Lexicon of New Formal Geologic Names 

of the United States 1981-1985 

U. S. G E 0 L 0 G I C A L S U R V E Y B U L L E T I N 1 5 6 5 
.I 

I 
Lexicon of New Formal Geologic Names 

of the United States 1981-1985 

By GWENDOLYN W. LUTTRELL, MARILYN L. HUBERT, and 

CYNTHIA R. MURDOCK 

U. S. G E 0 L 0 G I C A L S U R V E Y B U L L E T I N 1 5 6 5 

A compilation of the new formal geologic names 

introduced into the literature from 1981 to 1985 in 

the United States and Puerto Rico 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1991 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, Jr., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government 

Library of Congress Cataloging in Publication Data 

Luttrell, Gwendolyn Lewise Werth, 1927-

Lexicon of new formal geologic names of the United States 1981-1985/ by 

Gwendolyn W. Luttrell, Marilyn L. Hubert, and Cynthia R. Murdock. 

p. em. - (U.S. Geological Survey bulletin ; 1565) 

"A compilation of the new formal geologic names introduced into the literature 

from 1981 to 1985 in the United States and Puerto Rico." 

Includes bibliographical references. 

Supt. of Docs. no.: I 19.3:1565 

1. Geology-United States-Nomenclature. 2. Geology-Puerto Rico-Nomenclature. I. Hubert, Marilyn L. II Murdock, Cynthia R. III. Title. 

IV. Series. 

QE77.L88 1991 

557.3'014-dc20 91-22753 

CIP 

For sale by the Books and Open-File Reports Section 

U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 
CONTENTS 

Page 

Abstract.............................................................................. 1 

Introduction......................................................................... 1 

Selection of Names for the Lexicon.......................................... 2 

Lexicon Explanation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Lexicon............................................................................... 6 

References Cited .................................................................. 364 

TABLE 

Page 

Major geochronologic and chronostratigraphic units in use by the 

U.S. Geological Survey, including age estimates of boundaries . . . . IV 

METRIC CONVERSION FACTORS 

For readers who wish to convert measurements from the inch-pound system of 

units to the metric system of units, the conversion factors are listed below: 

Multiply By To obtain 

Length 

inch (in.) 25.4 millimeter (mm) 

foot (ft) .3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

Area 

square mile (mi2

) 2.590 square kilometer (km2

) 

III 
IV CONTENTS 

MAJOR GEOCHRONOLOGIC AND CHRONOSTRATIGRAPHIC UNITS 

Subdivisions in use by the U.S. Geological Survey (map symbols) Age estimates of 

boundaries in lEon or Eonothem Era or Erathem Period or System Epoch or Series million vears1

• 2 

Quaternary (Q) Holocene 0.010 - Pleistocene 2 (1.7-2.2)-

Neogene Pliocene Cenozoic subperiod or 5 (4.9-5.3) -

(Cz) subsvstem (N) Miocene Tertiary (T) 24 (23-26) - Paleogene Olieocene 38 (34-38)-

subperiod or Eocene 55 (54-56)- subsystem (F\) Paleocene 63 (63-66)- Cretaceous Late Upper 1-% (95-97)-

(K) Early Lower 138 (135-141) -

Jurassic Late Upper 

Mesozoic Middle Middle 

(Mz) (J) Early Lower 205 (200-215)-

Triassic Late Upper 

("i) Middle Middle 

Early Lower -240 - Permian Late Upper 

Phanerozoic (P) Early Lower 290 (290-305)-

Carboniferous Pennsylvanian Late Upper 

Middle Middle Periods or (P) Early Lower Systems -330 -

(C) Mississippian Late Upper 

(M) Early Lower 360 (360-365)-

Devonian Late Upper 

Paleozoic (0) Middle Middle 

(A.) Early Lower 410 (405-415)-

Silurian Late Upper 

(S) Middle Middle 

Earlv Lower 435 (435-440)-

Ordovician Late Upper 

(0) Middle Middle 

Early Lower 500 (495-510)-

Cambrian Late Upper 

(£) Middle Middle 

EarlY Lower -5703 

- Late Proterozoic4 

(Z) 900 - Proterozoic Middle Proterozoic4 

<e> (Y) 1600 - Early Proterozoic4 

(X) 2500 - Late Archean4 

(W) 3000 - Archea Middle Archean4 

(A) (V) 3400 - Early Archean4 

(U) 

r----pr~.:Ard;'"e~s---- ..._ _______ (3BOO?y------

(pA) 4550 

1 Ranges reflect uncertainties of isotopic and biostratigraphic age assignments. Age of boundaries not closely 

bracketed by existing data shown by -. Decay constants and isotopic ratios employed are cited in Steiger and Jager 

(1977). 2 Age estimates for the Phanerozoic are by G.A. Izett, M.A. Lanphere, M.E. MacLachlan, C.W. Naeser, J.D. 

Obradovich, Z.E. Peterman, M. Rubin, T.W. Stern, and R.E. Zartman at the request of the Geologic Names 

Committee. Age estimates for the Precambrain are by International Union of Geological Sciences Working Group on the 

Precambrian for the United States and Mexico, J.E. Harrison, Chairman. The chart is intended for use by members of 

the U.S. Geological Survey and does not constitute a formal proposal for a geologic time scale. Estimates of ages of 

boundaries were made after reviewing published time scales and other data. Future modification of this chart will 

undoubtedly be required. The general references apply where references are not given for specific boundaries. 3 Rocks older than 570 Ma also called Precambrian (p£), a time term that has no specific rank. 4 Geochronometric units. 5 Informal time term that has no specific rank. 
LEXICON OF NEW FORMAL GEOLOGIC NAMES 

OF THE UNITED STATES 1981-1985 

By GwENDOLYN W. LuTTRELL, MARILYN L. HuBERT, 

and CYNTHIA R. MuRDOCK 

Abstract 

Brief descriptions of new formal geologic names in the United States and 

Puerto Rico introduced between 1981 and 1985 are compiled from the naming 

papers. Information given for each name includes geologic age, geographic 

location, geologic province, type locality, subunits, and a summary of the 

lithology, genesis, structure, adjoining units, correlations, and thickness. 

INTRODUCTION 

In 1902, the U.S. Geological Survey published Bulletin 191, North 

American Geologic Formation Names, by F.B. Weeks, for use in 

assigning names to the formations that were being delineated in the 

folios of the Geologic Atlas of the United States. Weeks (1902) stressed 

the importance of recording and publishing the usage of geologic 

nomenclature in order to preserve the stability of the nomenclature. 

Following the rules of nomenclature adopted for U.S. Geological Survey 

publications, he specifically recommended that a formation at the 

particular locality from which it takes its name should be defined in such 

a manner that it can be differentiated from other strata with which it 

occurs; that, in determining the names to be applied to formations, the 

laws of priority and general usage should be observed; and that there 

should be no duplication of names, so that" ... in time all the present 

discrepancies in the nomenclature of formations would disappear from 

geologic literature." The present volume is the ninth in the series of 

lexicons published by the U.S. Geological Survey as a means of 

Manuscript approved for publication October 22, 1990. 

1 
2 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

preserving the stability of the nomenclature and recording the usage of 

geologic names of the United States. The lexicon series, listed chronologically, is as follows: 

Weeks, F.B., 1902, North American geologic formation names: Bibliography, 

synonymy, and distribution: U.S. Geological Survey Bulletin 191, 433 p. 

Wilmarth, M.G., 1938, Lexicon of geologic names of the United States (including Alaska): U.S. Geological Survey Bulletin 896, pt. 1, A-L, p. 1-1244; 

pt. 2, M-Z, p. 1245-2396. 

Wilson, Druid, Sando, W.J., and Kopf, R.W., 1957, Geologic names of North 

America introduced in 1936-1955: U.S. Geological Survey Bulletin 

1056-A, p. 1-405. 

Wilson, Druid, Keroher, G.C., and Hansen, B.E., 1959, Index to the geologic 

names of North America: U.S. Geological Survey Bulletin 1056-B, 

p. 407-622. 

Keroher, G.C., and others, 1966, Lexicon of geologic names of the United States 

for 1936-1960: U.S. Geological Survey Bulletin 1200, pt. 1, A-F, 

p. 1-1448; pt. 2, G-0, p. 1449-2886; pt. 3, P-Z, p. 2887-4341. 

Keroher, G.C., 1970, Lexicon of geologic names of the United States for 

1961-1967: U.S. Geological Survey Bulletin 1350, 848 p. 

Luttrell, G.W., Hubert, M.L., Wright, W.B., Jussen, V.M., and Swanson, 

R.W., 1981, Lexicon of geologic names of the United States for 

1968-1975: U.S. Geological Survey Bulletin 1520, 342 p. 

Swanson, R.W., Hubert, M.L., Luttrell, G.W., and Jussen, V.M., 1981, 

Geologic names of the United States through 1975: U.S. Geological 

Survey Bulletin 1535, 643 p. 

Luttrell, G.W., Hubert, M.L., and Jussen, V.M., 1986, Lexicon of new formal 

geologic names of the United States 1976-1980: U.S. Geological Survey 

Bulletin 1564, 191 p. 

SELECTION OF NAMES FOR THE LEXICON 

In 1933 the Committee on Stratigraphic Nomenclature, having 

representatives from the Association of American State Geologists, 

U.S. Geological Survey, American Association of Petroleum Geologists, 

and Geological Society of America, recognized the need for uniform 

procedures for classifying and naming stratigraphic and related units in 

the United States and formulated a code of Classification and Nomenclature of Rock Units. An outgrowth of this group, the Commission on 

Stratigraphic Nomenclature, now called the North American Commission on Stratigraphic Nomenclature, was founded in 1946. The Commission recognizes the desirability of uniform usage of stratigraphic nomenclature throughout North America and issued major revisions of the 

Code in 1961, 1970, and 1983. Geologic names in this lexicon have been 

selected following the rules for establishment of a formal geologic name 

in the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 1983) or, for those names published before 1983, the Code of Stratigraphic Nomenclature (American 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 3 

Commission on Stratigraphic Nomenclature, 1970). Both Codes state 

that proper establishment of a formal geologic name requires publication, in a recognized scientific medium, of a comprehensive statement 

that includes intent to designate a formal unit; designation of rank; 

selection and derivation of name; specification of stratotype (where 

applicable); description of unit; definition of boundaries; historical 

background; dimensions, shape, and other regional aspects; geologic 

age; correlations; and genesis (where applicable). Abstracts, theses, 

microfilms, open-file releases, and guidebooks that have distribution 

limited to participants of a field excursion do not constitute publication 

within the meaning established by the Code. We have attempted to 

include in this lexicon only names that meet these criteria, although a 

few exceptions have been made in dubious cases where formal proposals 

seem to have been intended or where informal names have become 

established in the literature through continued use. These exceptions 

are noted in the text. 

LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 5 

LEXICON EXPLANATION 

The following information is given for each name: 

• Unit name and affiliated units of higher rank. Bold print indicates 

usage accepted by the U.S. Geological Survey (USGS). 

• Geologic age assigned in naming paper. 

• State(s) in which the unit is described. State having the type 

locality is listed first. 

• Geologic province of type area as established by the American 

Association of Petroleum Geologists Committee on Statistics of 

Drilling (Meyer, 1970). 

• Reference to naming paper. 

• Type or reference section, locality, or area and derivation of name 

if not implicit in the type description. 

• Formally named subunits in ascending order. 

• Summary of the naming paper including definition and historical 

background; geographic distribution; formal and informal subdivisions listed in ascending order; description of the unit including 

lithology, color, distinctive textures, and other features; genesis; 

structure; boundaries, adjoining units, and correlations; thickness; 

and basis for age determination. In summary description, the 

designation "(new name)" indicates that the name is described 

herein. 

• Reference to revision paper (where applicable). 

• Summary of the revision paper. 

Units of measurements are those used in the naming papers; therefore, use of the inch-pound and metric systems of units differs from 

summary to summary. 
6 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Able Member of the Lehigh Acres Formation of the Glades 

Group 

Early Cretaceous (Comanchean) 

Florida 

South Florida province 

Applegate, A.V., Winston, G.O., and Palacas, J.G., 1981, Subdivision and regional 

stratigraphy of the Pre-Punta Gorda rocks (Lowermost Cretaceous-Jurassic(?)) in 

south Florida: Gulf Coast Association of Geological Societies Transactions, v. 31, 

(supplement), October, p. 447-453. 

Type section: Humble Number 1 Lehigh Acres well P-407, depth 

interval12,250-12,460 ft, sec. 14, T. 45 S., R. 27 E., Lee County, Fla. 

Named for the nearby Able Canal. 

The Able Member, here named, is the upper member of the Lehigh 

Acres Formation (new name) of the Glades Group in the subsurface of 

the South Florida basin, where it is the uppermost of four regionally 

persistent anhydrite units that have been identified below the Punta 

Gorda Anhydrite of the Glades Group. Consists of white to gray 

anhydrite interbedded with brown micritic, pure limestone, and gray 

argillaceous limestone containing occasional dolomite beds. Overlies the 

Twelve Mile Member (new name) of the Lehigh Acres; underlies the 

Punta Gorda Anhydrite. Thickness is 210 ft in the type well. Age is 

Early Cretaceous (earliest Comanchean). 

Accomack Member of the Omar Formation 

Pleistocene 

Virginia, Maryland 

Atlantic Coast basin 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of uppermost Cenozoic 

deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological 

Survey Professional Paper 1067-G, 53 p. 

Type section: Facies A-E, borehole H-20, northwest of Wattsville, 

northern Accomack County, Va. Reference sections: facies E and F, 

sand pits near Wattsville, Persimmon Point, and Accomack, Accomack 

County, Va. 

The informal Accomack beds of Mixon and others (1982), which 

underlie the upland in the area north and west of the Ames Ridge 

shoreline in Accomack County, Va., and are well developed from 

Wallops Station, Va., to Shell town, Md., are here named the Accomack 

Member of the Omar Formation. Consists of a dominantly transgressive 

sequence of sand, gravel, silt, clay, and peat divided into seven principal 

interfingering and overlapping sedimentary facies, A through G, representing marginal marine depositional environments. Unconformably 

overlies the Tunnels Mill Member (new name) of the Yorktown 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 7 

Formation; disconformably underlies the Occohannock Member (new 

name) of the Nassawadox Formation (new name); or is truncated by and 

disconformably underlies the Joynes Neck Sand (new name) or the Kent 

Island Formation. Thickness ranges from 58 ft at the type section to 80 

ft. Age is middle or late Pleistocene based on paleomagnetic data, 

uranium-thorium ages, and fossils. 

Accotink Schist of the Annandale Group 

Late Proterozoic or Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., and Lyttle, P.T., 1981, The Accotink Schist, Lake Barcroft Metasandstone, and Popes Head Formation-Keys to an understanding of the tectonic evolution 

of the northern Virginia Piedmont: U.S. Geological Survey Professional Paper 1205, 

16 p. 

Type locality: Outcrops along Accotink Creek west of the Capital 

Beltway, Interstate Highway 1-495, just north of the Little River 

Turnpike exchange, Annandale quadrangle, Fairfax County, Va. 

The Accotink Schist, here named, is the lower unit of the informal 

Eastern Fairfax sequence, defined as the structurally lowest metamorphic rocks in northern Virginia. Consists of beds of deformed pelitic 

quartz-muscovite-biotite-chlorite-plagioclase schist containing thin 

basal intervals of fine-grained metasiltstone, interbeds of metasandstone, and turbidite sequences. Gradationally underlies the Lake Barcroft Metasandstone (new name), the upper unit of the Eastern Fairfax 

sequence. Exotic blocks of Accotink Schist are contained in the Sykesville Formation, which is believed to have been emplaced by subaqueous 

sliding on top of the Lake Barcroft. Intruded by Early Cambrian 

Occoquan Granite. Thickness is unknown because the base is not 

exposed. 

Drake, A.A., Jr., 1985, Tectonic implications of the Indian Run Formation-A newly 

recognized sedimentary melange in the northern Virginia Piedmont: U.S. Geological 

Survey Professional Paper 1324, 12 p. 

The Accotink Schist is the lower unit of the Annandale Group (new 

name), formerly the informal Eastern Fairfax sequence of Drake and 

Lyttle (1981). The Accotink and the upper unit of the Annandale Group, 

the Lake Barcroft Metasandstone (new name), lie between two 

melanges, the newly recognized underlying Indian Run Formation (new 

name) and the overlying Sykesville Formation. Fragments of Accotink 

and Lake Barcroft are restricted to an area of melange originally 

defined as Sykesville, but now considered to be a separate unit, the 

Indian Run. Age is Late Proterozoic or Cambrian. 
8 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Alamos Canyon Siltstone Member of the Peace Valley 

Formation of the Ridge Basin Group 

Miocene 

California 

los Angeles basin 

Link, M. H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J.C., and Link, M.H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5-12. 

Type section: Along the western side of Pyramid Lake from north of the 

tuff horizon to the Piru Creek arm of Pyramid Lake and across the lake 

and along the west side of Canada de los Alamos, Los Angeles County, 

Calif. 

The Alamos Canyon Siltstone Member, here named, is the uppermost member of the redefined Peace Valley Formation of the Ridge 

Basin Group in the central Ridge basin, Los Angeles County, Calif., 

where the Peace Valley is separated into five members by clastic 

tongues of the Ridge Route Formation of the Ridge Basin Group. 

Consists of gray-green shale, mudstone, and siltstone containing a few 

brown sandstone layers and vertebrate fossils. Extends laterally for 

6,100 m; interfingers laterally with the Violin Breccia to the southwest 

and the Apple Canyon Sandstone Member (new name) of the Ridge 

Route Formation to the northeast. Conformably overlies the Posey 

Canyon Shale Member (new name) of the Peace Valley, from which it is 

separated by a distinctive tuff horizon; conformably underlies the Apple 

Canyon Sandstone Member. Thickness is 1,500 mat the type section. 

Age is late Miocene based on vertebrate (Kinsey Ranch fauna) and plant 

fossils from underlying units. 

Albion Creek Chert Member of the Tenmile Creek Formation 

of the Stanley Group 

late Mississippian 

Oklahoma 

Ouachita tectonic belt province 

Pitt, W.D., Fay, R.O., Wilson, L.R., and Curiale, J.A., 1982, Geology of Pushmataha 

County, Oklahoma: Eastern New Mexico University Studies in Natural Sciences 

Special Publication 2, 101 p. 

Type area: Along the upper branches of Albion Creek, north of Albion, 

southeastern Potato Hills, Pushmataha County, Okla. 

The Albion Creek Chert Member, here named, is in the lower part 

of the Tenmile Creek Formation of the Stanley Group in the Ouachita 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 9 

Mountains in Pushmataha County, southeastern Oklahoma. Replaces 

the preempted name Albion Shale or Formation of former usage. 

Consists of alternating beds of gray sandstone and gray siliceous shale 

and chert. In the Stanley Group type section, T. 2 N., R. 20 E., it lies 

about 1, 700 ft above the Friendship Chert Member (new name) of the 

Tenmile Creek and about 2,000 ft above the Arkansas Novaculite. 

Thickness ranges from 45 to 185 ft. Age is Late Mississippian. 

Alexandria Bay Gneiss of the Piseco Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type area: Exposures within 1 km of Alexandria Bay, St. Lawrence 

River, Jefferson County, N.Y. 

The Alexandria Bay Gneiss, here named, is in the Piseco Group (new 

name) in the Adirondack Mountains in New York. Consists of finegrained pink and gray leucogranitic gneiss. Overlies the Pharaoh 

Mountain Gneiss (new name) of the Piseco in the Northwest Lowlands; 

unconformably underlies the Baldface Hill Gneiss (new name) of the 

Oswegatchie Group. Equivalent to the Brant Lake Gneiss in the central 

and eastern Adirondacks. Thickness is 1,200 m. Age is Proterozoic. 

Alkali Canyon Formation of the Dalles Group 

Miocene and Pliocene(?) 

Oregon 

Eastern Columbia basin 

Farooqui, S.M., Beaulieu, J.D., Bunker, R.C., Stensland, D.E., and Thoms, R.E., 1981, 

Dalles Group: Neogene formations overlying the Columbia River Basalt Group in 

north-central Oregon: Oregon Geology, v. 43, no. 10, p. 131-140. 

Reference section: Chem-Security Systems access road, SE1/4 sec. 25, 

T. 2 N., R. 20 E., Gilliam County, Oreg. Named for Alkali Canyon, 

16 km southwest of Arlington, T. 2 N., R. 20-21 E. 

Vitric tuff, silty clay, silt, and basalt gravel alluvial fan and braided 

stream deposits in the Arlington basin are here named the Alkali 

Canyon Formation of the Dalles Group. Conformably and unconformably overlies units of the Columbia River Group and the Ellensburg 

Formation; underlies Quaternary loess. Age is late Miocene and early 

Pliocene(?) based on vertebrate fossils. 
10 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Aliens Grove Member of the Walworth Formation 

Pleistocene (Wisconsinan) 

Wisconsin, Jllinois 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Base of west wall of borrow pit, 0.8 km east of Aliens 

Grove, 4 km west of Capron Ridge and north of old Highway 15, 

NWV4SEV4SWV4 sec. 32, T. 2 N., R. 15 E., Sharon and Clinton 

7.5-minute quadrangles, Walworth County, Wis. 

The Aliens Grove Member of the Walworth Formation (new name), 

here named following the informal usage of Fricke (1976), is in southcentral Wisconsin and northern Illinois. Consists of light-brown to 

yellowish-brown sandy, pebbly till and associated deposits. Sharply 

overlies the Foxhollow Member (new name) and sharply to gradationally underlies the Clinton Member (new name), both of the Walworth 

Formation. Equivalent to the Argyle Till Member of the Winnebago 

Formation in Illinois. Thickness attains 3. 9 m. Age is late Pleistocene 

(early Wisconsinan or older). 

Amboy Drift 

Pleistocene (Wisconsinan) 

Washington 

Western Columbia basin 

Mundorff, M.J., 1984, Glaciation in the lower Lewis River basin, southwestern Cascade 

Range, Washington: Northwest Science, v. 58, no. 4, p. 269-281. 

Type area: Exposures in the vicinity of the town of Amboy, Clark 

County, Wash. 

Glacial drift, including till, lacustrine and fluvial outwash deposits, 

ice-contact deposits, and boulder deposits in the Lewis River valley, 

East Fork Lewis River valley and on interfluves between the two 

rivers, in Clark County, Wash., are here named the Amboy Drift. Blue 

or gray till, weathering brown, forms a discontinuous blanket as much 

as 30 m thick over most of the area. Overlies the Troutdale Formation. 

Correlates with the Hayden Creek Drift. Age is late Pleistocene (early 

Wisconsinan) based on the 14carbon date of wood of greater than 60 ka. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 11 

Andy Mountain Formation of the Sandy Springs Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Abrams, C.E., and McConnell, K.I., 1981, Stratigraphy of the area around the AustellFrolona antiform; west-central Georgia, in Wigley, P.B., ed., Latest thinking on the 

stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 55--67. 

Type locality: Andy Mountain, 1.5 mi west of Winston, Winston 

7.5-minute quadrangle, Douglas County, Ga. 

The Andy Mountain Formation of the informal Roosterville group, 

here named, is in the Austell-Frolona antiform, west-central Georgia. 

Consists of garnet-muscovite-quartz schist and quartzite containing 

local horizons of gneiss. Stratigraphically overlies but structurally 

underlies the New Georgia Group (new name); stratigraphically underlies the Bill Arp Formation (new name), but folding has placed it 

structurally over the Bill Arp and the intrusive Austell Gneiss. Age is 

Proterozoic. 

McConnell, K. I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

The Andy Mountain Formation is here assigned to the Sandy 

Springs Group (western belt). Conformably overlies the Dog River 

Formation (new name); stratigraphically underlies the Bill Arp Formation (new name), both of the Sandy Springs Group. Age is Late 

Proterozoic and (or) early Paleozoic. 

Annandale Group 

Late Proterozoic or Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., 1985, Tectonic implications of the Indian Run Formation-A newly 

recognized sedimentary melange in the northern Virginia Piedmont: U.S. Geological 

Survey Professional Paper 1324, 12 p. 

Type locality: Exposures along Accotink Creek, Holmes Run, and 

Tripps Run, Annandale 7.5-minute quadrangle, Fairfax County, Va. 

Named for the city of Annandale, Fairfax County. 

Subunits: Accotink Schist, Lake Barcroft Metasandstone. 

The Annandale Group, an allochthon in Fairfax County, Va., was 

originally termed the Eastern Fairfax sequence by Drake and Lyttle 

(1981). Contains the lower Accotink Schist (new name) and the overlying Lake Barcroft Metasandstone (new name). Thought to be a 

coarsening-upward sequence of an outer submarine fan association. 

Overlies the Indian Run Formation (new name), with which it forms a 
12 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

melange-allochthon motif, on the Red Fox thrust fault; underlies the 

Sykesville Formation melange on the Burke thrust fault. Intruded by 

the Cambrian Occoquan Granite. Age is probably Late Proterozoic 

although it must be considered Late Proterozoic or Cambrian. 

Antelope Range Formation 

Early Mississippian (Osagean or later) 

Nevada 

Great Basin province 

Hose, R.K., Armstrong, A.K., Harris, A.G., and Mamet, B.L., 1982, Devonian and 

Mississippian rocks of the northern Antelope Range, Eureka County, Nevada: U.S. 

Geological Survey Professional Paper 1182, 19 p. 

Type section: Outcrops in sec. 22, T. 16 N., R. 51 E., northern Antelope 

Range, Eureka County, Nev. 

The Antelope Range Formation, here named, is in the northern 

Antelope Range, Nev., and is also recognized in the southern Fish 

Creek Range, 10 km to the east, where there is a similar sandstoneshale sequence overlying a profound basal unconformity. Deposition 

was in a deltaic or estuarine environment. Consists of a 30-m-thick basal 

sequence of dark-yellowish-orange- to light-brown-weathering fine- to 

coarse-grained sandstone containing quartz, feldspar, and chert, overlain by olive-gray silty shale or thin-bedded, platy siltstone. Sharply and 

unconformably overlies the Kinkead Spring Limestone (new name) or 

the Davis Spring Formation (new name) in the Antelope Range and the 

Devils Gate Limestone in the Fish Creek Range. Upper part is faulted 

or removed by erosion. Thickness is unknown. Age is Early Mississippian (Osagean or later) based on its stratigraphic position above the 

Osagean Kinkead Spring Limestone. 

Apple Canyon Sandstone Member of the Ridge Route 

Formation of the Ridge Basin Group 

Miocene (Hemphillian) 

California 

Los Angeles basin 

Link, M.H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J.C., and Link, M.H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5--12. 

Type section: Exposure on the northeast side of Interstate Highway 

I-5, beginning at its intersection with Hungry Valley Road, about 8 km 

south of Gorman, Los Angeles County, Calif. 

The Apple Canyon Sandstone Member, here named, is in the Ridge 

Route Formation of the Ridge Basin Group in the central Ridge basin, 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 13 

Los Angeles County, Calif. Is the uppermost of five major clastic 

tongues in the Ridge Route and consists of light-brown mediumgrained, arkosic sandstone interbedded with mudstone and conglomerate and minor amounts of limestone; contains freshwater mollusk, 

ostracode, stromatolite, plant, and vertebrate fossils. Lateral extent is 

8,000 m; interfingers with the Ridge Route (undivided) and the Posey 

Canyon Shale Member (new name) and the Alamos Canyon Siltstone 

Member (new name), both of the redefined Peace Valley Formation, to 

the northeast, and the Violin Breccia to the southwest. Conformably 

overlies the Alamos Canyon; conformably underlies the Hungry Valley 

Formation of the Ridge Basin Group. Thickness is 1,000 mat the type 

section and attains 1, 130 m. Age is late Miocene (Hemphillian) based on 

vertebrate fossils (Kinsey Ranch fauna). 

Arapahoe Sand Member of the Flanner Beach Formation 

Pleistocene 

North Carolina 

Atlantic Coast basin 

Miller, William, III, 1985, The Flanner Beach Formation (middle Pleistocene) in eastern 

North Carolina: Tulane Studies in Geology and Paleontology, v. 18, no. 3, p. 93-122. 

Type locality: Outcrops in bluffs of the Neuse River near Smith Gut, 

west of the mouth of Beard Creek, and near Pine Cliff Recreation Area, 

Cherry Point 7.5-minute quadrangle, Pamlico County, N.C. Probably 

named for the nearby town of Arapahoe. 

Barrier sand deposits exposed near Smith Gut and at the Pine Cliff 

Recreation area in the Neuse River valley, Pamlico County, N.C., are 

here named the Arapahoe Sand Member of the Flanner Beach Formation, following the informal usage of Mixon and Pilkey (1976). Consists 

of crossbedded, fine to coarse sand, sandy mud, and pebbly sand 

containing clay laminations and cylindrical burrows. Gradationally 

overlies the Smith Gut Member (new name) of the Flanner Beach; 

intertongues to the east with the Beard Creek Member (new name) of 

the Flanner Beach; is truncated to the east by the Suffolk (Grantsboro) 

Scarp. Thickness attains 7.5 m. Age is middle Pleistocene. 

Archer Mountain Suite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Sinha, A.K., and Bartholomew, M.J., 1984, Evolution of the Grenville terrane in the 

central Virginia Appalachians: Geological Society of America Special Paper 194, 

p. 175-186. 
14 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type locality: Along U.S. Highway 29, 100m south from its junction 

with Virginia Highway 6 North where it crosses Rockfish River at 

Woods Mill, Lovingston 7.5-minute quadrangle, lat 37°51' N., long 

78°49'30" W., Nelson County, Va. Derivation of name not stated. 

The Archer Mountain Suite, informally called the Archer Mountain 

pluton by Bartholomew and others (1981), here named, is in the 

Lovingston massif of the central Virginia Blue Ridge. Consists of 

biotite-quartz monzonite intruded by small massive charnockite plutons 

and coarse pegmatites. Age is Middle Proterozoic based on a uraniumlead age of 1, 060 Ma. 

Argo-Fay Bed of the Scales Formation of the Maquoketa 

Group 

Late Ordovician 

Illinois 

Wisconsin arch 

Kolata, D.R., and Graese, A.M., 1983, Lithostratigraphy and depositional environments 

of the Maquoketa Group (Ordovician) in northern Illinois: Illinois Geological Survey 

Circular 528, 49 p. 

Type section: Mt. Carroll Southwest Section: Quarry on the north side 

of U.S. Highway 52, 2.5 mi southwest of Mt. Carroll and 5 mi north of 

Argo-Fay, SW1/4NE1/4SW1/4 sec. 10, T. 24 N., R. 4 E., Savanna 

15-minute quadrangle, Carroll County, Ill. 

The Argo-Fay Bed, here named, is in the lower part of the Scales 

Formation of the Maquoketa Group in Carroll County, northwestern 

Illinois. Consists of hard, brownish-black to black carbonaceous, fissile 

clay shale. Fragments of graptolites and chitinozoans stand out on 

weathered bedding planes. Lies 4 ft above the unconformable contact of 

the Scales with the Dubuque Formation. Equivalent to beds in the 

brown shaly unit of Brown (1974) in Clayton County, Iowa, and in Grant 

County, Wis. Thickness is 1 ft. Age is Late Ordovician. 

Armstrong Hill Member of the Slade Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R., 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Roadcut on Kentucky Highway 2 north of Armstrong Hill, 

just north of its intersection with Interstate Highway 1-64, Olive Hill 

7.5-minute quadrangle, Carter County, Ky. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 15 

The Armstrong Hill Member, used informally by Ettensohn (1977) 

and here named and assigned to the Slade Formation (new name), was 

previously assigned to the Newman Limestone, here restricted from 

the Cumberland Escarpment area of east-central and northeastern 

Kentucky. Consists predominantly of calcilutite containing thin shale 

partings. Conformably overlies the Cave Branch Bed of the Slade; 

disconformably underlies the Holly Fork Member (new name) or 

Tygarts Creek Member (new name), both of the Slade, although local 

intertonguing may occur with these units. Maximum thickness is 5 m. 

Age is Late Mississippian. 

Arnett Member of the Sleeping Buffalo Rhyolite 

Miocene 

Arizona 

Basin and Range province 

Creasey, S.C., Peterson, D.W., and Gambell, N.A., 1983, Geologic map of the Teapot 

Mountain quadrangle, Pinal County, Arizona: U.S. Geological Survey Geologic Quadrangle Map GQ-1559, scale 1:24,000. 

Type locality: Exposures in Arnett Creek, NW1/4 sec. 22, T. 2 S., R. 12 

E., Teapot Mountain 7.5-minute quadrangle, Pinal County, Ariz. 

The Arnett Member of the Sleeping Buffalo Rhyolite (new name), 

here named, is in the Teapot Mountain quadrangle, Pinal County, Ariz. 

Consists of light-gray to buff flow-banded, vitrophyric and glomeroporphyritic rhyolite, locally comprising alternating zones of agglomeritic, pumiceous, and dense aphanitic rhyolite. Contains phenocrysts of 

plagioclase and quartz in a glassy or devitrified groundmass. Conformably overlies older Tertiary tuff; unconformably underlies the Road 

Runner Rhyolite (new name). Age is Miocene based on potassium-argon 

ages of 18 to 15.9 Ma of rhyolite in the Mineral Mountain quadrangle to 

the west. 

Aspen Range Formation 

Mississippian (Osagean to Chesterian) 

Idaho 

Wasatch uplift 

Sando, W.J., Sandberg, C.A., and Gutschick, R.C., 1981, Stratigraphic and economic 

significance of Mississippian sequence at North Georgetown Canyon, Idaho: American 

Association of Petroleum Geologists Bulletin, v. 65, no. 8, p. 1433-1443. 

Type section: Outcrops at North Georgetown Canyon on a spur extending across the S1/2NE1/4 sec. 16, T. 10 S., R. 44 E., Harrington Peak 

7.5-minute quadrangle, Bear Lake County, Idaho. 

Rocks previously mapped as Brazer Limestone by Cressman (1964) 

and Deseret [Limestone] equivalent by Sando and Sandberg (1979) are 
16 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

here named the Aspen Range Formation and are recognized as part of 

a facies belt of Mississippian rocks in the Overthrust belt of Idaho. 

Exposed on the west side of Aspen Range at North Georgetown Canyon 

and on the east side at Wells Canyon. North Georgetown Canyon 

section contains a lower phosphatic member, 20 m thick, that has a basal 

phosphorite bed, 5 to 8 em thick; a thin-bedded limestone member, 91 m 

thick; a sandy crinoidal limestone member, 195 m thick; a birdseye 

limestone member, 132 m thick; a chertified siltstone member, 28 m 

thick; and a thick-bedded limestone member, 65 m thick. The phosphatic 

member is equivalent to phosphatic members in the Deep Creek, Little 

Flat, and Brazer Formations. Conformably overlies the Mission Canyon 

Limestone of the Madison Group; disconformably underlies the Wells 

Formation. Thickness is 531 m at the type section. Age is Mississippian 

(middle Osagean to middle Chesterian) based on foraminifers, conodonts, and corals. 

Atlanta Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type area: Area around Atlanta, Fulton County, Ga. 

Subunits: Inman Yard Formation, Wolf Creek Formation, Promised 

Land Formation and its Hannah Member, Norcross Gneiss, 

Clairmont Formation, Senoia Formation, Wahoo Creek Formation, 

Stonewall Formation, Clarkston Formation and its Fairburn and 

Tar Creek Members, Big Cotton Indian Formation, Intrenchment 

Creek Quartzite, Camp Creek Formation. 

The Atlanta Group, here named, is a eugeosynclinal sequence of 

flysch-like rocks that crop out in the 90-km-long by 40-km-wide 

Newnan-Tucker synform in northern Georgia. Subdivided into 12 

formations and 3 members (all new names), listed above in ascending 

order. Thickness ranges from 6,000 to 18,000 m. Contact with the 

discordantly overlying Lithonia Gneiss and Snellville Formation (new 

name) is a thrust fault or an unconformity. Younger than the Snellville 

Formation (1,100 Ma) and intruded by the Stone Mountain and Panola 

Granites (325 Ma). Age is Late Proterozoic and (or) early Paleozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 17 

Badger Gulch Formation 

Early Permian (Leonardian) 

Idaho 

Great Basin province 

Mytton, J.W., Morgan, W.A., and Wardlaw, B.R., 1983, Stratigraphic relations of 

Permian units, Cassia Mountains, Idaho, in Miller, D.M., Todd, V.R., and Howard, 

K.A., eds., Tectonic and stratigraphic studies in the eastern Great Basin: Geological 

Society of America Memoir 157, p. 281-303. 

Type section: Composite of, in the lower part, exposures on a ridge 

southwest of the confluence of A. H. Creek and Third Fork, Sl/2 sec. 17, 

T. 14 S., R. 19 E., Pike Mountain 7.5-minute quadrangle, Cassia 

County, Idaho, and, in the upper part, exposures on a northwest-facing 

ridge on the south side of Badger Gulch, NWl/4 sec. 20, T. 15 S., R. 20 

E., Mahogany Butte 7.5-minute quadrangle, Cassia County, Idaho. 

The Badger Gulch sequence of Morgan (1980) in the Cassia Mountains, southern Idaho, is here named the Badger Gulch Formation. 

Consists of brownish-gray to black, very fine grained, thin-bedded lime 

mudstone containing silt-sized skeletal fragments replaced by calcite, 

quartz silt, and argillaceous material. Outcrops form castellated cliffs 

that have jagged spires. Beds have sharp contacts and evenly spaced 

laminae and are marine basin deposits. May be part of the depositional 

sequence of the northern Oquirrh basin. Conformably and gradationally 

overlies the Third Fork Formation (new name); conformably and 

gradationally underlies the Trapper Creek Formation (new name). 

Thickness at the composite section is 313.7 m. Age is Early Permian 

(early Leonardian) based on conodonts in the Trapper Creek. The 

Wolfcampian-Leonardian boundary lies within the poorly fossiliferous 

Third Fork-Badger Gulch sequence and, for convenience, is drawn at 

the Third Fork-Badger Gulch contact. 

Baker Hill Formation of the Wilcox Group 

Paleocene 

Alabama, Georgia 

Mid-Gulf Coast basin 

Gibson, T.G., 1982, New stratigraphic unit in the Wilcox Group (upper Paleocene-lower 

Eocene) in Alabama and Georgia: U.S. Geological Survey Bulletin 1529-H, 

p. H23-H32. 

Type locality: Exposure on south wall of Lynn Griffin no. 1 mine, west 

side of County Highway 29, 5.2 mi southwest of Baker Hill, NEl/4 sec. 

4, T. 8 N., R. 27 E., Lawrenceville 7.5-minute quadrangle, Henry 

County, Ala. 

Rocks previously included in the time-equivalent Nanafalia Formation are here named the Baker Hill Formation of the Wilcox Group in 
18 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

southeastern Alabama and southwestern Georgia. Consists of kaolinitic 

and bauxitic massively bedded clay, carbonaceous clay, and crossbedded micaceous quartz sand deposited in a fluvial to estuarine environment. Overlies the Clayton or Porters Creek Formations of the Midway 

Group; unconformably underlies the Tuscahoma Formation of the 

Wilcox Group. Thickness is 55 ft at the type locality and ranges from 50 

to 150 ft. Age is late Paleocene based on dinoflagellates and its 

equivalency to the Nanafalia Formation. 

Bakerville Member of the Lincoln Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellhneous Paper 84-1, p. 1-15. 

Type section: Gravel pit, east side of Robin Road, 200 m south of its 

intersection with Highway B, 1. 7 km west of Bakerville, 

SEl/4NWlf4NWl/4 sec. 26, T. 25 N., R. 2 E., Marshfield 15-minute 

quadrangle, Wood County, Wis. Named for Bakerville. 

The lower member of the Lincoln Formation (new name) in the 

Chippewa sublobe in central Wisconsin is here named the Bakerville 

Member, following the informal usage of Mode (1976). Consists of 

reddish-brown cobbly, pebbly, sandy loam; in some places is texturally 

indistinguishable from the till of the adjacent Merrill Member (new 

name), which is given a different name because continuity between the 

units has not been established. Sharply overlies Precambrian or Cambrian bedrock or the Edgar Member (new name) of the Marathon 

Formation (new name); is the surface unit in the Marshfield moraine. 

Maximum thickness is 10 m. Age is Pleistocene (early Wisconsinan) 

based on the age of organic material overlying the Merrill Member. 

Baldface Hill Gneiss of the Oswegatchie Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: Exposures along the rocky face of Baldface Hill, 3 to 5 km 

north of Harrisville, Harrisville 7.5-minute quadrangle, Lewis County, 

N.Y. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 19 

The Baldface Hill Gneiss of the Oswegatchie Group, here named, is 

at Baldface Hill in the Northwest Lowlands of the Adirondack Mountains, N.Y. Consists of layered, rusty-brown-weathering biotitegarnet-sillimanite gneiss. Although outcrops are discontinuous, the unit 

may be continuous but not well exposed. Unconformably overlies the 

Alexandria Bay Gneiss (new name) of the Piseco Group (new name); 

underlies the Poplar Hill Gneiss (new name) and Gouverneur Marble of 

the Oswegatchie Group in the Northwest Lowlands. Correlates with 

the Eagle Lake Gneiss of the Lake George Group (both new names) in 

the eastern Adirondacks. Thickness ranges from 30 to 300m. Age is 

Proterozoic. 

Ball Mountain Formation of the lynchburg Group 

Late Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Wehr, Frederick, 1985, Stratigraphy of the Lynchburg Group and Swift Run Formation, 

Late Proterozoic (730-570 Ma), central Virginia: Southeastern Geology, v. 25, no. 4, 

p. 225-239. 

Type locality: Exposures on Ball Mountain south of the Rockfish River, 

Schuyler 7.5-minute quadrangle, Nelson County, Va. 

Subunit: Johnson Mill Member. 

The Ball Mountain Formation of the Lynchburg Group, here named, 

is in the Culpeper and Rockfish River areas in Virginia. Consists of 

coarse-grained to pebbly quartz wacke and quartzite interbedded with 

laminated siltstone and graphitic mudstone. The upper 100 m consists of 

graphitic schist named the Johnson Mill Member, the revised Johnson 

Mill Formation of Nelson (1962). Truncates underlying units and either 

unconformably overlies or is in fault contact with the Thorofare Mountain Formation (new name) of the Lynchburg. Is in fault(?) contact with 

the overlying Charlottesville Formation. Is equivalent to the upper part 

of the Rockfish Conglomerate. Age is Late Proterozoic based on an age 

of 730 to 570 Ma for the Lynchburg Group. 

Bandera Mesa Member of the Devil's Graveyard Formation of 

the Buck Hill Group 

Oligocene 

Texas 

Permian basin 

Stevens, J.B., Stevens, M.S., and Wilson, J.A., 1984, Devil's Graveyard Formation 

(new), Eocene and Oligocene age, Trans-Pecos Texas: Texas Memorial Museum 

Bulletin 32, p. 1-21. 
20 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type area: Area along the front of Bandera Mesa from Puerto Potrillo 

to Red Hill, and east across Green Valley to McKinney Mountain, 

Jordan Gap quadrangle, Presidio County, Tex. Boundary stratotypes 

are designated. 

The Bandera Mesa Member, here named, is in the upper part of the 

Devil's Graveyard Formation (new name) of the Buck Hill Group. 

Consists of pink, red, and brown fluvial and lacustrine tuffaceous 

mudstone, conglomerate, clay, and limestone, thin basalt flows, and 

sandstone- and conglomerate-filled channels informally named the 

Skyline and Cotter channels. Overlies the middle member of the Devil's 

Graveyard and is separated from it by the Skyline channels. The Cotter 

channels occur higher in the section. Underlies the Mitchell Mesa 

Rhyolite or the informal Yellow conglomerate. Thickness is about 1,000 

ft. Age is Oligocene based on vertebrate fauna. 

Banzet Formation of the Cherokee Group 

Middle Pennsylvanian (Desmoinesian) 

Kansas, Oklahoma 

Cherokee basin, Chautauqua platform 

Denesen, S.L., 1985, Depositional environments of the Banzet Formation (Middle 

Pennsylvanian) in southeastern Kansas and northeastern Oklahoma: Shale Shaker, 

v. 36, no. 2, p. 164-169. 

Type area: 11,000 mi2 between T. 26 S. in Kansas and T. 22 N. in 

Oklahoma and between R. 2 E. and R. 23 E. Derivation of name not 

stated. 

Subunits: Bevier Member and Bevier coal bed; Lagonda Member and 

Iron Post coal bed; Mulky Member and Kinnison Shale Bed, Breezy Hill 

Limestone Bed, and Mulky coal bed. 

The interval of shales, siltstones, thin limestones, thin coals, and 

lenticular, discontinuous sandstones found in repetitive sequences 

between the top of the Ardmore Limestone and the base of the Excello 

Shale in southeastern Kansas and northeastern 0 klahoma is here named 

the Banzet Formation of the Cherokee Group. Includes the Bevier, 

Lagonda, and Mulky Members, here reduced from formation rank, and 

the Bevier coal bed in the Bevier Member, the Iron Post coal bed in the 

Lagonda Member, and the Kinnison Shale Bed, Breezy Hill Limestone 

Bed, and Mulky coal bed in the Mulky Member. The Kinnison and 

Breezy Hill are reduced from members of the Mulky Formation. Age is 

Middle Pennsylvanian (Desmoinesian). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 21 

Barlow Gneiss Member of the Pumpkinvine Creek Formation 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

German, J. M., 1985, The geology of the northeastern portion of the Dahlonega gold belt: 

Georgia Geologic Survey Bulletin 100, p. 1-41. 

Type locality: Exposures in a large hydraulic cut near the inactive 

Barlow gold mine near Dahlonega, Dawsonville and Campbell Mountain 

7.5-minute quadrangles, Lumpkin County, north-central Georgia. 

The Barlow Gneiss Member of the Pumpkinvine Creek Formation, 

here named, is in the Dahlonega, Ga., area. Consists of gray, pinstriped-appearing muscovite-biotite-plagioclase-quartz gneiss locally 

interlayered with amphibolites. Lithologically similar to and may be 

correlative with the Gaits Ferry Gneiss Member (new name) of 

McConnell and Abrams (1984) of the Pumpkinvine Creek. Is a wellexposed marker horizon and is sharply bounded by undifferentiated 

amphibolite of the Pumpkinvine Creek. Age is Late Proterozoic and (or) 

early Paleozoic. 

Bat Mountain Formation 

Miocene 

California 

Great Basin province 

Cemen, Ibrahim, Drake, Robert, and Wright, L.A., 1982, Stratigraphy and chronology of 

the Tertiary sedimentary and volcanic units at the southeastern end of the Funeral 

Mountains, Death Valley region, California, in Cooper, J.D., Troxel, B.W., and 

Wright, L.A., eds., Geology of selected areas in the San Bernardino Mountains, 

western Mohave Desert, and southern Great Basin, California: Geological Society of 

America, Cordilleran Section, 78th Annual Meeting, volume and guidebook no. 9, 

p. 77-88. 

Type locality: Exposures along the crest and southeastern flank of Bat 

Mountain, southeastern Funeral Mountains, Ash Meadows 15-minute 

quadrangle, Inyo County, Calif. 

The Bat Mountain Formation, here named, is in the southeastern 

end of the Funeral Mountains in the Death Valley region of Inyo 

County, Calif. Denny and Drewes (1965) divided the formation into an 

informal lower unit, which they called the upper fanglomerate, and an 

informal upper unit, which they called the upper conglomerate. Their 

upper fanglomerate is here referred to as the conglomerate member and 

their upper conglomerate as the sandstone member. The conglomerate 

member consists of poorly sorted, angular clasts of Proterozoic and 

Paleozoic carbonate and siliceous rocks in a sand to clay matrix, which 

is gray in the lower part and red in the upper part of the member. The 

sandstone member consists of reddish-brown to brown fining-upward 
22 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

cycles, conglomeratic at the base and silty at the top, and represents 

stream deposits marginal to the alluvial fan deposits of the conglomerate member. The sandstone member grades laterally and vertically 

down into the conglomerate member. The Bat Mountain unconformably 

overlies algal limestone and is exposed at the surface. Thickness of the 

conglomerate member ranges from 200 to 1,000 ft. Age is middle(?) 

Miocene based on the ages of tuffs in the Artist Drive Formation. 

Bay View Coral Bed of the Windom Shale Member of the 

Moscow Formation of the Hamilton Group 

Middle o'evonian 

New York 

Appalachian basin 

Baird, G. C., and Brett, C.E., 1983, Regional variation and paleontology of two coral beds 

in the Middle Devonian Hamilton Group of western New York: Journal of Paleontology, v. 57, no. 3, p. 417-446. 

Type section: Abandoned Penn-Dixie Cement Company quarry, 0.2 mi 

northeast of the junction of Big Tree and Bay View Roads, near Bay 

View, Buffalo SE 7.5-minute quadrangle, Erie County, N.Y. 

The coral-rich bed in the lower middle part of the Windom Shale 

Member of the Moscow Formation of the Hamilton Group is here named 

the Bay View Coral Bed. This important marker bed extends for 150 km 

from Lake Erie east to Onondaga County, N.Y. The western facies, 15 

to 30 em thick, consists of coral and other fossils in soft, blocky, gray 

mudstone. The eastern facies, 1 to 2 m thick, is gray, fissile to blocky, 

calcareous mudstone containing shell beds and nonseptarian concretions. Overlies the Ambocoelia umbonata zone of Brett (1974); underlies the coral-trilobite bed of Brett (1974), here named the Smoke Creek 

Bed (new name) of the Windom. Age is Middle Devonian. 

Beard Creek Member of the Flanner Beach Formation 

Pleistocene 

North Carolina 

Atlantic Coast basin 

Miller, William, III, 1985, The Flanner Beach Formation (middle Pleistocene) in eastern 

North Carolina: Tulane Studies in Geology and Paleontology, v. 18, no. 3, p. 93-122. 

Type locality: Bluffs on the north shore of the Neuse River, 0.6 km 

northwest of Beard Creek and 0.3 km upstream from Whisk Point, 

Upper Broad Creek 7.5-minute quadrangle, Pamlico County, N.C. 

Estuarine and lagoonal back barrier deposits in the Neuse River area 

of the North Carolina Coastal Plain are here named the Beard Creek 

Member of the Flanner Beach Formation, following the informal usage 

of Mixon and Pilkey (1976). Consists of fine- to medium-grained sand 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 23 

and muddy sand containing mollusks and minor amounts of silt and clay 

interbeds. Gradationally and conformably overlies the Smith Gut Member (new name) of the Flanner Beach; intertongues to the east with the 

Arapahoe Sand Member (new name) and to the northwest with the 

Newport Sand Member (new name), both of the Flanner Beach. 

Thickness is 4 mat the type locality. Age is middle Pleistocene. 

Bear Pond Gneiss 

Precambrian 

New York 

Adirondack uplift 

Potter, D. B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: Exposures on the northwest shore of Bear Pond and 

along Route 10 to the west over a distance of 0.4 km, Tupper Lake 

15-minute quadrangle, Hamilton County, N.Y. 

Subunit: High Pond Member. 

The Bear Pond Gneiss, here named, is in the Loon Pond syncline in 

the Bog River synclinorium of the Adirondack Highlands, Hamilton and 

St. Lawrence Counties, N.Y., where it occurs as a layer of varying 

thickness that rings the central portion of the syncline and produces 

topographic features such as high ridges, lakes, ponds, and swamps. 

Includes the High Pond Member (new name), a quartz-rich granulite, 

with which it is transitional. Consists of several different quartzmicrocline gneisses containing magnetite as well as plagioclase, biotite, 

garnet, and sillimanite. Overlies the Little Charley Pond Formation 

(new name); underlies the Lost Pond Marble (new name) or its Bog 

River Member (new name). Is intruded by the Otter Pond Dioritic 

Gneiss (new name). Thickness attains 420 m. Age is Precambrian. 

Beaver Creek Sand Member of the Winnebago Formation 

Pleistocene (Illinoian) 

Illinois 

Wisconsin arch 

Berg, R.C., and Kempton, J.P., 1985, Stratigraphic relationships of the Beaver Creek 

Sand Member of the Winnebago Formation: Illinois Geological Survey, Midwest 

Friends of the Pleistocene, 32d field conference, guidebook 19, p. 121-129. 

Type section: State Street Quarry Section, 100 m east of the BooneWinnebago County line, north of State Street, SW1f4SW1f4NW1f4 sec. 19, 

T. 44 N., R. 3 E., Boone County, Ill. Named for Beaver Creek in Boone 

County. 
24 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Beaver Creek Sand Member of the Winnebago Formation, here 

named, is in Boone and Winnebago Counties, Ill. Consists of yellow to 

tan, calcareous, crossbedded, contorted medium sands containing 

coarse cobbles and boulders. As the glacier that deposited the overlying 

Nimtz Till Member (new name) of the Winnebago overrode the Beaver 

Creek, the sand and gravel beds of the Beaver Creek were contorted 

and large inclusions of diamicton were thrust into the beds. Overlies the 

Glasford Formation and is the oldest member of the Winnebago. 

Thickness is 3. 5 m. Age is middle Pleistocene (Illinoian). 

Belfry Member of the Fort Union Formation 

Paleocene (Tiffanian) 

Montana 

Bighorn basin 

Yuretich, R.F., Hickey, L.J., Gregson, B.P., Hsia, Y.L., 1984, Lacustrine deposits in the 

Paleocene Fort Union Formation, northern Bighorn basin, Montana: Journal of 

Sedimentary Petrology, v. 54, no. 3, p. 836-852. 

Type section: Cody Road section, 2. 5 km south of the town of Belfry on 

State Highway 397 (Cody Road), sec. 27, T. 18 S., R. 22 E., Hollenbeck 

Draw 7.5-minute quadrangle, Carbon County, Mont. 

A lacustrine facies of the Fort Union Formation exposed near the 

center of the Clarks Fork basin, Montana, is here named the Belfry 

Member, following the informal usage of Hickey (1980). Consists of 

repetitive sequences of both fining-upward and coarsening-upward 

cycles of lenticular sandstone, siltstone and shale, mudstone, lignite, 

argillaceous and fossiliferous limestone, and tabular sandstone that are 

characterized by the predominance of laterally persistent, relatively 

thin beds. Grades into fluvial facies both laterally and vertically and lies 

within sediments belonging to the Tongue River Member of the Fort 

Union. Thickness may be as much as 600 m. Age is middle to late 

Paleocene (Tiffanian) based on megaflora and pollen. 

Belhaven Phosphatic Sand Member of the Pungo River 

Formation 

Miocene 

North Carolina 

Atlantic Coast basin 

Gibson, T.G., 1983, Stratigraphy of Miocene through lower Pleistocene strata of the 

United States central Atlantic Coastal Plain, in Ray, C.E., ed., Geology and paleontology of the Lee Creek Mine, North Carolina, I: Smithsonian Contributions to 

Paleobiology, no. 53, p. 35-80. 

Type section: AU-1-GRL corehole, depth interval 152-210 ft, near 

Aurora, Aurora 7.5-minute quadrangle, Beaufort County, N.C. Named 

for the town of Belhaven, Beaufort County. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 25 

The Belhaven Phosphatic Sand Member of the Pungo River Formation, here named, is in the Albemarle embayment in North Carolina. 

Consists of medium-greenish-brown phosphatic sand containing graygreen clay and limestone and dolomite beds. Unconformably overlies 

the Castle Hayne Formation; conformably underlies the Bonnerton 

Member (new name) of the Pungo River. Thickness at the type section 

is 58 ft. Age is early and middle Miocene. 

Belle Rive Coal Member of the Mattoon Formation of the 

Mcleansboro Group 

late Pennsylvanian (Missourian) 

Illinois 

Illinois basin 

Nance, R.B., and Treworgy, C.G., 1981, Strippable coal resources of Illinois: Part 8-

Central and southeastern counties: Illinois Geological Survey Circular 515, 32 p. 

Type section: Exposure along a tributary to Goose Creek, 6 mi south of 

the village of Belle Rive, SE1f4SE1f4NE1f4 sec. 35, T. 4 S., R. 4 E., 

Jefferson County, Ill. 

The Belle Rive Coal Member of the Mattoon Formation of the 

McLeansboro Group, here named, is in Jefferson County, Ill. Lies 400 

ft above the Shoal Creek Limestone Member of the Bond Formation and 

35 to 40 ft below the Opdyke Coal Member of the Mattoon. Correlates 

tentatively with the Loudon Coal Member (new name) of the Mattoon in 

Fayette County to the north. Thickness at the type section is 2 ft. Age 

is Late Pennsylvanian (Missourian). 

Bellingham Bay Member of the Chuckanut Formation 

Eocene 

Washington 

Bellingham basin 

Johnson, S.Y., 1984, Stratigraphy, age, and paleogeography of the Eocene Chuckanut 

Formation, northwest Washington: Canadian Journal of Earth Sciences, v. 21, no. 1, 

p. 92-106. 

Type section: Coastal exposures along Bellingham Bay and on Chuckanut Drive, sees. 9, 8, 7, and 6, T. 36 N., R. 3 E., sec. 1, T. 36 N., R. 

2 E., and sees. 36 and 25, T. 37 N., R. 2 E., Bellingham, Whatcom 

County, Wash. 

The Bellingham Bay Member is here named the basal member of the 

Chuckanut Formation in the Bellingham Bay area in the western part of 

the largest outcrop belt of the Chuckanut, which extends from the San 

Juan Islands to the foothills of the North Cascades, Wash. Consists of 

fining-upward cycles of coarse-grained, crossbedded, ripple-laminated 

sandstone and minor conglomerate intervals alternating with fine-
26 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

grained sandstone, mudstone, and minor coal intervals. A dacite 

lithic-tuff bed is near the top of the unit. Represents fine-load meandering river deposits in an extensive fluvial system. Unconformably 

overlies pre-Tertiary rocks; conformably underlies the Governors Point 

Member (new name) and Padden Member (new name), both of the 

Chuckanut, in the western part of the outcrop belt, and the Slide 

Member (new name) of the Chuckanut, in the eastern part of the 

outcrop belt. Thickness is 2, 700 m along Bellingham Bay in the west and 

3,300 min the east. Age is early Eocene based on zircon fission-track 

ages of about 55 Ma for the base and 49.9 Ma for the tuff at the top of 

the Bellingham Bay Member. 

Bellmore Formation 

Pleistocene (Wisconsinan) 

New York 

Atlantic Coast basin 

Rampino, M.R., and Sanders, J.E., 1981, Upper Quaternary stratigraphy of southern 

Long Island, New York: Northeastern Geology, v. 3, no. 2, p. 116--128. 

Type section: Borehole 200-C, Wantagh Pollution Control Plant, Wantagh, Nassau County, N.Y. Named for the town of Bellmore. 

Glacial outwash deposits in south-central Long Island, N.Y., are 

here named the Bellmore Formation. Consists of brown to yellowbrown, dense, cross bedded sand and gravelly sand. Unconformably 

overlies the Wantagh Formation (new name); forms the surficial sediment of much of south-central Long Island. Correlates with the Roslyn 

Drift of northern Long Island. Thickness at the type section is 31.5 ft. 

Age is late Pleistocene (late Wisconsinan). 

Bell Mountain Rhyolite of the St. Francois Mountains 

Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: SE1/4NE1/4 sec. 2, T. 33 N., R. 1 E., Edgehill quadrangle, 

Reynolds County, Mo. Named for Bell and North Bell Mountains, 

Reynolds and Iron Counties. 

Rocks previously mapped as the Bell Mountain ash flows by 

Anderson (1962) and the upper part of Unit D of the tuff of Stouts Creek 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 27 

by Anderson (1970) in the western St. Francois Mountains of southeast 

Missouri are here named the Bell Mountain Rhyolite. Consists of 

maroon to dark-maroon air-fall tuff containing lapilli and lithophysae. 

Overlies the Wildcat Mountain Rhyolite (new name); underlies the 

revised Royal Gorge Rhyolite. Thickness is 25 m. Age is Middle 

Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E.B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Bell Mountain Rhyolite. 

Belpre Ash Bed 

late Devonian 

Ohio, Kentucky, Pennsylvania, Tennessee, Virginia, West Virginia 

Illinois basin 

Roen, J.B., and Hosterman, J.W., 1982, Misuse of the term "bentonite" for ash beds of 

Devonian age in the Appalachian basin: Geological Society of America Bulletin, v. 93, 

no. 9, p. 921-925. 

Type section: Lamp 1 well, depth 1,182 m, Lot 66, Belpre Township, 

Washington County, Ohio. 

The informal Belpre bentonite of Collins (1979) is here named the 

Belpre Ash Bed. Lies in the Appalachian basin near the base of the 

black shale beds of the Olentangy Shale in the subsurface of eastern 

Ohio and eastern Kentucky; lies in the Rhinestreet Shale Member of the 

West Falls Formation in the subsurface of northwestern Pennsylvania, 

western West Virginia, southwestern Virginia, and northeastern Tennessee; and lies at the surface in southwestern Virginia and northeastern Tennessee in that part of the Chattanooga Shale that is equivalent 

to the Rhinestreet Shale Member in the subsurface. Consists of illite, 

kaolinite, illite-smectite mixed layer clay, quartz, and biotite. Thickness 

ranges from 0.5 to 30 em. Age is Late Devonian. 

Belvidere Till Member of the Glasford Formation 

Pleistocene (Illinoian) 

Illinois 

Wisconsin arch 

Kempton, J.P., Berg, R.C., and Follmer, L.R., 1985, Revision of the stratigraphy and 

nomenclature of glacial deposits in central northern Illinois: Illinois Geological Survey, 

Midwest Friends of the Pleistocene, 32d field conference, guidebook 19, p. 1-19. 
28 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Belvidere South Boring, near junction of U.S. Route 20 

and Genoa Road, 0.8 km southeast of Belvidere, NWl/4NWl/4NWl/4 sec. 

6, T. 43 N., R. 4 E., Boone County, Ill. 

The Belvidere Till Member of the Glasford Formation, here named, 

has been identified in exposures and borings in Boone, De Kalb, 

McHenry, and Kane Counties, Ill. Consists of pinkish to tan-brown 

diamicton and has a texture ranging from loam to clay loam to silty clay 

loam. Overlies the Esmond Till Member of the Glasford or older 

deposits where the Esmond is absent; underlies the Nimtz Till Member 

(new name) of the Winnebago Formation. Replaces the Capron Till 

Member in southern Boone, northern De Kalb, and southwestern 

McHenry Counties. Age is Pleistocene (Illinoian). 

Ben Hill Granite 

Mississippian to Pennsylvanian 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Community of Ben Hill, Ben Hill quadrangle, Fulton 

County, Ga. 

The Ben Hill Granite, here named, is in Fulton County, Ga. Consists 

of coarse-grained, porphyritic muscovite-biotite-quartz granite containing microcline phenocrysts. Is of batholithic size and intrudes the 

Clarkston, Stonewall, Wahoo Creek, and Clairmont Formations and the 

Norcross Gneiss, all of the Atlanta Group (all new names). The contact 

is sharp and discordant but is locally marked by dikes and sills of Ben 

Hill Granite alternating with altered country rocks over about a 30-m 

interval. Contains numerous xenoliths or roof pendants of country rock. 

Age is Mississippian to Pennsylvanian based on the age of zircon dated 

at 325 Ma. 

Big Bear Group 

Precambrian 

California 

Mohave basin 

Cameron, C.S., 1982, Stratigraphy and significance of the upper Precambrian Big Bear 

Group, in Cooper, J.D., Geology of selected areas in the San Bernardino Mountains, 

western Mohave desert, and southern Great Basin, California: Geological Society of 

America, Cordilleran Section, 78th Annual Meeting, guidebook, field trip 9, p. 5-20. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 29 

Type section: See type sections listed under individual subunit entries. 

Named for the Big Bear area, San Bernardino Mountains, San Bernardino County, Calif. 

Subunits: Wildhorse Meadows Quartzite, Lightning Gulch Formation, 

Moonridge Quartzite, Green Spot Formation, Delamar Mountain Formation. 

Following the informal usage of Cameron (1981), metasedimentary 

rocks preserved in roof pendants in the Big Bear area of the San 

Bernardino Mountains in California are here named the Big Bear 

Group. Rocks of the Big Bear Group have previously been included with 

the Sargossa Quartzite, Furnace Limestone, Chicopee Formation, and 

Chicopee Canyon Formation. The group is divided into (ascending) the 

Wildhorse Meadows Quartzite, Lightning Gulch Formation, Moonridge 

Quartzite, Green Spot Formation, and Delamar Mountain Formation 

(all new names). Unconformably overlies an older Precambrian gneiss 

complex; conformably underlies the uppermost Precambrian and Lower 

Cambrian Wood Canyon Formation, except in the Sugarloaf Mountain 

area where the contact is a fault or intrusive contact. Age is late 

Precambrian. 

Big Bend Ridge Rhyolite 

Pleistocene 

Idaho 

Snake River basin 

Christiansen, R. L., 1982, Late Cenozoic volcanism of the Island Park area, eastern Idaho, 

in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic geology of Idaho: Idaho 

Bureau of Mines and Geology Bulletin 26, p. 345-368. 

Type area: Caldera scarp at the base of Bishop Mountain, Big Bend 

Ridge caldera segment, Island Park area, Fremont County, Idaho. 

The Big Bend Ridge Rhyolite is here named and includes four lava 

flows, named the Bishop Mountain, Green Canyon, Blue Creek, and 

Headquarters flows, located on the rim and outer flank of Island Park 

between Big Bend and Thurmon Ridges in Fremont County, Idaho. 

Consists of rhyolite containing phenocrysts of quartz, sanidine, and 

plagioclase. Overlies the Huckleberry Ridge Tuff; underlies the Mesa 

Falls Tuff. The rhyolite may represent Pleistocene postcollapse flows of 

the first volcanic cycle (2. 0 Ma) or precollapse flows of the second 

volcanic cycle (1.3 Ma) or both. 
30 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Big Cotton Indian Formation of the Atlanta Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Exposures near Big Cotton Indian Creek and its tributaries, Jonesboro quadrangle, Clayton County, Ga. 

The Big Cotton Indian Formation of the Atlanta Group (new name), 

here named, is in the Newnan-Tucker synform near Atlanta, Ga. 

Consists of biotite-plagioclase gneiss, hornblende-plagioclase amphibolite, and biotite-muscovite schist. Gradationally overlies the Clarkston 

Formation (new name); gradationally underlies the Camp Creek Formation (new name), both of the Atlanta Group. Thickness is as much as 

4,000 m. Age is Late Proterozoic and (or) early Paleozoic. 

Big Goose Member of the Madison Limestone 

Early Mississippian (Osagean) 

Wyoming, Montana 

Powder River basin 

Sando, W.J., 1982, New members of the Madison Limestone (Devonian and Mississippian), north-central Wyoming and southern Montana: U.S. Geological Survey Bulletin 

1529-H, p. H125-H130. 

Type section: Little Tongue River section, NEl/4 sec. 27, T. 56 N., R. 87 

W., Sheridan County, Wyo. Named for exposures on Big Goose Creek, 

NWl/4 sec. 2, T. 54 N., R. 86 W. 

The informal cherty dolomite member of Sando (1972) is here named 

the Big Goose Member, one of six members of the Madison Limestone 

in the Powder River basin in north-central Wyoming and southern 

Montana. Is also recognized in the subsurface in the Bighorn, Wind 

River, and Powder River basins. Consists of predominantly finegrained, thin- to medium-bedded, cherty dolomite and dolomitic limestone. Autobrecciation and shattering are distinctive features. Conformably overlies the W oodhurst Member of the Madison; conformably 

underlies the Little Tongue Member (new name) of the Madison. 

Thickness is 55.5 mat the type section and ranges from 38 to 100m. Age 

is Early Mississippian (Osagean) based on corals and brachiopods. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 31 

Big Island Formation 

Miocene 

Idaho, Nevada 

Great Basin province 

Coats, R.R., 1985, The Big Island Formation, a Miocene formation in northern Elko 

County, Nevada, and adjacent Idaho, including a consideration of its composition and 

petrographic character: U.S. Geological Survey Bulletin 1605-A, p. A7-A13. 

Type section: West wall of the Jarbidge River Canyon, about 122 m 

west-northwest of the confluence of Buck Creek and the Jarbidge 

River, center N¥2 sec. 28, T. 16 S., R. 9 E., Dishpan quadrangle, 

Owyhee County, Idaho. Named for Big Island, a plateau on the east and 

west sides of the Jarbidge River, in Elko County, Nev., and Owyhee 

County, Idaho. 

A sequence of nonmarine sedimentary and volcanic rocks exposed on 

the western part of Big Island, a plateau between the Jarbidge River 

and its East Fork, and on the east and west sides of the river in Elko 

County, Nev., and Owyhee and Twin Falls Counties, Idaho, is here 

named the Big Island Formation. Consists of three lenticular units, a 

lower boulder gravel about 100 m thick, a middle weathered dacitic tuff 

6 m thick, and an upper gray tholeiitic olivine basalt 60 m thick. Much 

of the basalt was originally included in the Banbury Volcanics. Discrepancies in the age of that unit, renamed the Banbury Basalt, led to the 

conclusion that the Banbury does not represent a formation of limited 

stratigraphic position or age range. The Banbury of the type locality is 

not continuous with the basalts of the Big Island plateau, therefore they 

are assigned to the Big Island Formation, and the name Banbury is 

excluded from this area. Overlies the Cougar Point Welded Tuff; 

discontinuously underlies unconsolidated Quaternary deposits. Age is 

late Miocene based on stratigraphic position and potassium-argon ages 

of basalt. 

Big Valley Formation of the Three Forks Group 

late Devonian 

Alberta, Saskatchewan, Montana 

Williston basin 

Christopher, J.E., 1961, Transitional Devonian-Mississippian formations of southern 

Saskatchewan: Saskatchewan Department of Mineral Resources Report 66, 103 p. 

Type section: Gulf Rumsey no. 6-30 (Lsd. 6-30-33-21 w4) well, depth 

interval 5,250-5,295 ft, Stettler area, Alberta, Canada (W onfor and 

Andrichuck, 1956). 

The Big Valley Member of the Three Forks Formation, named by 

Wonfor and Andrichuck (1956), is here revised as the Big Valley 

Formation of the Three Forks Group in Saskatchewan and the 
32 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

southwest-trending erosional edge of the Big Valley is extended in the 

subsurface into Montana at R. 13 W. of the Third Meridian. Consists of 

green shale laminated with shale containing thin layers of pyrite. 

Overlies the Torquay Formation; underlies and interfingers with the 

lower member of the Bakken Formation. Thickness ranges from 115 ft 

in Saskatchewan to 25 ft in Montana. In many areas of Montana only 

erosional remnants are found. Age is Late Devonian. 

Bill Arp Formation of the Sandy Springs Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Abrams, C.E., and McConnell, K.I., 1981, Stratigraphy of the area around the AustellFrolona antiform; west-central Georgia, in Wigley, P.B., ed., Latest thinking on the 

stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 55-67. 

Type locality: Exposures near the town of Bill Arp, Winston 7.5-minute 

quadrangle, Carroll County, Ga. 

The Bill Arp Formation, used informally by Crawford and Medlin 

(1974) and here named, is in the Austell-Frolona antiform in westcentral Georgia. Includes the informal Union Grove Churcq schist of 

Crawford and Medlin (1974) and is assigned to the informal Roosterville 

group. Consists of inter layered mica schist and metagraywacke. Stratigraphically overlies but, because of refolding, structurally underlies 

the New Georgia Group (new name) and the Andy Mountain Formation 

(new name). Is intruded by the Austell Gneiss. Age is Proterozoic. 

McConnell, K.I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

The Bill Arp Formation is here assigned to the Sandy Springs Group 

(western belt) in the Austell-Frolona antiform. Age is Late Proterozoic 

and (or) early Paleozoic. 

Bitter Ridge Limestone Member of the Horse Spring Formation 

Miocene 

Nevada 

Great Basin province 

Bohannon, R.G., 1984, Nonmarine sedimentary rocks of Tertiary age in the Lake Mead 

region, southeastern Nevada and northwestern Arizona: U.S. Geological Survey 

Professional Paper 1259, 72 p. 

Type section: Exposures at Bitter Ridge in the Muddy Mountains, lat 

36°18'30" N., long 114°35' W., Muddy Peak 15-minute quadrangle, 

Clark County, Nev. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 33 

Lacustrine limestone that composes the hogback of Bitter Ridge 

between Bitter Spring Valley and White Basin in the Muddy Mountains 

in Clark County, Nev., is here named the Bitter Ridge Limestone 

Member of the Horse Spring Formation. Consists of uniform lightbrown, yellow, and pale-pink crystalline limestone, chiefly stromatolitic, and is divided into wavy-bedded and stromatolitic mound subfacies. Contains some locally gypsiferous red and yellow sandstone 

beds. Unconformably overlies Paleozoic rocks or conformably overlies 

the here revised Thumb Member of the Horse Spring where the base is 

defined at the top of the stratigraphically highest sandstone bed of the 

Thumb Member. Conformably underlies the Lovell Wash Member (new 

name) of the Horse Spring where the top of the Bitter Ridge is defined 

at the top of the uppermost resistant limestone bed below the tuffaceous 

beds of the Lovell Wash Member. Thickness at the type section is 375 

m and ranges from 300 to 400 m. Age is Miocene based on potassiumargon and fission-track dates. 

Black Knob Chert Member of the Tenmile Creek Formation 

of the Stanley Group 

Late Mississippian 

Oklahoma 

Ouachita tectonic belt province 

Pitt, W.D., Fay, R.O., Wilson, L.R., and Curiale, J.A., 1982, Geology of Pushmataha 

County, Oklahoma: Eastern New Mexico University Studies in Natural Sciences 

Special Publication 2, 101 p. 

Type locality: Outcrop on the east side of Black Knob Ridge, T. 1 S., 

R. 12 E., Atoka County, Okla. 

The Black Knob Chert Member, here named, is in the lower part of 

the Tenmile Creek Formation of the Stanley Group in the Ouachita 

Mountains in Atoka County, southeastern Oklahoma. Consists of a bed 

of fossiliferous siliceous shale near the base of the Tenmile Creek. 

Thickness is about 20 ft. Age is Late Mississippian. 

Blackoak Coal Member of the Kalo Formation of the 

Cherokee Group of the Des Moines Supergroup 

Middle Pennsylvanian (Atokan) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 
34 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Exposures along an intermittent tributary of Cedar Creek 

in an abandoned rock quarry in NW1/4SE1/4, sec. 31, T. 75 N., R. 17 W., 

Mahaska County, Iowa. Named for Blackoak Township. 

The Blackoak Coal Member, here named, is the lower of two 

members of the Kalo Formation (new name) of the Cherokee Group in 

south-central Iowa. Unit extends over a significant portion of the study 

area, and, to the south and west, splits into two or more closely spaced 

beds. The names Manbeck and Hastie were applied to coal beds in Polk 

County by Landis and Van Eck (1965) and may refer at least in part to 

the Blackoak. Contains abundant pyrite nodules and fusain. Is the 

biostratigraphic equivalent of the Pope Creek Coal Member of the 

Abbott Formation. Overlies the Kilbourn Formation (new name); 

underlies silty, carbonaceous shale below the Cliffland Coal Member 

(new name). Thickness is highly variable, ranging from 4.5 in. at the 

type section to 5. 7 ft. Age is Middle Pennsylvanian (late Atokan). 

Blair Creek Formation of the Marquette Range Supergroup 

Early Proterozoic 

Michigan 

Wisconsin arch 

Sims, P.K., Peterman, Z.E., Prinz, W.C., and Benedict, F.C., 1984, Geology, geochemistry, and age of Archean and Early Proterozoic rocks in the Marenisco-Watersmeet 

area, northern Michigan: U.S. Geological Survey Professional Paper 1292-A, 

p. A1-A41. 

Type area: Exposures in thevicinityofBlairCreek, T. 46N., R. 40-41 W., 

Gogebic County, Mich. 

The basal volcanic unit of the Marquette Range Supergroup on the 

southeast limb of the Copps syncline east of the Gogebic Range in 

Michigan is here named the Blair Creek Formation. Is divided into five 

map units: basal conglomerate, grit, and wacke; mafic volcanic rocks; 

iron-formation; volcanic rocks; and an unexposed magnetic unit at the 

top. Unconformably overlies Archean gneiss and greenstone-granite 

basement terranes; subconformably underlies the Copps and Michigamme Formations of the Baraga Group of the Marquette Range 

Supergroup. Is intruded by Early Proterozoic metadiabase dikes. 

Maximum thickness is 2,000 m. Age is Early Proterozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 35 

Blankenship Member of the Otuk Formation of the Etivluk 

Group 

Early and Middle jurassic (Sinemurian to Bajocian) 

Alaska 

Arctic Foothills province 

Mull, C.G., Tailleur, I.L., Mayfield, C.F., Ellersieck, Inyo, and Curtis, S., 1982, New 

upper Paleozoic and lower Mesozoic stratigraphic units, central and western Brooks 

Range, Alaska: American Association of Petroleum Geologists Bulletin, v. 66, no. 3, 

p. 348-362. 

Type section: Cutbanks along a west-flowing tributary of Blankenship 

Creek, a tributary of the Ipnavik River, on the south side of Lisburne 

Ridge, NEl/4 sec. 36, T. 9 S., R. 21 W., Howard Pass quadrangle, 

Alaska. Principal reference section designated. 

The Blankenship Member, here named, is locally present in the 

uppermost part of the Otuk Formation (new name) of the Etivluk Group 

(new name) in the Etivluk River area of the Howard Pass and Killik 

River quadrangles of the Brooks Range, Alaska. Consists of rhythmically interbedded black fissile oil shale, dark-gray chert, and minor 

amounts of dolomitic limestone. Lower and upper contacts of the 

Blankenship represent disconformities or nondepositional hiatuses with 

the lower part of the allochthonous Otuk Formation and with Lower 

Cretaceous claystone and shale. Thickness is 7 m at the type section. 

Age is middle Early Jurassic through early Middle Jurassic (Sinemurian 

through middle Bajocian) based on fossils. 

Blue Canyon Tuff of the Datil Group 

Oligocene 

New Mexico 

Basin and Range province 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: Northwest side of Main Canyon near its junction with 

Blue Canyon, 7 mi north of Datil, 1.1 mi northeast of the junction of 

Cibola National Forest road 14 and the road into Blue Canyon, 

NEl/4SEl/4 sec. 1, T. 1 S., R. 10 W., Datil Mountains, Cal Ship Mesa 

7.5-minute quadrangle, Catron County, N. Mex. 

The Blue Canyon Tuff of the Datil Group, here named, is in the Datil 

Mountains and northwest Gallinas Mountains in southwestern New 

Mexico. Thins to the east and is absent in the Socorro-Magdalena area. 

Consists of brown- to purple-gray, unwelded to poorly welded, moderately crystal-rich quartz-latite ash-flow tuff. Is interbedded with the 

Rincon Windmill Member (new name) of the Spears Formation of the 
36 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Datil Group and locally splits the Rincon Windmill Member into two 

tongues. Overlies the Rock House Canyon Tuff (new name) of the Datil 

Group; underlies the Hells Mesa Tuff. Thickness at the type section is 40 

ft and attains 100 ft. Age is Oligocene based on a potassium-argon 

biotite date of 33.3 Ma and a zircon fission-track date of 33.2 Ma. 

Blue Gulch Mudstone Member of the Hornbrook Formation 

late Cretaceous (Campanian to Maastrichtian) 

California, Oregon 

Klamath Mountains province 

Nilsen, T.H., 1984, Tectonics and sedimentation of the Upper Cretaceous Hornbrook 

Formation, Oregon and California, in Crouch, J.K., and Bachman, S.B., eds., 

Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and Mineralogists, Pacific Section, v. 38, p. 101-118. 

Type section: Composite of five localities near Blue Gulch, Rancheria 

Gulch, and Hilt, sees. 20, 21, 27, 33, and 34, T. 47 N., R. 6 W., 

Hornbrook 15-minute quadrangle, Siskiyou County, Calif. Named for 

Blue Gulch, southeast of the Klamath River, 4 km south of Hornbrook. 

Subunits: Rancheria Gulch Sandstone Beds, Hilt Bed. 

The Blue Gulch Mudstone Member is here named the uppermost 

member of the Hornbrook Formation along the northeast margin of the 

Klamath Mountains in Siskiyou County, Calif., and Jackson County, 

Oreg. Includes a lower part consisting of interbedded gray siltstone and 

sandstone; the Rancheria Gulch Sandstone Beds (new name) consisting 

of fine-grained gray sandstone; a middle part consisting of interbedded 

gray mudstone, siltstone, and sandstone and the Hilt Bed (new name); 

an upper middle part consisting of interbedded gray mudstone and 

sandstone; and an upper part consisting of gray mudstone and siltstone. 

Conformably and gradationally overlies the Rocky Gulch Sandstone 

Member (new name), or locally, the Ditch Creek Siltstone Member (new 

name), both of the Hornbrook; unconformably underlies Tertiary nonmarine gravels and volcanic rocks. Thickness is 912.5 m at the type 

section. Age is Late Cretaceous (early Campanian to early Maastrichtian) based on foraminifera and ammonites from the part of the Blue 

Gulch above the Rancheria Gulch Sandstone Beds. 

Blue Mound Shale Member of the Shale Hill Formation of 

the Pleasanton Group 

late Pennsylvanian (Missourian) 

Missouri 

Forest City basin 

Howe, W.B., 1982, Stratigraphy of the Pleasanton Group, Pennsylvanian System in 

Missouri: Missouri Department of Natural Resources, Open File Report Series 

OFR--82-10-GI, 99 p. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 37 

Type section: Exposure in roadcut through hill, 3 mi northwest of Blue 

Mound, NW1/4SWV4 sec. 28, T. 56 N., R. 24 W., Livingston County, Mo. 

The Blue Mound Shale Member is here named the uppermost of 

three members of the Shale Hill Formation (new name) of the 

Pleasanton Group in the Forest City basin in northwestern Missouri. 

The lower part of the Blue Mound Shale Member contains the Locust 

Creek coal, called the Ovid coal in earlier reports. The Locust Creek 

coal is a bed or zone of thin impure coal beds of variable thickness 

ranging from a thin streak to 2. 5 ft and including clay partings and is of 

generally poor quality. Recognition in western Missouri is tentative. 

The upper part of the Blue Mound Member consists of silty, micaceous, 

sparsely fossiliferous, gray to drab shale that is silty and maroon or 

gray-green in the uppermost part and sandstone, called upper Knobtown by drillers, that occupies channels cut through the Knobtown 

Limestone Member of the Shale Hill Formation. Conformably overlies 

the Weldon River Sandstone Member (new name) or the Knobtown 

Limestone Member, both of the Shale Hill; disconformably underlies the 

Critzer Limestone Member of the Hertha Formation of the Kansas City 

Group. Thickness is 18 ft at the type section and averages 25 ft. Age is 

Late Pennsylvanian (early Missourian). 

Bobcaygeon Formation 

Middle Ordovician 

Ontario, Pennsylvania 

Appalachian basin 

Wagner, W.R., 1966, Stratigraphy of the Cambrian to Middle Ordovician rocks of central 

and western Pennsylvania: Pennsylvania Geological Survey Bulletin G 49, 156 p. 

Type section: Composite of Nogies Creek road cut, Little Bob quarry, 

and Number 36 highway road cut south of the town of Bobcaygeon, 

Ontario, Canada. (Liberty, 1969). 

The Bobcaygeon Formation of Liberty (1964) is here extended from 

Ontario, Canada, to northwestern Pennsylvania in the subsurface along 

Lake Erie in Erie County. Consists of interbedded calcarenite, calcilutite, and calcisiltite and occupies the position of the Benner Formation 

to the east. As in Ontario, the Bobcaygeon overlies the Gull River 

Formation and underlies the V erulam Formation, which grades into the 

N ealmont Formation in northwestern Pennsylvania. Age is Middle 

Ordovician. 
38 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Bog River Member of the lost Pond Marble 

Precambrian 

New York 

Adirondack uplift 

Potter, D.B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: Exposures along Bog River, Tupper Lake 15-minute 

quadrangle, St. Lawrence County, N.Y. 

The Bog River Member of the Lost Pond Marble (new name), here 

named, is in the Loon Pond syncline in the Bog River synclinorium in 

the Adirondack Highlands, Hamilton and St. Lawrence Counties, N.Y., 

where it is the basal member of the Lost Pond. Consists of calcitequartz-clinopyroxene marble. Overlies the Bear Pond Gneiss (new 

name). Is intruded by the Otter Pond Dioritic Gneiss (new name). 

Thickness is 300 m. Age is Precambrian. 

Boil Mountain Complex 

Cambrian(?) and Early Ordovician(?) 

Maine 

New England province 

Boudette, E.L., 1982, Ophiolite assemblage of early Paleozoic age in central-western 

Maine, in St-Julien, P., and Beland, J., eds., Major structural zones and faults of the 

northern Appalachians: Geological Association of Canada Special Paper 24, p. 209-230. 

Type section: Composite of the two east-west elongate contiguous parts 

of the complex, 15 km north of Kennebago Lake, Franklin County, 

Maine. Named for Boil Mountain, 14 km north of Kennebago Lake. 

Plutonic rocks of the ophiolite sequence in central-western Maine 

are here named the Boil Mountain Complex. Consists of serpentinite, 

pyroxenite, gabbro, epidiorite, and tonalite, all extensively altered by 

tectonism and metamorphism, especially in the southwest where segments of serpentinite have been remobilized to form diapiric serpentinite. At the base, epidiorite, gabbro, and serpentinite are in sharp, 

concordant contact with the Chain Lakes massif. Along the southeastern edge, probably the stratigraphic top, tonalite is in undisturbed 

contact with greenstone of the Jim Pond Formation (new name). Age is 

Cambrian(?) and Early Ordovician(?). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 39 

Bone Island Formation 

Early Cretaceous (Coahuilan) 

Florida 

South Florida province 

Applegate, A. V., Winston, G.O., and Palacas, J.G., 1981, Subdivision and regional 

stratigraphy of the Pre-Punta Gorda rocks (Lowermost Cretaceous-Jurassic(?)) in 

south Florida: Gulf Coast Association of Geological Societies Transactions, October, v. 

31 (supplement), p. 447-453. 

Type section: Mobil-Phillips Number 1 Seminole well P-565B, depth 

interval13, 750-15,100 ft, sec. 28, T. 48 S., R. 33 E., Hendry County, 

Fla. Named for Bone Island in the Big Cypress Swamp. 

The Bone Island Formation, here named, occurs in the subsurface of 

the South Florida basin, where it is one of four regionally persistent 

anhydrite units below the Punta Gorda Anhydrite of the Glades Group. 

Consists of anhydrite and buff to cream oolitic limestone containing 

some micritic limestone or dolomite. Overlies the Wood River Formation (new name); underlies the Pumpkin Bay Formation (new name); 

the contact is at the top of a regionally persistent 200-ft anhydrite bed. 

Thickness at the type well is 1,350 ft. Age is Early Cretaceous (early 

Coahuilan) based on stratigraphic position. 

Boney Spring Formation 

Pleistocene (Wisconsinan) 

Missouri 

Ozark uplift 

Haynes, C.V., Jr., 1985, Mastodon-bearing springs and late Quaternary geochronology of 

the lower Pomme de Terre valley, Missouri: Geological Society of America Special 

Paper 204, 35 p. 

Type locality: Boney Spring, 3.2 km northwest of Breshears Valley 

near Avery, sec. 29, T. 39 N., R. 22 W., Fristoe 15-minute quadrangle, 

Benton County, Mo. 

Alluvium deposits in the T -1 terrace of the Breshears Valley, 

Benton and Hickory Counties, Mo., are here named the Boney Spring 

Formation, following the informal usage of Brakenridge (1981). Consists of 5 to 7 m of gray to olive interbedded organic clay, clayey silt, and 

peat overlying 1 to 3 m of chert pebble gravel; also has intrusions of 

spring-laid granular tufa and clay containing spruce logs and bones of 

mastodon, giant beaver, ground sloth, and smaller animals. Unconformably overlies the Breshears Valley Formation (new name) and the 

Trolinger Spring Formation (new name) with an erosional hiatus of 

2,000 to 3,000 years; unconformably underlies the Rodgers Shelter 

Formation (new name) with an erosional hiatus. Age is late Pleistocene 

(late Wisconsinan) based on pollen and bones. 
40 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Bonnerton Member of the Pungo River Formation 

Miocene 

North Carolina 

Atlantic Coast basin 

Gibson, T.G., 1983, Stratigraphy of Miocene through lower Pleistocene strata of the 

United States central Atlantic Coastal Plain, in Ray, C.E., ed., Geology and paleontology of the Lee Creek Mine, North Carolina, 1: Smithsonian Contributions to 

Paleobiology, no. 53, p. 35-80. 

Type section: AU-1-GRL core hole, depth interval 120-152 ft, near 

Aurora, Aurora 7.5-minute quadrangle, Beaufort County, N.C. Named 

for the town of Bonnerton, Beaufort County. 

The Bonnerton Member of the Pungo River Formation, here named, 

occurs in the southern part of the Albemarle embayment, North 

Carolina. Consists of white to light-gray-green phosphatic limestone 

and sand, calcareous clay, and coquina. Conformably overlies the 

Belhaven Phosphatic Sand Member (new name) of the Pungo River; 

unconformably underlies the Yorktown Formation. Thickness is 32 ft at 

the type section. Age is middle Miocene. 

Boqueron Basalt 

late Cretaceous (Campanian) 

Puerto Rico 

Volckmann, R.P., 1984, Upper Cretaceous stratigraphy of southwest Puerto Rico: A 

revision: U.S. Geological Survey Bulletin 1537-A, p. A73-A83. 

Type locality: None designated. Crops out from Morales Diaz on the 

eastern border of the Puerto Real 7.5-minute quadrangle to the town of 

Boqueron on the Bahia de Boqueron in the west, Puerto Rico. 

Basaltic lava in the Puerto Real quadrangle in southwestern Puerto 

Rico, previously mapped by Mattson (1960) as part of the now abandoned San German Formation or undifferentiated Cretaceous(?) volcanic rocks, is here named the Boqueron Basalt. Consists of darkgray-brown to greenish-brown or dark-gray porphyritic, locally 

amygdular, pyroxene-olivine-oxyhornblende basaltic lava and minor 

amounts of breccia and tuff that have poorly developed flow banding 

overlain by a line of 5- to 10-m-thick limestone lenses. Coarse-grained, 

medium-bedded volcanic wacke as much as 150 m thick occurs at the top 

of the Boqueron. Lack of pillows suggests subaerial deposition of lava; 

the limestone lenses and volcanic wacke represent local submergence 

following deposition of the basalt. Is interbedded with identical volcanic 

wacke at the base of the Lajas Formation (new name) and appears to 

underlie the Lajas with minor disconformity. Age is Late Cretaceous 

(middle Campanian or older) based on fossils in the overlying Cotui 

Limestone. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 41 

Border Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Sinha, A.K., and Bartholomew, M.J., 1984, Evolution of the Grenville terrane in the 

central Virginia Appalachians: Geological Society of America Special Paper 194, 

p. 175--186. 

Type locality: Outcrops on the Tye River, 650 m north of the junction 

with Virginia Highways 151 and 56, Horseshoe Mountain 7.5-minute 

quadrangle, Nelson County, Va. Derivation of name not stated. 

The informal Border Gneiss of Hillhouse (1960), here formally 

named, occurs in the Lovingston massif in the central Blue Ridge, Va. 

Consists of feldspathic and garnet graphite gneisses and separates the 

Roseland Anorthosite from the other units of the massif. Age is Middle 

Proterozoic. 

Bottom Creek Suite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: None designated. Named for Bottom Creek, lat 37°08' 

N., long 80° W., Elliston quadrangle, Montgomery County, Va. 

The Bottom Creek Suite, here named, occurs in the Pedlar massif in 

the Blue Ridge of Virginia and is a charnockite suite that contains 

mesocharnockite, megaporphyry, and porphyroblastic gneiss rock 

types. Age is Middle Proterozoic. 

Bow River Quartzite of the Phantom lake Metamorphic Suite 

Archean 

Wyoming 

Green River basin 

Karlstrom, K.E., Houston, R.S., Coolidge, C.M., Flurkey, A.J., and Sever, C.K., 1981, 

The geology of Archean and Early Proterozoic terraines of the Medicine Bow 

Mountains, Wyoming, in Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, 

eds., A summary of the geology and uranium potential of Precambrian conglomerates 

in southeastern Wyoming: U.S. Department of Energy National Uranium Resource 

Evaluation, v. 1, pt. 2, p. 197-399. 

Type local iffy: None designated. Well exposed throughout the northern 

Medicine Bow Mountains, Carbon County, Wyo. Derivation of name not 

stated. 
42 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Bow River Quartzite, here named, of the Phantom Lake 

Metamorphic Suite, defines the limbs of French J oes anticlinorium in 

the northern Medicine Bow Mountains, Wyo. Consists of fine-grained 

muscovitic quartzite, local conglomerate, local biotite and hornblende 

schist and phyllite, and local quartz-rich carbonates. Abundant planar 

crossbeds and ripple marks indicate the direction of the stratigraphic 

top. Gradationally or sharply and conformably overlies the Rock Mountain Conglomerate (new name) of the Phantom Lake; underlies the 

Colberg Metavolcanic Rocks and the Conical Peak Quartzite (both new 

names) of the Phantom Lake. Thickness ranges from 200 to 580 m and 

averages 350 m. Age is Archean. 

Box Canyon Member of the Tiger Formation 

Eocene, Oligocene, Miocene 

Washington 

Northern Cascade Range-Okanogan province 

Gager, B.R., 1983, Stratigraphy of the Tiger Formation, northeastern Washington: 

Northwest Geology, v. 12, p. 25-41. 

Type section: Road and stream cuts northwest and west of the Box 

Canyon Dam on the Pend Oreille River, SEl/4SEl/4SWl/4 sec. 18 and 

Nl/2NWl/4 sec. 19, T. 38 N., R. 43 E., and El/2 sec. 13, T. 38 N., R. 42 E., 

Pend Oreille County, Wash. 

The Box Canyon Member, here named, is in the revised Tiger 

Formation in the area northwest and southwest of lone and west to 

southwest of Tiger in northeastern Washington. Consists of massive to 

horizontally and planar crossbedded conglomerate and minor amounts 

of sandstone, siltstone, shale, and coal. Clast lithology varies laterally. 

Overlies Paleozoic strata and possibly overlies Precambrian greenstone 

and Cretaceous granite; pinches out below the Lost Creek Member 

(new name) of the Tiger Formation south of Tiger. Thickness is at least 

600 mat the type section and may be more than 1,500 m. Age ranges 

from early middle Eocene, based on inclusions of late early to early 

middle Eocene volcanic rock clasts, through middle Miocene, although 

the age determination of middle Miocene, based on middle Miocene 

regional faults that bound the Tiger Formation, is less definite. 

Brady Member of the Gower Formation 

Silurian (Wenlockian and Ludlovian) 

Iowa 

Iowa shelf 

Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River fault zone and 

the structural and stratigraphic framework of eastern Iowa: Iowa Geological Survey 

Technical Information Series 13, 126 p. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 43 

Type locality: Outcrops in the Brady (McGuire) quarry, SEl/4SEl/4 sec. 

14, T. 80 N., R. 3 W., Cedar County, Iowa. 

The informal Brady facies of Philcox (1970) is here named the Brady 

Member of the Gower Formation and is restricted to areas in Jones, 

Cedar, and Linn Counties, Iowa. Consists of mounded sequences of 

fossil-moldic and fossil-replaced dolomites that have wackestone, packstone, and boundstone fabrics and abundant brachiopods and rugose 

corals. Overlies the Palisades-Kepler Member (new name) of the Scotch 

Grove Formation (new name); is laterally equivalent to the Anamosa 

Member of the Gower and to the LeClair Member of the Gower in Scott 

County; unconformably underlies Devonian strata. The Brady represents a second stage of carbonate mound building above the older 

Palisades-Kepler mounds and is surrounded by laminated dolomites of 

the Anamosa Member. Age is Silurian (late Wenlockian and Ludlovian). 

Branch River Member of the Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Greenleaf Quarry, on the north side of Highway 96, 0.7 

km east of Greenleaf, SEl/4SWl/4 sec. 4, T. 21 N., R. 20 E., Greenleaf 

7.5-minute quadrangle, Brown County, Wis. Named for the Branch 

River in Morrison Township, Denmark 15-minute quadrangle. 

The lowest of three members of the Kewaunee Formation (new 

name) in the Green Bay Lobe east of an arbitrary vertical cutoff at the 

Fox River is named the Branch River Member, following the informal 

usage of McCartney and Mickelson (1982). Consists of brown sandy 

silty, clay till. Overlies dolomite bedrock or till and gravel of the Horicon 

Formation (new name); underlies the Chilton Member (new name) of 

the Kewaunee or is the surface unit. Is equivalent to the Silver Cliff 

Member (new name) of the Kewaunee west of the Fox River in the 

Green Bay Lobe and to the Ozaukee Member (new name) of the 

Kewaunee in the Lake Michigan Lobe. Average thickness is 2 m. Age is 

late Pleistocene (late Wisconsinan). 
44 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Breshears Valley Formation 

Pleistocene (pre-Sangamonian) 

Missouri 

Ozark uplift 

Haynes, C.V., Jr., 1985, Mastodon-bearing springs and late Quaternary geochronology of 

the lower Pomme de Terre valley, Missouri: Geological Society of America Special 

Paper 204, 35 p. 

Type locality: Breshears Valley, near Avery, sec. 4, T. 38 N., R. 22 W., 

Fristoe 15-minute quadrangle, Benton County, Mo. 

Alluvial deposits of the lowest T --3 terrace in the Breshears Valley, 

an abandoned meander of the Pomme de Terre River, in Benton and 

Hickory Counties, Mo., called the informal Breshears formation by 

Brakenridge (1981), are here named the Breshears Valley Formation. 

Consists of a strath of oxidized chert gravels with a strong red, relict 

soil. Unconformably overlies Paleozoic dolomite and sandstone; unconformably underlies alluvial terrace deposits named the Trolinger 

Spring, Boney Spring, Rodgers Shelter, and Pippins Cemetery Formations (all new names). Age is Pleistocene (possibly pre-Sangamonian), 

based on a Sangamonian age for basal peat of the overlying Trolinger 

Spring Formation. 

Bristol Hill Coal Member of the Bond Formation 

late Pennsylvanian (Missourian) 

Illinois 

Illinois basin 

Nance, R.B., and Treworgy, C.G., 1981, Strippable coal resources of Illinois: Part 8-

Central and southeastern counties: Illinois Geological Survey Circular 515, 32 p. 

Type section: Exposure along Bristol Hill, center NE1/4NE1/4 sec. 12, T. 

6 N., R. 11 W., Heathsville 7.5-minute quadrangle, Crawford County, 

Ill. 

The Bristol Hill Coal Member of the Bond Formation of the 

McLeansboro Group, here named, occurs in the area of Flat Rock, 

Crawford County, Ill. Local informal name is Flat Rock Coal. At the 

type area the coal underlies marine limestone tentatively correlated 

with the lower portion of the Livingston Limestone Member of the 

Bond. Lies 35 to 40 ft above a black shale and thin coal correlated with 

the Witt Coal Member of the Bond and 280 ft above the West Franklin 

Limestone Member of the Modesto Formation. Thickness is 10 in. at the 

type section. Age is Late Pennsylvanian (Missourian). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 45 

Browns Ferry Member of the Rhems Formation of the Black 

Mingo Group 

Paleocene (Danian, Midwayan) 

South Carolina 

Atlantic Coast basin 

Van Nieuwenhuise, D.S., and Colquhoun, D.J., 1982, The Paleocene-lower Eocene Black 

Mingo Group of the east central Coastal Plain of South Carolina: South Carolina 

Geology, v. 26, no. 2, p. 47-67. 

Type section: Composite of outcrops at Browns Ferry on the Black 

River and underlying strata revealed by auger hole CV2, 15ft (4.6 m) 

away from the outcrop, Georgetown County, S.C. 

The Browns Ferry Member, here named, is the lower member of the 

Rhems Formation of the Black Mingo Group in the Coastal Plain of 

South Carolina. The here revised Black Mingo Group includes all strata 

from the base of the Paleocene to the unconformity at the top of the 

Eocene Ypresian Stage and is divided into the Rhems Formation of the 

Danian Stage, the Williamsburg Formation of the Thanetian Stage, and 

unnamed Ypresian strata. [Of the Clubhouse Crossroads core hole 

Number 1, Gohn and others (1978) assigned the entire Paleocene section 

to the Black Mingo Formation, and Gohn and others (1983) named the 

Ypresian strata the Fishburne Formation (new name).] The Browns 

Ferry Member consists of indurated, fossiliferous, clayey sand beds. 

Unconformably overlies the Peedee Formation; unconformably underlies the Perkins Bluff Member (new name) of the Rhems with sharp, 

erosional contact. Thickness is 37 ft at the composite type section and 

135 ft in the Clubhouse Crossroads corehole Number 1. Age is Paleocene (late Danian; middle Midwayan) based on ostracodes and pollen. 

Browns Pond Formation 

Early Cambrian 

New York 

New England province 

Rowley, D.B., Kidd, W.S.F., and Delano, L.L., 1979, Detailed stratigraphic and 

structural features of the Giddings Brook slice of the Taconic allochthon in the 

Granville area, in Friedman, G.M., ed., Guidebook: New England Intercollegiate 

Geological Conference, 71st Annual Meeting, p. 186-242. 

Type locality: Along Holcombville Road near Browns Pond, at the 

Granville-Thorn Hill 7.5-minute quadrangle boundary, Washington 

County, N.Y. (Jacobi, 19'77). 

The Browns Pond Formation, informally named by Jacobi (1977) and 

here described, is in the Giddings Brook slice of the Taconic allochthon 

in the Granville area, N e~w York. Consists of a heterogeneous assemblage of lithologic types, including limestone, limestone conglomerate, 
46 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

limestone breccia, quartz wacke, dolomitic calcarenite, and quartz 

arenite in a matrix of black finely cleaved, fissile slate. The informal 

Mudd Pond quartzite, a distinctive lithologic marker, is found in the 

lower part of the Browns Pond. Sharply overlies the Truth ville Slate or 

Formation (new name) where the color changes from gray-green to 

black; gradationally underlies the Mettawee Slate. Thickness is typically 80 m but ranges from 25 to 130 m. Age is Early Cambrian based on 

fossils. [Although this name has not been formally proposed, it is 

included here because of its continued usage.] 

Bruggers Formation 

Middle Ordovician (Whiterock or Chazyan) 

Michigan 

Michigan basin 

Fisher, J.H., and Barratt, M.W., 1985, Exploration in the Ordovician of central Michigan 

basin: American Association of Petroleum Geologists Bulletin, v. 69, no. 12, 

p. 2065--1076. 

Type section: JEM Bruggers 3-7 well, depth interval10,152-11,322 ft, 

sec. 7, T. 24 N., R. 6 W., Missaukee County, Mich. 

The Bruggers Formation, here named, occurs in the subsurface of 

the central Michigan basin. Consists of clear to white, massive, partly 

crossbedded, bioturbated, clean quartz sandstone that has silica 

cement. Porosity indicates a potential for significant gas production. 

Gradationally overlies the Foster Formation (new name)-the contact 

arbitrarily is placed below the lowest thick sandstone; unconformably 

underlies thin, lenticular interbeds of dolostone, limestone, and sandstone, which are here termed lower Glenwood because they underlie 

typical Glenwood Formation. Thickness is 1,170 ft at the type section. 

Age is Middle Ordovician (Whiterock or Chazyan) based on conodonts. 

Bryan Meadow Granodiorite 

late Cretaceous 

California 

Sierra Nevada province 

John, D.A., Armin, R.A., and Moore, W.J., Quaternary geology by J.C. Dohrenwend, 

1981, Geologic map of the Freel and Dardanelles further planning areas, Alpine and El 

Dorado Counties, California: U.S. Geological Survey Miscellaneous Field Studies Map 

MF-1322-A, scale 1:62,500. 

Type locality: Exposures north of Elbert Lake, sec. 19, T. 11 N., R. 18 

E., El Dorado County, Calif. [Named for Bryan Meadow, sec. 24, 

T. 11 N., R. 17 E.] 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 47 

The Bryan Meadow Granodiorite, named informally by Loomis 

(1981) and here named, occurs in the central Sierra Nevada of California. Consists of light-gray medium-grained, locally porphyritic hornblende biotite granodiorite and potassium feldspar phenocrysts. 

Intrudes the Echo Lake Granodiorite, Burnside Lake Adamellite, 

informal Lovers Leap granodiorite of Loomis (1981), Freel Peak Granodiorite (new name), and quartz diorite of Jobs Canyon. Age is Late 

Cretaceous based on a potassium-argon age of 87 Ma. 

Buck Creek Quarry Member of the Scotch Grove Formation 

Early Silurian (Wenlockian) 

Iowa 

Iowa shelf 

Johnson, M.E., 1983, New member names for the Lower Silurian Hopkinton Dolomite of 

eastern Iowa: Iowa Academy of Science Proceedings, v. 90, no. 1, p. 13-18. 

Type section: Buck CreE~k quarry, east edge of the village of Buck 

Creek, NE1/4NW1/4 sec. 20, T. 87 N., R. 4 W., Delaware County, Iowa. 

Previously divided on the basis of paleontologic units, the Hopkinton 

Dolomite is here divided into lithologic members to facilitate interregional correlations based on sea-level curves. Rocks formerly called the 

Pentameroides Beds, as well as the problematical Goniophyllum and 

Callipentamerus Beds, of the Hopkinton, are here named the Buck 

Creek Quarry Member, the uppermost member of the Hopkinton 

Dolomite in eastern Iowa. Consists of mottled-gray to light-brown 

thick-bedded to massive, finely crystalline dolomite containing numerous white chert horizons. The brachiopod Pentameroides is abundant 

throughout the member. Overlies the Welton Member (new name); 

underlies the Gower Fornmtion. Thickness at the type section is 16.5 m. 

Age is Early Silurian (Wenlockian). 

Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River fault zone and 

the structural and stratigraphic framework of eastern Iowa: Iowa Geological Survey 

Technical Information Series 13, 126 p. 

The Johns Creek Quarry, Welton, and Buck Creek Quarry Members, all new names of Johnson (1983), are here reassigned from the 

upper part of the Hopkinton Dolomite to the lower part of the Scotch 

Grove Formation (new name), a unit defined between the Hopkinton 

and the Gower Formation, for the purpose of preserving the original 

definitions of these units. Underlies and extends laterally into the Fawn 

Creek, Waubeek, and Palisades-Kepler Members (all new names) of the 

Scotch Grove. Age is Early Silurian (Wenlockian). 
48 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Buck Mountain Shut-ins Formation of the St. Francois 

Mountains Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: SEl/4 sec. 33, T. 34 N., R. 3 E., St. Francois Mountains, 

Ironton quadrangle, Iron County, Mo. Named for Buck Mountain 

Shut-ins, Iron County. 

The Buck Mountain andesite flows and tuffs of Anderson (1962), the 

tuffs of Mill Creek and Lake Springs, and Unit A, the base of the tuff of 

Stouts Creek of Anderson (1970), are here named the Buck Mountain 

Shut-ins Formation in the western St. Francois Mountains, Mo. Consists of black andesitic lava flows containing white plagioclase phenocrysts interbedded with rhyolitic air-fall tuff and ash-flow tuff. Overlies 

the Pond Ridge Rhyolite (new name); underlies the Ironton Rhyolite 

(new name). Thickness ranges from 80 to 1,000 m. Age is Middle 

Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, inKisvarsanyi, E.B., ed., StudiesinPrecambriangeologyof 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Buck Mountain Shut-ins Formation. 

Burleigh Hill Member of the Rochester Shale 

Middle Silurian (Wenlockian) 

Ontario, New York 

Appalachian basin 

Brett, C.E., 1983, Stratigraphy and facies relationships of the Silurian Rochester Shale 

(Wenlockian; Clinton Group) in New York State and Ontario: Rochester Academy of 

Science Proceedings, Centennial Colloquium Issue, v. 15, no. 2, p. 118-141. 

Type locality: Road cuts on both sides of Burleigh Hill Drive, Thorold, 

Ontario, Canada. 

The Burleigh Hill Member of the Rochester Shale, here named, is in 

the area from Grimsby, Ontario, Canada, to Lockport, N.Y. Consists of 

sparsely fosssiliferous gray, weathering to white, platy, well-laminated 

shale containing thin micritic limestone interbeds. Comprises the upper 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 49 

calcareous portion of the Rochester Shale and sharply overlies the 

bryozoa beds or unitE of the Lewiston Member (new name); gradationally underlies the DeCew Dolostone or grades laterally into the 

transitional Gates Member (of Chadwick, 1918) of the Rochester in 

Moore County, N.Y. Thickness is 11.2 m at the type locality. Age is 

Middle Silurian (Wenlockian). 

Butlers Bluff Member of the Nassawadox Formation 

Pleistocene 

Virginia 

Atlantic Coast basin 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of uppermost Cenozoic 

deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological 

Survey Professional Paper 1067-G, 53 p. 

Type section: ChesapeakE:~ Bay cliffs at Butlers Bluff between Picketts 

Harbor and Penn Central Railroad ferry landing, southern tip of 

Delmarva Peninsula, Northampton County, Va. Principal reference 

section: Borehole Ch-11, Nassawadox Formation type section. 

The Butlers Bluff Member is here named the middle member of the 

Nassawadox Formation (new name) in the southern Delmarva upland in 

Virginia. Consists of palt~-gray to yellowish-gray fossiliferous, fine to 

coarse, pebbly, clean, crossbedded sand. Conformably to disconformably overlies the Stumptown Member (new name) of the Nassawadox; 

extends westward in the subsurface beneath the Franktown plain 

where it conformably to disconformably underlies the Occohannock 

Member (new name) of the Nassawadox; forms the upper part of the 

Nassawadox in the southern Delmarva upland. May be equivalent in 

age to or may be truncated by the Joynes Neck Sand (new name). 

Thickness at the type section ranges from 25 to 80 ft. Age is Pleistocene. 

Calispell Lake Member of the Tiger Formation 

Eocene, Oligocene, Miocene 

Washington 

Northern Cascade Range-Okanogan province 

Gager, B.R., 1983, Stratigraphy of the Tiger Formation, northeastern Washington: 

Northwest Geology, v. 12, p. 25-41. 

Type section: Exposures in north-facing roadcut, NElf4SEl/4 sec. 2, 

T. 32 N., R. 42 E., Pend Oreille County, Wash. Reference locality: 

Exposures along the West Calispell Lake Road, SWl/4SWl/4 sec. 1 and 

Wl/2NWl/4 sec. 12, T. 32 N., R. 42 E., Pend Oreille County. 

The Calispell Lake l\1[ember, here named, is in the revised Tiger 

Formation in the Cusick region, northeastern Washington. Consists 

of polymictic conglomerate interbedded with rippled and laminated 
50 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

fine-grained sandstone, siltstone, and clay. Conformably and unconformably overlies the Winchester Creek Member (new name) of the 

Tiger. Correlates with the Jared Member (new name) and records 

erosion of older Tiger strata. Thickness is 350 m. Age ranges from early 

middle Eocene, based on inclusions of late early to early middle Eocene 

volcanic rock clasts, through middle Miocene based on middle Miocene 

regional faults that bound the Tiger Formation, although the age 

determination of middle Miocene is less definite. 

Camp Creek Formation of the Atlanta Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Roadcut outcrops along the Fairburn-Jonesboro Road 

(Georgia Highway 138) on both sides of Camp Creek, Riverdale 

7.5-minute quadrangle, Clayton County, Ga. 

The Camp Creek Formation, here named, is the youngest unit of the 

Atlanta Group (new name) in the Newnan-Tucker synform near 

Atlanta, Ga. Consists of massive granite gneisses inter layered with thin 

fine-grained, dark-green hornblende-plagioclase amphibolites. Gradationally overlies the Big Cotton Indian Formation (new name) of the 

Atlanta; sharply and conformably overlies the Clarkston and Intrenchment Creek Formations (new names) of the Atlanta. Is intruded by the 

Union City Complex (new name) and Palmetto Granite. Thickness 

ranges from 600 to 3,000 m. Age is Late Proterozoic and (or) early 

Paleozoic. 

Canada Pilares Member of the Zia Sand 

Miocene (Hemingfordian) 

New Mexico 

San Juan basin 

Gawne, C.E., 1981, Sedimentology and stratigraphy of the Miocene Zia Sand of New 

Mexico: Summary: Geological Society of America Bulletin, v. 92, no. 12, pt. I, 

p. 999--1007. 

Type section: North side of Canada Pilares, sec. 12, T. 12 N., R. 1 W., 

and sec. 7, T. 12 N., R. 1 E., Sky Village and Sky Village SE 7.5-minute 

quadrangles, Sandoval County, N. Mex. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 51 

The Canada Pilares M:ember, here named, is the upper member of 

the Zia Sand in the San Juan basin, New Mexico. Consists of interbedded red clay and pink sandstone and represents a flood-plain deposit. 

Unconformably overlies the reddish silt, sand, and clay of the Chamisa 

Mesa Member of the Zia; underlies pink sand of beds equivalent to the 

Pojoaque Member of the 'fesuque Formation. Thickness is 29 m at the 

type section. Age is Miocene (early Hemingfordian). 

Cando Formation of the Coleharbor Group 

Pleistocene (pre-Wisconsinan or Wisconsinan) 

North Dakota 

Williston basin 

Bluemle, J.P., 1984, Geology of'rowner County, North Dakota: North Dakota Geological 

Survey Bulletin 79, pt. I, p. 1-44. 

Type locality: None designated. Named for the town of Cando, Towner 

County, N. Dak. 

The Cando Formation of the Coleharbor Group, here named, was 

informally named by Howard Hobbs in an unpublished study of the 

glacial stratigraphy of northeastern North Dakota. Is the lowermost of 

five glacial till formations representing separate advances of glacial ice 

in Towner County and is widely preserved in the subsurface. Consists 

of till; stratified silt, sand, and gravel; and shale breccia. Is olive gray 

where unoxidized and bu1i to olive brown where oxidized. U nconformably overlies the Cretaceous Pierre Formation or older Pleistocene 

glacial sediments; underlies the Vang Formation (new name) or the 

Gardar and Dahlen Formations, all of the Coleharbor. Thickness of the 

till is less than 20 ft. Age is Pleistocene (pre- or early Wisconsinan). 

Canyon Creek Drift 

Pleistocene 

Washington 

Western Columbia basin 

Mundorff, M.J., 1984, Glaciation in the lower Lewis River basin, southwestern Cascade 

Range, Washington: Northwt:!st Science, v. 58, no. 4, p. 269-281. 

Type area: Canyon Creek valley, Clark County, Wash. 

Drift and till deposits at altitudes ranging down to about 460 m in the 

valleys of Canyon Creek and Siouxon Creek and their tributaries, Clark 

County, Wash., are here named the Canyon Creek Drift. Consists of 

moraine and cobbly and bouldery till that has a gray sandy and clayey 

matrix. Probably represents an early event during the Fraser glaciation. Age is late Pleistoc1ene (60 ka)-much younger than the Amboy 

Drift (new name). 
52 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Canyon Range Formation 

Cretaceous and Tertiary 

Utah 

Great Basin province 

Holladay, J. C., 1984, Geology of the northern Canyon Range, Millard and Juab Counties, 

Utah: Brigham Young University Geology Studies, v. 31, pt. 1, p. 1-28. 

Type section: Spur north of Cow Canyon extending from N1/2SWlf4 sec. 

24, T. 16 S., R. 2 W., west into unsurveyed Fishlake National Forest, 

northern Canyon Range, Juab County, Utah. 

Rocks formerly assigned to the Indianola Group by Christiansen 

(1952), and later called the informal Canyon Range formation by Stolle 

(1978), are here named the Canyon Range Formation and are subdivided into informal lower, middle, and upper members, as defined by 

Christiansen (1952). The lower member, equivalent to the lower part of 

Stolle's unit A, consists of coarse conglomerate that has Paleozoic 

limestone clasts in a red matrix, and ranges from 265 to 414 m in 

thickness. The middle member, equivalent to the upper part of Stolle's 

unit A, consists of a resistant quartzite clast conglomerate that has a red 

sand matrix, and ranges from 125 to 600 m in thickness. The upper 

member, equivalent to Stolle's unit B, consists of more than 1,200 m of 

cobble and pebble conglomerate, coarse sandstone, siltstone, shale, and 

nonmarine limestone. Unconformably overlies Late(?) Cambrian carbonates; unconformably underlies the Tertiary red beds of Wide Canyon. Age is Cretaceous and Tertiary. 

Carruthers Coal Member of the Floris Formation of the 

Cherokee Group of the Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Road cut in the NWlf4NWlf4SElf4 sec. 3, T. 73 N., 

R. 20 W., Lucas County, Iowa. Named for Carruthers Creek in 

northeastern Lucas County. 

The uppermost coal of the Floris Formation (new name) of the 

Cherokee Group is here named the Carruthers Coal Member. Overlies 

mudstone of the Floris; underlies dark-gray clay shale containing 

brachiopods and pelecypods. Has been correlated with the Wiley coal of 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 53 

Illinois, but an unnamed coal below the Carruthers is probably equivalent to the Wiley; the Carruthers may instead be equivalent to the 

Greenbush-Dekovan coals of Illinois. Thickness at the type section is 1.4 

ft and ranges from a smut to 2.8 ft. Age is Middle Pennsylvanian (early 

Desmoinesian). 

Carson Desert Formation 

Pleistocene and Holocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type area: Carson Desert, Churchill County, Nev. 

Subunits: Upsal Hogback Bed, Soda Lake Bed. 

The Carson Desert Formation, here named, comprises the deposits 

of two vents in the Carson Desert northwest of Fallon in the Lake 

Lahontan area, Nevada. The older vent, U psal Hogback, consists of at 

least five cinder cones or tuff rings, and the younger vent, Soda Lake, 

is a classic tuff ring that has a lake in its center. Tephra from these vents 

are named the Upsal Hogback and Soda Lake Beds (new names). Age 

is Pleistocene and Holocene, 35 to 6 ka. 

Carson Sink Bed of the Mono Basin Formation 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Measured section 3 of Morrison (1964), west bank of 

Carson River at the south edge of Carson Sink, NElf4NWlf4 sec. 30, 

T. 21 N., R. 30 E., Churchill County, Nev. 

The Carson Sink Bed, here named, is found as an ashy parting in the 

Mono Basin Formation (new name) in the Carson Desert of the Lake 

Lahontan area, Nevada. Tephra contains glass-encased biotite phenocrysts and is similar to the Salt Wells Member (new name) of the Mono 

Basin Formation but is much older. Interfingers with the lower member 

of the Sehoo Formation. Overlies the Pelican Island Bed (new name) of 

the Pyramid Lake Member (new name) of the Mount Mazama Formation and the Marble Bluff Bed (new name); underlies the Timber Lake 

Bed (new name) of the Pyramid Lake. Age is Pleistocene, 35 to 11.5 ka. 
54 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Carthage Member of the Tres Hermanos Formation 

late Cretaceous (Turonian) 

New Mexico 

Orogrande basin 

Hook, S.C., Molenaar, C.M., and Cobban, W.A., 1983, Stratigraphy and revision of 

nomenclature of upper Cenomanian to Turonian (Upper Cretaceous) rocks of westcentral New Mexico: New Mexico Bureau of Mines and Mineral Resources Circular 

185, p. 7-28. 

Type section: SElf4SElf4 sec. 8 and NElf4NElf4 sec. 17, T. 5 S., R. 2 E., 

San Antonio quadrangle, Socorro County, N. Mex. Named for the town 

of Carthage, 16 mi southeast of Socorro. 

The Carthage Member, here named, is the middle member of the 

Tres Hermanos Formation, which is raised in stratigraphic rank in the 

Orogrande basin, New Mexico. Consists of gray to buff fine- to very 

fine grained, calcareous sandstone and dark-gray partly carbonaceous 

shale and siltstone. Sandstones are paludal-lacustrine or crevasse-splay 

bay-fill types, deposited on a broad, low-relief coastal or delta plain. 

Overlies the Atarque Sandstone Member (formerly assigned to the 

Mesaverde Formation) and underlies the Fite Ranch Sandstone Member (new name), both of the Tres Hermanos. Intertongues with the 

Mancos Shale. Thickness at the type section is 116ft and ranges from 

100 to 225 ft. Age is Late Cretaceous (late middle and earliest late 

Turonian) based on the ages of underlying and overlying rock. 

Carvers Gap Granulite Gneiss 

Middle Proterozoic 

North Carolina, Tennessee 

Piedmont-Blue Ridge province 

Gulley, G.L., 1985, A Proterozoic granulite-facies terrane on Roan Mountain, western 

Blue Ridge belt, North Carolina-Tennessee: Geological Society of America Bulletin, 

v. 96, no. 11, p. 1428-1439. 

Type locality: Exposures along an access road at its intersection with 

Tennessee State Highway 143 and North Carolina State Highway 261 at 

Carvers Gap, Carvers Gap 7.5-minute quadrangle, Mitchell County, 

N.C. 

The Carvers Gap Granulite Gneiss is here named for outcrops at 

Carvers Gap on Roan Mountain in the Elk River massif in the Blue 

Ridge of North Carolina and Tennessee. Consists of four intergradational units: layered granulite gneiss, massive granulite gneiss, layered 

amphibolite gneiss, and nonlayered amphibolite gneiss as well as 

granitoid segregations and pyroxenite nodules. Is intruded by dikes of 

Late Proterozoic Bakersville Gabbro. Age is Middle Proterozoic based 

on rubidium-strontium ages. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 55 

Cazier Canyon Agglomerate 

Oligocene 

Utah 

Great Basin province 

Meibos, L.C., 1983, Structure and stratigraphy of the Nephi NW 7.5-minute quadrangle, 

Juab County, Utah: Brigham Young University Geology Studies, v. 30, pt. 1, p. 37-58. 

Type section: Exposures in Cazier Canyon, NEl/4 sec. 23, T. 12 S., 

R. 1 W., Nephi NW 7.5-minute quadrangle, Juab County, Utah. 

The Cazier Canyon Agglomerate, here named, is in the Great Basin 

province, Utah. Consists of dark-red and light- to grayish-pink angular 

to subangular, poorly sorted, poorly bedded, volcanic clasts of andesite 

and latite and minor amounts of quartzite clasts. Forms steep ledges 

and cliffs. Unconformably overlies the Copperopolis Latite; underlies 

Quaternary alluvium or colluvium. Thickness is 230 m at the type 

section. Age is Oligocene. 

Cedar Bluff Rhyolite of the St. Francois Mountains Volcanic 

Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: NE1f4NW1f4 sec. 3, T. 33 N., R. 3 E., western St. Francois 

Mountains, Ironton quadrangle, Iron County, Mo. Named for Cedar 

Bluff School, near exposures 2 mi west of Ironton. 

Rocks called Cedar Bluff rhyolite and undifferentiated felsite by 

Anderson (1962, 1970) are here named the Cedar Bluff Rhyolite in the 

western St. Francois Mountains, Mo. Consists of brownish-maroon to 

grayish ash-flow tuff containing white plagioclase phenocrysts. Overlies 

the Shepherd Mountain Rhyolite (new name); underlies the Pond Ridge 

Rhyolite (new name). Thickness is 580 m. Age is Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E. B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Cedar Bluff Rhyolite. 
56 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Cedar Lake Quartzite Member of the Mud Creek Formation 

of the New Georgia Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Abrams, C. E., and McConnell, K.I., 1981, Stratigraphy of the area around the AustellFrolona antiform; west-central Georgia, in Wigley, P.B., ed., Latest thinking on the 

stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 55-67. 

Type locality: Exposures at Cedar Lake, northwest of Winston, Winston 7.5-minute quadrangle, Douglas County, Ga. 

The Cedar Lake Quartzite Member of the Mud Creek Formation 

(new name) of the New Georgia Group (new name), here named, is in 

the Villa Rica antiform on the northwest flank of the Austell-Frolona 

antiform in west-central Georgia. Consists of quartzite interlayered 

with amphibolite as well as layers and disseminated grains of magnetite 

and specular hematite representing a metamorphosed banded iron 

formation. Thickness ranges from 1 to 4 m. Interfingers with the Villa 

Rica Gneiss Member (new name) of the Mud Creek. Grades into the 

stratigraphically overlying but structurally underlying Andy Mountain 

Formation (new name) and Bill Arp Formation (new name) of the 

informal Roosterville group. Age is Proterozoic(?). 

McConnell, K. I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Age of the New Georgia Group is Late Proterozoic and (or) early 

Paleozoic. 

Cereza Peak Shale Member of the Peace Valley Formation of 

the Ridge Basin Group 

Miocene 

California 

Los Angeles basin 

Link, M.H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J.C., and Link, M.H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5-12. 

Type section: Exposure at the base of Cherry Peak, east of California 

Highway 99, about 17 km north of Castaic, Los Angeles County, Calif. 

Cereza is Spanish for cherry and is used because the name Cherry Peak 

is preoccupied as a stratigraphic name. 

The Cereza Peak Shale Member, here named, is in the Peace Valley 

Formation, redefined, of the Ridge Basin Group in the central RidgE: 

basin, Los Angeles County, Calif., where clastic tongues of the Ridgr. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 57 

Route Formation divide the Peace Valley into five members. Consists of 

dark-gray shale and blue-gray mudstone containing minor amounts of 

sandstone interbeds as well as plant, ostracode, and fish fossils. A floral 

assemblage from the Cereza Peak is representative of a semiarid to 

subhumid climate. Lateral extent of the unit is 5,540 m. Interfingers 

with the Ridge Route Formation undivided to the northeast and the 

Violin Breccia to the southwest. Conformably overlies the Frenchman 

Flat Sandstone Member (new name) and conformably underlies the Piru 

Gorge Sandstone Member, redefined, both of the Ridge Route. Thickness at the type section is 914 m and attains 940 m. Age is late Miocene 

based on fossils. 

Chandler Bridge Formation 

Oligocene (Chattian) 

South Carolina 

Atlantic Coast basin 

Sanders, A.E., Weems, R.E., and Lemon, E.M., Jr., 1982, Chandler Bridge Formation-A new Oligocene stratigraphic unit in the lower coastal plain of South Carolina: 

U.S. Geological Survey Bulletin 1529-H, p. H105-H124. 

Type section: Charleston Museum paleontologic excavation site 0. 7 km 

northwest of the confluence of Chandler Bridge Creek and Eagle Creek, 

Stallsville quadrangle, Dorchester County, S.C. 

A thin sequence of noncalcareous arenaceous beds in Dorchester, 

Berkeley, and Charleston Counties, S.C., is here named the Chandler 

Bridge Formation. Includes three conformable beds: a basal yellowishbrown clayey, quartz-phosphate sand; a middle gray clayey, poorly 

compacted, quartz-phosphate sand; and an upper gray clayey, wellcompacted, quartz-phosphate sand. Disconformably overlies the Ashley 

Member of the Cooper Formation; disconformably underlies surficial 

Pleistocene deposits. Thickness is 5 m. Age is late Oligocene (Chattian) 

based on cetacean fauna. 

Chapel Branch Member of the Santee limestone 

Eocene 

South Carolina 

Atlantic Coast basin 

Powell, R.J., 1984, Lithostratigraphy, depositional environment, and sequence framework of the middle Eocene Santee Limestone, South Carolina Coastal Plain: Southeastern Geology, v. 25, no. 2, p. 79-100. 

Type section: South shore of Lake Marion, 1. 5 mi northwest of U.S. 

Highway 301 crossing, Santee State Park; access by unnumbered paved 

road, 1.5 mi east of crossing of County Roads 105 and 82, Orangeburg 

County, S.C. Named for nearby stream called Chapel Branch. 
58 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Chapel Branch Member of the Santee Limestone, a foraminiferal biomicrite lithofacies, is here named for outcrops along the south 

shore of Lake Marion in Orangeburg and Calhoun Counties, S.C. 

Consists of yellowish-gray homogeneous matrix-supported foraminifera, ostracodes, echinoids, and mollusks and has traces of bryozoa. 

Is laterally equivalent to other lithofacies in the Santee; grades down-dip 

into bryozoan biosparrudite-biomicrudite facies. Stratigraphically 

underlies the Caw Caw Member of the Santee, a molluskan-mold 

mudstone facies. Thickness at the type section is 7.5 ft. Age is middle 

Eocene. 

Chatsworth Formation 

Late Cretaceous (Campanian to Maastrichtian) 

California 

Los Angeles basin, Ventura basin 

Colburn, I.P., Saul, L.E.R., and Almgren, A.A., 1981, The Chatsworth Formation: A 

new formation name for the Upper Cretaceous strata of the Simi Hills, California, in 

Link, M.H., Squires, R.L., and Colburn, I.P., eds., Simi Hills Cretaceous turbidites, 

southern California: Society of Economic Paleontologists and Mineralogists, Pacific 

Section, p. 9-16. 

Type section: Exposures along Woolsey Canyon Road and Black Canyon Road from Valley Circle Boulevard to the base of the Simi 

Conglomerate in Santa Susana Knolls, eastern Simi Hills, Los Angeles 

and Ventura Counties, Calif. Named for the community of Chatsworth, 

Los Angeles County. 

Beds in the Simi Hills previously referred to as the Chico Formation, a name originally applied to all the Upper Cretaceous strata in 

California, are here named the Chatsworth Formation. Consists of four 

principal lithosomes composed of turbidite sandstone and interbedded 

hemipelagic mudstone described by Colburn (1973) as Descriptive 

Facies I, II, III, and IV. Deposition under shallow, littoral conditions is 

suggested by meager faunas. Base of the unit is not exposed; older beds 

unconformably underlie Miocene strata; younger beds concordantly or 

unconformably underlie the lower(?) Tertiary Simi Conglomerate. 

Thickness is more than 1,830 m. Age is Late Cretaceous (middle 

Campanian to early Maastrichtian) based on mollusks. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 59 

Chavez Canyon Member of the Spears Formation of the Datil 

Group 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: Chavez Canyon, 17 mi northeast of Datil, 0.6 mi north of 

Chavez well, Sl/2 sec. 27, T. 2 N., R. 8 W., northwest Gallinas 

Mountains, Dog Springs 7.5-minute quadrangle, SocoiTo County, 

N.Mex. 

The Chavez Canyon Member, here named, is the middle member of 

the Spears Formation of the Datil Group in the northwest Gallinas 

Mountains, southwestern New Mexico. Consists of a lower feldspathic 

sandstone unit and an overlying volcaniclastic conglomerate unit containing a few debris flows. Overlies the Dog Springs Member (new 

name) of the Spears Formation; underlies the Rock House Canyon Tuff 

(new name) of the Datil Group. Is split locally into two parts by the 

interbedded Datil Well Tuff (new name) of the Datil Group. Thickness 

at the type section is 416ft and attains 1,000 ft. Age is Oligocene. 

Cheeneetnuk Limestone 

Early(?) and Middle Devonian 

Alaska 

Holitna basin 

Blodgett, R.B., and Gilbert, W.G., 1983, The Cheeneetnuk Limestone, a new Early(?) to 

Middle Devonian formation in the McGrath A-4 and A-5 quadrangles, west-central 

Alaska: Alaska Division of Geological and Geophysical Surveys, Professional Report 

85, p. 1-6. 

Type section: Exposures along the northwest bank of the southwestflowing Cheeneetnuk River, sees. 16 and 21, T. 23 N., R. 32 W., Seward 

Meridian, McGrath A-5 quadrangle, Alaska. 

The Cheeneetnuk Limestone, here named, is equivalent to unit 

mDlc of Gilbert (1981) and forms the uppermost horizon within an 

Ordovician to Middle Devonian carbonate-platform sequence exposed 

on the north side of the Farewell fault in the McGrath A-4 and A-5 

quadrangles, Alaska. Consists of dark-gray well-bedded, argillaceous, 
60 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

micritic limestone. Conformably overlies unnamed dolomite of unit lDd 

of Gilbert (1981); conformably underlies unnamed argillite and chert of 

unit uPzac of Gilbert (1981). Thickness is 457 m at the type section. 

Fossils in the upper part of the formation are early Middle Devonian 

(Eifelian); the lack of fossils in the lower part makes a positive age 

determination impossible, but the relative total thickness suggests that 

the base of the formation extends into the Lower Devonian. 

Chenoweth Formation of the Dalles Group 

Miocene and Pliocene(?) 

Oregon 

Eastern Columbia basin 

Farooqui, S.M., Beaulieu, J.D., Bunker, R.C., Stensland, D.E., and Thoms, R.E., 1981, 

Dalles Group: Neogene formations overlying the Columbia River Basalt Group in 

north-central Oregon: Oregon Geology, v. 43, no. 10, p. 131-140. 

Reference sections: Badger Creek and Chenoweth Rim section, NEl/4 

sec. 30, T. 2 N., R. 13 E.; Government Flat section, NEl/4 sec. 10, 

T. 1 N., R. 12 E., Wasco County, Oreg. Named for Chenoweth Creek, 

west of The Dalles, T. 2 N., R. 13 E. 

Volcaniclastic debris fan deposits consisting of interbedded agglomerate, tuff breccia, tuff, lahars, and clastics in The Dalles basin are here 

named the Chenoweth Formation of the Dalles Group. Overlies the 

Priest Rapids and Frenchman Springs Members of the Wanapum 

Basalt; underlies Quaternary rocks. Age is late Miocene and early 

Pliocene(?) based on potassium-argon and vertebrate fossil dates. 

Chestatee Member of the Canton Formation 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

German, J.M., 1985, The geology of the northeastern portion of the Dahlonega gold belt: 

Georgia Geologic Survey Bulletin 100, p. 1-41. 

Type locality: Exposures along Chestatee River in Murrayville quadrangle, Lumpkin County, Ga. 

The Chestatee Member of the Canton Formation, here named, is in 

the Dahlonega area in Georgia and was previously mapped as the Roan 

Gneiss by Keith (1909). Consists of amphibolite, hornblende-plagioclase 

gneiss, muscovite-biotite-quartz-plagioclase gneiss, and muscovitepyrite-plagioclase-quartz gneiss. Lies in sharp contact with metagraywacke of the Helen Member (new name) of the Canton to the southeast 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 61 

and in fault contact with biotite-quartz schist of the Palmer Creek 

Member (new name) of the Canton to the northwest. Age is Late 

Proterozoic and (or) early Paleozoic. 

Chestnut Hill Formation 

Late Proterozoic 

Pennsylvania, New Jersey 

Appalachian basin 

Drake, A.A., Jr., 1984, The Reading Prong of New Jersey and eastern Pennsylvania-An 

appraisal of rock relations and chemistry of a major Proterozoic terrane in the 

Appalachians: Geological Society of America Special Paper 194, p. 75--126. 

Type locality: Exposures on Chestnut Hill along the west bank of the 

Delaware River, Easton 7.5-minute quadrangle, Northampton County, 

Pa. 

The Chestnut Hill Formation, here named, is a poorly exposed 

sequence of arkose, ferruginous quartzite, quartzite, conglomerate, 

metarhyolite, and metasaprolite along the north border of the Reading 

Prong on Chestnut Hill, Pa., and Marble Mountain, N.J. Was previously included in the Pickering Gneiss by Bayley (1941) and in the 

Moravian Heights Formation by Fraser (1939). Overlies other metasedimentary and metavolcanic rocks of the Reading Prong and differs from 

them in that bedding can be recognized and it is of lower metamorphic 

grade. Age is probably Late Proterozoic. 

Chicken Ridge Sandstone Member of the Kanawha Formation 

Middle Pennsylvanian 

Virginia 

Appalachian basin 

Englund, K.J., 1981, Geologic map of the Jewell Ridge quadrangle, Virginia: U.S. 

Geological Survey Geologic Quadrangle Map GQ-1550, scale 1:24,000. 

Type locality: Exposures on State Route 636 at the head of Jewell 

Branch, Jewell Ridge quadrangle, Buchanan County, southwestern 

Virginia. 

The Chicken Ridge Sandstone Member of the Kanawha Formation, 

here named, is in the Jewell Ridge quadrangle in Buchanan and 

Tazewell Counties, Va. Occurs near the base of the Kanawha and 

underlies 4 ft of shale and underclay beneath the Bearwallow coal bed. 

Thickness is 20 ft. Age is Middle Pennsylvanian. 
62 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Chicora Member of the Williamsburg Formation of the Black 

Mingo Group 

Paleocene (Thanetian) 

South Carolina 

Atlantic Coast basin 

Van Nieuwenhuise, D.S., and Colquhoun, D.J., 1982, The Paleocene-lower Eocene Black 

Mingo Group of the east central Coastal Plain of South Carolina: South Carolina 

Geology, v. 26, no. 2, p. 47-67. 

Type section: Outcrops along the south bank of the Santee River just 

downstream from Wilsons Landing, Chicora 7.5-minute quadrangle, 

Berkeley County, S.C. 

The Chicora Member, here named, is the upper member of the 

Williamsburg Formation of the Black Mingo Group in the South 

Carolina Coastal Plain. As revised, the Black Mingo Group includes all 

the strata from the base of the Paleocene to the top of the Ypresian 

Stage of the Eocene and is divided into the Rhems Formation of the 

Danian Stage, the Williamsburg Formation of the Thanetian Stage, and 

unnamed Ypresian strata. [Of the Clubhouse Crossroads corehole 

Number 1, Gohn and others (1978) assigned the entire Paleocene section 

to the Black Mingo Formation, and Gohn and others (1983) named the 

Ypresian strata the Fishburne Formation (new name).] The Chicora 

Member consists of glauconitic, argillaceous, fossiliferous sand and 

indurated mollusk-rich limestone. Gradationally overlies the Lower 

Bridge Member (new name) of the Williamsburg; unconformably underlies unnamed Ypresian strata of the Black Mingo Group. Thickness at 

the type section is 8 ft. Age is late Paleocene (Thanetian). 

Chilton Member of the Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: DePere Site, gravel pit north of Brown County Highway 

X near the top of the Silurian escarpment, southeast corner of sec. 38, 

T. 23 N., R. 20 E., DePere 7.5-minute quadrangle, Brown County, Wis. 

Named for the city of Chilton, Calumet County. 

Following the informal usage of McCartney and Mickelson (1982), 

the Chilton Member of the Kewaunee Formation (new name), here 

named, is on the east side of the Green Bay Lobe in Wisconsin. Consists 

of reddish-brown sand, silt, and clay till. Distinctly overlies the Branch 

River Member (new name) of the Kewaunee or the Horicon Formation 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 63 

(new name); abruptly underlies the Glenmore Member (new name) of 

the Kewaunee or lies at the surface. The contact with the equivalent 

Kirby Lake Member (new name) of the Kewaunee on the west side of 

the Green Bay Lobe is an arbitrarily drawn vertical cutoff at the Fox 

River. Is also equivalent to the Haven Member (new name) and Valders 

Member of the Kewaunee in the Lake Michigan Lobe. Thickness ranges 

from 1 to 3 m. Age is late Pleistocene (late Wisconsinan). 

Chowan River Formation of the Chesapeake Group 

Pliocene 

North Carolina, Virginia 

Atlantic Coast basin 

Blackwelder, B.W., 1981, Stratigraphy of upper Pliocene and lower Pleistocene marine 

and estuarine deposits of northeastern North Carolina: U.S. Geological Survey Bulletin 

1502-B, 16 p. 

Type section: Bluffs on the Chowan River 250 m downstream from 

Colerain Beach, Bertie County, N.C. 

Subunits: Edenhouse Member (North Carolina, Virginia), Colerain 

Beach Member (North Carolina). 

Sand and silt deposits previously mapped as the upper Pliocene 

Chowan River beds of the Yorktown Formation and the upper Pliocene 

part of the Croatan Formation, here abandoned, are here named the 

Chowan River Formation of the Chesapeake Group. Extends north 

from the Pamlico River near Aurora, N.C., to near Norfolk, Va., and 

represents an unconformity bounded late Pliocene marine transgression 

and regression in the Coastal Plain. Consists of marine shelly, silty sand 

and estuarine-laminated and trough-crossbedded clayey, silty sand. Is 

divided into the lower Edenhouse Member (new name) in North 

Carolina and Virginia and the upper Colerain Beach Member (new 

name) in North Carolina. Transitionally to unconformably overlies the 

Morgarts Beach Member of the Yorktown Formation; unconformably 

underlies the James City Formation or sand and gravel deposits 

assigned to the Windsor Formation(?) of Coch (1968). Thickness is 4.2 m 

at the type section. Age is late Pliocene based on corals. 

Chumstick Formation 

Eocene 

Washington 

Northern Cascade Range-Okanogan province 

Gresens, R.L., Naeser, C.W., and Whetten, J.W., 1981, Stratigraphy and age of the 

Chumstick and Wenatchee Formations: Tertiary fluvial and lacustrine rocks, Chiwaukum graben, Washington: Geological Society of America Bulletin, v. 92, no. 5, pt. I, 

p. 233-236; pt. II, p. 841-876. 
64 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Exposures along Eagle Creek beginning at its confluence 

with Chumstick Creek, sec. 31, T. 25 N., R. 18 E., and extending 

northeast to sec. 20, T. 25 N., R. 19 E., north of Leavenworth, Chelan 

County, Wash. 

Subunit: Nahahum Canyon Member. 

Previously called the informal Camas sandstone, an upper sedimentary unit of the Swauk Formation, by Russell (1900), the Chumstick 

Formation is here named following the informal usage of Buza (1976). 

Occurs in the Chiwaukum graben in the central Cascade Range of 

Washington. Consists of whitish to buff-gray crossbedded to massive, 

feldspathic and pebbly sandstone of fluvial origin interbedded with 

conglomerate, shale, and minor amounts of tuff. Fanglomerates occur at 

the base and along the margins. Includes the fine-grained lacustrine 

Nahahum Canyon Member (new name) in the upper part. Lies in the 

Chiwaukum graben and is bounded by the Leavenworth and Entiat 

faults, both active during the deposition of the Chumstick. U nconformably overlies weathered crystalline basement Swakane Biotite Gneiss; 

unconformably underlies the Wenatchee Formation (new name). Thickness at the type section is 5,800 m but is extremely variable elsewhere. 

Age is middle Eocene based on a fission-track age of 45 Ma from zircon 

in tuff. 

Clairmont Formation of the Atlanta Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Exposures at the intersection of Clairmont Road and 

Interstate Highway I-85, Northeast Atlanta 7.5-minute quadrangle, De 

Kalb County, Ga. 

The Clairmont Formation of the Atlanta Group (new name), here 

named, is in the Newnan-Tucker synform near Atlanta, Ga., and 

consists of well-foliated, contorted, porphyroblastic, biotite-plagioclase 

gneiss interlayered with amphibolite. Contacts with the underlying 

Norcross Gneiss (new name) and overlying Wahoo Creek Formation 

(new name), both of the Atlanta, are conformable and gradational. Is in 

sharp contact with the Wolf Creek and Promised Land Formations 

(both new names) of the Atlanta. Correlates with part of the Senoia 

Formation (new name) of the Atlanta. Thickness ranges from 500 to 

1,500 m. Age is late Late Proterozoic and (or) Paleozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 65 

Clarkston Formation of the Atlanta Group 

late Proterozoic and (or) early Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type section: Outcrops along the Georgia Railroad and East Ponce de 

Leon Avenue (Stone Mountain Highway) from Clarkston to Mountain 

Industrial Boulevard, Clarkston, Stone Mountain 7.5-minute quadrangle, Fulton County, Ga. 

Subunits: Fairburn Member, Tar Creek Member. 

The Clarkston Formation of the Atlanta Group (new name) is here 

named. On the northwest limb of the Newnan-Tucker synform near 

Atlanta, Ga., it is divided into the lower Fairburn Member (new name) 

and the upper Tar Creek Member (new name). Consists of interlayered 

purple-pink-weathering muscovite schist and ocher-weathering 

hornblende-plagioclase amphibolite. Overlies the Wahoo Creek Formation or Stonewall Formation (both new names) of the Atlanta with sharp 

and probably conformable contact. Gradationally underlies the Big 

Cotton Indian Formation (new name) of the Atlanta in the northeast; 

elsewhere underlies the Intrenchment Creek Formation and Camp 

Creek Formation (both new names) of the Atlanta with sharp and 

conformable contact. Thickness ranges from 800 to 2,500 m. Age is Late 

Proterozoic and (or) early Paleozoic. 

Cliffland Coal Member of the Kalo Formation of the 

Cherokee Group of the Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and VanDorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Abandoned railroad cut in NEl/4NEl/4SEl/4, sec. 18, 

T. 71 N., R. 12 W., Wapello County, Iowa. Named for the town of 

Cliffland. 

The Cliffland Coal Member, here named, is the upper of two coal 

members of the Kalo Formation (new name) of the Cherokee Group in 

south-central Iowa. At the type section and to the west, consists of two 

coal beds separated by about 15 ft of silty shale. Combined thickness of 

the two beds at the type section is 4. 8 ft. Where a single bed is present, 
66 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

thickness varies from 2 in. to 6.3 ft. Overlies a sequence of thinly 

interbedded shale, siltstone, and sandstone above the Blackoak 

Coal Member (new name). Underlies a similar sequence below the 

Floris Formation (new name). Age is Middle Pennsylvanian (early 

Desmoinesian). 

Cliff Ridge Member of the Tiger Formation 

Eocene, Oligocene, Miocene 

Washington 

Northern Cascade Range-Okanogan province 

Gager, B.R., 1983, Stratigraphy of the Tiger Formation, northeastern Washington: 

Northwest Geology, v. 12, p. 25-41. 

Type section: Exposures along N ofs Creek Road on the south flank of 

Cliff Ridge, SEl/4 sec. 25, T. 34 N., R. 40 E., and SWlf4SWlf4 sec. 30, and 

Nlf2NW1/4 sec. 31, T. 34 N., R. 41 E., Pend Oreille County, Wash. 

The Cliff Ridge Member, here named, is in the revised Tiger 

Formation in the Cliff Ridge region, northeastern Washington. Consists 

of coarse, massive conglomerate composed of greenstone, granite, 

dolomite, and volcanic rock. Boulder conglomerates are common. Overlies Precambrian greenstone and possibly Cretaceous granite, but has 

no stratigraphic relationship to other members of the Tiger Formation. 

Thickness is 400 m at the type section, but may be as much as 1, 700 m. 

Age ranges from early middle Eocene, based on inclusions of late early 

to early middle Eocene volcanic rock clasts, through middle Miocene, 

based on middle Miocene faults that bound the Tiger Formation, 

although the age determination of middle Miocene is less definite. 

Clifton Creek Limestone 

Mississippian 

Tennessee 

Appalachian basin 

Brent, W. B., 1982, Mississippian stratigraphy of Greendale and Newman Ridge synclines 

and Middle Ordovician nomenclature in upper east Tennessee: Tennessee Division of 

Geology Report of Investigations 41, 37 p. 

Type section: Hillside on the east bank of Clifton Creek, 1.8 km 

northeast of Snow Flake, Looneys Gap quadrangle, Hawkins County, 

Tenn. Reference section: 1 km northeast of intersection of Laurel 

Branch Road and State Highway 94, Camelot quadrangle, Hawkins 

County. 

The Clifton Creek Limestone, informally named by Sanders (1952), 

is here named. These Mississippian strata in the Greendale syncline in 

Hawkins and Grainger Counties, Tenn., were previously named the 

Newman Limestone by Hardeman and others (1966) but are isolated 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 67 

from the type Newman Limestone in the Newman Ridge syncline. 

Consists of gray thick-bedded, finely crystalline limestone and finegrained oolitic calcarenite. Sharply overlies the Snow Flake Formation 

(new name); underlies the Gilliam Creek Limestone (new name). 

Correlates, in part, with the St. Louis Limestone. Thickness is 39 m. 

Age is Mississippian. 

Clinton Member of the Walworth Formation 

Pleistocene (Wisconsinan) 

Wisconsin, Illinois 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Road cut and test hole along Highway 15 (BeloitMilwaukee Road), 3.2 km northeast of Clinton, NEl/4SWl/4 sec. 3, 

T. 1 N., R. 14 E., Clinton 7.5-minute quadrangle, Rock County, Wis. 

Named for the village of Clinton. 

The Clinton Member, here named, is the upper member of the 

Walworth Formation (new name), following the informal usage of 

Fricke (1976), in south-central Wisconsin and northern Illinois. Consists 

of pebbly, sandy, yellowish-brown till containing little clay. Sharply to 

gradationally overlies the Allens Grove Member (new name) of the 

Walworth; sharply underlies the Capron Member of the Zenda Formation (new name) or is exposed at the surface in eastern Rock and 

western Walworth Counties, Wis. Thickness ranges from less than 1 m 

to more than 12m. Age is late Pleistocene (early Wisconsinan or older). 

Cloudland Granulite Gneiss 

Middle Proterozoic 

North Carolina, Tennessee 

Piedmont-Blue Ridge province 

Gulley, G.L., Jr., 1985, A Proterozoic granulite-facies terrane on Roan Mountain, western 

Blue Ridge belt, North Carolina-Tennessee: Geological Society of America Bulletin, v. 

96, no. 11, p. 1428-1439. 

Type locality: Exposures near a parking lot off the access road at the 

intersection of Tennessee State Highway 143 and North Carolina State 

Highway 261, from Carvers Gap to the top of Roan Mountain, Bakersville 7.5-minute quadrangle, Mitchell County, N.C. Named for Cloudland resort on Roan Mountain. 

The Cloudland Granulite Gneiss, here named, is on Roan Mountain 

in the Blue Ridge of North Carolina and Tennessee. Consists of 

granulite gneiss characterized by garnet and aluminum silicate as 
68 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

primary granulite-facies minerals. Is intruded by the Bakersville Gabbro. Age is Middle Proterozoic based on rubidium-strontium ages. 

Coal Mine Brook Formation 

Middle Pennsylvanian 

Massachusetts 

New England province 

Goldsmith, Richard, Grew, E.S., Hepburn, J.C., and Robinson, G.R., Jr., 1982, Formation names in the Worcester area, Massachusetts: U.S. Geological Survey Bulletin 

1529-H, p. H43-H56. 

Type locality: Composite of exposures near Franklin and Shrewsbury 

Streets and at the Worcester coal mine on the property of Notre Dame 

Institute, Worcester, Worcester County, Mass. Named for Coal Mine 

Brook, which is near the mine. 

Fossiliferous slate and phyllite and garnetiferous phyllite, arkose, 

and conglomerate at the Worcester coal mine, Worcester, Mass., are 

here named the Coal Mine Brook Formation. Separated by faulting and 

unconformity from the underlying Worcester Formation. Thicknesses 

at the composite type locality are 330 m of phyllite, arkose, and 

conglomerate and 50 m of slate and phyllite. Age is Middle Pennsylvanian based on flora found in the coal. 

Colberg Metavolcanic Rocks of the Phantom Lake 

Metamorphic Suite 

Archean 

Wyoming 

Green River basin 

Karlstrom, K.E., Houston, R.S., Coolidge, C.M., Flurkey, A.J., and Sever, C.K., 1981, 

The geology of Archean and Early Proterozoic terraines of the Medicine Bow 

Mountains, Wyoming, in Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, 

eds., A summary of the geology and uranium potential of Precambrian conglomerates 

in southeastern Wyoming: U.S. Department of Energy National Uranium Resource 

Evaluation, v. 1, pt. 2, p. 197-399. 

Type locality: None designated. Derivation of name not stated. 

A unit here named the Colberg Metavolcanic Rocks of the Phantom 

Lake Metamorphic Suite crops out in large areas of the northern 

Medicine Bow Mountains and in the core of the Arrastre anticline in the 

central Medicine Bow Mountains, Wyo. Consists of a heterogeneous 

assemblage of metabasalt, metatuff, metagraywacke, paraconglomerate, and quartzite. Deposition may have taken place in alluvial or 

submarine channels and fans adjacent to fault scarps. Overlies the Bow 

River Quartzite (new name), underlies the Conical Peak Quartzite (new 

name), both of the Phantom Lake. Thickness ranges from 100m to 2,500 

m. Age is Archean. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 69 

Colerain Beach Member of the Chowan River Formation of the 

Chesapeake Group 

Pliocene 

North Carolina 

Atlantic Coast basin 

Blackwelder, B.W., 1981, Stratigraphy of upper Pliocene and lower Pleistocene marine 

and estuarine deposits of northeastern North Carolina: U.S. Geological Survey Bulletin 

1502-B, 16 p. 

Type section: Bluffs on the Chowan River 250 m downstream from 

Colerain Beach, Bertie County, N.C. 

Upper regressive beds of the Chowan River Formation (new name) 

of the Chesapeake Group in the Coastal Plain of northeastern North 

Carolina are here named the Colerain Beach Member. Consists of 

trough-crossbedded, thickly bedded and thinly laminated sand and silt 

containing lenses of fossils indicative of estuarine deposition. Transitionally to unconformably overlies the Edenhouse Member (new name) 

of the Chowan River; sharply and unconformably underlies sand and 

gravel deposits tentatively assigned to the Windsor Formation(?) of 

Coch (1968). Thickness is 2. 7 m at the type section. Age is late Pliocene 

based on corals. 

Collins Till 

Pleistocene (Wisconsinan) 

New York 

Appalachian basin 

Calkin, P.E., Muller, E.H., and Barnes, J.H., 1982, The Gowanda Hospital Interstadial 

Site, New York: American Journal of Science, v. 282, p. 1110-1142. 

Type section: Gowanda Hospital Section, along the left bank of the 

South Branch, Clear Creek, at the edge of the Gowanda State Hospital 

grounds, west of U.S. Highway 62 and 4 km. north of the village of 

Gowanda, Erie County, N.Y. 

The Collins Till, here named, is in Erie County, N.Y. Consists of 

red, compact, homogeneous, sparsely pebbly, silty clay till separated 

from underlying Devonian shale by a reddish-gray till facies modified by 

assimilated shale. An upper weathered zone, designated the Gowanda 

Paleosol, is overlain by silt, sand, and gravel. Thickness at the type 

section is 2. 7 m. Age is late Pleistocene (early Wisconsinan). 
70 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Comanche Point Member of the Dox Formation of the Unkar 

Group 

Middle Proterozoic 

Arizona 

Plateau sedimentary province 

Stevenson, G.M., and Beus, S.S., 1982, Stratigraphy and depositional setting of the upper 

Precambrian Dox Formation in Grand Canyon: Geological Society of America Bulletin, 

v. 93, no. 2, p. 163-173. 

Type section: Exposures in the bed of an unnamed creek tributary to 

Tanner Canyon, 1.6 km west of Comanche Point, a promontory on the 

southeast side of the Colorado River, eastern Grand Canyon, Vishnu 

Temple quadrangle, Coconino County, Ariz. 

The Comanche Point Member of the Dox Formation of the U nkar 

Group, here named, is in the eastern Grand Canyon, Arizona. Contains 

five laterally continuous marker units, each 3 to 12m thick, consisting 

of white to greenish-white and lavender interbedded sandstone and 

mudstone in an otherwise predominantly red-brown slope-forming 

siltstone that has ripple marks, mudcracks, and salt crystal casts. A 

dolomitic stromatolite bed occurs directly above the lowest marker unit. 

Was deposited as a tidal flat complex. Overlies the Solomon Temple 

Member (new name), and gradationally underlies the Ochoa Point 

Member (new name), both of the Dox Formation. Thickness at the type 

section is 155 m. Age is Middle Proterozoic based on the age of the 

overlying Cardenas Lavas (1.1 Ma). 

Conconully Granodiorite 

Late Cretaceous 

Washington 

Northern Cascade Range-Okanogan province 

Menzer, F.J., Jr., 1983, Metamorphism and plutonism in the central part of the Okanogan 

Range, Washington: Geological Society of America Bulletin, v. 94, no. 4, p. 471-498. 

Type locality: Exposures in the West Fork of Salmon Creek basin 

southwest of Conconully, T. 35 N., R. 24 E., Okanogan County, Wash. 

The Conconully Granodiorite, here named, is a postmetamorphic, 

orthomagmatic pluton of batholithic dimensions in the Okanogan Range, 

Wash. Consists predominantly of granodiorite but composition ranges 

from quartz diorite to quartz monzonite. Is subdivided into three 

mappable phases on the basis of texture and composition: the main 

phase contains plagioclase, quartz, and pinkish potash feldspar, locally 

subporphyritic, and is the most widespread variety of rock; the Mineral 

Hill phase contains potash feldspar megacrysts, as much as 5 em in 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 71 

diameter, and local green hornblende in a main phase-type groundmass; 

the Ritchie Ridge phase is similar to the main phase but is finer grained. 

Weathered nature of the granodiorite distinguishes it from local felsic 

plutonic rocks except for the Pogue Mountain Quartz Monzonite and the 

Leader Mountain Granodioritic Gneiss. Intrudes the Salmon Creek 

Schists and Gneisses, Summit-Frazer Trondhjemitic Gneiss (new 

name), Leader Mountain Granodioritic Gneiss, and Windy Hill Quartz 

Dioritic Orthogneiss (new name). Is intruded by the Leader Lake 

Quartz Monzonite (new name), which may be a later differentiate of the 

same parent magma. Age is Late Cretaceous. 

Conical Peak Quartzite of the Phantom lake Metamorphic 

Suite 

Archean 

Wyoming 

Green River basin 

Karlstrom, K.E., Houston, R.S., Coolidge, C.M., Flurkey, A.J., and Sever, C.K., 1981, 

The geology of Archean and Early Proterozoic terraines of the Medicine Bow 

Mountains, Wyoming, in Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, 

eds., A summary of the geology and uranium potential of Precambrian conglomerates 

in southeastern Wyoming: U.S. Department of Energy National Uranium Resource 

Evaluation, v. 1, pt., 2, p. 197-399. 

Type area: Conical Peak area, northern Medicine Bow Mountains, 

T. 18-19 N., R. 79 W., Carbon County, Wyo. 

The Conical Peak Quartzite of the Phantom Lake Metamorphic 

Suite, here named, is in the core of the Foote Creek synclinorium in the 

northern Medicine Bow Mountains, Wyo. Consists of white, foliated, 

fine-grained muscovitic subarkose and calcareous quartzite. Large-scale 

planar crossbeds and bimodal paleocurrents suggest a shallow marine 

depositional environment. Overlies the Bow River Quartzite (new 

name) and Colberg Metavolcanic Rocks (new name), both of the 

Phantom Lake; unconformably underlies the Magnolia Formation of the 

Deep Lake Group. Exposed stratigraphic thickness is about 800 m. Age 

is Archean. 

Conover Ranch Formation of the Snowcrest Range Group 

late Mississippian (Chesterian) and Early Pennsylvanian (Morrowan) 

Montana 

Montana folded belt province 

Wardlaw, B.R., and Pecora, W.C., 1985, New Mississippian-Pennsylvanian stratigraphic 

units in southwest Montana and adjacent Idaho, in Sando, W.J., ed., Mississippian and 

Pennsylvanian stratigraphy in southwest Montana and adjacent Idaho: U.S. Geological 

Survey Bulletin 1656-B, p. B1-B9. 
72 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Exposure 122 m uphill from the northwest bank of Sheep 

Creek, Conover Ranch, Blacktail Mountains, NE1/4NW1f4 sec. 18, 

T. 9 S., R. 8 W., Gallagher Mountain 7.5-minute quadrangle, Beaverhead County, Mont. 

Rocks previously assigned to the Amsden Formation in southwest 

Montana are here named the Conover Ranch Formation, the upper 

formation of the Snowcrest Range Group (new name), in the Tendoy 

Mountains, Blacktail Mountains, Snowcrest Range, Elkhorn-Boulder 

Mountains, Tobacco Root Range, and parts of the Gravelly Range and 

Pioneer Mountains, Mont. Consists of pale-reddish-brown to palereddish-purple mudstone containing thin-bedded marine limestone, 

calcareous sandstone and siltstone, and, locally, carbonate conglomerate, phosphatic claystone, mottled or nodular calcareous mudstone, and 

recrystallized grainstone. Overlies the Lombard Limestone (new name) 

of the Snowcrest Range Group; underlies and intertongues with the 

Quadrant Sandstone. Is equivalent to part of the Tyler Formation, part 

of the Alaska Bench Limestone of the Amsden Group in central 

Montana, and part of the Bluebird Mountain Formation in east-central 

Idaho. Is laterally equivalent to the uppermost part of the Lombard and 

the lowermost part of the Quadrant. Thickness at the type section is 

30.6 m and ranges from 0 to 33m. Age is commonly Late Mississippian 

(late Chesterian) (Mamet Foraminifer Zone 19, Sando and Bamber 

Coral Zone VI), but is Early Pennsylvanian (early Morrowan) along the 

Jefferson River, where it includes the Mississippian-Pennsylvanian 

boundary. 

Continental Divide Metavolcanic Rocks 

Archean 

Wyoming 

Green River basin 

Flurkey, A.J., Houston, R.S., Karlstrom, K.E., and Kratochvil, T.L., 1981, The geology 

of Archean and Early Proterozoic terranes of the Sierra Madre, Wyoming, in 

Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, eds., A summary of the 

geology and uranium potential of Precambrian conglomerates in southeastern Wyoming: U.S. Department of Energy National Uranium Resource Evaluation, v. 1, pt. 3, 

p. 401-541. 

Type area: Headwaters of South Spring Creek, North Spring Creek, 

and Jack Creek, Sierra Madre, Carbon County, Wyo. Derivation of 

name not stated. 

The Continental Divide Metavolcanic Rocks, here named, are in the 

Sierra Madre, Wyo., and consist of fine-grained amphibolite, metabasalt, and hornblende gneiss containing local quartzite, schist, and 

marble. Overlies older Archean metasedimentary and metavolcanic 

rocks; unconformably underlies the Phantom Lake Metamorphic Suite. 

Thickness is about 360m. Age is Archean. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 73 

Cookson Formation 

Early Ordovician 

New Brunswick, Maine 

New England province 

Ruitenberg, A.A., 1967, Stratigraphy, structure and metallization Piskahegan-Rolling 

Dam area (northern Appalachians, New Brunswick, Canada): Leidse Geologische 

Mededelingen, v. 40, p. 79-120. 

Type locality: Exposures on the north side of Cookson Island in Oak 

Bay of the St. Croix River, Charlotte County, New Brunswick, Canada. 

The Cookson Fonnation, here named, occurs in the St. David Dome 

in the Piskahegan-Rolling Dam area of New Brunswick and to the 

southwest in Maine. Rocks of the Cookson were previously named the 

Dennis Fonnation by MacKenzie (1940), but that name is not retained 

because the quartzitic, intensely metamorphosed Dennis section is not 

typical of the unit. The Cookson has also been mapped as part of the 

Dark Argillite Division of the Charlotte Group of MacKenzie and Alcock 

(1960). Consists of thinly laminated black slate, silty slate, and phyllite 

containing minor amounts of interbedded quartzite and the metamorphic equivalents of the slates and phyllite. Well-developed slaty cleavage and spotted slates are typical. Separated from the overlying Oak 

Bay Fonnation by an erosional unconfonnity. Age is Early Ordovician 

based on graptolites. 

Cooney Canyon Member of the Cooney Tuff 

Oligocene 

New Mexico 

Basin and Range province 

Ratte, J.C., 1981, Geologic map of the Mogollon quadrangle, Catron County, New Mexico: 

U.S. Geological Survey Geologic Quadrangle Map GQ-1557, scale 1:24,000. 

Type section: Cooney Canyon of Mineral Creek, S¥2 sec. 20, T. 10 S., 

R. 19 W., Mogollon quadrangle, Catron County, N.Mex. 

Rocks fonnerly mapped as the Cooney Quartz Latite by Ferguson 

(1927) and the upper quartz latitic member of the Cooney Tuff by Ratte 

and Finnell (1978) are here named the Cooney Canyon Member, the 

upper member of the Cooney Tuff in Catron County, N. Mex. Consists 

of rhyolitic to quartz-latitic ash-flow tuff that has multiple simple and 

compound cooling units, some separated by volcaniclastic sandstone. 

Tuffs vary from partially welded to densely welded and are petrographically variable, containing phenocrysts of oligoclase-andesine, minor 

amounts of biotite and opaque oxide, and rare clinopyroxene, zircon, 

and oxyhornblende in a devitrified cryptocrystalline matrix. Overlies 

the Whitewater Creek Member of the Cooney Tuff; underlies unnamed 

volcanic rocks. Thickness is 200 m in Cooney Canyon and ranges from 
74 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

400 to 500 m on the north side of Whitewater Creek. Age is Oligocene 

based on a potassium-argon biotite age of 32 Ma. 

Cope Hollow Formation of the St. Francois Mountains 

Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: Exposures north of the swimming area of Johnson 

Shut-ins State Park, SW1/4NW1/4 sec. 16, T. 33 N., R. 2 E., St. Francois 

Mountains, Johnson Shut-ins quadrangle, Reynolds County, Mo. 

Named for Cope Hollow. 

Rocks described as the upper part of the tuff of Johnson Shut-ins by 

Anderson (1970) are here named the Cope Hollow Formation in the 

Taum Sauk Caldera in the western St. Francois Mountains, Mo. 

Consists of four informal cooling units: (A), black, crossbedded air-fall 

tuff, 9 m thick; (B), deep-maroon ash-flow tuff, 5 m thick; (C), 

dark-gray, crossbedded air-fall tuff, 28 m thick; (D), maroon ash-flow 

tuff, thickness unknown. Overlies the Johnson Shut-ins Rhyolite (new 

name); is the youngest volcanic unit. Age is Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E. B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Cope Hollow Formation. 

Copper Falls Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Cutbank on west side of Bad River, 0.8 km northwest of 

Copper Falls, in Copper Falls State Park, SWlf4SEl/4NWlf4 sec. 17, 

T. 45 N., R. 2 W., Mellen 15-minute quadrangle, Ashland County, Wis. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 75 

Subunit: Nashville Member. 

The Copper Falls Formation, here named, is in a broad area of 

northern Wisconsin and includes till derived from the Superior Lobe, 

Chippewa Sublobe, Wisconsin Valley Lobe, and the Langlade Lobe in 

the Lake Superior basin. Includes the Nashville Member (new name) in 

the Chippewa Sublobe in Forest, Langlade, and Oneida Counties. 

Consists of reddish-brown, mostly fluvial sand, gravel, and till. Unconformably overlies pre-Pleistocene or older Pleistocene units; unconformably underlies the Miller Creek Formation (new name) or lies at the 

surface. Thickness at the type section is 45 m. Age is late Pleistocene 

(late Wisconsinan and possibly early Wisconsinan). 

Copperton Formation of the libby Creek Group 

Early Proterozoic 

Wyoming 

Green River basin 

Flurkey, A.J., Houston, R.S., Karlstrom, K.E., and Kratochvil, T.L., 1981, The geology 

of Archean and Early Proterozoic terranes of the Sierra Madre, Wyoming, in 

Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, eds., A summary of the 

geology and uranium potential of Precambrian conglomerates in southeastern Wyoming: U.S. Department of Energy National Uranium Resource Evaluation, 

v. 1, pt. 3, p. 401-541. 

Type area: Exposures in the Sierra Madre, T. 14 N., R. 84-87 W., 

Carbon County, Wyo. May be named for the old town site of Copperton. 

The informal Copperton quartzite of Graff (1978) is here named the 

Copperton Formation in the lower Libby Creek Group in the Sierra 

Madre and is correlated with the Medicine Peak Quartzite, Lookout 

Schist, and Sugarloaf Quartzite in the Medicine Bow Mountains, Wyo. 

Consists of white, brecciated, coarse-grained, highly sheared kyanitic 

quartzite containing minor amounts of phyllite. Is in thrust fault contact 

with the underlying Vagner Formation of the Deep Lake Group along 

the Quartzite Peak fault; in thrust fault contact with the Slaughterhouse 

Formation of the upper Libby Creek Group along the Hidden Treasure 

fault. Is intruded by the Gaps Trondhjemite (new name). Thickness is 

1,070 m. Age is Early Proterozoic. 

Cornell Dam Member of the Valentine Formation of the 

Ogallala Group 

Miocene 

Nebraska 

Chadron arch 

Skinner, M.F., and Johnson, F.W., 1984, Tertiary stratigraphy and the Frick Collection 

of fossil vertebrates from north-central Nebraska: American Museum of Natural 

History Bulletin, v. 178, art. 3, p. 215-368. 
76 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Outcrop west of the original mouth of Minnechaduza 

Creek and its junction with the Niobrara River, SEl/4 sec. 22, T. 34 N., 

R. 27 W., Sparks quadrangle, Cherry County, Nebr. Named for Cornell 

Dam on the Niobrara River, 0.25 mi above the mouth of Minnechaduza 

Creek. 

The Cornell Dam Member of the Valentine Formation, here named, 

is in north-central Nebraska. Consists of gray, whitish-weathering, 

firm, silty sandstone and clay containing manganese stained nodules, 

glass shards, and vertebrate fossil beds. Unconformably overlies the 

Rosebud Formation; unconformably underlies the Crookston Bridge 

Member of the Valentine. Thickness at the type section is 42 ft. Age is 

Miocene based on an age of 11.6 Ma for the Hurlbut ash in the Cornell 

Dam Member. 

Coronado Hills Conglomerate of the Thunderbird Group 

Middle Proterozoic 

Texas 

Orogrande basin 

Thomann, W.F., 1981, Ignimbrites, trachytes, and sedimentary rocks of the Precambrian 

Thunderbird Group, Franklin Mountains, El Paso, Texas: Geological Society of 

America Bulletin, v. 92, no. 2, pt. I, p. 94-100. 

Type section: Exposure 3,000 ft northeast of Smugglers Pass in 

Fusselman Canyon, Franklin Mountains, lat 31°53'06" N., long 

106°29'34" W., El Paso County, Tex. Derivation of name not stated. 

The Coronado Hills Conglomerate is here named the lowest of three 

formations in the Thunderbird Group (new name) in the Franklin 

Mountains, Tex. Consists of well-rounded cobbles and pebbles of 

quartzite, quartz-sericite siltstone, shale, chert, jasper, ignimbrite, 

porphyritic trachyte, and rare marble and granite in a recrystallized 

matrix of quartz, feldspar, pumice, and glass shards. Horizontal bedding, scour fills, and crossbedding are visible. Unconformably overlies 

the Lanoria Quartzite; underlies the Smugglers Pass Formation (new 

name) of the Thunderbird Group. Thickness at the type section is about 

75 ft and ranges from 35 to 90 ft. Age is late Precambrian [Middle 

Proterozoic] (950 Ma). 

Cossatot Formation of the Trinity Group 

Early Cretaceous 

Arkansas 

Ouachita tectonic belt province 

Darling, B.K., and Lock, B.E., 1984, The surface formations of the Trinity Group in 

southwestern Arkansas, and a proposed revision of stratigraphic rank for the three 

lower units: Gulf Coast Association of Geological Societies Transactions, 34th Annual 

Meeting, p. 321--327. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 77 

Type section: Exposures approximately 4 mi north of the settlement of 

Provo, sec. 4, T. 8 S., R. 29 W., Sevier County, Ark. Named for the 

Cossatot River, which flows west of the type locality. 

Subunits: Pike Gravel Member, Delight Sand Member, Dierks Limestone Member. 

The Cossatot Formation is here named as the lowermost formation 

of the Trinity Group in Sevier, Howard, and Pike Counties, southwestern Arkansas. Was previously informally named the Provo formation by 

Nichols (1956), consisting of rocks constituting a single transgression, 

the Pike Gravel, Delight Sand, and Dierks Limestone, the three lower 

units of the Trinity Group in southwestern Arkansas. These names are 

retained, reduced in rank, and designated as members of the Cossatot. 

The basal Pike Gravel Member, composed of rounded to subrounded 

loose gravels, boulders, and conglomerate, is 25 to 100 ft thick; the 

Delight Sand Member, a fine-grained, crossbedded quartz sand containing chert fragments and claystone beds, is 10 to 110ft thick; and the 

uppermost Dierks Limestone Member, consisting of hard gray limestone that has thin layers of green shale, is 10 to 25 ft thick. Unconformably overlies the Jackfork Group; conformably underlies the Holly 

Creek Formation of the Trinity Group. Thickness ranges from 85 to 90 

ft at the type section. Age is Early Cretaceous. 

Cow Ridge Member of the Green River Formation 

Eocene 

Colorado 

Piceance basin 

Johnson, R.B., 1984, New names for units in the lower part of the Green River 

Formation, Piceance Creek basin, Colorado: U.S. Geological Survey Bulletin 1529-I, 

20 p. 

Type section: South side of Cow Ridge, sec. 31, T. 7 S., R. 98 W., Long 

Point quadrangle, Garfield County, Colo. Reference sections: Yellow 

Creek, sees. 9and 10, T. 2 N., R. 93W., and Fletcher Gulch, sees. 3, 10, 

11, 14, T. 1 N., R. 100 W., Garfield County, Colo. 

The Cow Ridge Member, here named, is the oldest member of the 

Green River Formation in the Piceance Creek basin of western Colorado. Formerly mapped as part of the Douglas Creek Member of the 

Green River and as part of the Wasatch Formation. Consists of brown 

ostracoda! clay shale, carbonaceous shale, thin persistent sandstones, 

siltstones, and ostracoda! limestones. Contains ostracode, mollusk, 

turtle, crocodile, bird, and fish fossils and palynomorphs. At Fletcher 

Gulch, the lower part of the Cow Ridge consists of low-grade, clay-rich 

oil shale and the upper part consists of claystone, mudstone, and 

conglomeratic sandstone. Deposited in the early stage of Lake Uinta 

as a freshwater, lacustrine unit. Overlies the Wasatch Formation; 
78 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

underlies the Garden Gulch Member at Fletcher Gulch and elsewhere 

underlies the tongue of the Wasatch. Thickness is 63 m at the type 

section, 149 m at Yellow Creek, and 216 m at Fletcher Gulch. Age is 

early and early middle Eocene based on palynomorphs. 

Craigmont Member of the Saddle Mountains Basalt of the 

Columbia River Basalt Group 

Miocene 

Idaho 

Eastern Columbia basin 

Camp, V.E., 1981, Geologic studies of the Columbia Plateau: Part II. Upper Miocene 

basalt distribution, reflecting source locations, tectonism, and drainage history in the 

Clearwater embayment, Idaho: Geological Society of America Bulletin, v. 92, no. 9, 

pt. I, p. 669--678. 

Type locality: Craigmont, Lewis County, Idaho. 

The Craigmont Member of the Saddle Mountains Basalt of the 

Columbia River Basalt Group, here named, is in the Nez Perce plateau 

of the Clearwater embayment in Idaho. Consists of fine- to mediumgrained basalt and rare olivine. Overlies the Icicle Flat Member (new 

name) and Grangeville Member (new name) of the Saddle Mountains 

Basalt. Age is late Miocene. 

Cranberry Lake Formation of the Oswegatchie Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: Exposures at the base of Indian Mountain near the south 

end of Cranberry Lake, St. Lawrence County, N.Y. 

The informal Cranberry Lake formation of Leavell (1977) is here 

named the Cranberry Lake Formation of the Oswegatchie Group in the 

western Adirondack Highlands, N.Y. Consists of layered gneiss and 

marble in the lower part and quartzite, granulite, marble, and gneiss in 

the upper part. Correlates with the Gouverneur Marble of the Oswegatchie Group and the Paradox Lake Formation of the Lake George 

Group (both new names); overlies rocks correlated with the Poplar Hill 

Gneiss (new name) or Baldface Hill Gneiss (new name), and underlies 

rocks correlated with the Pleasant Lake Gneiss (new name), all of the 

Oswegatchie Group in the Northwest Lowlands. Age is Proterozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 79 

Cranberry-Mine Layered Gneiss 

Middle Proterozoic 

North Carolina 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: ·Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Cranberry iron mine, near the town of Cranberry, lat 

36°08' N., long 81°58' W., Elk Park 7.5-minute quadrangle, Avery 

County, N.C. Reference locality: Outcrop on North Carolina State Road 

194, 1/4 mi east of its junction with U.S. Highway 19E, 1 mi northeast of 

the Cranberry mine. 

Older layered country rocks in the Elk River massif in North 

Carolina, here named the Cranberry-Mine Layered Gneiss, were previously mapped by Keith (1903) as part of the Cranberry Granite, which 

is revised as the Cranberry Suite and restricted to the plutonic rocks of 

the Elk River massif. Is equivalent to the Shoals Gneiss in Virginia. Age 

is Middle Proterozoic. 

Crater Tuff Breccia Member of the Colter Formation 

Miocene 

Wyoming 

Yellowstone province 

Barnosky, A.D., 1984, The Colter Formation-Evidence for Miocene volcanism in 

Jackson Hole, Teton County, Wyoming: Wyoming Geological Association, Earth 

Science Bulletin, v. 17, p. 49-97. 

Type section: Exposures along East Pilgrim Creek (the lower part of 

the Colter Formation type section), Two Ocean Lake 7.5-minute 

quadrangle, Teton County, Wyo. Named for Crater Mountain. 

The Crater Tuff Breccia Member, here named, is the lower member 

of the Colter Formation in the area of Crater Mountain, Two Ocean 

Lake, and Emerald Lake, Teton County, Wyo. Source area for the 

member is northwest of Pilgrim Mountain adjacent to the northern part 

of the Teton fault. Consists of andesitic, trachytic, and latitic tuff and 

ignimbrite, and is distinguished by its abundant tuff breccia and tuff, 

bright-green or drab-gray color, angular to subangular lithic clasts, and 

rare rounded quartz cobbles. Overlies unnamed pre-Colter rocks, 

Paleocene Pinyon Conglomerate, or Oligocene White River Formation; 

underlies the Pilgrim Conglomerate Member (new name) of the Colter. 

Thickness is 500 m. Was deposited between 24 and 18 Ma during early 

Miocene andesitic volcanism. 
80 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Crossing Knob Gneiss 

Middle Proterozoic 

North Carolina 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Along Bethel Church Road 0.5 mi south of its junction 

with U.S. Highway 321, on the west flank of Crossing Knob, lat 36°18' 

N., long 81°52'30" W., Sherwood quadrangle, Watauga County, N.C. 

The Crossing Knob Gneiss, here named, is in the Watauga massif in 

the Blue Ridge in North Carolina, where it appears to be a roof pendant 

in the Watauga River Gneiss (new name) of the Forge Creek Suite (new 

name). Age is Middle Proterozoic. 

Crossnore Plutonic-Volcanic Complex 

late Proterozoic 

North Carolina, Tennessee, Virginia 

Piedmont-Blue Ridge province 

Rankin, D.W., Stern, T.W., McLelland, James, Zartman, R.E., and Odom, A.L., 1983, 

Correlation chart for Precambrian rocks of the eastern United States: U.S. Geological 

Survey Professional Paper 1241-E, p. E1-E18. 

Type locality: None designated. Named for the town of Crossnore, 

Avery County, N.C. 

Subunits: Grandfather Mountain Formation (Tennessee, North Carolina), Mount Rogers Formation (Virginia, North Carolina, Tennessee), 

Catoctin Formation (Virginia). 

The informal Crossnore plutonic-volcanic group of Rankin and 

others (1973) is here named the Crossnore Plutonic-Volcanic Complex. 

Consists of volcanic rocks and consanguineous mafic and felsic dikes, 

sills, and plutons intrusive into the basement crystalline rocks of the 

Blue Ridge anticlinorium. Includes, from southwest to northeast, the 

volcanic and sedimentary Grandfather Mountain Formation in North 

Carolina, the Mount Rogers Formation in Virginia, North Carolina, and 

Tennessee, and the Catoctin Formation [unintentionally included here]. 

Also includes intrusive Beech Granite in North Carolina and Tennessee, 

Striped Rock Granite in Virginia, an unnamed aegirien-augite granite 

gneiss near Crossnore, N.C., Bakersville Gabbro in North Carolina and 

Tennessee, Brown Mountain Granite in North Carolina, and Linville 

Metadiabase in North Carolina. Age is Late Proterozoic based on 

discordia intercept ages of 810 Ma for zircons from rhyolite and 824 Ma 

for zircons from granite plutons. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 81 

Crowders Creek Metaconglomerate Member of the Battleground 

Formation 

late Proterozoic 

North Carolina 

Piedmont-Blue Ridge province 

Horton, J.W., Jr., 1984, Stratigraphic nomenclature in the Kings Mountain belt, North 

Carolina and South Carolina: U.S. Geological Survey Bulletin 1537-A, p. A59-A67. 

Type locality: Cliff exposures at a bend in Crowders Creek, 180m N. 

60° W. of its junction with Squirrel Branch, midway between Crowders 

Mountain and the town of Kings Mountain, lat 35°13'58" N., long 

81°18'25" W., Gaston County, N.C. 

The Crowders Creek Metaconglomerate Member of the Battleground Formation, here named, is in the Kings Mountain belt, North 

Carolina. Was previously mapped as part of the Draytonville Conglomerate Member of the Battleground by Keith and Sterrett (1931), as 

schistose conglomerate by Espenshade and Potter (1960), and as 

informal bed E by France and Brown (1981). Is the highest of three beds 

of quartz-pebble metaconglomerate in the Battleground and is separated from the underlying Draytonville Metaconglomerate Member by 

an unnamed unit of micaceous quartzite. Age is Late Proterozoic. 

Culpeper Group 

late Triassic and Early Jurassic 

Virginia, Maryland 

Piedmont-Blue Ridge province 

Lindholm, R.C., 1979, Geologic history and stratigraphy of the Triassic-Jurassic Culpeper 

basin, Virginia: Geological Society of America Bulletin, v. 90, no. 11, pt. I, p. 995-997; 

pt. II, p. 1702-1736. 

Type locality: None designated. Named for the Culpeper basin, Virginia and Maryland. 

Subunits: Reston Formation; Manassas Sandstone; Bull Run Formation 

and its Leesburg, Goose Creek, Cedar Mountain, and Barboursville 

Conglomerate Members; Buckland Formation; Waterfall Formation. 

The sedimentary and extrusive igneous rocks of the Culpeper basin 

in Virginia and Maryland are here named the Culpeper Group. The 

name was used informally by Cornet (1977), who designated informal 

formations K through A of the Culpeper. Includes the Reston Formation; Manassas Sandstone; Bull Run Formation and its Leesburg, Goose 

Creek, Cedar Mountain, and Barboursville Conglomerate Members; 

Buckland Formation; and Waterfall Formation. Age is Late Triassic 

and Early Jurassic. 
82 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Datil Well Tuff of the Datil Group 

Oligocene 

New Mexico 

Basin and Range province 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: Northeast side of White House Canyon across U.S. 

Highway 60 from the Datil Well Campground, 1.2 mi northwest of the 

junction of U.S. Highways 60 and 12 in the town of Datil, NW1/4SW1/4 

sec. 2, T. 2 S., R. 10 W., Datil 7.5-minute quadrangle, Catron County, 

N.Mex. 

The Datil Well Tuff of the Datil Group, here named, is in the Datil 

Mountains and northern Jornada del Muerto, southwestern New Mexico. Consists of purple to pink, densely welded, moderately crystal-rich, 

rhyolite ash-flow tuff. Overlies the andesite of White House Canyon, an 

informal member of the Spears Formation, or the Dog Springs Member 

(new name) of the Spears; splits and is interbedded with the Chavez 

Canyon Member (new name) of the Spears; underlies the Rock House 

Canyon Tuff (new name) of the Datil Group. Thickness at the type 

section is 31.5 ft. Age is Oligocene based on fission-track and potassiumargon dates (36. 7 Ma). 

Davis Canyon Tuff 

Oligocene 

New Mexico 

Basin and Range province 

Ratte, J.C., 1981, Geologic map of the Mogollon quadrangle, Catron County, New Mexico: 

U.S. Geological Survey Geologic Quadrangle Map GQ-1557, scale 1:24,000. 

Type section: Sl/2 sec. 11, T. 13 S., R. 17 W., Shelley Peak quadrangle, 

Catron County, N. Mex. Reference sections: Sl/2 sec. 31, and Nl/2 sec. 

15, T. 8 S., R. 20 W., Saliz Pass quadrangle. Named for Davis Canyon, 

south flank of Shelley Peak, Shelley Peak quadrangle. 

The Davis Canyon Tuff, here named in Catron County, N. Mex., 

was formerly mapped as the lower part of the Pacific Quartz Latite of 

Ferguson (1927). Consists of light-gray, phenocryst-poor, high-silica 

rhyolite ash-flow tuff containing 1 to 10 percent phenocrysts and 

microphenocrysts of sanidine, quartz, and sodic plagioclase in a devitrified granophyric to vitroclastic matrix. Overlies the Cranktown Sandstone or unnamed volcanic rocks; underlies the Shelley Peak Tuff (new 

name) or unnamed volcanic rocks. Thickness ranges from 60 to 150 m at 

the type section and from 0 to 50 m in the Mogollon quadrangle. Age is 

Oligocene based on potassium-argon ages of 28.9 Ma on sanidine and 

30.7 Ma on biotite. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 83 

Davis Spring Formation 

Early Mississippian (Kinderhookian or Osagean(?)) 

Nevada 

Great Basin province 

Hose, R.K., Armstrong, A.K., Harris, A.G., and Mamet, B.L., 1982, Devonian and 

Mississippian rocks of the northern Antelope Range, Eureka County, Nevada: U.S. 

Geological Survey Professional Paper 1182, 19 p. 

Type section: Outcrops in the SE1/4 sec. 20, T. 16 N., R. 51 E., northern 

Antelope Range, Eureka County, Nev. Named for Upper Davis Spring, 

which is 3 km southeast of the type section. 

The Davis Spring Formation, here named, is in the northern 

Antelope Range, Nevada. Consists of pale-brown, very fine grained, 

siliceous, dolomitic siltstone and finely laminated chert that has a 

translucent pale-brown organic pigment in the matrix. Conodonts occur 

20 m above the base and are mostly redeposited Devonian and Mississippian species. Abundance of organic material and lack of bioturbation 

suggest deposition in euxinic bottom waters and oxygenated upper 

levels. Contact with the underlying Fenstermaker Wash Formation 

(new name) is sharp and represents an unconformity of considerable 

magnitude; conformably and sharply underlies the Kinkead Spring 

Limestone (new name) or unconformably underlies the Antelope Range 

Formation (new name). Thickness is 125m at the type section. Age is 

Early Mississippian (no older than late Kinderhookian but possibly 

Osagean) based on conodonts. 

Delamar Mountain Formation of the Big Bear Group 

Precambrian 

California 

Mohave basin 

Cameron, C.S., 1982, Stratigraphy and significance of the upper Precambrian Big Bear 

Group, in Cooper, J.D., ed., Geology of selected areas in the San Bernardino 

Mountains, western Mohave desert, and southern Great Basin, California: Geological 

Society of America, Cordilleran Section, 78th Annual Meeting, guidebook, field trip 9, 

p. 5-20. 

Type section: Delamar Mountain, SEl/4 sec. 1 and SWl/4 sec. 6, T. 2 N., 

R. 1 E., Fawnskin 7.5-minute quadrangle, San Bernardino County, 

Calif. 

The uppermost unit of the Big Bear Group (new name) in the area of 

Delamar Mountain and Sugarloaf Mountain in the San Bernardino 

Mountains, California, is here named the Delamar Mountain Formation, 

following the informal usage of Cameron (1981). Contains two informal 

members: lower member Dl, which consists of a heterogeneous 

sequence of calc-silicate rock, quartzite, schist, and marble; and upper 
84 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

member D2, which consists of conformably overlying quartzite. Gradationally overlies the Green Spot Formation (new name) of the Big Bear 

Group; conformably underlies the late Precambrian and Early Cambrian Wood River Formation. Thickness at the type section is 217 m. 

Age is late Precambrian. 

Delle Phosphatic Member of the Woodman Formation, 

Chainman Shale, Deseret Limestone, Deep Creek Formation, 

Little Flat Formation, Aspen Range Formation, or Brazer 

Dolomite 

Mississippian (Osagean and Meramecian) 

Utah, Idaho, Nevada, Wyoming 

Great Basin province, Green River basin, Snake River basin, Wasatch 

uplift 

Sandberg, C.A., and Gutschick, R.C., 1984, Distribution, microfauna, and source-rock 

potential of Mississippian Delle Phosphatic Member of Woodman Formation and 

equivalents, Utah and adjacent states, in Woodward, Jane, Meissner, F.F., and 

Clayton, J. L., eds., Hydrocarbon source rocks of the greater Rocky Mountain region: 

Denver, Rocky Mountain Association of Geologists, p. 135--178. 

Type section: Exposures along a low ridge in the South Lakeside 

Mountains, SEl/4SEl/4SWl/4 sec. 6, T. 1 N., R. 8 W., Delle quadrangle, 

Tooele County, Utah. Named for the town of Delle, Utah. 

The widespread Delle Phosphatic Member, here named, is the basal 

member of seven formations in an area extending for 750 km along a 

northeast-trending axis from southeastern Nevada through western 

Utah and extreme southwestern Wyoming to southeastern Idaho. 

Replaces the informal phosphatic member of Sandberg and Gutschick 

(1979, 1980). At the type section in the South Lakeside Mountains and 

in the Deep Creek Mountains of Utah, it is assigned to the Woodman 

Formation; in the Needle Range, Utah and Nevada, to the Chainman 

Shale; in Ophir Canyon, Oquirrh Mountains, Utah, to the Deseret 

Limestone; at Hunter Canyon, Deep Creek Mountains, Idaho, to the 

Deep Creek Formation; at Little Flat Canyon, Chesterfield Range, 

Idaho, to the Little Flat Formation; at North Georgetown Canyon in 

the Aspen Range, Idaho and Wyoming, to the Aspen Range Formation; 

and in Brazer Canyon, Crawford Mountains, Utah and Wyoming, to the 

Brazer Dolomite. Includes two informally named discrete lithologic 

units, a lower 9.1-m-thick cherty unit consisting mainly of bedded black 

radiolarian chert (lydite) and a 5.8-m or thicker micritic limestone unit, 

which caps the member. The remainder of the Delle consists of 

thin-bedded gray to black organic-rich phosphatic claystone, mudstone, 

shale, siltstone, peloidal phosphorite, cherty micrite, red siltstone, 

brown prodeltaic siltstone, and thin interbeds of sandstone and coarse 

debris-flow encrinite. Contains conodonts, radiolarians, foraminifers, 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 85 

planktonic to benthic animals, and floating marine and transported land 

plants. Overlies the Joana, Lodgepole, Mission Canyon, or Gardison 

Limestones; underlies the Needle Siltstone Member, Tetro Member, or 

equivalents. Thickness is 59 m at the type section. Age is Mississippian 

(Osagean and Meramecian). 

Devils Bridge Clay 

Miocene(?) and Pliocene(?) 

Massachusetts 

Atlantic Coast basin 

Kaye, C.A., 1983, The autochthonous and allochthonous Coastal Plain deposits of 

Martha's Vineyard and the Marshfield-Scituate area, southeastern Massachusetts: 

Atlantic Coastal Plain Geological Association field trip guidebook, 34 p. 

Type locality: Devils Bridge, a bouldery shoal that juts out about 2 km 

from the north end of Gay Head Cliff, Martha's Vineyard, Mass. 

The Devils Bridge Clay, here named, is part of the Gay Head 

moraine in Martha's Vineyard, Mass., and is composed of thrust plates 

made up of remnants of Coastal Plain sediments that were stacked up 

during Pleistocene glaciation. Consists of black, massive, organic-poor, 

ferruginous clay that oxidizes rapidly to brown goethite. Overlies the 

Gay Head Greensand (new name) with erosional contact; underlies the 

Lobsterville Sand (new name) or Pleistocene deposits. Thickness is 2.6 

m. Age is late Miocene(?) and early Pliocene(?) based on a restricted 

pollen assemblage. 

Devil's Graveyard Formation of the Buck Hill Group 

Eocene and Oligocene 

Texas 

Permian basin 

Stevens, J.B., Stevens, M.S., and Wilson, J.A., 1984, Devil's Graveyard Formation 

(new), Eocene and Oligocene age, Trans-Pecos Texas: Texas Memorial Museum 

Bulletin 32, p. 1-21. 

Type area: Devil's Graveyard, along Alamo de Cesario Creek and the 

south face of Bandera Mesa, Agua Fria and Tascotal Mesa quadrangles, 

Brewster and Presidio Counties, Tex. Reference sections and boundary 

stratotypes are designated. 

Subunit: Bandera Mesa Member. 

The Devil's Graveyard Formation of the Buck Hill Group, here 

named, is in the Agua Fria-Green Valley area of Trans-Pecos, Tex. 

Consists of volcaniclastic tuff, bentonitic tuff, mudstone, and sandstone 

and is divided into informal lower and middle members and the upper 

Bandera Mesa Member (new name). Marker beds useful for correlation 

are informally named the Junction facies, Variegated beds, Lunch 
86 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Locality sandstone, Northeast facies, Car Park conglomerate, Strawberry tuff, Titanothere channels, Purple Bench tuff, Skyline channels, 

Cotter channels, and Upper breccia-conglomerate. Unconformably 

overlies Cretaceous rocks; underlies the Mitchell Mesa Rhyolite or the 

informal Yellow conglomerate. Thickness is 1,635 ft. Age is Eocene and 

Oligocene based on vertebrate fauna. 

Devil's Pass Member of the Virginian Ridge Formation 

Cretaceous (Albian to Cenomanian) 

Washington 

Northern Cascade Range-Okanogan province 

Trexler, J.H., Jr., 1985, Sedimentology and stratigraphy of the Cretaceous Virginian 

Ridge Formation, Methow Basin, Washington: Canadian Journal of Earth Sciences, 

v. 22, no. 9, p. 1274-1285. 

Type section: Exposures along Jackita Ridge, south of Devil's Pass, 

western side of the Methow Basin, Okanogan County, Wash. 

The Devil's Pass Member of the Virginian Ridge Formation, here 

named, is in the Methow Basin, the southernmost of a series of Mesozoic 

basins that rest with angular unconformity on older rocks in the 

Cascades, north-central Washington. Consists of a thick sequence of 

chert-pebble conglomerate and chert-volcanic-lithic sandstone. Represents an amalgamated, prograding fan-delta system. Interfingers with 

and gradationally overlies the Slate Peak Member (new name) of the 

Virginian Ridge; underlies the Winthrop Formation in the south and is 

truncated by modern erosion in the north. Thickness at the type section 

is greater than 1,000 m. Age is Cretaceous (Albian to Cenomanian). 

Dibekulewe Bed 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Road cut on the west side of South Curry Street, Stewart, 

south of Carson City, center Nt/2SW1/4NW1/4 sec. 20, T. 15 N., R. 20 E., 

Carson City 7.5-minute quadrangle, Lyon County, Nev. Dibekulewe is 

the Washo Indian name for the cove in the hills to the west, where the 

Carson City "C" is painted. 

The Dibekulewe Bed, here named, occurs west of Stewart, in the 

Lake Lahontan area, Nevada. Consists of corroded, phenocryst-poor 

tephra particles enclosed in fine sand and silt. Underlies the Mexican 

Dam Bed (new name). Age is Pleistocene. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 87 

Digdeguash Formation 

Silurian 

New Brunswick, Maine 

New England province 

Ruitenberg, A.A., 1967, Stratigraphy, structure and metallization Piskahegan-Rolling 

Dam area (northern Appalachians, New Brunswick, Canada): Leidse Geologische 

Mededelingen, v. 40, p. 79-120. 

Type locality: Exposures along the Digdeguash River at Tryon, Charlotte County, New Brunswick, Canada. 

Rocks in the Pleasant Ridge and St. David Dome areas in Charlotte 

County, N.B., previously named the Canoose Formation by MacKenzie 

(1940), are here named the Digdequash [sic] Formation. Consists of 

dark-gray and olive-green quartz wacke, silty slate, and slate. Grades 

laterally into the facies equivalent Waweig Formation (new name). Age 

is Late Silurian and Early Devonian. 

Ruitenberg, A.A., and Ludman, Allan, 1978, Stratigraphy and tectonic setting of early 

Paleozoic sedimentary rocks of the Wirral-Big Lake area, southwestern New 

Brunswick and southeastern Maine: Canadian Journal of Earth Science, v. 15, p. 22-32. 

The Digdeguash Formation is here extended from Pleasant Ridge, 

New Brunswick, to Third Chain Lake, Maine. Interfingers with the 

Silurian Waweig Formation (new name), to which it is partly equivalent; grades upward into the Flume Ridge Formation (new name). Age 

is Silurian. 

Ditch Creek Siltstone Member of the Hornbrook Formation 

late Cretaceous (Turonian and Coniacian) 

California, Oregon 

Klamath Mountains province 

Nilsen, T.H., 1984, Tectonics and sedimentation of the Upper Cretaceous Hornbrook 

Formation, Oregon and California, in Crouch, J.K., and Bachman, S.B., eds., 

Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and Mineralogists, Pacific Section, v. 38, p. 101.-118. 

Type section: Roadcuts along the northbound lane of Interstate Highway 1-5, 3 km south of Hornbrook, NEl/4NEl/4 sec. 32, T. 47 N., 

R. 6 W., Hornbrook 15-minute quadrangle, Siskiyou County, Calif. 

Named for Ditch Creek, 3 km west of Hornbrook. 

The Ditch Creek Siltstone Member of the Hornbrook Formation, 

here named, occurs along the northeast margin of the Klamath Mountains in Siskiyou County, Calif., and Jackson County, Oreg. Consists of 

gray siltstone and fine-grained, silty sandstone and represents outer 

shelf deposits. Conformably overlies the Osburger Gulch Sandstone 

Member (new name), erosionally or gradationally underlies the Rocky 

Gulch Sandstone Member (new name), and conformably or gradation-
88 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

ally locally underlies the Blue Gulch Mudstone Member (new name), all 

of the Hornbrook. Thickness is 61.6 mat the type section and ranges 

from 20 to 80 m. Age is Late Cretaceous (Turonian and Coniacian) based 

on mollusks and foraminifera. 

Dixon Gap Metaconglomerate Member of the Battleground 

Formation 

Late Proterozoic 

North Carolina, South Carolina 

Piedmont-Blue Ridge province 

Horton, J.W., Jr., 1984, Stratigraphic nomenclature in the Kings Mountain belt, North 

Carolina and South Carolina: U.S. Geological Survey Bulletin 1537-A, p. A59-A67. 

Type locality: Exposures at the ridge crest of Kings Mountain at Dixon 

Gap, where secondary road 2245 crosses the ridge, lat 35°10'27" N., long 

81°21'46" W., Cleveland County, N.C. 

Rocks previously included in the Draytonville Conglomerate Member of Keith and Sterrett (1931) and described as bed C by France and 

Brown (1981) are here named the Dixon Gap Metaconglomerate Member of the Battleground Formation in the Kings Mountain belt, North 

Carolina and South Carolina. Consists of quartz-pebble metaconglomerate. Overlies quartz-sericite schist and underlies the Jumping Branch 

Manganiferous Member (new name) of the Battleground. Age is Late 

Proterozoic. 

Dobbins Alas kite 

Tertiary 

Arizona 

Basin and Range province 

Reynolds, S.J., 1985, Geology of the South Mountains, central Arizona: Arizona Bureau 

of Geology and Mineral Technology Bulletin 195, 61 p. 

Type locality: North flank of Dobbins Lookout, eastern Main Ridge of 

the South Mountains, Maricopa County, Ariz. 

The Dobbins Alaskite, here named, occurs in the South Mountains 

near Phoenix, Ariz., at Dobbins Lookout and Mount Suppoa in the Main 

Ridge, and in the Boundary Hills and other parts of the Southern 

Foothills. Consists of white to cream, fine-grained, mylonitic alaskitic 

granite, quartz porphyry, and felsite that are contemporaneous and 

comagmatic. The last of three phases of a composite pluton that occupies 

the eastern half of the South Mountains, it is found along border zones 

of the second phase Telegraph Pass Granite (new name), and in places 

it overlies the first phase mylonitic South Mountains Granodiorite (new 

name). Age is middle Tertiary. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 89 

Dog River Formation of the Sandy Springs Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K. I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures near and along Dog River, northeast Douglas 

County, Ga. 

The unnamed lower unit on the northwest limb of the AustellFrolona antiform, lying gradationally above the Mud Creek Formation 

(new name) of the New Georgia Group (new name), is here named the 

Dog River Formation of the Sandy Springs Group (western belt). 

Consists of an intercalated sequence of muscovite-biotite-quartzfeldspar gneiss (metagraywacke), garnet-muscovite schist, amphibolite, 

and thin layers of banded iron formation. Conformably underlies the 

Andy Mountain Formation (new name) of the Sandy Springs Group 

(western belt). Is equivalent to the Powers Ferry Formation of the 

Sandy Springs Group (eastern belt). Age is Late Proterozoic and (or) 

early Paleozoic. 

Dog Springs Member of the Spears Formation of the Datil 

Group 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type area: Dog Springs, Chavez, and Old Canyons, 20 mi northeast of 

Datil, Sl/2 T. 2 N., R. 8 W., and the north edge ofT. 1 N., R. 8 W., 

northern Gallinas Mountains, D Cross and Dog Springs 7.5-minute 

quadrangles, Socorro County, N. Mex. 

The Dog Springs Member is here named the basal member of the 

Spears Formation of the Datil Group in the Gallinas and Datil Mountains, southwestern New Mexico. Consists of light-tan to brown, 

crystal-rich, nonpumiceous, quartz-latite breccias containing, in the 

Dog Springs area, large exotic blocks of limestone and autobrecciated 

volcanic rocks as much as 0.5 mi long and 250 ft thick, probably 

deposited by mudflows. A few large areas of autobrecciated rocks 

appear to be intrusives. Well-stratified, tuffaceous pond deposits are 

interbedded in the mudflow breccias. Bedding in the breccias is highly 

contorted and chaotic, probably resulting from penecontemporaneous 

soft-sediment deformation. Overlies the Baca Formation; underlies the 
90 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Chavez Canyon Member (new name) of the Spears or the Datil Well Tuff 

(new name) of the Datil Group. Thickness ranges from 0 to 3,000 ft. Age 

is Oligocene based on a potassium-argon date (39.6 Ma) and a zircon 

fission-track date (38.6 Ma). 

Dollarhide Formation 

Early Permian 

Idaho 

Snake River basin 

Hall, W.E., 1985, Stratigraphy and mineral deposits in middle and upper Paleozoic rocks 

of the black-shale mineral belt, central Idaho, in Mcintyre, D.H., ed., Symposium on 

the geology and mineral deposits of the Challis 1 o x 2° quadrangle, Idaho: U.S. 

Geological Survey Bulletin 1658 A-S, p. 117-131. 

Type locality: Exposures along the ridge between Dollarhide Summit 

and Dollarhide Mountain, 32 km west of Ketchum, Dollarhide Mountain 

7.5-minute quadrangle, Blaine County, Idaho. 

Rocks formerly mapped as part of the Wood River Formation are 

here named the Dollarhide Formation. Crops out over an area of 100 

km2 on the eastern side of the Idaho batholith in the central Idaho 

black-shale mineral belt. Consists of dark-gray, carbonaceous limestone, fine-grained limy sandstone, dark-gray and brown banded siltite, 

and quartzite. Graded bedding and convolute structures are common. Is 

intruded by the Idaho batholith. Thickness of partial measured section 

is 653 m. Age is probably Early Permian based on fusulinids. 

Dort Granite 

Mississippian(?) 

North Carolina, Virginia 

Atlantic Coast basin 

Becker, S.W., 1981, Petrography of the granitic basement beneath the Coastal Plain, 

Gates County, North Carolina: Southeastern Geology, v. 22, no. 1, p. 39-44. 

Type locality: Drill hole DO-l, depth interval 323-410 m, near Dort, 

Gates County, N.C. 

Crystalline basement rock located in the center of a large gravity 

anomaly at the North Carolina-Virginia border, is here named the Dort 

Granite. Consists of gray, coarse-grained amphibole-biotite granite 

containing small pegmatite and aplite dikes and mafic clots, fractured by 

two episodes of brittle deformation. First episode fractures are filled 

with calcite-epidote-chlorite-fluorite veins; second episode fractures are 

filled with calcite. Petrographically resembles the Petersburg Granite 

of Mississippian age. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 91 

Douglas Member of the Miller Creek Formation 

Holocene 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. •1-15. 

Type section: Exposures in bluff, 1. 5 km west of the mouth of Hanson 

Creek, SE1/4SW1f4SW1/4 sec. 27, T. 49 N., R. 12 W., Poplar NE 

7.5-minute quadrangle, Douglas County, Wis. Named for Douglas 

County. 

Following the informal usage of Need (1980), the Douglas Member of 

the Miller Creek Formation (new name), here named, is in the Superior 

Lobe west of the Bayfield Peninsula in Wisconsin. Consists of reddishbrown till. Overlies pre-Pleistocene rock or tills of the Copper Falls 

Formation (new name) and Hanson Creek Member (new name) of the 

Miller Creek Formation; underlies silt and clay of the Miller Creek or 

lies at the surface. Thickness ranges from 1 to 15 m. Age is earliest 

Holocene. 

Dreibelbis Member of the Windsor Township Formation 

Middle Ordovician 

Pennsylvania 

Appalachian basin 

Lash, G.G., and Drake, A.A., Jr., 1984, The Richmond and Greenwich slices of the 

Hamburg klippe in eastern Pennsylvania-Stratigraphy, sedimentology, structure, 

and plate tectonic implications: U.S. Geological Survey Professional Paper 1312, 40 p. 

Type locality: Exposures along the west bank of Maiden Creek north of 

Dreibelbis, Hamburg 7.5-minute quadrangle, Berks County, Pa. 

Rocks in the Greenwich slice of the Hamburg klippe in east-central 

Pennsylvania, mapped as the Martinsburg Formation by Willard (1943), 

are here named the Dreibelbis Member of the Windsor Township 

Formation (new name). Contains three main intercalated rock types 

which may be lens-shaped bodies: laminated to thick-bedded calcareous 

graywacke and greenish-gray shale interbedded with graywacke, siltstone, and mudstone; ripple laminated, locally conglomeratic, calcareous graywacke sandstone interbedded with siltstone and mudstone; and 

medium- to thick-bedded locally calcareous sandstone interbedded with 

siltstone, mudstone, and claystone-shale. Was deposited as turbidite 

and grain-flow channel facies incised into the underlying levee and 

open-fan sediments of the Weisenberg Member (new name) of the 

Windsor Township. Apparent thickness is 3,660 m. Age is Middle 

Ordovician based on graptolites in the graywacke. 
92 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Drowning Creek Formation of the Crab Orchard Group 

Early and Middle Silurian (Llandoverian) 

Kentucky 

Cincinnati arch 

McDowell, R.C., 1983, Stratigraphy of the Silurian outcrop belt on the east side of the 

Cincinnati arch in Kentucky, with revisions in the nomenclature: U.S. Geological 

Survey Professional Paper 1151-F, 27 p. 

Type section: Exposures along Kentucky Highway 52, east of Drowning 

Creek, near Winston, Panola quadrangle, Estill County, Ky. Reference 

section: Along Kentucky Highway 10, lower part southwest of Cabin 

Creek and upper part northeast of Cabin Creek, Tollesboro quadrangle, 

Lewis County, Ky. 

Subunits: In Bath County, Ky., and south: Brassfield Member, Plum 

Creek Shale Member, Oldham Member. North of Bath County: 

Brassfield Member, Dayton Dolomite Member. 

A sequence of beds, predominantly dolomite, is here named the 

Drowning Creek Formation of the Crab Orchard Group, revised and 

raised in rank from formation. In Bath County, Ky., and to the south, 

the Drowning Creek is divided into three members, the Brassfield, 

reduced in rank from formation, and the Plum Creek Shale and Oldham 

Members, formerly of the Crab Orchard Formation. The Brassfield 

consists of dolomite or limestone beds containing minor amounts of 

interbedded shale and chert nodules and lenses, 9 to 28 ft thick. The 

Plum Creek Shale consists of greenish-gray, poorly fissile clay shale 

that has beds and lenses of dolomite, about 5.5 ft thick. The Oldham 

consists of interbedded gray, fossiliferous dolomite and greenish-gray, 

poorly fissile shale, 3 to 15ft thick. Overlies the Preachersville Member 

of the Drakes Formation; underlies the Lulbegrud Shale Member of the 

Alger Shale. Thickness ranges from 20 to 50 ft. North of Bath County 

the Drowning Creek is divided into the Brassfield Member, undifferentiated beds where the Plum Creek Shale and Oldham become indistinguishable, and the Dayton Dolomite Member, reduced in rank from 

Dayton Limestone. Overlies the Preachersville Member of the Drakes 

Formation and underlies the Estill Shale, raised in rank from 

Estill Shale Member of the Alger Shale. North of Bath County, 

thickness ranges from 40 to 60 ft. Age is Early and Middle Silurian 

(Llandoverian). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 93 

Eagle lake Gneiss of the lake George Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: Exposures on the north shore of Eagle Lake, Paradox 

Lake 15-minute quadrangle, Essex County, N.Y. 

Rocks called the older paragneiss by Walton and deW aard (1963) are 

here named the Eagle Lake Gneiss, the basal unit of the Lake George 

Group (new name) in the eastern Adirondack Mountains of New York. 

Consists of thin, discontinuous exposures of biotite-quartz-plagioclase 

gneiss containing granitic layers and veins, and quartzite and quartzsillimanite gneiss. Unconformably overlies the Piseco Group (new 

name). Correlates with the Baldface Hill Gneiss (new name) and the 

Poplar Hill Gneiss (new name), both of the Oswegatchie Group, in the 

Northwest Lowlands of the Adirondacks. Age is Proterozoic. 

Ear Peak Member of the Kanayut Conglomerate 

Late Devonian 

Alaska 

Norton basin 

Nilsen, T.H., and Moore, T.E., 1984, Stratigraphic nomenclature for the Upper Devonian 

and Lower Mississippian(?) Kanayut Conglomerate, Brooks Range, Alaska: U.S. 

Geological Survey Bulletin 1529-A, p. A1-A64. 

Type section: Southernmost spur of an east-facing ridge 1.8 km southeast of Ear Peak, east-southeast of Shainin Lake, sees. 13 and 24, 

T. 13 S., R. 5 E., and sec. 18, T. 13 S., R. 6 E., Chandler Lake 

quadrangle, Alaska. 

The Ear Peak Member, here named, is the lowermost of three 

members of the revised Kanayut Conglomerate in the central and 

eastern Brooks Range, Alaska. Was previously mapped as the informal 

lower shale member, lower member, or lower part of the middle 

conglomerate member of the Kanayut. Consists of a sequence of 

red-brown-weathering, fining-upward, stream-channel conglomerate, 

sandstone, and siltstone cycles, averaging 15 m in thickness, alternating 

with flood-plain deposits of shale and siltstone. Paleosols and oxidized 

intervals are common at the tops of the stream-channel cycles. Gradationally overlies and interfingers with the Hunt Fork Shale or the 

Noatak Sandstone; gradationally underlies the Shainin Lake Member 

(new name) of the Kanayut Conglomerate. Thickness at the type section 

is 510 m. Age is Late Devonian based on flora in the Ear Peak and on 

fauna in the underlying units. 
94 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

East Charley Pond Gneiss 

Precambrian 

New York 

Adirondack uplift 

Potter, D.B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: Outcrops in ridges on high hills near East Charley Pond, 

Tupper Lake 15-minute quadrangle, Hamilton County, N.Y. 

Granitic igneous basement rock in the Loon Pond syncline in the Bog 

River synclinorium in the Adirondack Highlands, Hamilton and St. 

Lawrence Counties, N.Y., is here named the East Charley Pond 

Gneiss. Consists of massive, poorly jointed, homogeneous biotitemagnetite-plagioclase-hornblende-quartz-perthite gneiss of uniform 

texture. White- or pink-weathering pink perthite forms nearly half of 

the rock. Pegmatite veins and lenses are parallel to foliation. U nconformably underlies the Little Charley Pond Formation (new name); is 

intruded by the Otter Pond Dioritic Gneiss (new name). Thickness has 

not been determined. Age is Precambrian. 

East Fork Hills Formation 

Early Ordovician to Middle Devonian 

Alaska 

Holitna basin 

Dutro, J.T., Jr., and Patton, W.W., Jr., 1982, New Paleozoic formations in the northern 

Kuskokwim Mountains, west-central Alaska: U.S. Geological Survey Bulletin 1529-H, 

p. H13-H22. 

Type locality: Crest of the East Fork Hills, sec. 14, T. 27 S., R. 25 E., 

Medfra (A-3) quadrangle, Alaska. 

The East Fork Hills Formation, here named, is in the East Fork 

terrane and is mapped along the North Fork of the Kuskokwim River, 

Alaska. Consists of alternating thin bands of gray laminated limestone 

and orange-weathering dolomitic limestone, locally sheared and foliated, and subordinate laminated dolomite, chert, and siliceous siltstone. 

Is interpreted as a deep-water facies, equivalent to the entire shallowwater carbonate sequence of the Nixon Fork terrane, including the 

N ovi Mountain, Telsitna, Paradise Fork, and Whirlwind Creek Formations (all new names). Is in fault contact with the Whirlwind Creek 

Formation and Telsitna Formation along the northwest edge of the 

outcrop belt. Thickness is several hundred meters. Age is Early 

Ordovician to Middle Devonian based on conodonts. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 95 

East Kingston Member of the Port Ewen Formation of the 

Helderberg Group 

Early Devonian 

New York 

Appalachian basin 

Mazzo, C.R., and LaFleur, R.G., 1984, Stratigraphy of the Port Ewen Formation (Lower 

Devonian), eastern New York: Northeastern Geology, v. 6, no. 2, p. 71--82. 

Type section: Roadcut on New York Route 199, 1.02 km west of the 

Kingston-Rhinecliff Bridge across the Hudson River, Kingston, Ulster 

County, N.Y. 

The East Kingston Member is here named the upper of two 

members of the Port Ewen Formation of the Helderberg Group in the 

Silurian-Devonian outcrop belt in eastern New York. Consists of 

medium-gray- to buff-weathering, hackly to massive, laminated, silty, 

cherty claystone containing brachiopod and bryozoan wackestone 

stringers and bedded nodular chert. Overlies the Lake Katrine Member 

(new name) of the Port Ewen Formation; transitionally underlies the 

Glenerie Formation. Thickness at the type section is 21.2 m. Age is 

Early Devonian. 

Edenhouse Member of the Chowan River Formation of the 

Chesapeake Group 

Pliocene 

North Carolina, Virginia 

Atlantic Coast basin 

Blackwelder, B.W., 1981, Stratigraphy of upper Pliocene and lower Pleistocene marine 

and estuarine deposits of northeastern North Carolina: U.S. Geological Survey Bulletin 

1502-B, 16 p. 

Type section: Section 1.4 km upstream from the U.S. Highway 17 

bridge over the Chowan River above Edenhouse, Bertie County, N.C. 

Lower transgressive beds of the Chowan River Formation (new 

name) of the Chesapeake Group in the Coastal Plain of northeastern 

North Carolina and southeastern Virginia are here named the Edenhouse Member. Consists of shallow marine, locally bioturbated, shelly, 

silty sands. Unconformably overlies the Morgarts Beach Member of the 

Yorktown Formation; transitionally to unconformably underlies the 

Colerain Beach Member (new name) of the Chowan River Formation or 

unconformably underlies the James City Formation. Thickness is 3. 0 m 

at the type section. Age is late Pliocene based on coral ages. 
96 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Edgar Member of the Marathon Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Chicago and Northwestern Railroad cut on south side of 

Highway N, NWl/4NEl/4NWl/4 sec. 24, T. 28 N., R. 4 E., Edgar 

7.5-minute quadrangle, Marathon County, Wis. Named for the village 

of Edgar. 

The upper member of the Marathon Formation (new name) in the 

Chippewa Sublobe in southwestern Marathon, northern Wood, and 

eastern Clark Counties, Wis., is here named the Edgar Member, 

following the informal usage of Mode (1976). Consists of yellowish- to 

reddish-brown, calcareous, silty, pebbly loam to clay and silt loam. 

Overlies Precambrian bedrock or the Wausau Member (new name) of 

the Marathon; underlies the Bakerville Member (new name) of the 

Lincoln Formation (new name) or is exposed at the surface. Thickness 

ranges from less than 3 m to 10 m. Age is late Pleistocene (early 

Wisconsinan or older). 

Elkmont Formation 

Middle and Late Ordovician 

Alabama 

Piedmont-Blue Ridge province 

Neathery, T.L., and Drahovzal, J.A., 1985, Lithostratigraphy of Upper Ordovician strata 

in Alabama: Alabama Geological Survey Circular 124, 55 p. 

Type section: Elkmont Quarry, SEl/4SEl/4 sec. 31, T. 1 S., R. 4 W., 

Elkmont 7.5-minute quadrangle, Limestone County, Ala. 

The Elkmont Formation, here named, is in the Cumberland Plateau 

area in northeastern Alabama. Where the characteristic lithology of the 

Inman Formation is missing, the overlying Leipers Limestone is 

indistinguishable from the underlying Catheys Limestone. In the subsurface these combine with the Cannon and Hermitage Formations to 

form one massive lithologic unit in which only the Hermitage is 

recognizable. The lithologic interval from the top of the Hermitage to 

the base of the Sequatchie Formation, where the intervening Cannon, 

Catheys, Inman, and Leipers cannot be separated either lithologically 

or geophysically, is here redefined as the Elkmont Formation. Thickness is 130 ft at the type section. Age is Middle and Late Ordovician. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 97 

Elk Park Plutonic Suite 

Middle Proterozoic 

North Carolina 

Piedmont-Blue Ridge province 

Rankin, D.W., Stern, T.W., McLelland, James, Zartman, R.E., and Odom, A.L, 1983, 

Correlation chart for Precambrian rocks of the eastern United States: U.S. Geological 

Survey Professional Paper 1241-E, p. E1-E18. 

Type locality: None designated. Named for the village of Elk Park, 

Avery County, N.C. (Rankin and others, 1973). 

Subunits: Cranberry Gneiss, Blowing Rock Gneiss, and Wilson 

Creek Gneiss. 

Basement plutonic rocks in northwestern North Carolina, informally 

named the Elk Park plutonic group by Rankin and others (1973), are 

here named the Elk Park Plutonic Suite. Protoliths of this orogenic 

calc-alkaline suite were fine-grained to coarsely porphyritic diorites to 

quartz monzonites. Includes the Cranberry Gneiss of the Blue Ridge 

thrust sheet in northwestern North Carolina and the Blowing Rock and 

Wilson Creek Gneisses in the Grandfather Mountain window. Probably 

correlates with the Max Patch Granite of the Great Smoky Mountains 

and the Grayson Granodiorite Gneiss of Grayson County, Va. Age is 

Middle Proterozoic based on a zircon discordia intercept age of 1,079 

Ma. [The term Elk Park Supersuite is used by Bartholomew and Lewis 

(1984).] 

Ellicott Creek Breccia of the Bertie Group 

late Silurian 

New York, Ontario 

Appalachian basin 

Ciurca, S.J., Jr., 1982, Eurypterids, stratigraphy, Late Silurian-Early Devonian of 

western New York State and Ontario, Canada: New York State Geological Association, 

54th Annual Meeting, field trip guidebook, p. 99-120. 

Type section: Exposures at Ellicott Creek, Williamsville, Erie County, 

N.Y. 

The Ellicott Creek Breccia is here named as one of several waterlimes in the Bertie Group in New York and Ontario. Consists of 

varicolored, banded waterlime rich in eurypterid and cephalopod 

remains. Contains a massive middle unit that is probably the result of 

"reefy" algal masses; variability in thickness of the unit is probably due 

to variation in algal mound development. Overlies the Victor Dolostone 

or Phelps Waterlime; underlies the Scajaquada Formation, all of the 

Bertie Group. Thickness at the type section is 2 .. 3 to 2.5 m. Age is Late 

Silurian. 
98 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Escalante Creek Member of the Dox Formation of the Unkar 

Group 

Middle Proterozoic 

Arizona 

Plateau sedimentary province 

Stevenson, G.M., and Beus, S.S., 1982, Stratigraphy and depositional setting of the upper 

Precambrian Dox Formation in Grand Canyon: Geological Society of America Bulletin, 

v. 93, no. 2, p. 163-173. 

Type section: Exposures along Escalante Creek, eastern Grand Canyon, Vishnu Temple quadrangle, Coconino County, Ariz. 

The Escalante Creek Member, here named, is the lowermost 

member of the Dox Formation of the Unkar Group in the eastern Grand 

Canyon, Ariz. Contains four distinct lithologic units that record transgression and regression of prodeltaic and deltaic basin deposits formed 

in a marginal-marine environment: unit 1, the lowermost, consists of 73 

m of white to grayish-tan, friable, medium-grained quartz sandstone 

that has a basal dark-green to black shale; unit 2 consists of 80 m of 

green to brown shale, mudstone, and sandstone; unit 3 is a cliff-forming 

calcareous sandstone 96 m thick; unit 4, the uppermost, consists of 140 

m of less resistant interbedded brown to grayish siltstone. Conformably 

overlies the Shinumo Quartzite; gradationally underlies the Solomon 

Temple Member (new name) of the Dox. Thickness at the type section 

is 390 m. Age is Middle Proterozoic based on the age of the overlying 

Cardenas Lavas (1.1 Ma). 

Estrella Gneiss 

Precambrian 

Arizona 

Basin and Range province 

Reynolds, S.J., 1985, Geology of the South Mountains, central Arizona: Arizona Bureau 

of Geology and Mineral Technology Bulletin 195, 61 p. 

Type locality: Exposures in the central Sierra Estrella, southwest of 

the South Mountains, Maricopa County, Ariz. 

The Estrella Gneiss, here named, is in the Sierra Estrella, western 

South Mountains, Buckeye Hills, and White Tank Mountains, Ariz., and 

includes many exposures of high-grade metamorphic rocks south and 

west of Phoenix that are not easily correlated with other named 

Precambrian rocks of Arizona. Crops out as serrated ridges of darkcolored, blocky metamorphic rocks formed by mostly amphibolite-facies 

metamorphism of plutonic, volcanic, and metasedimentary protoliths, 

subsequently overprinted by Tertiary mylonitization. Consists 

of quartz-feldspathic gneiss, amphibolite, biotitic gneiss, granitic 

gneiss, migmatite, mica schist, and rare quartz-rich rocks that have 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 99 

crystalloblastic foliation. Is intruded by the Komatke Granite, South 

Mountains Granodiorite, and Telegraph Pass Granite (all new names). 

Age is Precambrian. 

Etivluk Group 

Pennsylvanian, Permian, Triassic, and Early and Middle jurassic 

Alaska 

Arctic Foothills province 

Mull, C.G., Tailleur, I.L., Mayfield, C.F., Ellersieck, Inyo, and Curtis, S., 1982, New 

upper Paleozoic and lower Mesozoic stratigraphic units, central and western Brooks 

Range, Alaska: American Association of Petroleum Geologists Bulletin, v. 66, no. 3, 

p. 348-362. 

Type locality: Composite of the Siksikpuk Formation, sees. 21 and 23, 

T. 12 S., R. 1 E., and the Otuk Formation, sec. 31, T. 10 S., R. 16 W., 

Alaska. Named for the Etivluk River, a tributary of the Colville River, 

western Endicott Mountains, Howard Pass quadrangle. 

Subunits: Siksikpuk Formation, Otuk Formation and its Blankenship Member. 

The Etivluk Group, here named, is in the De Long and Endicott 

Mountains in the Brooks Range, and adjacent northern foothills, 

Alaska, where it is present only on allochthonous sheets. Includes the 

lower Siksikpuk Formation and the upper Otuk Formation (new name) 

and its Blankenship Member (new name). Formations are thin, are not 

well exposed, and consist of thin-bedded chert, shale, silicified shale, 

and limestone. Disconformably or gradationally overlies the Lisburne 

Group; disconformably underlies Lower Cretaceous shale, graywacke, 

and conglomerate. Age of the Siksikpuk is Pennsylvanian, Permian, and 

Early Triassic; the Otuk is Early Triassic to Middle Jurassic; the 

Blankenship is Early and Middle Jurassic based on fossils. 

Etowah Formation of the Great Smoky Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures at the confluence of the Etowah and Little 

Rivers, South Canton 7.5-minute quadrangle, Cherokee County, Ga. 

The basal and oldest unit of the Murphy synclinorium in the Greater 

Atlanta region is here named the Etowah Formation of the Great 

Smoky Group. Consists of interlayered metasandstones and metaargillite containing lenses of calc-silicate granofels. Gradationally underlies the Sweetwater Creek Formation (new name) of the Great Smoky 
100 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Group; the boundary is placed where coarse clastics constitute less than 

50 percent of the unit. Age is Late Proterozoic and (or) early Paleozoic. 

Fairburn Member of the Clarkston Formation of the Atlanta 

Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Outcrops in and around Fairburn, Fairburn quadrangle, 

Fulton County, Ga. 

The Fairburn Member, here named, is the lower member of the 

Clarkston Formation (new name) of the Atlanta Group (new name) in 

the area from East Point to Palmetto, Ga., in the northwest limb of the 

Newnan-Tucker synform. Consists of crinkled garnet schist locally 

containing small red garnets. Sharply and conformably overlies· the 

Stonewall Formation (new name) of the Atlanta Group; gradationally 

underlies the Tar Creek Member (new name) of the Clarkston. Thickness ranges from 400 to 1, 000 m. Age is Late Proterozoic and (or) early 

Paleozoic. 

Fairdale Till Member of the Glasford Formation 

Pleistocene (Illinoian) 

Illinois 

Wisconsin arch 

Kempton, J.P., and Berg, R.C., 1985, Stratigraphy of the Oregon Till Member silty facies 

and Fairdale Till Member: Illinois Geological Survey, Midwest Friends of the Pleistocene, 32d field conference, guidebook 19, p. 132-154. 

Type section: Fairdale Quarry Section, on Fairdale Road 1.6 km south 

of Fairdale, center sec. 30, T. 42 N., R. 3 E., De Kalb County, Ill. 

The recognition that the Esmond Till Member is a unit of the 

Illinoian Glasford Formation rather than of the Wisconsinan Wedron 

Formation has left three unnamed till members below the Esmond 

Member. The middle member, here named the Fairdale Till Member of 

the Glasford Formation, occurs in De Kalb, Boone, Ogle, and Kane 

Counties, Ill., and is a yellowish-brown, sandy loam diamicton. Overlies 

the Herbert Till Member (new name) and underlies the Oregon Till 

Member (new name), both of the Glasford Formation, in a stratigraphic 

relationship similar to that between the Argyle and Capron Till 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 101 

Members of the Winnebago Formation, with which the diamictons were 

previously correlated. Thickness is less than 10 m. Age is middle 

Pleistocene (Illinoian). 

Faith Chert Member of the Tenmile Creek Formation of the 

Stanley Group 

late Mississippian 

Oklahoma 

Ouachita tectonic belt province 

Pitt, W.D., Fay, R.O., Wilson, L.R., and Curiale, J.A., 1982, Geology of Pushmataha 

County, Oklahoma: Eastern New Mexico University Studies in Natural Sciences 

Special Publication 2, 101 p. 

Type locality: Outcrop 0.4 mi southeast of Black Knob Ridge on the 

north side of Oklahoma Highway 7, NWl/4SEl/4NWl/4 sec. 24, T. 2 S., R. 

11 E., Atoka County, Okla. Named for the Faith Tabernacle Church, 

1,000 ft northwest of the outcrop. 

The Faith Chert Member, here named, is in the lower part of the 

Tenmile Creek Formation of the Stanley Group in the Ouachita Mountains in Atoka County, southeastern Oklahoma. Consists of bedded 

chert and siliceous shale. Lies about 1,200 ft above the base of the 

Tenmile Creek and is considered to be slightly higher than the Albion 

Creek Chert Member (new name) of the Tenmile Creek in Pushmataha 

County. Thickness is 90ft. Age is Late Mississippian. 

Fall Brook Coral Bed of the Windom Shale Member of the 

Moscow Formation of the Hamilton Group 

Middle Devonian 

New York 

Appalachian basin 

Baird, G. C., and Brett, C. C., 1983, Regional variation and paleontology of two coral beds 

in the Middle Devonian Hamilton Group of western New York: Journal of Paleontology, v. 57, no. 3, p. 417-446. 

Type section: Exposures along Fall Brook, 0.4 mi east of New York 

Route 20A-39 overpass, 1.4 mi south of Geneseo, Geneseo 7.5-minute 

quadrangle, Genesee County, N.Y. 

The coral-rich unit in the upper part of the Windom Shale Member 

of the Moscow Formation of the Hamilton Group is here named the Fall 

Brook Coral Bed. Extends from eastern Genesee County to Seneca 

County, N.Y. In the Genesee Valley area the bed contains large corals 

and other invertebrate fossils densely packed in a soft mudstone matrix. 

To the east, the bed thickens and the fossil content lessens; east 

of Seneca Lake, the unit cannot be identified. Separated from the 

underlying Smoke Creek Bed (new name) by 2 to 5 m of gray to black 
102 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

shale, the Ambocoelia? praeumbona zone. Underlies the Spirifercoralline zone of Stover (1956), here termed the Taunton Beds (new 

name). Maximum thickness is 1.5 m. Age is Middle Devonian. 

Fall Canyon Tuff 

Oligocene 

New Mexico 

Basin and Range province 

Ratte, J.C., 1981, Geologic map of the Mogollon quadrangle, Catron County, New Mexico: 

U.S. Geological Survey Geologic Quadrangle Map GQ-1557, scale 1:24,000. 

Type section: Wl/2 sec. 23, T. 13 S., R. 17 W., Shelley Peak quadrangle, 

Grant County, N. Mex. Named for Fall Canyon, south flank of Shelley 

Peak, Shelley Peak quadrangle, Catron County. 

The Fall Canyon Tuff, here named, is in the Basin and Range 

province in New Mexico. Consists of high-silica, phenocryst-rich rhyolite ash-flow tuff containing phenocrysts of sanidine cryptoperthite, 

quartz, and sodic plagioclase. Also contains biotite and accessory 

opaque oxide, zircon, sphene, oxyhornblende, and apatite. Overlies and 

underlies unnamed lava flows. Thickness at the type section is 150 m. 

Age is Oligocene based on a zircon fission-track age of 29.4 Ma. 

Farmers Creek Member of the Hopkinton Dolomite 

Early Silurian (llandoverian) 

Iowa 

Iowa shelf 

Johnson, M.E., 1983, New member names for the Lower Silurian Hopkinton Dolomite of 

eastern Iowa: Iowa Academy of Science Proceedings, v. 90, no. 1, p. 13-18. 

Type section: Schwenker quarry, near the center of Farmers Creek 

Township, 4. 75 km west-northwest of Fulton, NEl/4SW1f4 sec. 16, 

T. 85 N., R. 2 E., Jackson County, Iowa. 

Previously divided on the basis of paleontologic units, the Hopkinton 

Dolomite is here divided into lithologic members to facilitate interregional correlations based on sea-level curves. The 12-m-thick rock 

unit corresponding to the Cyclocrinites Beds of the Hopkinton is here 

named the Farmers Creek Member in eastern Iowa and may also be 

traced to northwestern Illinois. Consists of tan, massive, very finely 

crystalline to micritic dolomite. The pentamerid brachiopod Harpidium 

maquoketa predominates the fauna of the upper two-thirds of the 

member; the green alga Cyclocrinites occurs throughout the entire unit. 

Overlies the Marcus Member of the Hopkinton; underlies the Picture 

Rock Member (new name) of the Hopkinton. Age is Early Silurian 

(Llandoverian). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 103 

Farmersville Member of the Pecan Gap Formation of the 

Taylor Group 

Late Cretaceous (Campanian) 

Texas 

Ouachita tectonic belt province 

McNulty, C.L., Brezina, J.L., Dawson, W.C., and Maluf, F.W., 1981, Emendation of the 

Pecan Gap Chalk (Campanian) in northeast Texas: Gulf Coast Association of Geological 

Societies Transactions, v. 31, p. 353-358. 

Type locality: Hays Hills, an area of 1.0 sq mi located about 2 mi 

northwest of Farmersville, Collin County, Tex. 

The Farmersville Member, here named, of the Pecan Gap Formation, revised, of the Taylor Group, was proposed informally by Brezina 

(197 4) and published without formal definition by Dawson, Reaser, and 

Richardson (1978). Occurs only in the Hays Hills, Collin County, Tex., 

and is a lenticular body believed to be of storm-wave and tidal origin. 

Consists of thin-bedded glauconitic quartz sandstone alternating with 

bioclastic calcite. Disconformably overlies silty marl, possibly the 

Ozan Formation. Relationship to other units is uncertain; may correlate 

with the Wolfe City Formation or the Rockwall Member (new name) of 

the Pecan Gap. Thickness is 32 to 60 ft. Age is Late Cretaceous 

(Campanian). 

Fawn Creek Member of the Scotch Grove Formation 

Early Silurian (Wenlockian) 

Iowa 

Iowa shelf 

Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River fault zone and 

the structural and stratigraphic framework of eastern Iowa: Iowa Geological Survey 

Technical Information Series 13, 126 p. 

Type locality: Exposures along both sides of Wapsipinicon River 

upstream from the mouth of Fawn Creek, Wapsipinicon State Park, 

NI/2SE1/4 sec. 11, T. 84 N., R. 4 W., Jones County, Iowa. Reference core 

section: NWlf4NWlf4SWlf4NElf4 sec. 20, T. 82 N., R. 8 W., Linn County, 

Iowa. 

The informal Fawn Creek facies of Witzke (1981) is here named the 

Fawn Creek Member in the middle and upper Scotch Grove Formation 

(new name) in eastern Iowa. Consists of horizontally bedded, porous, 

noncherty, abundantly fossiliferous dolomite containing crinoid-moldic 

debris. Overlies and is replaced laterally to the east and west by the 

Buck Creek Quarry Member (new name) of the Scotch Grove, reassigned from the revised Hopkinton Formation; is replaced laterally to 

the north by the Palisades-Kepler Member (new name) of the Scotch 

Grove; underlies the Waubeek Member (new name) of the Scotch 
104 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Grove, or is a lateral facies equivalent of the Waubeek Member where 

it underlies the Anamosa Member of the Gower Formation. Thickness is 

commonly 60 ft but attains 97 ft. Age is Early Silurian (early and middle 

Wenlockian). 

Fayetteville Phyllite of the Sylacauga Marble Group 

Early and Middle Cambrian 

Alabama 

Piedmont-Blue Ridge province 

Tull, J.F., 1985, Stratigraphy of the Sylacauga Marble Group, in Tull, J.F., and others, 

eds., Early evolution of the Appalachian miogeocline: upper Precambrian-lower 

Paleozoic stratigraphy of the Talladega Slate Belt: Alabama Geological Society 

guidebook, 22d annual field trip, Nov. 22-23, 1985, p. 21-26. 

Type locality: Exposures near the village of Fayetteville, southwest 

Talladega County, Ala. 

The Fayetteville Phyllite of the Sylacauga Marble Group, as revised 

by Tull (1982) and here named, is in the southwestern part of the 

Talladega slate belt, Alabama. Consists of tan to maroon, calcareous 

metasiltstone, in places finely laminated and interbedded with metasandstone, and bounded above and below by thick carbonate units with 

which it is gradational. Overlies the Jumbo Dolomite and underlies the 

Shelvin Rock Church Formation (new name), both of the Sylacauga 

Marble Group. Correlates with part of the Rome Formation of Early 

and Middle Cambrian age. 

Fence Lake Formation 

Miocene 

New Mexico 

San juan basin 

McLellan, Marguerite, Robinson, Laura, Haschke, Laura, Carter, M.D., and Medlin, 

Antoinette, 1982, Fence Lake Formation (Tertiary), west-central New Mexico: New 

Mexico Geology, v. 4, no. 4, p. 53-55. 

Type section: Exposures in sec. 1, T. 4 N., R. 18 W., southwest Cibola 

County, N. Mex. Named for the community of Fence Lake, Cibola 

County. 

The Fence Lake Formation, here named, is in west-central New 

Mexico and was formerly mapped as the upper member of the Bidahochi 

Formation by Repenning and Irwin (1954). Includes a lower unit, the 

informal Fence Lake gravel of Marr (1956), that contains a coarse 

conglomerate consisting of 41 ft of subrounded to subangular granules, 

pebbles, cobbles, and boulders of basalt, rhyolite, and other fine- to 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 105 

coarse-grained, poorly sorted volcanic rocks and an upper unit consisting of 180 ft of grayish-pink, poorly sorted, very fine- to coarse-grained, 

calcareous sandstone containing lenses of conglomerate. Unconformably 

overlies the Upper Cretaceous Moreno Hill Formation (new name); 

upper unit remains at the surface only where it has been protected from 

erosion by a lens of conglomerate that is partly concealed by eolian sand. 

Similarity of clasts in the Fence Lake conglomerates to the rocks of the 

Datil Group in the Datil Mountains to the southeast suggests that the 

Fence Lake is an alluvial fan derived from rocks of the Datil Mountains. 

Thickness ranges from 60 ft to 221 ft at the type section. Age is Miocene 

based on clasts of Oligocene basaltic andesites and rhyolites of the 

Datil-Mogollon area. 

Fenstermaker Wash Formation 

Middle and Late Devonian 

Nevada 

Great Basin province 

Hose, R.K., Armstrong, A.K., Harris, A.G., and Mamet, B.L., 1982, Devonian and 

Mississippian rocks of the northern Antelope Range, Eureka County, Nevada: U.S. 

Geological Survey Professional Paper 1182, 19 p. 

Measured sections: Lower part: SEl/4 sec. 16, T. 16 N., R. 51 E.; 

NE1/4NE1/4 sec. 21, T. 15 N., R. 51 E.; and NEl/4NE1/4 sec. 20, T. 15 N., 

R. 51 E. Middle and upper parts: NEI/4 sec. 20 and NWI/4 sec. 21, 

T. 15 N., R. 51 E., northern Antelope Range, Eureka County, Nev. 

Named for Fenstermaker Wash, northeast and east of the northern part 

of the Antelope Range. 

The Fenstermaker Wash Formation, here named, is in the northern 

Antelope Range, Nev. Is divided into a lower part, 80 to 183m thick, 

consisting of medium-gray to light-brownish-gray, massive, medium- to 

coarse-grained, peloid-echinoderm-coral, stromatoporoid-brachiopod 

packstone and wackestone; a middle part, 42 m thick, consisting of 

pale-yellowish-orange, siliceous, laminated siltstone and claystone; and 

an upper part, 60 m thick, consisting of medium-gray, crossbedded, 

peloid-mudlump packstone to grainstone that forms a massive cliff. 

Contains a fauna suggestive of intertidal, deep water, and subtidal 

deposition. Conformably and sharply overlies the Denay Formation; 

sharply underlies the Davis Spring Formation (new name), representing an unconformity of considerable magnitude. Correlates temporally 

with the Bay State Dolomite and Devils Gate Limestone in the southern 

Fish Creek Range, 10 km to the east. Age is Middle and Late Devonian 

based on conodonts. 
106 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Ferguson Hill Member of the Sunrise Formation of the 

Volcano Peak Group 

Early Jurassic (Hettangian and Sinemurian) 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598-1608. 

Type locality: Exposures on the east flank of Ferguson Hill, west side 

of Muller Canyon, Gabbs Valley Range, Mineral County, Nev. This 

section is proposed as the stratotype for the Triassic-Jurassic System 

boundary. 

The lower two units, units 5 and 6, of Muller and Ferguson (1939) of 

the Sunrise Formation are here named the Ferguson Hill Member of the 

now revised Sunrise Formation of the Volcano Peak Group (new name) 

in the Gabbs Valley Range in west-central Nevada. Includes three 

lithologies: a lower silty limestone unit consisting of 5 m of black to gray 

thin- to medium-bedded, silty to sandy limestone and siltstone; a cherty 

limestone unit consisting of 35 m of brown, bluish-gray, or gray 

medium- to thick-bedded chert-rich limestone; and an upper oolitic 

limestone unit consisting of 15 m of gray or orange-brown oolitic 

limestone and siltstone. Conformably overlies the Muller Canyon Member (new name) of the Gabbs Formation of the Volcano Peak Group; 

conformably underlies the Five Card Draw Member (new name) of the 

Sunrise Formation. Age is Early Jurassic (Hettangian and Sinemurian) 

based on fossils. 

Fishburne Formation 

Eocene (Ypresian) 

South Carolina 

Atlantic Coast province 

Gohn, G.S., Hazel, J.E., Bybell, L.M., and Edwards, L.E., 1983, The Fishburne 

Formation (lower Eocene), a newly defined subsurface unit in the South Carolina 

Coastal Plain: U.S. Geological Survey Bulletin 1537-C, p. C1-C16. 

Type section: Clubhouse Crossroads corehole Number 1 (CCI), depth 

interval 416-440 ft, Dorchester County, S.C. Named for Fishburne 

Creek in southern Dorchester County. 

A thin, laterally persistent unit in the subsurface of the Coastal 

Plain southwest of the Charleston-Summerville area, South Carolina, 

assigned to the upper part of the Black Mingo Formation by Gohn and 

others (1977) and designated informal unit Te1 by Gohn and others 

(1978), is here named the Fishburne Formation. [The Fishburne Formation at the type section is described as unnamed Y presian strata of 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 107 

the Black Mingo Group by Van Nieuwenhuise and Colquhoun (1982).] 

Consists of greenish-gray to pale-olive, finely crystalline, nodular, 

glauconitic, clayey, microfossil-mollusk limestone that has an apparent 

lack of bedding due to bioturbation. Sharply overlies the Black Mingo 

Formation; sharply underlies the Moultrie Member of the Santee 

Limestone. Thickness at the type section is 24 ft. Age is early Eocene 

(Ypresian). 

Fisher Creek Formation 

Mississippian 

Tennessee 

Appalachian basin 

Brent, W.B., 1982, Mississippian stratigraphy of Greendale and Newman Ridge synclines 

and Middle Ordovician nomenclature in upper east Tennessee: Tennessee Division of 

Geology Report of Investigations 41, 37 p. 

Type section: Along the east side of Fisher Creek near Fisher Creek 

School, south of Looneys Gap in Clinch Mountain, Looneys Gap 

quadrangle, Hawkins County, Tenn. 

The Fisher Creek Formation, informally named by Sanders (1952), 

is here named. These Mississippian strata in the Greendale syncline in 

Hawkins and Grainger Counties, Tenn., were previously named the 

Newman Limestone by Hardeman and others (1966) but are isolated 

from the type Newman Limestone in the Newman Ridge syncline. 

Consists of limestone and subordinate sandstone and is subdivided into 

a lower member, the informal Fisher Creek formation of Sanders 

(1952), a middle sandstone member, the informal Alumwell sandstone of 

Sanders (1952), and an upper member, the informal Marshall Creek 

formation of Sanders (1952). Sharply overlies the Gilliam Creek Limestone (new name); sharply underlies the Fido Sandstone. Thickness is 

450 m. Age is Mississippian. 

Fisher Spring Sandstone Member of the Ridge Route 

Formation of the Ridge Basin Group 

Miocene 

California 

los Angeles basin 

Link, M. H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J.C., and Link, M.H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5-12. 

Type section: Outcrops adjacent to Fisher Spring along the east side of 

Interstate Highway I -5 between Paradise Ranch and Whitaker Peak 

road, about 12 km north of Castaic, Los Angeles County, Calif. 
108 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Fisher Spring Sandstone Member, here named, is in the Ridge 

Route Formation of the Ridge Basin Group in the central Ridge basin, 

Los Angeles County, Calif., and is one of five major clastic tongues of 

the Ridge Route Formation that cross the basin. Consists of lightbrown medium-grained, arkosic sandstone interbedded with mudstone 

and conglomerate and contains freshwater mollusk, ostracode, and 

vertebrate fossils suggestive of nonmarine lacustrine-fluvial conditions. 

Conformably overlies the Paradise Ranch Shale Member (new name), 

and conformably underlies the Osito Canyon Shale Member (new name), 

both of the Peace Valley Formation, redefined. Interfingers with the 

Violin Breccia to the southwest and with the Ridge Route undivided to 

the northeast. Lateral extent is 4,310 m. Thickness is 740 mat the type 

section and ranges from 100m to 1,300 m. Age is late Miocene based on 

stratigraphic position. 

Fite Ranch Sandstone Member of the Tres Hermanos Formation 

Late Cretaceous (Turonian) 

New Mexico 

Orogrande basin 

Hook, S.C., Molenaar, C.M., and Cobban, W.A., 1983, Stratigraphy and revision of 

nomenclature of upper Cenomanian to Turonian (Upper Cretaceous) rocks of westcentral New Mexico: New Mexico Bureau of Mines and Mineral Resources Circular 

185, p. 7-28. 

Type section: SE1/4SE1/4 sec. 8 and NE1/4NE1/4 sec. 17, T. 5 S., R. 2 E., 

San Antonio quadrangle, Socorro County, N. Mex. Named for Fite 

Ranch, 1 mi south of Carthage, Socorro County. 

The Fite Ranch Sandstone Member, here named, is the upper 

member of the Tres Hermanos Formation, raised in stratigraphic rank, 

in the Orogrande basin, New Mexico. Consists of light-gray to brown 

fine-grained, fossiliferous sandstone and minor amounts of siltstone. 

Sandstone is poorly bedded, burrowed, bioturbated, moderately to well 

sorted, and flat bedded or ripple marked and represents coastal barrier 

deposits. Overlies the Carthage Member (new name) of the Tres 

Hermanos; underlies the D-Cross Tongue of the Mancos Shale. 

Equivalent to the Juana Lopez Member of the Mancos Shale. Locally 

absent, and thickness is 75 ft at the type section but is thin in most 

places. Age is Late Cretaceous (early late Turonian). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 109 

Five Card Draw Member of the Sunrise Formation of the 

Volcano Peak Group 

Early Jurassic (Sinemurian) 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598--1608. 

Type locality: Exposures along Five Card Draw, Gabbs Valley Range, 

Mineral County, Nev. 

Unit 7 of Muller and Ferguson (1939) of the Sunrise Formation is 

here named the Five Card Draw Member of the now revised Sunrise 

Formation of the Volcano Peak Group (new name) in the Gabbs Valley 

Range in west-central Nevada. Consists of fine-grained siliceous siltstone and mudstone in the lower part and dark-gray to black mudstone 

grading to calcareous siltstone in the upper part. Conformably overlies 

the Ferguson Hill Member (new name) of the Sunrise; conformably 

underlies the New York Canyon Member (new name) of the Sunrise. 

Thickness is 100m. Age is Early Jurassic (Sinemurian) based on fossils. 

Floris Formation of the Cherokee Group of the Des Moines 

Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type locality: Exposures in a series of roadcuts along a north-south 

road on the east edge of sec. 29, T. 72 N., R. 13 W., east of Ottumwa, 

Wapello County, Iowa. Named for the community of Floris in northeastern Davis County. 

Subunits: Laddsdale Member, Carruthers Coal Member. 

The Floris Formation is one of four newly named formations in the 

Cherokee Group of the Des Moines Supergroup in southeastern and 

south-central Iowa. Consists of unfossiliferous shale and sandstone 

characterized by thick channel-fill sequences and the absence of widely 

traceable beds in the lower portion. Six coal beds in the lower Floris, 

named the Laddsdale Member (new name), are lenticular and discontinuous and range from 1 in to 2.2 ft in thickness. The Laddsdale 

Member is frequently overlain by a lenticular fossiliferous limestone 

historically referred to as the informal Laddsdale limestone in Iowa and 
110 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

correlated with the Seville Limestone of Illinois. The lenticular nature 

and lack of distinctive fauna make the correlation of the limestone with 

the Seville questionable, and it is given no formal name. The Carruthers 

Coal Member (new name), in the upper Floris, is a single thin, 

persistent coal, 1.4 ft thick. Contact with the underlying Kalo Formation (new name) of the Cherokee Group is placed at the base of the 

lowermost coal of the Laddsdale Member; underlies the Whitebreast 

Coal Member (new name) of the Swede Hollow Formation (new name) 

of the Cherokee. Thickness is 100 ft at the type section and ranges from 

65 to 190ft. Age is Middle Pennsylvanian (Desmoinesian). 

Flume Ridge (Flume) Formation 

late Silurian and Early Devonian 

New Brunswick, Maine 

New England province 

Ruitenberg, A.A., 1967, Stratigraphy, structure and metallization Piskahegan-Rolling 

Dam area (northern Appalachians, New Brunswick, Canada): Leidse Geologische 

Mededelingen, v. 40, p. 79-120. 

Type locality: Exposures at Flume, along the Magaguadavic River, 

Charlotte County, New Brunswick, Canada. 

Rocks named the Canoose Formation of MacKenzie (1940) and the 

Pale Argillite Division of the Charlotte Group of MacKenzie and Alcock 

(1960) are here named the Flume Formation. Occurs in Charlotte 

County, N.B., and westward into Maine. Consists of gray-green, sandy 

phyllite and slate. Interbedded with the underlying Waweig Formation 

(new name) and Digdeguash Formation (new name). Age is Late 

Silurian and Early Devonian based on fossils in the W aweig and 

pre-Mississippian deformation. 

Ruitenberg, A.A., 1972, Metallization episodes related to tectonic evolution, Rolling Dam 

and Mascarene-Nerepis belts, New Brunswick: Economic Geology, v. 67, p. 434-444. 

The Flume Formation of Ruitenberg (1967) is here mapped as the 

Flume Ridge Formation. [The name Flume Ridge is used in all 

subsequent references to the unit.] 

Folsomville Member of the Petersburg Formation 

Middle Pennsylvanian 

Indiana 

Illinois basin 

Eggert, D.L., 1982, A fluvial channel contemporaneous with deposition of the Springfield 

Coal Member (V), Petersburg Formation, northern Warrick County, Indiana: Indiana 

Department of Natural Resources, Geological Survey, Special Report 28, p. 1-20. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 111 

Type section: Final cuts in former surface mines near Folsomville, 

SW1/4NE1/4 sec. 7, T. 5 S., R. 7 W., and NW1/4SW1/4 sec. 12, T. 5 S., 

R. 8 W., northern Warrick County, Ind. 

Clastic beds that split the Springfield Coal Member (V) of the 

Petersburg Formation into two or more coal seams in northern Warrick 

County, Ind., are here named the Folsomville Member of the Petersburg. Represents a fluviochannel system that was partly contemporaneous with peat deposition. Consists of rash, gray mudstone, siltstone, 

and sandstone, which is crossbedded and coarser grained in the center 

of the channel. Where the upper seam of the coal is missing, the top of 

the Folsomville is the top of the Petersburg. Thickness attains 40 ft; 

width ranges from 1 to 4 mi. Age is Middle Pennsylvanian. 

Ford Member of the Bell Canyon Formation of the Delaware 

Mountain Group 

late Permian (Guadalupian) 

Texas, New Mexico 

Permian basin 

Winner, Phil, 1985, Type section for the uppermost Bell Canyon Formation in the central 

Delaware basin of West Texas: West Texas Geological Society Bulletin, v. 24, no. 7, 

p. 7-10. 

Type section: Gulf J.R. Grandin Number 1 well, sonic-gamma ray log, 

SEl/4 sec. 33, Block 29 PSL Survey, Loving County, Tex. [Possibly 

named for the Geraldine Ford field, Culberson and Reeves Counties, 

Tex.] 

The Ford Member, here named, is in the upper Bell Canyon 

Formation of the Delaware Mountain Group in the central Delaware 

basin of Texas and New Mexico. Was previously designated the 

informal unranked Ford siltstone by Nottingham (1960) and the Ford 

shale member by Grauten (1965). Consists of silty, calcareous shale that 

has relatively tight porosity and is defined as the first significant shaley 

zone above the base of the Olds Member (new name) of the Bell Canyon. 

Is regionally extensive but is difficult to correlate on a regional basis, 

especially where the overlying informal R3 sand of the Ramsey Member 

(new name) of the Bell Canyon is tightly cemented. Thickness is about 

10 ft. Age is Late Permian (Guadalupian). 

Forge Creek Suite of the Elk Park Supersuite 

Middle Proterozoic 

Tennessee, North Carolina, Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 
112 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type locality: None designated. Named for Forge Creek, lat 36°28' N., 

long 8r44' W., Baldwin Gap 7.5-minute quadrangle, Johnson County, 

Tenn. 

Subunits: Watauga River Gneiss (North Carolina, Tennessee), Comers 

Gneiss (Virginia), Grayson Gneiss (Virginia). 

The Forge Creek Suite, here named, is in the Elk Park Supersuite 

as used by Bartholomew and Lewis (1984) in the Watauga massif in the 

Blue Ridge in Tennessee, North Carolina, and Virginia. Includes the 

Watauga River Gneiss (new name) in North Carolina and Tennessee 

and the Comers and Grayson Gneisses in Virginia. Biotite dioritoid 

forms the coarse-grained Grayson Gneiss core facies. Medium-grained 

biotite granitoid forms the marginal Comers Gneiss facies that is 

gradational into granitoid of the Watauga River Gneiss. Age is Middle 

Proterozoic based on a rubidium-strontium age of 1, 175 Ma. 

Foster Formation 

Early and Middle Ordovician (Canadian, Whiterockian) 

Michigan 

Michigan basin 

Fisher, J.H., and Barratt, M.W., 1985, Exploration in the Ordovician of the central 

Michigan basin: American Association of Petroleum Geologists Bulletin, v. 69, no. 12, 

p. 2065-1076. 

Type section: Brazos-Sun-Superior State Foster Number 1 well, depth 

interval11,478-12,996 ft, sec. 28, T. 23 N., R. 2 E., Ogemaw County, 

Mich. 

The Foster Formation, here named, is in the subsurface of the 

central Michigan basin. Consists of dark-gray dolomitic siltstone, black 

shale, and dark-gray dolostone containing thinly interbedded sandstone, limestone, and anhydrite. Contorted bedding and bioturbation 

are common. Transitionally overlies the Cambrian Trempealeau Formation; gradationally underlies the Bruggers Formation (new name), 

and the contact is placed arbitrarily below the lowest thick sandstone. 

Thickness is 1,578 ft at the type section. Age is Early and Middle 

Ordovician (Canadian, Whiterockian) based on conodonts. 

Four-Mile Village Member of the Intracoastal Formation 

Pliocene 

Florida 

South Georgia-North Florida sedimentary province 

Clark, M.W., and Schmidt, Walter, 1982, Shallow stratigraphy of Okaloosa County and 

vicinity, Florida: Florida Bureau of Geology, Report of Investigations, no. 92, 51 p. 

Type section: Coffeen Number 1 (W-8865) core, depth interval211-269 

ft, NEl/4NEl/4 sec. 35, T. 2 S., R. 21 W., near the town of Four-Mile 

Village, southwest Walton County, Fla. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 113 

The Four-Mile Village Member of the Intracoastal Formation, here 

named, is in Walton and Okaloosa Counties, Fla. Consists of dark, 

weathered-looking, unconsolidated to indurated, massive bedded, calcareous, microfossiliferous, slightly arenaceous, glauconitic, phosphoritic sand or sandstone. Forms a low angle, wedge-shaped tongue in the 

center of the Intracoastal Formation. Thickness at the type section is 58 

ft. Age is Pliocene based on planktonic foraminifera. 

Foxhollow Member of the Walworth Formation 

Pleistocene (Wisconsinan) 

Wisconsin, Illinois 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Test hole Number 671 of Fricke (1976), 5 km east of Beloit 

on the east side of the country road north of old Highway 15, 

NEl/4SEl/4NEl/4 sec. 33, T. 1 N., R. 13 E., Shopiere 7.5-minute 

quadrangle, Rock County, Wis. Named for the town of Foxhollow, Rock 

County. 

The Foxhollow Member of the Walworth Formation (new name) is 

here named following the informal usage of Fricke (1976). Occurs in 

south-central Wisconsin east of Rock River and south of Turtle Creek 

and in part of northern Illinois. Consists of gray pebbly, silty, clayey till 

and contains wood fragments. Overlies pre-Pleistocene rocks; sharply 

underlies the Aliens Grove Member (new name) of the Walworth. Age 

is Pleistocene (early Wisconsinan or older). 

Foxtown Member of the Buttermilk Falls Limestone 

Middle Devonian 

Pennsylvania 

Appalachian basin 

Epstein, J.E., 1984, Onesquethawan stratigraphy (Lower and Middle Devonian) of 

northeastern Pennsylvania: U.S. Geological Survey Professional Paper 1337, 35 p. 

Type section: Exposures in railroad cut of Erie-Lackawanna Railroad, 

nearly 1 mi south of the East Stroudsburg Post Office, Stroudsburg 

7.5-minute quadrangle, Monroe County, Pa. Named for Foxtown Hill 

on Godfrey Ridge along U.S. Highway 611. 

The Foxtown Member, here named, is the lower of three mappable 

members of the Buttermilk Falls Limestone on Godfrey Ridge, Monroe 

County, Pa. Consists of wavy, irregularly bedded and lenticular, 

medium-gray, fine-grained, fossiliferous, cherty limestone in 1-in.- to 

2-ft-thick bed's, interbedded with shale, siltstone, and chert. Fossils 
114 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

include crinoid columnals in the lower half of the member and brachiopods and ostracodes. Abruptly overlies the Schoharie Formation; 

transitionally underlies the McMichael Member (new name) of the 

Buttermilk Falls. Thickness is 82 ft. Age is Middle Devonian. 

Freel Peak Granodiorite 

late Cretaceous 

California, Nevada 

Sierra Nevada province 

Armin, R.A., and John, D.A., 1983, Geologic map of the Freel Peak 15-minute 

quadrangle, California and Nevada: U.S. Geological Survey Miscellaneous Investigation Series Map I-1424, scale 1:62,000. 

Type locality: Exposures at Armstrong Pass, El/2 sec. 1, T. 11 N., R. 18 

E., Freel Peak 15-minute quadrangle, El Dorado and Alpine Counties, 

Calif. Named for Freel Peak, 2 mi north of Armstrong Pass, sec. 25, 

T. 12 N., R. 19 E. 

Intrusive rocks exposed in the central part of the Freel Peak 

quadrangle, central Sierra Nevada, California and Nevada, are here 

named the Freel Peak Granodiorite. Consists of light-gray, mediumgrained, biotite granodiorite containing distinctive quartz aggregates, 

potassium feldspar phenocrysts, and ragged biotite flakes. A pinkishorange to gray porphyritic body exposed north of Jobs Peak is regarded 

as a variant of the Freel Peak Granodiorite. Intrudes the quartz diorite 

of Jobs Canyon; is intruded by the tonalite west of Waterhouse Peak, 

the Burnside Lake Adamellite, and the Bryan Meadow Granodiorite 

(new name). Age is Late Cretaceous based on potassium-argon ages of 

93.2 and 82.9 Ma. 

Frenchman Flat Sandstone Member of the Ridge Route 

Formation of the Ridge Basin Group 

Miocene 

California 

los Angeles basin 

Link, M.H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J.C., and Link, M.H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5--12. 

Type section: Outcrop along California Highway 99 near Frenchman 

Flat, about 15 km north of Castaic, Los Angeles County, Calif. 

The Frenchman Flat Sandstone Member, here named, is in the 

Ridge Route Formation of the Ridge Basin Group in the central Ridge 

basin, Los Angeles County, Calif. Is a clastic tongue of the Ridge Route 

and consists of white, medium-grained, arkosic sandstone interbedded 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 115 

with mudstone and rare conglomerate. Contains freshwater mollusks, 

plant remains, ostracodes, and stromatolites. Extends laterally into the 

basin for 4, 620 m. Interfingers with the Ridge Route undivided to the 

northeast and with the Violin Breccia to the southwest. Conformably 

overlies the Osito Canyon Shale Member (new name) and conformably 

underlies the Cereza Peak Shale Member (new name), both of the Peace 

Valley Formation, redefined. Thickness is 172 m at the type section and 

ranges from 50 m to more than 400 m. Age is late Miocene based on its 

stratigraphic position below the fossiliferous late Miocene Cereza Peak 

Shale Member. 

Friendship Chert Member of the Tenmile Creek Formation of 

the Stanley Group 

late Mississippian 

Oklahoma 

Ouachita tectonic belt province 

Pitt, W.D., Fay, R.O., Wilson, L.R., and Curiale, J.A., 1982, Geology of Pushmataha 

County, Oklahoma: Eastern New Mexico University Studies in Natural Sciences 

Special Publication 2, 101 p. 

Type section: Exposure in SWl/4SWlf4NWlf4 sec. 13, T. 2 N., R. 20 E., 

southern Potato Hills, Pushmataha County, Okla. Named for Friendship School, sec. 20, T. 2 N., R. 20 E. 

The Friendship Chert Member, here named, is in the Tenmile Creek 

Formation of the Stanley Group in the Ouachita Mountains in Pushmataha County, southeastern Oklahoma. Consists of dark-gray to olivegray to tan siliceous shale containing thin chert beds. At the type 

section, lies in the lower part of the Tenmile Creek about 300 ft above 

the Arkansas Novaculite and 1, 700 ft below the Albion Creek Chert 

Member (new name) of the Tenmile Creek. Thickness is 65ft at the type 

section. Age is Late Mississippian. 

Gaits Ferry Gneiss Member of the Pumpkinvine Creek 

Formation of the New Georgia Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures near Gaits Ferry Landing on Lake Allatoona, 

Allatoona Dam 7.5-minute quadrangle, Bartow County, Ga. 

The Gaits Ferry Gneiss Member of the Pumpkin vine Creek Formation of the New Georgia Group (new name), here named, is in the 

Greater Atlanta region of northwest Georgia. Consists of banded 
116 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

hornblende-quartz-plagioclase gneiss interlayered with biotitemuscovite-plagioclase gneiss. Gradationally underlies amphibolite and 

garnet gneiss in the Pumpkinvine Creek. Age is Late Proterozoic and 

(or) early Paleozoic. 

Gantts Quarry Formation of the Sylacauga Marble Group 

Early Ordovician 

Alabama 

Piedmont-Blue Ridge province 

Tull, J. F., 1985, Stratigraphy of the Sylacauga Marble Group, in Tull, J. F., and others, 

eds., Early evolution of the Appalachian miogeocline: upper Precambrian-lower 

Paleozoic: Alabama Geological Society Guidebook, 22d Annual Field Trip, November 

22-23, 1985, p. 21-26. 

Type locality: Exposures in the Gantts Quarry, southwest of Sylacauga, 

Talladega County, Ala. 

The Gantts Quarry Formation of the Sylacauga Marble Group, as 

revised by Tull (1982) and here named, is in the Talladega slate belt, 

Alabama. Consists of white, cream, or gray micritic, fine-grained 

banded, calcite marble interlayered with dolomitic marble that has been 

quarried for dimension stone. Overlies the Gooch Branch Chert (new 

name) of the Sylacauga Marble Group; unconformably underlies the Lay 

Dam Formation. Age is Early Ordovician based on conodonts found 

near the base of the unit. 

Gaps Trondhjemite 

Early Proterozoic 

Wyoming 

Green River basin 

Karlstrom, K.E., Houston, R.S., Coolidge, C.M., Flurkey, A.J., and Sever, C.K., 1981, 

The geology of Archean and Early Proterozoic terraines of the Medicine Bow 

Mountains, Wyoming, in Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, 

eds., A summary of the geology and uranium potential of Precambrian conglomerates 

in southeastern Wyoming: U.S. Department of Energy National Uranium Resource 

Evaluation, v. 1, pt. 2, p. 197-399. 

Type area: Intrusive bodies near the Gap and other localities in the 

Medicine Bow Mountains and Sierra Madre, Carbon County, Wyo. 

The Gaps Trondhjemite, informally called the Gaps granite by 

Houston and others (1968) and here named, is in the Medicine Bow 

Mountains and Sierra Madre in southern Wyoming. Consists of red, 

ferruginous, sheared igneous rock that ranges from tonalite to diorite 

but is called trondhjemite because most samples are plagioclase-rich 

leucocratic quartz diorite that does not have alkali feldspars. Is spatially 

associated with and genetically related to gabbroic dikes and sills that 

crosscut the lower Libby Creek Group in the Medicine Bow Mountains 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 117 

and the upper Deep Lake Group in the Sierra Madre. U raninite has 

been found in fractures in the rock. Bodies range in size from a few 

meters to several hundred meters in diameter. Age is Early Proterozoic 

(2,000 Ma). 

Gay Head Greensand 

Miocene 

Massachusetts 

Atlantic Coast basin 

Kaye, C.A., 1983, The autochthonous and allochthonous Coastal Plain deposits of 

Martha's Vineyard and the Marshfield-Scituate area, southeastern Massachusetts: 

Atlantic Coastal Plain Geological Association Field Trip Guidebook, 34 p. 

Type locality: Exposure in Gay Head Cliff, at the west tip of Martha's 

Vineyard, Mass. 

The Gay Head Greensand, here named, is part of the Gay Head 

moraine in Martha's Vineyard, Mass., composed of thrust plates made 

up of remnants of Coastal Plain sediments that were stacked up during 

Pleistocene glaciation. Is also found in borings and excavations in 

Marshfield and Duxbury. Consists of greenish-gray to bluish-gray thin, 

highly fossiliferous, silty, glauconitic sand that has authigenic quartz 

pebbles, phosphate nodules, and glauconite nodules containing fossils of 

mollusks, fish, and crustaceans. Overlies granite bedrock; underlies the 

Devils Bridge Clay (new name) with erosional contact. Thickness 

ranges from 0. 3 to 3. 5 m. Age is Miocene. 

Georgian Bay Formation 

Late Ordovician (Cincinnatian) 

Ontario, Michigan 

Michigan basin 

Liberty, B.A., 1969, Paleozoic geology of the Lake Simcoe area, Ontario: Canada 

Geological Survey Memoir 355, p. 1-201. 

Type locality: Along East Meaford Creek on the south shore of 

Nottawasaga Bay in Georgian Bay, Lake Simcoe district, Ontario, 

Canada. 

Gray carbonate beds and blue and gray shale in the Lake Simcoe 

district, Ontario, are here named the Georgian Bay Formation of the 

Nottawasaga Group. Lower and upper informal members comprise the 

combined strata of the biostratigraphic Dundas and Meaford units. 

Overlies the Whitby Formation; underlies the Queenston Formation. 

Thickness is 130m. Age is Late Ordovician (Cincinnatian). 

Elias, R.J., 1982, Latest Ordovician solitary rugose corals of eastern North America: 

Bulletins of American Paleontology, v. 81, no. 314, p. 1-116. 
118 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Georgian Bay Formation is geographically extended to Drummond Island, Chippewa County, Mich., where a lectotype section is 

designated. 

Gerrit Basalt 

Pleistocene 

Idaho 

Snake River basin 

Christiansen, R. L., 1982, Late Cenozoic volcanism of the Island Park area, eastern Idaho, 

in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic geology of Idaho: Idaho 

Bureau of Mines and Geology Bulletin 26, p. 345-368. 

Type area: Canyon of Henrys Fork of the Snake River, upstream for 5 

km from Upper Mesa Falls, Fremont County, Idaho. Named for Gerrit 

railroad siding, 5 km east of Upper Mesa Falls. 

Basalts younger than the Lava Creek Tuff on the floor of Island 

Park, Fremont County, Idaho, are here named the Gerrit Basalt. The 

basalt flows erupted from several separate small volcanoes. Both 

concordantly and discordantly overlies an erosional surface cut on the 

Lava Creek and Mesa Falls Tuffs; overlies domes of Island Park 

Rhyolite (new name); underlies upper Pleistocene loess and alluvium, 

and probably also underlies the Buffalo Lake rhyolite flow (150 ka). Age 

is Pleistocene based on a potassium-argon age of 200 ka for one of the 

younger flows. 

Gibraltar Rock Member of the Tiger Formation 

Eocene, Oligocene, and Miocene 

Washington 

Northern Cascade Range-Okanogan province 

Gager, B. R., 1983, Stratigraphy of the Tiger Formation, northeastern Washington: 

Northwest Geology, v. 12, p. 25-41. 

Type section: Exposures at Gibraltar Rock, from the top down an 

east-facing gully, SEl/4NEl/4NWl/4 and SWl/4NWl/4NEl/4 sec. 5, T. 34 N., 

R. 43 E., Pend Oreille County, Wash. 

The Gibraltar Rock Member, here named, is in the revised Tiger 

Formation in the Cusick region of northeastern Washington. Consists of 

massive to horizontally and planar cross-stratified polymictic conglomerate and conglomeratic sandstone that has feldspar-rich clasts and 

matrix. Plant fossils are locally abundant in finer grained sandstone and 

siltstone. Unconformably overlies the Sanpoil Volcanics and O'Brien 

Creek Formation; is a facies equivalent of, intertongues with, and is 

separated by a vertical arbitrary boundary from the Locke Member 

(new name) and the Winchester Creek Member (new name), both of the 

Tiger. Thickness at the type section is 105 m; maximum thickness is 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 119 

400 m. Age ranges from early middle Eocene, based on the inclusion of 

late early to early middle Eocene volcanic rock clasts, through middle 

Miocene, based on middle Miocene regional faults that bound the Tiger 

Formation, although the age determination of middle Miocene is less 

definite. 

Gilliam Creek Limestone 

Mississippian 

Tennessee 

Appalachian basin 

Brent, W.B., 1982, Mississippian stratigraphy of Greendale and Newman Ridge synclines 

and Middle Ordovician nomenclature in upper east Tennessee: Tennessee Division of 

Geology Report of Investigations 41, 37 p. 

Type section: Exposures southeast of Gilliam Cemetery and along both 

sides of Gilliam Creek where it cuts through Chestnut Ridge, southwest 

of Looneys Gap in Clinch Mountain, Looneys Gap quadrangle, Hawkins 

County, Tenn. 

The Gilliam Creek Limestone, informally named by Sanders (1952), 

is here named. These Mississippian strata in the Greendale syncline in 

Hawkins and Grainger Counties, Tenn., previously were named the 

Newman Limestone by Hardeman and others (1966) but are isolated 

from the type Newman Limestone in the Newman Ridge syncline. The 

Gilliam Creek consists of finely laminated argillaceous limestone and 

calcarenite containing chert lenses and nodules. Overlies the Clifton 

Creek Limestone (new name); sharply underlies the Fisher Creek 

Formation (new name). Correlates in part with the Ste. Genevieve 

Limestone. Age is Mississippian. 

Glenmark Member of the Rochester Shale 

Middle Silurian (Wenlockian) 

New York 

Appalachian basin 

Brett, C. E., 1983, Stratigraphy and facies relationships of the Silurian Rochester Shale 

(Wenlockian; Clinton Group) in New York State and Ontario: Rochester [N.Y.] 

Academy of Science Proceedings, Centennial Colloquium Issue, v. 15, no. 2, p. 

118-141. 

Type locality: Exposures at Glenmark Falls on Sodus Creek near 

Sodus, Sodus Bay 7.5-minute quadrangle, Wayne County, N.Y. 

The Glenmark Member of the Rochester Shale, here named, is a 

distinctive ledge-forming unit in the middle part of the Rochester in 

Wayne and Cayuga Counties, N.Y. Consists of dark bluish-gray, 

argillaceous limestone that has thin shaley partings and basal coarsely 

crystalline limestone that has hematite stringers. Gradationally overlies 

the calcareous lower part of the Rochester; abruptly and sharply 
120 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

underlies the upper Rochester. Thickness is 9 m at the type locality. 

Age is Middle Silurian (Wenlockian). 

Glenmore Member of the Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: DePere Site, a gravel pit north of Highway X, near the 

top of the Silurian escarpment, southeast corner of sec. 38, T. 23 N., R. 

20 E., DePere 7.5-minute quadrangle, Brown County, Wis. Named for 

the township of Glenmore. 

Following the informal usage of McCartney and Mickelson (1982), 

the Glenmore Member of the Kewaunee Formation (new name), here 

named, is in the Green Bay Lobe east of the Fox River in Wisconsin. 

Consists of dull-reddish-brown sand, silt, and clay. Abruptly overlies 

the Chilton Member (new name) of the Kewaunee; underlies younger 

unnamed organic sediment or lacustrine silt and clay or is the surface 

unit in many places. Correlates with the Two Rivers Member of the 

Kewaunee Formation in the Lake Michigan Lobe and with the Middle 

Inlet Member (new name) of the Kewaunee on the west side of the 

Green Bay Lobe, from which it is separated by an arbitrarily determined vertical contact at the Fox River. Thickness is 6 mat the type 

section. Age is Pleistocene (late Wisconsinan). 

Gooch Branch Chert of the Sylacauga Marble Group 

Cambrian and Ordovician 

Alabama 

Piedmont-Blue Ridge province 

Tull, J.F., 1985, Stratigraphy of the Sylacauga Marble Group, in Tull, J.F., and others, 

eds., Early evolution of the Appalachian miogeocline: Upper Precambrian-lower 

Paleozoic: Alabama Geological Society Guidebook, 22d Annual Field Trip, November 

22-23, 1985, p. 21-26. 

Type locality: None designated. Forms low hills in the city of 

Sylacauga, Talladega County, Ala. 

The Gooch Branch Chert, here named, occurs in the Sylacauga 

Marble Group, as revised by Tull (1982), in the Talladega slate belt, 

Alabama. Consists of gray to tan, dolomitic marble interbedded with 

cream to white, foliated metachert that forms benches and rubble 

trains. Contains brown iron ore and manganese. Overlies the Shelvin 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 121 

Rock Church Formation (new name) and underlies the Gantts Quarry 

Formation (new name), both of the Sylacauga Marble Group. Correlates 

with much of the Cambrian-Ordovician Knox Group, especially the 

Copper Ridge Dolomite. Age is Cambrian and Ordovician based on 

Early Ordovician conodonts in the overlying Gantts Quarry Formation. 

Goose Creek Limestone 

Pliocene 

South Carolina 

Atlantic Coast basin 

Weems, R.E., Lemon, E.M., Jr., McCartan, Lucy, Bybell, L.M., and Sanders, A.E., 

1982, Recognition and formalization of the Pliocene "Goose Creek phase" in the 

Charleston, South Carolina, area: U.S. Geological Survey Bulletin 1529-H, 

p. H137-H148. 

Type section: Bluff along Goose Creek 0.3 km east of the Seaboard 

Coastline railroad bridge over Goose Creek, North Charleston 7.5-

minute quadrangle, Berkeley County, S.C. (Sloan, 1908). 

The Goose Creek phase of Sloan (1908) in the Charleston, S.C., area 

is here formally named the Goose Creek Limestone. Consists of gray to 

white, medium- to coarse-grained, quartzose, phosphatic, sparsely 

shelly calcarenite. Unconformably overlies the Ashley Member of the 

Cooper Formation. Thickness at the type section is 3m. Age is Pliocene. 

Governors Point Member of the Chuckanut Formation 

Eocene 

Washington 

Bellingham basin 

Johnson, S.Y., 1984, Stratigraphy, age, and paleogeography of the Eocene Chuckanut 

Formation, northwest Washington: Canadian Journal of Earth Sciences, v. 21, no. 1, 

p. 92-106. 

Type section: Exposures on the west coast of Governors Point on 

Bellingham Bay, El/2 sec. 26, T. 37 N., R. 3 E., Bellingham, Whatcom 

County, Wash. 

The Governors Point Member, here named, is in the Chuckanut 

Formation in the Bellingham Bay area in the western part of the largest 

outcrop belt of the Chuckanut, which extends from the SanJuan Islands 

into the foothills of the North Cascades, Wash. Consists of finingupward beds of cross-stratified arkosic sandstone and massive to 

crudely stratified metagraywacke-rich conglomerate, representing 

braided-river deposits. Conformably overlies the Bellingham Bay Member (new name) and unconformably underlies the Padden Member (new 

name), both of the Chuckanut. Thickness is 375m at the type section. 
122 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Age is early middle Eocene based on the age of the tuff bed (49.9 Ma) at 

the top of the underlying Bellingham Bay Member. 

Grand Prize Formation 

Pennsylvanian(?) and Early Permian (Leonardian or Wolfcampian) 

Idaho 

Idaho Mountains province 

Hall, W.E., 1985, Stratigraphy of and mineral deposits in middle and upper Paleozoic 

rocks of the black-shale mineral belt, central Idaho, in Mcintyre, D.H., ed., Symposium on the geology and mineral deposits ofthe Challis 1° x 2° quadrangle, Idaho: U.S. 

Geological Survey Bulletin 1658 A-S, p. 117-131. 

Type locality: North side of Pole Creek at its confluence with Grand 

Prize Creek, Horton Peak 7.5-minute quadrangle, Custer County, 

Idaho. 

Rocks exposed in a 800-km2 area from 2 km north of Galena Summit 

north to the Yankee Fork of the Salmon River on the eastern side of the 

Idaho batholith, formerly mapped as part of the Wood River Formation, 

are here named the Grand Prize Formation. Is divided at the type 

locality into four unnamed units: dark-gray, carbonaceous siltite and 

gray limestone, 690 m thick; bluish-gray, fine-grained limestone, 30m 

thick; gray, banded, limy siltstone and carbonaceous siltite, 580 m thick; 

and dark-gray, banded siltite and gray limestone, 150 m thick. Overlies 

the Wood River Formation in thrust-fault contact. Age, based on 

conodonts, is Early Permian (Leonardian or Wolfcampian) or possibly 

as old as Pennsylvanian. 

Grangeville Member of the Saddle Mountains Basalt of the 

Columbia River Basalt Group 

Miocene 

Idaho 

Idaho Mountains province 

Camp, V.E., 1981, Geologic studies of the Columbia Plateau: Part II. Upper Miocene 

basalt distribution, reflecting source locations, tectonism, and drainage history in the 

Clearwater embayment, Idaho: Geological Society of America Bulletin, v. 92, no. 9, 

pt. I, p. 669-678. 

Type locality: Grangeville, near South Fork of Clearwater River, Idaho 

County, Idaho. 

The Grangeville Member of the Saddle Mountains Basalt of the 

Columbia River Basalt Group, here named, is in the Nez Perce plateau 

of the Clearwater embayment, Idaho. Consists of medium- to coarsegrained olivine basalt that erupted from dikes cutting the Nez Perce 

plateau in Rocky canyon. Overlies the basalt of Weippe of the Pomona 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 123 

Member and underlies the Craigmont Member (new name), both of the 

Saddle Mountains Basalt. Age is late Miocene. 

Granite Basin Porphyry 

Cretaceous and (or) Tertiary 

Arizona 

Basin and Range province 

Creasey, S.C., 1984, The Schultze Granite, the Teacup Granodiorite, and the Granite 

Basin Porphyry: A geochemical comparison of mineralized and unmineralized stocks in 

southern Arizona: U.S. Geological Survey Professional Paper 1303, 41 p. 

Type locality: Granite Basin, T. 4 S., R. 16-17 E., Christmas 15-minute 

quadrangle (Christmas and Jerusalem Mountain 7.5-minute quadrangles), Gila and Pinal Counties, Ariz. 

The Granite Basin Porphyry, here named, crops out in a 16-km2 area 

about 35 km south-southeast of Globe, Ariz. Consists of euhedral 

phenocrysts of plagioclase, hornblende, and biotite in a holocrystalline, 

phanerocrystalline, aplitic groundmass of potassium feldspar, quartz, 

plagioclase, and hornblende that shows no indication of copper mineralization. Characterized by its uniformity of chemical composition, 

texture, and mineralogy and by the evenness in the degree and extent 

of secondary alteration. Is sill-like and intrudes the late Paleozoic 

Escabrosa and Naco Limestones. Age is Cretaceous and (or) Tertiary 

based on potassium-argon ages of hornblende of 72.3 and 60.7 Ma. 

Green Spot Formation of the Big Bear Group 

Precambrian 

California 

Mohave basin 

Cameron, C. S., 1982, Stratigraphy and significance of the upper Precambrian Big Bear 

Group, in Cooper, J.D., Geology of selected areas in the San Bernardino Mountains, 

western Mohave desert, and southern Great Basin, California: Geological Society of 

America, Cordilleran Section, 78th Annual Meeting, guidebook, field trip 9, p. 5-20. 

Type locality: None designated. Named for Green Spot Hill, San 

Bernardino County, Calif. 

Following the informal usage of Cameron (1981), the Green Spot 

Formation, here named, is in the Big Bear Group (new name) in the 

southwest part of the Sugarloaf Mountain area of the San Bernardino 

Mountains in California. Consists of a complexly imbricated and 

intruded sequence of dolomitic, cherty, calc-silicate, and stromatolitic 

marble, phyllite, and quartzite, and is divided into nine unnamed 

members, G1 to G9. Contacts between the members are conformable; 

conformably overlies the Moonridge Quartzite (new name) and 
124 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

gradationally underlies the Delamar Mountain Formation (new name), 

both of the Big Bear Group. Thickness is approximately 880 m. Age is 

late Precambrian. 

Hall Canyon Conglomerate Member of the Goldens Ranch 

Formation 

Oligocene 

Utah 

Great Basin province 

Meibos, L.C., 1983, Structure and stratigraphy of the Nephi NW 7.5-minute quadrangle, 

Juab County, Utah: Brigham Young University Geology Studies, v. 30, pt. 1, p. 37-58. 

Type locality: None designated. Best exposures are northwest and 

southeast of Hall Canyon on the east side of Long Ridge, NEl/4 sec. 16, 

T. 13 S., R. 1 W., Nephi NW 7.5-minute quadrangle, Juab County, 

Utah. 

The Hall Canyon Conglomerate Member is here named the middle 

member of the Goldens Ranch Formation in the Great Basin province, 

Utah. Divided, on the basis of the presence of volcanic clasts, into units 

Q and V. Unit Q consists of 60 to 70 percent quartzite clasts and 30 to 

40 percent limestone clasts. Unit V consists of 45 to 55 percent quartzite 

clasts, 15 percent limestone clasts, and 30 to 40 percent volcanic clasts 

of red andesite. The quartzite clasts resemble Tintic Quartzite; the 

limestone clasts are Paleozoic limestone. The matrix of both units is 

bentonitic clay. Overlies the Chicken Creek Tuff Member, here reduced 

in rank from formation, of the Goldens Ranch; unconformably underlies 

the Sage Valley Limestone Member of the Goldens Ranch. Correlates 

with parts of the Ajax and Crazy Hollow Formations. Thickness is 

about 250m. Age is Oligocene. 

Hannah Member of the Promised Land Formation of the Atlanta 

Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Exposures where powerlines cross a southwest running 

road northwest of Hannah Cemetery, near Centerville, Snellville 7.5-

minute quadrangle, Gwinnett County, Ga. 

The Hannah Member of the Promised Land Formation (new name) 

of the Atlanta Group (new name), here named, is in the Newnan-Tucker 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 125 

synform near Atlanta, Ga., and is a thin unit of quartzite and schist at 

the top of the Promised Land. Fresh outcrops are white. Thickness is 

3m. Age is Late Proterozoic and (or) early Paleozoic. 

Hansboro Formation of the Coleharbor Group 

Pleistocene (Wisconsinan) 

North Dakota 

Williston basin 

Bluemle, J.P., 1984, Geology of Towner County, North Dakota: North Dakota Geological 

Survey Bulletin 79, pt. I, p. 1-44. 

Type locality: None designated. Named for the town of Hansboro, 

Towner County, N. Dak. 

The Hansboro Formation of the Coleharbor Group, here named, was 

informally named by Howard Hobbs in an unpublished study of the 

glacial stratigraphy of northeastern North Dakota. Is the uppermost of 

five glacial till deposits representing separate advances of glacial ice in 

Towner County, N. Dak. Consists of fissile till and stratified sediment 

containing crystalline sand and carbonate grains and characterized by 

sparse shale. Color is buff where oxidized and light-gray where unoxidized. Directly overlies the Dahlen Formation; no overlying units have 

been observed. Probably deposited during a readvance of the glacier 

that had earlier deposited the Dahlen Formation. Till portion is less 

than 15 ft thick; total thickness attains 50 ft. Age is Pleistocene, 

probably late Wisconsinan. 

Hanson Creek Member of the Miller Creek Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Exposures in bluff, 1.5 km west of the mouth of Hanson 

Creek, SEl/4SWl/4SWl/4 sec. 27, T. 49 N., R. 12 W., Poplar NE 

7.5-minute quadrangle, Douglas County, Wis. Named for Hanson 

Creek, which drains into Lake Superior 1 km east of the mouth of the 

Amnicon River. 

Following the informal usage of Need (1980), the Hanson Creek 

Member of the Miller Creek Formation (new name), here named, is in 

the Superior Lobe along the Lake Superior shoreline in Douglas and 

Bayfield Counties, Wis. Consists of dark reddish-brown till. Sharply 

overlies pre-Pleistocene rocks or the Pleistocene Copper Falls 
126 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Formation (new name); underlies the Douglas Member (new name) or 

sand of the Miller Creek Formation. Thickness is 7.5 m at the type 

section. Age is Pleistocene (latest Wisconsinan). 

Haven Member of the Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Nuclear power plant site in Lake Michigan bluff, 

NW1/4NW1/4NE1/4 sec. 22, T. 16 N., R. 23 E., Sheboygan North 

7.5-minute quadrangle, Sheboygan County, Wis. Named for the community of Haven. 

Following the informal usage of Acomb (1978), the Haven Member 

of the Kewaunee Formation (new name), here named, is in the Lake 

Michigan Lobe in Wisconsin. Consists of pinkish-gray, red, and reddishbrown, pebbly, sandy, and clayey silt till. Overlies the Ozaukee Member 

(new name) and underlies the Valders Member, both of the Kewaunee. 

Is equivalent to the Chilton (new name) and Kirby Lake (new name) 

Members of the Kewaunee in the Green Bay Lobe. Thickness ranges 

from 2.4 m to 15m. Age is Pleistocene (late Wisconsinan). 

Hays Member of the Bell Canyon Formation of the Delaware 

Mountain Group 

late Permian (Guadalupian) 

Texas, New Mexico 

Permian basin 

Winner, Phil, 1985, Type section for the uppermost Bell Canyon Formation in the central 

Delaware basin of West Texas: West Texas Geological Society Bulletin, v. 24, no. 7, 

p. 7-10. 

Type section: Gulf J.R. Grandin Number 1 well, sonic-gamma ray log, 

SE1/4 sec. 33, Block 29 PSL Survey, Loving County, Tex. Named for the 

Hays field, Reeves County, Tex. 

The Hays Member, here named, is the lowest producing unit in the 

informal A sand in the upper Bell Canyon Formation of the Delaware 

Mountain Group in the central Delaware basin of Texas and New 

Mexico. Called the informal Hays sandstone member of the Bell Canyon 

by Grauten (1965), who defined it as the petroleum-producing sand in 

the Hays field. The producing sand is now correlated with the Olds 

Member (new name) of the Bell Canyon, the main pay in the Olds field. 

The Hays is also a producing sand in the Quito field. Consists of 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 127 

silty, fine-grained sandstone and displays clean gamma-ray response 

and good porosity development at the base; the upper portion is 

relatively shaley and has lower porosity due to an increase in carbonate 

cement. Overlies the informal Bell Canyon B sand; underlies the Olds 

Member. Thickness ranges from 40ft in the type well to 110ft. [Age is 

Late Permian (Guadalupian).] 

Helen Group 

Late Proterozoic and Paleozoic 

Georgia, North Carolina 

Piedmont-Blue Ridge province 

Nelson, A.E., and Gillon, K.A., 1985, Stratigraphic nomenclature in the Richard Russell 

and Helen thrust sheets, Georgia and North Carolina: U.S. Geological Survey Bulletin 

1605--A, p. A59-A62. 

Type locality: Exposures near the town of Helen, Helen 7.5-minute 

quadrangle, White County, Ga. (Gillon, 1982). 

Subunits: Nacoochee Formation, Horton Formation, Robertstown 

Formation. 

The name Helen Group, used informally by Gillon (1982), is here 

adopted for metamorphic rocks of the Helen thrust sheet between the 

Dahlonega and Shope Fork faults, Georgia and North Carolina. 

Includes the Nacoochee (new name), Horton (new name) (Gillon's 

informal Chattahoochee), and Robertstown (new name) (Gillon's informal Unicoi Park) Formations. The Group is fault bounded and isoclinally 

folded. The nature of the contact with the overlying Coweeta Group is 

uncertain. Age is tentatively Late Proterozoic and early Paleozoic. 

Helen Member of the Canton Formation 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

German, J.M., 1985, The geology of the northeastern portion of the Dahlonega gold belt: 

Georgia Geologic Survey Bulletin 100, p. 1-41. 

Type locality: Named for town of Helen, White County, Ga. 

The Helen Member of the Canton Formation, here named, is in the 

Dahlonega area, Georgia, and was previously mapped as the Carolina 

Gneiss by Keith (1909). [It is incorrectly stated by German (1985) that 

Gillon (1982) named these rocks the informal Helen sequence. Gillon's 

(1982) informal Helen group was formally named the Helen Group 

(new name) by Nelson and Gillon (1985), a usage that is consistent 

with Gillon's original definition and should take precedence over the 

usage of German (1985) of Helen Member of the Canton Formation.] 

The Helen Member consists of biotite-plagioclase-quartz gneiss and 
128 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

biotite-muscovite-quartz schist containing garnet. Is in sharp contact 

with the Chestatee Member (new name) of the Canton; grades into the 

Univeter (new name) and Tallulah Falls Formations to the southeast 

and the Palmer Creek Member (new name) of the Canton and the 

Coweeta Group to the northwest. Its boundaries are defined as the 

last occurrence of interlayered metagraywacke and biotite-muscovitequartz schist. Age is Late Proterozoic and (or) early Paleozoic. 

Hemlock Lake Formation of the Saginaw Group 

Early Pennsylvanian (Morrowan) 

Michigan 

Michigan basin 

Vugrinovich, Ray, 1984, Lithostratigraphy and depositional environments of the Pennsylvanian rocks and the Bayport Formation of the Michigan basin: Michigan Geological 

Survey Division, Report of Investigation 27, 33 p. 

Type section: Michigan Consolidated Gas Company Number L-125 well, 

depth interval 770-1,000 ft, center NWl/4NWlf4 sec. 29, T. 18 N., 

R. 5 W., Lincoln Township, Clare County, Mich. Named for nearby 

Hemlock Lake. 

Subunit: Six Lakes Limestone Member. 

The Hemlock Lake Formation of the Saginaw Group, here named, 

lies in the subsurface of the Michigan basin. The lower part of the 

formation contains a thin discontinuous basal coal bed overlain by a 

sequence of thin-bedded, yellowish-gray sandstone, red and gray interbedded siltstone, and gray shale containing minor amounts of carbonate 

rock. The Six Lakes Limestone Member (new name) is present in the 

western part of the Hemlock Lake study area. The upper part of the 

Hemlock Lake consists of shale containing minor amounts of siltstone, 

sandstone, carbonate rock, and coal. The unit represents back-barrier 

and transgressive marine and alluvial plain deposits. Overlies the 

Parma Formation; underlies the Lake George Formation (new name) of 

the Saginaw Group with sharp contact. Thickness at the type well is 230 

ft. Age is Early Pennsylvanian (Morrowan). 

Herbert Till Member of the Glasford Formation 

Pleistocene (Illinoian) 

Illinois 

Wisconsin arch 

Kempton, J.P., Berg, R.C., and Follmer, L.R., 1985, Revision of the stratigraphy and 

nomenclature of glacial deposits in central northern Illinois: Illinois Geological Survey, 

Midwest Friends of the Pleistocene, 32d field conference, guidebook 19, p. 1-19. 

Type section: Stone Quarry Road Boring, 6.4 km northwest of village of 

Herbert, NElf4NElf4NEl/4 sec. 22, T. 43 N., R. 3 E., Boone County, Ill. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 129 

The recognition that the Esmond Till Member is a unit of the 

Illinoian Glasford Formation, rather than of the Wisconsinan Wedron 

Formation, has left three unnamed till members below the Esmond 

Member. The oldest of these, here named the Herbert Till Member of 

the Glasford Formation, occurs in the subsurface of parts of Boone, De 

Kalb, Ogle, McHenry, and Kane Counties, Ill. Consists of a gray-brown 

loam to sandy loam diamicton and has a clay-mineral composition similar 

to the Esmond, but illite often exceeds 80 percent. Overlies shale of the 

Maquoketa Group; underlies the Fairdale or Oregon Till Members (both 

new names) of the Glasford Formation. Was previously correlated with 

the Sterling Till Member of the Glasford. Thickness is less than 10 m. 

Age is Pleistocene (Illinoian). 

Hersey Member of the Pierce Formation 

Pleistocene (pre-Illinoian) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: West side of abandoned gravel pit, north of Highway 12, 

1 km southwest of Hersey, SW1/4SEl/4 SEl/4 sec. 29, T. 29 N., R. 15 W., 

Wilson 7.5-minute quadrangle, St. Croix County, Wis. 

Following the informal usage of Baker and Simpson (1981), the 

Hersey Member, here named, is the lower member of the Pierce 

Formation (new name) in west-central Wisconsin. Consists of yellowishbrown to dark-gray, structureless, calcareous till and associated sand 

and gravel. The lower contact is unknown except where it overlies 

Paleozoic bedrock; gradationally underlies the Kinnickinnic Member 

(new name) of the Pierce or sharply underlies the River Falls Formation 

(new name), and is the surface unit in Pierce, Buffalo, Pepin, and Dunn 

Counties. Thickness ranges from 1 to 55 m. Age is Pleistocene 

(pre-Illinoian). 

Hexenkopf Complex 

Middle Proterozoic 

Pennsylvania 

Appalachian basin 

Drake, A.A., Jr., 1984, The Reading Prong of New Jersey and eastern Pennsylvania-An 

appraisal of rock relations and chemistry of a major Proterozoic terrane in the 

Appalachians: Geological Society of America Special Paper 194, p. 75-126. 

Type locality: Exposures on and near Hexenkopf Hill, Riegelsville 

quadrangle, Northampton County, Pa. 
130 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Hexenkopf Complex, here named, occurs in a 15-km2 area in 

east-central Pennsylvania where the Riegelsville, Easton, Nazareth, 

and Hellertown quadrangles meet. Consists of a heterogeneous body of 

highly altered mafic rock of three general types: hornblende-augitequartz-andesine gneiss, epidote-augite-hornblende-plagioclase gneiss, 

and quartz-garnet-augite granofels. Is in thrust contact with lower 

Paleozoic rocks on the south and with the Byram Intrusive Suite on the 

north. Underlies the Losee Metamorphic Suite and other metasedimentary rocks on the east and west. Age is Middle Proterozoic, predating all 

other Middle Proterozoic rocks in the area. 

Highland Gypsum Member of the De Queen Formation of 

the Trinity Group 

Early Cretaceous 

Arkansas 

Ouachita tectonic belt province 

Darling, B.K., and Lock, B.E., 1984, The surface formations of the Trinity Group in 

southwestern Arkansas, and a proposed revision of stratigraphic rank for the three 

lower units: Gulf Coast Association of Geological Societies Transactions, 34th Annual 

Meeting, p. 321-327. 

Type section: Highland gypsum quarry, SWl/4NEl/4 sec. 21, T. 8 S., R. 

26 W., Pike County, Ark. 

The Highland Gypsum Member, here named, is in the easternmost 

part of the De Queen Formation of the Trinity Group in Pike and 

Howard Counties, Ark. Consists of thin beds of claystone, lime mudstone, algal laminated dolomudstone, and mosaic gypsum. Gypsum beds 

do not appear to be laterally extensive and are indicative of deposition 

in shallow lagoonal waters, back-reef brine ponds, and abandoned tidal 

channels on mudflats. Overlies the Holly Creek Formation; underlies 

the Murfreesboro Member (new name) of the De Queen. Correlates 

with the Ferry Lake Anhydrite in the subsurface in Oklahoma. Thickness is 29 ft at the type section. Age is Early Cretaceous. 

High Pond Member of the Bear Pond Gneiss 

Precambrian 

New York 

Adirondack uplift 

Potter, D.B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: None designated. Named for High Pond, Tupper Lake 

15-minute quadrangle, St. Lawrence County, N.Y. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 131 

The High Pond Member of the Bear Pond Gneiss (new name), here 

named, is in the Loon Pond syncline in the Bog River synclinorium in 

the Adirondack Highlands, Hamilton and St. Lawrence Counties, N.Y. 

Consists of quartz-rich, sugary-textured granulite containing magnetite, pyrite, garnet, biotite, sillimanite, and microcline and small 

boudins of garnet-quartz-augite gneiss. Thickness ranges from 10 to 15 

m. Age is Precambrian. 

High Shoals Granite 

Pennsylvanian 

North Carolina 

Piedmont-Blue Ridge province 

Horton, J.W., Jr., 1984, Stratigraphic nomenclature in the Kings Mountain belt, North 

Carolina and South Carolina: U.S. Geological Survey Bulletin 1537-A, p. A59-A67. 

Type locality: Exposures at High Shoals on the South Fork Catawba 

River, lat 35°23'48" N., long 81°12'05" W., Gaston County, N.C. 

Rocks previously mapped as Yorkville Granite by Keith and Sterrett (1931) and as Yorkville Quartz Monzonite by Espenshade and 

Potter (1960) are here named the High Shoals Granite. Was informally 

named the High Shoals granitic gneiss by Horton and Butler (1977) to 

distinguish it from nonfoliated granites like the type Yorkville near 

York, S.C. Occupies an area of batholithic size in the Kings Mountain 

belt, North Carolina. Consists of coarse-grained, generally porphyritic, 

gneissoid biotite granite or granitic gneiss. Uranium-lead isotopic data 

on zircons indicate a Pennsylvanian age of about 317 Ma. 

Hill 2292 Member of the Lost Pond Marble 

Precambrian 

New York 

Adirondack uplift 

Potter, D.B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: Outcrops along the steep southern slopes of Loon Pond 

Mountain, Tupper Lake 15-minute quadrangle, Hamilton County, N.Y. 

The Hill 2292 Member of the Lost Pond Marble (new name), here 

named, is in the Loon Pond syncline in the Bog River synclinorium in 

the Adirondack Highlands, Hamilton and St. Lawrence Counties, N.Y. 

Consists of sillimanite-microcline-quartz granulite. Overlies the Bog 

River Member (new name) and underlies the Sabattis Road Member 

(new name), both of the Lost Pond Marble. Thickness is more than 50 m. 

Age is Precambrian. 
132 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Hills Mountain Granulite Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., Gathright, T.M., II, and Henika, W.S., 1981, A tectonic model for 

the Blue Ridge in central Virginia: American Journal of Science, v. 281, no. 9, 

p. 1164-1183. 

Type locality: Near Hills Mountain, 15 km northeast of Lovingston on 

aN. 18° E. trend, Greenfield 7.5-minute quadrangle, Nelson County, 

Va. 

The Hills Mountain Granulite Gneiss, here named, is in the Lovingston massif in the central Blue Ridge, Va. Consists of gray, mediumgrained, hypersthene-bearing quartz-feldspathic gneiss that has granablastic texture and poorly developed segregation layering. Forms most 

of the country rock and roof pendants in the Archer Mountain pluton. 

The contact zone between the gneiss and the pluton consists of a zone of 

migmatitic granulite gneiss. Age is Middle Proterozoic. 

Hills Point Member of the Flanner Beach Formation 

Pleistocene 

North Carolina 

Atlantic Coast basin 

Miller, William, III, 1985, The Flanner Beach Formation (middle Pleistocene) in eastern 

North Carolina: Tulane Studies in Geology and Paleontology, v. 18, no. 3, p. 93-122. 

Type section: Bluffs on the south shore of the Pamlico River, 0.2 km 

upstream from Camp Hardee and 1.2 km west of Hills Point, Blounts 

Bay 7.5-minute quadrangle, Beaufort County, N.C. 

The Hills Point Member of the Flanner Beach Formation, here 

named, is in the Pamlico River valley, Blounts Bay area, Beaufort 

County, N.C. Blanketlike deposits, which may represent lagoonal or 

river estuary deposition, consist of laminated silty clay and clayey silt 

that have sand lenses, burrows, and carbonized wood. Unconformably 

overlies pre-Flanner Beach fluvial deposits; grades eastward into an 

unnamed heavily burrowed sand unit of the Flanner Beach; intertongues with and underlies the Mauls Point Member (new name) of the 

Flanner Beach. Thickness is 2.5 mat the type section. Age is middle 

Pleistocene. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 133 

Hilt Bed of the Blue Gulch Mudstone Member of the 

Hornbrook Formation 

Late Cretaceous (Campanian) 

California, Oregon 

Klamath Mountains province 

Nilsen, T.H., 1984, Tectonics and sedimentation of the Upper Cretaceous Hornbrook 

Formation, Oregon and California, in Crouch, J.K., and Bachman, S.B., eds., 

Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and Mineralogists, Pacific Section, v. 38, p. 101-118. 

Type section: Roadcut along an access road to the Hilt exit east of 

Interstate Highway I-5, NW1/4SW1/4 sec. 24, T. 48 N., R. 7 W., 

Hornbrook 15-minute quadrangle, Siskiyou County, Calif. Named for 

the abandoned town of Hilt, 11 km northwest of Hornbrook. 

The Hilt Bed, here named, is in the Blue Gulch Mudstone Member 

(new name) of the Hornbrook Formation in the northern margin of the 

Shasta Valley, Siskiyou County, Calif., and the Dark Hollow area, 

Jackson County, Oreg., on the northeast margin of the Klamath 

Mountains. The Hilt is a prominent, laterally continuous bed of gray 

sandstone in the middle part of the Blue Gulch Mudstone Member, 

about 480 m above the base. Thickness ranges from 2 to 5 m. Age is Late 

Cretaceous (Campanian). 

Holly Fork Member of the Slade Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R. 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Roadcut south of Holly Fork along westbound lanes of 

Interstate Highway I-64, 16 km west of its intersection with Kentucky 

Highway 2, Soldier quadrangle, Rowan County, Ky. 

The Holly Fork Member, used informally by Ettensohn (1977) and 

here named, is in the Slade Formation (new name) and was previously 

included in units now restricted from the Cumberland Escarpment area 

of east-central and northeastern Kentucky. Consists of dolostone and 

calcilutite. Disconformably overlies or intertongues with the Armstrong 

Hill Member (new name) and disconformably underlies or intertongues 

with the Tygarts Creek Member (new name), both of the Slade. 

Maximum thickness is 5 m. Age is Late Mississippian. 
134 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Hooper Canyon Formation 

Tertiary 

Utah 

Wasatch uplift 

Van Horn, Richard, 1981, Geologic map of pre-Quaternary rocks of the Salt Lake City 

North quadrangle, Davis and Salt Lake Counties, Utah: U.S. Geological Survey 

Miscellaneous Investigations Map I-1330, scale 1:24,000. 

Type locality: Exposures in the headwaters of Hooper Canyon in the 

Fort Douglas quadrangle, 1.5 km east of the Salt Lake City North 

quadrangle, Davis County, Utah. 

The Hooper Canyon Formation, here named, is in the Wasatch uplift 

in north-central Utah, where it was deposited by west-flowing streams 

on a late Tertiary erosion surface. Consists of brown to gray, poorly to 

moderately consolidated, crudely bedded alluvium ranging in size from 

boulders to silt in a sandy and silty matrix. Subrounded to subangular 

clasts are 50 to 75 percent quartzite or sandstone and 30 to 50 percent 

limestone. Unconformably overlies upper Tertiary conglomerate. 

Thickness is as much as 15m. Age is late Tertiary. 

Horicon Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Roadcut on the south side of Maple view Road, west of its 

intersection with Maple Road, SE1/4SW1/4SW1/4 sec. 34, T. 31 N., 

R. 10 E., Mattoon 7.5-minute quadrangle, Langlade County, Wis. 

Named for the city of Horicon, Dodge County. 

Subunits: Liberty Grove Member, Mapleview Member. 

The Horicon Formation, here named, is in the Green Bay Lobe in 

eastern, central, and southern Wisconsin. Includes the Mapleview 

Member (new name) on the west side of the Green Bay Lobe in 

Langlade and Marathon Counties and the equivalent Liberty Grove 

Member (new name) on the east side in Door County. No members are 

named in south-central Wisconsin. Consists of brown, reddish-brown, 

and yellowish-brown till and associated sand and gravel. Sharply 

overlies the Walworth Formation (new name) or bedrock or sand and 

gravel; is the surficial unit in much of south-central Wisconsin, but 

abruptly underlies the Kewaunee Formation (new name) near Green 

Bay. Thickness ranges from 1 m to more than 100 m. Age is late 

Pleistocene (late Wisconsinan). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 135 

Horsepen Mountain Suite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Outcrops along Virginia Highway 24 on the southern 

flank of Horsepen Mountain, lat 37°17' N., long 79°49' W., Stewartsville 

7.5-minute quadrangle, Bedford County, Va. 

The Horsepen Mountain Suite, here named, is in the Lovingston 

massif in the Blue Ridge of Virginia. Consists of biotite dioritoid and 

charnockite. Age is Middle Proterozoic. 

Horton Formation of the Helen Group 

late Proterozoic and Paleozoic 

Georgia, North Carolina 

Piedmont-Blue Ridge province 

Nelson, A.E., and Gillon, K.A., 1985, Stratigraphic nomenclature in the Richard Russell 

and Helen thrust sheets, Georgia and North Carolina: U.S. Geological Survey Bulletin 

1605-A, p. A59-A62. 

Type locality: Exposures along the Chattahoochee River in the city of 

Helen, Helen 7.5-minute quadrangle, White County, Ga. (Gillon, 1982). 

Named for Horton Creek, which flows into the Chattahoochee River 

south of Robertstown. 

The informal Chattahoochee formation of Gillon (1982) is here named 

the Horton Formation of the Helen Group (new name) in the Helen 

thrust sheet in Georgia and North Carolina. Consists of an interlayered 

sequence of argillaceous and feldspathic metasandstone and metasiltstone (locally sulphidic), mica schist, aluminous schist, and amphibolite. 

Is conformable and gradational with the Nacoochee Formation (new 

name) of the Helen Group to the southeast; is conformable with the 

Robertstown Formation (new name) of the Helen Group to the northwest. Age is tentatively Late Proterozoic and early Paleozoic. 

Houstenaden Creek Formation 

late Cretaceous (Campanian) 

Oregon 

Western Columbia basin 

Bourgeois, Joanne, and Dott, R.H., Jr., 1985, Stratigraphy and sedimentology of Upper 

Cretaceous rocks in coastal southwest Oregon: Evidence for wrench-fault tectonics in 

a postulated accretionary terrane: Geological Society of America Bulletin, v. 96, no. 8, 

p. 1007-1019. 
136 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Composite of the exposures at Houstenaden Cove, Burnt 

Hill Cove, and Cape Sebastian, Curry County, Oreg. Named for 

Houstenaden Creek. 

Rocks formerly mapped as lower Cape Sebastian Sandstone by 

Hunter and others (1970) and as Hunters Cove Formation by Dott 

(1971) are here named the Houstenaden Creek Formation in a region of 

complex juxtaposition of tectonostratigraphic terranes in southwest 

Oregon. With the Late Jurassic Otter Point complex [Formation] and 

the Late Cretaceous Cape Sebastian Sandstone and Hunters Cove 

Formation, it forms the distinctive Gold Beach terrane west of highangle faults that mark the boundary of the Neogene Humboldt 

microplate. Consists of alternating beds of mudstone, siltstone, and 

sandstone turbidites in the lower part, overlain by thick amalgamated, 

coarse-grained sandstone that has channelized conglomerate bodies. 

Lies in fault contact with the underlying Otter Point; unconformably 

underlies the Cape Sebastian Sandstone. Thickness is at least 500 m. 

Age is Late Cretaceous (Campanian) based on dinoflagellates and 

pollen. 

Hulopoe Gravel 

Pleistocene 

Hawaii 

Moore, J.G., and Moore, G.W., 1984, Deposit from a giant wave on the Island of Lanai, 

Hawaii: Science, v. 226, no. 4680, p. 1312-1314. 

Type locality: Exposures along the major gulch that drains into the 

northernmost extent of Kapihua Bay, the bay directly west of Hulopoe 

Bay, Island of Lanai, Hawaii. 

The Hulopoe Gravel, here named, is on the coastal slopes of Lanai, 

Hawaii, where it reaches a maximum elevation of 326 m. Gravel was 

deposited by the surge of a giant ocean wave, created by the rapid 

movement of a submarine slide, that swept several hundred m up the 

flanks of Lanai and other nearby islands. Consists of a lower layer of 

subrounded to rounded clasts of 5 percent white limestone and 95 

percent basalt, ranging in size from 3 em to 1 m, and an upper layer of 

subangular to angular clasts of basalt, ranging from 20 em to 1.5 m. 

Basalt boulders vary from vesicular to dense; limestone boulders are 

honeycomb coral, algae, and calcareous sandstone. Thickness and clast 

size decrease systematically with distance from shore and elevation. 

Overlies basaltic bedrock or fossil soil; upper surface consists of loose 

boulders. Similar deposits occur on other islands. Uranium-series age of 

the limestone clasts is Pleistocene (110 ka). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 137 

Humptulips Formation 

Eocene (Narizian) 

Washington 

Western Columbia basin 

Rau, W.W., 1984, The Humptulips Formation-A new Eocene formation of southwest 

Washington: Washington Geologic Newsletter, v. 12, no. 4, p. 1-5. 

Type locality: Exposures in the East Fork of the Humptulips River, 

from its confluence with the West Fork upstream to the volcanics of the 

Crescent Formation, Grays Harbor County, Wash. 

Strata in the northern part of the Grays Harbor basin, Washington, 

previously informally referred to as sedimentary rocks of late Eocene 

age are here named the Humptulips Formation. Consists of massive to 

thinly laminated sandy siltstone, mudstone, and sandstone that contain 

light-gray-weathering tuff beds. Unconformably overlies the Crescent 

Formation; conformably underlies the Lincoln Creek Formation. Correlates with the Skookumchuck and Mcintosh Formations in southwest 

Washington and the Aldwell Formation and Twin River Group to the 

north. Thickness is greater than 3,000 ft. Age is middle and late Eocene 

(N arizian) based on foraminifera. 

Hutchinson River Group 

Cambrian to Middle Ordovician 

New York, Connecticut 

New England province 

Baskerville, C. A., 1982, Adoption of the Hutchinson River Group and its subdivisions in 

Bronx and Westchester Counties, southeastern New York: U.S. Geological Survey 

Bulletin 1529-H, p. H1-H10. 

Type locality: Terrane traversed by the Hutchinson River, which flows 

from Scarsdale, Westchester County, to Eastchester Bay, Bronx 

County, N.Y. 

Subunits: Hartland Formation (New York and Connecticut) and its 

Pelham Bay Member (New York), Harrison Gneiss (New York and 

Connecticut). 

The Hutchinson River Group, here named, is in the Manhattan 

Prong in Westchester and Bronx Counties, N.Y., and Fairfield County, 

Conn. Contains the Hartland Formation and its Pelham Bay Member 

(new name) and four informal amphibolite, schist, and gneiss members, 

and the overlying Harrison Gneiss. Age is Cambrian to Middle 

Ordovician. 
138 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Hyatt Ranch Member of the Tensleep Formation 

Early Permian (Wolfcampian) 

Wyoming 

Big Horn basin 

Moore, D.A., 1984, The Tensleep Formation of the southeastern Big Horn basin, 

Wyoming, in Goolsby, Jim, and Morton, Doug, eds., The Permian and Pennsylvanian 

geology of Wyoming: Wyoming Geological Association 35th Annual Field Conference 

Guidebook, p. 273-279. 

Type locality: Exposures on either side of Hyatt Ranch on Paintrock 

Creek, center T. 50 N., R. 89 W., Big Horn County, Wyo. 

A distinctive widespread aeolian unit of the Tensleep Formation on 

the west flank of the Big Horn Mountains in the Big Horn and Wind 

River basins, Wyoming, is here named the Hyatt Ranch Member. 

Consists of white to light-gray and buff, fine- to occasionally coarsegrained, friable to cemented, subrounded, cross-stratified, aeolian 

sands in the uppermost 30 m of the Tensleep and represents the tops of 

preserved dunes. Overlies the Medicine Lodge Creek Member (new 

name) of the Tensleep with angular unconformity. Correlates with the 

upper member of the Minnelusa Formation. Exhibits distinctive 

changes in thickness. Age is possibly Early Permian (Wolfcampian). 

Ibex Formation 

Late Proterozoic 

California 

Great Basin province 

Wright, L.A., and Williams, E.G., 1984, Appendix II-Type section of the newly-named 

Proterozoic Ibex Formation, the basinal equivalent of the Noonday Dolomite, Death 

Valley region, California, in Wright, L.A., and Troxel, B.W., Geology of the northern 

half of the Confidence Hills 15-minute quadrangle, Death Valley region, eastern 

California: the area of the Amargosa chaos: California Division of Mines and Geology 

Map Sheet 34, p. 25-31. 

Type section: Exposures 2 km southwest of Ibex Spring and south of a 

jeep road that connects the spring with Buckwheat Wash to the west, 

immediately north of the south border of the southwestern quarter of 

the Shoshone 15-minute quadrangle, Death Valley region, San Bernardino County, Calif. 

The Noonday Dolomite in the Death Valley region, eastern California, grades abruptly southward into a markedly different succession of 

strata that have lithologies and bedding characteristics that indicate 

deposition in deep water. These strata, termed the basin facies of the 

Noonday Dolomite by Williams and others (1976), are here named the 

Ibex Formation and are mapped in the Confidence Hills quadrangle. 

Includes a lower conglomerate member, 5 m thick; overlain by a 

dolomite member, 8 m thick; an arkose member, 90 m thick; a limestone 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 139 

member, 21 m thick; a shaly limestone member, 23 m thick; and a 

dolomite member, 200 m thick. Total thickness is about 34 7 m. Overlies 

the Kingston Peak Formation; underlies the Johnnie Formation. Age is 

Late Proterozoic. 

Icicle Flat Member of the Saddle Mountains Basalt of the 

Columbia River Basalt Group 

Miocene 

Idaho 

Eastern Columbia basin 

Camp, V.E., 1981, Geologic studies of the Columbia Plateau: Part II. Upper Miocene 

basalt distribution, reflecting source locations, tectonism, and drainage history in the 

Clearwater embayment, Idaho: Geological Society of America Bulletin, v. 92, no. 9, 

pt. I, p. 669-678. 

Type locality: Icicle Flat, Nez Perce plateau, Lewis County, Idaho. 

The Icicle Flat Member of the Saddle Mountains Basalt of the 

Columbia River Basalt Group, here named, is in the Nez Perce plateau 

of the Clearwater embayment in Idaho. Consists of medium- to coarsegrained olivine basalt containing abundant plagioclase phenocrysts. 

Overlies the Asotin Member and underlies the Craigmont Member, 

both of the Saddle Mountains. Age is late Miocene. 

Indian Run Formation 

late Proterozoic or Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., 1985, Tectonic implications of the Indian Run Formation-A newly 

recognized sedimentary melange in the northern Virginia Piedmont: U.S. Geological 

Survey Professional Paper 1324, 12 p. 

Type locality: Exposures along Indian Run from just southeast of the 

intersection of Little River Turnpike and Evergreen Lane to the point 

at which the Run is crossed by Braddock Road, Annandale 7.5-minute 

quadrangle, Fairfax County, Va. 

The Indian Run Formation, here named, was previously mapped as 

the Sykesville Formation in Virginia. Is a precursory sedimentary 

melange having a quartz-plagioclase-muscovite-biotite-chlorite-garnet 

matrix containing abundant olistoliths of Accotink Schist (new name) 

and Lake Barcroft Metasandstone (new name) of the Annandale Group 

(new name). Melange is believed to have been emplaced by subaqueous 

sliding, but its base is not exposed and the unit serving as the slide 

surface is not known. Tectonically underlies the Annandale Group on 

the Red Fox thrust fault; is intruded by the Occoquan Granite. Age is 

Late Proterozoic or Cambrian based on isotopic ages from the Occoquan 

Granite. 
140 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Inman Yard Formation of the Atlanta Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Deep cuts on the north side of Inman Yard railroad yard 

west of Marietta Road, Atlanta, Northwest Atlanta quadrangle, Fulton 

County, Ga. 

The Inman Yard Formation, here named, is apparently the lowest 

unit in the Atlanta Group (new name) in the Newnan-Tucker synform in 

northern Georgia. Consists of interlayered gneiss, schist, and granite 

gneiss. Base of the unit is not exposed; underlies the Norcross Gneiss 

(new name) of the Atlanta with sharp and apparently conformable 

contact. Thickness is 700 m. Age is Late Proterozoic and (or) early 

Paleozoic. 

Intrenchment Creek Quartzite of the Atlanta Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Outcrops in excavations for the landfill beneath the 

powerline, just west of Intrenchment Creek, Southeast Atlanta quadrangle, De Kalb County, Ga. 

The Intrenchment Creek Quartzite of the Atlanta Group (new 

name), here named, is in the Newnan-Tucker synform in northern 

Georgia. Consists of a thin unit of spessartine quartzite and spessartine 

mica schist. Because of the manganiferous garnets, the rock weathers to 

blocky, hard black quartzite called coticule or gondite elsewhere. 

Sharply and conformably overlies the Clarkston Formation (new name) 

and underlies the Camp Creek Formation (new name) of the Atlanta. 

Thickness attains 3m. Age is Late Proterozoic and (or) early Paleozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 141 

Ironton Rhyolite of the St. Francois Mountains Volcanic 

Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: SWl/4 sec. 33, T. 34 N., R. 3 E., Ironton quadrangle, Iron 

County, Mo. 

Rocks previously mapped as the Lindsey Mountain composite ash 

flows and High Top bedded tuff by Anderson (1962) and Unit A of the 

tuff of Stouts Creek by Anderson (1970) are here named the Ironton 

Rhyolite. Occurs in the Taum Sauk Caldera in the western St. Francois 

Mountains in southeastern Missouri. Consists of dark-maroon to black 

ash-flow tuff containing phenocrysts of quartz and alkali feldspar. 

Overlies the Buck Mountain Shut-ins Formation (new name); underlies 

the Lindsey Mountain Rhyolite (new name). Thickness is 340m. Age is 

Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E. B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Ironton Rhyolite. 

lshi Tuff Member of the Tuscan Formation 

Pliocene 

California 

Sacramento basin 

Harwood, D.S., Helley, E.J., and Doukas, M.P., 1981, Geologic map of the Chico 

monocline and northeastern part of the Sacramento Valley, California: U.S. Geological 

Survey Miscellaneous Investigations Map I-1238, scale 1:62,500. 

Type locality: Exposures on the north rim of Big Chico Creek canyon, 

about 400 m northeast of Horseshoe Lake in Bidwell Park, city of Chico, 

T. 22 N., R. 2 E. Richardson Springs 15-minute quadrangle, 

Butte County, Calif. Named for Ishi Caves on the south wall of Deer 

Creek canyon, sec. 11, T. 25 N., R. 1 E., Panther Spring 15-minute 

quadrangle. 
142 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Ishi Tuff Member, here named, is in the western part of the 

Tuscan Formation along the northeastern side of the Sacramento Valley 

from Chico to Red Bluff, Calif. Consists of white to light-gray, finegrained, pumiceous airfall tuff composed of rhyolitic to dacitic glass and 

distinctive bronze-colored mica flakes commonly reworked and contains 

lenses and partings of sandstone and siltstone. Grades laterally into tan 

micaceous siltstone. Conformably overlies a layer of volcanic conglomerate, 2 to 3m thick, and locally, a layer of tan siltstone, 1m thick, at 

the top of unit B of the Tuscan; conformably and sharply underlies unit 

C lahar. Thickness is 0.3 m. Age is Pliocene based on stratigraphic 

relations. 

Island Park Rhyolite 

Pleistocene 

Idaho 

Snake River basin 

Christiansen, R.L., 1982, Late Cenozoic volcanism of the Island Park area, eastern Idaho, 

in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic geology of Idaho: Idaho 

Bureau of Mines and Geology Bulletin 26, p. 345-368. 

Type locality: Lookout Butte, Island Park area, Fremont County, 

Idaho. 

Six small rhyolite domes that crop out adjacent to the Henrys Fork 

caldera in Fremont County, Idaho, are here named the Island Park 

Rhyolite. The rhyolite domes are named the Moonshine Mountain, 

Silver Lake, Osborne Butte, Elk Butte, Lookout Butte, and Warm 

River Butte domes and are steep sided and endogenous and have 

shell-like flow-structure patterns parallel to their sides and concentric 

around their vents. Rhyolite contains large phenocrysts of quartz, sodic 

sanidine, sodic oligoclase, opaque oxides, ferroaugite, and fayalitic 

olivine. Domes are nearly buried by the younger Gerrit Basalt (new 

name) and are younger than the Mesa Falls Tuff and older than the Lava 

Creek Tuff. The Pleistocene Osborne Butte dome is dated at 1.3 Ma, the 

age of the second volcanic cycle. 

jack Creek Quartzite of the Phantom Lake Metamorphic 

Suite 

Archean 

Wyoming 

Green River basin 

Flurkey, A.J., Houston, R.S., Karlstrom, K.E., and Kratochvil, T.L., 1981, The geology 

of Archean and Early Proterozoic terranes of the Sierra Madre, Wyoming, in 

Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, eds., A summary of the 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 143 

geology and uranium potential of Precambrian conglomerates in southeastern Wyoming: U.S. Department of Energy National Uranium Resource Evaluation, v. 1, pt. 3, 

p. 403-531. 

Type locality: Exposures in Jack Creek Canyon and the cirque above 

North Spring Creek Lake, sees. 5, 8, and 9, T. 14 N., R. 86 W., Carbon 

County, Wyo. 

The Jack Creek Quartzite, here named, is modified from the 

informal Jack Creek Formation of Graff (1978) to include all of the 

metasedimentary rocks at the base of the Phantom Lake Metamorphic 

Suite in the northern Sierra Madre, Wyo. Consists of quartzite and 

lenses of phyllite, marble, paraconglomerate, quartz-pebble conglomerate, and metagraywacke. The informal Deep Gulch Conglomerate is a 

radioactive, crossbedded, pyritic quartz-pebble conglomerate facies at 

the base of the Jack Creek, which represents fluvial deposits in a 

braided river system. Units in the Jack Creek above the Deep Gulch are 

interpreted as a marine transgressional succession. Unconformably 

overlies the Continental Divide Metavolcanic Rocks (new name); underlies the Silver Lake Metavolcanic Rocks (new name) of the Phantom 

Lake. Thickness ranges from 300 to 800 m. Age is Archean. 

jacksonwald Basalt Member of the Brunswick Formation of 

the Newark Supergroup 

Early Jurassic (Hettangian) 

Pennsylvania 

Newark basin 

MacLachlan, D.B., 1983, Geology and mineral resources of the Reading and Birdsboro 

quadrangles, Berks County, Pennsylvania: Pennsylvania Topographic and Geological 

Survey Atlas 187cd, one sheet, scale 1:24,000. 

Type locality: Exposures south of the town of Jacksonwald, 4 mi 

southeast of Reading, Berks County, Pa. (Wherry, 1910). 

The Jacksonwald trap of Wherry (1910), here named the Jacksonwald Basalt Member of the Brunswick Formation [of the Newark 

Supergroup], occurs in the Jacksonwald syncline, Berks County, Pa. 

Consists of fine-grained, dark-gray basalt that has a vesicular top, 

chemically identical to chill margins of York Haven-type intrusives. 

Overlies the lower member and underlies the upper member of the 

Brunswick. May be too thick to be a single flow unit, but no internal 

divisions have been identified. Thickness is 500 ft. Age is Early Jurassic 

(Hettangian) based on pollen and spores, in the lower member of the 

Brunswick Formation, which place the Triassic-Jurassic boundary more 

than 50 ft but less than 130 ft below the basalt. 
144 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Jared Member of the Tiger Formation 

Eocene, Oligocene, and Miocene 

Washington 

Northern Cascade Range-Okanogan province 

Gager, B.R., 1983, Stratigraphy of the Tiger Formation, northeastern Washington: 

Northwest Geology, v. 12, p. 25-41. 

Type section: East-facing outcrop 1 km southwest of Jared, 

SElf4SElf4NElf4 sec. 11, T. 34 N., R. 42 E., Pend Oreille County, Wash. 

The Jared Member, here named, is in the revised Tiger Formation 

in the Cusick region of northeastern Washington. Consists of conglomerate containing clasts of two-mica granite and subordinate phyllitic 

metasedimentary rocks. Conformably overlies the Locke Member (new 

name) of the Tiger east of the Cusick Creek fault; unconformably 

overlies the Locke west of the fault. Correlates with the Calispell Lake 

Member (new name) of the Tiger and records erosion of older Tiger 

strata. Maximum thickness is 700 m. Age ranges from early middle 

Eocene based on inclusions of late early to early middle Eocene volcanic 

rock clasts through middle Miocene, based on middle Miocene regional 

faults that bound the Tiger Formation, although the age determination 

of middle Miocene is less definite. 

Jasper Point Formation 

Triassic(?) and Early Jurassic 

California 

Sierra Nevada province 

Bogen, N.L., 1985, Stratigraphic and sedimentologic evidence of a submarine island-arc 

volcano in the lower Mesozoic Penon Blanco and Jasper Point Formations, Mariposa 

County, California: Geological Society of America Bulletin, v. 96, no. 10, p. 1322-1331. 

Type section: Exposures at Jasper Point on the Merced River, Penon 

Blanco Peak quadrangle, Mariposa County, Calif. 

Rocks exposed in the core of the Cotton Creek anticline of Late 

Jurassic age in the southern part of the western Sierra Nevada 

metamorphic belt are here named the Jasper Point Formation. These 

rocks were previously included in the revised Penon Blanco Formation, 

and chert, here assigned to the Jasper Point, was called the informal 

Hunter Valley chert by Taliaferro (1943). Consists of a stratified 

sequence of more than 900 m of massive, pillowed, and brecciated basalt 

overlain by 100 m of red, white, brown, and black, rhythmically layered 

radiolarian chert, both altered to prehnite or chlorite grade. Is interbedded with and gradationally underlies the Penon Blanco Formation. 

Age is Early Jurassic or older based on a uranium-lead zircon age of the 

Don Pedro pluton, which intrudes the Jasper Point. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 145 

Jim Pond Formation 

Cambrian(?) and Early Ordovician(?) 

Maine 

New England province 

Boudette, E.L., 1982, Ophiolite assemblage of early Paleozoic age in central-western 

Maine, in St-Julien, P., and Beland, J., eds., Major structural zones and faults of the 

northern Appalachians: Geological Association of Canada Special Paper 24, p. 209-230. 

Type section: Composite of exposures along the North Branch of the 

Dead River, northern Franklin County, Maine. Named for Jim Pond, 

located 8 km above the confluence of the North Branch of the Dead 

River with Flagstaff Lake. 

Volcanic and metasedimentary rocks of the ophiolite sequence in 

central-western Maine are here named the Jim Pond Formation. 

Consists of a basal chlorite-albite-epidote-actinolite greenstone member 

that has minor amounts of metagraywacke, 150 to 500 m thick. 

Northwest of the Squirtgun fault it is divided into lower and upper units 

by a metadacite member in the east, 0 to 500 m thick, and a metagraywacke member in the west. The metadacite member is closely associated with hematitic chert iron-formation members. Greenstone is 

thickly layered with pillowed and massive flows. Patches of altered 

amphibolite are in undisturbed contact with the southeastern belt of 

tonalite of the Boil Mountain Complex (new name). Age is Cambrian(?) 

and Early Ordovician(?). 

Jim Sage Volcanic Member of the Salt Lake Formation 

Miocene 

Idaho 

Great Basin province 

Williams, P.L., Covington, H.R., and Pierce, K.L., 1982, Cenozoic stratigraphy and 

tectonic evolution of the Raft River basin, Idaho, in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic geology of Idaho: Idaho Bureau of Mines and Geology 

Bulletin 26, p. 491-504. 

Type locality: Southern Jim Sage Mountains, lat 42°05' to 42°08' N., 

long 113°28' to 113°32' W., Raft River basin, Cassia County, Idaho. 

Rhyolite flows in the southern Jim Sage Mountains are here named 

the Jim Sage Volcanic Member of the Salt Lake Formation. Consists of 

lower rhyolite flows; a middle breccia, ash-flow tuff, sandstone, shale, 

and siltstone unit; and upper rhyolite flows. Overlies the lower tuffaceous member and underlies the upper rhyolite member, both of the 

Salt Lake Formation. Maximum thickness is 1,200 m. Age is Miocene, 

based on radiometric dates of 11 to 9 Ma. 
146 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Johns Creek Quarry Member of the Scotch Grove Formation 

Early Silurian (Llandoverian, Telychian) 

Iowa 

Iowa shelf 

Johnson, M.E., 1983, New member names for the Lower Silurian Hopkinton Dolomite of 

eastern Iowa: Iowa Academy of Science Proceedings, v. 90, no. 1, p. 13-18. 

Type section: Johns Creek quarry, 6.5 km south of Farley, SElf4SWlf4 

sec. 36, T. 88 N., R. 2 W., Dubuque County, Iowa. 

Previously divided on the basis of paleontologic units, the Hopkinton 

Dolomite is here divided into lithologic members to facilitate interregional correlations based on sea-level curves. Rocks previously called 

the Bioherm Beds of the Hopkinton are here named the Johns Creek 

Quarry Member of the Hopkinton in eastern Iowa. Consists of a 

patch-reef facies and an interreef facies, each having distinctly different lithologies and fossil content. Reef mounds in the patch-reef facies 

are tan, massive, micritic dolomite, 7 to 10 m thick; the interreef facies 

is cream to tan, medium-bedded, finely crystalline dolomite, 3 to 5 m 

thick. Overlies the Picture Rock Member (new name) of the Hopkinton; 

underlies the Welton Member (new name) of the Hopkinton. Age is 

Early Silurian (Llandoverian, Telychian). 

Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River fault zone and 

the structural and stratigraphic framework of eastern Iowa: Iowa Geological Survey 

Technical Information Series 13, 126 p. 

The Johns Creek Quarry, Welton, and Buck Creek Quarry Members, all new names of Johnson (1983), are here reassigned from the 

upper part of the Hopkinton Dolomite to the lower part of the Scotch 

Grove Formation (new name). The Scotch Grove is defined between the 

Hopkinton and the Gower Formation for the purpose of preserving the 

original definitions of these units. 

Johnson Shut-ins Rhyolite of the St. Francois Mountains 

Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 147 

Type section: Exposures in the swimming area of Johnson Shut-ins 

State Park, NWl/4SWl/4 sec. 16, T. 33 N., R. 2 E., Johnson Shut-ins 

quadrangle, Reynolds County, Mo. 

Rocks previously mapped as Johnson ash-flow and air-fall tuffs by 

Anderson (1962) and as tuff of Johnson Shut-ins by Anderson (1970) are 

here named the Johnson Shut-ins Rhyolite. Occurs in the Taum Sauk 

Caldera in the western St. Francois Mountains of southeast Missouri. 

Consists of a lower unit of maroon ash-flow tuff containing quartz and 

feldspar phenocrysts, 23 m thick; a middle unit of crossbedded, waterdeposited tuff, 0 to 5 m thick; and an upper unit of gray ash-flow tuff 

containing quartz and feldspar phenocrysts, 27 m thick. Overlies the 

Proffit Mountain Formation (new name); underlies the Cope Hollow 

Formation (new name). Age is Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E.B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Johnson Shut-ins Rhyolite. 

Joker Peak Member of the Sunrise Formation of the Volcano 

Peak Group 

Early Jurassic (Pliensbachian) 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598-1608. 

Type locality: Exposures on the southern flank of Joker Peak, Gabbs 

Valley Range, Mineral County, Nev. 

The lower argillaceous part of the uppermost unit of Muller and 

Ferguson (1939) of the Sunrise Formation is here named the Joker Peak 

Member of the now revised Sunrise Formation of the Volcano Peak 

Group (new name) in the Gabbs Valley Range in west-central Nevada. 

Consists of medium-gray to brown mudstone and siltstone containing 

thin calcareous beds. Sharply and conformably overlies the New York 

Canyon Member (new name) of the Sunrise; conformably underlies the 

Mina Peak Member (new name) of the Sunrise; the contact is drawn at 

the lowest limestone beds. Thickness is 30 m. Age is Early Jurassic 

(Pliensbachian) based on fossils. 
148 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Joynes Neck Sand 

Pleistocene 

Virginia 

Atlantic Coast basin 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of uppermost Cenozoic 

deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological 

Survey Professional Paper 1067-G, 53 p. 

Type section: Borehole A-15, on county road 652 about 1.5 mi eastsoutheast of the town of Accomack and 0.5 mi southeast of the Edge Hill 

Cemetery, Joynes Neck area of Accomack County, Va. 

The Joynes Neck Sand, here named, occurs along the east side of the 

Delmarva Peninsula in Accomack and Northampton Counties, Va. 

Consists of yellowish-gray, loose, fine to coarse, surficial quartz sand, 

interstratified with beds of pebbly sand and gravel. Truncates and 

disconformably overlies the Accomack Member (new name) of the Omar 

Formation; may truncate or be equivalent to the Butlers Bluff and 

Occohannock Members of the Nassawadox Formation (all new names); 

is truncated along its eastern margin by Holocene barrier-lagoon 

complex deposits. Thickness at the type section is 30 ft. Age is 

Pleistocene. 

Juans Lake Beds of the Allison Member of the Menefee 

Formation of the Mesaverde Group 

late Cretaceous 

New Mexico 

San juan basin 

Miller, R.L., 1984, Subdivisions of the Menefee Formation and Cliff House Sandstone 

(Upper Cretaceous) in southwest SanJuan basin, New Mexico: U.S. Geological Survey 

Bulletin 1537-A, p. A29-A53. 

Type section: Exposures in the badlands area near Red Hill, SWI/4 to 

NEI/4 sec. 6, T. 22 N., R. 13 W., in the northeast part of The Pillar 3 SE 

7.5-minute quadrangle, San Juan County, N. Mex. Named for Juans 

Lake in the La Vida Mission quadrangle. 

The middle unit of the Allison Member of the Menefee Formation of 

the Mesaverde Group in the SanJuan basin, New Mexico, is here named 

the Juans Lake Beds. Consists predominantly of interbedded, partly 

crossbedded, fine-grained sandstone and gray mudstone containing 

ironstone concretions, petrified wood, carbonized tree trunks, and plant 

fragments. Is distinguished from the overlying La Vida Beds (new 

name) of the Allison Member by the inclusion of numerous large, round, 

calcareous concretions composed of gray cryptocrystalline limestone 

above and below sandstone units and by the absence of coal beds. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 149 

Overlies lower beds of the Allison Member; underlies the La Vida Beds. 

Thickness at the type section is 900 ft. Age is Late Cretaceous. 

Judds Falls Metabentonite 

Early Devonian (Helderbergian) 

New York 

Appalachian basin 

Conkin, J.E., and Conkin, B.M., 1984, Paleozoic metabentonites of North America: Part 

1-Devonian metabentonites in the eastern United States and southern Ontario (their 

identities, stratigraphic positions, and correlation): Kentucky, University of Louisville 

Studies in Paleontology and Stratigraphy, no. 16, 135 p. 

Type locality: Exposures along U.S. Highway 20, near an abandoned 

railway overpass, 0.4 mi east-southeast of the intersection of U.S. 

Highway 20 and N.Y. Highway 166, at Judds Falls, 2 mi northeast of 

Cherry Valley, Sprout Brook 7.5-minute quadrangle, Otsego County, 

N.Y. 

The Judds Falls Metabentonite, here named, is in Otsego County, 

N.Y. Consists of variegated, unctuous clay containing l-in-thick pyroclastic euhedral crystals. Has the appearance of the Onondaga Indian 

Nation Metabentonite, which is recognizable as far east as Cherry 

Valley. Lies 32 ft below the paracontinuous boundary of the Kalkberg 

Limestone and the Oriskany Sandstone. Age is Early Devonian 

(Helderbergian). 

Jumping Branch Manganiferous Member of the Battleground 

Formation 

late Proterozoic 

South Carolina, North Carolina 

Piedmont-Blue Ridge province 

Horton, J.W., Jr., 1984, Stratigraphic nomenclature in the Kings Mountain belt, North 

Carolina and South Carolina: U.S. Geological Survey Bulletin 1537-A, p. A59-A67. 

Type locality: Taylor clay pit on the west side of secondary road 123 

across from the western boundary of Kings Mountain National Military 

Park, lat 35°07'59" N., long 81°25'17" W., Cherokee County, S.C. 

Named for Jumping Branch, a tributary of Kings Creek, 4.1 km 

southwest of the type locality. 

The Jumping Branch Manganiferous Member of the Battleground 

Formation, here named, is in the Kings Mountain belt, South Carolina 

and North Carolina. Was described as the manganese schist member of 

the Battleground by Keith and Sterrett (1931). Consists of fine-grained 

equigranular spessartine-almandine garnet and quartz rock ( coticule or 

gondite) interlayered with quartz-sericite schist or phyllite. The duskybrown color of secondary oxides and hydroxides of manganese and iron 
150 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

in weathered rock and saprolite makes the Jumping Branch Member a 

distinctive marker unit. Overlies the Dixon Gap Metaconglomerate 

Member (new name) and underlies the Draytonville Metaconglomerate 

Member of the Battleground. Age is Late Proterozoic. 

Kahatchee Mountain Group 

Late Precambrian and Cambrian 

Alabama 

Piedmont-Blue Ridge province 

Tull, J.F., 1982, Stratigraphic framework of the Talladega slate belt, Alabama Appalachians, in Bearce, D.N., and others, eds., Tectonic studies in the Talladega and 

Carolina slate belts, southern Appalachian orogen: Geological Society of America 

Special Paper 191, p. 3-18. 

Type area: Southwestern part of the Talladega slate belt in southeast 

Shelby and northeast Chilton Counties, Ala. Named for the mountainous area northwest of Sylacauga. 

Subunits: Waxahatchee Slate, Sawyer Limestone, Brewer Phyllite, 

Wash Creek Slate. 

The Kahatchee Mountain Group, here named, is the lower sequence 

in the southwestern part of the Talladega slate belt in Alabama. 

Includes the Waxahatchee Slate, Sawyer Limestone, Brewer Phyllite, 

and Wash Creek Slate. Consists predominantly of pelitic slate, phyllite, 

and metasandstone and a minor carbonate unit. Underlies the Sylacauga Marble Group or the Lay Dam Formation of the Talladega Group. 

The Kahatchee Mountain Group may extend farther northeast in 

Alabama and into Georgia and may correlate with the Ocoee Supergroup and Chilhowee Group in the Blue Ridge belt. Age is Late 

Proterozoic and Cambrian. 

Kala Formation of the Cherokee Group of the Des Moines 

Supergroup 

Middle Pennsylvanian (Atokan and Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and VanDorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Exposures in bluffs along the Des Moines River, just west 

of the community ofKalo, SEl/4NWl/4SWl/4, sec. 17, T. 88 N., R. 28 W., 

Webster County, Iowa. 

Subunits: Blackoak Coal Member, Cliffland Coal Member. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 151 

The Kalo Formation, here named, occurs in the Cherokee Group of 

the Des Moines Supergroup and is recognized in most of southern and 

central Iowa. Includes two coal members: the basal Blackoak Coal 

Member (new name) and the overlying Cliffland Coal Member (new 

name). The remainder of the formation is predominated by fluvial and 

marginal marine deltaic sedimentary sequences of interlaminated sandstone, siltstone, and shale, which separate the coals and overlie the 

Cliffland. Overlies the Kilbourn Formation (new name); underlies the 

Floris Formation (new name). Thickness at the type section is about 50 

ft and ranges from 17 to 120 ft. Age is Middle Pennsylvanian (late 

Atokan to early Desmoinesian). 

Kalubik Formation of the Ugnuravik Group 

Early Cretaceous (Barremian and Aptian) 

Alaska 

Arctic Coastal Plains province 

Carman, G.J., and Hardwick, Peter, 1983, Geology and regional setting of Kuparuk oil 

field, Alaska: American Association of Petroleum Geologists Bulletin, v. 67, no. 6, 

p. 1014-1031. 

Type section: U gnu State 1 well, depth interval 5,670-5,890 ft b.r. t., in 

the Ugnuravik Group type section, Kuparuk field, Colville-Prudhoe 

basin, T. 12 N., R. 9 E., Umiat Base Line, Alaska. Named for Kalubik 

Creek, which flows into Harrison Bay west of the Kuparuk field. 

The Kalubik Formation of the U gnuravik Group (new name), here 

named, is in the Colville-Prudhoe basin, Alaska. Consists of brownishgray to black, carbonaceous, moderately fissile, locally sideritic, silty 

mudstone containing nodular and disseminated pyrite. Gradationally 

overlies the Kuparuk Formation (new name) of the U gnuravik; underlies the informal HRZ unit of the U gnuravik. Correlates with the lower 

part of the unnamed shale of Early Cretaceous age of Jones and Spears 

(1976) and Jamison and others (1980). Thickness ranges from 200 to 300 

ft. Age is Early Cretaceous (Barremian and Aptian) based on dinoflagellates and foraminifera. 

Kanauguk Formation 

Late Proterozoic 

Alaska 

Yukon-Koyokuck province 

Sainsbury, C.L., 1974, Geologic map of the Bendeleben quadrangle, Seward Peninsula, 

Alaska: U.S. Bureau of Mines, U.S. Geological Survey, and The Mapmakers, scale 

1:150,000, 31 p. 

Type area: Central York Mountains, western Seward Peninsula, Alaska 

(Sainsbury, 1969). [Probably named for the Kanauguk River.] 
152 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Kanauguk Formation, here named, was irrst described in the 

York Mountains by Sainsbury (1969) but is here recognized in many 

localities on the Seward Peninsula, Alaska. Consists of a thick, widespread unit of orange-weathering, thin-bedded, rhythmically interlayered argillaceous limestone and dolomitic limestone. Is schistose and 

contains veinlets of vitreous quartz where deformed. Conformably 

overlies the York Slate (new name) with a transitional boundary several 

hundred feet thick. Intensely deformed rocks are possibly mixed with 

the base of thrust sheets of Paleozoic(?) age. Age is at least in part Late 

Proterozoic based on a rubidium-strontium minimum age of 750 Ma for 

gneisses derived from the York. 

Kawkawlin Bentonite 

Middle Devonian 

Michigan 

Michigan basin 

Baltrusaitis, E.J., 1974, Middle Devonian bentonite in Michigan basin: American Association of Petroleum Geologists Bulletin, v. 58, no. 7, p. 1323-1330. 

Type section: Gulf Bateson 1 well, depth interval3,160-3,165 ft, center 

Sl/2SEl/4SEl/4 sec. 2, T. 14 N., R. 4 E., Kawkawlin oil field, Bay County, 

Mich. 

The Kawkawlin Bentonite, here named, is a distinctive, widespread 

bentonitic ash fall present in evaporite and carbonate sedimentary 

rocks of the Lucas Formation of the Detroit River Group in the 

subsurface of the Michigan basin, Michigan. Post-Detroit River emergence and erosion of the flanks of the basin have resulted in the 

truncation of the ash bed to its present limits. Consists of soft, friable, 

gray to greenish-gray montmorillonite(?) clay containing flakes of 

unaltered brown biotite and minor amounts of pyrite, chert, and 

glauconite. Another thin unnamed bentonite bed that does not contain 

biotite lies 50 ft above the Kawkawlin in the Lucas Formation. May be 

equivalent to the Tioga Bentonite of the Appalachian and Illinois basins. 

Thickness ranges from a few inches to 1 ft. Age is Middle Devonian. 

Keefus Till 

Pleistocene (Wisconsinan) 

Ohio 

Appalachian basin 

White, G.W., and Totten, S.M., 1979, Glacial geology of Ashtabula County, Ohio: Ohio 

Geological Survey Report of Investigations 112, 48 p. 

Type section: Exposure on the north bank of Conneaut Creek, 150 ft 

east of the Keefus Road bridge across Conneaut Creek, 1. 7 mi south of 

Lake Erie and 0.6 mi east of Amboy, Ashtabula County, Ohio. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 153 

The Keefus Till, here named, is in Ashtabula County, Ohio, where it 

crops out in many places and is recorded in drilling. Consists of 

dusky-red, hard, stony, calcareous till containing pebbles and small 

cobbles. Overlies the Devonian Chagrin Shale; underlies the Titusville 

Till or younger tills. Thickness at the type section is 3 ft. Age is 

Pleistocene (earliest Wisconsinan or older). 

Keensburg Coal Member of the Mattoon Formation of the 

Mcleansboro Group 

late Pennsylvanian (Missourian) 

Illinois 

Illinois basin 

Nance, R.B., and Treworgy, C.G., 1981, Strippable coal resources of Illinois: Part 8-

Central and southeastern counties: Illinois Geological Survey Circular 515, 32 p. 

Type section: Exposure on McClearys Bluff, 2.5 mi south of the village 

of Keensburg, NWl/4SWl/4SEl/4 sec. 29, T. 2 S., R. 13 W., Wabash 

County, Ill. 

Coal exposed at McClearys Bluff, Wabash County, Ill., here named, 

is the Keensburg Coal Member of the Mattoon Formation of the 

McLeansboro Group. Lies 7 ft above the McClearys Bluff Coal Member 

and 50 to 55 ft above the Friendsville Coal Member of the Mattoon 

Formation. Thickness at the type section is 1 ft. Age is Late Pennsylvanian (Missourian). 

Kellogg Creek Mafic Complex of the New Georgia Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C.E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures along Kellogg Creek, Kennesaw 7.5-minute 

quadrangle, southern Cherokee County, Ga. 

The informal Kellogg Creek metagabbro of McConnell and Costello 

(1980) is here named the Kellogg Creek Mafic Complex of the New 

Georgia Group (new name). This premetamorphic complex lies west of 

the outcrop area of the Laura Lake Mafic Complex (new name) of the 

New Georgia Group in the Greater Atlanta region, Georgia. Consists of 

garnet amphibolite, metagabbro, and minor amounts of meta-ultramafic 

rocks, and has no direct evidence of extrusive facies. Age is Late 

Proterozoic and (or) early Paleozoic. 
154 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Kelsey Tuff Member of the Kelseyville Formation 

Pleistocene 

California 

Northern Coast Range province 

Rymer, M.J., 1981, Stratigraphic revision of the Cache Formation (Pliocene and Pleistocene), Lake County, California: U.S. Geological Survey Bulletin 1502-C, p. Cl-C35. 

Type section: Roadcut along State Highway 29, 3.4 km south-southeast 

of the town of Kelseyville, SEl/4NEl/4 sec. 26, T. 13 N., R. 9 W., 

Kelseyville 7.5-minute quadrangle, Lake County, Calif. Named for 

Kelsey Creek. 

Tuff referred to as volcanic ash aquifer and aquifer ash in the Clear 

Lake area, Lake County, Calif., is here named the Kelsey Tuff Member 

of the Kelseyville Formation (new name). Consists of a bed of paleorange basaltic andesite lapilli tuff, 1. 0 to 1. 7 m thick, which, because of 

its distinctive character and presence throughout much of Big Valley, is 

a useful marker bed. The lower unit of the Kelsey, 20 to 30 em thick, 

consists of several thin beds of gray, fine-grained, vitric tuff and 

coarser, lithic tuff. The upper unit, 120 to 170 em thick, is an unsorted 

bed of pumiceous, gray, basaltic andesite lapilli tuff. Shows chemical 

affinity to flows of the Clear Lake volcanic field and possibly was 

erupted from a vent on Mount Konocti. Contains ground water under 

artesian pressure and is recognized in wells west and north of surface 

exposures of the Kelseyville Formation. Age is Pleistocene. 

Kelseyville Formation 

Pleistocene 

California 

Northern Coast Range province 

Rymer, M.J., 1981, Stratigraphic revision of the Cache Formation (Pliocene and Pleistocene), Lake County, California: U.S. Geological Survey Bulletin 1502-C, p. Cl-C35. 

Type section: Exposures along Kelsey Creek and along a ravine south of 

Kelseyville and west of State Highway 29, SEl/4NEl/4 sec. 27, 

NWl/4NWl/4 sec. 26, and SWl/4SWl/4 sec. 23, T. 13 N., R. 9 W., 

Kelseyville 7.5-minute quadrangle, Lake County, Calif. 

Subunit: Kelsey Tuff Member. 

Lacustrine and fluvial beds exposed near Kelseyville in the Clear 

Lake area, Lake County, Calif., which were previously assigned to the 

revised Cache Formation, are here named the Kelseyville Formation. 

Consists of yellowish-gray sandstone and siltstone, locally interbedded 

pebble conglomerate, and several tuff beds, including the Kelsey Tuff 

Member (new name), a marker bed. Overlies rocks of the Franciscan 

assemblage, locally overlies serpentinite, and locally intertongues with 

and overlies flows of the Clear Lake volcanic field; underlies Quaternary 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 155 

terrace deposits. Maximum thickness is at least 140m. Age is Pleistocene, between 0.64 and 0.13 Ma, based on potassium-argon ages of the 

underlying volcanic rocks and plant fossils. 

Kennesaw Gneiss Member of the laura lake Mafic Complex 

of the New Georgia Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C.E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures east of Kennesaw, Kennesaw 7.5-minute 

quadrangle, Cobb County, Ga. 

The informal Kennesaw gneiss of Hurst (1952) is here named the 

Kennesaw Gneiss Member of the Laura Lake Mafic Complex (new 

name) of the New Georgia Group (new name). Is a mappable unit of 

quartz diorite gneiss located along the western margin of Laura Lake in 

the Greater Atlanta region, Georgia. Quarried locally for aggregate 

near Kennesaw, Cobb County. Age is Late Proterozoic and (or) early 

Paleozoic. 

Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Lake bluff at the south edge of the city of Kewaunee, 

NEl/4SEl/4SEl/4 sec. 19, T. 23 N., R. 25 E., Kewaunee 7.5-minute 

quadrangle, Kewaunee County, Wis. 

Subunits: 

Lake Michigan Lobe: Ozaukee, Haven, Valders, and Two Rivers 

Members. 

Green Bay Lobe east of Fox River: Branch River, Chilton, and 

Glenmore Members. 

Green Bay Lobe west of Fox River: Silver Cliff, Kirby Lake, and 

Middle Inlet Members. 

The Kewaunee Formation, here named, occurs in the Lake Michigan 

and Green Bay Lobes in Wisconsin. In the Lake Michigan Lobe it is 

divided into the basal Ozaukee Member (new name) and the overlying 

Haven (new name), Valders, and Two Rivers Members. Members in the 

Green Bay Lobe east of the arbitrary vertical cutoff at the Fox River 
156 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

are the Branch River, Chilton, and Glenmore Members (all new names). 

West of the Fox River the Kewaunee is divided into the Silver Cliff, 

Kirby Lake, and Middle Inlet Members (all new names). Till of the 

Kewaunee is brown or reddish-brown, calcareous, sandy, silty, clay till. 

Overlies various members of the New Berlin Formation (new name) and 

Oak Creek Formation (new name) in the Lake Michigan Lobe, and the 

Horicon Formation (new name) in the Green Bay Lobe. Lies at the 

surface over much of northeast Wisconsin. Is equivalent to parts of the 

Wedron and Lake Michigan Formations in Illinois and younger parts of 

the Copper Falls Formation (new name) in northern Wisconsin. Thickness ranges from less than 1 m to more than 18 m. Age is Pleistocene 

(late Wisconsinan). 

Kilbourn Formation of the Cherokee Group of the 

Des Moines Supergroup 

Middle Pennsylvanian (Atokan) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and VanDorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Exposures in an abandoned quarry in NWlf4SE1/4 sec. 36, 

T. 70N., R.10W., VanBuren County, Iowa. Namedforthecommunity 

of Kilbourn in north-central Van Buren County. 

The Kilbourn Formation, here named, lies at the base of the 

Cherokee Group of the Des Moines Supergroup in central and southern 

Iowa. Strata are predominantly nonmarine sandstones, shales, and 

siltstones. Locally contains thin zones of limestone and thin, unnamed 

beds of coal that have little economic value. Unconformably overlies 

Mississippian St. Louis or Ste. Genevieve Limestones; underlies the 

Kalo Formation (new name) of the Cherokee. Thickness at the type 

section is approximately 20 ft; maximum measured thickness is 218 ft. 

Age is Middle Pennsylvanian (Atokan). 

Kimball Mountain Tuff Bed of the Parachute Creek Member, 

Anvil Points Member, Garden Gulch Member, or Douglas 

Creek Member of the Green River Formation 

Eocene 

Colorado 

Piceance basin 

Johnson, R.B., 1984, New names for units in the lower part of the Green River 

Formation, Piceance Creek basin, Colorado: U.S. Geological Survey Bulletin 1529-1, 

20 p. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 157 

Type section: West end of Kimball Mountain, SW1/4SE1/4 sec. 7, T. 7 S., 

R. 98 W., Long Point quadrangle, Garfield County, Colo. 

The Kimball Mountain Tuff Bed, here named, is in the Green River 

Formation. At the type section on Kimball Mountain, in the southwestern part of the Piceance Creek basin, Colorado, the bed is present at the 

base of the Parachute Creek Member but is also mapped in the Anvil 

Points, Garden Gulch, and Douglas Creek Members of the Green River. 

Consists of distinctive, light-buff to dark-gray tuff composed of hexagonal analcime surrounded by large crystals of sparry calcite. Occurs 60 

to 110m above the base of the Long Point Bed (new name), in the Green 

River. Thickness ranges from 1 to 15 em. Age is Eocene. 

Kingsbury limestone Member of the Great Meadows 

Formation of the Beekmantown Group 

Early Ordovician 

New York 

New England province 

Fisher, D. W., 1984, Bedrock geology of the Glens Falls-Whitehall region, New York: 

New York State Museum Map and Chart Series no. 35, 58 p. 

Type locality: None designated. [Possibly named for the town of 

Kingsbury, Washington County, N.Y.] 

The Kingsbury Limestone Member of the Great Meadows Formation of the Beekmantown Group is here named. Consists of massive, 

light-gray weathering, light- to medium-gray, fine- to medium-grained 

dolomitic limestone. Occurs as lenses and fissure fillings; fossils include 

algal heads. Overlies the Winchell Creek Siltstone Member and underlies the Fort Edward Dolostone Member, both of the Great Meadows. 

Thickness ranges from 0 to 12m. Age is Early Ordovician. 

Kingsley Cave Member of the Chico Formation 

late Cretaceous (Santonian) 

California 

Sacramento basin 

Haggart, J.W., and Ward, P.D., 1984, Late Cretaceous (Santonian-Campanian) stratigraphy of the northern Sacramento Valley, California: Geological Society of America 

Bulletin, v. 95, no. 5, p. 618--627. 

Type section: Exposures along Mill Creek, from NE1/4NW1/4 sec. 20 to 

SW1/4 sec. 19, T. 27 N., R. 2 E., Tehama County, Calif. Named for 

nearby Kingsley Cave. 

The Kingsley Cave Member of the Chico Formation is here named. 

Occurs along Deer, Mill, and Antelope Creeks, Tehama County, northeastern Sacramento Valley, Calif. Consists of greenish-gray to bluishgray, spheroidally weathered, heavily bioturbated, fossiliferous, muddy 
158 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

siltstone and silty mudstone containing rare pebble conglomerate beds 

as much as 1 m thick. Was deposited locally in quiet water conditions 

and may represent a marine connection with regions farther northeast. 

CoiTelates with the Dobbins Shale Member of the Forbes Formation of 

the western Sacramento Valley. Thickness is 350 m. Age is Late 

Cretaceous (late Santonian) based on ammonites. 

Kinkead Spring Limestone 

Early Mississippian (Osagean) 

Nevada 

Great Basin province 

Hose, R.K., Armstrong, A.K., Harris, A.G., and Mamet, B.L., 1982, Devonian and 

Mississippian rocks of the northern Antelope Range, Eureka County, Nevada: U.S. 

Geological Survey Professional Paper 1182, 19 p. 

Type section: E"xposures in SEl/4 sec. 20 and SWl/4 sec. 21, T. 16 N., 

R. 51 E., northern Antelope Range, Eureka County, Nev. Named for 

Kinkead Spring, 4 km southeast of the type section. 

The Kinkead Spring Limestone, here named, is in the northern 

Antelope Range, Nev. Consists of gray, olive-gray, and yellowish-gray, 

thin bedded to platy echinoderm-bryozoan-brachiopod packstone and 

grainstone containing clasts composed of peloids, ooids, skeletal fragments, foraminifers, algae, and quartz grains. Contains reworked 

conodonts of Late Devonian and Early Mississippian age. Was deposited in an open platform marine environment. Sharply and conformably 

overlies the Davis Spring Formation (new name); sharply and unconformably underlies the Antelope Range Formation (new name). Thickness is 160 m at the type section but may be more than 220 m because 

there is a thrust fault in the upper part of the formation. Age is Early 

Mississippian (middle(?) to late Osagean) based on conodonts. 

Kinnickinnic Member of the Pierce Formation 

Pleistocene (pre-Illinoian) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Stream bank 400 m north of Highway FF, SEl/4SWl/4SWl/4 

sec. 12, T. 27 N., R. 19 W., River Falls West 7.5-minute quadrangle, 

Pierce County, Wis. Named for the Kinnickinnic River in western St. 

Croix and Pierce Counties, terminating in the St. Croix River, 10 km 

north of Prescott. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 159 

The upper member of the Pierce Formation (new name) in westcentral Wisconsin is here named the Kinnickinnic Member. Consists of 

grayish-brown to dark-gray, thinly laminated, calcareous, silt loam of 

glacial lacustrine origin. Gradationally overlies the Hersey Member 

(new name) of the Pierce; sharply underlies the River Falls Formation 

(new name) or is exposed at the surface. Thickness is more than 21.m. 

Age is Pleistocene (pre-Illinoian). 

Kirby Lake Member of the Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Road cut on south side of Highway W, 0.16 km west of 

Kirby Lake Road, NE1/4NWV4SEV4 sec. 27, T. 32 N., R. 19 E., Crivitz 

7.5-minute quadrangle, Marinette County, Wis. Named for Kirby Lake 

15 km west of Crivitz. 

Following the informal usage of McCartney (1979), the Kirby Lake 

Member of the Kewaunee Formation (new name), here named, is in the 

Green Bay Lobe, west of the Fox River in Wisconsin. Consists of 

reddish-brown to yellowish-red sand-silt-clay till. Unconformably overlies pre-Pleistocene rocks or the Silver Cliff Member (new name) of the 

Kewaunee; unconformably underlies the Middle Inlet Member (new 

name) of the Kewaunee or is the surface unit. The contact with the 

equivalent Chilton Member (new name) of the Kewaunee Formation on 

the east side of the Green Bay Lobe is an arbitrarily drawn vertical 

cutoff at the Fox River. Thickness ranges from 1 m at the surface to 10 

min the subsurface. Age is Pleistocene (late Wisconsinan). 

Klamath River Conglomerate Member of the Hornbrook 

Formation 

late Cretaceous (Cenomanian and Turonian) 

California, Oregon 

Klamath Mountains province 

Nilsen, T.H., 1984, Tectonics and sedimentation of the Upper Cretaceous Hornbrook 

Formation, Oregon and California, in Crouch, J.K., and Bachman, S.B., eds., 

Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and Mineralogists, Pacific Section, v. 38, p. 101-118. 

Type section: Old open cut mine workings 0.4 km west of the Klamath 

River, west of Interstate Highway I-5, 0. 7 km southeast of the 
160 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

McCavick mine, SEl/4 sec. 32, T. 47 N., R. 6 W., Hornbrook 15-minute 

quadrangle, Siskiyou County, Calif. 

The Klamath River Conglomerate Member, here named, is the 

lowermost of five members of the Hornbrook Formation along the 

northeastern margin of the Klamath Mountains in Siskiyou County, 

Calif., and Jackson County, Oreg. Consists of brown- and redweathering gray, clast- and matrix-supported conglomerate and minor 

amounts of sandstone, siltstone, mudstone, and basal breccia deposited 

as laterally discontinuous alluvial-fan and braided-stream sediments. In 

places it forms a thin veneer at the base of the Hornbrook. U nconformably overlies pre-Cretaceous igneous and metamorphic rocks; conformably underlies the Osburger Gulch Sandstone Member (new name) of 

the Hornbrook. Thickness is 36.5 mat the type section and ranges from 

0 to 90 m. Age is early Late Cretaceous (Cenomanian and Turonian) and 

could possibly range from to Berriasian to Turonian based on molluskan 

fossils from the Osburger Gulch Sandstone Member. 

Klondike lake Conglomerate of the libby Creek Group 

Early Proterozoic 

Wyoming 

Green River basin 

Karlstrom, K.E., Houston, R.S., Coolidge, C.M., Flurkey, A.J., and Sever, O.K., 1981, 

The geology of Archean and Early Proterozoic terraines of the Medicine Bow 

Mountains, Wyoming, in Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, 

eds., A summary of the geology and uranium potential of Precambrian conglomerates 

in southeastern Wyoming: U.S. Department of Energy National Uranium Resource 

Evaluation, v. 1, pt. 2, p. 197-399. 

Type area: Northern Medicine Bow Mountains, Carbon County, Wyo. 

Derivation of name not stated. 

The Klondike Lake Conglomerate, here named, is in the Libby 

Creek Group and occurs in the Medicine Bow Mountains, Wyo. Consists 

of hematitic quartz-pebble conglomerate. Origin of iron-oxide grains in 

the conglomerate is uncertain, but the lack of other heavy minerals 

suggests deposition in lagoons on tidal flats. Lies 125 m below the top of 

the enclosing Medicine Peak Quartzite of the Libby Creek Group. Can 

be traced for 9 km. Thickness is 17 m. Age is Early Proterozoic. 

[Karlstrom and others (1983) refer to the unit as Klondike Lake 

Conglomerate Member of the Medicine Peak Quartzite of the Libby 

Creek Group of the Snowy Pass Supergroup.] 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 161 

Komatke Granite 

Precambrian 

Arizona 

Basin and Range province 

Reynolds, S.J., 1985, Geology of the South Mountains, central Arizona: Arizona Bureau 

of Geology and Mineral Technology Bulletin 195, 61 p. 

Type locality: Exposures at water tank on the southwest end of Main 

Ridge, South Mountains, sec. 33, T. 1 S., R. 2 E., Maricopa County, 

Ariz. Named for the village of Komatke, southwest of the South 

Mountains. 

The Komatke Granite, here named, is in the southwest ends of Main 

Ridge and Alta Ridge in the South Mountains, near Phoenix, Ariz. 

Consists of gray to pinkish, coarse-grained and porphyritic granite that 

has nearly vertical crystalloblastic foliation. Alaskitic and aplitic phases 

occur near its intrusive contacts with Estrella Gneiss (new name). Age 

is Precambrian. 

Kuna Formation of the Lisburne Group 

Early Mississippian to Early Pennsylvanian 

Alaska 

Arctic Foothills province 

Mull, C.G., Tailleur, I.L., Mayfield, C.F., Ellersieck, Inyo, and Curtis, S., 1982, New 

upper Paleozoic and lower Mesozoic stratigraphic units, central and western Brooks 

Range, Alaska: American Association of Petroleum Geologists Bulletin, v. 66, no. 3, p. 

348-362. 

Type locality: Exposures in the valley of an upper tributary of the Kuna 

River, SW1/4 sec. 21, T. 34 N., R. 5 E., western Howard Pass 

quadrangle, Endicott Mountains, Alaska. 

Rocks previously called the black Lisburne or dark colored facies of 

the Lisburne in the De Long and Endicott Mountains of the Brooks 

Range, Alaska, are here named the Kuna Formation of the Lisburne 

Group. Consists of black, sooty, phosphatic, carbonaceous shale, black 

chert, fine-grained limestone, and dolomite, usually more shaly at the 

bottom and more cherty at the top. Is nonresistant and is exposed only 

in cutbanks and on steep slopes. lntertongues eastward with the 

Wachsmuth and Alapah Limestones of the Lisburne Group. Conformably and gradationally overlies the Kayak Shale of the Endicott Group; 

disconformably or gradationally underlies the Siksikpuk Formation of 

the Etivluk Group (new name). Age is Early Mississippian to Early 

Pennsylvanian based on fossils. 
162 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Kuparuk Formation of the Ugnuravik Group 

Early Cretaceous (Valanginian to Barremian) 

Alaska 

Arctic Coastal Plains province 

Cannan, G.J., and Hardwick, Peter, 1983, Geology and regional setting of Kuparuk oil 

field, Alaska: American Association of Petroleum Geologists Bulletin, v. 67, no. 6, 

p. 1014-1031. 

Type section: Ugnu State 1 well, depth interval 5,890-6,262 ft b.r.t., 

type section of the Ugnuravik Group, Kuparuk field, Colville-Prudhoe 

basin, T. 12 N., R. 9 E., Umiat Base Line, Alaska. Named for the 

Kuparuk River, which flows north into Gwydwr Bay. 

The Kuparuk Formation of the U gnuravik Group (new name), here 

named, is in the Kuparuk field in the Colville-Prudhoe basin, Alaska. 

Consists of a cyclic sequence of coarse- and fine-grained terrigenous 

clastic sediments informally subdivided into a lower member having A 

and B units characterized by thinly interbedded sandstone, siltstone, 

and mudstone and an upper member having a C unit characterized by 

massive sandstone and siltstone and a D unit characterized by silty 

mudstone. Gradationally overlies the Miluveach Formation (new name) 

and gradationally underlies the Kalubik Formation (new name), both of 

the U gnuravik Group. Correlates with the Kongakut Formation to the 

east, the Okpikruak Formation to the south, and the Put River 

Sandstone (new name) in the Prudhoe Bay field. [The informal name 

Kuparuk River sands was used by Fackler and others (1970), who 

designated the type section as the Mobil-Phillips North Kuparuk State 

1 well, depth interval6,774-7,054 ft, in the Prudhoe Bay field, T. 12 N., 

R. 12 E., Umiat Base Line. Referred to as the Kuparuk River 

Formation by Jones and Spears (1976). Formal usage was implied by 

Jamison and others (1980), who described the Kuparuk River Formation in the Prudhoe Bay field where it consists of three sand members 

termed Lower, Middle, and Upper Sands, separated by shales and silty 

shales. At Prudhoe Bay, it conformably overlies the Kingak Shale and 

unconformably underlies unnamed Lower Cretaceous shale.] Hydrocarbon reserves of the Kuparuk and Prudhoe Bay fields occur in the 

Kuparuk Formation. Age is Early Cretaceous (Valanginian to Barremian) based on dinoflagellates. Foraminifers of mixed Late Jurassic and 

Early Cretaceous ages suggest that the Kuparuk may represent continuous deposition in the Late Jurassic and Early Cretaceous (Jamison 

and others, 1980). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 163 

Laddsdale Member of the Floris Formation of the Cherokee 

Group of the Des Moines Supergroup 

Middle Pennsylvanian 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and VanDorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Stream cut on Soap Creek, SEl/4SEl/4NWl/4 sec. 17, 

T. 70 N., R. 12 W., northeastern Davis County, Iowa. Named for the 

abandoned mining community of Laddsdale, Davis County. 

The Laddsdale Member, here named, is the lower of two members 

of the Floris Formation (new name) of the Cherokee Group of the Des 

Moines Supergroup in south-central Iowa. The type section contains 

four coal beds that are 8. 6 ft thick and are distributed through 30 ft of 

strata at the base of the Floris. Strata associated with the coals are 

nonmarine shales and siltstones, a thin fossiliferous marine shale above 

the second coal, and a fossiliferous marine limestone at the upper 

contact of the member. Other areas contain six coal beds representing 

six depositional cycles. Overlies the Kalo Formation (new name); 

underlies a fossiliferous limestone historically referred to as the informal Laddsdale limestone and correlated with the Seville Limestone of 

Illinois. Age is Middle Pennsylvanian. 

Lady Slipper Granulite Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Sinha, A.K., and Bartholomew, M.J., 1984, Evolution of the Grenville terrane in the 

central Virginia Appalachians: Geological Society of America Special Paper 194, 

p. 175-186. 

Type section: Outcrop on U.S. Highway 60, 400 m east of its junction 

with the Blue Ridge Parkway, lat 37°44'30" N., long 79°18' W., Buena 

Vista 7.5-minute quadrangle, Rockbridge County, Va. Derivation of 

name not stated. 

The Lady Slipper Granulite Gneiss, here named, is a sequence of 

metavolcanic rocks in the Pedlar massif in the western parts of the 
164 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Buena Vista and Cornwall quadrangles, Virginia. Consists of lightgray, medium-grained, layered to massive gneiss containing quartz, 

plagioclase, hypersthene, garnet, and biotite. Is intruded by the Pedlar 

River Charnockite Suite (new name). Age is Middle Proterozoic based 

on a concordia intercept age of 1, 130 Ma. 

Lajas Formation 

late Cretaceous (Campanian) 

Puerto Rico 

Volckmann, R.P., 1984, Upper Cretaceous stratigraphy of southwest Puerto Rico: A 

revision: U.S. Geological Survey Bulletin 1537-A, p. A73-A83. 

Type locality: Exposures at the abandoned railway station at the 

intersection of Roads 116 and 315 in the town of Lajas, San German 

7.5-minute quadrangle, southwestern Puerto Rico. 

Rocks in southwestern Puerto Rico, previously mapped as the lower 

part of the San German Formation as defined by Mattson (1960), are 

here named the Lajas Formation. The San German Formation is now 

abandoned and its Cotui Limestone Member is raised to formation rank 

as the Cotui Limestone. The Lajas consists of basal volcanic wacke 

overlain by grayish-red to grayish-purple, porphyritic lava and tuff 

containing labradorite and oxyhornblende phenocrysts in a fine-grained 

matrix of plagioclase, magnetite, hematite, and actinolite. Lack of 

pillows in the lava suggests subaerial deposition. The base of the Lajas 

is interlayered with volcanic wacke identical to volcanic wacke at the top 

of the Boqueron Basalt (new name), which it appears to overlie with 

minor disconformity. Underlies the Cotui Limestone with an apparently 

slight disconformity. Thickness is more than 1,000 m. Age is Late 

Cretaceous, probably middle Campanian or older, based on fossils in the 

overlying Cotui. 

La Jencia Tuff 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: East slope of a west-dipping hogback on the west side of 

LaJencia basin, 6.5 mi north of Magdalena and 1.8 mi southeast of Bear 

Springs, NWl/4 sec. 22, T. 1 S., R. 4 W., southern Bear Mountains, 

Magdalena NW 7.5-minute quadrangle, Socorro County, N.Mex. 

Rocks in the northeast Mogollon-Datil volcanic field in southwestern 

New Mexico, formerly called the lower cooling unit of the tuff of Bear 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 165 

Springs, A-L Peak Tuff, now abandoned, and Potato Canyon Rhyolite 

Tuff, now abandoned, are here named the La J en cia Tuff. Consists of 

multiple flows of crystal-poor, moderately to densely welded, rhyolite 

ash-flow tuff containing well developed primary flow structures; lineated pumice, lithic fragments, and exotic blocks. Overlies the Hells 

Mesa Tuff and the Luis Lopez Formation (new name); underlies the La 

Jara Peak Basaltic Andesite, Sawmill Canyon Formation (new name), 

or Vicks Peak Tuff. Thickness attains 3,000 ft; base is not exposed. Age 

is Oligocene based on its stratigraphic position between two dated units. 

Lake Barcroft Metasandstone of the Annandale Group 

Late Proterozoic or Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., and Lyttle, P.T., 1981, The Accotink Schist, Lake Barcroft Metasandstone, and Popes Head Formation-Keys to an understanding of the tectonic evolution 

of the northern Virginia Piedmont: U.S. Geological Survey Professional Paper 1205, 

16 p. 

Type locality: Exposures at the confluence of and along the Holmes Run 

and Tripps Run arms of Lake Barcroft, Annandale quadrangle, Fairfax 

County, Va. 

The Lake Barcroft Metasandstone, here named, is the upper unit of 

the informal Eastern Fairfax sequence, the structurally lowest metamorphic rocks in northern Virginia. Consists of two types of metasandstone: Type I meta-arenite, thick-bedded quartzofeldspathic granofels 

having no interbedded pelite; Type II thin- to medium-bedded micaceous metagraywacke that has pelitic layers. Gradationally overlies the 

Accotink Schist (new name) of the Eastern Fairfax sequence; underlies 

the Sykesville Formation, which contains exotic blocks of Lake Barcroft 

Metasandstone and is believed to have been emplaced by subaqueous 

sliding on the top of the Lake Barcroft. Is intruded by Early Cambrian 

Occoquan Granite. Thickness is about 400 m. 

Drake, A.A., Jr., 1985, Tectonic implications of the Indian Run Formation-A newly 

recognized sedimentary melange in the northern Virginia Piedmont: U.S. Geological 

Survey Professional Paper 1324, 12 p. 

The Lake Barcroft Metasandstone is the upper unit of the Annandale Group (new name), originally called the informal Eastern Fairfax 

sequence of Drake and Lyttle (1981). The lower unit of the Annandale 

Group, the Accotink Schist (new name), and the Lake Barcroft lie 

between two melanges, the newly recognized lower Indian Run Formation (new name) and the upper Sykesville Formation. Fragments of 

Accotink and Lake Barcroft are restricted to an area of melange 

originally defined as Sykesville but now considered to be a separate 

unit, the Indian Run. Age is Late Proterozoic or Cambrian. 
166 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Lake Chelan Metabentonite 

Early and Middle Devonian (Onesquethawan) 

Indiana, Kentucky 

Cincinnati arch 

Conkin, J.E., and Conkin, B.M., 1984, Paleozoic metabentonites of North America: Part 

1-Devonian metabentonites in the eastern United States and southern Ontario: Their 

identities, stratigraphic positions, and correlation: University of Louisville Studies in 

Paleontology and Stratigraphy, no. 16, 135 p. 

Type locality: North wall of abandoned Sellersburg Stone Quarry 

(Denton and Voyles Quarry), Speed 7.5-minute quadrangle, Clark 

County, Ind. Named for Lake Chelan, across the road from the quarry. 

The Lake Chelan Metabentonite, here named, is a metabentonite 

present in stylolitic seams associated with unit 2 of bone bed 4 of the 

Jeffersonville Limestone of southern Indiana and northwestern Kentucky. Occurs 5.8 ft below the Tioga Metabentonite, 5.5 ft above the 

Onondaga Indian Nation Metabentonite, and 16 ft above the Kawkawlin 

Metabentonite [Bentonite] (new name) in southern Indiana. Age is 

Early and Middle Devonian (Onesquethawan). 

Lake George Formation of the Saginaw Group 

Early Pennsylvanian (Morrowan) 

Michigan 

Michigan basin 

Vugrinovich, Ray, 1984, Lithostratigraphy and depositional environments of the Pennsylvanian rocks and the Bayport Formation of the Michigan basin: Michigan Geological 

Survey Division, Report of Investigation 27, 33 p. 

Type section: Michigan Consolidated Gas Company Number L-124 well, 

depth interval 764-885 ft, NW1/4NW1/4NW1/4 sec. 21, T. 18 N., R. 5 W., 

Lincoln Township, Clare County, Mich. Named for the nearby village of 

Lake George. 

The Lake George Formation of the Saginaw Group, here named, is 

in the subsurface of the Michigan basin. Consists of white to yellowishgray to grayish-red, fine- to coarse-grained, friable, quartz sandstone 

and grayish-brown massive claystone containing local shale and siltstone. Overlies the Hemlock Lake Formation (new name) and gradationally underlies the Winn Formation (new name), both of the Saginaw 

Group. The deposits are channel fill sediments. Thickness at the type 

section is 121 ft. Age is Early Pennsylvanian (Morrowan). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 167 

lake George Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type area: Exposures in the area north and west of Lake George, 

Warren County, N.Y. 

Subunits: 

Eastern Adirondacks: Eagle Lake Gneiss, Paradox Lake, Treadway 

Mountain, Lake Durant, Springhill Pond, Thunderbolt Mountain 

Formations. 

Southern Adirondacks: Sacandaga Formation, Lake Durant Formation, Tomany Mountain Formation, Rooster Hill Megacrystic Gneiss, 

Peck Lake Formation, Green Lake Formation, Canada Lake Charnockitic Gneiss, Irving Pond Formation. 

Metamorphosed sedimentary rocks in the Adirondack Mountains, 

N.Y., are here named the Lake George Group. In the eastern Adirondacks it includes, in ascending order, the Eagle Lake Gneiss (new 

name), Paradox Lake (new name), Treadway Mountain (new name), 

Lake Durant, Springhill Pond (new name), and Thunderbolt Mountain 

(new name) Formations. In the southern Adirondacks it includes the 

Sacandaga, Lake Durant, and Tomany Mountain Formations, Rooster 

Hill Megacrystic Gneiss, Peck Lake and Green Lake Formations, 

Canada Lake Charnockitic Gneiss, and Irving Pond Formation. Unconformably overlies the Piseco Group (new name) in the central, eastern, 

and southern Adirondacks. In the central Adirondacks the Cedar River, 

Lake Durant, Blue Mountain Lake, and Little Moose Mountain Formations are correlated with the southern Adirondack sequence but these 

units are not specifically assigned to the Lake George Group. Correlates with the Oswegatchie Group in the Northwest Lowlands. 

Regional metamorphism occurred during the Grenville orogeny. Age is 

Proterozoic. 

lake Katrine Member of the Port Ewen Formation of the 

Helderberg Group 

Early Devonian 

New York 

Appalachian basin 

Mazzo, C.R., and LaFleur, R.G., 1984, Stratigraphy of the Port Ewen Formation (Lower 

Devonian), eastern New York: Northeastern Geology, v. 6, no. 2, p. 71--82. 
168 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Roadcut on New York Route 199, 1.02 km west of the 

Kingston-Rhinecliff Bridge across the Hudson River, Kingston, Ulster 

County, N.Y. 

The Lake Katrine Member, here named, is the lower of two 

members of the Port Ewen Formation of the Helderberg Group in the 

Silurian-Devonian· outcrop belt in eastern New York. Consists of 

dark-gray- to brown-weathering, fissile to hackly, burrow mottled, 

nonresistant, platy claystone, mudstone, and shale containing bioclastic 

debris and coarse-grained carbonate at the base. Transitionally overlies 

the Alson Formation; underlies the East Kingston Member (new name) 

of the Port Ewen. Thickness at the type section is 6 m. Age is Early 

Devonian. 

Lanier Mountain Quartzite Member of the Snellville Formation 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Roadcut and natural outcrops on Lanier Mountain, 

Snellville quadrangle, Gwinnett County, Ga. 

The Lanier Mountain Quartzite Member, here named, is the upper 

member of the Snellville Formation (new name) in the Newnan-Tucker 

synform near Atlanta, Ga. Consists of quartzite ranging in composition 

from quartz through muscovitic quartzite to garnetiferous, sillimanitic, 

muscovitic quartzite. Overlies the Norris Lake Schist Member (new 

name) of the Snellville and is probably younger than the Atlanta Group 

(new name). Age is Late Proterozoic and (or) early Paleozoic based on 

a maximum age of 1,100 Ma from detrital zircons. 

Las Animas Formation 

Middle Proterozoic 

Colorado 

las Vegas-Raton basin 

Tweto, Ogden, 1983, Las Animas Formation (Upper Precambrian) in the subsurface of 

southeastern Colorado: U.S. Geological Survey Bulletin 1529-G, 14 p. 

Type section: R.W. Lange Number 1 Government test well, depth 

interval 2,045-6,210 ft, SWlf4NWlf4 sec. 10, T. 29 S., R. 62 W., 

Las Animas County, Colo. Reference section: Upper part: Phillips 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 169 

Petroleum Company Number 1 E.W. Haskins well, depth interval 

1,115-2,570 ft, NE1/4NE1/4 sec. 23, T. 29 S., R. 56 W. Named for Las 

Animas County. 

A sequence of slightly to moderately metamorphosed sedimentary 

and igneous rocks that occurs only in the subsurface in a belt 80 mi long 

and up to 30 mi wide in southeastern Colorado is here named the Las 

Animas Formation. Consists mainly of dark-gray to black slate, phyllite, dark-gray fine-grained graywacke, and recrystallized chert. Carbonate and volcanic rocks are present in the upper part. Overlies(?) 

Precambrian granite dated at 1,400 to 1,300 Ma; unconformably underlies Permian Sangre de Cristo Formation at the type section; unconformably underlies Upper Cambrian Reagan Sandstone at the reference 

section. Thickness, unknown because the base of the formation has not 

been reached, is probably more than 5,575 ft. Age is Middle Proterozoic. 

Laura Lake Mafic Complex of the New Georgia Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.l., and Abrams, C. E., 1984, Geology ofthe Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures near Laura Lake, Kennesaw 7.5-minute 

quadrangle, eastern Cobb County, Ga. 

Subunit: Kennesaw Gneiss Member. 

The largest premetamorphic intrusive-extrusive complex in the 

Piedmont portion of the Greater Atlanta region, Georgia, is here named 

the Laura Lake Mafic Complex of the New Georgia Group (new name). 

Includes the Kennesaw Gneiss Member (new name), a unit of quartz 

diorite gneiss, along the western margin. Consists of migmatitic garnet 

amphibolite, clinopyroxene, felsic gneiss, metagabbro, meta-ultramafic 

rocks, and a banded iron formation. Is separated from the outcrop belt 

of the New Georgia Group by a thin strip of rocks of the Sandy Springs 

Group. Because of lithologic similarities to the New Georgia, the Laura 

Lake is believed to represent a slice of the New Georgia that, along with 

the Sandy Springs, was thrust over other units of the New Georgia. Age 

is Late Proterozoic and (or) early Paleozoic. 

Laurel Branch Limestone 

Mississippian 

Tennessee 

Appalachian basin 

Brent, W.B., 1982, Mississippian stratigraphy of Greendale and Newman Ridge synclines 

and Middle Ordovician nomenclature in upper east Tennessee: Tennessee Division of 

Geology Report of Investigations 41, 37 p. 
170 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Exposures on a hillside east of a sinkhole 0.4 km 

northwest of the intersection of State Highway 94 and a county road 

parallel to Laurel Branch (stream) and 0.4 km northeast of Laurel View 

Church, Camelot quadrangle, Hawkins County, Tenn. 

The Laurel Branch Limestone, informally named by Sanders (1952), 

is here named. These Mississippian strata in the Greendale syncline in 

Hawkins and Grainger Counties, Tenn., were previously named Newman Limestone by Hardeman and others (1966) but are isolated from 

the type Newman Limestone in the Newman Ridge syncline. Consists 

of gray fine-grained limestone containing nodules and lenses of black 

chert and a distinctive zone, 4.5 m thick, of calcareous siltstone and 

shale. Overlies the Pressmens Home Formation (new name); underlies 

the Snow Flake Formation (new name). Correlates with the lower part 

of the St. Louis Limestone. Thickness is 24 m. Age is Mississippian. 

La Vida Beds of the Allison Member of the Menefee Formation 

of the Mesaverde Group 

Late Cretaceous 

New Mexico 

San Juan basin 

Miller, R.L., 1984, Subdivisions of the Menefee Formation and Cliff House Sandstone 

(Upper Cretaceous) in southwest SanJuan basin, New Mexico: U.S. Geological Survey 

Bulletin 1537-A, p. A29-A53. 

Type section: Exposures in the Red Hill-White Rock region, from the 

northeast corner of sec. 31 to the north central part of sec. 30, T. 22 N., 

R. 13 W., Pillar 3 SE 7. 5-minute quadrangle, SanJuan County, N. Mex. 

Named for La Vida Mission Indian School, San Juan County. 

The fluvial upper unit of the Allison Member of the Menefee 

Formation of the Mesaverde Group in northwest New Mexico is here 

named the La Vida Beds. Consists of olive-gray and dark-brown 

mudstone, olive-gray siltstone, dark-gray shale, and gray, fine-grained 

sandstone containing petrified wood and ironstone concretions. Lenticular coal beds, most of which are more than 1 ft thick, are in the upper 

part of the unit. Overlies the Juans Lake Beds (new name) of the Allison 

Member; underlies the Cliff House Sandstone. Thickness is 232 ft at the 

type section. Age is Late Cretaceous. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 171 

Lavon Member of the Pecan Gap Formation of the Taylor 

Group 

late Cretaceous (Campanian) 

Texas 

Ouachita tectonic belt province 

McNulty, C.L., Brezina, J.L., Dawson, W.C., and Maluf, F.W., 1981, Emendation of the 

Pecan Gap Chalk (Campanian) in northeast Texas: Gulf Coast Association of Geological 

Societies Transactions, v. 31, p. 353-358. 

Type section: Exposures along Bear Creek about 1. 0 mi east of the town 

of Lavon, Collin County, Tex. (Maluf, 1975). 

Rocks informally named the Bear Creek member by Maluf (1975) are 

here named the Lavon Member of the revised Pecan Gap Formation of 

the Taylor Group. Is in the north-south belt of outcrop in Collin and 

Rockwall Counties, Tex., and can be traced, with the Rockwall Member 

(new name) of the Pecan Gap, between Farmersville and southern 

Rockwall County. Consists of light-gray, white-weathering, obscurely 

bedded, silty chalk and calcarenite containing poorly defined trace 

fossils. Disconformably overlies the Rockwall Member; sharply underlies the Marl brook Formation. May become the Pecan Gap Chalk of the 

west-southwest belt of outcrop. Thickness at the type section is 30 ft. 

Age is Late Cretaceous (Campanian). 

Leader Lake Quartz Monzonite 

late Cretaceous 

Washington 

Northern Cascade Range-Okanogan province 

Menzer, F.J., Jr., 1983, Metamorphism and plutonism in the central part of the Okanogan 

Range, Washington: Geological Society of America Bulletin, v. 94, no. 4, p. 471-498. 

Type locality: Exposures on the knolls southeast of Leader Lake, 

T. 33 N., R. 25 E., Okanogan County, Wash. 

A postmetamorphic, orthomagmatic stock in the central Okanogan 

Range, Wash., is here named the Leader Lake Quartz Monzonite. 

Consists of fine- to medium-grained rocks composed of equal amounts of 

quartz, zoned oligoclase, and microcline and minor amounts of biotite 

and muscovite. Intrudes the Conconully Granodiorite (new name), but a 

combined rubidium-strontium mineral isochron age of 81 Ma is considered to be evidence that it is a slightly younger differentiate of the same 

parental magma as the Conconully. Age is Late Cretaceous. 
172 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

lees Summit Formation of the Pleasanton Group 

Late Pennsylvanian (Missourian) 

Missouri, Iowa 

Forest City basin 

Howe, W.B., 1982, Stratigraphy of the Pleasanton Group, Pennsylvanian System in 

Missouri: Missouri Department of Natural Resources, Open File Report Series 

OFR-82-10-GI, 99 p. 

Type section: Section in Acme Brick and Tile Company shale quarry at 

Vale, NE1/4NE1/4 sec. 27, T. 48 N., R. 32 W., Jackson County, Mo. 

Named for the city of Lees Summit, Jackson County. 

Subunits: Exline Limestone Member, Unity Farm Shale Member. 

The Lees Summit Formation of the Pleasanton Group, here named, 

is in the Forest City basin in northwestern Missouri. Includes the basal 

Exline Limestone Member and the upper Unity Farm Shale Member 

(new name). The Exline Limestone Member, here reduced from formation rank in the Pleasanton Group in Missouri, consists of fossiliferous, 

massive, laminated algal limestone and silty calcareous shale containing 

masses of crinoidallimestone. Forms the floor of shale quarries in Cass, 

Jackson, and Livingston Counties, Mo., and Appanoose County, Iowa. 

The Unity Farm Shale Member is the shale overlying the Exline 

Member. The Lees Summit overlies the South Mound Shale Member of 

the Seminole Formation and unconformably underlies the Weldon River 

Sandstone Member (new name) of the Shale Hill Formation (new name). 

Thickness at the type section is 65ft. Age is Late Pennsylvanian (early 

Missourian). 

Lehigh Acres Formation of the Glades Group 

Early Cretaceous (Comanchean) 

Florida 

South Florida province 

Applegate, A.V., Winston, G.O., and Palacas, J.G., 1981, Subdivision and regional 

stratigraphy of the Pre-Punta Gorda rocks (Lowermost Cretaceous-Jurassic(?)) in 

south Florida: Gulf Coast Association of Geological Societies, October Transactions 

(supplement), v. 31, p. 447-453. 

Type section: Humble Number 1 Lehigh Acres well P-407, depth 

interval12,250-12,800 ft, sec. 14, T. 45 S., R. 27 E., Lee County, Fla. 

Named for the nearby community of Lehigh Acres. 

Subunits: West Felda Shale Member, Twelve Mile Member, Able 

Member. 

The Lehigh Acres Formation of the Glades Group, here named, is in 

the subsurface of the South Florida basin. Includes the West Felda 

Shale Member (new name), a gray, calcareous shale unit; the Twelve 

Mile Member (new name), a limestone unit containing the brown 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 173 

dolomite zone; and the Able Member (new name), an anhydrite and 

limestone unit that is the uppermost of four regionally persistent 

anhydrite units below the Punta Gorda Anhydrite of the Glades Group. 

Overlies the Pumpkin Bay Formation (new name); underlies the Punta 

Gorda Anhydrite. Thickness at the type well is 550 ft and ranges from 

530 to 740 ft in the downdip portion of the basin. Age is Early 

Cretaceous (earliest Comanchean). 

Lemitar Tuff 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: Tributary canyon on the north side of Canoncito de 

Puertecito del Lemitar (Corkscrew Canyon), 8 mi northwest of Socorro, 

NW1/4SE1/4SE1/4 sec. 12, T. 2 S., R. 2 W., Lemitar Mountains, Lemitar 

7.5-minute quadrangle, Socorro County, N. Mex. 

Rocks in the San Mateo, Magdalena, Lemitar, and Chupadera 

Mountains, J oyita Hills, and northern J ornada del Muerto, N. Mex., 

formerly called Potato Canyon Rhyolite Tuff (name now abandoned), 

are here named the Lemitar Tuff. Consists of a simple to compound 

cooling unit of densely welded rhyolite ash-flow tuff that has strong 

compositional zoning, divided into a lower light-gray to pale-red rhyolitic member and an upper medium-red to yellowish-gray crystal-rich 

member. Overlies the Vicks Peak Tuff or the Sawmill Canyon Formation (new name); overlies and underlies tongues of the La Jara Peak 

Basaltic Andesite; underlies the South Canyon Tuff (new name). 

Thickness ranges from 0 to 2,000 ft. Age is Oligocene based on a 

potassium-argon age of 28.4 Ma. 

Leter Ranch Bed of the Pyramid Lake Member of the Mount 

Mazama Formation 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Measured section 1 of Morrison (1964), east of Leter 

Ranch on the south edge of Carson Sink, sec. 15, T. 21 N., R. 30 E., 

Churchill County, Nev. 
174 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Leter Ranch Bed of the Pyramid Lake Member (new name) of 

the Mount Mazama Formation, here named, is in the Carson Desert of 

the Lake Lahontan area, Nevada. Consists of a 1-cm-thick bed of white 

tephra, present as an ashy parting. Is interbedded with the lower 

member of the Sehoo Formation. Overlies the Wono Bed (new name) of 

the Pyramid Lake, underlies the Upsal Hogback Bed (new name) of the 

Carson Desert Formation (new name). Age is Pleistocene, 35 to 11.5 

Ma. 

lewiston Member of the Rochester Shale 

Middle Silurian (Wenlockian) 

New York, Ontario 

Appalachian basin 

Brett, C.E., 1983, Stratigraphy and facies relationships of the Silurian Rochester Shale 

(Wenlockian; Clinton Group) in New York State and Ontario: Rochester [New York] 

Academy of Science Proceedings, Centennial Colloquium Issue, v. 15, no. 2, 

p. 118-141. 

Type locality: Cliff exposures in the east wall of Niagara Gorge, 1 km 

south of the Lewiston-Queenston bridge and 0. 6 km north of the Robert 

Moses power plant, 2.3 km south of Lewiston, Lewiston 7.5-minute 

quadrangle, Niagara County, N.Y. 

The Lewiston Member of the Rochester Shale, here named, is the 

lower unit of the Rochester in the area from Hamilton, Ontario, Canada, 

to Brockport, N.Y. Corresponds to Grabau's (1901) lower shales and 

Ringueberg's (1888) lower and middle third subdivisions. Consists of 

gray, brownish-weathering, fossiliferous, shaly mudstone containing 

thin interbedded lenses of biomicrite and burrowed micrite. Is subdivided into five units: unit A, a basal transition zone of brachiopodcrinoid-rich biomicrite lenses in shale, 1m thick; unit B, gray mudstone 

containing bryozoan clusters, 1 to 3m thick; unit C, sparsely fossiliferous shale and calcisiltites, variable thickness; unit D, fossiliferous 

mudstone and bryozoan-rich limestone, 2 m thick; and unit E, upper 

bryozoan-rich biomicrite and a minor amount of shale, which correspond 

to the bryozoa beds of Grabau (1901), 1.5 m thick. Gradationally or 

sharply overlies the Irondequoit Limestone; sharply underlies the 

Burleigh Hill Member (new name) of the Rochester or, west of 

Grimsby, Ontario, the Stoney Creek Member of the Rochester. Thickness at the type locality is 8.6 m. Age is Middle Silurian (Wenlockian). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 175 

liberty Grove Member of the Horicon Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Road cut on north side of Waters End Road, west of the 

intersection with Highway ZZ, 4.8 km northeast of Sister Bay, 

SElf4SElf4NWlf4 sec. 35, T. 32 N., R. 28 E., Sister Bay 15-minute 

quadrangle, Door County, Wis. Named for Liberty Grove Township. 

Following the informal usage of Schneider (1981), the Liberty Grove 

Member of the Horicon Formation (new name), here named, is on the 

eastern side of the Green Bay Lobe in Door County, Wis. Consists of 

brown to yellowish-brown, coarse-grained, pebbly sandy loam till. 

Where it rests directly on bedrock, most of the clasts are Silurian 

dolomite. Lies at the surface or underlies the Kewaunee Formation 

(new name). Correlates with the Mapleview Member (new name) of the 

Horicon on the west side of the Green Bay Lobe. Thickness ranges from 

less than 3m to more than 10m. Age is Pleistocene (late Wisconsinan). 

lightning Gulch Formation of the Big Bear Group 

Precambrian 

California 

Mohave basin 

Cameron, C. S., 1982, Stratigraphy and significance of the upper Precambrian Big Bear 

Group, in Cooper, J.D., ed., Geology of selected areas in the San Bernardino 

Mountains, western Mohave desert, and southern Great Basin, California: Geological 

Society of America, Cordilleran Section, 78th Annual Meeting, guidebook, field trip 9, 

p. 5-20. 

Type section: Northwest ofWildhorse Meadows, NWl/4 sec. 4, T. 1 N., 

R. 2 E., Moonridge 7.5-minute quadrangle, San Bernardino County, 

Calif. Named for Lightning Gulch. 

Following the informal usage of Cameron (1981), the Lightning 

Gulch Formation, here named, is in the Big Bear Group (new name) in 

the southwest portion of the Sugarloaf Mountain area of the San 

Bernardino Mountains, Calif. Divided into a basal greenstone member, 

a time transgressive flow unit that locally overlies the Wildhorse 

Meadows Quartzite (new name) or lies within the lower phyllite 

member, L1, of the Lightning Gulch, where member L1 conformably 

overlies the Wildhorse Meadows; a middle quartzite member, L2, that 

gradationally overlies member L1 and underlies member L3; and an 

upper phyllite member, L3, that conformably underlies the Moonridge 
176 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Quartzite (new name) of the Big Bear Group. Thickness at the type 

section is 303 m. Age is late Precambrian. 

Limekiln Spring Member of the Kingston Peak Formation of the 

Pahrump Group 

Proterozoic 

California 

Mohave basin 

Albee, A.L., Labotka, T.C., Lanphere, M.A., and McDowell, S.D., 1981, Geologic map of 

the Telescope Peak quadrangle, California: U.S. Geological Survey Geologic Quadrangle Map GQ-1532, scale 1:62,500. 

Type section: Near Limekiln Spring in Surprise Canyon, east flank of 

the Panamint Range, T. 21 S., R. 45 E., Telescope Peak 15-minute 

quadrangle, Inyo County, Calif. 

The Limekiln Spring Member of the Kingston Peak Formation of the 

Pahrump Group, here named, is in the Telescope Peak quadrangle, Inyo 

County, Calif. Consists mainly of fine-grained metagraywacke, pelitic 

schist, and amphibolitic schist, and is divided into four map units: 

arkosic conglomerate containing clasts of older Proterozoic gneiss or of 

Beck Spring Dolomite interbedded with metamorphosed arkose and 

dolomite; thick dolomite beds; quartzite and calcareous quartzite; and 

argillite, schist, amphibolite, and metamorphosed conglomerate. The 

top of the member is marked by 60 to 100 m of thin-bedded calcareous 

quartzite and quartz arenite. Interfingers with the upper part of Beck 

Spring Dolomite; locally unconformably overlies Beck Spring Dolomite, 

Crystal Spring Formation, and older Proterozoic rocks; underlies the 

Surprise Member of the Kingston Peak Formation. Thickness ranges 

from 50 to 500 m. Age is Proterozoic. 

Lincoln Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Gravel pit, east side of Robin Road, 200 m south of its 

intersection with Highway B, 1. 7 km west of Bakerville, 

SE1/4NW1/4NW1/4 sec. 26, T. 25 N., R. 2 E., Marshfield 15-minute 

quadrangle, Wood County, Wis. Named for Lincoln County. 

Subunits: Bakerville Member, Merrill Member. 

The Lincoln Formation, here named, is in the Chippewa sublobe in 

Lincoln, Langlade, Marathon, Wood, Clark, and Taylor Counties, Wis. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 177 

Consists of reddish-brown till and associated sand and gravel. Is divided 

into the lower Bakerville Member (new name) and the upper Merrill 

Member (new name). Sharply overlies the Marathon Formation (new 

name) or Precambrian bedrock and is the surficial unit in most areas. 

Maximum thickness is 20 m. Age is Pleistocene (early Wisconsinan or 

older) based on organic matter overlying the Merrill Member. 

lindsay Formation 

Middle Ordovician 

Ontario, Pennsylvania 

Appalachian basin 

Wagner, W.R., 1966, Stratigraphy of the Cambrian to Middle Ordovician rocks of central 

and western Pennsylvania: Pennsylvania Geological Survey Bulletin G 49, 156 p. 

Type section: Exposures along Highway 35, 4 mi northwest of Lindsay, 

Ontario, Canada (Liberty, 1969). 

The Lindsay Formation of Liberty (1964) is here extended from 

Ontario in the subsurface near Lake Erie in Erie County, northwestern 

Pennsylvania, to replace the Salona Formation and the overlying 

Coburn Formation where they lose their character and consist of 

calcarenite and shale. In northwestern Pennsylvania the Salona Formation increases in thickness, becomes less argillaceous and more calcareous, and passes northward into a sequence of fossiliferous calcarenites 

and shales of the Lindsay Formation of Ontario. Overlies the Verulam 

Formation; underlies the Collingwood Formation. Age is Middle 

Ordovician. 

lindsey Mountain Rhyolite of the St. Francois Mountains 

Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: S1/2NW1/4 sec. 4, T. 33 N., R. 3 E., Ironton quadrangle, 

Iron County, Mo. Named for Lindsey Mountain. 

Rocks previously mapped as the Lindsey Mountain ash flow by 

Anderson (1962) and Unit B of the tuff of Stouts Creek by Anderson 

(1970), here named the Lindsey Mountain Rhyolite, are in the Taum 

Sauk Caldera in the western St. Francois Mountains of southeast 

Missouri. Consists of violet-gray, blackish, or light-maroon ash-flow tuff 
178 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

containing quartz and alkali feldspar phenocrysts. Overlies the Ironton 

Rhyolite (new name); underlies the Russell Mountain Rhyolite (new 

name). Thickness ranges from 500 to 700 m. Age is Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E.B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Lindsey Mountain Rhyolite. 

Little Bighorn Member of the Madison Limestone 

Early Mississippian (Kinderhookian) 

Wyoming, Montana 

Powder River basin 

Sando, W.J., 1982, New members of the Madison Limestone (Devonian and Mississippian), north-central Wyoming and southern Montana: U.S. Geological Survey Bulletin 

1529-H, p. H125-H130. 

Type section: Little Tongue River section, NEl/4 sec. 27, T. 57 N., 

R. 87 W., Sheridan County, Wyo. Named for exposures in Little 

Bighorn Canyon, NWl/4 sec. 30, T. 58 N., R. 89 W. 

The informal lower dolomite member of Sando (1972), here named 

the Little Bighorn Member, is one of six members of the Madison 

Limestone in the Powder River basin in north-central Wyoming and 

southern Montana. Is also recognized in the subsurface in the Bighorn, 

Wind River, and Powder River basins. Consists of thick-bedded, fineto medium-crystalline, fossiliferous, crinoidal dolomite and dolomitic 

limestone. Conformably overlies the Cottonwood Canyon Member of 

the Madison at most localities, or unconformably overlies the Devonian 

Jefferson Dolomite, Ordovician Bighorn Dolomite, or Ordovician and 

Cambrian Gallatin Limestone where the Cottonwood Canyon is absent; 

conformably underlies the Woodhurst Member of the Madison. Thickness is 17.5 m at the type section and ranges from 3 to 48 m. Age is 

Early Mississippian (Kinderhookian) based on brachiopods. 

Little Charley Pond Formation 

Precambrian 

New York 

Adirondack uplift 

Potter, D.B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 179 

Type locality: Exposures in the vicinity of Little Charley Pond, Tupper 

Lake 15-minute quadrangle, Hamilton County, N.Y. 

The Little Charley Pond Formation, here named, is the lowest unit 

of cover rocks in the Loon Pond syncline of the Bog River synclinorium, 

Adirondack Highlands, Hamilton, and St. Lawrence Counties, N.Y. 

The lower half consists of foliated quartzite interbedded with calcitediopside-quartz granulite, the upper half consists of diopsidic marble 

containing scattered thin quartzite beds. Unconformably overlies basement rocks of the East Charley Pond Gneiss (new name); unconformably underlies the Bear Pond Gneiss (new name). Thickness ranges 

from 0 to 40 m. Age is Precambrian. 

Little Jacks Tuff 

Miocene 

Idaho 

Snake River basin 

Ekren, E.B., Mcintyre, D.H., and Bennett, E.H., 1984, High-temperature, largevolume, lavalike ash-flow tuffs without calderas in southwestern Idaho: U.S. Geological 

Survey Professional Paper 1272, 76 p. 

Type locality: Exposures on the east wall of Little Jacks Creek canyon 

at the junction of a large tributary (Rattlesnake Creek of local usage), 

SWl/4 sec. 5, T. 9 S., R. 3 E., 35 km south of Grand View, Owyhee 

County, Idaho. 

Rocks previously informally named the rhyolite of Owyhee Plateau 

of Neill (1975) and the tuff of Antelope Ridge of Bennett (1976) are here 

named the Little Jacks Tuff. Erupted from a gentle dome in the area 

east of Juniper Mountain in the Owyhee Plateau, southwestern Idaho, 

and has been traced over an area 100 km in diameter. Tuffs were 

emplaced as ash flows at extremely high temperatures and coalesced to 

liquids before final emplacement and cooling. Contains at least four and 

possibly six cooling units of flow-banded, densely welded, brecciated, 

medium-gray to purplish-gray, vitrophyric, calc-alkalic rhyolite tuff 

containing phenocrysts of plagioclase and pigeonite. Weathers to darkreddish-brown or purple. Onlaps the Swisher Mountain Tuff (new name) 

east of Juniper Mountain. Thickness is 275 m at the type locality and 

ranges from 90 to 600 m. Age is Miocene based on potassium-argon ages 

of 10 and 9.6 Ma. 
180 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Little Tongue Member of the Madison Limestone 

Early Mississippian (Osagean) 

Wyoming, Montana 

Powder River basin 

Sando, W.J., 1982, New members of the Madison Limestone (Devonian and Mississippian), north-central Wyoming and southern Montana: U.S. Geological Survey Bulletin 

1529-H, p. H125-H130. 

Type section: Little Tongue River section, NW1/4 sec. 26, T. 56 N., 

R. 87 W., Sheridan County, Wyo. 

The informal cliffy limestone member of Sando (1972), here named 

the Little Tongue Member, is one of six members of the Madison 

Limestone in the Powder River basin in north-central Wyoming and 

southern Montana. Is also recognized in the subsurface in the Bighorn, 

Wind River, and Powder River basins. Consists of cliff-forming, 

medium- to thick-bedded, cherty, fossiliferous, crinoidal limestone, 

dolomitic limestone, or dolomite. At most localities it is marked by a 

solution breccia that represents an interval of evaporite, carbonate, and 

terrigenous rocks at the surface; anhydrite occurs at this level in the 

subsurface. Conformably overlies the Big Goose Member (new name) of 

the Madison; conformably underlies the Bull Ridge Member of the 

Madison or disconformably underlies the Amsden Formation. Thickness 

is 70 m at the type section and ranges from 24 to 87 m. Age is Early 

Mississippian (Osagean) based on corals and brachiopods. 

Lobsterville Sand 

Pliocene 

Massachusetts 

Atlantic Coast basin 

Kaye, C.A., 1983, The autochthonous and allochthonous Coastal Plain deposits of 

Martha's Vineyard and the Marshfield-Scituate area, southeastern Massachusetts: 

Atlantic Coastal Plain Geological Association Field Trip Guidebook, 34 p. 

Type locality: Outcrops in the north part of Gay Head Cliff, Martha's 

Vineyard, Mass. Named for a section of Gay Head township that adjoins 

the north end of the cliff. 

The Lobsterville Sand, here named, is part of the Gay Head moraine 

in Martha's Vineyard, Mass., and is composed of thrust plates made up 

of remnants of Coastal Plain sediments that were stacked up during 

Pleistocene glaciation. Consists of light-yellow to gray, medium- to 

coarse-grained, crossbedded, clean sand containing broken mollusk 

shells. Overlies the Devils Bridge Clay (new name). Thickness is 3.5 m. 

Age is early Pliocene based on fossils. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 181 

locke Member of the Tiger Formation 

Eocene, Oligocene, and Miocene 

Washington 

Northern Cascade Range-Okanogan province 

Gager, B.R., 1983, Stratigraphy of the Tiger Formation, northeastern Washington: 

Northwest Geology, v. 12, p. 25-41. 

Type section: Exposures in a road cut along the Locke Cut-off Road, 

SElf4NWlf4 sec. 25, T. 34 N., R. 42 E., Pend Oreille County, Wash. 

The Locke Member, here named, is in the revised Tiger Formation 

in the Cusick region, northeastern Washington. Consists of massive to 

horizontally and planar cross-stratified, coarse-grained sandstone fining 

upward to siltstone and carbonaceous shale and a minor amount of 

conglomerate. The base is not exposed but it presumably overlies 

Precambrian and Paleozoic strata; is a facies equivalent of, intertongues 

with, and is separated by a vertical arbitrary boundary from the 

Gibraltar Rock Member (new name) of the Tiger; conformably underlies 

the Jared Member (new name) of the Tiger east of the Cusick Creek 

fault; unconformably underlies the Jared west of the fault. Thickness is 

34m at the type section; inferred total thickness is 2,000 m. Age ranges 

from early middle Eocene, based on the inclusion of late early to early 

middle Eocene volcanic rock clasts, through middle Miocene, based on 

middle Miocene regional faults that bound the Tiger Formation, 

although the age determination of middle Miocene is less definite. 

Lombard Limestone of the Snowcrest Range Group 

late Mississippian (Meramecian, Chesterian) 

Montana 

Montana folded belt province 

Wardlaw, B.R., and Pecora, W.C., 1985, New Mississippian-Pennsylvanian stratigraphic 

units in southwest Montana and adjacent Idaho, in Sando, W.J., ed., Mississippian and 

Pennsylvanian stratigraphy in southwest Montana and adjacent Idaho: U.S. Geological 

Survey Bulletin 1656-B, p. B1-B9. 

Type section: Exposures 1 km north of Lombard Station, Sl/2 sec. 7, 

T. 4 N., R. 3 E., Toston 7.5-minute quadrangle, Broadwater County, 

Mont. 

The Lombard Limestone, here named, is the middle formation of the 

Snowcrest Range Group (new name). Crops out throughout most of 

southwest Montana in the Tendoy Mountains, Pioneer Mountains, 

Blacktail Mountains, Snowcrest Range, Ruby Range, Tobacco Root 

Range, northwestern part of the Gravelly Range, Elkhorn Mountains, 

Horseshoe Hills, and Bridger Range. Consists of a geographically 

restricted lower unit of poorly fossiliferous, thin to thick, indistinctly 

bedded lime-mudstone and packstone and an upper unit of fossiliferous, 
182 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

thin- to thick-bedded, skeletal lime-mudstone, wackestone, and packstone containing thin interbeds and partings of silty limestone, siltstone, and shale. Overlies the Kibbey Sandstone and underlies the 

Conover Ranch Formation (new name), both of the Snowcrest Range 

Group. Is equivalent to the Otter and Heath Formations of the Big 

Snowy Group and to part of the Tyler Formation of the Amsden Group 

in central Montana, to the South Creek and Surrett Canyon Formations 

in east-central Idaho, and to the Railroad Canyon Formation (new 

name) in the Beaverhead Range, Idaho and Montana. Thickness is 49.7 

m at the type section and attains 130 m. Age is Late Mississippian (late 

Meramecian to late Chesterian) (Mamet Foraminifer Zone 15 and Sando 

and Bamber Coral Zone IV to Mamet Foraminifer Zone 19). 

lonesome Pine Formation 

Middle Ordovician 

Tennessee 

Appalachian basin 

Brent, W.B., 1982, Mississippian stratigraphy of Greendale and Newman Ridge synclines 

and Middle Ordovician nomenclature in upper east Tennessee: Tennessee Division of 

Geology Report of Investigations 41, 37 p. 

Type section: Along and in fields adjacent to State Highway 70, about 

0. 3 km north of Lonesome Pine School and about 1. 6 km southeast of 

Livesay Mill, Kyles Ford 7.5-minute quadrangle, Hancock County, 

Tenn. 

The Lonesome Pine Formation, here named, is in the area southeast 

of the Clinch port thrust fault in Hancock and Hawkins Counties, Tenn. 

Consists of pink and gray, fossiliferous limestone, including mound 

structures of reef origin, calcareous shale, and chert. Is divided into 

informal lower and upper members. Unconformably overlies the Elway 

Limestone; gradationally underlies the Luther Formation (new name). 

Thickness is 170 m at the type section. Age is Middle Ordovician. 

Long Point Bed of the Anvil Points Member, Garden Gulch 

Member, or Douglas Creek Member of the Green River 

Formation 

Eocene 

Colorado 

Piceance basin 

Johnson, R.B., 1984, New names for units in the lower part of the Green River 

Formation, Piceance Creek basin, Colorado: U.S. Geological Survey Bulletin 1529-I, 

20 p. 

Type section: South side of Long Point in NElf4SWlf4 sec. 18, T. 7 S., 

R. 97 W., Long Point quadrangle, Garfield County, Colo. Reference 

section: West end of Kimball Mountain, SElf4SElf4, sec. 7, T. 7 S., 

R. 98 W., Long Point quadrangle. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 183 

The Long Point Bed in the Green River Formation, here named, is 

in the Piceance Creek basin, Colorado. At its type section, the Long 

Point occurs at the base of the Anvil Points Member, on Kimball 

Mountain, it occurs at the base of the Garden Gulch Member, and 

elsewhere it occurs at the base of the Douglas Creek Member. Is thin or 

absent in the central part of the basin, and grades into a thick sandstone 

sequence to the east where it loses its identity. Consists of medium-gray 

ostracode- and oolite-rich, very fine to medium-grained sandstone and 

grayish-white ostracoda! and oolitic limestone. Gastropods are abundant at the reference section, and thin claystone partings are common 

throughout. Overlies the Wasatch Formation. Thickness ranges from 

about 20 em to 14.6 m. Age is Eocene. 

loon Pond Mountain Member of the lost Pond Marble 

Precambrian 

New York 

Adirondack uplift 

Potter, D.B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: None designated. Probably named for Loon Pond Mountain, Tupper Lake 15-minute quadrangle, Hamilton County, N.Y. 

The Loon Pond Mountain Member of the Lost Pond Marble (new 

name), here named, is in the Loon Pond syncline of the Bog River 

synclinorium of the Adirondack Highlands, Hamilton and St. Lawrence 

Counties, N.Y. Consists of massive pyritic quartzite. Overlies the 

Sabattis Road Member (new name) of the Lost Pond; lies at the top of 

the structure. Is cut by the Otter Pond Dioritic Gneiss (new name). 

Thickness is at least 40 m. Age is Precambrian. 

lost Creek Member of the Tiger Formation 

Eocene, Oligocene, Miocene 

Washington 

Northern Cascade Range-Okanogan province 

Gager, B.R., 1983, Stratigraphy of the Tiger Formation, northeastern Washington: 

Northwest Geology, v. 12, p. 25-41. 

Type section: East-facing bluffs near Lost Creek, Wtf2NEl/4 sec. 16, 

T. 36 N., R. 43 E., Pend Oreille County, Wash. 

The Lost Creek Member, here named, is in the revised Tiger 

Formation in the area near lone and Tiger in northeastern Washington. 

Consists of massive to horizontally stratified biotite-hornblende granitic 

conglomerate and arkosic sandstone containing all intermediate grainsize and clast-percent variations. Overlies and pinches out over the Box 
184 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Canyon Member (new name) of the Tiger; otherwise the base is not 

exposed. Thickness at the type section is 300 m and attains to more than 

2, 000 m. Age ranges from early middle Eocene, based on the inclusion 

of late early to early middle Eocene volcanic rock clasts, through middle 

Miocene, based on middle Miocene regional faults that bound the Tiger 

Formation, although the age determination of middle Miocene is less 

definite. 

lost Mountain Amphibolite Member of the Univeter 

Formation of the New Georgia Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Lost Mountain, Lost Mountain 7.5-minute quadrangle, 

Cobb County, Ga. 

The Lost Mountain Amphibolite Member of the U niveter Formation 

(new name) of the New Georgia Group (new name), here named, is in 

the Greater Atlanta region of northwest Georgia. Forms two limbs of a 

fold traceable for 80 mi in the U niveter and encloses the Rose Creek 

Schist Member (new name) of the Univeter. Consists of hornblendeplagioclase amphibolite and hornblende gneiss and local layers of 

banded iron formation. Age is Late Proterozoic and (or) early Paleozoic. 

lost Pond Marble 

Precambrian 

New York 

Adirondack uplift 

Potter, D. B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: Exposures near Lost Pond, Tupper Lake 15-minute 

quadrangle, Hamilton County, N.Y. 

Subunits: Bog River Member, Hill 2292 Member, Sabattis Road 

Member, Loon Pond Mountain Member. 

The Lost Pond Marble, here named, is the youngest cover unit in the 

Loon Pond syncline of the Bog River synclinorium in the Adirondack 

Highlands, Hamilton and St. Lawrence Counties, N.Y. Includes, in 

ascending order, the Bog River, Hill 2292, Sabattis Road, and Loon 

Pond Mountain Members (all new names). Forms two broad areas of 

outcrop characterized by low topographic relief and swamps. Consists of 

marble, granulite, and quartzite units. Overlies the Bear Pond Gneiss 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 185 

(new name). Is intruded by the Otter Pond Dioritic Gneiss (new name). 

Thickness is more than 300 m. Age is Precambrian. 

loudon Coal Member of the Mattoon Formation of the 

Mcleansboro Group 

late Pennsylvanian (Missourian) 

Illinois 

Illinois basin 

Nance, R.B., and Treworgy, C.G., 1981, Strippable coal resources of Illinois: Part 8-

Central and southeastern counties: Illinois Geological Survey Circular 515, 32 p. 

Type section: Exposure in the south cutbank of Moccasin Creek, 

NE1/4SW1/4SE1/4 sec. 23, T. 8 N., R. 3 E., Loudon Township, Fayette 

County, Ill. 

The Loudon Coal Member of the Mattoon Formation of the 

McLeansboro Group, here named, is in Fayette County, Ill. Lies 30 to 

40 ft above the Millersville Limestone Member of the Bond Formation 

and 25 to 40 ft below the Oconee Coal Member (new name) of the 

Mattoon Formation. Correlates tentatively with the Belle Rive Coal 

Member (new name) of the Mattoon in Jefferson County to the south. 

Thickness at the type section is 15 in. Age is Late Pennsylvanian 

(Missourian). 

Lovell Wash Member of the Horse Spring Formation 

Miocene 

Nevada 

Great Basin province 

Bohannon, R.G., 1984, Nonmarine sedimentary rocks of Tertiary age in the Lake Mead 

region, southeastern Nevada and northwestern Arizona: U.S. Geological Survey 

Professional Paper 1259, 72 p. 

Type section: Exposures in Lovell Wash in the Muddy Mountains, lat 

36°12'45" N., long 114°42'30" W., Hoover Dam 15-minute quadrangle, 

Clark County, Nev. 

The Lovell Wash Member, here named the uppermost of four 

members of the Horse Spring Formation, is at Lovell Wash, Nev. Is not 

widely distributed at the surface and crops out only northwest of the 

Lake Mead fault system in Nevada. Consists of white limestone and 

dolomite, gray and white claystone, gray and brown tuff, tuffaceous 

sandstone, and arenaceous tuff. Probably originated as sediments and 

ash falls deposited in a lacustrine environment. Conformably overlies 

the Bitter Ridge Limestone Member (new name) of the Horse Spring 

Formation; unconformably underlies unnamed Miocene red sandstone in 
186 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

White Basin and the Muddy Creek Formation at Black Mesa. Thickness 

at the type section is 300 m. Age is Miocene based on potassium-argon 

and fission-track dates. 

lower Bridge Member of the Williamsburg Formation of the 

Black Mingo Group 

Paleocene (Thanetian) 

South Carolina 

Atlantic Coast basin 

Van Nieuwenhuise, D.S., and Colquhoun, D.J., 1982, The Paleocene-lower Eocene Black 

Mingo Group of the east central Coastal Plain of South Carolina: South Carolina 

Geology, v. 26, no. 2, p. 47-67. 

Type section: Outcrops along the Black River near the South Carolina 

Highway 377 bridge (Lower Bridge), Williamsburg County, S.C. 

The Lower Bridge Member, here named, is the lower member of the 

Williamsburg Formation of the Black Mingo Group in the Coastal Plain 

of South Carolina. The revised Black Mingo Group includes all the 

strata from the base of the Paleocene to the top of the Y pre sian Stage 

of the Eocene and is divided into the Rhems Formation of the Danian 

Stage, the Williamsburg Formation of the Thanetian Stage, and 

unnamed Y pre sian strata. [In the Clubhouse Crossroads corehole 

Number 1, Gohn and others (1978) assigned the entire Paleocene section 

to the Black Mingo Formation, and Gohn and others (1983) named the 

Ypresian strata the Fishburne Formation (new name).] The Lower 

Bridge Member consists of fine-grained silicified mudstone, and fossiliferous, laminated, arenaceous shale. Unconformably overlies the Perkins Bluff Member (new name) of the Rhems; gradationally underlies 

the Chicora Member (new name) of the Williamsburg. Thickness at the 

type section is 12 ft. Age is Paleocene (Thanetian). 

Lower Lake Formation 

Pleistocene 

California 

Northern Coast Range province 

Rymer, M.J., 1981, Stratigraphic revision of the Cache Formation (Pliocene and Pleistocene), Lake County, California: U.S. Geological Survey Bulletin 1502--d, p. C1-C35. 

Type section: Exposures along the west side of State Highway 53 in the 

town of Lower Lake, Wtf2SW1/4SW1/4 sec. 2, T. 12 N., R. 7 W., Lower 

Lake 7.5-minute quadrangle, Lake County, Calif. 

Lacustrine deposits in the Clear Lake area, Lake County, Calif., 

previously assigned to the revised Cache Formation, are here named 

the Lower Lake Formation. Consists of a heterogeneous deposit 

of pebble conglomerate, sandstone, siltstone, calcareous siltstone, 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 187 

limestone, tuff, and diatomite. Unconformably overlies Cretaceous 

rocks of the Great Valley sequence, the Cache Formation, or dacite of 

the Clear Lake volcanic field. Underlies units of the Clear Lake volcanic 

field. Thickness at the type section is 130 m. Age is Pleistocene based on 

potassium-argon ages of the Clear Lake volcanic rocks. 

Low-Water-Bridge Layered Gneiss 

Middle Proterozoic 

North Carolina 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Outcrop along river road, 0.5 mi north of the intersection 

of North Carolina State Roads 1527 and 1510 on the southeast side of the 

low-water bridge over the Yadkin River, 0.5 mi south of Rockford, lat 

36°16' N., long 80°39' W., Copeland quadrangle, Surry County, N.C. 

The Low-Water-Bridge Layered Gneiss, here named, is in the 

Sauras massif in the Blue Ridge in North Carolina. Represents country 

rock that was intruded by rocks of Grenville age. Contains biotite-rich 

relict amphibolite facies assemblages and lacks granulite facies. Age is 

Middle Proterozoic. 

Luis Lopez Formation 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type area: South end of Luis Lopez manganese district, 11 mi southwest of Socorro and 7 mi southwest of the village of Luis Lopez, east 

side of the Chupadera Mountains from 2.5 mi north of Nogal Canyon to 

3.3 mi south of Nogal Canyon, sees. 20, 29, 31, and 32, T. 4 S., R. 1 W., 

and sees. 4, 5, 6, 8, and 9, T. 5 S., R. 1 W., Luis Lopez 7.5-minute 

quadrangle, Socorro County, N. Mex. 

The Luis Lopez Formation, here named, is in the Socorro Peak, 

Chupadera, and Magdalena Mountains, N. Mex., and is the heterolithic 

cauldron-fill unit of the Socorro cauldron. Includes the informal rhyolites of Bianchi Ranch and Hardy Ridge. Consists of rhyolite domes and 

flows, local ash-flow tuffs, volcaniclastic rocks, breccias, andesite flows, 

and intrusives. Overlies the Hells Mesa Tuff; underlies the La J en cia 

Tuff (new name). Thickness ranges from 0 to 3,500 ft. Age is Oligocene. 
188 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

luther Formation 

Middle Ordovician 

Tennessee 

Appalachian basin 

Brent, W.B., 1982, Mississippian stratigraphy of Greendale and Newman Ridge synclines 

and Middle Ordovician nomenclature in upper east Tennessee: Tennessee Division of 

Geology Report of Investigations 41, 37 p. 

Type section: Roadcut on east side of State Highway 31, 600 m 

northwest of War Creek Church at Luther, Lee Valley quadrangle, 

Hancock County, Tenn. 

The Luther Formation, here named, is in the area southeast of the 

Clinchport thrust fault in Hancock and Hawkins Counties, Tenn. 

Consists of beds of fine-grained red and yellow limestone, argillaceous 

limestone, and shale. Gradationally overlies the Lonesome Pine Formation (new name); gradationally underlies the Witten Limestone. Correlates partly with the Bowen Formation. Thickness is 35 m at the type 

section. Age is Middle Ordovician. 

lynn Mountain Formation 

Early and Middle Pennsylvanian (Morrowan and Desmoinesian) 

Oklahoma 

Ouachita tectonic belt province 

Pitt, W.D., Fay, R.O., Wilson, L.R., and Curiale, J.A., 1982, Geology of Pushmataha 

County, Oklahoma: Eastern New Mexico University Studies in Natural Sciences 

Special Publication 2, 101 p. 

Type section: Outcrops along U.S. Highway 271 from a point 0.1 mi 

south of the main entrance to Clayton Lake State Park southward to the 

contact with the Johns Valley Shale, NWV4SWV4 sec. 35, T. 1 N., 

R. 19 E., Pushmataha County, Okla. Named for Lynn Mountain, 

Pushmataha County. 

The Lynn Mountain Formation, here named, is in the Ouachita 

Mountains in Pushmataha County, southeastern Oklahoma. Consists of 

alternating beds of greenish-gray, brown-weathering, fine-grained 

sandstone and dark-gray to black shale; clayey where more than 1 ft 

thick, and micaceous and silty where less than 1 ft thick. Conformably 

overlies the Johns Valley Shale; unconformably underlies the Lower 

Cretaceous Antlers Formation. Thickness at the type section is 1,844 ft; 

the top is eroded. Age is Early and Middle Pennsylvanian (Morrowan 

and Desmoinesian) based on palynomorphs. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 189 

Maddox Branch Member of the Slade Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R., 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37p. 

Type section: Roadcut along westbound lanes of Interstate Highway 

I --64, 15.7 km west of its intersection with Kentucky Highway 2, Soldier 

quadrangle, Rowan County, Ky. Named for Maddox Branch northeast 

of the type section. 

Strata here named the Maddox Branch Member of the Slade 

Formation (new name) were previously assigned to the Newman 

Limestone, Hardinsburg Sandstone, and other stratigraphic units that 

are now restricted from the Cumberland Escarpment area of eastcentral and northeastern Kentucky. Consists of green calcareous shale 

containing calcilutite lenses. Conformably overlies the Ramey Creek 

Member (new name) of the Slade; conformably or disconformably 

underlies the Poppin Rock Member (new name) of the Slade. Thickness 

ranges from 0 to 14m. Age is Late Mississippian. 

Magdalena Peak Rhyolite of the Santa Fe Group 

Miocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type area: On and south of Magdalena Peak, 1.25 to 5 mi south of the 

village of Magdalena on Magdalena Peak and along Hop and Agua Frio 

Canyons, sec. 34, T. 2 S., R. 4 W., and sees. 2, 3, 10, 11, 14, and 15, 

T. 3 S., R. 4 W., Magdalena SW 7.5-minute quadrangle, Socorro 

County, N. Mex. 

The Magdalena Peak Rhyolite of the Santa Fe Group, here named, 

is on the west flank of the Magdalena Range in New Mexico. Consists of 

pink, buff, or gray, flow-banded, rhyolite domes and flows. Overlies 

fanglomerates of the Popotosa Formation; the top is eroded. Thickness 

ranges from 0 to 600 ft. Age is Miocene based on a potassium-argon age 

of 14.8 Ma. 
190 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Maple Falls Member of the Chuckanut Formation 

Eocene 

Washington 

Bellingham basin 

Johnson, S.Y., 1984, Stratigraphy, age, and paleogeography of the Eocene Chuckanut 

Formation, northwest Washington: Canadian Journal of Earth Sciences, v. 21, no. 1, 

p. 92-106. 

Type section: Exposures in the bed of Coal Creek, Sl/2 sec. 4, T. 39 N., 

R. 5 E., Whatcom County, Wash. Named for the town of Maple Falls. 

The Maple Falls Member of the Chuckanut Formation, here named, 

is in the Sumas Mountain and North Fork Nooksack River valley area 

of the central part of the largest outcrop belt of the Chuckanut, which 

extends from the San Juan Islands into the foothills of the North 

Cascades, Wash. Consists of alternating conglomerate-rich coarsegrained sandstone strata and fine-grained siltstone and mudstone beds, 

interpreted as interfingering alluvial fan and flood-plain deposits. 

Overlies and possibly interfingers with the Padden Member (new name) 

and Slide Member (new name) of the Chuckanut; is bounded on the 

north and west by faults. Thickness at the type section is more than 800 

m. Age is late middle to late(?) Eocene based on stratigraphic correlation with the Padden Member. 

Mapleview Member of the Horicon Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Roadcut on the south side of Mapleview Road, west of its 

intersection with Maple Road, SElf4SWlf4SWl/4 sec. 34, T. 31 N., 

R. 10 E., Mattoon 7.5-minute quadrangle, Langlade County, Wis. 

Named for Mapleview Road, a town road running east from Highways 

45, 47, and 52, south of Antigo. 

Following the informal usage of McCartney and Mickelson (1982), 

the Mapleview Member of the Horicon Formation (new name) is here 

named. Lies on the west side of the Green Bay Lobe in Langlade and 

Marathon Counties, Wis. Consists of brown to reddish-brown, cobbly, 

pebbly, silty sand till. Overlies sand and gravel; interfingers with or 

sharply underlies the Nashville Member (new name) of the Copper Falls 

Formation (new name) or lies at the surface. Correlates with the 

Liberty Grove Member (new name) of the Horicon on the east side of 

the Green Bay Lobe. Thickness is unknown. Age is Pleistocene (late 

Wisconsinan). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 191 

Marathon Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Gravel pit on west side of Ryan Street, 2.4 km south of 

Highway 29, SW1/4SWlf4NElf4 sec 27, T. 28 N., R. 8 E., Wausau 

15-minute quadrangle, Marathon County, Wis. Named for Marathon 

County. 

Subunits: Wausau Member, Edgar Member. 

The Marathon Formation, here named, is in the Chippewa Sublobe 

in Marathon, Wood, and Clark Counties, Wis., where it is typified by a 

water-eroded landscape having thin light-gray, yellow, or brown till, 

sand, and gravel deposits. Is divided into the lower Wausau Member 

(new name), consisting of brown loam till, and the upper Edgar Member 

(new name), consisting of siltier brown loam till. Unconformably 

overlies Precambrian bedrock and is the surficial unit in most of 

Marathon County but sharply underlies the Lincoln and Copper Falls 

Formations (new names) to the north and west and the Horicon 

Formation (new name) to the east. Thickness ranges from 0 to 20m. 

Age is Pleistocene, probably early Wisconsinan or older. 

Marble Bluff Bed 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Marble Bluff, in the banks of Mud Lake (Winnemucca) 

Slough, 5.6 km north of Nixon, NWlf4NWlf4 sec. 12, T. 23 N., R. 23 E., 

Nixon 15-minute quadrangle, Washoe County, Nev. 

The Marble Bluff Bed, here named, is attributed to Mount St. 

Helens in southwestern Washington because it contains cummingtonite, 

which is characteristic of Mount St. Helens tephra. Occurs in the Carson 

Desert and around Pyramid Lake in the Lake Lahontan area, Nevada. 

Is a graded bed, gray at the base and white at the top, 1 em thick, and 

is the lowest tephra layer contained within the lower member of the 

Sehoo Formation. Underlies the Carson Sink Bed (new name) of the 

Mono Basin Formation (new name) and the Pelican Island Bed (new 

name) and Wono Bed (new name) of the Pyramid Lake Member (new 

name) of the Mount Mazama Formation. Age is Pleistocene, 35 to 

11.5 ka. 
192 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Marple Canyon Sandstone Member of the Ridge Route 

Formation of the Ridge Basin Group 

Miocene (Mohnian) 

California 

los Angeles basin 

Link, M. H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J. C., and Link, M. H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5-12. 

Type section: Exposures on the north side of Marple Canyon where the 

Old Ridge Route crosses the outcrop at the head of the canyon, between 

1.0 km south and 0.5 km north of the intersection of Old Ridge Route 

and Templin Highway, about 8. 0 km north of Castaic, Los Angeles 

County, Calif. 

The Marple Canyon Sandstone Member, here named, is in the Ridge 

Route Formation of the Ridge Basin Group in the central Ridge basin, 

Los Angeles County, Calif. Is the oldest of five major clastic tongues in 

the Ridge Route. Consists of brown and white arkosic sandstone 

interbedded with mudstone and conglomerate and contains freshwater 

mollusk, ostracode, charophyte, and vertebrate fossils. Lateral extent 

is 8, 000 m; interfingers with the Violin Breccia to the southwest and the 

Ridge Route Formation undivided to the northeast. Conformably 

overlies and interfingers with the Castaic Formation; conformably 

underlies the Paradise Ranch Shale Member (new name) of the Peace 

Valley Formation, redefined. Thickness is 420 m at the type section and 

ranges from 80 to 1,100 m. Age is late Miocene (late Mohnian) based on 

its stratigraphic position above the Castaic Formation. 

Marshfield Center Formation 

Miocene 

Massachusetts 

New England province 

Kaye, C.A., 1983, The autochthonous and allochthonous Coastal Plain deposits of 

Martha's Vineyard and the Marshfield-Scituate area, southeastern Massachusetts: 

Atlantic Coastal Plain Geological Association Field Trip Guidebook, 34 p. 

Type locality: Abandoned sand pits on the east side of Marshfield 

Center, Duxbury 7.5-minute quadrangle, Plymouth County, Mass. 

Glacially dislocated, allochthonous masses in the Marshfield Hills 

moraine and at Third Cliff, Scituate, Mass., are here named the 

Marshfield Center Formation. Consists of gray, compact, micaceous, 

slightly glauconitic, horizontally bedded silt and clay. Overlies older 

granite; is thrust into Pleistocene moraine. Thickness attains 14m. Age 

is Miocene, probably no younger than middle Miocene, based on pollen 

and spores. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 193 

Mars Hill Ti II 

Pleistocene (Wisconsinan) 

Maine 

New England province 

Genes, A.N., Newman, W.A., and Brewer, T.B., 1981, Late Wisconsinan glaciation 

models of northern Maine and adjacent Canada: Quaternary Research, v. 16, no. 1, 

p. 48-65. 

Type locality: Mars Hill, southern Aroostook County, Maine. 

The Mars Hill Till, here named, blankets the surface of southern 

Aroostook County, Maine, as an irregular hummocky sheet consisting of 

outwash, kames, kettles, and smaller till hummocks and an extensive 

moraine complex, characterized by distinct ridges, that rises above the 

general level of the drift surface. Clasts in the drift include DeBoullie 

Granodiorite, Chapman Sandstone, Mapleton Sandstone, and Mars Hill 

Conglomerate. Was deposited by the Laurentide ice sheet or by a 

separate ice cap in Maine. Correlates with the Van Buren Till (new 

name), also deposited by the Laurentide ice sheet, and the Lennoxville 

till of southeastern Quebec. Is the youngest till in Aroostook County and 

lies at the surface. Thickness ranges from 0 to 30 m. Age is Pleistocene 

(late Wisconsinan). [The geographic name Mars Hill has been preempted by the Mars Hill Conglomerate of Gregory (1900), named for the 

same geographic feature. The use of a preempted name violates the 

Code of Stratigraphic Nomenclature (American Commission on Stratigraphic Nomenclature, 1970), in effect at the time this name was 

introduced, as well as the North American Stratigraphic Code (North 

American Commission on Stratigraphic Nomenclature, 1983).] 

Mauls Point Member of the Flanner Beach Formation 

Pleistocene 

North Carolina 

Atlantic Coast basin 

Miller, William, III, 1985, The Flanner Beach Formation (middle Pleistocene) in eastern 

North Carolina: Tulane Studies in Geology and Paleontology, v. 18, no. 3, p. 93-122. 

Type section: Bluffs on the south shore of the Pamlico River, 1.2 km 

southwest of Mauls Point on the southeastern shore of Blounts Bay, 

Blounts Bay 7.5-minute quadrangle, Beaufort County, N.C. 

The upper member of the Flanner Beach Formation in the Pamlico 

River valley in the Blounts Bay area of Beaufort County, N.C., is here 

named the Mauls Point Member. Consists of a blanket-shaped unit of 

interbedded sand and mud containing clay interlaminations, and may 

represent open lagoonal deposits. Intertongues with and overlies the 

Hills Point Member (new name) of the Flanner Beach. Thickness at the 

type section is 4 m. Age is middle Pleistocene. 
194 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Mauzy Formation 

Early Permian 

Kentucky 

Illinois basin 

Kehn, T.M., Beard, J.G., and Williamson, A.D. 1982, Mauzy Formation, a new stratigraphic unit of Permian age in western Kentucky: U.S. Geological Survey Bulletin 

1529-H, p. H73-H86. 

Type section: Composite of measured section 340 ft thick from core hole 

Gil-30 of the Kentucky Geological Survey, 7.5 mi northeast of Sturgis, 

and 50 ft of younger strata in a nearby ridge 1 mi west of Cap Mauzy 

Lake, Bordley quadrangle, Union County, Ky. 

Strata of Early Permian age preserved in a fault block near Sturgis 

in western Kentucky, formerly assigned to the uppermost part of the 

Pennsylvanian Sturgis Formation, are here named the Mauzy Formation. Consists of interbedded gray to black and green to greenish-gray 

shale and siltstone and lesser amounts of limestone and sandstone. 

Three thin coal or carbonaceous shale beds are in the lower part of the 

cored section. Conformably overlies the Sturgis Formation and may 

intergrade with it; the upper limit is not defined because it has been 

removed by erosion. Thickness at the type section is 390 ft; total 

thickness may be as much as 1,300 ft. The boundary between the 

Pennsylvanian and Permian Systems cannot be defined precisely but is 

placed at the proposed contact between the Sturgis and the Mauzy. 

Fusulinids of Early Permian age are found in the Mauzy 140 ft above the 

boundary. 

Mazama Member of the Mount Mazama Formation 

Holocene 

Nevada, California 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Measured section 22a of Morrison (1964), Stillwater 

Reservoir diversion canal, Humboldt County, Nev. 

Subunits: Tsoyawata Bed, Mazama Bed. 

The Mazama Member of the Mount Mazama Formation, here 

named, is in the Lake Lahontan area of Nevada and California. 

Comprises at least three tephra beds, two of which are named the 

Tsoyawata Bed (new name) and Mazama Bed, formed during the 

eruptions that led to the collapse of Mount Mazama at about 7 ka. Age 

is Holocene. [The unit here named the Mazama Bed is described in the 

literature as the informal Mazama ash, widely distributed throughout 

the western United States and Canada. The use of the same geographic 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 195 

name, Mazama, for a unit and one of its parts violates the North 

American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 1983).] 

McKay Formation of the Dalles Group 

Miocene and Pliocene 

Oregon 

Eastern Columbia basin 

Farooqui, S.M., Beaulieu, J.D., Bunker, R.C., Stensland, D.E., and Thoms, R.E., 1981, 

Dalles Group: Neogene formations overlying the Columbia River Basalt Group in 

north-central Oregon: Oregon Geology, v. 43, no. 10, p. 131-140. 

Reference sections: McKay Reservoir section, El/2 sec. 33, T. 2 N., 

R. 32 E.; Mission section, North-facing roadcut, NWl/4NElf4NEl/4 sec. 

12, T. 2 N., R. 32 E., Umatilla County, Oreg. 

Fanglomerates in the vicinity of the McKay reservoir in the Agency 

basin, informally named the McKay beds by Hogenson (1964), are here 

named the McKay Formation of the Dalles Group. Consists of fanglomerate or valley fill deposits of partially carbonate-cemented basalt 

gravel and interbedded tuffaceous sand and silt. Conformably overlies 

the Frenchman Springs Member of the Wanapum Basalt and the 

Grande Ronde Basalt; underlies Quaternary loess. Thickness ranges 

from 2 to 72 m. Age is late Miocene and early Pliocene based on 

vertebrate fossils. 

McKenzie Canyon Limestone of the Tendoy Group 

late Mississippian (Meramecian) 

Montana 

Montana folded belt province 

Sando, W.J., Sandberg, C.A., and Perry, W.J., Jr., 1985, Revision of Mississippian 

stratigraphy, northern Tendoy Mountains, southwest Montana, in Sando, W.J., ed., 

Mississippian and Pennsylvanian stratigraphy in southwest Montana and adjacent 

Idaho: U.S. Geological Survey Bulletin 165~A, p. A1-A10. 

Type section: North side of Bell Canyon, sec. 17, T. 11 S., R. 10 W., 

Tendoy Mountains, Kidd 7.5-minute quadrangle, Beaverhead County, 

Mont. Named for exposures in McKenzie Canyon. 

The McKenzie Canyon Limestone, here named, is the uppermost 

formation of the Tendoy Group (new name) in the Tendoy Mountains, 

Mont. Consists of gray, thin- to medium-bedded, sparsely cherty 

micrite, dismicrite, and pelmicrite and minor amounts of crinoidal 

wackestone, encrinite, pelsparite, evaporite-solution breccia, and silty 

dolomitic limestone. Represents a facies belt deposited near the shoreline of a karst plain developed on the craton. Conformably overlies the 

Mission Canyon Limestone of the Tendoy Group; conformably underlies 
196 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

the Kibbey Sandstone of the Snowcrest Range Group (new name). 

Thickness is 140m at the type section. Age is Late Mississippian (early 

Meramecian) based on corals and conodonts. 

McKown Formation of the Austin Group 

late Cretaceous 

Texas 

Ouachita tectonic belt province 

Garner, L.E., and Young, K.P., 1976, Environmental geology of the Austin area-An aid 

to urban planning: Texas Bureau of Economic Geology Report of Investigations 86, 

39 p. 

Type locality: Named for the old McKown quarry site exposed along 

Onion Creek, upstream from U.S. Highway 183, near Pilot Knob, 

Travis County, Tex. 

The McKown Formation of the Austin Group, here named, occurs 

only in the vicinity of Pilot Knob, Tex. Consists of coarse-grained, 

shell-fragment limestone and is a beach rock facies equivalent of the 

Pflugerville (new name), Burditt, and possibly the upper 40 ft of the 

Dessau Formations of the Austin. Grades laterally into pyroclastic tuff 

that surrounds the central intrusion of Pilot Knob. Underlies the 

Sprinkle Formation of the Taylor Group. Thickness ranges from 0 to 45 

ft. Age is Late Cretaceous. 

McMichael Member of the Buttermilk Falls Limestone 

Middle Devonian 

Pennsylvania 

Appalachian basin 

Epstein, J.E., 1984, Onesquethawan stratigraphy (Lower and Middle Devonian) of 

northeastern Pennsylvania: U.S. Geological Survey Professional Paper 1337, 35 p. 

Type section: Railroad cut of Erie-Lackawanna Railroad, nearly 1 mi 

south of East Stroudsburg Post Office, Stroudsburg 7.5-minute quadrangle, Monroe County, Pa. Named for McMichael Creek north of 

Godfrey Ridge. 

The middle of three mappable members of the Buttermilk Falls 

Limestone on Godfrey Ridge, Monroe County, Pa., is here named the 

McMichael Member. Consists of evenly bedded to lenticular, calcareous, 

partly silty, medium-gray fossiliferous shale interbedded with fossiliferous biomicrite and biomicrudite. Forms a topographic swale between 

cherty limestones below and above. Gradationally overlies the Foxtown 

Member (new name) and gradationally underlies the Stroudsburg 

Member (new name), both of the Buttermilk Falls. Thickness is 41ft. 

Age is Middle Devonian. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 197 

Medicine lodge Creek Member of the Tensleep Formation 

Middle Pennsylvanian (Desmoinesian) 

Wyoming 

Big Horn basin 

Moore, D.A., 1984, The Tensleep Formation of the southeastern Big Horn basin, 

Wyoming, in Goolsby, Jim, and Morton, Doug, eds., The Permian and Pennsylvanian 

geology of Wyoming: Wyoming Geological Association 35th Annual Field Conference 

Guidebook, p. 273-279. 

Type locality: Exposures in the canyon of Medicine Lodge Creek, 

center T. 50 N., R. 89 W., Big Horn County, Wyo. 

The lower, marine unit of the Tensleep Formation in the Big Horn 

and Wind River basins, Wyoming, is here named the Medicine Lodge 

Creek Member. Consists of white to tan and pink, subangular to 

subrounded, fine-grained, quartzose sandstone, extensively cemented 

by calcite and dolomite, and numerous gray-green to white, fossiliferous 

limestone and dolomite beds intercalated with marine shale beds. 

Underlies the Hyatt Ranch Member (new name) of the Tensleep with 

angular unconformity. Correlates with the middle member of the 

Minnelusa Formation. Thickness ranges from 150 to 200 ft. Age is 

Middle Pennsylvanian (Desmoinesian) based on marine megafossils and 

fusulinids. 

Merrick Formation 

Pleistocene (Wisconsinan) 

New York 

Atlantic Coast basin 

Rampino, M.R., and Sanders, J.E., 1981, Upper Quaternary stratigraphy of southern 

Long Island, New York: Northeastern Geology, v. 3, no. 2, p. 116-128. 

Type section: Borehole 201, Wantagh Pollution Control Plant, 0.25 mi 

east of Wantagh State Parkway and 1.2 mi south of Merrick Road, 

Wantagh, Long Island, Nassau County, N.Y. 

Glacial outwash deposits in the subsurface of south-central Long 

Island are here named the Merrick Formation. Consists of light-brown 

to brown, firm to very dense, fine to coarse sand and gravel. Unconformably overlies Upper Cretaceous sediments; unconformably underlies the Wantagh Formation (new name). Correlates with the Montauk 

Drift of northern Long Island. Thickness at the type section is 14.5 ft. 

Age is late Pleistocene (early Wisconsinan). 
198 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Merrill Member of the Lincoln Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Northwest corner of the gravel pit north of Duginski 

Road, about 500 m west of the intersection of Duginski Road and old 

Highway 51, north of the town of Merrill, SEV4SEV4NWV4 sec. 1, 

T. 31 N., R. 6 E., Merrill15-minute quadrangle, Lincoln County, Wis. 

The upper member of the Lincoln Formation (new name) in the 

Chippewa Sublobe in central Wisconsin is here named the Merrill 

Member, following the informal usage of LaBerge and Myers (1971). 

Consists of dark-reddish-brown cobbly, pebbly, sandy loam till that 

resembles the adjacent Bakerville Member (new name) of the Lincoln in 

color and texture. Sharply overlies the Wausau Member (new name) of 

the Marathon Formation (new name); is the surface till unit in Langlade, 

Lincoln, and eastern Marathon Counties. No exposures of the contact 

with the overlying Nashville Member (new name) of the Copper Falls 

Formation (new name) are known. Thickness is less than 10m. Age is 

Pleistocene (early Wisconsinan or older) based on overlying organic 

material. 

Merritt Dam Member of the Ash Hollow Formation of the 

Ogallala Group 

Miocene 

Nebraska 

Chadron arch 

Skinner, M.F., and Johnson, F.W., 1984, Tertiary stratigraphy and the Frick Collection 

of fossil vertebrates from north-central Nebraska: American Museum of Natural 

History Bulletin, v. 178, art. 3, p. 215-368. 

Type section: Outcrop above the Burge quarry on the east side of Snake 

River canyon, NWV4NEV4NEV4SEV4 sec. 15, T. 32 N., R. 30 W., Cherry 

County, Nebr. Named for Merritt Reservoir Dam, 9 mi southsouthwest of the type section. 

The Merritt Dam Member of the Ash Hollow Formation of the 

Ogallala Group, here named, is in north-central Nebraska. Consists of 

thin-bedded sandstone containing calcareous or marly zones and layers 

of vitric tuff and ash beds. Contains vertebrate fossil beds. Overlies the 

Cap Rock Member of the Ash Hollow; underlies Quaternary Sand Hills 

terrain. Thickness at the type section is 65 ft. Ash beds in the member 

are dated at 10 and 9.5 Ma. Age is Miocene. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 199 

Mexican Dam Bed 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Exposure in a high terrace of the Carson River about 6.5 

km east-southeast of Carson City at Mexican Dam, center NWl/4SEl/4 

sec. 35, T. 15 N., R. 20 E., Dayton 15-minute quadrangle, Lyon County, 

Nev. 

The Mexican Dam Bed, here named, occurs at two localities near 

Carson City, Nev., above the highest shoreline of Lake Lahontan. 

Consists of white, rhyolitic tephra containing elongated glass shards. 

Overlies the Dibekulewe Bed (new name). Age is Pleistocene. 

Michaud Formation 

Holocene 

Louisiana 

Gulf Coast basin 

Miller, William, III, 1983, Stratigraphy of newly exposed Quaternary sediments, eastern 

Orleans Parish, Louisiana: Tulane Studies in Geology and Paleontology, v. 17, no. 3, 

p. 85-103. 

Type section: East wall of Lake Carmel borrow pit, 0.5 km northeast of 

the junction of Bullard Avenue and Interstate Highway I-10, and 

northwest of the village of Michoud, on the outskirts of New Orleans, 

Orleans Parish, La. 

Bay-sound deposits formed on a deltaic facies of the Deweyville 

terrace in Orleans Parish, La., are here named the Michoud Formation. 

Consists of fine-grained, slightly shelly, greenish-gray silt and clay 

containing sand lenses. Unconformably overlies buried Pleistocene soil; 

grades upward into a barrier bar sand unit. Thickness is 3.8 m at the 

type section. Peat at the base of the unit has a radiocarbon age of7.3 ka. 

Age is Holocene. 

Middle Granville Slate 

Early Cambrian 

New York 

New England province 

Fisher, D.W., 1984, Bedrock geology of the Glens Falls-Whitehall region, New York: 

New York State Museum Map and Chart Series no. 35, 60 p. 
200 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Quarries and adjacent outcrops 300 to 1,500 m northnorthwest of the bridge over the Mettawee River at Middle Granville, 

Granville 7.5-minute quadrangle, Washington County, N.Y. Four reference sections are designated. 

Extensively quarried green, purple, maroon, and gray slates in 

Washington County, N.Y., previously mapped as the Mettawee Slate 

and as part of the West Castleton Formation, are here named the 

Middle Granville Slate. Contains local interbeds of micrite, in places 

reduced to layers of nodules; weathers to a distinctive tan color. 

Overlies the Browns Pond Formation (new name); the contact is placed 

where gray slate changes upward to green slate; underlies the Hatch 

Hill Formation; the contact is placed where slates change upward to 

sooty, fissile black slates. Thickness at the type section is 95 m. Age is 

Early Cambrian based on fossils. 

Middle Inlet Member of the Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Road cut on north side of Caylor Road, 1.5 km north of 

Highway JJ, NE1/4NW1/4SE1/4 sec. 8, T. 33 N., R. 23 E., Stephenson 

15-minute quadrangle, Marinette County, Wis. Named for the Township of Middle Inlet. 

The upper member of the Kewaunee Formation (new name) on the 

west side of the Green Bay Lobe in Wisconsin is here named the Middle 

Inlet Member, following the informal usage of McCartney (1979). 

Consists of reddish-brown sand-silt-clay till. Unconformably overlies 

the Kirby Lake Member (new name) of the Kewaunee; lies at the 

surface in much of Marinette County. Contact with the equivalent 

Glenmore Member (new name) of the Kewaunee on the east side of the 

Green Bay Lobe is arbitrarily placed at the vertical contact at the Fox 

River. Thickness is 4.5 mat the type section. Age is Pleistocene (late 

Wisconsinan). 

Milky River Formation 

Pliocene 

Alaska 

Bristol Bay basin 

Dettennan, R.L., Miller, T.P., Yount, M.E., and Wilson, F.H., 1981, Geologic map of the 

Chignik and Sutwik Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous 

Investigations Map 1-1229, scale 1:250,000. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 201 

Type locality: Northeast spur of an unnamed mountain, 12 km east of 

Bear Lake, sees. 14, 15, and 22, T. 48 S., R. 69 W., Chignik quadrangle, 

Alaska. Named for Milky River which lies west of the mountain. 

Volcanogenic nonmarine sedimentary rock interlayered with flows 

and sills, the informal Milky River Formation of Galloway (1974), are 

here defined and formally named the Milky River Formation. Lower 

part consists of 1,000 m of dark-brown to gray, poorly indurated, 

coarse, crossbedded and channeled, volcanic sandstone and cobbleboulder conglomerate. Upper part contains porphyritic andesite flows, 

lahars, and tuff beds interlayered with sedimentary rock; volcanic 

layers are thicker and more numerous upward. Unconformably overlies 

Bear Lake Formation; unconformably underlies volcanic flows and 

surficial deposits of Pleistocene and Holocene age. Thickness at the type 

locality is 1,525 m. One flow unit near top has a radiometric age of 3 Ma; 

age is Pliocene. 

Miller Creek Formation 

Pleistocene (Wisconsinan) and Holocene 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Exposures in bluff, 1. 5 km west of the mouth of Hanson 

Creek, SEl/4SWl/4SWl/4 sec. 27, T. 49 N., R. 12 W., Poplar NE 

7.5-minute quadrangle, Douglas County, Wis. Named for Miller Creek, 

a tributary of the Amnicon River. 

Subunits: Hanson Creek Member, Douglas Member. 

The Miller Creek Formation, here named, is in the Superior Lobe in 

Wisconsin. Includes the older Hanson Creek Member (new name) along 

the Lake Superior shoreline and the Douglas Member (new name) west 

of the Bayfield Peninsula. Consists of till, reddish clay sediments that 

have been called Red Clay, and offshore silt and clay beds. Sharply 

overlies the Copper Falls Formation (new name); lies at the surface in 

the Superior lowland. Thickness ranges from 10 to 90 m. Age is late 

Pleistocene (latest Wisconsinan) and Holocene. 

Mill Knob Member of the Slade Formation 

late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R., 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 
202 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Natural Bridge Stone Company quarry, 4 km southeast of 

Mill Knob and 3 km south of Bowen, Stanton 7.5-minute quadrangle, 

Powell County, Ky. 

Strata previously assigned to the Newman Limestone and other 

units that are now restricted from the Cumberland Escarpment outcrop 

belt in east-central and northeastern Kentucky are here named the Mill 

Knob Member of the Slade Formation (new name). Consists of calcarenite and calcilutite and lesser amounts of dolostone and shale. Intertongues with or conformably overlies the Warix Run Member (new 

name) of the Slade, or disconformably overlies the Ste. Genevieve and 

St. Louis Members; disconformably underlies the Cave Branch Bed of 

the Slade. Thickness ranges from 0 to 13 m. Age is Late Mississippian. 

Miluveach Formation of the Ugnuravik Group 

Early Cretaceous (Valanginian to Barremian) 

Alaska 

Arctic Coastal Plains province 

Carman, G.J., and Hardwick, Peter, 1983, Geology and regional setting of Kuparuk oil 

field, Alaska: American Association of Petroleum Geologists Bulletin, v. 67, no. 6, 

p. 1014-1031. 

Type section: U gnu State 1 well, depth interval 6,262-6,793 ft b.r. t., 

also the type section of the U gnuravik Group, Kuparuk field, ColvillePrudhoe basin, T. 12 N., R. 9 E., Umiat Base Line, Alaska. Named for 

the Miluveach River located west of the Kuparuk field. 

The Miluveach Formation of the Ugnuravik Group (new name), here 

named, is in the Colville-Prudhoe basin, Alaska. Consists of grayishbrown to black, brittle, micaceous, silty mudstone containing finely 

disseminated pyrite, pyritized foraminifera, and rounded quartz grains. 

Unconformably overlies the Kingak Shale; gradationally underlies the 

Kuparuk Formation (new name) of the U gnuravik Group. Correlates 

with the lower part of the Kongakut Formation to the southeast, and 

possibly with the Pebble Shale to the west. Thickness ranges from 300 

to 500 feet. Age is Early Cretaceous (Valanginian to Barremian) based 

on dinoflagellates. 

Mina Peak Member of the Sunrise Formation of the Volcano 

Peak Group 

Early Jurassic (Pliensbachian) 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598-1608. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 203 

Type locality: Exposures on Mina Peak, Gabbs Valley Range, Mineral 

County, Nev. 

The upper carbonaceous part of the uppermost unit of Muller and 

Ferguson (1939) of the Sunrise Formation is here named the Mina Peak 

Member of the now revised Sunrise Formation of the Volcano Peak 

Group (new name) in the Gabbs Valley Range in west-central Nevada. 

Consists of medium- to thick-bedded bioclastic limestone. Conformably 

overlies the argillaceous Joker Peak Member (new name) of the Sunrise, 

and the contact is drawn at the lowest limestone beds; gradationally 

underlies the Dunlap Formation. Thickness is 75 m. Age is Early 

Jurassic (Pliensbachian) based on fossils. 

Mirounga Formation 

Late Cretaceous (Turonian(?) to Maastrichtian) 

California 

Santa Maria basin 

Bartling, W.A., and Abbott, P.L., 1983, Upper Cretaceous sedimentation and tectonics 

with reference to the Eocene, San Miguel Island, and San Diego area, California, in 

Larue, D.K., and Steel, R.J., eds., Cenozoic marine sedimentation Pacific margin, 

U.S.A.: Society of Economic Paleontologists and Mineralogists, Pacific Section, May 

18, 1983, p. 133-150. 

Type section: Beach cliffs from Point Bennett northeastward to the 

west side of Otter Harbor, and from the mouth to the head of west 

Green Mountain Canyon, west end of San Miguel Island, Calif. Named 

for Mirounga augustirostris, the northern elephant seal, which breeds 

at the base of the outcrop. 

Submarine fan deposits of the middle fan-fringe facies on San Miguel 

Island, formerly assigned to the J alama Formation of the California 

mainland, are here named the Mirounga Formation. Consists of interbedded sandstone, mudstone, and channel conglomerate dominated by 

durable, brittle, black rhyodacite, which gives the rock a salt-andpepper appearance, whereas the J alama Formation is dominated 

by quartzite. Underlies Eocene submarine fan deposits. Thickness is 

7,800 ft at the type section. Age is Late Cretaceous (Turonian(?) to 

Maastrichtian) based on potassium-argon ages of the rhyodacite. 

Mobley Mountain Granite 

Late Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Herz, Norman, and Force, E.R., 1984, Rock suites in Grenvillian terrane of the Roseland 

district, Virginia. Part 1. Lithologic relations: Geological Society of America Special 

Paper 194, p. 187-200. 
204 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type locality: Mobley Mountain, Piney River 7.5-minute quadrangle, 

Amherst County, Va. 

The Mobley Mountain Granite, here named, underlies Mobley 

Mountain in the southwestern corner of the Roseland district, Amherst 

County, Va. Consists of fine- to medium-grained, massive granite that 

has a salt-and-pepper appearance resulting from biotite patches disseminated through granular quartz and feldspar. The granite body is plug 

shaped under Mobley Mountain, and irregular smaller bodies, veins, 

and migmatites extend for 2 km in each direction away from the 

mountain. Intrudes the Turkey Mountain pluton of the Roses Mill 

Plutonic Suite (new name). Is part of a belt of granites emplaced about 

650 Ma. Age is Late Proterozoic. 

Mokelumne River Formation 

late Cretaceous 

California 

Sacramento basin 

Campion, J.T., Jr., 1980, Conway Ranch gas field: California Division of Oil and Gas, 

Publication TR24, 13 p. 

Type section: Brazos Oil and Gas Company (now Union Oil Company of 

California) well, S.R. Unit 1, depth interval 4,364-5,906 ft, sec. 17, 

T. 4 N., R. 4 E., San Joaquin County, Calif. 

Rocks in the subsurface of the southern Sacramento Valley, Calif., 

formerly called the Meganos-Martinez Formation and currently known 

as the informal Mokelumne formation, (not to be confused with the 

formally named Mokelumne Formation of Taliaferro (1951), of Permian 

age, located in ElDorado County, Calif.) are here named the Mokelumne River Formation. Consists of white to gray-green, fine- to 

medium-grained, friable, quartzose sandstone and gray to brown carbonaceous shale interbedded with thin layers of lignite. Overlies the H 

& T shale; unconformably underlies the Eocene Capay Formation. Gas 

is produced from three sandstone zones in the Mokelumne River 

Formation; the middle zone is informally named the IOC sand. Thickness is 1,542 ft. Age is Late Cretaceous. 

Mono Basin Formation 

Pleistocene and Holocene 

California, Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type area: Mono Basin, California. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 205 

Subunits: Carson Sink Bed, Salt Wells Member and its Walker Lake 

Bed and Turupah Flat Bed. 

The Mono Basin Formation, here named, is in the Mono Lake and 

Lake Lahontan areas, California and Nevada. Contains the Carson Sink 

Bed (new name) and the Salt Wells Member and its Walker Lake Bed 

and Turupah Flat Bed (all new names). Consists of tephra, the source of 

which is believed to be Mono Basin in eastern California because of its 

similarity in petrography and age to known tephra from Mono Basin and 

its geographic distribution, which is limited to the area south of Carson 

Sink. Age is Pleistocene and Holocene, 35 to 0.6 ka. 

Monumental Mills Formation of the Lynchburg Group 

Late Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Wehr, Frederick, 1985, Stratigraphy of the Lynchburg Group and Swift Run Formation, 

Late Proterozoic (730-570 Ma), central Virginia: Southeastern Geology, v. 25, no. 4, 

p. 225--239. 

Type locality: Exposures near Monumental Mills, Castleton 7.5-minute 

quadrangle, Rappahannock County, Va. 

The Monumental Mills Formation of the Lynchburg Group, here 

named, is in the Culpeper area, Virginia. Includes two informal 

members: a lower sandstone member consisting of gray, fine- to 

medium-grained, well-sorted sandstone and siltstone that makes up the 

bulk of the formation and an upper siltstone member consisting of 

dark-gray to greenish, thinly laminated siltstone and mudstone. The 

outcrop belt of the Monumental Mills is 0 to 1,500 m wide and thins to 

the south. Contacts are not exposed, but it appears to gradationally 

overlie the Bunker Hill Formation of the Lynchburg; sharply underlies 

the Thorofare Mountain Formation (new name) of the Lynchburg. Age 

is Late Proterozoic based on an age ranging from 730 to 570 Ma for the 

Lynchburg Group. 

Moonridge Quartzite of the Big Bear Group 

Precambrian 

California 

Mohave basin 

Cameron, C.S., 1982, Stratigraphy and significance of the upper Precambrian Big Bear 

Group, in Cooper, J.D., Geology of selected areas in the San Bernardino Mountains, 

western Mohave desert, and southern Great Basin, California: Geological Society of 

America, Cordilleran Section, 78th Annual Meeting, guidebook, field trip 9, p. 5--20. 

Type section: 1.5 km northeast of Sugarloaf Mountain at Peak 9,433 

ft, NWl/4 sec. 5, T. 1 N., R. 2 E., Moonridge 7.5-minute quadrangle, 

San Bernardino County, Calif. 
206 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Rocks in the southwest part of the Sugarloaf Mountain area of the 

San Bernardino Mountains in California, informally called the Sugarloaf 

Quartzite by Cameron (1981), are here named the Moonridge Quartzite 

of the Big Bear Group (new name). Is divided into a lower quartzite 

member, Ml, consisting of white, massive, vitreous orthoquartzite that 

conformably overlies the Lightning Gulch Formation (new name) of the 

Big Bear Group; a lower laminated quartz phyllite member, M2; a 

middle quartzite member, M3, consisting of light-gray to tan, wellbedded quartzite; an upper phyllite member, M4, consisting of quartz 

phyllite, micaceous quartzite, and marble; and an upper quartzite 

member, M5, consisting of blue-gray to white, cliff-forming quartzite 

that conformably underlies the Green Spot Formation (new name) of 

the Big Bear Group. Contacts between the members are conformable. Thickness at the type section is more than 125 m. Age is late 

Precambrian. 

Moonshine Creek Latite 

Oligocene 

Nevada 

Great Basin province 

Hose, R.K., 1983, Geologic map of the Cockalorum Wash quadrangle, Eureka and Nye 

Counties, Nevada: U.S. Geological Survey Miscellaneous Investigations Map 1-1410, 

scale 1:31,680. 

Type section: Exposures on the east side of upper Moonshine Creek, 

sec. 16 (projected), T. 131/2 N., R. 51 E., southwest corner of Cockalorum Wash 15-minute quadrangle, Nye County, Nev. 

The Moonshine Creek Latite, here named, is in the Antelope Range, 

Nev. Consists of pale-brown to pale-red, vuggy, andesitic lava containing phenocrysts and yellow zeolite-lined vesicles in a dense partially 

devitrified groundmass. Unconformably overlies the Mulligan Canyon 

Rhyolite (new name); conformably underlies Oligocene dacite porphyry. 

Thickness is 200 m. Age is Oligocene based on stratigraphic position. 

Moreno Hill Formation 

late Cretaceous (Turonian) 

New Mexico 

San juan basin 

McLellan, Marguerite, Haschke, Laura, Robinson, Laura, Carter, M.D., and Medlin, 

Antoinette, 1983, Middle Turonian and younger Cretaceous rocks, northern Salt Lake 

coal field, Cibola and Catron Counties, New Mexico, in Hook, S.C., compiler, 

Contributions to mid-Cretaceous paleontology and stratigraphy of New Mexico-Part 

II: New Mexico Bureau of Mines and Mineral Resources Circular 185, p. 41-47. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 207 

Type section: Exposures on southwest side of Santa Rita Mesa, 

beginning in Nl/2 sec. 7, T. 4 N., R. 18 W., Moreno Hill quadrangle, 

Cibola County, N. Mex. Named for Moreno Hill. 

The Moreno Hill Formation, here named in west-central New 

Mexico, includes unnamed lower, middle, and upper members. Consists 

of nonmarine olive-gray shale; olive gray, brown, or brown-gray carbonaceous shale; orange to brown, very fine grained to very coarsegrained, poorly sorted, subangular, and steeply crossbedded sandstones; olive-gray to yellow-brown siltstones; and thin coal beds. 

Sandstones are fluvial channel and splay deposits, shales are back-bay 

swamp or lagoon deposits. Overlies the Atarque Sandstone; unconformably underlies the Miocene Fence Lake Formation (new name). Is 

laterally equivalent in part to the Tres Hermanos Formation, Pescado 

Tongue of the Mancos Shale, and Gallup Sandstone. Upper part may be 

laterally equivalent to the lowest part of the Crevasse Canyon Formation. Thickness at the type section, which includes only the lower and 

middle members, is 519 ft. Age is Late Cretaceous (middle and late 

Turonian) based on the middle Turonian age of the underlying Atarque 

Sandstone. 

Morgan School Shale of the Marmaton Group of the 

Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Center of the east line, NWl/4 sec. 18, T. 72 N., R. 22 W., 

Lucas County, Iowa. Named for the former site of Morgan School, 

approximately 1 mi to the southeast. 

Subunit: Summit Coal Member. 

The Morgan School Shale, here named, is in the Marmaton Group of 

the Des Moines Supergroup in southeastern and central Iowa. Includes 

the poorly developed Summit Coal Member (new name), described as 

the Summit coal in Missouri by McGee (1885), at the top. Consists of 

nonmarine and marginal marine clastic olive to brownish-green, calcareous shale and siltstone; a weathered carbonaceous streak marks the 

position of the Summit Coal Member. The Morgan School and the 

underlying Mouse Creek Formation (new name) encompass the lower of 

two depositional cycles in the Marmaton; the overlying Stephens Forest 

Formation (new name) and Labette Formation encompass the upper 
208 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

depositional cycle of the Marmaton. Thickness is 5. 6 ft at the type 

section and ranges from less than 1. 0 ft to 19 ft. Age is Middle 

Pennsylvanian (Desmoinesian). 

Moselem Member of the Virginville Formation 

late Cambrian and Early Ordovician 

Pennsylvania 

Appalachian basin 

Lash, G.G., and Drake, A.A., Jr., 1984, The Richmond and Greenwich slices of the 

Hamburg klippe in eastern Pennsylvania-Stratigraphy, sedimentology, structure, 

and plate tectonic implications: U.S. Geological Survey Professional Paper 1312, 40 p. 

Type locality: Exposures along Maiden Creek north of Moselem and in 

the southern half of the Hamburg quadrangle, Berks County, Pa. 

The Moselem Member of the Virginville Formation (new name), 

here named, is in the Richmond slice of the Hamburg klippe in 

Pennsylvania. Consists of cleaved black and green mudstone and shale 

that has variable amounts of carbonate rock. Tectonically underlies the 

Sacony Member (new name) and Onyx Cave Member (new name) of the 

Virginville. Thickness is 230 m. Age is Late Cambrian and late Early 

Ordovician based on conodonts. 

Mount Hyatt Member of the Gabbs Formation of the Volcano 

Peak Group 

late Triassic (Norian) 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598-1608. 

Type locality: Exposures east of Mount Hyatt, New York Canyon, 

Gabbs Valley Range, Mineral County, Nev. 

The middle member of Muller and Ferguson (1939) of the Gabbs 

Formation, here named the Mount Hyatt Member of the now revised 

Gabbs Formation of the Volcano Peak Group (new name), is in the 

Gabbs Valley Range, west-central Nevada. Consists of grayish-brown 

to medium- and dark-gray, brownish-gray- to orange-brownweathering, medium- to thick-bedded, bioclastic, silty to sandy limestone containing interbeds of calcareous siltstone. Conformably overlies 

the Nun Mine Member (new name) of the Gabbs; sharply and conformably underlies the Muller Canyon Member (new name) of the Gabbs, 

and the contact is drawn above the highest limestone bed of the Mount 

Hyatt. Thickness is 30 m. Age is Late Triassic (Norian) based on fossils. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 209 

Mount Kelly Graywacke Tongue of the Fortress Mountain 

Formation 

Early Cretaceous (Aptian and Albian) 

Alaska 

Arctic Foothills province 

Mull, C.G., 1985, Cretaceous tectonics, depositional cycles, and the Nanushuk Group, 

Brooks Range and Arctic Slope, Alaska, in Huffman, A.C., Jr., ed., Geology of the 

Nanushuk Group and related rocks, North Slope, Alaska: U.S. Geological Survey 

Bulletin 1614, p. 7-36. 

Type locality: Mount Kelly, western foothills of the De Long Mountains, sec. 21, T. 11 S., R. 50 W., Umiat meridian, Arctic slope, Alaska. 

Rocks in the western foothills of the De Long Mountains, in a 

stratigraphic position similar to the Fortress Mountain Formation, 

were assigned to that unit by Chapman and Sable (1960). Because the 

distinctive calcareous, micaceous graywacke lithology is quite different 

from that of the type Fortress Mountain, this rock unit is here named 

the Mount Kelly Graywacke Tongue of the Fortress Mountain Formation. The Fortress Mountain is restricted to the sections of massive 

conglomerate, shale, and noncalcareous, nonmicaceous graywacke 

north of the Endicott and eastern De Long Mountains. Consists of fmeto coarse-grained sandstone containing quartz, chert, muscovite, and 

limestone and other lithic rock fragments in an extremely argillaceous 

matrix, gray silty shale, and mudstone. Bedding features suggest 

turbidite deposition. Base of the tongue is not exposed but may be an 

unconformity; top appears to be gradational and to interfinger with the 

overlying Torok Formation. Structural deformation by folding and 

thrust faulting makes thickness determination impossible but may be 

as much as several hundred meters. Age is late Early Cretaceous 

(Aptian and Albian) based on flora. 

Mount Mineral Formation 

Late Proterozoic 

Massachusetts 

New England province 

Robinson, Peter, and Luttrell, G. W. 1985, Revision of some stratigraphic names in central 

Massachusetts: U.S. Geological Survey Bulletin 1605-A, p. A71-A78. 

Type locality: Mount Mineral, 5 km north of the village of Shutesbury, 

Shutesbury 7.5-minute quadrangle, Franklin County, Mass. 

The informal Mount Mineral Formation of Robinson and others 

(1973), here named, is exposed in the eastern part of the Shutesbury 

quadrangle, Franklin County, Mass. Consists of aluminous schist, 

locally rich in garnet and kyanite, amphibolite, and quartzite. Lenses of 

partially serpentinized harzburgite contain veins of anthophyllite, 
210 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

including the Pelham asbestos quarry. Probably correlates with and 

may be a southern facies of the Poplar Mountain Gneiss of Late 

Proterozoic age. 

Mount Pablo Formation 

Early Cretaceous (Aptian and Albian) 

Montana 

Sweetgrass arch 

Mudge, M.R., and Rice, D.D., 1982, Lower Cretaceous Mount Pablo Formation, 

northwestern Montana: U.S. Geological Survey Bulletin 1502-D, 19 p. 

Type section: Exposure on north side of Badger Creek in the Blackfeet 

Indian Reservation, NEl/4SWlf4 sec. 3, T. 29 N., R. 11 W., Half Dome 

Crag quadrangle, Pondera County, Mont. Named for Mount Pablo in 

the Sawtooth Range, 14 km south of East Glacier Park, Glacier County, 

Mont. 

Subunit: Cut Bank Sandstone Member. 

Strata of the Mount Pablo Formation, here named, were formerly 

assigned to the lower part of the Kootenai Formation, now geographically and stratigraphically restricted; the unnamed formation of Mudge, 

Earhart, and Rice (1977), Mudge, Earhart, and Claypool (1977), Mudge 

and Earhart (1979), and Mudge (1979); and the western facies of the 

Morrison Formation by Mudge (1972). Includes at its base the Cut Bank 

Sandstone Member, here geographically extended to the Sawtooth 

Range from the Cut Bank area where it is a member of the Kootenai 

Formation. Consists of gray, poorly sorted, cross bedded, coarse- to 

very fine grained sandstone and conglomerate in the lower part, 

variegated gray and greenish-gray mudstone interbedded with some 

sandstone in the middle part, and distinctive light-gray limestone 

interbedded with and overlain by gray-brown mudstone in the upper 

part. Unconformably overlies the Morrison Formation in most places; at 

the type section the Cut Bank Sandstone Member unconformably 

overlies the Swift Formation; unconformably underlies the Kootenai 

Formation. Correlates with the lower part of the Kootenai in the Cut 

Bank area. Thickness at the type section is 61 m and ranges from 34 m 

to 90 m. The Mount Pablo is the lowest Cretaceous unit in the Sawtooth 

Range. Age is Early Cretaceous (possibly late Aptian and early Albian) 

based on palynomorphs. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 211 

Mount Watson Formation of the Uinta Mountain Group 

Precambrian 

Utah 

Uinta uplift 

Sanderson, I.D., 1984, The Mount Watson Formation, an interpreted braided-fluvial 

deposit in the Uinta Mountain Group (upper Precambrian), Utah: The Mountain 

Geologist, v. 21, no. 4, p. 157-164. 

Type section: Exposures on Mount Watson, sees. 25 and 36, T. 1 S., 

R. 8 E., and sees. 30 and 31, T. 1 S., R. 9 E., Summit County, Utah. 

Section begins east of Mount Watson at the south end of Wall Lake, 

continues northwest to the east shore of Clyde Lake, and then southwest from the north end of Clyde Lake up the northeast ridge to the 

summit of Mount Watson. 

The Mount Watson Formation of the Uinta Mountain Group, 

informally named by Wallace (1972) and here named, is in the western 

Uinta Mountains of north-central Utah. Consists of a sequence of very 

light gray or almost white quartz arenite and subarkose interbedded 

with minor amounts of pale-red or grayish-red arkosic arenite and 

grayish-green shale. Was deposited in a braided-stream environment. 

Overlies the informal Moosehorn Lake formation of Wallace (1972) and 

underlies the informal Hades Pass formation of Wallace (1972), both of 

the Uinta Mountain Group. Thickness at the type section is 607 m and 

ranges from 550 m in the southeast to 700 m in the northwest. Age is 

late Precambrian. 

Mouse Creek Formation of the Marmaton Group of the 

Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade,J.W., Howes, M.R., Gregory,J.L., Anderson, R.R., and VanDorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Exposures in a gully along Whitebreast Creek, 

NWlf4NElf4NElf4 sec. 8, T. 73 N., R. 22 W., Lucas County, Iowa. 

Named for Mouse Creek, 5 mi to the west-northwest. 

Subunits: Excello Shale Member, Blackjack Creek Limestone Member. 

The Mouse Creek Formation, here named, is the lowermost formation in the Marmaton Group of the Des Moines Supergroup in southeastern and south-central Iowa. Includes the lower Excello Shale 

Member and the upper Blackjack Creek Limestone Member. The 

Excello consists of dark-gray shale containing abundant light-brown 
212 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

phosphate nodules and grades upward into greenish-brown mudstone. 

The Blackjack Creek consists of a single massive bed of argillaceous, 

fossiliferous limestone. Overlies the Swede Hollow Formation (new 

name) of the Cherokee Group of the Des Moines Supergroup; underlies 

the Morgan School Shale (new name) with which it encompasses the 

lower of two depositional cycles in the Marmaton. Thickness at the type 

section is 4. 9 ft; the upper contact is not exposed. Age is Middle 

Pennsylvanian (Desmoinesian). 

Mud Creek Formation of the New Georgia Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Abrams, C.E., and McConnell, K.I., 1981, Stratigraphy of the area around the AustellFrolona antiform; west-central Georgia, in Wigley, P.B., ed., Latest thinking on the 

stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 55--67. 

Type locality: Exposures near and along Mud Creek, New Georgia 

7.5-minute quadrangle, Paulding County, Ga. 

Subunits: Cedar Lake Quartzite Member, Villa Rica Gneiss Member. 

The Mud Creek Formation of the New Georgia Group (new name), 

here named, is in the Villa Rica antiform on the northwest limb of the 

Austell-Frolona antiform in west-central Georgia. Includes the Cedar 

Lake Quartzite Member (new name) and the Villa Rica Gneiss Member 

(new name). Consists of amphibolite, hornblende gneiss, biotite gneiss, 

mica schist, and quartzite. Stratigraphically underlies and grades into 

the Andy Mountain Formation (new name) and Bill Arp Formation (new 

name) of the informal Roosterville group. Age is Proterozoic(?). 

McConnell, K.I., and Abrams, C.E., 1984, Geology ofthe Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Age is Late Proterozoic and (or) early Paleozoic. 

Mulberry Rock Gneiss 

Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C.E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures at Mulberry Rock, New Georgia 7.5-minute 

quadrangle, western Paulding County, Ga. 

The Mulberry Rock Gneiss, here named, is a pre- to synmetamorphic intrusive body at the Allatoona fault, the boundary between the 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 213 

Piedmont and Blue Ridge in the Greater Atlanta region, Georgia. 

Consists of equigranular muscovite-quartz-microcline-plagioclase orthogneiss. Age is Paleozoic. 

Muley Canyon Sandstone Member of the Mancos Shale 

Late Cretaceous (Campanian) 

Utah 

Paradox basin 

Smith, Curtis, 1983, Geology, depositional environments, and coal resources of the Mt. 

Pennell2 NW quadrangle, Garfield County, Utah: Brigham Young University Geology 

Studies, v. 30, pt. 1, p. 145-167. 

Type section: Exposures at the head of Muley Canyon, SEl/4SWl/4 sec. 

16, T. 33 S., R. 7 E., Mt. Pennell2 NW quadrangle,. Garfield County, 

Utah. 

Strata formerly mapped as the Blue gate Sandstone by Gilbert (1877) 

and the Emery Sandstone Member of the Mancos Shale by Hunt (1946) 

are here named the Muley Canyon Sandstone Member in the upper part 

of the Mancos Shale in the Paradox basin, Utah. Consists of a lower 

massive sandstone, 27.5 to 66.7 m thick; a middle slope-forming unit 

that contains coal, carbonaceous mudstone, and sandstone, 30m thick; 

and an upper sandstone, 30m thick. Unconformably overlies the Blue 

Gate Shale Member of the Mancos; unconformably underlies the Masuk 

Shale Member of the Mancos. Correlates with the Star Point Sandstone 

on the Wasatch plateau and with the Drip Tank Member of the Straight 

Cliffs Formation on the Kaiparowits plateau. Thickness ranges from 57 

to 109m. Age is Late Cretaceous (early Campanian). 

Muller Canyon Member of the Gabbs Formation of the 

Volcano Peak Group 

Late Triassic (Norian) 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598--1608. 

Type locality: Exposures on the east flank of Ferguson Hill along the 

west side of Muller Canyon, Gabbs Valley Range, Mineral County, Nev. 

This section is proposed as the stratotype for the Triassic-Jurassic 

System boundary. 

The Muller Canyon Member, here named, is in the now revised 

Gabbs Formation of the Volcano Peak Group (new name) in the Gabbs 

Valley Range, west-central Nevada. The Muller Canyon includes most 

of the upper member of Muller and Ferguson (1939) of the Gabbs and 
214 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

the 10 m of unfossiliferous shales designated by them as the boundary 

between the Gabbs and Sunrise Formations. Consists of pinkish sandy 

siltstone that has small-scale cross-laminations and numerous thin 

gypsum beds. Sharply and conformably overlies the Mount Hyatt 

Member (new name) of the Gabbs; conformably underlies the Ferguson 

Hill Member (new name) of the Sunrise Formation of the Volcano Peak 

Group. Thickness attains 15 m. Age is Late Triassic (Norian) based on 

fossils. 

Mulligan Canyon Rhyolite 

Oligocene 

Nevada 

Great Basin province 

Hose, R.K., 1983, Geologic map of the Cockalorum Wash quadrangle, Eureka and Nye 

Counties, Nevada: U.S. Geological Survey Miscellaneous Investigations Map I-1410, 

scale 1:31,680. 

Type area: Exposures on Bills Peak, southwest of Indian Spring Ranch, 

sec. 10, T. 14 N., R. 51 E., Cockalorum Wash 15-minute quadrangle, 

Nye County, Nev. Named for Mulligan Canyon, sees. 33, 34, and 35, 

T. 15 N., R. 51 E., in the Antelope Range. 

The Mulligan Canyon Rhyolite, here named, is in the Antelope 

Range, Nev. Consists mainly of massive flows of light-gray porphyritic 

rhyolite but is laharlike from the Indian Spring Ranch north to Mulligan 

Canyon. Unconformably overlies the Sheep Spring Rhyolite (new 

name); unconformably underlies the Moonshine Creek Latite (new 

name). Thickness attains 400 m. Age is Oligocene based on stratigraphic 

position. 

Murfreesboro Member of the DeQueen Formation of the 

Trinity Group 

Early Cretaceous 

Arkansas 

Ouachita tectonic belt province 

Darling, B.K., and Lock, B.E., 1984, The surface formations of the Trinity Group in 

southwestern Arkansas and a proposed revision of stratigraphic rank for the three 

lower units: Gulf Coast Association of Geological Societies Transactions, 34th Annual 

Meeting, p. 321-327. 

Type locality: None designated. Probably named for Murfreesboro, 

Pike County, Ark. 

The Murfreesboro Member, here named, is in the easternmost part 

of the DeQueen Formation of the Trinity Group in Pike and Howard 

Counties, Ark. Consists of alternating gray to buff, dense, fossiliferous 

limestone, claystone, and minor amounts of sand, silt, gypsum, and 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 215 

celestite deposited during a time of marine circulation and periods of 

hypersalinity, subaerial exposure, and freshwater flooding. Overlies 

the Highland Gypsum Member (new name) of the DeQueen Formation; 

underlies the Antlers Sand of the Trinity Group. Correlates with the 

lowermost part of the Mooringsport Member of the Rusk Formation in 

the subsurface. Age is Early Cretaceous. 

Musty Buck Member of the Chico Formation 

late Cretaceous (Coniacian and Santonian) 

California 

Sacramento basin 

Haggart, J.W., and Ward, P.D., 1984, Late Cretaceous (Santonian-Campanian) stratigraphy of the northern Sacramento Valley, California: Geological Society of America 

Bulletin, v. 95, no. 5, p. 618-627. 

Type section: Exposures on Big Chico Creek, from the center sec. 1 to 

west margin sec. 13, T. 23 N., R. 2 E., Butte County, Calif. Derivation 

of name not stated. 

The Musty Buck Member, informally named by Saul (1961) and here 

named, is in the Chico Formation along Big Chico, Butte, Deer, and Mill 

Creeks, Butte and Tehama Counties, northeastern Sacramento Valley, 

Calif. Consists of greenish-gray to tan, arkosic, cross-stratified, bioturbated sandstone containing extensive pebble beds and local shell-lag 

deposits. Unconformably overlies pre-Cretaceous metamorphic rocks or 

conformably overlies the Ponderosa Way Member (new name) of the 

Chico; conformably underlies the Ten Mile Member (new name) of the 

Chico. Upper part of the Musty Buck is correlative with the Guinda 

Formation of the western Sacramento Valley. Thickness ranges from 

110 to 215m. Age is Late Cretaceous (Coniacian and Santonian) based 

on ammonites. 

Nacoochee Formation of the Helen Group 

late Proterozoic and Paleozoic 

Georgia, North Carolina 

Piedmont-Blue Ridge province 

Nelson, A.E., and Gillon, K.A., 1985, Stratigraphic nomenclature in the Richard Russell 

and Helen thrust sheets, Georgia and North Carolina: U.S. Geological Survey Bulletin 

1605-A, p. A59-A62. 

Type locality: Exposures along Chattahoochee River from the 

Nacoochee bridge on Georgia Highway 17 for 0.3 mi, Helen 7.5-minute 

quadrangle, White County, Ga. (Gillon, 1982). 

The Nacoochee Formation of the Helen Group (new name), informally named by Gillon (1982) and here named, is in the Helen thrust 

sheet in Georgia and North Carolina. Consists of an interlayered 
216 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

sequence of amphibolite and graphitic-aluminous schist and minor 

amounts of micaceous metasandstone, feldspathic metasiltstone, epidote quartzite, and biotite schist. Is gradational and conformable with 

the Horton Formation (new name) of the Helen Group to the west and 

is truncated on the southeast by the Dahlonega fault. Age is tentatively 

set at Late Proterozoic and early Paleozoic. 

Nahahum Canyon Member of the Chumstick Formation 

Eocene 

Washington 

Northern Cascade Range-Okanogan province 

Gresens, R.L., Naeser, C.W., and Whetten, J.W., 1981, Stratigraphy and age of the 

Chumstick and Wenatchee Formations: Tertiary fluvial and lacustrine rocks, Chiwaukum graben, Washington: Geological Society of America Bulletin, v. 92, no. 5, pt. I, 

p. 233-236; pt. II, p. 841-876. 

Type section: East flank of the Eagle Creek anticline about 0.5 km east 

of the Van Creek road extending for 1.3 km along the Eagle Creek road, 

sees. 13 and 24, T. 25 N., R. 18 E., and sec. 19, T. 25 N., R. 19 E., north 

of Leavenworth, Chelan County, Wash. Named for N ahahum Canyon 

northeast of Cashmere. 

The shaly sandstone and shale of Whetten and Laravie (1976) are 

here named the Nahahum Canyon Member in the upper part of the 

Chumstick Formation (new name) on the northeast side and northwest 

end of the Chiwaukum graben in the central Cascade Range of Washington. Consists of fine-grained shaly sandstone and shale containing 

thin laminae of biotite and organic matter, suggestive of quiet-water 

deposition in a shallow lake environment. Conformably overlies the 

lower part of the Chumstick; grades laterally into sandstone and 

conglomerate of the Chumstick near the Entiat fault and near the core 

of the Eagle Creek anticline; unconformably underlies the Wenatchee 

Formation (new name). Thickness is about 2,000 m. Age is middle(?) 

Eocene based on a zircon age of about 45 Ma for tuff in the lower part of 

the Chumstick and an age of 34 Ma for volcanic rocks in the Wenatchee. 

Nash Stream Till 

Pleistocene (Wisconsinan) 

New Hampshire 

New England province 

Koteff, Carl, and Pessl, Fred, Jr., 1985, Till stratigraphy in New Hampshire: Correlations 

with adjacent New England and Quebec, in Borns, H.W., Jr., and others, eds., Late 

Pleistocene history of northeastern New England and adjacent Quebec: Geological 

Society of America Special Paper 197, p. 1-12. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 217 

Type locality: Composite of outcrops along Nash Stream, Coos County, 

N.H. 

The lower till at Nash Stream, northern New Hampshire, is here 

named the Nash Stream Till. Consists of dark-olive-gray compact, silty 

till containing clasts of Ordovician and Devonian quartz monzonite, 

schist, and phyllite in a silt and clay matrix. Oxidation, which extends to 

a depth of 10 m, suggests a long interval before deposition of the 

unconformably overlying Stratford Mountain Till (new name) or glaciolacustrine outwash. Correlates with the [informal] New Sharon till in 

Maine and the J ohnville Till in Quebec. Maximum thickness is 21 m. 

Age is late Pleistocene (early Wisconsinan) based on the depth of 

weathering. 

Nashville Member of the Copper Falls Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Exposures in gravel pit in drumlin, SE1/4SW1/4SE1/4 sec. 7, 

T. 35 N., R. 12 E., Nashville 7.5-minute quadrangle, southwestern 

Forest County, Wis. Named for the Township of Nashville. 

Following the informal usage of Simpkins (1979), the Nashville 

Member of the Copper Falls Formation (new name), here named, is in 

the Chippewa Sublobe in Forest, Langlade, and Oneida Counties, Wis. 

Consists of reddish-brown, yellowish-red, and dark-brown pebbly, 

sandy loam till containing sand lenses. Sharply overlies the Marathon 

and Lincoln Formations (both new names) and overlies and intertongues with the stratigraphically equivalent Mapleview Member of the 

Horicon Formation (both new names); sharply underlies sand and 

gravel of the Copper Falls Formation or is the surface unit. Thickness 

ranges from 2 to 17 m. Age is late Pleistocene (late Wisconsinan). 

Nassawadox Formation 

Pleistocene 

Virginia 

Atlantic Coast basin 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of uppermost Cenozoic 

deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological 

Survey Professional Paper 1067-G, 53 p. 

Type section: Borehole Ch-11, east end of Route 648, 0.5 mi eas~ 

of Stumptown, west of the Penn Central Railroad, 10 mi southsouthwest of the town of Nassawadox, Cheriton 7.5-minute quadrangle, 

Northampton County, Va. 
218 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Subunits: Stumptown Member, Butlers Bluff Member, Occohannock Member. 

Sand and gravel deposits that underlie the Franktown plain and 

southern upland in the area south of the Ames Ridge shoreline in the 

Delmarva Peninsula, Va., are here named the Nassawadox Formation. 

Includes the lower subsurface Stumptown Member (new name), which 

unconformably overlies the Eastover and Yorktown Formations; the 

Butlers Bluff Member (new name), which forms the upper part of the 

Nassawadox in the southern upland area; and the upper Occohannock 

Member (new name), which conformably overlies the Butlers Bluff 

Member to the southwest. Thickness at the type section is 200ft and 

ranges from 20 to 200 ft. Age is Pleistocene. 

Nellysford Granulite Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., Gathright, T.M., II, and Henika, W.S., 1981, A tectonic model for 

the Blue Ridge in central Virginia: American Journal of Science, v. 281, no. 9, 

p. 1164-1183. 

Type locality: Near Nellysford, Sherando 7.5-minute quadrangle, 

Nelson County, Va. 

The Nellysford Granulite Gneiss, here named, is in the Pedlar massif 

in the central Blue Ridge, Va. Consists of well-layered, dark grayishgreen to dark-green, fine- to medium-grained, granoblastic, garnethypersthene-quartz-feldspar gneiss. Occurs along the eastern margin of 

and as roof-pendants in the Pedlar River pluton [Pedlar River Charnockite Suite (new name)]. Contacts with the pluton are concordant and 

gradational. Age is Middle Proterozoic. 

New Berlin Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene ~tratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Exposures in gravel pit on north side of Highway I 

(Lawnsdale Road), 0.8 to 1.6 km west of Highway Y (Racine Avenue), 

SE1/4 sec. 19 and SW1/4 sec. 20, T. 6 N., R. 20 E., Muskego 7.5-minute 

quadrangle, Waukesha County, Wis. Named for the city of New Berlin. 

The New Berlin Formation, here named, is in the Lake Michigan 

Lobe in southeastern Wisconsin. Consists of brown to yellowish-brown, 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 219 

sandy, pebbly, calcareous till and is divided into an informal lower sand 

and gravel member and an upper till member. At several places the till 

splits into two units, informally designated 1A and 1B by Mickelson and 

others (1977), separated by outwash sand and gravel deposits. Sharply 

to gradationally overlies the Tiskilwa Member of the Zenda Formation 

(new name); sharply or unconformably underlies the Oak Creek Formation (new name) or various members of the Kewaunee Formation (new 

name) in the Lake Michigan Lobe; is the surface unit in much of 

Waukesha and Walworth Counties. Correlates with the Horicon Formation (new name) of the Green Bay Lobe. Thickness is at least 22 m. 

Age is late Pleistocene (late Wisconsinan). 

New Bern Formation 

Eocene 

North Carolina 

Atlantic Coast basin 

Baum, G.R., Harris, W.B., and Zullo, V.A., 1978, Stratigraphic revision of the exposed 

middle Eocene to lower Miocene formations of North Carolina: Southeastern Geology, 

v. 20, no. 1, p. 1-19. 

Type section: Exposure at Martin Marietta quarry at New Bern, 

Craven County, N.C. 

The New Bern Formation, here named, is in the area lying between 

the Neuse and Trent Rivers, Craven and Jones Counties, N.C. Consists 

of predominantly sandy, basal pelecypod-mold biomicrosparrudite, 6 m 

thick, and overlying biosparite and biosparrudite, 1.8 m thick, and 

biomicrosparrudite, 1.4 m thick. Disconformably overlies the Castle 

Hayne Limestone; disconformably underlies the Trent or Yorktown 

Formation. Age is late Eocene. 

New Georgia Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Abrams, C. E., and McConnell, K.I., 1981, Stratigraphy of the area around the AustellFrolona antiform; west-central Georgia, in Wigley, P.B., ed., Latest thinking on the 

stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 55-67. 

Type locality: None designated. Named for the town of New Georgia, 

near Dallas, Paulding County, Ga. 

Subunits: Mud Creek Formation and its Cedar Lake Quartzite Member 

and Villa Rica Gneiss Member. 

The informal Dallas group of McConnell and Costello (1980), here 

formally named the New Georgia Group, occupies the Villa Rica 
220 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

antiform, an upwarped area on the northwestern limb of the AustellFrolona antiform in west-central Georgia. The name is changed to 

prevent confusion with the better known geographic locality of Dallas, 

Tex. Includes the Mud Creek Formation (new name) and its Cedar Lake 

Quartzite Member (new name) and Villa Rica Gneiss Member (new 

name). Consists of an interlayered sequence of metamorphosed mafic 

and felsic volcanic and plutonic rocks containing minor amounts of 

metasedimentary rocks. Grades upward into the stratigraphically overlying but structurally underlying Andy Mountain and Bill Arp Formations (both new names) of the informal Roosterville group of the 

Austell-Frolona antiform. Age is Proterozoic(?). 

McConnell, K.I., and Abrams, C.E., 1984, Geology ofthe Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Subunits: Laura Lake Mafic Complex and its Kennesaw Gneiss Member, Kellogg Creek Mafic Complex, Univeter Formation and its Lost 

Mountain Amphibolite Member and Rose Creek Schist Member, Mud 

Creek Formation and its Cedar Lake Quartzite Member and Villa Rica 

Gneiss Member, Pumpkinvine Creek Formation and its Gaits Ferry 

Gneiss Member, Canton Formation, Acworth Gneiss. 

In the Greater Atlanta region of northwest Georgia, the New 

Georgia Group includes the Laura Lake Mafic Complex and its Kennesaw Gneiss Member (both new names), the Kellogg Creek Mafic 

Complex (new name), the Univeter Formation and its Lost Mountain 

Amphibolite Member and Rose Creek Schist Member (all new names), 

the Mud Creek Formation and its Cedar Lake Quartzite Member and 

Villa Rica Gneiss Member (all new names), the Pumpkinvine Creek 

Formation and its Gaits Ferry Gneiss Member (new name), the Canton 

Formation, and the Acworth Gneiss. Age is Late Proterozoic and (or) 

early Paleozoic. 

Newport Sand Member of the Flanner Beach Formation 

Pleistocene 

North Carolina 

Atlantic Coast basin 

Miller, William, III, 1985, The Flanner Beach Formation (middle Pleistocene) in eastern 

North Carolina: Tulane Studies in Geology and Paleontology, v. 18, no. 3, p. 93-122. 

Type locality: Sand ridges extending from the town of Newport to the 

vicinity of Bogue, Carteret County, N.C. (Mixon and Pilkey, 1976). 

A barrier-sand lithosome associated with ridge-and-swale landforms 

in the Neuse River valley in Carteret County, N.C., is here named the 

Newport Sand Member of the Flanner Beach Formation, following the 

informal usage of Mixon and Pilkey (1976). Consists of pale-yellowishgray, crossbedded, fine to coarse, well-sorted quartz sand that has 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 221 

quartz and chert pebbles and zones impregnated with black organic 

colloids. Intertongues with the Beard Creek Member (new name) of the 

Flanner Beach to the northwest. Thickness ranges from 3 to 12 m. Age 

is middle Pleistocene. 

New York Canyon Member of the Sunrise Formation of the 

Volcano Peak Group 

Early jurassic (Sinemurian) 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598--1608. 

Type locality: Exposures near the mouth of New York Canyon, Gabbs 

Valley Range, Mineral County, Nev. 

Unit 8 of Muller and Ferguson (1939) of the Sunrise Formation is 

here named the New York Canyon Member of the now revised Sunrise 

Formation of the Volcano Peak Group (new name) in the Gabbs Valley 

Range in west-central Nevada. Consists of blue-gray, orange-brownweathering, medium- to thick-bedded bioclastic limestone. Conformably 

overlies the Five Card Draw Member (new name) of the Sunrise; 

sharply and conformably underlies the Joker Peak Member (new name) 

of the Sunrise. Thickness is 120 m. Age is Early Jurassic (Sinemurian) 

based on fossils. 

Nimtz Till Member of the Winnebago Formation 

Pleistocene (Illinoian) 

Wisconsin 

Wisconsin arch 

Berg, R.C., and Kempton, J.P., 1985, Winnebago and Glasford Formation diamictons at 

the Nimtz Quarry Section: Illinois Geological Survey and Midwest Friends of the 

Pleistocene, 32d field conference, guidebook 19, p. 87-97. 

Type section: Nimtz Quarry Section, 5 km east of Loves Park, Nlf2SE1/4 

sec. 33, T. 45 N., R. 2 E., Winnebago County, Ill. 

The Nimtz Till Member of the Winnebago Formation, here named, 

occurs primarily in the subsurface east of the Rock River in Winnebago, 

Boone, and McHenry Counties, Ill. Consists of gray-brown or buff loam 

to sandy loam diamicton, which is 69 percent illite. Was previously 

described as the Argyle Till Member, but it has been determined to be 

stratigraphically distinct from the overlying Argyle diamicton, which is 

63 percent illite. Overlies the Beaver Creek Sand Member (new name) 
222 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

of the Winnebago or the Belvidere Till Member (new name) of the 

Glasford Formation. Thickness is less than 15 m. Age is Pleistocene 

(Illinoian). 

Norcross Gneiss of the Atlanta Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Industrial parks on both sides of Jimmy Carter Boulevard southeast of Interstate Highway I--85, Norcross 7.5-minute quadrangle, Gwinnett County, Ga. Named for the city of Norcross. 

The Norcross Gneiss of the Atlanta Group (new name), here named, 

is in the Newnan-Tucker synform near Atlanta, Ga. Consists of wellfoliated gray, epidote-biotite-muscovite-plagioclase gneiss containing 

pods and lenses of amphibolite. Sharply and conformably overlies the 

Inman Yard Formation (new name) of the Atlanta Group; lies in sharp 

contact and correlates with the Wolf Creek Formation (new name) of 

the Atlanta to the southwest; gradationally and conformably underlies 

the Clairmont Formation (new name) of the Atlanta. Thickness is 2,000 

m. Age is Late Proterozoic and (or) early Paleozoic. 

Norris Lake Schist Member of the Snellville Formation 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Outcrops in No Business Creek, just below the dam at 

Norris Lake, Snellville quadrangle, Gwinnett County, Ga. 

The Norris Lake Schist Member is here named the lower member of 

the Snellville Formation (new name) in the Newnan-Tucker synform 

near Atlanta, Ga. Consists of interlayered garnet-biotite-muscovite 

schist, hornblende-plagioclase amphibolite, and minor amounts of biotite gneiss and quartzite. Discordantly overlies the Lithonia Gneiss and 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 223 

Atlanta Group (new name); underlies the Lanier Mountain Quartzite 

Member (new name) of the Snellville. Thickness is 30m. Age is Late 

Proterozoic and (or) early Paleozoic based on an age of 1,100 Ma for 

detrital zircons from the Lanier Mountain Quartzite Member. 

Novi Mountain Formation 

Early Ordovician 

Alaska 

Holitna basin 

Dutro, J.T., Jr., and Patton, W.W., Jr., 1982, New Paleozoic formations in the northern 

Kuskokwim Mountains, west-central Alaska: U.S. Geological Survey Bulletin 1529-H, 

p. H13-H22. 

Type section: East and west flanks of Novi Mountain, sees. 29, 30, and 

32, T. 17 S., R. 28 E., Medfra (D-1) quadrangle, Alaska. 

The N ovi Mountain Formation, here named, is in the Nixon Fork 

terrane of the Kuskokwim Mountains, Alaska, where it was deposited in 

a shallow-water carbonate environment. Consists of calcareous siltstone 

and shale and has evidence of bioturbation in the lower third of the unit. 

The upper two-thirds are characterized by 5- to 30-m-thick carbonate 

cycles of limestone, shaly limestone, and calcareous siltstone. Outcrops 

are variegated gray carbonate rocks alternating with yellowweathering siltier rocks. Overlies Precambrian or lower Paleozoic 

calc-schist; conformably underlies the Telsitna Formation (new name). 

Thickness is 900 m. Age is Early Ordovician based on conodonts. 

Noxapaga Formation 

Tertiary 

Alaska 

Yukon-Koyukuck province 

Sainsbury, C.L., 1974, Geologic map of the Bendeleben quadrangle, Seward Peninsula, 

Alaska: U.S. Bureau of Mines, U.S. Geological Survey, and The Mapmakers, 31 p., 

scale 1:150,000. 

Type area: Tertiary basin traversed by the N oxapaga River, western 

Bendeleben quadrangle, Seward Peninsula, Alaska. 

Rocks of unquestionable Tertiary age exposed only in trenched 

pingos west of the Noxapaga River in the small Tertiary basin in the 

western part of the Bendeleben quadrangle, Alaska, previously 

assigned to the younger Kougarok Gravel by Hopkins (1963), are here 

named the Noxapaga Formation. Consists of conglomerate, sandstone, 

thin lignitic coal, and fireclay. Unconformably underlies unconsolidated 

Pleistocene Kougarok Gravel. 
224 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Nun Mine Member of the Gabbs Formation of the Volcano 

Peak Group 

late Triassic (Norian) 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598-1608. 

Type locality: Exposures near Luning Draw, Gabbs Valley Range, 

Mineral County, Nev. Named for the Nun mine near Five Card Draw. 

The lower member of Muller and Ferguson (1939) of the Gabbs 

Formation is here named the Nun Mine Member of the now revised 

Gabbs Formation of the Volcano Peak Group (new name) in the Gabbs 

Valley Range in west-central Nevada. Consists of dark-gray to black, 

grayish-purple-weathering, thin-bedded, calcareous mudstone and siltstone intercalated with thin to thick beds of black limestone. Conformably overlies the Luning Formation; sharply and conformably underlies 

the Mount Hyatt Member (new name) of the Gabbs. Thickness is 90 m. 

Age is Late Triassic (Norian) based on fossils. 

Oak Creek Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Oakwood Road South Section, in Lake Michigan bluffs 

between Oakwood Road and Elm Road, north of Oak Creek Power 

Plant, NE1/4NE1/4NE1/4 sec. 36, T. 5 N., R. 22 E., and NW¥4 sec. 31, 

T. 5 N., R. 23 E., Racine North 7.5-minute quadrangle, Milwaukee 

County, Wis. Named for the city of Oak Creek. 

The Oak Creek Formation, here named, is in the Lake Michigan 

Lobe in southeastern Wisconsin. Consists of fine-grained glacial till, 

lacustrine clay, silt, and sand, and glaciofluvial sand and gravel. Three 

till units designated 2A, 2B, and 2C, were identified by Mickelson and 

others (1977). Sharply or unconformably overlies the upper till member 

of the New Berlin Formation (new name); sharply underlies lacustrine deposits or the Kewaunee Formation (new name), or occurs as 

surface drift. Thickness attains 35 m. Age is Pleistocene (late 

Wisconsinan). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 225 

Oakley Shale Member of the Swede Hollow Formation of the 

Cherokee Group of the Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Exposures along a tributary to Whitebreast Creek at the 

Swede Hollow type section, sees. 33 and 34, T. 73 N., R. 22 W., and sec. 

3, T. 72 N., R. 22 W., Lucas County, Iowa. Named for the community 

of Oakley in northern Lucas County. 

The Oakley Shale Member of the Swede Hollow Formation (new 

name) of the Cherokee Group, here named, is in southern Iowa. 

Consists of fissile, black shale, containing phosphate nodules at the 

base, overlain by bioturbated gray shale in the eastern area. In the 

western area the black fissile facies is underlain by gray shale containing 

plant fossils. Overlies the Whitebreast Coal Member (new name) of the 

Swede Hollow with a sharp, irregular contact; underlies the Ardmore 

Limestone Member of the Swede Hollow. The black shale bed may be 

equivalent to the Mecca Quarry Shale in northeastern Illinois. Thickness ranges from 1. 5 ft at the type section to 25 ft in the western area. 

Age is Middle Pennsylvanian (Desmoinesian). 

Occohannock Member of the Nassawadox Formation 

Pleistocene 

Virginia 

Atlantic Coast basin 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of uppermost Cenozoic 

deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological 

Survey Professional Paper 1067-G, 53 p. 

Type section: Exposures in west-facing cliff at the mouth of Shields 

Cove on the north side of Occohannock Creek, 2. 5 mi west of Bell 

Haven, Delmarva Peninsula, Northampton County, Va. Reference 

section: Cliffs on south bank of Occohannock Creek, Shooting Point, and 

Hungars Beach. 

Surficial deposits of the Franktown plain, Northampton County, 

Va., are here named the Occohannock Member, the upper member of 

the Nassawadox Formation (new name). Consists of light-yellowishgray, fine to medium quartz sand beds. Disconformably overlies the 

Accomack Member (new name) of the Omar Formation to the north; 

conformably to disconformably overlies the Butlers Bluff Member (new 
226 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

name) of the Nassawadox to the southwest; is truncated and overlapped 

by the Kent Island Formation or lies at the surface. May be equivalent 

to the Joynes Neck Sand (new name). Thickness at the type section is 15 

ft and ranges from 7 to 20 ft. Age is Pleistocene. 

Ochoa Point Member of the Dox Formation of the Unkar 

Group 

Middle Proterozoic 

Arizona 

Plateau sedimentary province 

Stevenson, G.M., and Beus, S.S., 1982, Stratigraphy and depositional setting of the upper 

Precambrian Dox Formation in Grand Canyon: Geological Society of America Bulletin, 

v. 93, no. 2, p. 163-173. 

Type section: Exposures in an unnamed streamway on the southwest 

side of Ochoa Point, a promontory west of Basalt Canyon on the 

northwest side of the Colorado River, eastern Grand Canyon, Vishnu 

Temple quadrangle, Coconino County, Ariz. 

The Ochoa Point Member is here named the uppermost member of 

the Dox Formation of the Unkar Group in the eastern Grand Canyon, 

Ariz. The lower half consists of slope-forming, reddish-brown, micaceous siltstone containing thin interbeds of sandstone. Upper half 

consists of steep-slope-forming, thicker and more closely spaced sandstone beds containing thin shale partings. Represents tidal-flat deposits. Gradationally overlies the Comanche Point Member (new name) of 

the Dox; conformably underlies the Cardenas Lavas. Thickness is 76 m 

at the type section and ranges from 53 to 91 m. Age is Middle 

Proterozoic based on the age of the overlying Cardenas Lavas (1.1 Ma). 

Ocmulgee Formation of the Ocala Group 

Eocene 

Georgia 

Atlantic Coast basin 

Huddlestun, P.F., and Hetrick, J.H., 1985, Upper Eocene stratigraphy of central and 

eastern Georgia: Georgia Geologic Survey Bulletin 95, 78 p. 

Type locality: Exposures at Taylors Bluff on the east side of the 

Ocmulgee River, 2. 7 mi north of Hawkinsville, Pulaski County, Ga. 

The Ocmulgee Formation of the Ocala Group, here named, is in the 

Georgia Coastal Plain from Houston and Pulaski Counties in the west to 

as far east as the Savannah River. Previously mapped as the Cooper 

Marl, but the units are not laterally equivalent. Consists of a basal 

sandy, glauconitic, indurated limestone overlain by tough, massive, 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 227 

glauconitic, granular, even-textured, slightly argillaceous, calcarenitic 

limestone. Conformably overlies the Twiggs Clay Member of the Dry 

Branch Formation; paraconformably underlies the Marianna Limestone. Thickness at the type locality is 35 ft. Age is late Eocene. 

Oconee Coal Member of the Mattoon Formation of the 

Mcleansboro Group 

Late Pennsylvanian (Missourian) 

Illinois 

Illinois basin 

Nance, R.B., and Treworgy, C.G., 1981, Strippable coal resources of Illinois: Part 8-

Central and southeastern counties: Illinois Geological Survey Circular 515, 32 p. 

Type section: Exposure in a west-flowing tributary to Coal Creek, 4 mi 

north ofthe village of Oconee, SEl/4SEl/4SEl/4 sec. 34, T. 11 N., R. 1 E., 

approximately 300 ft north of the county line road in Christian County, 

Ill. 

The Oconee Coal Member of the Mattoon Formation of the 

McLeansboro Group, here named, is in Shelby, Cumberland, Effingham, and Jasper Counties, Ill. Lies 25 to 40 ft above the Loudon Coal 

Member (new name) and 60 to 110ft below the Shelbyville Coal Member 

of the Mattoon Formation. Thickness is 1 ft at the type section. Age is 

Late Pennsylvanian (Missourian). 

Oil Creek Formation 

Oligocene 

California 

Eel River basin 

Bachman, S.B., Underwood, M.B., and Menack, J.S., 1984, Cenozoic evolution of coastal 

northern California, in Crouch, J.K., and Bachman, S.B., eds., Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and 

Mineralogists, Pacific Section, p. 55-66. 

Type locality: Oil Creek near False Cape, 6 mi southwest of Ferndale, 

Humboldt County, Calif. 

The Oil Creek Formation, here named, is in the Eel River basin, 

California. Consists of a debris flow containing clasts of sandstone, 

shale, and conglomerate derived from the Coastal Belt Complex and 

less indurated siltstones of unknown origin. Concordantly overlies the 

Coastal Belt Complex; unconformably underlies fractured rocks of the 

Wildcat Group. Unit may represent deposition during a period of 

regional uplift preceding the main phase of Wildcat deposition. Thickness is 33 ft. Age is Oligocene based on microfauna. 
228 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Old Church Formation of the Chesapeake Group 

Oligocene and Miocene 

Virginia, Maryland 

Atlantic Coast basin 

Ward, L.W., 1985, Stratigraphy and characteristic mollusks of the Pamunkey Group 

(lower Tertiary) and the Old Church Formation of the Chesapeake Group-Virginia 

Coastal Plain: U.S. Geological Survey Professional Paper 1346, 78 p. 

Type section: Exposure at USGS locality 26412 on the south bank of the 

Pamunkey River at Horseshoe, Manquin 7.5-minute quadrangle, 

Hanover County, Va. Named for the nearby village of Old Church. 

The upper Oligocene or lower Miocene beds in the outcrop area on 

the Pamunkey River from above Horseshoe to below the mouth of 

Matadequin Creek, Va., are here named the Old Church Formation of 

the Chesapeake Group. Consists of grayish-olive, clayey quartz sands 

containing molluskan shell fragments, foraminifers, ostracodes, and 

small amounts of reworked glauconite. Irregular indurated masses 

occur as boulder-size concretions. Unconformably overlies the Piney 

Point Formation; unconformably underlies the Calvert Formation. 

Thickness ranges from less than 1 ft to 3 ft. A bed along the Patuxent 

River in Maryland, called zone 1 of the Calvert Formation by Shattuck 

(1904), that lies unconformably between the Woodstock Member of the 

Nanjemoy Formation and Shattuck's (1904) zone 2 of the Calvert 

Formation, may be equivalent to and belong in the Old Church. 

Subsurface beds in Maryland, Delaware, and New Jersey, mapped as 

the Piney Point Formation by Olsson and others (1980), are equivalent 

to the Old Church. Ward and others (1978) correlated the Pamunkey 

River outcrop with the Chickasawhayan-age River Bend Formation in 

North Carolina. 

Old Mill Branch Metasiltstone Member of the Popes Head 

Formation 

late Proterozoic and (or) Early Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., and Lyttle, P.T., 1981, The Accotink Schist, Lake Barcroft Metasandstone, and Popes Head Formation-Keys to an understanding of the tectonic evolution 

of the northern Virginia Piedmont: U.S. Geological Survey Professional Paper 1205, 

16 p. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 229 

Type locality: Exposures along Old Mill Branch between Clifton Road 

and the Occoquan Reservoir, Manassas 7.5-minute quadrangle, Fairfax 

County, Va. 

The Old Mill Branch Member of the Popes Head Formation (new 

name), here named, is in Fairfax County, northern Virginia. Consists of 

alternating beds of coarser grained micaceous metasiltstone and metasandstone and finer grained metapelite and micaceous metasiltstone 

containing interbedded felsic and mafic metatuff layers. Is isoclinally 

folded and phyllitic cleavage is subparallel to bedding. Discordantly 

overlies all other rocks of the Wissahickon terrane in Fairfax County; 

gradationally underlies the Station Hills Phyllite Member (new name) of 

the Popes Head; is intruded by the Occoquan Granite. Maximum 

thickness is about 730 m. Age is Late Proterozoic and (or) Early 

Cambrian based on the age of the Occoquan Granite, which has been 

determined radiometrically to be Early Cambrian. 

Olds Member of the Bell Canyon Formation of the Delaware 

Mountain Group 

Late Permian (Guadalupian) 

Texas, New Mexico 

Permian basin 

Winner, Phil, 1985, Type section for the uppermost Bell Canyon Formation in the central 

Delaware basin of West Texas: West Texas Geological Society Bulletin, v. 24, no. 7, 

p. 7-10. 

Type section: Gulf J.R. Grandin Number 1 well, sonic-gamma ray log, 

SEl/4 sec. 33, Block 29 PSL Survey, Loving County, Tex. Named for the 

Olds field, Reeves County, Tex. 

The Olds Member, here named, is in the informal A sand in the 

upper Bell Canyon Formation of the Delaware Mountain Group in the 

central Delaware basin in Texas and New Mexico. Previously designated the informal unranked Olds sand by Nottingham (1960) and the 

Olds sandstone member, the main pay in the Olds field, by Grauten 

(1965). Produces in the Olds, Hays, Quito, and Grice fields. Consists of 

silty, fine-grained sandstone and has an upward increase in sonic 

porosity; four separate sand units have been mapped locally. The base 

is picked at the first shale above the top of the Bell Canyon B sand 

where sonic porosity shows a significant increase. Overlies the Hays 

Member (new name) and underlies the Ford Member (new name), both 

of the Bell Canyon. Is regionally extensive but is absent to the north 

beneath the Paduca field. Thickness ranges from 0 to 50 ft. [Age is Late 

Permian (Guadalupian).] 
230 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Onaway Member of the Wanapum Basalt of the Columbia 

River Basalt Group 

Miocene 

Idaho, Washington 

Eastern Columbia basin 

Camp, V.E., 1981, Geologic studies of the Columbia Plateau: Part II. Upper Miocene 

basalt distribution, reflecting source locations, tectonism, and drainage history in the 

Clearwater embayment, Idaho: Geological Society of America Bulletin, v. 92, no. 9, 

pt. I, p. 669-678. 

Type locality: Potlatch River area near and around Onaway, Latah 

County, Idaho. 

The Onaway Member of the Wanapum Basalt of the Columbia River 

Basalt Group, here named, is in the Potlatch River area of the 

Clearwater embayment in western Idaho and adjoining eastern Washington. Consists of several flows of medium- to coarse-grained basalt 

containing plagioclase phenocrysts extruded from vents extending from 

Palouse, Wash., to Potlatch, Troy, and Joel, Idaho. The informal basalt 

of Potlatch is the only mappable flow in the member. The Onaway is at 

the top of the W anapum and contains flows that lie both below and 

above the Priest Rapids Member of the Wanapum; hence the WanapumSaddle Mountains Basalt contact is redefined at the top of the Onaway. 

Age is late Miocene. 

Onyx Cave Member of the Virginville Formation 

Late Cambrian and Early Ordovician 

Pennsylvania 

Appalachian basin 

Lash, G.G., and Drake, A.A., Jr., 1984, The Richmond and Greenwich slices of the 

Hamburg klippe in eastern Pennsylvania-Stratigraphy, sedimentology, structure, 

and plate tectonic implications: U.S. Geological Survey Professional Paper 1312, 40 p. 

Type locality: Exposures at Onyx Cave, Hamburg 7.5-minute quadrangle, Berks County, Pa. 

The Onyx Cave Member of the Virginville Formation (new name), 

here named, is in the Richmond slice of the Hamburg klippe in 

Pennsylvania. Consists of four distinct rock types: granular and quartzose limestone, interbedded black lime mudstone and limestone, massive 

carbonate-clast conglomerate, and laminated black shale and orange 

dolostone. Conformably overlies the Sacony Member (new name) of the 

Virginville; tectonically overlies the Moselem Member (new name) of 

the Virginville. Minimum thickness is 90 m. Age is Late Cambrian and 

Early Ordovician based on conodonts. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 231 

Oreanna Bed 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Badlands on the west side of the Humboldt River, 7.6 km 

south of Rye Patch Dam and 7. 7 km north of Oreanna, NE1/4SW1/4SW1/4 

sec. 6, T. 29 N., R. 33 E., Oreanna 15-minute quadrangle, Pershing 

County, Nev. 

The Oreanna Bed, here named, is exposed between Rye Patch Dam 

and Oreanna on the Humboldt River, Lake Lahontan area, Nevada. Is 

attributed to a source at the Island Park Caldera of northeastern Idaho 

because it is chemically and petrographically similar to Pearlette ash 

beds 0 and B, which are correlative to welded tuffs of the Yellowstone 

Group in Yellowstone Park. Age is Pleistocene, 600 ka. 

Oregon Till Member of the Glasford Formation 

Pleistocene (Illinoian) 

lllinois 

Wisconsin arch 

Kempton, J.P., Berg, R.C., and Follmer, L.R., 1985, Revision of the stratigraphy and 

nomenclature of glacial deposits in central northern Illinois: Illinois Geological Survey, 

Midwest Friends of the Pleistocene, 32d field conference, guidebook 19, p. 1-19. 

Type section: Grand Detour Section, 16 km south of Oregon, 

SW1/4SW1/4NE1/4 sec. 25, T. 22 N., R. 9 E., Lee County, Ill. 

The recognition that the Esmond Till Member is a unit of the 

Illinoian Glasford Formation rather than of the Wisconsinan Wedron 

Formation has left three unnamed till members below the Esmond 

Member. The upper till is here named the Oregon Till Member of the 

Glasford Formation for its widespread occurrence near Oregon in Ogle 

County, and in Boone, Winnebago, and Lee Counties, Ill. Consists of a 

pinkish-brown loam to sandy loam diamicton. Its siltier finingdownward component is referred to as the Oregon Till Member silty 

facies by Kempton and Berg (1985). Overlies the Fairdale Till Member 

(new name) and underlies the Esmond Till Member, both of the 

Glasford. Replaces the Argyle Till Member of the Winnebago Formation in Winnebago, Ogle, and Lee Counties. Thickness is 1 m. Age is 

Pleistocene (Illinoian). 
232 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Orme Spring Conglomerate 

Paleocene and Eocene 

Utah 

Great Basin province 

Meibos, L.C., 1983, Structure and stratigraphy of the Nephi NW 7.5-minute quadrangle, 

Juab County, Utah: Brigham Young University Geology Studies, v. 30, pt. 1, p. 37-58. 

Type section: Exposures in the northeast comer of sec. 31, T. 13 S., 

R. 2 W., Nephi NW 7.5-minute quadrangle, Juab County, Utah. 

Reference localities: sees. 31, 33, and 35, T. 13 S., R. 1 W. Named for 

Orme Spring nearby. 

The Orme Spring Conglomerate, here named, is in the Great Basin 

province, Utah, where it forms rounded knobs and low ledges. Is 

probably an alluvial fan deposit of local extent. Consists of conglomerate 

that has local coarse sandstone lenses. Conglomerate clasts are subangular to subrounded fossiliferous upper Paleozoic limestone, quartz, and 

calcareous sandstone; matrix is medium- to coarse-grained quartz, 

quartzite, chert, and limestone. Unconformably(?) overlies the Red 

Narrows Conglomerate; unconformably underlies the Chicken Creek 

Tuff Member (reduced in rank from formation) of the Goldens Ranch 

Formation. The age of the laterally and temporally equivalent Flagstaff 

Limestone is late Paleocene. Age shown on correlation chart is late 

Paleocene and Eocene. 

Osburger Gulch Sandstone Member of the Hornbrook 

Formation 

late Cretaceous (Cenomanian, Turonian, and Coniacian) 

California, Oregon 

Klamath Mountains province 

Nilsen, T.H., 1984, Tectonics and sedimentation of the Upper Cretaceous Hornbrook 

Formation, Oregon and California, in Crouch, J.K., and Bachman, S.B., eds., 

Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and Mineralogists, Pacific Section, v. 38, p. 101-118. 

Type section: Near the mouth and along the north flank of Osburger 

Gulch, east of the Klamath River and 3.5 km south of the town of 

Hornbrook, SWl/4 sec. 33, T. 47 N., R. 6 W., Hornbrook 15-minute 

quadrangle, Siskiyou County, Calif. 

The Osburger Gulch Sandstone Member of the Hornbrook Formation, here named, is along the northeast margin of the Klamath 

Mountains in Siskiyou County, Calif., and Jackson County, Oreg. 

Consists of gray sandstone containing some conglomerate, siltstone, 

and shale, and represents transgressive shoreline and shelf deposits. 

Conformably overlies the Klamath River Conglomerate Member (new 

name) of the Hornbrook or unconformably overlies pre-Cretaceous 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 233 

basement rocks; conformably underlies the Ditch Creek Siltstone Member (new name) of the Hornbrook. Thickness is 116.5 m at the type 

section and ranges from 75 to 150 m. Age is Late Cretaceous (Cenomanian, Turonian, and early Coniacian) based on mollusks. 

Osgood Bed 

Holocene 

California 

Sierra Nevada province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Osgood Swamp, 0.5 km northwest of U.S. Highway 50 at 

the foot of Myers Grade, near South Lake Tahoe, ElDorado County, 

Calif. 

The Osgood Bed, here named, occurs at Osgood Swamp, California, 

where it overlies the Tsoyawata Bed of the Mazama Member (both new 

names) of the Mount Mazama Formation. Age is Holocene, 6 to 2 ka, 

based on the age of peat underlying the tephra. 

Osito Canyon Shale Member of the Peace Valley Formation 

of the Ridge Basin Group 

Miocene 

California 

Los Angeles basin 

Link, M.H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J.C., and Link, M.H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5--12. 

Type section: Exposures along Osito Canyon adjacent to California 

Highway 99, about 15 km north of Castaic, Los Angeles County, Calif. 

The Osito Canyon Shale Member, here named, is in the Peace Valley 

Formation, redefined, of the Ridge Basin Group in the central Ridge 

basin, Los Angeles County, Calif., where clastic tongues of the Ridge 

Route Formation separate the Peace Valley into five members. Consists of unfossiliferous gray shale, mudstone, and interbeds of siltstone 

and sandstone. Extends laterally for 6,154 m and interfingers with the 

Ridge Route Formation undivided to the northeast and the Violin 

Breccia to the southwest. Conformably overlies the Fisher Spring 

Sandstone Member (new name) and conformably underlies the Frenchman Flat Sandstone Member (new name), both of the Ridge Route. 

Thickness at the type section is 976 m. Age is late Miocene based on its 

stratigraphic position above the marine Castaic Formation and below 

the Cereza Peak Shale Member (n~w name) of the Peace Valley. 
234 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Otter Pond Dioritic Gneiss 

Precambrian 

New York 

Adirondack uplift 

Potter, D.B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: Exposures along the high ridge west of Otter Pond, 

Tupper Lake 15-minute quadrangle, Hamilton County, N.Y. 

The Otter Pond Dioritic Gneiss, here named, is in the Loon Pond 

syncline of the Bog River synclinorium in the Adirondack Highlands, 

Hamilton and St. Lawrence Counties, N.Y., where it is extensively 

distributed throughout the area. Consists of ridge-forming, dark-green, 

massive, foliated to granitic dioritic gneiss, containing plagioclase, 

hornblende, and magnetite, that weathers to a black and white salt and 

pepper texture. Is concordant with surrounding units in most areas or 

cuts them at a low angle. Intrudes the East Charley Pond Gneiss, Bear 

Pond Gneiss, and Lost Pond Marble and its Bog River, Hill 2292, 

Sabattis Road, and Loon Pond Mountain Members (all new names). Age 

is Precambrian. 

Otuk Formation of the Etivluk Group 

Early Triassic to Middle Jurassic 

Alaska 

Arctic Foothills province 

Mull, C.G., Tailleur, I.L., Mayfield, C.F., Ellersieck, Inyo, and Curtis, S., 1982, New 

upper Paleozoic and lower Mesozoic stratigraphic units, central and western Brooks 

Range, Alaska: American Association of Petroleum Geologists Bulletin, v. 66, no. 3, 

p. 348-362. 

Type section: Bluff on the east bank of Otuk Creek, a tributary of the 

East Fork of the Etivluk River, sec. 31, T. 10 S., R. 16 W., western 

Killik River quadrangle, Alaska. Principal reference section designated. 

Subunit: Blankenship Member. 

Rocks previously assigned to the Shublik Formation in the Endicott 

and De Long Mountains are here named the Otuk Formation of the 

Etivluk Group (new name). As here redefined, the Shublik is confined to 

the autochthonous terrane of northern Alaska and the Otuk is confined 

to allochthonous sheets of the central and western Brooks Range. Is 

divided into lower informal shale, chert, and limestone members and 

the Blankenship Member (new name), locally present at the top. 

Lower part consists of brown- or green-weathering, gray chert and 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 235 

nonsiliceous shale, and upper part consists of yellow- to orange-gray, 

rhythmically interbedded chert, siliceous shale, and silicified limestone. 

The Blankenship Member consists of black shale, chert, and limestone. 

Conformably or disconformably overlies the Siksikpuk Formation of the 

Etivluk; disconformably underlies Lower Cretaceous rocks. Thickness 

ranges from 50 to 100m. Age is Early Triassic to Middle Jurassic based 

on fossils. 

Oventop Suite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229--254. 

Type locality: Exposure along Virginia State Road 635, 1 mi west of 

Hume, lat 38°50' N., long 78°02' W., Flint Hill 7.5-minute quadrangle, 

Fauquier County, Va. Named for Oventop Mountain. 

The Oventop Suite, here named, is in the Lovingston massif in the 

Blue Ridge of Virginia. Consists of biotite dioritoid plutonic rocks. Age 

is Middle Proterozoic. 

Owiyukuts Complex 

Archean 

Utah, Colorado 

Uinta uplift 

Sears, J.W., Graff, P.J., and Holden, G.S., 1982, Tectonic evolution oflower Proterozoic 

rocks, Uinta Mountains, Utah and Colorado: Geological Society of America Bulletin, 

v. 93, no. 10, p. 990--997. 

Type area: South flank of 0-Wi-Yu-Kuts Mountain, Uinta Mountains, 

Daggett County, Utah. 

Rocks mapped as Red Creek Quartzite by Hansen (1965) are here 

named the Owiyukuts Complex. Underlies an area less than 3 km2 in the 

Beaver Creek block and also occurs in the Mountain Home, Dutch John, 

and Bender Mountain blocks of the Uinta Mountains in Utah and 

Colorado. Consists of medium- to fine-grained potassium-feldspar-rich 

granitic gneiss, quartzofeldspathic gneiss, garnet gneiss, migmatitic 

gneiss, biotite gneiss, and garnet amphibolite enclosing massive coarsegrained pegmatite bodies. Unconformably underlies the Red Creek 

Quartzite along a shear surface. Age is Archean based on a rubidiumstrontium whole-rock isochron age of 2. 7 Ma for Owiyukuts gneiss. 
236 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Ozaukee Member of the Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Lake Park Section, north of Port Washington Harbor, 

NW1/4SE1/4NE1/4 sec. 28, T. 11 N., R. 22 E., Port Washington East 

7.5-minute quadrangle, Ozaukee County, Wis. Named for Ozaukee 

County. 

Following the informal usage of Acomb (1978), the Ozaukee Member 

is here named the lowermost member of the Kewaunee Formation (new 

name) and occurs in the Lake Michigan Lobe in Ozaukee and Milwaukee 

Counties, Wis. Consists of reddish-brown or pinkish-gray, pebbly, 

clayey, and silty till and associated lake sediments. Overlies the Oak 

Creek Formation (new name); is present at the top of the Lake Michigan 

coastal bluff from Milwaukee to Sheboygan County where it is the 

surface unit. Is equivalent to the Branch River and Silver Cliff Members 

(both new names) of the Kewaunee Formation in the Lake Michigan 

Lobe and the Green Bay Lobe, respectively. Thickness ranges from 2.4 

m to 20 m. Age is Pleistocene (late Wisconsinan). 

Padden Member of the Chuckanut Formation 

Eocene 

Washington 

Bellingham basin 

Johnson, S.Y., 1984, Stratigraphy, age, and paleogeography of the Eocene Chuckanut 

Fonnation, northwest Washington: Canadian Journal of Earth Sciences, v. 21, no. 1, 

p. 92-106. 

Type section: Composite of outcrops along Bellingham Bay, on the south 

and north limbs of the Chuckanut syncline, sec. 25 and W1/2 sec. 13, 

T. 37 N., R. 2 E., Whatcom County, Wash. Named for Lake Padden. 

The Padden Member, here named, is in the Chuckanut Formation in 

the Bellingham Bay area on the mainland and is on Lummi and Sucia 

Islands, in the largest outcrop belt of the Chuckanut, which extends 

from the San Juan Islands into the North Cascades, Wash. Consists of 

alternating medium- to coarse-grained, cross bedded sandstone, massive 

to crudely stratified conglomerate, and mudstone containing minor 

amounts of coal. Represents braided river and flood-plain deposits. 

Conformably overlies the Bellingham Bay and Governors Point Members (both new names) of the Chuckanut, or unconformably overlies 

pre-Tertiary rocks in the western part of the outcrop belt; interfingers 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 237 

with the Slide Member and underlies the Maple Falls Member (both 

new names) of the Chuckanut. On Sucia Island strata of the Padden 

Member, formerly assigned to the Nanaimo Group, are in fault contact 

with the N anaimo. Thickness is 680 m at the type section; total 

thickness may exceed 3,000 m. Age is middle to late Eocene based on 

zircon fission-track ages and pollen. 

Palisades-Kepler Member of the Scotch Grove Formation 

Early Silurian (Wenlockian) 

Iowa 

Iowa shelf 

Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River fault zone and 

the structural and stratigraphic framework of eastern Iowa: Iowa Geological Survey 

Technical Information Series 13, 126 p. 

Type locality: Exposures extending along the banks of the Cedar River 

for 1.6 mi in Palisades-Kepler State Park, El/2SWI/4 and SWV4NEV4 sec. 

4, T. 82 N., R. 6 W., Linn County, Iowa. 

Horizontally bedded, nonlaminated strata called the informal 

Palisades-Kepler Mound facies by Witzke (1981), included within the 

LeClair facies of the Gower Formation by previous workers, are here 

named the Palisades-Kepler Member of the Scotch Grove Formation 

(new name) in eastern Iowa. Consists of crinoidal skeletal-moldic and 

skeletal-replaced dolomite containing wackestone, packstone, and rare 

grainstone fabrics, characterized by mounded carbonate reefs, including 

single mounds that range in size from 200 to 300 ft laterally and from 30 

to 200 ft vertically, and coalesced complexes of mounds. Base of the 

member has not been observed; extends laterally into strata of the Buck 

Creek Quarry, Waubeek, and Fawn Creek Members (all new names) of 

the Scotch Grove; sharply underlies the Anamosa Member or Brady 

Member (new name) of the Gower Formation. Age is Early Silurian 

(early and middle Wenlockian). 

Palmer Creek Member of the Canton Formation 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

German, J.M., 1985, The geology of the northeastern portion of the Dahlonega gold belt: 

Georgia Geologic Survey Bulletin 100, p. 1-41. 

Type locality: Exposures along Palmer Creek near Dawsonville, Dawsonville 7.5-minute quadrangle, Dawson County, Ga. 

The Palmer Creek Member of the Canton Formation, here named in 

the Dahlonega area, Georgia, was previously mapped as the Carolina 

Gneiss by Keith (1909). Consists of biotite-quartz schist containing 
238 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

hornblende or garnet. The boundary between the Palmer Creek and the 

underlying Proctor Creek Member (new name) of the Canton is gradational at the lowest occurrence of biotite-quartz schist. Is in fault contact 

with the overlying Chestatee Member (new name) of the Canton at the 

first occurrence of inter layered felsic gneiss and amphibolite. Where the 

Chestatee Member is absent the Palmer Creek grades into the Helen 

Member (new name) of the Canton at the first occurrence of biotiteplagioclase-quartz gneiss. Age is Late Proterozoic and (or) early 

Paleozoic. 

Pan Tak Granite 

Tertiary 

Arizona 

Basin and Range province 

Wright, J.E., and Haxel, Gordon, 1982, A garnet-two-mica granite, Coyote Mountains, 

southern Arizona: Geologic setting, uranium-lead isotopic systematics of zircon, and 

nature of the granite source region: Geological Society of America Bulletin, v. 93, no. 

11, p. 1176-1188. 

Type area: Northern part of the Coyote Mountains, Baboquivari Peak 

quadrangle, Pima County, Ariz. Named for the town of Pan Tak, Pima 

County. 

The Pan Tak Granite, here named, occurs in the Coyote Mountains, 

southern Papago Indian Reservation, south-central Arizona. Granite of 

the pluton consists of two phases: an older phase of reddish-weathering, 

medium-grained, leucocratic, biotite and muscovite-biotite granite 

intruded by a younger phase of white- to pinkish- or orangish-grayweathering, medium-grained, leucocratic, garnet-muscovite and 

garnet-biotite granite and associated pegmatite dikes. Granite was 

generated by the melting of late Precambrian crystalline basement 

during latest Cretaceous and early Tertiary crustal thrust faulting. 

Intrudes Paleozoic metasedimentary rocks and Jurassic plutonic rocks. 

Age is early Tertiary based on a uranium-lead isotopic age of 58 Ma. 

Panther Bluff Formation of the Great Smoky Group 

Late Proterozoic 

Georgia, Tennessee 

Piedmont-Blue Ridge province, Appalachian basin 

Gair, J.E., and Slack, J.F., 1982, Geologic maps of the Cohutta Wilderness and the Hemp 

Top Roadless Area, northern Georgia and southeastern Tennessee: U.S. Geological 

Survey Miscellaneous Field Studies Map MF-1415-A, scale 1:48,000. 

Type locality: Panther Bluff in the south-central part of the Cohutta 

Wilderness, lat 34°54' N., long 84°36' W., Hemp Top 7.5-minute 

quadrangle, Fannin County, Ga. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 239 

The Panther Bluff Formation, here named, is the lower unit of the 

Great Smoky Group in the Cohutta Wilderness and Hemp Top Roadless 

Area, Ga., and Tenn. Consists of quartzose, feldspathic, and micaceous 

metasandstone and metawacke containing minor amounts of metashale 

and metaconglomerate. Is in fault contact with rocks of the underlying 

Snowbird Group; conformably underlies the lower part of the Boyd Gap 

Formation of the Great Smoky Group. Maximum thickness is 2,000 ft. 

Age is Late Proterozoic. 

Paradise Granodiorite 

Late Cretaceous 

California 

San Joaquin basin 

Moore, J.G., 1981, Geologic map of the Mount Whitney quadrangle, Inyo and Tulare 

Counties, California: U.S. Geological Survey Geologic Quadrangle Map GQ-1545, scale 

1:62,500. 

Type locality: Exposures on the east side of Paradise Valley, eastcentral Marion Peak 15-minute quadrangle, Fresno County, Calif. 

The Paradise-Whitney nested sequence extends 83 km southeastward from the central part of the Marion Peak quadrangle on the 

northwest, through the Mount Whitney quadrangle, to the southeastern part of the Olancha quadrangle on the southeast in Inyo, Tulare, and 

Fresno Counties, Calif. Includes the Paradise pluton, here named the 

Paradise Granodiorite, and the Whitney pluton, named the Whitney 

Granodiorite (new name). Consists of porphyritic granodiorite and 

granite that have potassium-feldspar phenocrysts characterized by 

zonally arranged inclusions of biotite and hornblende. The ParadiseWhitney nested sequence was emplaced as a single intrusion about 85 

Ma, but before complete solidification occurred, the partly molten and 

more differentiated central Whitney Granodiorite core burst through 

the solidified wall of the Paradise Granodiorite on the southeast side. 

Western and eastern contacts of the Whitney dip under the Paradise 

and its axis plunges north beneath the Paradise. Age is Late Cretaceous 

based on potassium-argon biotite and hornblende ages of 78 and 84 Ma 

and a uranium-lead age of 86 Ma. 

Paradise Fork Formation 

Silurian (Llandoverian and Wenlockian) 

Alaska 

Holitna basin 

Dutro, J.T., Jr., and Patton, W.W., Jr., 1982, New Paleozoic formations in the northern 

Kuskokwim Mountains, west-central Alaska: U.S. Geological Survey Bulletin 1529-H, 

p. H13-H22. 
240 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type locality: Low hills between upper Paradise Fork and upper 

Sulukna River drainages, sees. 11, 12, 14, and 23, T. 19 S., R. 26 E., 

Medfra (D-2) quadrangle, Alaska. 

The Paradise Fork Formation, here named, is mapped in the 

northern part of the Nixon Fork terrane of the Kuskokwim Mountains, 

Alaska, where it was deposited in a shallow-water carbonate environment. Consists of dark-gray, platy, silty limestone and interbedded 

black silt shale containing isolated limestone lenses in the upper part of 

the sequence. Disconformably(?) overlies the Telsitna Formation (new 

name); underlies the Whirlwind Creek Formation (new name). 

Is terminated by a major northwest-trending vertical fault at 

White Mountain Creek. Thickness is a minimum of 1,000 m. Age is 

Silurian (latest Llandoverian and Wenlockian) based on graptolites and 

ostracodes. 

Paradise Ranch Shale Member of the Peace Valley Formation 

of the Ridge Basin Group 

Miocene 

California 

Los Angeles basin 

Link, M.H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J.C., and Link, M.H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5-12. 

Type section: Exposure along the east side of Interstate Highway I -5 

from Templin Highway north to Three Mile Grade, 9 km north of 

Castaic, Los Angeles County, Calif. Named for Paradise Ranch on the 

west side of Highway I -5. 

The Paradise Ranch Shale Member, here named, is in the Peace 

Valley Formation, redefined, of the Ridge Basin Group in the central 

Ridge basin, Los Angeles County, Calif. Is the lowest member of the 

Peace Valley, which is separated into five members by clastic tongues of 

the Ridge Route Formation. Consists of poorly exposed dark-gray, 

unfossiliferous shale containing thin interbeds of sandstone. Extends 

laterally for 5, 625 m and interfingers with the Violin Breccia to the 

southwest and the Ridge Route Formation undivided to the northeast. 

Conformably overlies the Marple Canyon Sandstone Member (new 

name) and conformably underlies the Fisher Spring Sandstone Member 

(new name), both of the Ridge Route Formation. Thickness is 549 m at 

the type section. Age is late Miocene based on its stratigraphic position 

above the marine Castaic Formation and the Marple Canyon Sandstone 

Member of the Ridge Route. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 241 

Paradox Lake Formation of the Lake George Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: None designated. Occurs in the eastern Adirondack 

Mountains, N.Y. Source of name not stated. 

The name Paradox Lake Formation, used by Walton and deWaard 

(1963), is here assigned to the Lake George Group (new name) in the 

eastern Adirondack Mountains, N.Y. Consists of calcitic and dolomitic 

marble interlayered with amphibolite, quartzite, gneiss, schist, and 

granulite, some of which are locally mappable units. Overlies the Eagle 

Lake Gneiss (new name) of the Lake George Group or rocks of the 

Piseco Group (new name); underlies the Treadway Mountain Formation 

(new name) of the Lake George Group. Correlates with the Cedar River 

Formation of the Lake George Group and the Cranberry Lake Formation (new name) and Gouverneur Marble, both of the Oswegatchie 

Group, in other parts of the Adirondacks. Age is Proterozoic. [Although 

this name has not been formally proposed, it is included here because of 

its continued usage.] 

Paragon Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R. 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Roadcuts along the western side of Kentucky Highway 

1274, 1.1 km north of the Licking River (Cave Run Lake), Bangor 

quadrangle, Rowan County, Ky. Named for the community of Paragon, 

5. 6 km east of the type section. 

Strata of the Paragon Formation, here named, were previously 

assigned to the Pennington Formation or Newman Limestone, which 

are now restricted from the Cumberland Escarpment outcrop belt in 

Kentucky. The Paragon occurs throughout the outcrop belt south of 

Greenup County southward to an arbitrary cutoff against the Pennington at the southern border of Kentucky. Consists of a sequence of shale, 

dolostone, and limestone divided into a lower dark shale member, a 

clastic or dolomite member, a limestone member, and an upper shale 
242 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

member. Conformably overlies or intertongues with the Poppin Rock 

Member (new name) of the Slade Formation (new name) or the Bangor 

Limestone; disconformably underlies Pennsylvanian units. Thickness 

ranges from 0 to 60 m. Age is Late Mississippian. 

Parr Branch Formation of the Snowbird Group of the Ocoee 

Supergroup 

Middle Proterozoic 

Georgia 

Appalachian basin 

McConnell, K.I., and Costello, J.O., 1984, Basement-cover rock relationships along the 

western edge of the Blue Ridge thrust sheet in Georgia: Geological Society of America 

Special Paper 194, p. 263-280. 

Type locality: None designated. Occurs near Fort Mountain State Park, 

Murray County, Ga. Origin of name not stated. 

The Parr Branch Formation of the Snowbird Group of the Ocoee 

Supergroup, here named, is in a small unnamed anticlinorium of 

Grenville-age basement rocks located along the western margin of the 

Blue Ridge thrust sheet in the Fort Mountain area of north-central 

Georgia. Consists of metamorphosed coarse, bouldery conglomerate 

derived from the nonconformably underlying Fort Mountain Gneiss. 

Conformably underlies the Wilhite Formation of the Walden Creek 

Group. Is the lithostratigraphic equivalent of the Pinelog Formation of 

the Snowbird Group in the Salem Church anticlinorium to the south. 

Age is Middle Proterozoic. 

Patterson Lake Member of the Virginian Ridge Formation 

Cretaceous (Aptian and Albian) 

Washington 

Northern Cascade Range-Okanogan province 

Trexler, J.H., Jr., 1985, Sedimentology and stratigraphy of the Cretaceous Virginian 

Ridge Formation, Methow Basin, Washington: Canadian Journal of Earth Sciences, v. 

22, no. 9, p. 1274-1285. 

Type section: Exposures on hillside east of Patterson Lake, 4.8 km 

southwest of Winthrop in the southern Methow Basin, sec. 8, T. 34 N., 

R. 21 E., Okanogan County, Wash. 

The Patterson Lake Member of the Virginian Ridge Formation, 

here named, occurs in a narrow belt in the southern part of the Methow 

Basin, the southernmost of a series of Mesozoic basins that rest with 

angular unconformity on older rocks in north-central Washington. 

Consists of braided stream deposits of massive, crudely stratified 

conglomerate and irregular, lenticular beds of coarse sandstone in the 

lower 100 m; massive to thick-bedded sandstone and conglomerate 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 243 

representing fluvial deposits of gentler gradient in the middle 250 m; 

and thickly bedded, fossiliferous marine sandstone in the upper 100 m. 

Unconformably overlies the Newby Group; interfingers laterally with 

and gradationally underlies the Slate Peak Member (new name) of the 

Virginian Ridge Formation. Thickness at the type section is about 450 

m. Age is Cretaceous (Aptian and Albian) based on fossils. 

Payne Cliffs Formation 

Eocene 

Oregon 

Klamath Mountains province 

McKnight, B.K., 1984, Stratigraphy and sedimentology of the Payne Cliffs Formation, 

southwestern Oregon, in Nilsen, T.H., ed., Geology of the Upper Cretaceous Hornbrook Formation: Society of Economic Paleontologists and Mineralogists, Pacific 

Section, v. 42, p. 187-194. 

Type section: Exposures near Payne Cliffs, 4.5 km northwest of 

Phoenix, Bear Creek valley, Klamath Mountains, Jackson County, 

Oreg. 

The Payne Cliffs Formation, here named, was informally named by 

McKnight (1971) and was previously mapped as the Umpqua Formation 

by Wells (1956). Is exposed along the northeast margin of the Klamath 

Mountains in the Medford-Ashland area of southwest Oregon and 

represents braided-stream deposits and fining-upward sequences of 

conglomerate and sandstone derived from the Klamath Mountains. 

Consists of informal Unit 1, a basal conglomerate unit of crudely bedded 

gravel and sand, 160 m thick, and Unit 2, an upper sandstone unit, 

containing conglomerate lenses, 2,150 m thick. Unconformably overlies 

the Late Cretaceous Hornbrook Formation; unconformably underlies 

volcanic and volcaniclastic rocks of the Cascade Range. Thickness at the 

type section is 27 m. Minimum age is late Eocene based on fossil leaves. 

Peaks of Otter Suite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Exposures at the Peaks of Otter, lat 37~7' N., long 

79°35' W., Peaks of Otter 7.5-minute quadrangle, Bedford County, Va. 

The Peaks of Otter Suite, here named, is in the Pedlar massif in the 

Blue Ridge of Virginia. Typical exposures of mesocharnockite are found 

in the Peaks of Otter and Montvale quadrangles. Age is Middle 

Proterozoic. 
244 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Pedlar River Charnockite Suite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Sinha, A.K., and Bartholomew, M.J., 1984, Evolution of the Grenville terrane in the 

central Virginia Appalachians: Geological Society of America Special Paper 194, 

p. 175-186. 

Type section: Outcrop 400 m S. 10° W. of Hog Camp Gap where the 

Appalachian Trail reaches the crest of Cole Mountain, lat 37°45'30" N., 

long 79°11'30" W., Montebello 7.5-minute quadrangle, Rockbridge 

County, Va. Named for the Pedlar River. 

The Pedlar River Charnockite Suite, here named in the Pedlar 

massif in Virginia, consists of coarse-grained massive and foliated 

charnockites containing quartz, perthite, plagioclase, hypersthene, and 

ilmenite showing evidence of ductile deformation and mylonitization. 

Intrudes the Lady Slipper Granulite Gneiss (new name). Age is Middle 

Proterozoic based on a concordia intercept age of 1, 075 Ma. 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

The Pedlar River Charnockite Suite, previously named the Pedlar 

River pluton by Bartholomew and others (1981), includes four main rock 

types: granite, leucocharnockite, mesocharnockite, and the informal 

Vesuvius mega porphyry, which crops out along Virginia Highway 56 

about 2 mi east of the town of Vesuvius, Rockbridge County, Va. The 

Pedlar River intrudes the basal Nellysford Granulite Gneiss (new name) 

and the Lady Slipper Granulite Gneiss (new name). 

Pelham Bay Member of the Hartland Formation of the 

Hutchinson River Group 

Late Cambrian and Early Ordovician 

New York 

New England province 

Baskerville, C.A., 1982, Adoption of the Hutchinson River Group and its subdivisions in 

Bronx and Westchester Counties, southeastern New York: U.S. Geological Survey 

Bulletin 1529-H, p. H1-H10. 

Type locality: Outcrops in Pelham Bay Park, Flushing 7.5-minute 

quadrangle, Bronx County, N.Y. 

The Pelham Bay Member, here named, of the Hartland Formation 

of the Hutchinson River Group (new name) is exposed in the Long 

Island Sound area of New York but may extend beneath the sound off 

the Connecticut coast. Consists of interbedded amphibolites, gneisses, 

and schists of very high metamorphic grade, granulite, and pegmatite. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 245 

Maximum thickness is 1,500 m. Age is probably Late Cambrian and 

Early Ordovician based on a potassium-argon age of 380 Ma. 

Pelican Island Bed of the Pyramid Lake Member of the 

Mount Mazama Formation 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Measured section 4 of Morrison (1964), southeast of 

Pelican Island, 3.6 km east of Timber Lake, Churchill County, Nev. 

The Pelican Island Bed, here named, is the lowermost of five beds of 

tephra in the Pyramid Lake Member (new name) of the Mount Mazama 

Formation. Consists of very fine grained, ashy parting and is more 

potassium-rich than the Timber Lake Bed (new name), the next higher 

bed in the Pyramid Lake Member. Interfingers with the lower member 

of the Sehoo Formation. Overlies the Marble Bluff Bed (new name) and 

underlies the Carson Sink Bed (new name) of the Mono Basin Formation 

(new name). Age is Pleistocene, 35-11.5 ka. 

Perkins Bluff Member of the Rhems Formation of the Black 

Mingo Group 

Paleocene (Danian, Midwayan) 

South Carolina 

Atlantic Coast basin 

Van Nieuwenhuise, D.S., and Colquhoun, D.J., 1982, The Paleocene-lower Eocene Black 

Mingo Group of the east central Coastal Plain of South Carolina: South Carolina 

Geology, v. 26, no. 2, p. 47-67. 

Type section: Exposures along Perkins Bluff on the Black River, 

Georgetown County, S.C. 

The Perkins Bluff Member, here named, is the upper member of the 

Rhems Formation of the Black Mingo Group in the Coastal Plain of 

South Carolina. The revised Black Mingo Group includes all the strata 

from the base of the Paleocene to the unconformity at the top of the 

Ypresian Stage of the Eocene and is divided into the Rhems Formation 

of the Danian Stage, the Williamsburg Formation of the Thanetian 

Stage, and unnamed Ypresian strata. [In the Clubhouse Crossroads 

corehole Number 1, Gohn and others (1978) assigned the entire Paleocene section to the Black Mingo Formation, and Gohn and others (1983) 

named the Ypresian section the Fishburne Formation (new name).] The 

Perkins Bluff Member consists of imbricated, pelecypod-rich, partly 

silicified, argillaceous sand forming a prominent ridge that extends 
246 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

along the Black River and overhangs the Browns Ferry Member (new 

name) of the Rhems. Unconformably overlies the Browns Ferry Member with sharp erosional contact; unconformably underlies the Lower 

Bridge Member (new name) of the Williamsburg Formation. Thickness 

at the type section is 10 ft. Age is Paleocene (late Danian, middle 

Midwayan). 

Pettus Lake Member of the Fort Rock Formation 

Pliocene 

Oregon 

Southern Oregon basin 

Colbath, G.K., and Steele, M.J., 1982, The geology of economically significant lower 

Pliocene diatomites in the Fort Rock basin near Christmas Valley, Lake County, 

Oregon: Oregon Geology, v. 44, no. 10, p. 111-118. 

Type section: Exposure west of Seven Mile Ridge and Pettus Lake, 

SEV4NWV4 sec. 5, T. 28 S., R. 17 E., Lake County, Ore. 

The Pettus Lake Member of the Fort Rock Formation, here named, 

occurs in the Fort Rock basin, Oregon. Includes the diatomitedominated rocks of the informal tuffaceous sandstone and siltstone, tuff, 

and diatomite unit Tst, mapped by Walker and others (1967); the 

remainder of unit Tst is grouped with their palagonitic tuff unit QTps, 

here referred to informally as the volcaniclastic rocks of Seven Mile 

Ridge and Table Rock. Consists of white, pale-orange, or pale-gray, 

thick-bedded diatomite containing irregularly spaced tabular interbeds 

of volcanic ash and pumice. Overlies the Picture Rock Basalt; conformably underlies and is interbedded with volcaniclastic breccia of Seven 

Mile Ridge. Thickness is about 4 mat the type section and about 91 m 

in the central part of the Fort Rock basin. Age is early Pliocene based 

on diatoms. 

Pflugerville Formation of the Austin Group 

Late Cretaceous 

Texas 

Ouachita tectonic belt province 

Garner, L.E., and Young, K.P., 1976, Environmental geology of the Austin area-An aid 

to urban planning: Texas Bureau of Economic Geology Report of Investigations 86, 

39 p. 

Type locality: None designated. Named for the town of Pflugerville, 

Travis County, Tex. 

The Pflugerville Formation, here named, is in the Austin Group and 

occurs in the Austin, Tex., area. Consists of light-gray, chalky, clayey 

limestone containing hard limestone beds at the base and top. Overlies 

the Burditt Formation of the Austin; is equivalent to the McKown 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 247 

Formation (new name) of the Austin, a beach rock facies; underlies the 

Sprinkle Formation of the Taylor Group. Thickness is 40 ft. Age is Late 

Cretaceous. 

Pharaoh Mountain Gneiss of the Piseco Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: Exposures on Pharaoh Mountain, on the east side of 

Schroon Lake, and in woods on the east side of the town road north from 

Adirondack toward Schroon Lake Village, Paradox Lake quadrangle, 

Essex County, N.Y. 

Interlayered charnockitic and granitic gneisses in large domical 

massifs are here named the Pharaoh Mountain Gneiss, the basal unit of 

the Piseco Group (new name) in the Adirondack Mountains in New 

York. Underlies the Brant Lake Gneiss of the Piseco Group in the 

central and eastern Adirondacks, the Alexandria Bay Gneiss (new 

name) of the Piseco in the Northwest Lowlands, and leucogranitic 

gneiss in the western Adirondack Highlands. Age is Proterozoic. 

Phelan Formation 

Pliocene and Pleistocene 

California 

Mohave basin 

Weldon, Ray, 1984, Implications of the age and distribution of the late Cenozoic 

stratigraphy in Cajon Pass, southern California, in San Andreas fault, Cajon Pass to 

Wrightwood: American Association of Petroleum Geologists, Pacific Section, and Los 

Angeles Basin Geological Society volume and guidebook 55, p. 9-16. 

Type locality: None designated. Exposed southwest of Phelan Peak, 

about 5 km northeast of Wrightwood, western San Bernardino Mountains, San Bernardino County, Calif. 

Magnetic stratigraphy demonstrates that the Crowder Formation in 

the Cajon Pass area of the San Bernardino Mountains, Calif., is 

Miocene. A younger unit to the west, formed as a narrow northwest 

trending basin parallel to and north of the San Andreas fault, that had 

previously been included in the Crowder as the western Crowder of 

Foster (1980), is here removed from the Crowder and named the Phelan 

Formation. Consists of tuff, sand, and gravel, and crops out over an 

area of 50 km2 • Overlies the Punchbowl and Crowder Formations; 
248 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

underlies the Harold Formation of the Victorville Fan sequence. Age is 

Pliocene and Pleistocene, 4.2 to 0.9 Ma, based on magnetic polarity 

stratigraphy. 

Picture Rock Member of the Hopkinton Dolomite 

Early Silurian (Llandoverian, Telychian) 

Iowa 

Iowa shelf 

Johnson, M.E., 1983, New member names for the Lower Silurian Hopkinton Dolomite of 

eastern Iowa: Iowa Academy of Science Proceedings, v. 90, no. 1, p. 13-18. 

Type section: Exposures in natural bluffs along the Maquoketa River in 

Picture Rock Park, SEl/4SWl/4 sec. 32, T. 86 N., R. 2 W., Jones County, 

Iowa. 

Previously divided on the basis of paleontologic units, the Hopkinton 

Dolomite is here divided into lithologic members to facilitate interregional correlations based on sea-level curves. Rocks formerly called 

the Favosites Beds of the Hopkinton are here named the Picture Rock 

Member of the Hopkinton Dolomite in eastern Iowa. Consists of tan to 

brown, very thick bedded or massive, medium crystalline, highly vuggy 

dolomite that has abundant tabulate coral colonies. Overlies the Farmers Creek Member (new name) of the Hopkinton; underlies the Johns 

Creek Quarry Member (new name) of the Hopkinton. Thickness at the 

type section ranges from 10.75 to 11.50 m. Age is Early Silurian 

(Llandoverian, Telychian). 

Pierce Formation 

Pleistocene (pre-Illinoian) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: West side of abandoned gravel pit, north of Highway 12, 

1.0 km southwest of Hersey, SWl/4SEl/4SEl/4 sec. 29, T. 29 N., R. 15 W., 

Wilson 7.5-minute quadrangle, St. Croix County, Wis. Named for 

Pierce County. 

Subunits: Hersey Member, Kinnickinnic Member. 

The Pierce Formation, here named, occurs in Pierce, St. Croix, 

Dunn, Pepin, and Buffalo Counties, Wis. Includes the lower Hersey 

Member (new name) and the upper Kinnickinnic Member (new name). 

Consists of gray calcareous till and associated yellowish-brown sand and 

gravel and laminated silt and clay of glacial lacustrine origin. Basal 

contact is unknown except where it overlies Paleozoic bedrock; sharply 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 249 

underlies the River Falls Formation (new name) in northern Pierce and 

St. Croix Counties, elsewhere it is the surficial unit. Thickness ranges 

from less than 1 m to 55 m. Age is Pleistocene (pre-Illinoian). 

Pilgrim Conglomerate Member of the Colter Formation 

Miocene 

Wyoming 

Yellowstone province 

Barnosky, A.D., 1984, The Colter Formation-Evidence for Miocene volcanism in 

Jackson Hole, Teton County, Wyoming: Wyoming Geological Association, Earth 

Science Bulletin, v. 17, p. 49-97. 

Type section: Exposures along Pilgrim Creek (the upper part of the 

Colter Formation type section), Two Ocean Lake 7.5-minute quadrangle, Teton County, Wyo. 

The Pilgrim Conglomerate Member is here named the upper member of the Colter Formation and is exposed at Pilgrim Creek, Two 

Ocean Lake, Cunningham Hill, Shadow Mountain, and Ditch Creek, 

Teton County, Wyo. The major vent area for the member was a few 

kilometers northwest of Pilgrim Mountain. Consists of pink rhyolitic 

tuff, ignimbrite, and conglomerate, and differs from the underlying 

Crater Tuff Breccia Member (new name) of the Colter by the occurrence 

of conglomerate, sandstone, and claystone, its pink, white, blue-gray, 

tan-gray, or green color, the presence of angular to sub rounded volcanic 

clasts, and the frequent occurrence of rounded quartz cobbles. Is older 

than the Huckleberry Ridge Tuff. Thickness is 1,000 m. Was deposited 

between 13 and 9.4 Ma during later Miocene volcanism. 

Pilot Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Outcrops behind the Pilot Community Center, Pilot 

7.5-minute quadrangle, Montgomery County, Va. 

The Pilot Gneiss, here named in the Pedlar massif in the Virginia 

Blue Ridge, is an intrusive leucogranulite gneiss containing small 

hornblende granitoid bodies. Age is Middle Proterozoic. 
250 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Piney Branch Complex 

late Proterozoic and (or) Early Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., and Morgan, B.A., 1981, The Piney Branch Complex-A metamorphosed fragment of the Central Appalachian ophiolite in northern Virginia: American 

Journal of Science, v. 281, no. 4, p. 484-508. 

Type locality: Exposures along Piney Branch between Robeys Mill and 

a point about 300 m north of Braddock Road, Fairfax 7.5-minute 

quadrangle, Fairfax County, Va. 

The Piney Branch Complex, here named, crops out over an area of 

9 km2 for a length of 18 km from Oakton to near Yorkshire in Fairfax 

County, V a. Is a tectonic melange resulting from the deformation of a 

layered complex that contained repetitive cycles of ultramafic and mafic 

rocks that are now metamorphosed to serpentinite, soapstone, actinolite schist, and metagabbro. Is intruded by dikes and sheets of plagiogranite. A discontinuous underlying border of precursory ophiolitic 

melange, the Yorkshire Formation (new name), which is thought to 

record the first movement of the allochthonous Piney Branch slab. The 

allochthon consisting of the Piney Branch and Yorkshire was thrust 

upon the Peters Creek Schist and, together with it, forms a composite 

allochthon that was emplaced on the Sykesville Formation, perhaps by 

gravity sliding. Unconformably underlies the Popes Head Formation 

(new name). Movement of the Piney Branch began in the Late Proterozoic after the metamorphism of the Peters Creek and ended during the 

Taconic orogeny. Age is Late Proterozoic and (or) Early Cambrian. 

Pippins Cemetery Formation 

Holocene 

Missouri 

Ozark uplift 

Haynes, C. V., Jr., 1985, Mastodon-bearing springs and late Quaternary geochronology of 

the lower Pomme de Terre valley, Missouri: Geological Society of America Special 

Paper 204, 35 p. 

Type locality: None designated. Probably named for Pippins family 

cemetery, spelled Pippens on the Fristoe 15-minute quadrangle map, 

Benton and Hickory Counties, Mo. 

The historic flood plain T -0 of the Pomme de Terre River, Benton 

and Hickory Counties, Mo., is here named the Pippins Cemetery 

Formation. This unit was called the informal Pippens formation by 

Brakenridge (1981). Consists of a compound, 4- to 6-m-thick terrace of 

two cut-and-fill deposits of gray silt or silty fine sand over brown chert 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 251 

pebble gravel. Unconformably overlies the Breshears Valley Formation 

(new name). Age is Holocene based on radiocarbon dates of 0.84 and 

0.43±0.1 ka. 

Piseco Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type area: Exposures in the Piseco dome near Piseco Lake, Hamilton 

County, N.Y. 

Subunits: Pharaoh Mountain Gneiss, Brant Lake Gneiss, Alexandria 

Bay Gneiss. 

Basement rocks of the Adirondack Mountains, N.Y., consisting of 

interlayered charnockitic, granitic, and leucogranitic gneisses, are here 

named the Piseco Group. Includes the basal Pharaoh Mountain Gneiss 

(new name), which is overlain by the Brant Lake Gneiss in the central 

and eastern Adirondacks, by leucogranitic gneiss in the western 

Adirondack Highlands, and by the Alexandria Bay Gneiss (new name) 

in the Northwest Lowlands. Basal quartzofeldspathic gneiss is the only 

unit of the Piseco Group in the southern Adirondacks. Unconformably 

underlies metasedimentary rocks of the Oswegatchie Group in the 

Northwest Lowlands and the Lake George Group (new name) in the 

central, eastern, and southern Adirondacks. Regional metamorphism 

occurred during the Grenville orogeny. Age is Proterozoic. 

Pleasant Lake Gneiss of the Oswegatchie Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: Exposures in and around Pleasant Lake and Rossie, St. 

Lawrence County, N.Y. 

Gray hornblende-biotite-quartz-plagioclase gneiss and basal quartzite, previously named the Major Gneiss by Lewis (1969), are here 

named the Pleasant Lake Gneiss of the Oswegatchie Group in 

the Northwest Lowlands of the Adirondacks, N.Y. Overlies the Gouverneur Marble of the Oswegatchie; correlates with the Treadway 
252 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Mountain Formation of the Lake George Group (both new names) in 

the eastern Adirondacks. Maximum thickness is 1,050 m. Age is 

Proterozoic. 

Pleasant Mills Formation of the Salina Group 

Middle Silurian 

Indiana 

Cincinnati arch 

Droste, J.B., and Shaver, R.H., 1982, The Salina Group (Middle and Upper Silurian) of 

Indiana: Indiana Geological Survey, Special Report 24, 41 p. 

Type section: Meshberger Brothers Stone Corporation quarry, 3 mi 

south of Pleasant Mills, center sec. 4, T. 26 N., R. 15 E., Adams 

County, Ind. 

Subunit: Limberlost Dolomite Member. 

The Pleasant Mills Formation of the Salina Group, here named, 

includes all Silurian rocks that lie above the Salamonie Dolomite and 

below the Wabash Formation in central and northern Indiana northeast 

of the defined limit of the Salina Group. In the area within and south of 

the Fort Wayne Bank, the formation includes the Limberlost Dolomite 

Member, here reduced from formation rank, and overlying rocks 

formerly assigned to the Waldron and Louisville Formations, which are, 

in this area, interbedded and lacking typical lithologies. North of the 

Fort Wayne Bank the Limberlost Dolomite Member may be identified 

wherever an upper contact is provided by a recognizable Waldron 

equivalent. The formation has an arbitrary cutoff on the southeast at 

the Limberlost depositional limit; the Waldron and Louisville retain 

their formational status south of this limit. The Pleasant Mills consists 

of medium- to dark-brown, fine-grained dolomite containing nodular 

chert, and lighter brown, more granular, porous dolomite. A reef facies 

near the Fort Wayne Bank is termed the Huntington lithofacies. Two 

major depositional cyclic sequences are recognized. Thickness ranges 

from 0 to 300ft. Age is Middle Silurian (Niagaran). 

Ponderosa Way Member of the Chico Formation 

Late Cretaceous (Coniacian) 

California 

Sacramento basin 

Haggart, J.W., and Ward, P.D., 1984, Late Cretaceous (Santonian-Campanian) stratigraphy of the northern Sacramento Valley, California: Geological Society of America 

Bulletin, v. 95, no. 5, p. 618-627. 

Type section: Exposures on Big Chico Creek near Ponderosa Way 

Bridge, sec. 1, T. 23 N., R. 2 E., Butte County, Calif. Named for the 

foothills road, Ponderosa Way. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 253 

The Ponderosa Way Member, informally named by Saul (1961), is 

here named the basal unit of the Chico Formation along Butte, Big 

Chico, and Deer Creeks in Butte and Tehama Counties, eastern 

Sacramento Valley, Calif. Consists of poorly sorted and moderately well 

rounded cobble conglomerate containing local sand lenses in the lower 

part; the upper parts become increasingly sandy through interbedding 

of sandstone lenses within the conglomerate. Unconformably overlies 

pre-Cretaceous metamorphic rocks; conformably underlies the Musty 

Buck Member (new name) of the Chico. Thickness is 200m. Age is Late 

Cretaceous based on Coniacian ammonites in the upper part of the 

Ponderosa Way Member. 

Pond Ridge Rhyolite of the St. Francois Mountains Volcanic 

Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: NElf4NWlf4 sec. 3, T. 33 N., R. 3 E., Ironton quadrangle, 

Iron County, Mo. Exposed at Shepherd Mountain Lake dam on Pond 

Ridge. 

Rocks previously mapped as the upper part of the Cedar Bluff felsite 

or undifferentiated felsite by Anderson (1962, 1970) are here named the 

Pond Ridge Rhyolite in the western St. Francois Mountains in southeast Missouri. Consists of dark-maroon to grayish ash-flow tuff containing white to pinkish feldspar phenocrysts, quartz phenocrysts, and 

large reddish fiamme. Overlies the Cedar Bluff Rhyolite (new name); 

underlies the Buck Mountain Shut-ins Formation (new name). Thickness is 130 m. Age is Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E. B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Pond Ridge Rhyolite. 
254 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Popes Creek Sand Member of the Calvert Formation 

Miocene 

Maryland, Virginia, Delaware 

Atlantic Coast basin 

Gibson, T.G., 1983, Stratigraphy of Miocene through lower Pleistocene strata of the 

United States central Atlantic Coastal Plain, in Ray, C.E., ed., Geology and paleontology of the Lee Creek Mine, North Carolina, I: Smithsonian Contributions to 

Paleobiology, no. 53, p. 35-80. 

Type section: Outcrop on the north bank of the Potomac River, 300ft 

southeast of the mouth of Popes Creek, Charles County, Md. 

The basal transgressive beds of the Calvert Formation in the 

Salisbury embayment are here removed from the Fairhaven Member 

because of their lithologic distinction from the rest of the Fairhaven and 

are here named the Popes Creek Sand Member. Crops out in Maryland 

west of the Chesapeake Bay from near Fairhaven south to Popes Creek 

and into Virginia. Extends into Delaware in the subsurface. Consists of 

olive-brown and green to greenish-white glauconitic quartz sand having 

a basal layer of quartz and phosphate pebbles and phosphatized mollusk 

shells. Unconformably overlies the Nanjemoy Formation; overlies an 

older cycle of sand and diatomaceous clay beds, termed the Dunkirk 

beds of the Calvert Formation, along the Patuxent River in Maryland. 

Underlies the Fairhaven Member of the Calvert. Thickness at the type 

section is 10.5 ft. Age is early Miocene. 

Popes Head Formation 

late Proterozoic and (or) Early Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., and Lyttle, P.T., 1981, The Accotink Schist, Lake Barcroft Metasandstone, and Popes Head Formation-Keys to an understanding of the tectonic evolution 

of the northern Virginia Piedmont: U.S. Geological Survey Professional Paper 1205, 

16 p. 

Type locality: Exposures along Popes Head Creek and adjacent tracks 

of the Southern Railroad between Station Hills, Fairfax 7.5-minute 

quadrangle, and the confluence of the creek with Bull Run, Manassas 

7.5-minute quadrangle, Fairfax County, Va. 

Subunits: Old Mill Branch Metasiltstone Member, Station Hills 

Phyllite Member. 

The Popes Head Formation, here named, is a sequence of metasiltstone and phyllite in northern Virginia that was originally named the 

Clifton Phyllite by A.P. Bennison and Charles Milton (USGS, unpublished data, 1950). The unit is renamed the Popes Head Formation 

because the geographic name Clifton is preempted. Includes the Old 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 255 

Mill Branch Metasiltstone Member (new name) and the Station Hills 

Phyllite Member (new name). Unconformably overlies all other metasedimentary and transported meta-igneous rocks of the Wissahickon 

terrane in northern Virginia including the allochthon consisting of the 

Yorkshire Formation and the Piney Branch Complex (both new names). 

Is intruded by Occoquan Granite. Age is Late Proterozoic and (or) 

Early Cambrian based on a radiometric age of Early Cambrian for the 

Occoquan Granite. 

Poplar Hill Gneiss of the Oswegatchie Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: Road cut on Route 58 and exposures on adjacent Poplar 

Hill, 2.4 km west of Emeryville, between Balmat and Gouverneur, St. 

Lawrence County, N.Y. 

The Poplar Hill Gneiss of the Oswegatchie Group, here named, was 

previously named the Major Paragneiss by Engel and Engel (1953). 

Occurs in the Northwest Lowlands of the Adirondack Mountains, N.Y. 

Consists of rusty-brown- or gray-weathering biotite-quartz-oligoclase 

gneiss that has thin layers and veins of pink to white granitic gneiss. 

Overlies the Baldface Hill Gneiss (new name) and unconformably 

underlies the Gouverneur Marble, both of the Oswegatchie Group. 

Correlates with the Eagle Lake Gneiss of the Lake George Group (both 

new names) in the eastern Adirondacks. Age is Proterozoic. 

Poppin Rock Member of the Slade Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R., 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Roadcut along the western side of Kentucky Highway 

1274, 1.1 km north of the Licking River (Cave Run Lake), Bangor 

quadrangle, Rowan County, Ky. Named for Poppin Rock tunnel near 

Paragon, 5.5 km east of the type section. 

The Poppin Rock Member, here named, is in the Slade Formation 

(new name) and was previously called the Glen Dean Limestone. Usage 
256 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

of the name Glen Dean is here restricted from the Cumberland 

Escarpment outcrop area of east-central and northeastern Kentucky, 

and the usage of the name Poppin Rock is restricted to the geographic 

limits of the Slade Formation. Occurs throughout the outcrop belt of the 

Slade south of Greenup County. Consists of thin- to thick-bedded 

calcarenite that has shale partings. Conformably or disconformably 

overlies the Maddox Branch Member (new name) of the Slade; conformably underlies or intertongues with the Paragon Formation (new 

name), or disconformably underlies the Paragon, Lee, or Breathitt 

Formations in the north. Thickness ranges from 0 to 12 m. Age is Late 

Mississippian. 

Porvenir Formation of the Madera Group 

Middle Pennsylvanian (Desmoinesian) 

New Mexico 

Palo Duro basin, las Vegas-Raton basin 

Baltz, E.H., and Myers, D.A., 1984, Porvenir Formation (new name)-And other 

revisions of nomenclature of Mississippian, Pennsylvanian, and Lower Permian rocks, 

southeastern Sangre de Cristo Mountains, New Mexico: U.S. Geological Survey 

Bulletin 1537-B, p. B1-B39. 

Type section: Along U.S. Forest Service Johnson Mesa road on the 

ridge south of Canovas Canyon, a south tributary of Gallinas Creek, 

12.5 mi northwest of Las Vegas, Santa Fe National Forest, center sec. 

23, T. 17 N., R. 14 E., San Miguel County, N.Mex. Principal reference 

section specified for northern facies. Named for exposures in hogbacks 

near El Porvenir Campground. 

Rocks previously called the lower gray limestone member of the 

Madera Formation are here named the Porvenir Formation, the lower 

unit of the Madera Group in the southeastern Sangre de Cristo 

Mountains, San Miguel and Mora Counties, N. Mex. Includes three 

laterally intergrading marine facies: a southern carbonate facies, a 

shale-carbonate facies, and a northern sandstone-shale-carbonate 

facies. Consists of limestone and interbedded gray shale and a minor 

amount of sandstone at the type section, characteristic of the southern 

carbonate facies deposited in shallow seas. Consists of shale, sandy and 

oolitic limestones, and arkosic sandstone to the northeast. Conformably 

overlies the Sandia Formation; disconformably underlies the Alamitos 

Formation of the Madera Group. Thickness at the type section is 1,065 

ft and ranges from 700 to 1,615 ft. Age is Middle Pennsylvanian based 

on fusulinids of Desmoinesian Age. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 257 

Posey Canyon Shale Member of the Peace Valley Formation 

of the Ridge Basin Group 

Miocene 

California 

Los Angeles basin 

Link, M.H., 1982, Stratigraphic nomenclature and age of Miocene strata, Ridge basin, 

southern California, in Crowell, J.C., and Link, M.H., eds., Geologic history of Ridge 

basin, southern California: Society of Economic Paleontologists and Mineralogists, 

Pacific Section, guidebook, p. 5--12. 

Type section: Outcrops on the southwest side of Pyramid Dam and 

Lake, Los Angeles County, Calif. Named for Posey Canyon, which is 

now covered by Pyramid Lake. 

The Posey Canyon Shale Member, here named, is in the Peace 

Valley Formation, redefined, of the Ridge Basin Group in the central 

Ridge basin, Los Angeles County, Calif., where the Peace Valley is 

separated into five members by clastic tongues of the Ridge Route 

Formation. Consists of indurated gray shale, mudstone, dolomicrite, 

pyritic shale and siltstone, and gypsiferous siltstone and contains plant, 

fish, ostracode, and mollusk fossils. Lateral extent is 2, 700 to 3,600 m; 

interfingers with the Violin Breccia to the southwest and the Ridge 

Route Formation undivided and its Apple Canyon Siltstone Member 

(new name) to the northeast. Conformably overlies the Piru Gorge 

Sandstone Member (redefined) of the Ridge Route Formation; conformably underlies the Alamos Canyon Siltstone Member (new name) of the 

Peace Valley and is separated from it by a distinctive tuff horizon. 

Thickness is 1, 000 m at the type section and ranges from 730 to 1, 000 m. 

Age is late Miocene based on fossil plants. 

Poverty Flat Sandstone 

Eocene 

California 

San Joaquin basin 

Bartow, J.A., 1985, Revisions in the Tertiary stratigraphy of the east flank of the Diablo 

Range, central California: U.S. Geological Survey Bulletin 1605--A, p. A1-A6. 

Type section: Along the California Aqueduct south of Orestimba Creek, 

sees. 20, 29, and 32, T. 7 S., R. 8 E., Newman 7.5-minute quadrangle, 

Stanislaus County, Calif. Reference section: Texaco Howard 1 well, 25 

km east of the type section. Named for Poverty Flat, a valley east of the 

aqueduct. 
258 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Poverty Flat Sandstone, here named, includes conglomerate 

and conglomeratic sandstone previously assigned to the undifferentiated Miocene between Garzas and Crow Creeks by Anderson and Pack 

(1915), the informally named Poverty Flat siltstone by Collins (1950), 

and the basal part of the San Pablo Formation of Anderson and Pack 

(1915) in the area south of Hospital Creek on the east flank of the Diablo 

Range. Consists of gray or blue-gray lithic sandstone in the lower part 

and interbedded gray to white kaolinitic quartzose sandstone and 

siltstone, carbonaceous shale, kaolinitic claystone, and conglomerate in 

the upper part. Red or orange mottling is characteristic in the upper 

part. Overlies, possibly unconformably, the Kreyenhagen Shale; unconformably underlies the Valley Springs Formation. Age is late middle 

and late Eocene based on diatoms and mollusks. 

Pressmens Home Formation 

Mississippian 

Tennessee 

Appalachian basin 

Brent, W.B., 1982, Mississippian stratigraphy of Greendale and Newman Ridge synclines 

and Middle Ordovician nomenclature in upper east Tennessee: Tennessee Division of 

Geology Report of Investigations 41, 37 p. 

Type section: Exposures on a hillside 3.2 km northeast of Camelot 

(Pressmens Home) and 244 m north of Laurel View Church, 0.5 km 

northwest of the intersection of Tennessee Highway 94 and Laurel 

Branch Road, Camelot quadrangle, Hawkins County, Tenn. 

The Pressmens Home Formation, informally named by Sanders 

(1952), is here named. These Mississippian strata in the Greendale 

syncline in Hawkins and Grainger Counties, Tenn., were previously 

named the Newman Limestone by Hardeman and others (1966), but are 

isolated from the type Newman Limestone in the Newman Ridge 

syncline. The Pressmens Home consists of siltstone, sandstone, limestone, and dolostone that grade into one another both horizontally and 

vertically. Overlies the Maccrady Formation; underlies the Laurel 

Branch Limestone (new name). Correlates with the Little Valley 

Formation of Averitt (1941). Thickness is 44.6 m at the type section. 

Age is Mississippian. 

Proctor Creek Member of the Canton Formation 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

German, J.M., 1985, The geology of the northeastern portion of the Dahlonega gold belt: 

Georgia Geologic Survey Bulletin 109, p. 1-41. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 259 

Type locality: Exposures along Proctor Creek near Dawsonville, Dawsonville 7.5-minute quadrangle, Dawson County, Ga. 

The Proctor Creek Member of the Canton Formation, here named, 

is in the Dahlonega, Ga., area and was previously mapped as Carolina 

Gneiss by Keith (1909). Consists of fine- to medium-grained muscovitegarnet-biotite-quartz schist having a silvery luster. Sharply overlies 

iron formation or amphibolite of the Pumpkinvine Creek Formation; 

gradationally underlies darker garnet-poor biotite-quartz schist of the 

Palmer Creek Member (new name) of the Canton. Age is Late Proterozoic and (or) early Paleozoic. 

Proffit Mountain Formation of the St. Francois Mountains 

Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology Number 6, p. 81-90. 

Type section: SWl/4 sec. 16, T. 33 N., R. 2 E., Johnson Shut-ins 

quadrangle, Reynolds County, Mo. Derivation of name not stated. 

Rocks previously mapped as the lower part of the tuff of Johnson 

Shut-ins by Anderson (1970) are here named the Proffit Mountain 

Formation. Occurs in the western St. Francois Mountains in southeast 

Missouri. Consists of six tuff units: A, red ash-flow tuff containing 

quartz and feldspar phenocrysts, 16m thick; B, red or gray, crossbedded air-fall tuff, 5 m thick; C, deep-maroon ash-flow tuff containing 

quartz and feldspar phenocrysts, 39m thick; D, rose-gray ash-flow tuff 

containing quartz and feldspar phenocrysts, 56 m thick; E, red, crossbedded air-fall tuff, 15m thick; and F, gray, crossbedded air-fall tuff, 7 

m thick. Overlies the Taum Sauk Rhyolite (new name); underlies the 

Johnson Shut-ins Rhyolite (new name). Age is Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E.B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Proffit Mountain Formation. 
260 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Promised Land Formation of the Atlanta Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type section: Roadcuts along Georgia Highway 124 where it crosses the 

Yellow River, 1 km west of Promised Land, Snellville quadrangle, 

Gwinnett County, Ga. 

Subunit: Hannah Member. 

The Promised Land Formation of the Atlanta Group (new name), 

here named, is in the Newnan-Tucker synform near Atlanta, Ga. 

Consists of interlayered gneiss and amphibolite in the lower part and 

the Hannah Member (new name), composed of quartzite and schist, at 

the top. Is in gradational contact with the Wolf Creek Formation (new 

name), in sharp conformable contact with the Clairmont Formation 

(new name), both of the Atlanta, and in sharp, probably tectonic contact 

with the Lithonia Gneiss. Thickness ranges from 400 to 1,500 m. Age is 

Late Proterozoic and (or) early Paleozoic. 

Prospect Mountain Hornblende Granitic Gneiss 

Middle Proterozoic 

New York 

New England province 

Fisher, D.W., 1984, Bedrock geology of the Glens Falls-Whitehall region, New York: 

New York State Museum Map and Chart Series no. 35, 58 p. 

Type locality: Exposures along the Prospect Mountain Memorial Highway, Lake George quadrangle, Warren County, N.Y. 

The Prospect Mountain Hornblende Granitic Gneiss is here named. 

Consists of dark-olive-brown- to gray- or pink-weathering, light- to 

medium-gray, medium- to coarse-grained, locally megacrystic, foliated 

gneiss containing biotite, garnet, graphite, augite, and hypersthene. 

Contains small unmappable bodies of meta-anorthosite. Age is Middle 

Proterozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 261 

Pumpkin Bay Formation 

Early Cretaceous (Coahuilan) 

Florida 

South Florida province 

Applegate, A.V., Winston, G.O., and Palacas, J.G., 1981, Subdivision and regional 

stratigraphy of the Pre-Punta Gorda rocks (Lowermost Cretaceous-Jurassic(?)) in 

south Florida: Gulf Coast Association of Geological Societies Transactions, October 

(supplement), v. 31, p. 447-453. 

Type section: Bass Collier Company 12-2 well P-778, depth interval 

14,050-15,130 ft, sec. 12, T. 52 S., R. 27 E., Collier County, Fla. Named 

for Pumpkin Bay, 3 mi south of the type well. 

The Pumpkin Bay Formation, here named, is in the subsurface of 

the South Florida basin, where it is one of four regionally persistent 

anhydrite units below the Punta Gorda Anhydrite of the Glades Group. 

Consists of anhydrite and dolomite in the lower part and cream, tan, and 

brown micritic limestone, occasionally oolitic, in the upper part. Overlies the Bone Island Formation (new name); the contact is at the top of 

a regionally persistent 200-ft anhydrite bed in the Bone Island; underlies the West Felda Shale Member (new name) of the Lehigh Acres 

Formation (new name) of the Glades. Thickness is 1,080 ft at the type 

well. Age is Early Cretaceous (late Coahuilan) based on stratigraphic 

position. 

Put River Sandstone 

Early Cretaceous 

Alaska 

Arctic Coastal Plains province 

Jamison, H.C., Brockett, L.D., and Mcintosh, R.A., 1980, Prudhoe Bay-A 10-year 

perspective, in Halbouty, M.T., ed., Giant oil and gas fields of the decade 1968--1978: 

American Association of Petroleum Geologists Memoir 30, p. 289-314. 

Type section: ARCO-Exxon NGI-7 well, depth interval 8,027-8,091 ft, 

Prudhoe Bay field, T. 11 N., R. 14 E., Umiat Base Line, Alaska. 

Derivation of name not stated. 

The Put River Sandstone, here named, is in the center of the 

Prudhoe Bay field and along the western shoreline of Prudhoe Bay, 

where it occupies the basal sections of channels eroded into the rocks 

underlying the Lower Cretaceous erosion surface. Consists of graybrown, conglomeratic, quartzose chert sandstone containing lesser 

amounts of glauconite. Occurs directly above the Lower Cretaceous 

unconformity and unconformably overlies the Sag River Sandstone; 

underlies unnamed Lower Cretaceous shale. Is considered part of the 

Permo-Triassic Reservoir of the Prudhoe Bay field. Thickness at the 

type section is 64 ft. Age is Early Cretaceous based on micropaleontologic and palynologic data. 
262 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Pyramid Lake Member of the Mount Mazama Formation 

Pleistocene 

Nevada, California 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: East shore of Pyramid Lake, 500 m southeast of Pyramid 

Island, center NEl/4SWl/4 sec. 3, T. 24 N., R. 22 E., Washoe County, 

Nev. 

Subunits: Pelican Island, Timber Lake, Wono, Leter Ranch, and Trego 

Hot Springs Beds. 

The Pyramid Lake Member of the Mount Mazama Formation, here 

named, is in the Lake Lahontan area, Nevada, and California. Contains 

five tephra beds, named above in ascending order (all new names), 

which are inferred to represent the products of a single body of magma 

that was becoming progressively more potassium rich and differentiated and whose source was Mount Mazama. Beds are intercalated with 

the lower member of the Sehoo Formation. Age is Pleistocene, 35 to 

11.5 ka. 

Quartet Group of the Wernecke Supergroup 

Middle Proterozoic 

Canada, Alaska 

Yukon-Porcupine province 

Delaney, G.D., 1981, The mid-Proterozoic Wernecke Supergroup, Wernecke Mountains, 

Yukon Territory, in Campbell, F.H.A., ed., Proterozoic basins of Canada: Geological 

Survey of Canada Paper 81-10, p. 1-23. 

Type area: Extensive exposures in the Wernecke and Ogilvie Mountains and the Keele Range of the Porcupine Plateau, Yukon Territory, 

Canada. Derivation of name not stated. 

The Quartet Group of the Wernecke Supergroup (new name), here 

named in the Yukon Territory, Canada, extends into Alaska in the 

Keele Range of the Porcupine Plateau. Is subdivided into two units of 

formational rank, informally designated Q-1 and Q-2. Consists of a 

monotonous succession of dark-gray-weathering siltstone, fine sandstone, mudstone, claystone, and minor silty dolomite. Basal part of the 

unit accumulated in a sediment-starved stagnant basin and the greater 

part was deposited in a shallow marine environment. Thickness is a 

minimum of 5 km. Age is Middle Proterozoic, 1,700 to 1,200 Ma. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 263 

Railroad Canyon Formation 

Late Mississippian (Chesterian) 

Idaho, Montana 

Idaho Mountains province, Montana folded belt province 

Wardlaw, B.R., and Pecora, W.C., 1985, New Mississippian-Pennsylvanian stratigraphic 

units in southwest Montana and adjacent Idaho, in Sando, W.J., ed., Mississippian and 

Pennsylvanian stratigraphy in southwest Montana and adjacent Idaho: U.S. Geological 

Survey Bulletin 1656-B, p. B1-B9. 

Type section: Northwest of Railroad Canyon, NWV4 sec. 31 and SEV4 

sec. 30, T. 17 S., R. 27 E., Bannock Pass 7.5-minute quadrangle, Lemhi 

County, Idaho. 

The Railroad Canyon Formation, here named, is in the Beaverhead 

Range in east-central Idaho and southwest Montana. Consists of gray to 

black shale; gray, thin-bedded, flaggy, silty lime-mudstone; thin-bedded 

calcareous siltstone; olive-gray, flaggy claystone; mudchip, bioclastic 

conglomerate; yellow and gray, thin- to medium-bedded packstone; and 

gray, thin-bedded wackestone. Overlies the Scott Peak Formation; 

underlies the Bluebird Mountain Formation. Is equivalent to the 

Lombard Limestone (new name) and the Conover Ranch Formation 

(new name), both of the Snowcrest Range Group (new name), and the 

Surrett Canyon and Arco Hills Formations. Thickness is 205 m at the 

type section. Age is Late Mississippian (Chesterian) based on brachiopod and conodont faunas (Sando and Bamber Coral Zone V, or 

younger). 

Rainbow Gardens Member of the Horse Spring Formation 

Miocene 

Nevada, Arizona 

Great Basin province 

Bohannon, R.G., 1984, Nonmarine sedimentary rocks of Tertiary age in the Lake Mead 

region, southeastern Nevada and northwestern Arizona: U.S. Geological Survey 

Professional Paper 1259, 72 p. 

Type section: Exposures in Rainbow Gardens, lat 36°08'30" N., long 

114°57'30" W., Henderson and Frenchman Mountain 7.5-minute quadrangles, Clark County, Nev. 

The Rainbow Gardens Member, here named the lowermost of four 

members of the revised Horse Spring Formation, is recognized between 

Frenchman Mountain, Clark County, Nev., and Grand Wash Cliff, 

Mohave County, Ariz. Includes the oldest mappable unit in Longwell's 

(1963) Thumb Formation east of Frenchman Mountain, the oldest 

mappable Tertiary unit in the Bitter Spring Valley area, most of the 

Horse Spring Formation at Overton Ridge, and the lowest unit of the 

Horse Spring in the Virgin Mountains area. Consists of interbedded 
264 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

clastic sedimentary rocks ranging from conglomerate to claystone, 

carbonate rocks, evaporite beds, and chert. Gray and red-brown, 

blocky-weathering conglomerate occurs at the base at all exposures; the 

top is marked by a resistant limestone that forms a hogback through 

Rainbow Gardens. Represents a basal pediment gravel deposit overlain 

by a complex system of lake and playa deposits. Unconformably overlies 

the Kaibab Limestone and Moenkopi Formation through the Aztec 

Sandstone and Baseline Sandstone, depending on locality; underlies the 

revised Thumb Member of the Horse Spring Formation. Unit is wedge 

shaped, and thickness ranges from 50 to 400 m. Age is Miocene, about 20 

Ma, based on fission-track ages of the Horse Spring Formation. 

Ramey Creek Member of the Slade Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R., 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Road cut at the intersection of Kentucky Highways 127 4 

and 801, Bangor quadrangle, Rowan County, Ky. Named for Ramey 

Creek, west of the type section. 

Strata previously assigned to the Cypress Sandstone, Golconda 

Formation, and other units that are now restricted from the Cumberland Escarpment area of east-central and northeastern Kentucky are 

here named the Ramey Creek Member of the Slade Formation (new 

name). Consists of interbedded limestone and shale containing abundant 

chert. Conformably overlies the Tygarts Creek Member (new name) 

and conformably underlies the Maddox Branch Member (new name), 

both of the Slade Formation. Thickness ranges from 0 to 10m. Age is 

Late Mississippian. 

Ramsey Member of the Bell Canyon Formation of the 

Delaware Mountain Group 

Late Permian (Guadalupian) 

Texas, New Mexico 

Permian basin 

Winner, Phil, 1985, Type section for the uppermost Bell Canyon Formation in the central 

Delaware basin of West Texas: West Texas Geological Society Bulletin, v. 24, no. 7, 

p. 7-10. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 265 

Type section: Gulf J.R. Grandin Number 1 well, sonic-gamma-ray log, 

SEl/4 sec. 33, Block 29 PSL Survey, Loving County, Tex. Derivation of 

name not stated. 

The Ramsey Member, here named, is in the informal A sand in the 

upper Bell Canyon Formation of the Delaware Mountain Group in the 

central Delaware basin of Texas and New Mexico. Was previously 

designated the informal unranked Ramsey sand by Nottingham (1960) 

and the Ramsey sandstone member by Grauten (1965). Is the uppermost and most prolific pay zone in the A sand and produces in the Two 

Freds, Monroe, Meridian, Paduca, Grice, El Mar, Pinal Dome, and 

Quito fields. Consists of very fine grained sandstone or coarse-grained 

siltstone and contains three informal sand units, in ascending order, R3, 

R2, and Rl. R3 is absent in the Grice, El Mar, and Paduca fields and 

probably is absent west of these fields as well. R2 and R1 are regionally 

extensive and cover the entire central Delaware basin. Extends from 

the top of the Ford Member (new name) of the Bell Canyon to the third 

shale unit above the Ford Member; underlies the Trap Member (new 

name) of the Bell Canyon. Thickness ranges from 30 to 60 ft. [Age is 

Late Permian ( Guadalupian).] 

Rancheria Gulch Sandstone Beds of the Blue Gulch Mudstone 

Member of the Hornbrook Formation 

Late Cretaceous (Campanian) 

California 

Klamath Mountains province 

Nilsen, T.H., 1984, Tectonics and sedimentation of the Upper Cretaceous Hornbrook 

Formation, Oregon and California, in Crouch, J.K., and Bachman, S.B., eds., 

Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and Mineralogists, Pacific Section, v. 38, p. 101-118. 

Type section: Two low ridges directly southeast of Rancheria Gulch, 

center Sl/2SWl/4 sec. 20, T. 47 N., R. 6 W., Hornbrook 15-minute 

quadrangle, Siskiyou County, Calif. 

The Rancheria Gulch Sandstone Beds, here named, are in the lower 

part of the Blue Gulch Mudstone Member (new name) of the Hornbrook 

Formation along the northeast margin of the Klamath Mountains 

between Ditch Creek and Osburger Gulch, Siskiyou County, Calif. 

Consists of gray, fine-grained sandstone that has thin interbeds of 

siltstone near the top. Molluskan fossils are present locally. Conformably overlies and underlies mudstone and siltstone of the Blue Gulch. 

Thickness is 85.8 m at the type section and ranges from 0 to 85.8 m. Age 

is Late Cretaceous (Campanian). 
266 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Ravencliff Member of the Hinton Formation 

Late Mississippian (Chesterian) 

West Virginia 

Appalachian basin 

Schalla, R.A., 1984, Deltaic deposits of the Upper Mississippian Ravencliff Member of the 

Hinton Formation, southern West Virginia: Southeastern Geology, v. 25, no. 1, 

p. 1-12. 

Type locality: None designated. Origin of the name is unknown, but it 

is a generally accepted drillers' term in West Virginia, Kentucky, and 

Virginia. 

A distinctive group of lithologies identified by geophysical and 

drillers' logs in the subsurface in McDowell and Wyoming Counties, 

W. V., is here named the Ravencliff Member of the Hinton Formation. 

Consists of a heterogeneous sequence of sandstone, quartz pebble 

conglomerate, and interbedded variegated shale. Is restricted to the 

strata that conformably overlie the Little Stone Gap Member and 

conformably underlie the radioactive Hot Shale marker bed of the 

Hinton Formation. Thickness ranges from 410 to 465 ft. Age is Late 

Mississippian (Chesterian). 

Red Shirt Gabbro 

Cretaceous 

Washington 

Northern Cascade Range-Okanogan province 

Menzer, F.J., Jr., 1983, Metamorphism and plutonism in the central part of the Okanogan 

Range, Washington: Geological Society of America Bulletin, v. 94, no. 4, p. 471-498. 

Type locality: Outcrops west of the portal of the Red Shirt mine, east 

side of the Methow Valley, T. 33 N., R. 23 E., Okanogan County, Wash. 

The Red Shirt Gabbro, a postmetamorphic plutonic unit, here 

named, is in the Okanogan Range, Wash. Consists of massive, magmatic gabbro containing labradorite and green hornblende. Contact 

with the Wolf Canyon Quartz Diorite (new name) may be intrusive or 

gradational. Age is Cretaceous. 

Rhodes Tuff 

Miocene 

California 

Great Basin province 

Wright, L.A., Kramer, J.H., Thornton, C.P., and Troxel, B.W., 1984, Appendix 1-Type 

sections of two newly named volcanic units of the central Death Valley volcanic field, 

eastern California, in Wright, L.A., and Troxel, B. W., Geology of the northern half of 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 267 

the Confidence Hills 15-minute quadrangle, Death Valley region, eastern California: 

the area of the Amargosa chaos: California Division of Mines and Geology Map Sheet 

34, p. 21-24. 

Type section: Composite of exposures extending for 12 km along the 

lower southwest sides of Salsberry Peak and Sheephead Mountain, from 

Rhodes Wash eastward to Salsberry Pass in the Black Mountains, 

Confidence Hills and Shoshone 15-minute quadrangles, lnyo County, 

Calif. 

The Rhodes Tuff, here named, is in the Confidence Hills and 

Shoshone quadrangles in the central Death Valley volcanic field, 

California. Consists of a lower layer of air-falllapilli tuff, a few meters 

thick, conformably overlain by more resistant, knob forming, ash-flow 

tuff displaying a lower zone of dense welding that has a basal layer of 

black obsidian, 1 to 2 m thick, grading upward into grayish-red 

vitrophyre; a middle zone of grayish-brown partially welded tuff; and an 

upper zone of grayish-pink tuff showing no welding. Overlies dacitic 

flows; conformably underlies the Sheephead Andesite (new name). 

Thickness is 450 m at Salsberry Pass. Age is Miocene based on 

potassium-argon ages of 10.4 Ma for the underlying dacitic flows and 8. 7 

to 7.6 Ma for the overlying Shoshone Volcanics. 

Richard Russell Formation 

late Proterozoic 

Georgia, North Carolina 

Piedmont-Blue Ridge province 

Nelson, A.E., and Gillon, K.A., 1985, Stratigraphic nomenclature in the Richard Russell 

and Helen thrust sheets, Georgia and North Carolina: U.S. Geological Survey Bulletin 

1605-A, p. A59-A62. 

Type locality: Exposures along Richard Russell Highway (Georgia 

Highway 348) extending for 0.3 mi northwest from Hogpen Gap, 

Cowrock 7.5-minute quadrangle, Union County, Ga. 

The informal Richard Russell formation of Gillon (1982) is here 

named the Richard Russell Formation in the Richard Russell thrust 

sheet in Georgia and North Carolina. Consists of inter layered migmatitic biotite gneiss, metasandstone, aluminous biotite schist and biotitemuscovite schist, granofels, and amphibolite. Is bounded on the northwest by the Hayesville fault and on the southeast by the Shope Fork 

fault. Thickness is unknown. Age is probably Late Proterozoic. 
268 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Rincon Windmill Member of the Spears Formation of the 

Datil Group 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: Exposures 14 mi northeast of Datil and 1.25 mi northnorthwest of Rincon Windmill, NWl/4NWl/4 sec. 18, T. 1 N., R. 8 W., 

northeast Datil Mountains, Dog Springs 7.5-minute quadrangle, 

Socorro County, N. Mex. 

The Rincon Windmill Member is here named the upper member of 

the Spears Formation of the Datil Group in the Orogrande basin and in 

the Gallinas Mountains, N. Mex. Consists of brown to light-brown, 

volcaniclastic sandstones and conglomerates, which have pebble to 

cobble conglomerates in the lower two-thirds and well-sorted, feldspathic, aeolian sandstone in the upper one-third. Overlies the Rock 

House Canyon Tuff (new name) of the Datil Group; is interbedded with 

and locally split into two tongues by the Blue Canyon Tuff (new name) 

of the Datil; underlies the Hells Mesa Tuff. Thickness is 411 ft at the 

type section and ranges from 275 to 500ft. Age is Oligocene. 

Rio Salado Tongue of the Mancos Shale 

Late Cretaceous (Cenomanian to Turonian) 

New Mexico 

San juan basin 

Hook, S.C., Molenaar, C.M., and Cobban, W.A., 1983, Stratigraphy and revision of 

nomenclature of upper Cenomanian to Turonian (Upper Cretaceous) rocks of westcentral New Mexico: New Mexico Bureau of Mines and Mineral Resources Circular 

185, p. 7-28. 

Type section: Exposures in the Rio Salado valley, NEl/4 sec. 33, T. 3 N., 

R. 6 W., Puertocito quadrangle, Socorro County, N. Mex. 

Subunit: Bridge Creek Limestone Beds. 

The Rio Salado Tongue of the Mancos Shale, here named, is in the 

Orogrande basin, New Mexico. Defined as that part of the Mancos Shale 

separating the underlying Twowells Tongue of the Dakota Sandstone 

from the conformably overlying Atarque Sandstone Member of the Tres 

Hermanos Formation in west-central New Mexico or the Atarque 

Sandstone to the southwest, where the Tres Hermanos Formation is 

not used. Includes, in ascending order, (1) a lower shale and limestone 

unit consisting of calcareous fossiliferous shale and the Bridge Creek 

Limestone Beds, which are reduced in stratigraphic rank and replace 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 269 

the Greenhorn Limestone Member of the Mancos in this area, composed 

of gray fossiliferous shale, calcarenite, and limestone and (2) an upper 

light-olive-gray, noncalcareous clay-shale unit. Cannot be differentiated 

from Riley to Carthage and Truth or Consequences, except for limestones within the Bridge Creek Limestone Beds. Thickness ranges from 

200 to 300 ft. Age is Late Cretaceous (late Cenomanian to middle 

Turonian) based on ammonites. 

River Falls Formation 

Pleistocene (Illinoian or Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: South side of abandoned gravel quarry, 300 m south of 

Road E, 4 km northeast of Baldwin, SE1/4NE1/4NE1/4 sec. 18, T. 29 N., 

R. 16 W., Emerald 7.5-minute quadrangle, St. Croix County, Wis. 

Named for River Falls, Pierce County. 

The informal Baldwin till of Baker and Simpson (1981) is here named 

the River Falls Formation in the Superior Lobe in Pierce, St. Croix, and 

Dunn Counties, western Wisconsin. Consists of yellowish-red to 

reddish-brown, structureless basal till, locally weakly stratified, containing lenses of fine sand. Is deeply weathered to sandy clay loam. 

Sharply overlies the Hersey Member or the Kinnickinnic Member of the 

Pierce Formation (all new names); sharply underlies till, sand, and 

gravel of the late Wisconsinan St. Croix moraine or is exposed at the 

surface. Thickness ranges from less than 1 to more than 10 m. Age is 

Pleistocene (Illinoian or early Wisconsinan). 

Road Runner Rhyolite 

Miocene 

Arizona 

Basin and Range province 

Creasey, S.C., Peterson, D.W., and Gambell, N.A., 1983, Geologic map of the Teapot 

Mountain quadrangle, Pinal County, Arizona: U.S. Geological Survey Geologic Quadrangle Map GQ-1559, scale 1:24,000. 

Type locality: Exposures at Road Runner Mesa, S1/2 sec. 27 and N1/2 sec. 

34, T. 2 S., R. 12 E., Teapot Mountain quadrangle, Pinal County, Ariz. 

The Road Runner Rhyolite, here named, is in the Teapot Mountain 

quadrangle, Pinal County, Ariz., where it comprises both extensive 

flows and a semicircular plug 600 min diameter. Consists of pinkishgray, flow-banded, porphyritic volcanic rock having a vitrophyric 
270 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

groundmass in the flows and a microcrystalline groundmass in the plug. 

Phenocrysts consist of plagioclase, quartz, biotite, and magnetite. 

Vesicles, amygdules, and spherules occur in both flows and plug. 

Unconformably overlies the Sleeping Buffalo Rhyolite and its Arnett 

Member (both new names); unconformably underlies Quaternary 

gravel. Age is Miocene based on a potassium-argon age of 18.9 Ma. 

Robertstown Formation of the Helen Group 

late Proterozoic and (or) Paleozoic 

Georgia, North Carolina 

Piedmont-Blue Ridge province 

Nelson, A.E., and Gillon, K.A., 1985, Stratigraphic nomenclature in the Richard Russell 

and Helen thrust sheets, Georgia and North Carolina: U.S. Geological Survey Bulletin 

1605-A, p. A59-A62. 

Type locality: Exposures along the road on the west side of unnamed 

lake at Unicoi State Park, Helen 7.5-minute quadrangle, White County, 

Ga. Named for the nearby town of Robertstown. 

The informal Unicoi Park formation of Gillon (1982) is here named 

the Robertstown Formation of the Helen Group (new name) in the 

Helen thrust sheet in Georgia and North Carolina. Consists of thinly 

layered, coarse-grained feldspathic metasandstone interlayered with 

mica schist, amphibolite, and pebbly quartz metasandstone, and is 

characterized by thin, aluminous schist partings between metasandstone beds. Is conformable to the southeast with the Horton Formation 

(new name) of the Helen Group; is truncated on the northwest by the 

Shope Fork fault. Age is tentatively determined to be Late Proterozoic 

and early Paleozoic. 

Rock House Canyon Tuff of the Datil Group 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: Exposures 15 mi northeast of Datil and 3 mi north of 

North Lake at the junction of Rock House Canyon and Long Canyon, 

SW1/4 sec. 13, T. 1 N., R. 8 W., northwest Gallinas Mountains, Dog 

Springs 7.5-minute quadrangle, Socorro County, N. Mex. 

Rocks formerly called the tuff of Main Canyon and the tuff of Nipple 

Mountain are here named the Rock House Canyon Tuff of the Datil 

Group in the Datil, Gallinas, Crosby, and Magdalena Mountains, and 

Tres Montosas Magdalena area, in the Orogrande basin, New Mexico. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 271 

Consists of white, pink to purple-gray, or light-gray to tan, unwelded to 

moderately welded, crystal-poor, ash-flow tuff containing abundant 

elliptical pumice, sparse sanadine, and andesitic phenocrysts. Overlies 

the Chavez Canyon Member (new name) of the Spears Formation of the 

Datil Group; underlies the Blue Canyon Tuff (new name) of the Datil or 

the Rincon Windmill Member (new name) of the Spears. Thickness is 

225ft at the type section and ranges from 0 to 350ft. Age is Oligocene. 

Rock Mountain Conglomerate of the Phantom lake 

Metamorphic Suite 

Archean 

Wyoming 

Green River basin 

Karlstrom, K.E., Houston, R.S., Coolidge, C.M., Flurkey, A.J., and Sever, C.K., 1981, 

The geology of Archean and Early Proterozoic terraines of the Medicine Bow 

Mountains, Wyoming, in Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, 

eds., A summary of the geology and uranium potential of Precambrian conglomerates 

in southeastern Wyoming: U.S. Department of Energy National Uranium Resource 

Evaluation, v. 1, pt. 2, p. 197-399. 

Type locality: Outcrops on Rock Mountain and near the extreme 

northwestern limit of Precambrian outcrop, northern Medicine Bow 

Mountains, sees. 27 and 33, T. 19 N., R. 79 W., Carbon County, Wyo. 

The Rock Mountain Conglomerate, here named, is in the Phantom 

Lake Metamorphic Suite and crops out in the northern Medicine Bow 

Mountains, Wyo. Consists of coarse-grained muscovitic quartzite containing beds of anomalously radioactive quartz, quartzite, amphibolite, 

and schist paraconglomerate ranging in thickness from less than 1 m to 

several hundred meters. Lithologically similar conglomerates occur as 

lenses in the Stud Creek Volcaniclastic Rocks (new name) of the 

Phantom Lake in the Stud Creek area of the Medicine Bow Mountains. 

Overlies the Stud Creek Volcaniclastic Rocks possibly gradationally; 

gradationally or sharply conformably underlies the Bow River Quartzite 

(new name) of the Phantom Lake. Stratigraphic thickness is 400 m. Age 

is Archean. 

Rockwall Member of the Pecan Gap Formation of the Taylor 

Group 

Late Cretaceous (Campanian) 

Texas 

Ouachita tectonic belt province 

McNulty, C.L., Brezina, J.L., Dawson, W.C., and Maluf, F.W., 1981, Emendation of the 

Pecan Gap Chalk (Campanian) in northeast Texas: Gulf Coast Association of Geological 

Societies Transactions, v. 31, p. 353-358. 
272 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Gullied hillside along Farm-To-Market Road 740 between 

Rockwall and Interstate Highway I-30, 2 mi south of Rockwall, 

Rockwall County, Tex. (Maluf, 1975). 

Rocks informally named by Maluf (1975) are here named the 

Rockwall Member of the revised Pecan Gap Formation of the Taylor 

Group in the north-south outcrop belt in Collin and Rockwall Counties, 

Tex. Can be traced with the Lavon Member (new name) of the Pecan 

Gap from Farmersville to southern Rockwall County. Consists of darkto medium-olive-gray, yellowish-orange-weathering, silty marl containing beds of quartz siltstone and chalk. Gradationally overlies the Wolfe 

City Formation; disconformably underlies the Lavon Member. Thickness is 65ft at the type section. Age is Late Cretaceous (Campanian). 

Rocky Gulch Sandstone Member of the Hornbrook Formation 

Late Cretaceous (Campanian) 

California, Oregon 

Klamath Mountains province 

Nilsen, T.H., 1984, Tectonics and sedimentation of the Upper Cretaceous Hornbrook 

Formation, Oregon and California, in Crouch, J.K., and Bachman, S.B., eds., 

Tectonics and sedimentation along the California margin: Society of Economic Paleontologists and Mineralogists, Pacific Section, v. 38, p. 101-118. 

Type section: Roadcuts along the northbound lane of Interstate Highway I-5, adjacent to and west of the Klamath River and 3 km south of 

Hornbrook, NE1/4NE1/4 sec. 32, T. 47 N., R. 6 W., Hornbrook 15-minute 

quadrangle, Siskiyou County, Calif. Named for outcrops in Rocky 

Gulch, 2 km southwest of Hornbrook. 

The Rocky Gulch Sandstone Member of the Hornbrook Formation, 

here named, occurs along the northeast margin of the Klamath Mountains in Siskiyou County, Calif., and Jackson County, Oreg. Consists of 

beds of gray, fine- and medium-grained sandstone containing intervals 

of thin shale and local conglomerate and siltstone. Erosionally or 

gradationally overlies the Ditch Creek Siltstone Member (new name) 

and gradationally underlies the Blue Gulch Mudstone Member (new 

name), both of the Hornbrook. Thickness is 171.2 m at the type section 

and ranges from 115 to 225m. Age is Late Cretaceous (Campanian) 

based on foraminifera. 

Rodgers Shelter Formation 

Pleistocene and Holocene 

Missouri 

Ozark uplift 

Haynes, C.V., Jr., 1985, Mastodon-bearing springs and late Quaternary geochronology of 

the lower Pomme de Terre valley, Missouri: Geological Society of America Special 

Paper 204, 35 p. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 273 

Type locality: None designated. Named for Rodgers Shelter on the 

Pomme de Terre River, sec. 33, T. 39 N., R. 22 W., Fristoe 15-minute 

quadrangle, Benton County, Mo. 

Intermediate terrace deposits T-1c in the lower Pomme de Terre 

Valley, Benton and Hickory Counties, Mo., called the informal Rodgers 

formation by Brakenridge (1981), are here named the Rodgers Shelter 

Formation. Four strata are defined on the basis of erosional and 

lithologic contacts: stratum 1 consists of a matrix of brown to darkgrayish-brown alluvial clayey silt and colluvial gravel containing 

Paleoindian and Early Archaic artifacts; stratum 2 consists of darkgrayish brown clayey silt containing Middle Archaic artifacts; stratum 

3 consists of colluvial chert gravel; stratum 4 consists of alluvial silt and 

colluvial gravel containing Late Archaic to Woodland artifacts. Unconformably overlies the Boney Spring and Breshears Valley Formations 

(both new names) with an erosional hiatus; is exposed at the surface. 

Age is late Pleistocene and Holocene, 10.5 to 1.5 ka. 

Rose Creek Schist Member of the Univeter Formation of the 

New Georgia Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures near Rose Creek Church, Kennesaw 7.5-

minute quadrangle, Cherokee County, Ga. 

The Rose Creek Schist Member of the U niveter Formation (new 

name) of the New Georgia Group (new name), here named, is in the 

Greater Atlanta region of northwest Georgia. Forms the center of a fold 

of which the limbs are formed by the Lost Mountain Amphibolite 

Member (new name) of the Univeter. Consists of garnet-biotitemuscovite schist. Age is Late Proterozoic and (or) early Paleozoic. 

Roses Mill Plutonic Suite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Herz, Norman, and Force, E.R., 1984, Rock suites in Grenvillian terrane of the Roseland 

district, Virginia. Part 1: Lithologic relations: Geological Society of America Special 

Paper 194, p. 187-200. 

Type locality: Road cut at Roses Mill, east side of the Roseland district, 

Arrington 7.5-minute quadrangle, Nelson County, Va. 
274 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Roses Mill Plutonic Suite, here named in the Roseland district, 

Nelson and Amherst Counties, Va., includes the Roses Mill and Turkey 

Mountain plutons. Four dominant rock facies are present: primary 

charnockitic ferrodiorite, secondary biotite augen gneiss, dikes in older 

formations, and nelsonite. Plutons that intrude the anorthositegranulite terrane include the Roseland Anorthosite and the charnockitic 

rocks of the Pedlar massif. Xenoliths of older rock are found in the 

Roses Mill pluton; the Turkey Mountain pluton is intruded by the 

Mobley Mountain Granite (new name). Age is Middle Proterozoic based 

on a uranium-lead date of 970 Ma. 

Rosslyn Member of the Slade Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R., 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Exposure in the abandoned Baker Quarry on a ridge 1.6 

km southeast of Stanton, Ky., and north of Kentucky Highway 213, 

Stanton quadrangle, Powell County, Ky. Named for the community of 

Rosslyn, 2 km east of the type section. 

Strata previously assigned to the Renault Formation and ReelsvilleBeech Creek Limestone Member of the Newman Limestone, which are 

now restricted from the Cumberland Escarpment area of Kentucky, are 

here named the Rosslyn Member of the Slade Formation (new name) 

and are restricted to central Powell and southern Montgomery Counties. Consists of a basal conglomerate grading upward to thin-bedded 

calcarenite lenses interbedded with calcilutite. Disconformably overlies 

the Cave Branch Bed of the Slade; grades upward into the Tygarts 

Creek Member (new name) of the Slade. Thickness ranges from 0 to 2 

m. Age is Late Mississippian. 

Russell Mountain Rhyolite of the St. Francois Mountains 

Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 275 

Type section: NEl/4SWl/4 sec. 2, T. 33 N., R. 3 E., Ironton quadrangle, 

Iron County, Mo. Exposed on the east slope of Russell Mountain. 

Rocks previously mapped as the Shut-ins banded ash flow by 

Anderson (1962) and Unit C of the tuff of Stouts Creek by Anderson 

(1970) are here named the Russell Mountain Rhyolite in the western St. 

Francois Mountains in southeast Missouri. Consists of brick-red to 

dark-maroon ash-flow tuff containing large fiamme and white feldspar 

phenocrysts. Overlies the Lindsey Mountain Rhyolite (new name); 

underlies the Wildcat Mountain Rhyolite (new name). Thickness is 300 

m. Age is Middle Proterozoic. · 

Kisvarsanyi, E. B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E.B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Russell Mountain Rhyolite. 

Rye Patch Dam Bed of the Rye Patch Formation 

Pleistocene (Illinoian) 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Exposure at the east abutment of Rye Patch Dam on the 

Humboldt River at Rye Patch Reservoir, Pershing County, Nev. 

The Rye Patch Dam Bed, here named, is in the Rye Patch 

Formation in the Lake Lahontan area, Nevada. Tephra occurs in a lens 

of ash up to 2 m thick. Age is Pleistocene (Illinoian). 

Sabattis Road Member of the Lost Pond Marble 

Precambrian 

New York 

Adirondack uplift 

Potter, D. B., Jr., 1984, Cross section of the Loon Pond syncline, Tupper Lake quadrangle, New York, in Potter, D.B., Jr., ed., Field trip guidebook: New York State 

Geological Association, 56th Annual Meeting, trip AB-2, p. 3-15. 

Type locality: Exposures 0.5 km east of Bear Pond along Route 10, 

Tupper Lake 15-minute quadrangle, Hamilton County, N.Y. Derivation 

of name not stated. 

The Sabattis Road Member of the Lost Pond Marble (new name), 

here named, is in the Loon Pond syncline of the Bog River synclinorium 

in the Adirondack Highlands, Hamilton and St. Lawrence Counties, 
276 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

N.Y. Consists of interbedded coarse graphitic marble, diopside-calcite 

granulite, and thin-bedded quartzite. Overlies the Hill 2292 Member 

(new name) and underlies the Loon Pond Mountain Member (new 

name), both of the Lost Pond. Is cut by the Otter Pond Dioritic Gneiss 

(new name). Thickness is at least 60 m. Age is Precambrian. 

Sacony Member of the Virginville Formation 

Late Cambrian and Early Ordovician 

Pennsylvania 

Appalachian basin 

Lash, G.G., and Drake, A.A., Jr., 1984, The Richmond and Greenwich slices of the 

Hamburg klippe in eastern Pennsylvania-Stratigraphy, sedimentology, structure, 

and plate tectonic implications: U.S. Geological Survey Professional Paper 1312, 40 p. 

Type locality: Exposures along Sacony Creek, 1.6 km northeast of 

Virginville, Kutztown 7.5-minute quadrangle, Berks County, Pa. 

Rocks described as the Martinsburg Shale by Miller (1937) are here 

named the Sacony Member of the Virginville Formation (new name) in 

the Richmond slice of the Hamburg klippe in Pennsylvania. Consists of 

massive, grayish-green and grayish-red, micaceous siltstone to sandstone intercalated with shale and mudstone. Outcrops form lenticular or 

ovoid masses. Tectonically overlies the Moselem Member (new name) of 

the Virginville; conformably underlies the Onyx Cave Member (new 

name) of the Virginville. Thickness is 245 m. Age is Late Cambrian and 

late Early Ordovician. 

Saddleback Mountain Suite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Saddleback Mountain, lat 38~2' N., long 78°30' W., Swift 

Run 7.5-minute quadrangle, Rockingham County, Va. 

Subunit: Old Rag Granite. 

The Saddle back Mountain Suite, here named, is in the Pedlar massif 

in the Blue Ridge in northern Virginia. Contains the Old Rag Granite of 

Furcron (1934) and a mesocharnockite facies. Age is Middle Proterozoic 

based on uranium-lead ages. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 277 

Sadler Ranch Formation 

Early and Middle Devonian 

Nevada 

Great Basin province 

Kendall, G.W., Johnson, J.G., Brown, J.O., and Klapper, G., 1983, Stratigraphy and 

facies across Lower Devonian-Middle Devonian boundary, central Nevada: American 

Association of Petroleum Geologists Bulletin, v. 67, no. 12, p. 2199-2207. 

Type section: Outcrops on a spur that extends up to the saddle directly 

north of Summit 7466, west of Sadler Ranch on the eastern side of the 

Sulphur Spring Range, Garden Valley 15-minute quadrangle, Eureka 

County, Nev. 

Rocks previously described as the middle, crinoidal part of the 

Union Mountain Formation by Carlisle and others (1957) are here 

named the Sadler Ranch Formation. Crops out along the eastern flank 

of the Sulphur Spring Range, at Table Mountain in the Mahogany Hills, 

Modoc Peak, Lone Mountain, and Union Mountain, Eureka County, 

Nev. Is divided into lower and upper dolomites and a middle crinoidal 

dolomite. Lower unit is moderately well-bedded, medium- to thickbedded, and finely crystalline, yellowish-gray- to olive-grayweathering, olive-gray to brownish-black dolomite; middle crinoidal 

dolomite is crinoidal packstone; upper dolomite is similar to the lower 

dolomite. Was deposited in a shallow, nearshore, carbonate shelf and 

slope environment. Abruptly overlies the Bartine Limestone Member 

or the Coils Creek Member of the McColley Canyon Formation; 

conformably underlies the coarse crystalline member of the Oxyoke 

Canyon Formation. Thickness is 124 m at the type section. Age is Early 

and Middle Devonian based on the presence of conodont zones that 

define the Lower-Middle Devonian boundary. 

Salinas Peak Member of the Contadero Formation 

Late Devonian (Frasnian) 

New Mexico 

Orogrande basin 

Sorauf, J.E., 1984, Devonian stratigraphy of the San Andres Mountains, Dona Ana, 

Sierra, and Socorro Counties, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Circular 189, 32 p. 

Type section: Exposures in a gully above Montoya Plateau on the 

southwest flank of Salinas Peak, about 0.5 mi northeast of Route 12, 

Sweetwater Creek Canyon in White Sands Missile Range, 

NWV4NEV4SEV4 sec. 7, T. 12 S., R. 4 E., Salinas Peak quadrangle, 

Sierra County, N.Mex. 

The Salinas Peak Member, here named, is the lowest of three 

members of the Contadero Formation in the northern San Andres 
278 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Mountains of southwestern New Mexico. Consists of a basal unit of soft, 

tan shale, which is red at the base; a middle silty unit of brown or green 

shale interbedded with thin-bedded, coarse siltstone or flaggy sandstone; and an upper unit of blue-gray, nodular, argillaceous limestone 

containing abundant solitary rugose corals. Overlies the Sly Gap 

Formation; underlies the Thoroughgood Formation, revised as the 

Thurgood [sic] Member, or the Rhodes Canyon Member, both of the 

Contadero Formation. Thickness at the type section is 10.8 m. Age is 

Late Devonian (late Frasnian) based on brachiopods and conodonts. 

Salt Wells Member of the Mono Basin Formation 

Holocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Road cut 1.3 km south of Weber Dam, on the west side of 

the Walker River north of Schurz, center Wlf2Wlf2 sec. 33, T. 14 N., 

R. 28 E., Weber Reservoir 15-minute quadrangle, Mineral County, 

Nev. [Probably named for the town of Salt Wells.] 

Subunits: Walker Lake Bed, Turupah Flat Bed. 

The Salt Wells Member of the Mono Basin Formation (new name), 

here named, is in the Lake Lahontan sequence in Nevada. Contains two 

tephra layers regarded as stratigraphic markers, the Walker Lake Bed 

(new name) and the Turupah Flat Bed (new name), composed of rhyolite 

that has similar glass chemistry. Source is attributed to Mono Basin 

because of its distribution south of Carson Sink and because rhyolitic 

tephra of similar age and petrography were erupted in the Mono Basin. 

Age is Holocene, about 2 to 0.6 ka. 

Sand Hill Gneiss 

Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures near Sand Hill, Villa Rica 7.5-minute quadrangle, eastern Carroll County, Ga. 

The Sand Hill Gneiss, here named, is a pre- to synmetamorphic 

intrusive rock of the Piedmont in the Greater Atlanta region, Georgia. 

Consists of fine- to coarse-grained muscovite-biotite-oligoclase-quartzmicrocline orthogneiss. Age is Paleozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 279 

Sandy Creek Granulite Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Outcrop on State Road 619 along Sandy Creek, lat 

37°15'30" N., long 79°49' W., Stewartsville 7.5-minute quadrangle, 

Bedford County, Va. 

The Sandy Creek Granulite Gneiss, here named, is in the Lovingston massif in the Blue Ridge in southwestern Virginia and is a layered 

granulite gneiss. Age is Middle Proterozoic. 

Santa Rosa Hills Limestone 

late Mississippian (Visean) 

California 

Great Basin province 

Dunne, G.C., Gulliver, R.M., and Stevens, C.H., 1981, Correlation of Mississippian 

shelf-to-basin strata, eastern California: Geological Society of America Bulletin, v. 92, 

no. 1, pt. I, p. 1-4; pt. II, p. 1-38. 

Type section: Northwest side of hill6170 in Santa Rosa Hills, from 5,860 

ft elevation to saddle at 6,035 ft elevation, T. 17 S., R. 40 E., lat 

117°39'21" N., long 36°28'41" W., Darwin 15-minute quadrangle, lnyo 

County, Calif. 

A previously unrecognized unit in the Santa Rosa Hills and a unit 

previously mapped as Lee Flat Limestone in the carbonate facies region 

of the Argus and Panamint Ranges to the east and southeast are here 

named the Santa Rosa Hills Limestone. Consists of medium- to lightgray, massive-appearing, thick- and thin-bedded limestone or marble 

containing pelmatozoan debris and interbedded chert. Gradationally 

overlies the Perdido Formation; sharply and disconformably underlies 

the Rest Spring Shale. Forms a northwestward-thinning wedge that 

varies from 245 to 610 ft thick. Thickness at the type section is 272 ft. 

Age is Late Mississippian (middle and perhaps late Visean) based on 

corals, conodonts, and foraminifera. 
280 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Sawmill Canyon Formation 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type area: Exposures along both sides of Sawmill Canyon, 16 mi 

southeast of Magdalena, sees. 3, 4, 9, 10, 11, 14, and 15, T. 5 S., R. 3 W., 

South Baldy 7.5-minute quadrangle, Socorro County, N. Mex. 

Rocks called a unit of Sixmile Canyon or Sixmile Canyon andesite in 

earlier reports are here named the Sawmill Canyon Formation in the 

Magdalena Mountains, Orogrande basin, New Mexico. Informal members include the andesite of Landavaso Reservoir and, at the top, the 

tuff of Caronita Canyon, a thick, multiple-flow, simple cooling unit of 

ash-flow tuff. Is a complex cauldron-fill unit consisting of andesite flows, 

rhyolite flows and domes, ash-flow tuffs, conglomerates, and mudflow 

deposits. Overlies the La J encia Tuff (new name); underlies the Lemitar 

Tuff (new name). Age is Oligocene based on potassium-argon biotite 

dates of 29.7 Ma on bedded tuff in cauldron fill and 30.2 Ma on the tuff 

of Caronita Canyon. 

Schoolhouse Chert Member of the Moyers Formation of the 

Stanley Group 

Late Mississippian 

Oklahoma 

Ouachita tectonic belt province 

Pitt, W.D., Fay, R.O., Wilson, L.R., and Curiale, J.A., 1982, Geology of Pushmataha 

County, Oklahoma: Eastern New Mexico University Studies in Natural Sciences 

Special Publication 2, 101 p. 

Type locality: None designated. Named for the schoolhouse in Moyers, 

Pushmataha County, Okla. 

The Schoolhouse Chert Member of the Moyers Formation of the 

Stanley Group, here named, is in the Ouachita Mountains in Pushmataha County, southeastern Oklahoma. Consists of blue-gray to black 

banded siliceous shale and chert. Lies at the base of the Moyers, which 

overlies the Tenmile Creek Formation. Thickness ranges from 20 to 100 

ft. Age is Late Mississippian. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 281 

Schoolhouse Member of the Snowshoe Formation 

Middle Jurassic (Bajocian) 

Oregon 

Snake River basin 

Smith, P.L., 1980, Correlation of the members of the Jurassic Snowshoe Formation in the 

Izee basin of east-central Oregon: Canadian Journal of Earth Sciences, v. 17, no. 12, 

p. 1603-1608. 

Type section: Snowshoe Formation type section, South Fork of the John 

Day River near the former community of Izee, Izee 15-minute quadrangle, Grant County, Oreg. Named for Schoolhouse Gulch behind the 

former Izee schoolhouse. 

Rocks previously called the middle member of the Snowshoe Formation by Dickinson and Vigrass (1965) are here named the Schoolhouse 

Member of the Snowshoe. Consists of gray, green, or buff laminated 

siltstone and sandstone alternating with argillaceous mudstone, shale, 

and siltstone. Transitionally overlies the Warm Springs Member of the 

Snowshoe; interfingers laterally with the Basey Member of the Snowshoe in the Suplee area to the west and interfingers and underlies the 

Silvies Member of the Snowshoe to the east; unconformably underlies 

the South Fork Member (new name) of the Snowshoe or the Trowbridge 

Formation to the west. Thickness is 300 m in the type area; wedges out 

to the northeast. Age is Middle Jurassic (Bajocian). 

Scotch Grove Formation 

Early Silurian (Llandoverian and Wenlockian) 

Iowa 

Iowa shelf 

Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River fault zone and 

the structural and stratigraphic framework of eastern Iowa: Iowa Geological Survey 

Technical Information Series 13, 126 p. 

Type locality: Quarry area north of the town of Scotch Grove, 

NW1/4SE1/4SE1/4 and SE1/4NW1/4SE1/4 sec. 7, T. 85 N., R. 2 W., Jones 

County, Iowa. Reference core section: Near Walford, SE1/4SW1/4 

SW1/4SW1/4 sec. 5, T. 81 N., R. 8 W., Johnson County, Iowa. 

Subunits: Johns Creek Quarry Member, Welton Member, Buck Creek 

Quarry Member, Fawn Creek Member, Waubeek Member, PalisadesKepler Member. 

The Scotch Grove Formation, described as an informal rock unit by 

Witzke (1981) and here named, is in eastern Iowa and is defined as the 

interval of rocks above the Picture Rock Member (new name) of the 

Hopkinton Formation and below the base of the first laminated and 

mounded dolomites of the Gower Formation. The original definitions of 

both the Hopkinton and Gower are preserved with the introduction of 
282 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

the Scotch Grove Formation. Includes six members, in ascending order: 

the Johns Creek Quarry, Welton, and Buck Creek Quarry Members of 

Johnson (1983), here reassigned from the upper part of the revised 

Hopkinton Formation, and the Fawn Creek, Waubeek, and PalisadesKepler Members (all new names). Consists of a variety of carbonate 

facies including flat-lying and mounded, dense and porous, cherty and 

noncherty, sparsely fossiliferous and crinoid-moldic dolomite. Lower 

and upper contacts are conformable and sharp; the upper contact may 

be locally disconformable. Thickness ranges from 100 to 300 ft. Age is 

Early Silurian (late Llandoverian and Wenlockian). 

Senoia Formation of the Atlanta Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type section: Exposures along the first road running west from Georgia 

Highway 85, southwest of Keg Creek, in the city of Senoia, Senoia 

quadrangle, Coweta County, Ga. 

The Senoia Formation of the Atlanta Group (new name), here 

named, is in the Newnan-Tucker synform near Atlanta, Ga., and 

consists of garnet-biotite-muscovite schist interlayered with finegrained hornblende-plagioclase amphibolite. Lower contact has not 

been mapped; sharply and conformably underlies the Wahoo Creek 

Formation (new name) of the Atlanta. Correlates with most of the 

Clairmont Formation (new name) of the Atlanta. Age is Late Proterozoic and (or) early Paleozoic. 

Sentinel Island Formation of the Spieden Group 

Early Cretaceous (Valanginian and Hauterivian) 

Washington 

Puget Sound province 

Johnson, S.Y., 1981, The Spieden Group: An anomalous piece of the Cordilleran 

paleogeographic puzzle: Canadian Journal of Earth Sciences, v. 18, no. 11, 

p. 1694-1707. 

Type section: Northwest and southwest shorelines of Spieden Island 

and the western shoreline of Sentinel Island, sec. 2, T. 37 N., R. 4 W., 

San Juan Islands, San Juan County, Wash. 

The Sentinel Island Formation of the Spied en Group, here named, is 

in the San Juan Islands, Wash. Includes lower and upper members, 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 283 

separated by an inferred unconformity. Lower member consists of gray, 

fine- to medium-grained, fossiliferous sandstone and siltstone, deposited in a shallow marine environment, 140 m thick; upper member 

consists of volcanic conglomerate, deposited as an alluvial fan, possibly 

more than 600 m thick. Disconformably overlies the Spieden Bluff 

Formation (new name) of the Spieden Group with a hiatus of 20 to 30 

million years; top of the formation is not exposed. Age is Early 

Cretaceous (Valanginian and Hauterivian and possibly younger) based 

on fossils. 

Shaeffer Hollow Granite 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Herz, Norman, and Force, E.R., 1984, Rock suites in Grenvillian terrane of the Roseland 

district, Virginia. Part 1. Lithologic relations: Geological Society of America Special 

Paper 194, p. 187-200. 

Type locality: Exposures in and north of Shaeffer Hollow, Horseshoe 

Mountain 7.5-minute quadrangle, Nelson County, Va. 

The Shaeffer Hollow Granite, here named, is in the Roseland district 

of Nelson and Amherst Counties, Va. Consists of coarse-grained, 

leucocratic, blue quartz granite having tabular feldspar phenocrysts and 

porphyritic texture. Forms xenoliths in and is cut by dikes of the Roses 

Mill pluton. Age is Middle Proterozoic based on uranium-lead ages of 

1, 787 and 980 Ma. 

Shainin Lake Member of the Kanayut Conglomerate 

Late Devonian 

Alaska 

Norton basin 

Nilsen, T.H., and Moore, T.E., 1984, Stratigraphic nomenclature for the Upper Devonian 

and Lower Mississippian(?) Kanayut Conglomerate, Brooks Range, Alaska: U.S. 

Geological Survey Bulletin 1529-A, p. A1-A64. 

Type section: Prominent cliff south of the confluence of Kayak and 

Alapah Creeks, about 8 km south-southeast of Shainin Lake, sec. 4, 

T. 14 S., R. 5 E., Chandler Lake quadrangle, Alaska. 

Rocks previously designated the informal middle conglomerate 

member of the Kanayut Conglomerate are here named the Shainin Lake 

Member of the now revised Kanayut Conglomerate in the central and 

eastern Brooks Range, Alaska. Consists of fining-upward thick-bedded 

couplets of conglomerate and sandstone and little or no shale. Forms a 

broad wedge- to lens-shaped body, probably deposited by braided 

streams on a broad plain, that pinches out toward the west and south 
284 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

into the gradationally underlying Ear Peak Member (new name) and 

gradationally overlying Stuver Member of the Kanayut. Thickness at 

the type section is 526 m. Age is Late Devonian based on stratigraphic 

position. 

Shale Hill Formation of the Pleasanton Group 

late Pennsylvanian (Missourian) 

Missouri 

Forest City basin 

Howe, W.B., 1982, Stratigraphy of the Pleasanton Group, Pennsylvanian System in 

Missouri: Missouri Department of Natural Resources, Open File Report Series 

OFR-82-10-GI, 99 p. 

Type section: Midland Brick and Tile Company quarry on Shale Hill, 

NEl/4SEl/4 sec. 18, T. 57 N., R. 24 W., north of Utica, Chillicothe 

15-minute quadrangle, Livingston County, Mo. 

Subunits: Weldon River Sandstone Member, Knobtown Limestone 

Member, Blue Mound Shale Member. 

The Shale Hill Formation, here named, is the youngest of three 

formations in the Pleasanton Group in the Forest City basin in northwestern Missouri. Outcrops extend from Bates County northeastward 

to Adair and Putnam Counties. Includes the basal Weldon River 

Sandstone Member (new name), consisting of channel- and valley-fill 

sandstone, shale, and conglomerate; the Knobtown Limestone. Member, 

consisting of littoral sandy limestone facies; and the upper Blue Mound 

Shale Member (new name), consisting of coal beds, underclay, and 

shale. Unconformably overlies the Unity Farm Shale Member (new 

name) of the Lees Summit Formation (new name); underlies rocks of the 

Kansas City Group. Thickness ranges from about 20 ft to more than 100 

ft. Age is Late Pennsylvanian (early Missourian). 

Sheephead Andesite 

Miocene 

California 

Great Basin province 

Wright, L.A., Kramer, J.H., Thornton, C.P., and Troxel, B.W., 1984, Appendix I-Type 

sections of two newly named volcanic units of the central Death Valley volcanic field, 

eastern California, in Wright, L.A., and Troxel, B. W., Geology of the northern half of 

the Confidence Hills 15-minute quadrangle, Death Valley region, eastern California: 

the area of the Amargosa chaos: California Division of Mines and Geology Map Sheet 

34, p. 21-24. 

Type section: Composite of exposures extending for 12 km along the 

lower southwest sides of Salsberry Peak and Sheephead Mountain, from 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 285 

Rhodes Wash eastward to Salsberry Pass in the Black Mountains, 

Confidence Hills and Shoshone 15-minute quadrangles, Inyo County, 

Calif. 

The Sheephead Andesite, here named, is in the Black Mountains, 

central Death Valley volcanic field, California. Consists of a lower unit 

of pale-red to grayish-red, vesicular andesite containing plagioclase 

phenocrysts and a basal flow breccia, 150 m thick; a poorly sorted 

volcaniclastic breccia unit, 3 to 10 m thick; and an upper pale-red to 

grayish-red, much less porphyritic andesite unit comprising a single 

flow, 60 m thick. Conformably overlies the Rhodes Tuff (new name); 

underlies the Shoshone Volcanics. Thickness is 210 m at Sheephead 

Mountain. Age is Miocene based on potassium-argon ages of 10.4 Ma for 

underlying dacitic flows and 8. 7 to 7.6 Ma for overlying Shoshone 

Volcanics. 

Sheep Spring Rhyolite 

Oligocene 

Nevada 

Great Basin province 

Hose, R.K., 1983, Geologic map of the Cockalorum Wash quadrangle, Eureka and Nye 

Counties, Nevada: U.S. Geological Survey Miscellaneous Investigations Map 1-1410, 

scale 1:31,680. 

Type section: Exposures on the west side of Ninemile Canyon, sees. 16 

and 17, T. 15 N., R. 51 E., Cockalorum Wash 15-minute quadrangle, 

Eureka County, Nev. Named for Sheep Spring along the upper reaches 

of Ninemile Canyon. 

The Sheep Spring Rhyolite, here named, is in the Antelope Range, 

Nev. Consists of several flows of brown, flow-banded, stony rhyolite 

having feldspar phenocrysts in a groundmass of devitrified glass, and 

contains lenticular bodies of black vitrophyre. Unconformably overlies 

rocks of Ordovician and Silurian age on erosional surfaces of considerable topographic and structural relief; unconformably underlies the 

Mulligan Canyon Rhyolite (new name). Thickness reaches 400 m. Age is 

Oligocene based on potassium-argon ages of 37 and 36.5 Ma. 

Shelley Peak Tuff 

Oligocene 

New Mexico 

Basin and Range province 

Ratte, J.C., 1981, Geologic map of the Mogollon quadrangle, Catron County, New Mexico: 

U.S. Geological Survey Geologic Quadrangle Map GQ-1557, scale 1:24,000. 

Type section: SEl/4 sec. 11, T. 13 S., R. 17 W., Shelley Peak quadrangle, 

Catron County, N. Mex. Reference sections: Sl/2 sec. 31, T. 8 S., 
286 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

R. 20 W., and SEl/4 sec. 7, T. 9 S., R. 20 W., both in the Saliz Pass 

quadrangle. Named for Shelley Peak, Catron County. 

The Shelley Peak Tuff, here named in Catron County, N.Mex., was 

formerly mapped as part of the Pacific Quartz Latite of Ferguson 

(1927). Consists of brick-red, compositionally zoned, crystal-rich, rhyolite ash-flow tuff. Contains sodic plagioclase and sanidine phenocrysts 

and accessory biotite, opaque oxides, green clinopyroxene, zircon, 

oxyhornblende, apatite, and sphene. Overlies the Davis Canyon Tuff 

(new name) or unnamed lava flows; underlies the Bloodgood Canyon 

Tuff or unnamed lava flows. Thickness is 200 m in the Shelley Peak 

quadrangle and 50 to 60 m in the Mogollon quadrangle. Age is Oligocene 

based on a zircon fission-track age of 28 Ma. 

Shellrock Point Volcanics 

Tertiary 

Washington 

Northern Cascade Range-Okanogan province 

Menzer, F.J., Jr., 1983, Metamorphism and plutonism in the central part of the Okanogan 

Range, Washington: Geological Society of America Bulletin, v. 94, no. 4, p. 471-498. 

Type locality: Shellrock Point on U.S. Highway 97 between Okanogan 

and Omak, T. 33 N., R. 26 E., Okanogan Range, Okanogan County, 

Wash. 

The Shellrock Point Volcanics, here named, are exposed on Pogue 

Mountain and Pogue Flat in the Okanogan Range, Wash. Consists of 

quartz keratophyre flows containing medium-grained phenocrysts of 

quartz and pink albite in a dense white to pale-green groundmass. May 

be older than the Miocene Columbia River Basalt; may correlate with 

early Tertiary keratophyre flows to the north. 

Shelton Member of the Trap Falls Formation 

Early or Middle Ordovician 

Connecticut 

New England province 

Rodgers, John, 1985, Bedrock geological map of Connecticut: Connecticut Geological and 

Natural History Survey, scale 1:125,000. 

Type locality: None designated. Described in the Shelton anticline in 

the Long Hill 7.5-minute quadrangle, Fairfield County, Conn. 

(Crowley, 1968). 

Rocks mapped as the Shelton facies of the Trap Falls Formation by 

Crowley (1968) are here named the Shelton Member of the Trap Falls in 

the Hartland belt of the Connecticut Valley synclinorium. Consists of 

white, light-gray, or buff, fine- to medium-grained, foliated granitic 

gneiss composed of sodic plagioclase, quartz, microcline, muscovite, and 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 287 

garnet in tiny grains, interlayered with mica schist, biotite, gneiss, and 

calc-silicate rock. Is thought to be the metavolcanic equivalent of 

granitic gneiss that has been termed Ansonia, Mine Hill, Tyler Lake, 

and Siscowit gneiss. Age is Early or Middle Ordovician. 

Shelvin Rock Church Formation of the Sylacauga Marble 

Group 

Cambrian 

Alabama 

Piedmont-Blue Ridge province 

Tull, J.F., 1985, Stratigraphy of the Sylacauga Marble Group, in Tull, J.F., Bearce, D.N., 

and Guthrie, G.M., eds., Early evolution of the Appalachian miogeocline: upper 

Precambrian-lower Paleozoic: Alabama Geological Society guidebook, 22d annual field 

trip, November 22-23, 1985, p. 21-26. 

Type locality: Exposures in hills around Shelvin Rock Qhurch, 6 km 

west of Sylacauga, NWl/4 sec. 4, T. 22 S., R. 3 E., Talladega County, 

Ala. 

The Shelvin Rock Church Formation of the Sylacauga Marble 

Group, as revised by Tull (1982), here named, is in the Talladega slate 

belt, Alabama. Consists of interlayered pink and white pelitic marble 

and locally carbonaceous gray calcareous phyllite. Overlies the Fayetteville Phyllite (new name) and underlies the Gooch Branch Chert (new 

name), both of the Sylacauga Marble Group. Correlates with the 

Cambrian Conasauga Formation and possibly with the upper part of the 

Rome Formation and the lower part of the Knox Group. Age is 

Cambrian. 

Shepherd Mountain Rhyolite of the St. Francois Mountains 

Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: Sec. 31, T. 34 N., R. 4 E., Ironton quadrangle, Iron 

County, Mo. Exposed on Shepherd Mountain and Pond Ridge northwest of Ironton. 

Rocks previously called Pilot Knob Felsite by Tolman and 

Robertson (1969) are here named the Shepherd Mountain Rhyolite in 

the western St. Francois Mountains, southeast Missouri. Consists of 

brick-red to dark-maroon ash-flow tuff containing white to pink plagioclase phenocrysts and fiamme. Is the oldest unit in the area; underlies 
288 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

the Cedar Bluff Rhyolite (new name). Thickness is 600 m. Age is Middle 

Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E.B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Shepherd Mountain Rhyolite. 

Signal Granite 

Precambrian 

Arizona 

Plateau sedimentary province 

Lucchitta, Ivo, and Suneson, Neal, 1982, Signal Granite (Precambrian), west-central 

Arizona: U.S. Geological Survey Bulletin 1529-H, p. H87-H90. 

Type locality: Exposures in the northern part of the Artillery Mountains between the ghost town of Signal, SWl/4 sec. 9, T. 13 N., R. 13 W., 

and Eagle Point, El/2 sec. 7, T. 12 N., R. 13 W., Artillery Peak 

15-minute quadrangle, Mohave County, Ariz. 

A granitic batholith, at least 30 km in diameter, exposed in the 

northern part of the Artillery Mountains, Ariz., is here named the 

Signal Granite. Consists of gray, leucocratic to mesocratic, massive, 

locally jointed, spheroidally weathered, medium- to coarse-grained, 

porphyritic biotite granite or monzogranite. Is cut by veins of quartz, 

pegmatite, and aplite and by dikes of diabase, metarhyolite porphyry, 

and leucogranite. On the north the pluton is intrusive into gneiss, schist, 

and plutonic country rock typical of the Precambrian terrane of the 

southwestern Colorado Plateau; on the south it is sheared and altered 

and may form the proto lith of the mylonitic quartz-feldspar gneiss of the 

Rawhide Mountains. The eastern contact is unknown; the western 

contact is poorly exposed and structurally complex. Age is Precambrian 

based on its similarity to other granites of known Precambrian age in 

Arizona. 

Silver Cliff Member of the Kewaunee Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 289 

Type section: Road cut at the crest of the Inner Mountain moraine on 

the north side of Eagle River Road, SWV4SWV4SWV4 sec. 9, T. 34 N., 

R. 18 E., Roaring Rapids 7.5-minute quadrangle, Marinette County, 

Wis. Named for the Township of Silver Cliff. 

Following the informal usage of McCartney (1979), the Silver Cliff 

Member of the Kewaunee Formation (new name) is here named. Occurs 

on the west side of the Green Bay Lobe in Wisconsin. Consists of 

reddish-brown sand-silt-clay till and is thin, discontinuous, and poorly 

exposed. Unconformably overlies pre-Pleistocene bedrock or older till 

of the Horicon Formation (new name); unconformably underlies the 

Kirby Lake or Middle Inlet Members (both new names) of the 

Kewaunee, or is the surface unit. Contact with the equivalent Branch 

River and Ozaukee Members (both new names), both of the Kewaunee, 

on the east side of the Green Bay Lobe is an arbitrary vertical contact 

at the Fox River. Thickness at the type section is 2 m. Age is 

Pleistocene (late Wisconsinan). 

Silverdale Formation 

Miocene 

North Carolina 

Atlantic Coast basin 

Baum, G.R., Harris, W.B., and Zullo, V.A., 1978, Stratigraphic revision of the exposed 

middle Eocene to lower Miocene formations of North Carolina: Southeastern Geology, 

v. 20, no. 1, p. 1-19. 

Type section: Exposures in a quarry located at the intersection of 

County Roads 1434 and 1442, east of the city of Silverdale, Onslow 

County, N.C. 

The Silverdale beds of Vokes (1967), here named the Silverdale 

Formation, are exposed only in quarries in a structural basin delineated 

by the Neuse fault to the northeast and the New River to the southwest 

in North Carolina. Represents a downdip offshore facies of the laterally 

equivalent Belgrade Formation and consists of a basal dense, sandy, 

pelecypod-mold biomicrudite grading upward into unconsolidated 

sandy, pelecypod biomicrudite. Disconformably overlies the Trent 

Formation; disconformably underlies the Crassostrea gigantissima 

facies oyster channels. Age is early Miocene. 
290 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Silver Lake Metavolcanic Rocks of the Phantom Lake 

Metamorphic Suite 

Archean 

Wyoming 

Green River basin 

Flurkey, A.J., Houston, R.S., Karlstrom, K.E., and Kratochvil, T.L., 1981, The geology 

of Archean and Early Proterozoic terranes of the Sierra Madre, Wyoming, in 

Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, eds., A summary of the 

geology and uranium potential of Precambrian conglomerates in southeastern Wyoming: U.S. Department of Energy National Uranium Resource Evaluation, v. 1, pt. 3, 

p. 403-531. 

Type area: Cliffs between South Spring Creek Lake and Silver Lake, 

Sierra Madre, Carbon County, Wyo. 

The Silver Lake Metavolcanic Rocks, here named in the Phantom 

Lake Metamorphic Suite in the Sierra Madre, include the informal 

Silver Lake conglomerate and Spring Lake volcanics of Graff (1978), 

here combined because of their interbedded relationship in outcrop. 

Consists of mafic and ultramafic(?) metavolcanic rocks, granite boulder 

paraconglomerate, biotite schist, metagraywacke, metatuff, quartzite, 

and metacarbonate. Rapid lateral and vertical facies changes are 

common and suggest deposition of sediments as alluvial fans, deltas, 

mud flows, or turbidity currents in an environment of scattered volcanic 

centers erupting flows and tuffs into surrounding basins. Overlies the 

Jack Creek Quartzite (new name) and underlies the Bridger Peak 

Quartzite, both of the Phantom Lake. Thickness is 300 m. Age is 

Archean. 

Singer Peak Formation of the Deep Lake Group 

Early Proterozoic 

Wyoming 

Green River basin 

Flurkey, A.J., Houston, R.S., Karlstrom, K.E., and Kratochvil, T.L., 1981, The geology 

of Archean and Early Proterozoic terranes of the Sierra Madre, Wyoming, in 

Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, eds., A summary of the 

geology and uranium potential of Precambrian conglomerates in southeastern Wyoming: U.S. Department of Energy National Uranium Resource Evaluation, v. 1, pt. 3, 

p. 403-531. 

Type area: None designated. Occurs in the Sierra Madre, Carbon 

County, Wyo. Derivation of name not stated. 

Rocks informally named the Singer Peak Formation by Graff (1978) 

and rocks assigned by him to the overlying Campbell Lake. Formation 

extended from the Medicine Bow Mountains are here named the Singer 

Peak Formation of the Deep Lake Group in the Sierra Madre, Wyo. Is 

interpreted to be an offshore marine facies of fluvialglacial units in the 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 291 

Medicine Bow Mountains. Consists of phyllite containing minor amounts 

of quartzite and a paraconglomerate layer near the top. Interfingers 

with the Magnolia Formation of the Deep Lake Group in the Dexter 

Peak area, but the contact is more obscure elsewhere; underlies the 

Cascade Quartzite of the Deep Lake. Correlates with the Lindsey 

Quartzite and Campbell Lake Formation of the Deep Lake Group in the 

Medicine Bow Mountains. Thickness ranges from 0 m in the east to 831 

m in the west. Age is Early Proterozoic. 

Six Lakes Limestone Member of the Hemlock Lake Formation 

of the Saginaw Group 

Early Pennsylvanian (Morrowan) 

Michigan 

Michigan basin 

Vugrinovich, Ray, 1984, Lithostratigraphy and depositional environments of the Pennsylvanian rocks and the Bayport Formation of the Michigan basin: Michigan Geological 

Survey Division, Report of Investigation 27, 33 p. 

Type section: Michigan Consolidated Gas Company Number SL-425 

well, NWV4NWV4SEV4 sec. 13, T. 12 N., R. 7 W., Belvidere Township, 

Montcalm County, Mich. Named for Six Lakes gas storage field in 

Montcalm County. 

The informal cream limestone of Tyler (1980) is here named the Six 

Lakes Limestone Member in the lower part of the Hemlock Lake 

Formation of the Saginaw Group in the subsurface of the Michigan 

basin. Consists of white to yellowish-gray to light-brown micritic 

limestone containing anhydrite, gypsum, and crystals of metallic 

sulfides. Is widespread in the western part of the Hemlock Lake study 

area and ranges from 0 to 30 ft thick. Age is Early Pennsylvanian 

(Morrowan). 

Slade Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R. 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Southwestern high wall of Nat ural Bridge Stone Company 

quarry near the Mountain Parkway, about 6.5 km northwest of Slade, 

Powell County, Ky. 
292 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Subunits: 

Lower part: Renfro, St. Louis, Ste. Genevieve, Warix Run, Mill 

Knob Members. 

Upper part: Cave Branch Bed, Armstrong Hill, Holly Fork, 

Rosslyn, Tygarts Creek, Ramey Creek, Maddox Branch, Poppin 

Rock Members. 

The Slade Formation, here named, includes Upper Mississippian 

rocks of the Cumberland Escarpment outcrop belt in east-central and 

northeastern Kentucky, extending to the northern boundary of Kentucky, that formerly were named the Newman Limestone, now 

restricted from that area. Is divided into a lower part that includes the 

Renfro, St. Louis, Ste. Genevieve, Warix Run (new name), and Mill 

Knob (new name) Members and consists of thin- to thick-bedded 

carbonate units commonly bounded by disconformities and subaerialexposure surfaces; and an upper part that includes the previously 

named Cave Branch Bed and the Armstrong Hill, Holly Fork, Rosslyn, 

Tygarts Creek, Ramey Creek, Maddox Branch, and Poppin Rock 

Members (all new names) and consists of thin- to thick-bedded carbonate units interbedded with shale. Conformably underlies or intertongues with the Paragon Formation (new name) or disconformably 

underlies the Paragon, Lee, or Breathitt Formations in the north. 

Thickness at the type section is 44 m; maximum thickness is 100 m at the 

arbitrary southwestern limit of the formation, where equivalent units 

are the Muldraugh Member of the Borden Formation and the Salem, 

Warsaw, St. Louis, Monteagle, Hartselle, and Bangor Formations. Age 

is Late Mississippian. 

Slate Peak Member of the Virginian Ridge Formation 

Cretaceous (Albian to Cenomanian) 

Washington 

Northern Cascade Range-Okanogan province 

Trexler, J.H., Jr., 1985, Sedimentology and stratigraphy of the Cretaceous Virginian 

Ridge Formation, Methow Basin, Washington: Canadian Journal of Earth Sciences, v. 

22, no. 9, p. 1274-1285. 

Type section: Type section of Virginian Ridge Formation, the Virginian 

Ridge-Wolf Creek trail section of Barksdale (1975), 8 km west of 

Winthrop, sees. 35 and 36, T. 35 N., R. 20 E., Methow Basin, Okanogan 

County, Wash. Named for Slate Peak, T. 37-38 N., R. 17-18 E., 

Okanogan County. 

The Slate Peak Member of the Virginian Ridge Formation, here 

named, is in the Methow Basin, the southernmost of a series of Mesozoic 

basins that rest with angular disconformity on older rocks in 

the Cascades, north-central Washington. Consists of thin-bedded, 

lithic sandstone, siltstone, and argillite containing thin chert-pebble 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 293 

conglomerate beds. Unconformably overlies the Harts Pass Group in 

the north-central part of the basin or gradationally overlies the Patterson Lake Member (new name) of the Virginian Ridge in the southern 

part of the basin; interfingers with and gradationally underlies the 

Devil's Pass Member (new name) of the Virginian Ridge along the 

western margin of the basin or conformably underlies the Winthrop 

Formation in the east. Thickness ranges from 1,000 min the western 

part to 300 m in the eastern part of the basin. Age is Cretaceous (Albian 

to Cenomanian) based on fossils. 

Sleeping Buffalo Rhyolite 

Miocene 

Arizona 

Basin and Range province 

Creasey, S.C., Peterson, D.W., and Gambell, N.A., 1983, Geologic map of the Teapot 

Mountain quadrangle, Pinal County, Arizona: U.S. Geological Survey Geologic Quadrangle Map GQ-1559, scale 1:24,000. 

Type locality: Exposures on and near The Sleeping Buffalo, a hill in 

sees. 3, 4, T. 3 S., R. 12 E., Teapot Mountain 7.5-minute quadrangle, 

Pinal County, Ariz. 

Subunit: Arnett Member. 

The Sleeping Buffalo Rhyolite, here named, is in the Teapot 

Mountain quadrangle, Pinal County, Ariz. Contains porphyritic rhyolite 

flows, intrusive rocks, and breccias, including the Arnett Member (new 

name), a unit of light-gray to buff flow-banded rhyolite, and an informal 

tuff member that is a buff, yellow, or brown, locally well-bedded, 

water-deposited tuff having a thickness of 0 to 120 m. One mass is a plug 

that grades from intrusive to flow and includes agglomerates, glass 

borders, autobreccia, flow layering, and pumice. Flows are locally 

glassy, perlitic, and devitrified. Rhyolite contains phenocrysts of plagioclase, quartz, sanidine, biotite, and magnetite in a glassy, devitrified or 

aphanitic groundmass. Conformably overlies older Tertiary tuff; unconformably underlies the Road Runner Rhyolite (new name). Age is 

Miocene based on potassium-argon ages of 18 to 15.9 Ma for rhyolite in 

the Mineral Mountain quadrangle to the west. 

Slide Member of the Chuckanut Formation 

Eocene 

Washington 

Bellingham basin 

Johnson, S.Y., 1984, Stratigraphy, age, and paleogeography of the Eocene Chuckanut 

Formation, northwest Washington: Canadian Journal of Earth Sciences, v. 21, no. 1, 

p. 92-106. 
294 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Composite of exposures on logging road S-1000 on Slide 

Mountain, sees. 4 and 9, T. 39 N., R. 6 E.; logging road 400 on the 

southeast side of Canyon Creek north of the North Fork Nooksack 

River, Wl/2 sec. 36, T. 40 N., R. 6 E.; and logging road SP-410 on the 

northeast side of Canyon Creek, SEl/4 sec. 25, T. 40 N., R. 6 E., 

Whatcom County, Wash. 

The Slide Member of the Chuckanut Formation, here named, is in 

the eastern part of the largest outcrop belt of the Chuckanut, which 

extends from the San Juan Islands into the foothills of the North 

Cascades, Wash. Consists of fining-upward cycles of lower coarsegrained units of arkosic sandstone and upper fine-grained units of 

mudstone and minor amounts of coal and sandstone, that are interpreted as meandering river and adjacent flood-plain deposits. Overlies 

the Bellingham Bay Member (new name); interfingers with the Padden 

Member (new name) to the west and is in fault contact with preTertiary rock to the east; underlies the Warnick and Maple Falls 

Members (new names), all of the Chuckanut Formation. Thickness is 

1,960 m at the type section. Age is middle Eocene based on zircon 

fission-track ages of the Bellingham Bay and Padden Members. 

Smith Gut Member of the Flanner Beach Formation 

Pleistocene 

North Carolina 

Atlantic Coast basin 

Miller, William, III, 1985, The Flanner Beach Formation (middle Pleistocene) in eastern 

North Carolina: Tulane Studies in Geology and Paleontology, v. 18, no. 3, p. 93-122. 

Type section: Measured section SG1, bluffs on the north bank of the 

Neuse River, 3.4 km southeast of the mouth of Beard Creek and 0.3 km 

northwest of Smith Gut, Cherry Point 7.5-minute quadrangle, Pamlico 

County, N.C. 

Basal transgressive beds of the Flanner Beach Formation exposed 

in the Neuse River valley of the North Carolina Coastal Plain are here 

named the Smith Gut Member. Consists of an irregular blanket-shaped 

deposit of olive-brown to greenish-gray, pebbly, shelly, muddy sand. 

Disconformably overlies the James City Formation; gradationally 

underlies the Arapahoe Sand, Beard Creek, and Newport Sand Members (all new names) of the Flanner Beach Formation. Thickness is 0.5 

m at the type section. Age is middle Pleistocene. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 295 

Smoke Creek Bed of the Windom Shale Member of the 

Moscow Formation of the Hamilton Group 

Middle Devonian 

New York 

Appalachian basin 

Baird, G. C., and Brett, C. E., 1983, Regional variation and paleontology of two coral beds 

in the Middle Devonian Hamilton Group of western New York: Journal of Paleontology, v. 57, no. 3, p. 417-446. 

Type section: Exposures on the bank of the south branch of Smoke 

Creek, 0.25 mi south of Mile Strip Road at Windom, (Windom Shale 

Member type section), Buffalo SE 7.5-minute quadrangle, Erie County, 

N.Y. 

The Coral-trilobite bed of Brett (1974) is here named the Smoke 

Creek Bed of the Windom Shale Member of the Moscow Formation of 

the Hamilton Group. Extends from Lake Erie east to Canandaigua 

Valley, New York, and consists of hard, calcareous mudstone. Overlies 

the Bay View Coral Bed (new name) in the lower part of the Windom; 

underlies the Fall Brook Coral Bed (new name) of the Windom. 

Thickness is 25 to 40 em. Age is Middle Devonian. 

Smugglers Pass Formation of the Thunderbird Group 

Precambrian 

Texas 

Orogrande basin 

Thomann, W.F., 1981, Ignimbrites, trachytes, and sedimentary rocks of the Precambrian 

Thunderbird Group, Franklin Mountains, El Paso County, Texas: Geological Society of 

America Bulletin, v. 92, no. 2, pt. I, p. 94-100. 

Type section: Exposure 3,000 ft northeast of Smugglers Pass in 

Fusselman Canyon, Franklin Mountains, lat 31°53'06" N., long 

106°29'34" W., El Paso County, Tex. 

The Smugglers Pass Formation is here named the middle of three 

formations in the Thunderbird Group (new name) in the Franklin 

Mountains, Tex. Consists of four units: a lowermost dark-gray to 

olive-black, melanocratic porphyritic trachyte unit as much as 150 ft 

thick; a grayish-red porphyritic trachyte unit as much as 200 ft thick; a 

tuffaceous sandstone and conglomerate unit as much as 90 ft thick; and 

an uppermost silicified ignimbrite as much as 20 ft thick. Overlies the 

Coronado Hills Conglomerate (new name) and underlies the Tom Mays 

Park Formation (new name), both of the Thunderbird Group. Thickness 

is about 1,800 ft at the type section. Age is late Precambrian (950 Ma). 
296 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Snellville Formation 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Large roadcut outcrops on Lanier Mountain, Snellville 

quadrangle, Gwinnett County, Ga. Named for exposures within the city 

limits of Snellville. 

Subunits: Norris Lake Schist Member, Lanier Mountain Quartzite 

Member. 

The Snellville Formation, here named, is in the Newnan-Tucker 

synform near Atlanta, Ga., and includes the lower Norris Lake Schist 

Member (new name) and the upper Lanier Mountain Quartzite Member 

(new name). Discordantly overlies the Lithonia Gneiss and the Wolf 

Creek, Clairmont, and Wahoo Creek Formations (all new names) of the 

Atlanta Group (new name) and is probably younger than the Atlanta 

Group. The lower contact is either a folded thrust contact or a folded 

angular unconformity. Is intruded by the Stone Mountain and Panola 

Granites (325 Ma). Age is Late Proterozoic and (or) early Paleozoic 

based on an age of 1,100 Ma of detrital zircons from the Lanier Mountain 

Quartzite Member. 

Snowcrest Range Group 

Late Mississippian and Early Pennsylvanian (Meramecian, Chesterian, 

Morrowan) 

Montana 

Montana folded belt province 

Wardlaw, B.R., and Pecora, W.C., 1985, New Mississippian-Pennsylvanian stratigraphic 

units in southwest Montana and adjacent Idaho, in Sando, W.J., ed., Mississippian and 

Pennsylvanian stratigraphy in southwest Montana and adjacent Idaho: U.S. Geological 

Survey Bulletin 1656-B, p. B1-B9. 

Type area: Snowcrest Range, Beaverhead and Madison Counties, 

Mont. 

Subunits: Kibbey Sandstone, Lombard Limestone, Conover Ranch 

Formation 

Rocks in southwest Montana formerly assigned to the Big Snowy 

Group and Amsden Formation are here named the Snowcrest Range 

Group. Includes the basal Kibbey Sandstone, reassigned in this area 

from the Big Snowy Group, the Lombard Limestone (new name), and 

the upper Conover Ranch Formation (new name). The Kibbey consists 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 297 

of yellow siltstone, sandstone, and mudstone; the Lombard consists of a 

lower unit of lime-mudstone and packstone and an upper unit of 

lime-mudstone, wackestone, and packstone; the Conover Ranch consists of mudstone containing minor amounts of limestone and sandstone. 

Overlies the McKenzie Canyon Limestone (new name) of the Tendoy 

Group (new name) in the Tendoy Range, and the Mission Canyon 

Limestone of the Madison Group elsewhere; underlies and intertongues 

with the Quadrant Sandstone. Age is Late Mississippian and Early 

Pennsylvanian (middle Meramecian to early Morrowan) based on conodont, foraminifer, coral, and brachiopod faunas. 

Snow Flake Formation 

Mississippian 

Tennessee 

Appalachian basin 

Brent, W. B., 1982, Mississippian stratigraphy of Greendale and Newman Ridge synclines 

and Middle Ordovician nomenclature in upper east Tennessee: Tennessee Division of 

Geology Report of Investigations 41, 37 p. 

Type section: South side of county road, 1. 6 km northeast of the locality 

of Snow Flake, 2.8 km east of Looneys Gap in Clinch Mountain, Looneys 

Gap quadrangle, Hawkins County, Tenn. 

The Snow Flake Formation, informally named by Sanders (1952), is 

here named. These Mississippian strata in the Greendale syncline in 

Hawkins and Grainger Counties, Tenn., were previously named the 

Newman Limestone by Hardeman and others (1966) but are isolated 

from the type Newman Limestone in the Newman Ridge syncline. 

Consists of fossiliferous, calcareous shale, silty shale, and limestone. 

Overlies the Laurel Branch Limestone (new name); underlies the 

Clifton Creek Limestone (new name). Thickness is 36 m. Age is 

Mississippian. 

Soapstone Ridge Complex 

Paleozoic(?) 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Soapstone Ridge, just south of South River, Atlanta, 

Southeast Atlanta quadrangle, De Kalb County, Ga. 
298 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Soapstone Ridge Complex, here named, is in the NewnanTucker synform near Atlanta, Ga. Consists of metamorphosed mafic 

and ultramafic igneous rocks and is divided into six major lithologic 

units: basal sillimanite-quartz blastomylonite and epidosite, actinolitechlorite-talc schist, interlayered metamorphosed mafic and ultramafic 

rocks, mixed amphibolite and actinolite-chlorite-talc schist, amphibolite, and metatroctolite. Is a multiply folded remnant of a disrupted 

ophiolite complex no more than 200 m thick, emplaced by low-angle 

thrusting in the early Middle Ordovician, and has many erosional 

windows exposing rocks of the Big Cotton Indian Formation (new 

name) of the Atlanta Group (new name). Age is early Paleozoic(?). 

Socorro Peak Rhyolite of the Santa Fe Group 

Miocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type area: On and south of Socorro Peak, 3 mi west and southwest of 

Socorro in a belt extending from the summit of Socorro Peak southward 

to the Grefco perlite mine, sees. 5, 8, 16, 17, 21, and 28, T. 3 S., R. 1 W., 

Socorro 7.5-minute quadrangle, Socorro County, N. Mex. 

The Socorro Peak Rhyolite of the Santa Fe Group, here named, is in 

the Orogrande basin, New Mexico. Includes the informal rhyolite of 

Pound Ranch. Consists of rhyodacite and rhyolite domes and flows 

containing minor amounts of pyroclastic rocks. Overlies fanglomerate 

and playa mudstones of the Popotosa Formation and is interbedded with 

upper Popotosa mudstone. Age is Miocene based on potassium-argon 

dates of 12.1 Ma for Strawberry Peak, 10.8 Ma for Signal Flat Hill, 10.6 

Ma for Stonewall Hill, 10.3 Ma for 6001 Mesa, 9.2 Ma for 6633 Peak, and 

4.5 Ma for Radar Peak, all of which are rhyolite domes. 

Soda Lake Bed of the Carson Desert Formation 

Pleistocene and Holocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Measured section 10 of Morrison (1964), bluff on the 

southeast side of Soda Lake, Carson Desert, SWlf4SWlf4 sec. 8, T. 19 N., 

R. 28 E., Churchill County, Nev. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 299 

The Soda Lake Bed of the Carson Desert Formation (new name), 

here named, is in the Carson Desert of the Lake Lahontan area, 

Nevada. Brown tephra of the Soda Lake Bed are found only at the Soda 

Lake vent and are distinguishable from the older tephra of the U psal 

Hogback Bed (new name) of the Carson Desert Formation under the 

microscope only by the larger olivine crystals and lower refractive index 

of the Soda Lake. Upsal Hogback and Soda Lake vents may have shared 

the same magma source. Age is Pleistocene and Holocene, 11 to 6 ka. 

Solomon Temple Member of the Dox Formation of the Unkar 

Group 

Middle Proterozoic 

Arizona 

Plateau sedimentary province 

Stevenson, G.M., and Beus, S.S., 1982, Stratigraphy and depositional setting of the upper 

Precambrian Dox Formation in Grand Canyon: Geological Society of America Bulletin, 

v. 93, no. 2, p. 163-173. 

Type section: Exposures 2.4 km northeast of Solomon Temple, a 

prominent butte in the eastern Grand Canyon, Vishnu Temple quadrangle, Coconino County, Ariz. 

The Solomon Temple Member of the Dox Formation of the Unkar 

Group, here named, is in the eastern Grand Canyon, Ariz. Consists of a 

lower unit exposed as a monotonous slope-forming sequence of alternating red to reddish-brown, fine-grained sandstone and red to maroon, 

laminated, shaly, micaceous siltstone, 215m thick; and an upper unit, a 

complex of dark-red, fine-grained, micaceous channel sandstones, 66 to 

122 m thick. Is interpreted as a flood-plain complex grading upward into 

migrating fluvial or tidal-channel or point-bar deposits. Gradationally 

overlies the Escalante Creek Member (new name), and underlies the 

Comanche Point Member (new name), both of the Dox Formation. 

Thickness is 280 m at the type section. Age is Middle Proterozoic based 

on the age of the overlying Cardenas Lavas (1.1 Ma). 

South Canyon Tuff 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: Exposures on the northwest side of the mouth of South 

Canyon, 12 mi southwest of Socorro, SWV4 sec. 30, T. 3 S., R. 2 W., 

Magdalena SE 7.5-minute quadrangle, Socorro County, N. Mex. 
300 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Rocks formerly called Potato Canyon Rhyolite Tuff, now abandoned, are here named the South Canyon Tuff. Occurs in the northeast 

Mogollon-Datil volcanic field, except for the Datil area, northern 

Gallinas Mountains, and Bear Mountains. Is divided into lower and 

upper members and consists of a simple to compound thick and 

continuous cooling unit of crystal-poor to moderately crystal-rich, 

quartz-rich, rhyolite ash-flow tuff. Overlies the Lemitar Tuff (new 

name) and tongue "c" of the La Jara Peak Basaltic Andesite; underlies 

the Popotosa Formation. Thickness attains 650 ft. Age is Oligocene 

based on a potassium-argon date of 26.7 Ma on biotite. 

South Crosby Peak Formation 

Oligocene 

New Mexico 

Orogrande basin 

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast 

Mogollon-Datil volcanic field, New Mexico: New Mexico Bureau of Mines and Mineral 

Resources Stratigraphic Chart 1. 

Type section: Exposure 1.8 mi northeast of South Crosby Peak and 4.3 

mi southwest of Datil, NEl/4 sec. 19, T. 2 S., R. 10 W., eastern Crosby 

Mountains, Sugarloaf Mountain 7.5-minute quadrangle, Catron County, 

N.Mex. 

Rocks formerly called the tuff of Crosby Mountain and volcaniclastic 

rocks of South Crosby Peak are here named the South Crosby Peak 

Formation. Occurs in the eastern Crosby and Datil Mountains and in the 

Jornada del Muerto, N. Mex. Consists of grayish-pink, medium- to 

coarse-grained, tuffaceous volcaniclastic sandstone and conglomerate 

and pale-pink, unwelded to poorly welded, crystal poor, ash-flow tuff. 

Overlies the Hells Mesa Tuff; underlies the La J encia Tuff (new name). 

Thickness at the type section is 595 ft and ranges from 0 to 200 ft in the 

Datil and western Gallinas Mountains. Age is Oligocene. 

South Fork Member of the Snowshoe Formation 

Middle jurassic (Bathonian) 

Oregon 

Snake River basin 

Smith, P.L., 1980, Correlation of the members of the Jurassic Snowshoe Formation in the 

Izee basin of east-central Oregon: Canadian Journal of Earth Sciences, v. 17, no. 12, 

p. 1603-1608. 

Type section: Type section of the Snowshoe Formation, South Fork of 

the John Day River near the former community of Izee, Izee 15-minute 

quadrangle, Grant County, Oreg. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 301 

Rocks previously described by Dickinson and Vigrass (1965) as the 

upper member of the Snowshoe Formation are here named the South 

Fork Member of the Snowshoe in the Mowich upwarp of the John Day 

inlier in Washington. Consists of thin-bedded, dark mudstone and 

siltstone containing beds of gray, calcareous sandstone. Laminations 

and crossbedding indicate turbidite deposition. Unconformably overlies 

the Schoolhouse Member (new name) or the Silvies Member of the 

Snowshoe; unconformably underlies the Trowbridge Formation. Thickness is 500 m at Lewis Creek and thins southward. Age is Middle 

Jurassic (Bathonian). 

South Mountains Granodiorite 

Tertiary 

Arizona 

Basin and Range province 

Reynolds, S.J., 1985, Geology of the South Mountains, central Arizona: Arizona Bureau 

of Geology and Mineral Technology Bulletin 195, 61 p. 

Type locality: Exposures along Summit Road, 500 m northeast of 

Telegraph Pass, Main Ridge of the South Mountains, Maricopa County, 

Ariz. Reference localities are designated. 

The South Mountains Granodiorite, here named, comprises most of 

the eastern half of the Main Ridge and Southern Foothills of the South 

Mountains near Phoenix, Ariz. Consists of gray, medium-grained, 

equigranular to slightly porphyritic granodiorite and contains numerous 

comagmatic aplitic dikes. Mylonitic fabric is present in most exposures 

and is darker due to streaking of biotite and a reduction in grain size. 

Chloritic breccia and micro breccia occupy zones of intense deformation. 

Is the oldest of three phases of a composite pluton and grades into or is 

intruded by the second phase Telegraph Pass Granite (new name). 

Underlies the third phase Dobbins Alaskite (new name) in places. 

Intrudes the overlying Precambrian Estrella Gneiss (new name) along a 

subhorizontal contact where it is strongly mylonitic. Age is middle 

Tertiary. 

Spickert Knob Formation of the Borden Group 

Early Mississippian (Keokuk) 

Indiana 

Cincinnati arch 

Rexroad, C.B., and Lane, N.G., 1984, Spickert Knob Formation (new), Borden Group, in 

Indiana: Indiana Geological Survey Occasional Paper 43, 4 p. 

Type section: Outcrops along Spickert Knob Road and in adjacent 

ravines to the northeast in the NEl/4 sec. 21 and SEl/4 sec. 16, T. 2 S., 

R. 6 E., New Albany 7.5-minute quadrangle, Floyd County, Ind. 
302 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Spickert Knob Formation of the Borden Group, here named, 

was described in Floyd County, Ind., where the name was used by 

Stockdale (1931) for a facies of the Locust Point Formation. The Locust 

Point and Carwood Formations of the Borden Group do not have a 

recognizable mutual boundary that consistently separates them outside 

their type areas, and together they represent parts of a depositional 

event that resulted in a single mappable unit, designated the Spickert 

Knob Formation. The Locust Point and Carwood cannot be mapped 

separately and are abandoned. The Spickert Knob consists of silty 

shale, siltstone, sandstone, and lenticular limestone. Gradationally 

overlies the Kenwood Member of the New Providence Shale; gradationally underlies the Floyds Knob Limestone Member of the Edwardsville 

Formation. Thickness at the type section is 238 ft. Age is Early 

Mississippian (Keokuk) based on fossils. 

Spieden Bluff Formation of the Spieden Group 

Late jurassic (Oxfordian or Kimmeridgian) 

Washington 

Puget Sound province 

Johnson, S. Y., 1981, The Spieden Group: An anomalous piece of the Cordilleran 

paleogeographic puzzle: Canadian Journal of Earth Sciences, v. 18, no. 11, 

p. 1694-1707. 

Type section: Spieden Bluff, north end of Spieden Island, sec. 2, 

T. 37 N., R. 4 W., San Juan Islands, San Juan County, Wash. 

The Spieden Bluff Formation of the Spieden Group, here named, is 

in the San Juan Islands, Wash. Includes a lower member consisting of 

structureless, fine-grained sandstone and crystal tuff,-. 5 m thick, 

overlain by volcanic breccia-conglomerate, 75 m thick; and a gradationally overlying upper member consisting of gray, fine- to mediumgrained, fossiliferous sandstone and siltstone, 20 m thick. Strata were 

deposited in subaerial and shallow marine environments near an active 

volcanic source. Base is not exposed; disconformably underlies the 

Sentinel Island Formation (new name) of the Spieden Group, with a 

hiatus spanning 20 to 30 million years. Age is Late Jurassic (Oxfordian 

or Kimmeridgian) based on fossils. 

Spillville Formation 

Middle Devonian (Eifelian) 

Iowa, Minnesota 

Iowa shelf 

Klapper, Gilbert, and Barrick, J.E., 1983, Middle Devonian (Eifelian) conodonts from the 

Spillville Formation in northern Iowa and southern Minnesota: Journal of Paleontology, v. 57, no. 6, p. 1212-1243. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 303 

Type section: Abandoned quarry at Spillville (Pavlovec's Spillville 

quarry), SEl/4 sec. 20, T. 97 N., R. 9 W., Fort Atkinson quadrangle, 

Winneshiek County, Iowa. 

Basal Middle Devonian strata in northern Iowa and southern 

Minnesota, previously correlated with the Solon Member of the Cedar 

Valley Formation in east-central Iowa, are here named the Spillville 

Formation. Can be distinguished from the Solon Member because it is 

consistently a yellowish-orange to grayish-orange, medium- to finegrained, fossiliferous, calcareous dolostone sequence containing sandstone or sandy carbonate developed locally at the base. Late Eifelian 

conodonts in the lower part suggest a correlation with the lower part of 

the Coggon Member of the Wapsipinicon Formation. Unconformably 

overlies the Maquoketa Shale; underlies a clastic interval correlated 

with the Kenwood Member of the Wapsipinicon. The clastic interval 

underlies a unit that is the lithostratigraphic equivalent of the combined 

Spring Grove and Davenport Members of the Wapsipinicon, and this 

unit underlies the informal Salisbury beds, which may correlate with 

the Solon Member of the Cedar Valley Formation. Thickness at the type 

section is 18 m. Age is Middle Devonian (Eifelian). 

Split Rock Creek Formation 

late Cretaceous 

South Dakota 

Sioux uplift 

Ludvigson, G.A., McKay, R.M., Iles, D., and Bretz, R.F., 1981, Lithostratigraphy and 

sedimentary petrology of the Split Rock Creek Formation, Late Cretaceous of 

southeastern South Dakota: Iowa Geological Survey Guidebook Series 4, p. 77-104. 

Type section: None designated. Named for exposures along cut banks of 

Split Rock Creek, Minnehaha County, S. Dak. Principal surface and 

subsurface sections designated. 

The Split Rock Creek Formation, here named, occurs in an 80 mi2 

area in the Sioux uplift of southeastern South Dakota. Is a basin-fill 

shallow water facies equivalent of a marine unit, probably the Niobrara 

Formation. Consists of sandy diamictites and friable quartz sandstone 

overlain by dark-gray, laminated, organic claystone that grades upward 

into opaline spiculite and massive chert. Contains land plant debris, 

fossils, and Precambrian rock detritus. Unconformably overlies late 

Precambrian Sioux Quartzite or, locally, Corson Diabase. Maximum 

thickness is about 300 ft. Age is Late Cretaceous based on regional 

relationships and fossil evidence, including sequoia twig molds, teleost 

fish scales, sponge spicules, radiolaria, gastropods, foraminifera, 

pelecypods, and crustaceans. 
304 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Springhill Pond Formation of the Lake George Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: None designated. Occurs in the eastern Adirondack 

Mountains, N.Y. Origin of name not stated. 

The name Springhill Pond Formation of Walton and de Waard (1963) 

is here assigned to the Lake George Group (new name) in the eastern 

Adirondack Mountains in New York. Consists of garnet-sillimanite 

gneiss, quartzite, and marble. Alling (1917) divided the sequence, from 

base to top, into tentative units: Hague gneiss, Dixon schist, Faxon 

limestone, Swede Pond quartzite, (Bryant Lake) limestone, Catamount 

sillimanite schist, and Bear Pond schist. Structurally overlies the Lake 

Durant Formation; structurally underlies the Thunderbolt Mountain 

Formation (new name), both of the Lake George Group. Correlates with 

the Blue Mountain Lake Formation of the central Adirondacks. Age is 

Proterozoic. [Although this name has not been formally proposed, it is 

included here because of its continued usage.] 

Spruce Creek Formation 

Cretaceous 

Alaska 

Yukon-Koyukuck province 

Sainsbury, C.L., 1974, Geologic map of the Bendeleben quadrangle, Seward Peninsula, 

Alaska: U.S. Bureau of Mines, U.S. Geological Survey, and The Mapmakers, 31 p., 

scale 1:150,000. 

Type locality: Exposures at the head of Spruce Creek, a southwest 

tributary of Independence Creek, a tributary of the Kugruk River, 

Bendeleben quadrangle, Seward Peninsula, Alaska. 

The Spruce Creek Formation, here named, is in the area along the 

east front of the Darby Mountains and northward along the Kugruk 

River, Seward Peninsula, Alaska. Consists of thick cobble conglomerate 

containing clasts of limestone and dolomite, Jurassic volcanic rocks, 

chloritic schist, and York Slate (new name). Weathers to bare hills 

covered by cobbles. Unconformably overlies Jurassic metavolcanic 

rocks or Paleozoic carbonate rocks; underlies a thrust sheet of Paleozoic 

rocks. Maximum thickness is at least 200 ft, but much has been removed 

by erosion. Age is Cretaceous. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 305 

Stage Crossing Gneiss 

Archean 

Wyoming 

Green River basin 

Karlstrom, K.E., Houston, R.S., Coolidge, C.M., Flurkey, A.J., and Sever, C.K., 1981, 

The geology of Archean and Early Proterozoic terraines of the Medicine Bow 

Mountains, Wyoming, in Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, 

eds., A summary of the geology and uranium potential of Precambrian conglomerates 

in southeastern Wyoming: U.S. Department of Energy National Uranium Resource 

Evaluation, v. 1, pt. 2, p. 197-399. 

Type area: Northern Medicine Bow Mountains, Carbon County, Wyo. 

Named for the Overland Trail stage crossing of Rock Creek, near 

Arlington. 

The Stage Crossing Gneiss, here named, is in the northern Medicine 

Bow Mountains, Wyo. Consists of hornblende gneiss and minor amounts 

of metasedimentary biotite gneiss. Gradationally underlies or may be in 

fault contact with the Stud Creek Volcaniclastic Rocks (new name) of 

the Phantom Lake Metamorphic Suite. Maximum thickness is 1,200 m 

but is probably much less because of repetition by folding. Age is 

Archean because it is cut by granite similar to the Baggot Rocks Granite 

(2,500 to 2,400 Ma). 

Stage Road Layered Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Sinha, A.K., and Bartholomew, M.J., 1984, Evolution of the Grenville terrane in the 

central Virginia Appalachians: Geological Society of America Special Paper 194, 

p. 175-186. 

Type section: Outcrops on U.S. Highway 29, 50 m west of its intersection with Virginia State Road 617, lat 37°51' N., long 78°48' W., 

Lovingston 7.5-minute quadrangle, Rockbridge County, Va. Origin of 

name not stated. 

The Stage Road Layered Gneiss, here named, is in the Lovingston 

massif and includes augen gneisses and schists of the old Lovingston 

Formation of Jonas (1935). Consists of augen gneiss, biotite gneiss, and 

layered schists and gneisses. Age is Middle Proterozoic based on 

concordia intercept ages of 1,870 to 915 Ma. 
306 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Station Hills Phyllite Member of the Popes Head Formation 

Late Proterozoic and (or) Early Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., and Lyttle, P.T., 1981, The Accotink Schist, Lake Barcroft Metasandstone, and Popes Head Formation-Keys to an understanding of the tectonic evolution 

of the northern Virginia Piedmont: U.S. Geological Survey Professional Paper 1205, 

16 p. 

Type locality: Exposures along the tracks of the Southern Railroad, 

from a point about 350 m west of Station Hills to a point about 900 m 

east of that village, Fairfax 7.5-minute quadrangle, Fairfax County, Va. 

The Station Hills Phyllite Member of the Popes Head Formation 

(new name), here named, is in Fairfax County, Va. Consists of 

light-greenish-gray, dusky-yellow-weathering phyllite and lesser finegrained metasiltstone occupying the core of the Popes Head synform in 

the Wissahickon terrane. Conformably overlies the Old Mill Branch 

Member (new name) of the Popes Head; is intruded by the Occoquan 

Granite. Maximum exposed thickness is about 300 m, but the top of the 

unit is covered. Age is Late Proterozoic and (or) Early Cambrian based 

on a radiometric age of Early Cambrian for the Occoquan Granite. 

Stephens Forest Formation of the Marmaton Group of the 

Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Center of the east line, NWl/4 sec. 18, T. 72 N., R. 22 W., 

Lucas County, Iowa. Named for Stephens State Forest, 1.5 mi southwest of the town of Lucas. 

Subunits: Little Osage Shale Member, Houx Limestone Member, 

Higginsville Limestone Member. 

The Stephens Forest Formation, here named, is in the Marmaton 

Group of the Des Moines Supergroup in southeastern and central Iowa. 

Includes in ascending order the revised Little Osage Shale Member, the 

Houx Limestone Member, an unnamed shale member, and the Higginsville Limestone Member. Consists of fissile, black phosphatic shale; 

calcareous, green-brown, fossiliferous shale; light-gray, silty shale; and 

light-gray, fine-grained, fossiliferous limestone. Encompasses the 

marine portion of the upper depositional cycle of the Marmaton. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 307 

Overlies the Summit Coal Member (new name) of the Morgan School 

Shale (new name) and underlies the Labette Shale, both of the Marmaton Group. Thickness is 11.5 ft at the type section. Age is Middle 

Pennsylvanian (Desmoinesian). 

Stewarts Knob Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Outcrop along the Blue Ridge Parkway, 0.5 mi north of 

its junction with Virginia Highway 24, Stewartsville 7.5-minute quadrangle, Bedford County, Va. 

The Stewarts Knob Gneiss, here named, is in the Pedlar massif in 

the Blue Ridge in Virginia. Consists of small intrusive bodies of 

light-gray to white porphyroblastic biotite-garnet leucogneiss with 

associated nelsonite dikes. Age is late Middle Proterozoic. 

St. Francis Till 

Pleistocene (Wisconsinan) 

Maine 

New England province 

Genes, A.N., Newman, W.A., and Brewer, T.B., 1981, Late Wisconsinan glaciation 

models of northern Maine and adjacent Canada: Quaternary Research, v. 16, no. 1, 

p. 48-65. 

Type locality: Exposures in river bluffs at Golden Rapids, Rankin 

Rapids, and Hammond Brook along the St. John River, Aroostook 

County, Maine. [Probably named for the town of St. Francis near 

Rankin Rapids.] 

The oldest Pleistocene sediments in Aroostook County, Maine, 

exposed by the downcutting of the St. John River to bedrock, are here 

named the St. Francis Till. Consists of compact, silty to clayey, 

dark-gray till containing clasts derived from the underlying Seboomook 

Formation, 3.0 to 3.6 m thick, overlain by outwash or boulder pavement 

of similar lithology, 3.0 to 5.0 m thick, or stratified sediments associated 

with younger drift. Correlates with the middle Wisconsinan Chaudiere 

Till and Gay hurst Formation of southeastern Quebec. Unconformably 

underlies the Van Buren Till (new name) along the St. John River. Age 

is Pleistocene (middle Wisconsinan). 
308 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

St. Francois Mountains Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E.B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

Type area: St. Francois Mountains, southeast Missouri. 

Subunits: Shepherd Mountain Rhyolite, Cedar Bluff Rhyolite, Pond 

Ridge Rhyolite, Buck Mountain Shut-ins Formation, Ironton Rhyolite, 

Lindsey Mountain Rhyolite, Russell Mountain Rhyolite, Wildcat Mountain Rhyolite, Bell Mountain Rhyolite, Royal Gorge Rhyolite, Taum 

Sauk Rhyolite, Proffit Mountain Formation, Johnson Shut-ins Rhyolite, 

Cope Hollow Formation. 

The formal name St. Francois Mountains Volcanic Supergroup is 

here adopted for all the Precambrian volcanic rocks of the St. Francois 

Mountains in southeast Missouri. Includes the units defined by Berry 

(1976) in the western part of the St. Francois Mountains, listed above. 

All are new names except the revised Royal Gorge Rhyolite. Age is 

Middle Proterozoic. 

Stonewall Formation of the Atlanta Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Exposures in and around the community of Stonewall, 

Fairburn quadrangle, Fulton County, Ga. 

The Stonewall Formation of the Atlanta Group (new name), here 

named, is in the Newnan-Tucker synform near Atlanta, Ga., and 

consists of medium-grained biotite gneiss and fine-grained hornblendeplagioclase amphibolite interlayered with sillimanite-biotite schist. 

Sharply and conformably overlies the Wahoo Creek Formation (new 

name), and sharply and conformably underlies the Clarkston Formation 

(new name), both of the Atlanta Group. Thickness ranges from 1,000 to 

1,500 m. Age is Late Proterozoic and (or) early Paleozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 309 

Stratford Mountain Till 

Pleistocene (Wisconsinan) 

New Hampshire 

New England province 

Koteff, Carl, and Pessl, Fred, Jr., 1985, Till stratigraphy in New Hampshire: Correlations 

with adjacent New England and Quebec, in Borns, H.W., Jr., and others, eds., Late 

Pleistocene history of northeastern New England and adjacent Quebec: Geological 

Society America Special Paper 197, p. 1-12. 

Type locality: Composite of exposures along Nash Stream, Coos 

County, N.H. Named for nearby Stratford Mountain. 

The upper till at Nash Stream in northern New Hampshire is here 

named the Stratford Mountain Till. Consists of light-olive-gray, loose to 

moderately compact, sandy till containing clasts of Ordovician and 

Devonian quartz monzonite, schist, and phyllite. Is oxidized to a depth 

of 1 m. Unconformably overlies the Nash Stream Till (new name) or 

sharply truncated glaciolacustrine outwash; underlies fluvial outwash. 

Correlates with surface tills throughout New England and with the 

Lennoxville Till in Quebec. Age is late Pleistocene (late Wisconsinan) 

based on its similarity to other surface tills. 

Stroudsburg Member of the Buttermilk Falls Limestone 

Middle Devonian (Onesquethawan and Cazenovian) 

Pennsylvania 

Appalachian basin 

Epstein, J.E., 1984, Onesquethawan stratigraphy (Lower and Middle Devonian) of 

northeastern Pennsylvania: U.S. Geological Survey Professional Paper 1337, 35 p. 

Type section: Railroad cut of Erie-Lackawanna Railroad, nearly 1 mi 

south of East Stroudsburg Post Office, Stroudsburg 7.5-minute quadrangle, Monroe County, Pa. Named for Stroudsburg, Pa. 

The upper member of the Buttermilk Falls Limestone in the 

Godfrey Ridge area, Monroe County, Pa., is here named the Stroudsburg Member. Consists of irregularly bedded, medium-gray, fossiliferous, fine- to medium-grained, locally argillaceous limestone and darkgray to grayish-black chert in irregular beds, lenses, and pods. 

Gradationally overlies the McMichael Member (new name) of the 

Buttermilk Falls; the upper boundary is not exposed but is probably in 

abrupt contact with the Union Springs Shale Member of the Marcellus 

Shale. The Tioga Ash Bed, which crops out 27 ft below the top of the 

member, marks the top of the Onesquethawan Stage. The upper 27ft of 

the Stroudsburg is Cazenovian and correlates with the Seneca Member 

of the Onondaga Limestone. Thickness is 149ft. Age is Middle Devonian 

(Onesquethawan and Cazenovian). 
310 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Stuart Creek Gneiss 

Middle Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Conley, J.F., 1985, Geology of the southwestern Virginia Piedmont: Virginia Division of 

Mineral Resources Publication 59, 33 p. 

Type locality: Exposures along both sides of Stuart Creek, from State 

Road 632, northwest for 2 mi, Spray 7.5-minute quadrangle, Henry 

County, Va. 

Granitic augen gneiss that occupies the cores of four structural 

domes in the Sauratown Mountains anticlinorium in Virginia is here 

named the Stuart Creek Gneiss. Texture varies from porphyroblastic 

gneiss to augen gneiss and flaser gneiss. Unconformably underlies 

metasedimentary rocks correlated with the Lynchburg Group. Age is 

Middle Proterozoic based on similar rocks dated at 1,192 Ma. 

Stud Creek Volcaniclastic Rocks of the Phantom Lake 

Metamorphic Suite 

Archean 

Wyoming 

Green River basin 

Karlstrom, K.E., Houston, R.S., Coolidge, C.M., Flurkey, A.J., and Sever, C.K., 1981, 

The geology of Archean and Early Proterozoic terraines of the Medicine Bow 

Mountains, Wyoming, in Karlstrom, K.E., Houston, R.S., Flurkey, A.J., and others, 

eds., A summary of the geology and uranium potential of Precambrian conglomerates 

in southeastern Wyoming: U.S. Department of Energy National Uranium Resource 

Evaluation, v. 1, pt. 2, p. 197-399. 

Type locality: Outcrops near Stud Creek, sec. 15, T. 18 N., R. 79 W., 

Medicine Bow Mountains, Carbon County, Wyo. 

The Stud Creek Volcaniclastic Rocks, here named, is the oldest unit 

of the Phantom Lake Metamorphic Suite in the Medicine Bow Mountains, Wyo. Crops out in the core of the overturned, doubly plunging 

French J oes anticlinorium near Stud Creek in the south and Rock 

Mountain in the north. Consists of a heterogeneous assemblage of 

metavolcanic and metasedimentary rocks lumped into four groups: 

pelitic schists, amphibolitic schists, quartzites and conglomerates, and 

calcareous rocks. Depositional environments ranged from fluvial to 

shallow marine but subaerial deposition and volcanism may have 

predominated. Stratigraphic relationships with the underlying Stage 

Crossing Gneiss (new name) and the overlying Rock Mountain Conglomerate (new name) of the Phantom Lake are complicated and may be 

in part gradational. Overall thickness is difficult to estimate because of 

isoclinal folds and the inferred presence of large strike faults, but 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 311 

maximum exposed stratigraphic thickness ranges from 330 m in the 

north to 500 m in the south. Age is Archean. 

Stumptown Member of the Nassawadox Formation 

Pleistocene 

Virginia 

Atlantic Coast basin 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of uppermost Cenozoic 

deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological 

Survey Professional Paper 1067-G, 53 p. 

Type section: Borehole Ch-11, lower 141 ft of Nassawadox Formation 

type section, east end of Route 648, 0.5 mi east of Stumptown, west of 

Penn Central Railroad branch line, 10 mi south-southwest of the town of 

Nassawadox, Cheriton 7.5-minute quadrangle, Northampton County, 

Va. 

The Stumptown Member, here named the lower member of the 

Nassawadox Formation (new name), fills the Eastville paleovalley in 

the subsurface of the Franktown plain and central upland south of the 

Ames Ridge shoreline in Northampton County, Va. Consists of sandy 

gravel, clay-silt, and muddy, fine sand that form three distinct lithofacies, named units A, B, and C. Unconformably overlies the Eastover 

or Yorktown Formations; conformably to disconformably underlies the 

Butlers Bluff Member (new name) of the Nassawadox. Thickness at the 

type section is 140 ft. Age is Pleistocene. 

Summit Coal Member of the Morgan School Shale of the 

Marmaton Group of the Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: None designated. First described in Macon County, Mo. 

(McGee, 1885). 

The Summit Coal Member, here named, is at the top of the Morgan 

School Shale (new name) of the Marmaton Group and was described as 

the Summit coal in Missouri by McGee (1885). Is poorly developed in 

Iowa, usually as a smut zone. Consists of black, carbonaceous shale 

with alternating bands of vitrain and calcareous fossil debris. Underlies 

the Stephens Forest Formation (new name). Correlates with the 
312 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Springfield (Number 5) coal of northwestern Illinois. Thickness is 8 in. at 

the Morgan School Shale type section. Age is Middle Pennsylvanian 

(Desmoinesian). 

Summit-Frazer Trondhjemitic Gneiss 

Mississippian 

Washington 

Northern Cascade Range-Okanogan province 

Menzer, F.J., Jr., 1983, Metamorphism and plutonism in the central part of the Okanogan 

Range, Washington: Geological Society of America Bulletin, v. 94, no. 4, p. 471-498. 

Type area: Roadcuts along the Loup Loup Pass Highway (Washington 

State Highway 20), T. 33-34 N., R. 23-24 E., western part of the 

Okanogan Range, Okanogan County, Wash. Named for Summit and 

Frazer Creeks. 

Premetamorphic basement gneisses in the western part of the 

Okanogan Range, Wash., are here named the Summit-Frazer Trondhjemitic Gneiss. Main phase includes 95 percent of the batholith and 

consists of trondhjemitic orthogneiss with metamorphic textures resulting from Mesozoic metamorphism. Older inclusion phase along the 

eastern margin contains altered metasedimentary and xenoliths of 

igneous rocks. Coyote Ridge quartz dioritic gneiss phase is a border 

phase in the southwestern part of the area. Represents a premetamorphic granitic basement mobilized as a gneiss dome during Mesozoic 

regional metamorphism. Intrudes the older Leecher Metamorphics on 

the west side; is intruded by the early Mesozoic Leader Mountain 

Granodioritic Gneiss and the Late Cretaceous Conconully Granodiorite 

(new name). Age is pre-Late Mississippian. 

Summit Island Formation 

Late Cretaceous 

Alaska 

Bristol Bay basin 

Hoare, J.M., Coonrad, W.L., and McCoy, Scott, 1983, Summit Island Formation, a new 

Upper Cretaceous formation in southwestern Alaska: U.S. Geological Survey Bulletin 

1529-B, p. B1-B18. 

Type section: Exposures in the sea cliffs on the northwest end of 

Summit Island, sec. 25, T. 15 S., R. 66 W., Togiak Bay, Hagemeister 

Island D-1 quadrangle, Alaska. 

The Summit Island Formation, here named, in southwestern 

Alaska, includes nonmarine strata that were previously included in the 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 313 

Gemuk Group and in an unnamed unit thought to include strata of 

Cretaceous and early Tertiary age. Consists of thick-bedded conglomerate, sandstone, siltstone, and carbonaceous mudstone that has carbonized plant material and a few thin coal seams. Beds are folded and 

faulted. Lies with angular(?) unconformity on highly deformed older 

Mesozoic rocks; underlies Tertiary volcanic rocks with angular unconformity. No complete section is exposed; thickness is 850 m at the type 

section. Age is Late Cretaceous, probably Maastrichtian, based on 

palynomorphs, fossil leaves, and the radiometric age of a dike that cuts 

the unit. 

Surprise Canyon Formation 

late Mississippian (Chesterian) and Early Pennsylvanian(?) 

(Morrowan(?)) 

Arizona 

Plateau sedimentary province 

Billingsley, G.H., and Beus, S.S., 1985, The Surprise Canyon Formation-An Upper 

Mississippian and Lower Pennsylvanian(?) rock unit in the Grand Canyon, Arizona: 

U.S. Geological Survey Bulletin 1605-A, p. A27-A33. 

Type section: 1.6 km west of the Colorado River (mi 263), 2.4 km 

southwest of the mouth of Tincanebits Canyon, and 2.4 km southeast of 

Bat Tower viewpoint, lat 36° N., long 113°48' W., western Grand 

Canyon, Amos Point quadrangle, Mohave County, Ariz. Named for 

Surprise Canyon, 18 km east of the type section. 

Rocks previously considered to be part of the Redwall Limestone 

and the Watahomigi Formation, or part of a valley-fill sequence 

between the Redwall and Watahomigi, are here named the Surprise 

Canyon Formation. Crops out in isolated patches throughout much of 

the Grand Canyon and part of Marble Canyon to the northeast. Consists 

of fossiliferous nonmarine and marine sediments and is subdivided into 

a basal nonmarine unit of white, yellow, and red, chert cobble and 

pebble conglomerate, dark-gray to red-brown, medium- to coarsegrained, locally cross-stratified calcareous sandstone, and medium- to 

fine-grained siltstone; and an upper marine unit of brown to yellowgray, coarse-grained, fossiliferous, cliff- and ledge-forming limestone 

overlain by red-brown, thin-bedded, ripple-laminated, slope-forming 

sandstone and siltstone. Cuts into and through the Mooney Falls and 

Horseshoe Mesa Members of the Redwall Limestone; unconformably 

underlies the Watahomigi Formation. Thickness is 91 m at the type 

section. Age is Late Mississippian (Chesterian) and locally Early 

Pennsylvanian(?) (Morrowan(?)) based on fossil spores, foraminifers, 

and corals. 
314 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Swamp Creek Member of the Saddle Mountains Basalt of the 

Columbia River Basalt Group 

Miocene 

Idaho 

Idaho Mountains province 

Camp, V.E., 1981, Geologic studies of the Columbia Plateau: Part II. Upper Miocene 

basalt distribution, reflecting source locations, tectonism, and drainage history in the 

Clearwater embayment, Idaho: Geological Society of America Bulletin, v. 92, no. 9, pt. 

I, p. 669-678. 

Type locality: Swamp Creek, North Fork of the Clearwater River, 

Clearwater County, Idaho. 

The Swamp Creek Member of the Saddle Mountains Basalt of the 

Columbia River Basalt Group, here named, is in the upper North Fork 

area of the Clearwater embayment, Idaho. Consists of medium- to 

coarse-grained olivine basalt containing abundant olivine phenocrysts. 

Lies above the basalt of Weippe of the Pomona Member of the Saddle 

Mountains. Age is late Miocene. 

Swede Hollow Formation of the Cherokee Group of the 

Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade,J.W., Howes, M.R., Gregory,J.L., Anderson, R.R., and VanDorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Exposures along a tributary to Whitebreast Creek in 

Swede Hollow, sees. 33 and 34, T. 73 N., R. 22 W., and sec. 3, T. 72 N., 

R. 22 W., Lucas County, Iowa. 

Subunits: Whitebreast Coal Member, Oakley Shale Member, Ardmore 

Limestone Member, Wheeler Coal Member, Bevier Coal Member, 

Mulkey Coal Member. 

The Swede Hollow Formation, here named, is the uppermost of four 

newly named formations of the Cherokee Group of the Des Moines 

Supergroup in southeastern and south-central Iowa. Includes in ascending order the basal Whitebreast Coal Member (new name), the Oakley 

Shale Member (new name), the Ardmore Limestone Member, the 

Wheeler Coal Member (new name), the Bevier Coal Member, extended 

from Missouri, and the Mulkey Coal Member, extended from Missouri. 

Represents a period of alternating marine and nonmarine cyclothemic 

deposition of limestones and shales characterized by laterally persistent, thin beds and uniform thickness. Forms the boundary between the 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 315 

Cherokee and Marmaton Groups; overlies the Floris Formation (new 

name) of the Cherokee; underlies the Excello Shale Member of the 

Mouse Creek Formation (new name) of the Marmaton. Thickness at the 

type section is 107 ft and averages 100 ft. Age is Middle Pennsylvanian 

(Desmoinesian). 

Sweetwater Creek Formation of the Great Smoky Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.l., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures along Sweetwater Creek on Lake Allatoona, 

South Canton 7.5-minute quadrangle, Cherokee County, Ga. 

The Sweetwater Creek Formation of the Great Smoky Group, here 

named, is in the Murphy synclinorium in the Greater Atlanta region, 

Georgia. Consists of poorly sorted, coarse, blue-quartz conglomeratic 

sandstone and graphitic phyllite. Gradationally overlies the Etowah 

Formation (new name) of the Great Smoky, and the boundary is placed 

where coarse clastics constitute more than 50 percent of the unit; 

gradationally underlies the Dean Formation. Age is Late Proterozoic 

and (or) early Paleozoic. 

Swisher Mountain Tuff 

Miocene 

Idaho 

Snake River basin 

Ekren, E.B., Mcintyre, D.H., and Bennett, E.H., 1984, High-temperature, largevolume, lavalike ash-flow tuffs without calderas in southwestern Idaho: U.S. Geological 

Survey Professional Paper 1272, 76 p. 

Type locality: Exposures on the northern wall of Wood Canyon, on the 

road between the De Lamar open-pit silver mine, Idaho, and the village 

of Jordan Valley, Oreg., SEl/4 sec. 29, T. 5 S., R. 5 W., Owyhee County, 

Idaho. Named for Swisher Mountain. 

Rocks previously informally named the rhyolite of Poison Creek of 

Neill (1975) and welded tuff number 1 of Bennett (1976) are here named 

the Swisher Mountain Tuff. One or more cooling units of tuff, erupted 

from the Juniper Mountain volcanic center in the Owyhee Plateau of 

southwestern Idaho, have been traced over an area, 100 km in diameter. Consists of bluish- or brownish-gray, reddish-weathering, densely 

welded, calc-alkalic, rhyolite tuff containing phenocrysts of plagioclase, 

alkali feldspar, pigeonite, and hypersthene. Flow-layered and brecciated vitrophyres indicate compound cooling. Tuff was emplaced as high 
316 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

temperature ash flows that coalesced to liquids before final emplacement and cooling. Overlies tuffaceous sedimentary rocks of the Sucker 

Creek Formation; is overlapped to the east by the Little Jacks Tuff (new 

name) and underlies gravel and fanglomerate of Pliocene and Quaternary age. Thickness ranges from 50 to 200 m. Age is Miocene based on 

a potassium-argon age of about 13.8 Ma. 

Switzer Creek Member of the Windsor Township Formation 

Middle Ordovician 

Pennsylvania 

Appalachian basin 

Lash, G.G., and Drake, A.A., Jr., 1984, The Richmond and Greenwich slices of the 

Hamburg klippe in eastern Pennsylvania-Stratigraphy, sedimentology, structure, 

and plate tectonic implications: U.S. Geological Survey Professional Paper 1312, 40 p. 

Type locality: Exposures along Switzer Creek, Topton and Kutztown 

7.5-minute quadrangles, Lehigh County, Pa. 

The Switzer Creek Member of the Windsor Township Formation 

(new name), here named, is in the Greenwich slice of the Hamburg 

klippe in Pennsylvania. Consists of thick-bedded, medium- to coarsegrained, calcareous graywacke interbedded with grayish-green shale, 

and local conglomerate beds that contain shale and limestone clasts. Is 

differentiated from graywacke of the Dreibelbis Member (new name) of 

the Windsor Township by amalgamated sequences and high porosity, 

resulting from weathering of limestone clasts and calcite cement. 

Deposits are turbidite and grain-flow channel facies incised into the 

underlying levee and open-fan mudstones and siltstones of the Weisenberg Member (new name) of the Windsor Township. Minimum thickness 

is 815 m. Age is Middle Ordovician based on graptolites in the 

graywacke. 

Table Top Member of the lake Valley Formation 

Early Mississippian 

New Mexico 

Orogrande basin 

Lane, H.R., and Ornriston, A.R., 1982, Waulsortian facies, Sacramento Mountains, New 

Mexico: Guide for an international field seminar, March 2--6, 1982, in Bolton, Keith, 

Lane, H.R., and LeMone, D.V., eds., Symposium on the paleoenvironmental setting 

and distribution of the Waulsortian facies: El Paso Geological Society and The 

University of Texas at El Paso, p. 115-182. 

Type section: Exposures at the base of Table Top Mountain, 

NWl/4SE1/4NW1/4 sec. 18, T. 19 S., R. 11 E., Otero County, N. Mex. 

Rocks previously assigned to the Arcente Member of the Lake 

Valley Formation are here named the Table Top Member of the Lake 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 317 

Valley in the Sacramento Mountains, N. Mex. Consists of dark-gray, 

argillaceous limestone and calcareous shale, sparsely fossiliferous 

except for a coarse, iron-rich crinoidal packstone occurring at the top of 

the member. Overlies the Alamogordo Member and underlies the 

Arcente Member of the Lake Valley Formation. Thickness at the type 

section is 15 ft. Age is Early Mississippian. 

Tarantula Mesa Sandstone 

Late Cretaceous (Campanian) 

Utah 

Paradox basin 

Smith, Curtis, 1983, Geology, depositional environments, and coal resources of the Mt. 

Penne112 NW quadrangle, Garfield County, Utah: Brigham Young University Geology 

Studies, v. 30, pt. 1, p. 145-167. 

Type section: Outcrops located 1. 6 km southwest of Turn of the 

Bullfrog, below the Frog, NEV4SEV4 sec. 35, T. 33 S., R. 9 E., Mt. 

Pennell2 NW quadrangle, Garfield County, Utah. Named for Tarantula 

Mesa. 

The Tarantula Mesa Sandstone, here named in the Paradox basin, 

Utah, was formerly called the Masuk Sandstone by Gilbert (1877) and 

the Mesaverde Formation by Hunt (1946). Is a braided stream deposit 

and is divided into a lower member consisting of grayish-orange, very 

fine to fine-grained, subangular to angular, moderately well sorted 

sandstone, having quartz and chert as major constituents, and an upper 

member consisting of conglomerate containing well-rounded, poorly 

sorted chert granules, overlain by grayish-orange, fine to mediumgrained, subangular sandstone containing quartz grains. U nconformably overlies the Masuk Shale Member of the Mancos Shale; unconformably underlies beds of late Campanian Age. Correlates with the upper 

sandstone member of the Wahweap Formation on the Kaiparowits 

plateau and with the Castlegate Sandstone and lower part of the Price 

River Formation on the Wasatch plateau. Thickness of the lower 

member ranges from 44.5 mat Spring Canyon to 65.5 mat the type 

section; the upper member ranges from 30m at Spring Canyon to 47 m 

at the type section. Age is Late Cretaceous (late Campanian). 

Tar Creek Member of the Clarkston Formation of the Atlanta 

Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 
318 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type locality: Outcrops along roads around Tar Creek, Fairburn 

quadrangle, Fayette County, Ga. 

The Tar Creek Member is here named the upper member of the 

Clarkston Formation (new name) of the Atlanta Group (new name) in 

the area from East Point to Palmetto, Ga., in the northwest limb of the 

Newnan-Tucker synform. Consists of purple-pink-weathering muscovite schist and ocher-weathering amphibolite and, like the Clarkston 

Formation, is undivided. Gradationally overlies the Fairburn Member 

(new name) of the Clarkston; underlies the Camp Creek Formation 

(new name) with sharp and conformable contact. Is intruded by the 

Union City Complex (new name) and Palmetto Granite. Thickness is 400 

to 1, 500 m. Age is Late Proterozoic and (or) early Paleozoic. 

Taum Sauk Rhyolite of the St. Francois Mountains Volcanic 

Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: Sec. 15, T. 33 N., R. 2 E., Johnson Shut-ins quadrangle, 

Reynolds County, Mo. Exposed on Taum Sauk Mountain. 

Rocks previously called Taum Sauk Mountain ash flows by Anderson 

(1962) and tuff of Taum Sauk Mountain by Anderson (1970) are here 

named the Taum Sauk Rhyolite in the western St. Francois Mountains, 

southeast Missouri. Consists of red to dark-maroon ash-flow tuff 

containing alkali feldspar and quartz phenocrysts and fiamme. Overlies 

the Royal Gorge Rhyolite; underlies the Proffit Mountain Formation 

(new name). Thickness is greater than 1,000 m, but total thickness is 

unknown because the unit is not exposed continuously through its total 

thickness or may be faulted. Age is Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E.B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66--80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Taum Sauk Rhyolite. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 319 

Taunton Beds of the Windom Shale Member of the Moscow 

Formation of the Hamilton Group 

Middle Devonian 

New York 

Appalachian basin 

Baird, G. C., and Brett, C.E., 1983, Regional variation and paleontology of two coral beds 

in the Middle Devonian Hamilton Group of western New York: Journal of Paleontology, v. 57, no. 3, p. 417-446. 

Type section: Exposures in the bed and banks of Taunton Gully, 0.4 km 

west of New York Route 36 overpass near Leicester, Leicester 7.5-

minute quadrangle, Genesee County, N.Y. 

The "Spirifer-coralline" zone of Stover (1956), here named the 

Taunton Beds of the Windom Shale Member of the Moscow Formation 

of the Hamilton Group, is a distinctive and widespread facies in the 

upper part of the Windom in Genesee, Livingston, and Ontario Counties, N.Y. Consists of 5 to 6 m of fossiliferous, calcareous mudstone, too 

thick and variable to be designated a single bed, and contains rugose 

corals, brachiopods, and bryozoa. Overlies the Fall Brook Coral Bed 

(new name) of the Windom. Age is Middle Devonian. 

Telegraph Pass Granite 

Tertiary 

Arizona 

Basin and Range province 

Reynolds, S.J., 1985, Geology of the South Mountains, central Arizona: Arizona Bureau 

of Geology and Mineral Technology Bulletin 195, 61 p. 

Type locality: Exposures along Summit Road, 300m north-northwest of 

Telegraph Pass, near the center of the Main Ridge of the South 

Mountains, Maricopa County, Ariz. Reference localities are designated. 

The Telegraph Pass Granite, here named, is in the Main Ridge and 

Southern Foothills of the South Mountains, near Phoenix, Ariz. Consists of light-gray, medium-grained granite having a variably developed 

mylonitic fabric and inclusions of metamorphic rocks near intrusive 

contacts with the Precambrian Estrella Gneiss (new name). Is the 

second of three phases of a composite pluton that occupies most of the 

eastern half of the range. Grades into or is intruded over the first-phase 

South Mountains Granodiorite (new name); the third-phase Dobbins 

Alaskite (new name) occurs along border zones of the granite. Intrudes 

Estrella Gneiss and intervenes between the Estrella and the South 

Mountains Granodiorite. Age is middle Tertiary. 
320 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Telsitna Formation 

Middle and Late Ordovician 

Alaska 

Holitna basin 

Dutro, J.T., Jr., and Patton, W.W., Jr., 1982, New Paleozoic formations in the northern 

Kuskokwim Mountains, west-central Alaska: U.S. Geological Survey Bulletin 1529-H, 

p. H13-H22. 

Type section: High northeast-trending ridge along the divide between 

the head of the Telsitna River and Paradise Fork, sees. 17, 19, and 20, 

T. 18 S., R. 27 E., Medfra (D-2) quadrangle, Alaska. 

The Telsitna Formation, here named, is the most widely distributed 

unit of the shallow-water carbonate sequence in the Nixon Fork terrane 

of the northern Kuskokwim Mountains, Alaska. At the type section, 

consists of variegated light-gray to dark-brown dolomite beds in the 

lower 300 m; fossiliferous, gray, thin-bedded limestone having silty, 

yellow-weathering interbeds, from 300 to 600 m; nonfossiliferous dolomite, from 600 to 1,000 m; and limestone containing black chert nodules, 

from 1,000 to 1,600 m. Conformably overlies the Novi Mountain 

Formation (new name); disconformably(?) underlies the Whirlwind 

Creek Formation (new name)· or the Paradise Fork Formation (new 

name). Is in fault contact with the East Fork Hills Formation (new 

name) of the East Fork terrane. Total thickness attains 2,000 m. Age is 

Middle and Late Ordovician based on conodonts and other invertebrate 

fossils. 

Tendoy Group 

Early and Late Mississippian (Kinderhookian, Osagean, and 

Meramecian) 

Montana 

Montana folded belt province 

Sando, W.J., Sandberg, C.A., and Perry, W.J., Jr., 1985, Revision of Mississippian 

stratigraphy, northern Tendoy Mountains, southwest Montana, in Sando, W.J., ed., 

Mississippian and Pennsylvanian stratigraphy in southwest Montana and adjacent 

Idaho: U.S. Geological Survey Bulletin 1656-A, p. A1-A10. 

Type section: Composite section measured at Bell Canyon, sec. 17, 

T. 11 S., R. 10 W., and the divide between Bell and McKenzie Canyons, 

sec. 21, T. 11 S., R. 10 W., Tendoy Mountains, Red Rock and Kidd 

7.5-minute quadrangles, Beaverhead County, Mont. 

Subunits: Paine Limestone, Middle Canyon Formation, Mission 

Canyon Limestone, McKenzie Canyon Limestone. 

Rocks formerly assigned to the Madison Group in the northern 

Tendoy Mountains between McKnight Canyon and the Clark Canyon 

Reservoir, southwest Montana, are here named the Tendoy Group. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 321 

Includes the basal Paine Limestone, raised in rank from member to 

formation, the Middle Canyon Formation, extended into Montana from 

Idaho, the Mission Canyon Limestone, and the McKenzie Canyon 

Limestone (new name). Consists mostly of limestone and some chert 

and represents a hitherto unrecognized facies belt near the craton 

margin. Overlies the Three Forks Formation; underlies the Kibbey 

Sandstone, reassigned from the Big Snowy Group to the Snowcrest 

Range Group (new name). Thickness is 810 mat the type section and is 

more than 1, 000 m regionally. Age is Mississippian (Kinderhookian to 

early Meramecian) based on conodonts and corals. 

Ten Mile Member of the Chico Formation 

Late Cretaceous (Campanian) 

California 

Sacramento basin 

Haggart, J.W., and Ward, P.D., 1984, Late Cretaceous (Santonian-Campanian) stratigraphy of the northern Sacramento Valley, California: Geological Society of America 

Bulletin, v. 95, no. 5, p. 618--627. 

Type section: Exposures along Big Chico Creek, sec. 13, T. 23 N., 

R. 2 E., Butte County, Calif. Named for the site of the Ten Mile House 

located along old Highway 32, paralleling Big Chico Creek. 

The Ten Mile Member, informally named by Saul (1961), is here 

named the stratigraphically highest member of the Chico Formation 

along Butte, Big Chico, Deer, and Mill Creeks in Butte and Tehama 

Counties, eastern Sacramento Valley, Calif. Forms tall bluffs and 

consists of greenish-gray to tan, fine-grained, moderately well sorted, 

bioturbated, fossiliferous, silty sandstone containing well preserved 

wood and mollusks in the matrix and as lag deposits. Conformably 

overlies the Musty Buck Member (new name) of the Chico; correlates 

with the middle of the Forbes Formation of the western Sacramento 

Valley. Thickness at the type section is about 575 m. Age is Late 

Cretaceous (early Campanian) based on ammonites. 

Thatcher Till 

Pleistocene (Wisconsinan) 

New York 

Appalachian basin 

Calkin, P.E., Muller, E.H., and Barnes, J.H., 1982, The Gowanda Hospital Interstadial 

Site, New York: American Journal of Science, v. 282, p. 1110-1142. 

Type locality: Exposures along Thatcher Brook at the highway bridge 

1.8 km south of the Gowanda village limit, Erie County, N.Y. 
322 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Thatcher Till, here named, is in Erie County, N.Y. Consists of 

gray clayey-silt till and interbedded stratified gray sand and silt. 

Overlies gravel; underlies silt and fine sand. Thickness is 5.1 m. Age is 

Pleistocene (late Wisconsinan). 

Thatcher Creek Member of the Cool Creek Formation of the 

Arbuckle Group 

Early Ordovician (Canadian) 

Oklahoma 

South Oklahoma folded belt province 

Ragland, D.A., and Donovan, R.N., 1985, The Thatcher Creek Member: Basal unit of the 

Cool Creek Formation in southern Oklahoma: Oklahoma Geology Notes, v. 45, no. 3, 

p. 84-91. 

Type section: Exposure in the valley of Thatcher Creek, a tributary of 

Blue Creek, sec. 11, T. 4 N., R. 13 W., Comanche County, Okla. 

The Thatcher Creek Member of the Cool Creek Formation of the 

Arbuckle Group, here named, is in the Slick Hills, Comanche County, 

Okla. Consists of sandy limestone and blocky, limy sandstone containing 

fine to coarse quartz sand in beds that have parallel laminations, 

crossbedding, and symmetrical ripple marks. Is the basal member of the 

Cool Creek and overlies algal mounds of the McKenzie Hill Formation. 

Deposition was in a high intertidal or supratidal environment that 

inhibited the growth of algal colonies. Thickness is 12 ft at the type 

section. Age is Early Ordovician (Canadian). 

The Forks Formation 

Late Silurian 

Maine 

New England province 

Marvinney, R.G., 1984, The Forks Formation of northwestern Maine: Evidence for a Late 

Ordovician to Late Silurian angular unconformity: Northeastern Geology, v. 6, no. 3, 

p. 151-160. 

Type section: Composite of the (1) west bank of Cold Stream, 200 m 

upstream from its confluence with the Kennebec River and (2) section 

along Moxie Stream from Moxie Falls to northeastward turn 450 m 

upstream, The Forks 7.5-minute quadrangle, Somerset County, Maine. 

Named for the village of The Forks. 

A prominent transgressive rock sequence in northwestern Maine is 

here named the The Forks Formation. Consists of a lower sequence of 

basal conglomerate and carbonate-rich, thin-bedded, silty limestone, 

and an upper sequence of clastic-rich siltstone, sandstone, and phyllite. 

Overlies the Cambrian or Ordovician Dead River Formation with 

angular unconformity, representing Taconian or Penobscottian tectonic 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 323 

events; gradationally underlies the Carrabassett Formation of Early 

Devonian age. Correlates with the Madrid Formation to the southeast. 

Thickness is 215 m. Age is Late Silurian based on estimated sedimentation rates. 

Third Fork Formation 

Early Permian (Wolfcampian) 

Idaho 

Great Basin province 

Mytton, J.W., Morgan, W.A., and Wardlaw, B.R., 1983, Stratigraphic relations of 

Permian units, Cassia Mountains, Idaho, in Miller, D.M., and others, eds., Tectonic 

and stratigraphic studies in the eastern Great Basin: Geological Society of America 

Memoir 157, p. 281--303. 

Type section; Ridge southwest of the confluence of A. H. Creek and 

Third Fork of Rock Creek, Sl/2 sec. 17, T. 14 S., R. 19 E., Pike Mountain 

and Trapper Creek 7.5-minute quadrangles, Cassia County, Idaho. 

The Third Fork sequence of Morgan (1980) is here named the Third 

Fork Formation in the central part of the Cassia Mountains, Idaho, 

where it is exposed in upthrown fault blocks. Consists of gray, buff, and 

pink sandy siltstone, composed of quartz and calcite cement, and three 

distinctive beds of argillaceous spiculitic black lime-mudstone and 

calcareous siltstone, characterized by trace fossils and extensive bioturbation. May be part of the depositional sequence of the northern 

Oquirrh basin. Gradationally overlies the Wahlstrom Hollow Formation 

(new name); gradationally underlies the Badger Gulch Formation (new 

name). Thickness at the type section is 331.2 m. Age is Early Permian 

(late Wolfcampian). The Third Fork and Badger Gulch Formations are 

poorly fossiliferous and difficult to date. The Wolfcampian-Leonardian 

boundary lies within the Third Fork-Badger Gulch sequence and is 

drawn, strictly for convenience, at the Third Fork-Badger Gulch 

contact. 

Thorofare Mountain Formation of the Lynchburg Group 

late Proterozoic 

Virginia 

Piedmont-Blue Ridge province 

Wehr, Frederick, 1985, Stratigraphy of the Lynchburg Group and Swift Run Formation, 

Late Proterozoic (730-570 Ma), central Virginia: Southeastern Geology, v. 25, no. 4, 

p. 225-239. 

Type locality: Exposures on and immediately east of Thorofare Mountain, Brightwood 7.5-minute quadrangle, Madison County, Va. 

The Thorofare Mountain Formation of the Lynchburg Group, here 

named in the Culpeper and Rockfish River areas in Virginia, was 
324 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

previously called the Loudoun Formation and Rockfish Conglomerate in 

the Rockfish River area. Consists of medium-grained to pebbly, poorly 

sorted feldspathic sandstone containing minor amounts of conglomerate, siltstone, and graphitic mudstone. Sharply overlies the Monumental Mills Formation (new name) of the Lynchburg Group in the Culpeper 

area; conformably overlies the Rockfish Conglomerate in the Rockfish 

River area. Unconformably underlies or is in fault contact with the Ball 

Mountain Formation (new name) of the Lynchburg. Age is Late 

Proterozoic based on ages for the Lynchburg Group (730 to 570 Ma) .. 

Thunderbird Group 

Precambrian 

Texas 

Orogrande basin 

Thomann, W.F., 1980, Ignimbrites, trachytes, and sedimentary rocks of the Precambrian 

Thunderbird Group, Franklin Mountains, El Paso, Texas: Geological Association of 

America Bulletin, v. 92, no. 2, pt. I, p. 94-100. 

Type section: Exposure about 3,000 ft northeast of Smugglers Pass in 

Fusselman Canyon, Franklin Mountains, lat 31°53'06" N., long 

106°29'34'' W., El Paso County, Tex. Named for Thunderbird Mountain 

on the southwest flank of South Franklin Mountain. 

Subunits: Coronado Hills Conglomerate, Smugglers Pass Formation, 

Tom Mays Park Formation. 

The sequence of Precambrian volcanic and sedimentary rocks in the 

Franklin Mountains that was previously named the Franklin Mountains 

Rhyolite of Muehlberger and Denison (1964) and the Thunderbird 

rhyolite porphyry of Kottlowski and others (1973) is here named the 

Thunderbird Group. Is divided into three formations on the basis of 

distinct lithology: the lower Coronado Hills Conglomerate (new name); 

the middle Smugglers Pass Formation (new name), composed of volcanic and sedimentary rocks; and the upper Tom Mays Formation (new 

name), composed of rhyolitic ignimbrites. Unconformably overlies the 

Lanoria Quartzite; is intruded by the Red Bluff Granite. Thickness is 

1,200 ft at the type section. Age is late Precambrian (950 Ma), the 

youngest of the Precambrian rocks in the Franklin Mountains. 

Thunderbolt Mountain Formation of the Lake George Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 325 

Type locality: None designated. Occurs in the eastern Adirondack 

Mountains, N.Y. Origin of name not stated. 

The name Thunderbolt Mountain Formation, used by Walton and 

deWaard (1963), is here assigned to the Lake George Group (new name) 

in the eastern Adirondack Mountains, N.Y. Consists of gray-green, 

charnockitic gneiss and pink, granitic gneiss interlayered with amphibolite, garnet granulite, garnet-biotite-quartz-plagioclase gneiss, and 

quartzite. Structurally overlies the Springhill Pond Formation (new 

name) of the Lake George Group and correlates with the Little Moose 

Mountain Formation in the central Adirondacks. Age is Proterozoic. 

[Although this name has not been formally proposed, it is included here 

because of its continued usage.] 

Timber Lake Bed of the Pyramid Lake Member of the Mount 

Mazama Formation 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type Section: Measured section 3 of Morrison (1964), west bank of 

Carson River, 1 km north of Timber Lake, NE1/4NW1/4 sec. 30, T. 21 N., 

R. 30 E., Churchill County, Nev. 

The Timber Lake Bed of the Pyramid Lake Member (new name) of 

the Mount Mazama Formation, here named, is in the Lake Lahontan 

area, Nevada. Is the most phenocryst-rich of the nonbasaltic tephra and 

contains less potassium than any other bed in the Mount Mazama. 

Interfingers with the lower member of the Sehoo Formation. Overlies 

the Carson Sink Bed (new name) of the Mono Basin Formation (new 

name); underlies the Wono Bed (new name) of the Pyramid Lake 

Member. Thickness is 1 em. Age is Pleistocene, 35 to 11.5 ka. 

Tom Mays Park Formation of the Thunderbird Group 

Precambrian 

Texas 

Orogrande basin 

Thomann, W.F., 1980, Ignimbrites, trachytes, and sedimentary rocks of the Precambrian 

Thunderbird Group, Franklin Mountains, El Paso, Texas: Geological Association of 

America Bulletin, v. 92, no. 2, pt. I, p. 94-100. 

Type section: Exposure 3,000 ft northeast of Smugglers Pass in 

Fusselman Canyon, Franklin Mountains, lat 31°53'06" N., long 

106°29'34" W., El Paso County, Tex. Named for Tom Mays Memorial 

Park. 
326 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

The Tom Mays Park Formation is here named the upper of three 

formations in the Thunderbird Group (new name) in the Franklin 

Mountains, Tex. Consists of rhyolitic ignimbrites. Individual flow units 

have not been recognized due to the uniform texture of the groundmass 

produced partly by devitrification of glass and partly by subsequent 

contact metamorphism caused by intrusion of the Red Bluff Granite. 

Intruded by widely scattered dikes of porphyritic rhyolite. Overlies the 

Smugglers Pass Formation (new name) of the Thunderbird; the top of 

the formation is an erosional surface. Maximum thickness is 550 ft. Age 

is late Precambrian. 

Tower Hill Quartzite of the Merrimack Group 

Silurian 

Massachusetts 

New England province 

Goldsmith, Richard, Grew, E.S., Hepburn, J.C., and Robinson, G.R., Jr., 1982, Formation names in the Worcester area, Massachusetts: U.S. Geological Survey Bulletin 

1529-H, p. H43-H56. 

Type locality: Tower Hill, Main Street, Boylston, Shrewsbury 7.5-

minute quadrangle, Worcester County, Mass. 

The informal Tower Hill quartzite member of the Boylston Formation of Grew (1970), also called unit B of Grew (1973), is here named the 

Tower Hill Quartzite of the Merrimack Group in the Worcester area, 

Massachusetts. Consists of orthoquartzite and interlayered pelite and 

may represent a proximal facies laterally equivalent to the distal facies 

of the Worcester Formation. Overlies the Boylston Schist; underlies the 

Oakdale Formation. Age is probably Silurian based on a tentative 

correlation with rocks in central Maine. 

Trap Member of the Bell Canyon Formation of the Delaware 

Mountain Group 

Late Permian (Guadalupian) 

Texas, New Mexico 

Permian basin 

Winner, Phil, 1985, Type section for the uppermost Bell Canyon Formation in the central 

Delaware basin of West Texas: West Texas Geological Society Bulletin, v. 24, no. 7, 

p. 7-10. 

Type section: Gulf J.R. Grandin Number 1 well, sonic-gamma ray log, 

SEl/4 sec. 33, Block 29 PSL Survey, Loving County, Tex. Derivation of 

name not stated. 

The Trap Member, here named, is in the upper Bell Canyon 

Formation of the Delaware Mountain Group in the central Delaware 

basin of Texas and New Mexico and was designated the informal Trap 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 327 

subdivision by Nottingham (1960) and the Trap member by Grauten 

(1965). This excellent and widespread regional nonproducing marker 

bed is restricted to a thin silt-sand marker below the base of the 

overlying Lamar Limestone Member of the Bell Canyon. Overlies the 

Ramsey Member (new name) of the Bell Canyon. [Age is Late Permian 

(Guadalupian).] 

Trapper Creek Formation 

Early Permian (Leonardian) 

Idaho 

Great Basin province 

Mytton, J.W., Morgan, W.A., and Wardlaw, B.R., 1983, Stratigraphic relations of 

Permian units, Cassia Mountains, Idaho, in Miller, D.M., and others, eds., Tectonic 

and stratigraphic studies in the eastern Great Basin: Geological Society of America 

Memoir 157, p. 281-303. 

Type section: Lower part: Exposures in Badger Gulch above the type 

section of the Badger Gulch Formation, sec. 20; upper part: Cliffs above 

Fall Creek, south of its confluence with Trapper Creek, center S1/2SE1/4 

sec. 9, T. 15 S., R. 20 S., Severe Spring 7.5-minute quadrangle, Cassia 

County, Idaho. 

Rocks mapped as the Park City Group by Morgan (1980) are here 

named the Trapper Creek Formation in the Cassia Mountains, southern 

Idaho. Consists of brownish-gray, very fine grained, medium- to thickbedded, fossiliferous limestone containing chert lenses alternating with 

buff, calcareous siltstone and very fine grained sandstone that resembles chert where it is silicified. Forms prominent ledges and cliffs. 

Deposits represent a fairly rapid shallowing of marine waters and a 

well-oxygenated, aerobic environment. Gradationally overlies the Badger Gulch Formation (new name); underlies the Grandeur Tongue of the 

Park City Formation. Thickness of composite section is 271 m. Age is 

Early Permian (early Leonardian) based on conodonts. 

Treadway Mountain Formation of the lake George Group 

Proterozoic 

New York 

Adirondack uplift 

Wiener, R.W., McLelland, J.M., Isachsen, Y.W., and Hall, L.M., 1984, Stratigraphy and 

structural geology of the Adirondack Mountains, New York: Review and synthesis: 

Geological Society of America Special Paper 194, p. 1-55. 

Type locality: None designated. Occurs in the eastern Adirondack 

Mountains, N.Y. Origin of name not stated. 

The name Treadway Mountain Formation, used by Walton and 

deWaard (1963), is here assigned to the Lake George Group (new name) 
328 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

in the eastern Adirondack Mountains, N.Y. Consists of migmatitic 

biotite-quartz-plagioclase gneiss, quartz-rich graphite-garnetsillimanite gneiss, quartzite, and garnet-biotite gneiss. Overlies the 

Paradox Lake Formation (new name) of the Lake George Group; 

underlies the Barton Mountain Formation. In the central Adirondacks, 

biotitic and garnetiferous rocks similar to the Treadway Mountain are 

present in the Lake Durant Formation, suggesting that the Treadway 

Mountain may be present, but thinner, in the central Adirondacks. 

Correlates with the Pleasant Lake Gneiss (new name) of the Oswegatchie Group in the northwestern Adirondacks. Age is Proterozoic. 

[Although this name has not been formally proposed, it is included here 

because of its continued usage.] 

Trego Hot Springs Bed of the Pyramid Lake Member of the 

Mount Mazama Formation 

Pleistocene 

Nevada, California 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Trego Hot Springs, south of the Western Pacific Railroad, 

200 m west of the intersection of Nevada Highway 49 and a dirt track on 

Black Rock Desert, 18 km east of Gerlach, sec. 3, T. 33 N., R. 25 E., 

Pershing County, Nev. 

The Trego Hot Springs Bed of the Pyramid Lake Member (new 

name) of the Mount Mazama Formation, here named, is in the Lake 

Lahontan area. Is present in the Pyramid Lake area, Nevada, northwest to Surprise Valley, Calif. Is the most potassium-rich bed of tephra 

in the Pyramid Lake. Is interbedded with the lower member of the 

Sehoo Formation. Age is Pleistocene, 35 to 11.5 ka. 

Trolinger Spring Formation 

Pleistocene (Sangamonian and Wisconsinan) 

Missouri 

Ozark uplift 

Haynes, C.V., Jr., 1985, Mastodon-bearing springs and late Quaternary geochronology of 

the lower Pomme de Terre valley, Missouri: Geological Society of America Special 

Paper 204, 35 p. 

Type locality: None designated. Named for Trolinger Spring, Breshears Valley, near Avery, sec. 9, T. 38 N., R. 22 W., Fristoe 15-minute 

quadrangle, Hickory County, Mo. 

Alluvial deposits of the T-2 terrace in the Breshears Valley, Hickory 

and Benton Counties, Mo., are here named the Trolinger Spring 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 329 

Formation. Brakenridge (1981) named this unit the informal Trolinger 

Formation. Consists of 1 to 2 m of chert gravel, having a dark-gray 

patina, overlain by 9 m of gray silty clay and clayey silt and lenses of 

clayey sand and gravel. Fossil bones from associated peat deposits 

include mastodon, mammoth, horse, and bison. Forms a well-developed 

dark-gray soil. Unconformably overlies the Breshears Valley Formation (new name); unconformably underlies the Boney Spring Formation 

(new name) from which it is separated by an erosional hiatus of 2,000 to 

3,000 years. Age is Pleistocene (Sangamonian and middle Wisconsinan) 

based on a uranium-series date of 160 ka on mastodon tooth enamel and 

radiocarbon dates of 32 ka on wood and plant fragments. 

Truthville Slate or Formation 

Cambrian(?) 

New York 

New England province 

Rowley, D.B., Kidd, W.S.F., and Delano, L.L., 1979, Detailed stratigraphic and 

structural features of the Giddings Brook slice of the Taconic allochthon in the 

Granville area, in Friedman, G.M., ed., Guidebook: New England Intercollegiate 

Geological Conference, 71st Annual Meeting, p. 186-242. 

Type locality: Exposures along the Mettawee River near Truthville, 

Washington County, N.Y. (Jacobi, 1977). 

The Truthville Slate or Formation, informally named by Jacobi 

(1977), is described in the Giddings Brook slice of the Taconic allochthon 

in the Granville area, New York. Consists of olive-gray-green, tanweathering, soft, well-cleaved, fissile, silty, micaceous slate. Gradationally overlies the Bomoseen Formation; sharply underlies the Browns 

Pond Formation (new name) at which the color changes from graygreen to black. Thickness is typically 45 m but ranges from 20 to 60 m. 

Age is Cambrian(?). [Although this name has not been formally proposed, it is included here because of its continued usage.] 

Tsoyawata Bed of the Mazama Member of the Mount 

Mazama Formation 

Holocene 

California, Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Stream cut on the south side of Long Valley Creek, 

southwest of U.S. Highway 395, 1.1 km west of the California-Nevada 

State line, center NEl/4NWl/4 sec. 19, T. 21 N., R. 18 E., Loyalton 
330 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

15-minute quadrangle, Sierra County, Calif. Tsoyawata is the Washo 

Indian word for Long Valley Creek. 

The Tsoyawata Bed of the Mazama Member (new name) of the 

Mount Mazama Formation, here named, is in the Lake Lahontan area of 

Nevada and California. Occurs at Virgin Creek, Lone Mountain, and 

Stillwater, Nev., and west of the crest of the Sierra Nevada and south 

to Lake Tahoe, Calif. Is the lower bed of the Mazama and consists of 5 

em of white tephra containing masses of small green hornblende laths. 

Overlies the Osgood Bed (new name) at Osgood Swamp, Calif. Age is 

Holocene, 7 ka. 

Tunnels Mill Member of the Yorktown Formation 

Pliocene 

Virginia, Maryland 

Atlantic Coast basin 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of uppermost Cenozoic 

deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological 

Survey Professional Paper 1067-G, 53 p. 

Type section: Borehole H-22, depth interval18 to 80ft, 6 to 68ft below 

sea level, at the junction of county roads 693 and 706, about 0.6 mi 

southwest of Tunnels Mill, Accomack County, Va. 

The Tunnels Mill Member, here named, is the middle member of the 

Yorktown Formation in a 10-mi-wide belt in the subsurface of Accomack 

County, Va., and Somerset and Worcester Counties, Md. Consists 

mainly of greenish- to brownish-gray, micaceous, clayey silt, silty clay, 

and fine quartz sand. Gradationally overlies the lower shelly sand 

member and gradationally underlies the upper shelly sand member of 

the Yorktown or unconformably underlies the Accomack Member (new 

name) of the Omar Formation. May be equivalent in part to the 

Morgarts Beach Member of the Yorktown west of the Chesapeake Bay. 

Thickness at the type section is 62ft. Age is middle Pliocene. 

Turner Mine Shale Member of the Carbondale Formation of 

the Kewaunee Group 

Middle Pennsylvanian (Desmoinesian) 

Illinois 

Illinois basin 

Nelson, W.J., 1983, The Turner Mine Shale Member: A newly named stratigraphic unit 

of the Carbondale Formation: Illinois State Geological Survey Circular 529, Geologic 

Notes, p. 11. 

Type section: Core B-41, depth interval 52.7-56.7 ft, at the Turner 

Number 1 mine, SWl/4NEl/4 sec. 27, T. 9 S., R. 4 E., Crab Orchard 

7.5-minute quadrangle, Williamson County, Ill. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 331 

The Turner Mine Shale Member of the Carbondale Formation of the 

Kewaunee Group, here named, is in the subsurface of the Illinois basin 

coal field. Consists of black, thinly laminated, hard, brittle, fissile shale 

containing pyrite, abundant organic matter, and high natural radioactivity. Spheroidal concretions of limestone occur near the base. 

Abruptly overlies the Springfield (Number 5) Coal Member or gradationally overlies the Dykersburg Shale Member and conformably underlies the St. David Limestone Member or the Canton Shale Member, all 

of the Carbondale Formation. Thickness at the type section is 5 ft and 

ranges from less than 1 in. to more than 8 ft. Age is Middle Pennsylvanian (Desmoinesian). 

Turupah Flat Bed of the Salt Wells Member of the Mono 

Basin Formation 

Holocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: On the edge of Turupah Flat, 0.2 km southeast of Salt 

Wells, NEl/4SWlf4NElf4 sec. 2, T. 17 N., R. 30 E., Churchill County, 

Nev. 

The Turupah Flat Bed of the Salt Wells Member (new name) of the 

Mono Basin Formation (new name), here named, is in the Lake 

Lahontan area, Nevada. Is widespread in the Fallon area and occurs at 

Weber Dam on the Walker River. Rhyolite tephra bed is 1 em thick and 

is poor in phenocrysts and lacks glass-encased biotite; may represent a 

crystal-poor fraction of the Walker Lake Bed (new name) of the Salt 

Wells. The Turupah Flat is the ash layer described by Morrison (1964) 

at the base of the Turupah Formation. Source is attributed to Mono 

Basin because of its southerly distribution and its similarity to rhyolitic 

tephra erupted in the Mono Basin. Age is Holocene, 1.5 to 0.6 ka. 

Tusas Mountain Granite 

Middle Proterozoic 

New Mexico 

San Juan basin 

Wobus, R.A., and Hedge, C. E., 1982, Redefinition of the Precambrian Tusas Mountain 

and Tres Piedras granites, north-central New Mexico: The Mountain Geologist, v. 19, 

no. 4, p. 105-114. 
332 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type locality: Shallow prospect pits about 100m west of the road, west 

side of Tusas Mountain, NEl/4 sec. 23, T. 28 N., R. 7 E., Rio Arriba 

County, N. Mex. 

A 5-km2 stock of massive granite porphyry at Tusas Mountain, 

previously described with granites exposed in Tusas Canyon and in the 

village ofTres Piedras as the Tusas Granite of Just (1937) and the Tusas 

Mountain pluton of the Tres Piedras Granite of Barker (1958), is here 

named the Tusas Mountain Granite. The term Tres Piedras Granite is 

applied only to the foliated granite of the older 1, 700-Ma intrusive 

episode. Consists of white to pink, fine-grained, massive to faintly 

foliated, porphyritic granite containing phenocrysts of microcline, 

quartz, and oligoclase and noteworthy amounts of purple fluorite. 

Underlies nearly all of Tusas Mountain; is in intrusive contact with the 

Moppin Formation on the west and south and with the Maquinita 

Granodiorite on the north. Age is Middle Proterozoic based on 

rubidium-strontium and uranium-lead ages of 1,500 and 1,430 Ma of the 

Tusas Mountain stock. 

Twelve Mile Member of the Lehigh Acres Formation of the 

Glades Group 

Early Cretaceous (Comanchean) 

Florida 

South Florida province 

Applegate, A.V., Winston, G.O., and Palacas, J.G., 1981, Subdivision and regional 

stratigraphy of the Pre-Punta Gorda rocks (Lowermost Cretaceous-Jurassic(?)) in 

south Florida: Gulf Coast Association of Geological Societies Transactions, v. 31 

(supplement), October, p. 447-453. 

Type section: Humble Number 1 Lehigh Acres well P-407, depth 

interval12,460-12,760 ft, sec. 14, T. 45 S., R. 27 E., Lee County, Fla. 

Named for the Twelve Mile Slough. 

The Twelve Mile Member is here named the middle member of the 

Lehigh Acres Formation (new name) of the Glades Group in the 

subsurface of the South Florida basin, where four regionally persistent 

anhydrite units are identified below the Punta Gorda Anhydrite of the 

Glades. Consists of cream to brown, micritic, or oolitic limestone beds 

overlain by a fine-grained, porous, brown dolomite about 75 ft thick, 

termed the brown dolomite zone, in the lower part, and gray argillaceous limestone in the upper part. Overlies the West Felda Shale 

Member (new name) and underlies the Able Member (new name) of the 

Lehigh Acres Formation. Thickness at the type well is 300ft. Age is 

Early Cretaceous (earliest Comanchean). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 333 

Tygarts Creek Member of the Slade Formation 

Late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R., 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Southeastern highwall of the Ken-Mor Stone Company's 

Olive Hill quarry, Grahn quadrangle, Carter County, Ky. Named for 

Tygarts Creek that flows adjacent to the quarry. 

The Tygarts Creek Member, here named, is in the Slade Formation 

(new name) and was formerly called the Reelsville-Beech Creek Limestone by McFarlan and Walker (1956), which is now restricted from the 

Cumberland Escarpment area of east-central and northeastern Kentucky. Occurs throughout the outcrop belt of the Slade and consists of 

light-gray calcarenite containing local stringers of dolomite. Disconformably overlies or intertongues with the Armstrong Hill, Holly Fork, 

or Rosslyn Me.mbers (all new names) of the Slade; conformably underlies the Ramey Creek Member (new name) of the Slade. Thickness 

ranges from 1 to 10 m. Age is Late Mississippian. 

Tygh Valley Formation of the Dalles Group 

Miocene and Pliocene 

Oregon 

Eastern Columbia basin 

Farooqui, S.M., Beaulieu, J.D., Bunker, R.C., Stensland, D.E., and Thoms, R.E., 1981, 

Dalles Group: Neogene formations overlying the Columbia River Basalt Group in 

north-central Oregon: Oregon Geology, v. 43, no. 10, p. 131-140. 

Reference section: North-facing roadcut along Tygh Valley-Wamic 

road, sec. 4, T. 4 S., R. 13 E., Wasco County, Oreg. Named for the town 

of Tygh Valley, sec. 3, T. 4 S., R. 13 E. 

Interbedded basaltic, andesitic, and pumiceous sandstone and conglomerate, tuffaceous sandstone and siltstone, tuff, breccia, and 

agglomerate in the Tygh basin are here named the Tygh Valley 

Formation of the Dalles Group. Disconformably overlies the Frenchman 

Springs Member of the Wanapum Basalt and the Grande Ronde Basalt; 

underlies Miocene and Pliocene andesite flows of the Cascade Range. 

Age is middle Miocene to Pliocene based on potassium-argon ages. 
334 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Ugnuravik Group 

Early Cretaceous (Valanginian to Albian) 

Alaska 

Arctic Coastal Plains province 

Carman, G.J., and Hardwick, Peter, 1983, Geology and regional setting of Kuparuk oil 

field, Alaska: American Association of Petroleum Geologists Bulletin, v. 67, no. 6, 

p. 1014-1031. 

Type section: U gnu State 1 well, depth interval 5,580-6,793 ft b.r. t., 

Kuparuk field, Colville-Prudhoe basin, T. 12 N., R. 9 E., Umiat Base 

Line, Alaska. Named for the Ugnuravik River, which flows through the 

field. 

Subunits: Miluveach Formation, Kuparuk Formation, Kalubik 

Formation. 

The U gnuravik Group, here named, is mappable over more than 600 

mi2 in the Colville-Prudhoe basin, Alaska. Is divided into four lithostratigraphic units, which are recognized in the type section and are 

correlated across the basin in ascending order: the Miluveach, Kuparuk, 

and Kalubik Formations (all new names) and the informal HRZ unit, a 

highly radioactive zone. Consists of mudstone, shale, sandstone, and 

siltstone. Unconformably overlies the Kingak Shale; unconformably 

underlies the Colville Group. Probably correlates with the Nanushuk 

Group and Kongakut-Okpikruak Formations. Thickness is more than 

1,500 ft. Age is Early Cretaceous (early Valanginian to Albian) based 

on dinoflagellates and other microfauna. 

Union City Complex 

Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Exposures around Shannon Shopping Mall at the intersection of Georgia Highway 138 and Interstate Highway 1-85, Union 

City, Fairburn 7.5-minute quadrangle, Fulton County, Ga. 

The Union City Complex, here named, is mapped in the NewnanTucker synform near Atlanta, Ga. Consists of a complex of porphyritic 

muscovite-biotite granites and granite gneisses, foliated and unfoliated, 

that intrudes the Atlanta Group (new name). Age is probably Paleozoic. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 335 

Union Wash Formation 

Early and Middle Triassic 

California 

Great Basin province 

Mount, J.D., 1971, Stratigraphy and paleontology of the marine Triassic lnyo Mountains, 

Inyo County, California: Southern California Paleontological Society Bulletin, v. 3, no. 

7, p. 1-4, 9. 

Type locality: Outcrops on the south side of Union Wash, Inyo 

Mountains, northeast part of Union Wash 7.5-minute quadrangle, Inyo 

County, Calif. 

The informal Ceratite limestone of Smith (1898) is here named the 

Union Wash Formation in the Inyo Mountains, Calif. Consists of gray to 

dark-brown, fissile and platy shale and calcareous shale, platy thinbedded limestone and argillaceous limestone, and occasional lenticular 

beds of massive, gray limestone. Disconformably overlies the Owens 

Valley Formation; conformably underlies unnamed volcanic breccia, 

conglomerate, and tuff. Thickness is about 2,500 ft. Age is Early to late 

Middle Triassic (Ladinian) based on cephalopods and conodonts. 

Unity Farm Shale Member of the lees Summit Formation of 

the Pleasanton Group 

Late Pennsylvanian (Missourian) 

Missouri 

Forest City basin 

Howe, W.B., 1982, Stratigraphy of the Pleasanton Group, Pennsylvanian System in 

Missouri: Missouri Department of Natural Resources, Open File Report Series 

OFR-82-10-GI, 99 p. 

Type section: Section in Acme Brick and Tile Company shale quarry at 

Vale, NE1/4NW1/4 sec. 27, T. 48 N., R. 32 W., Jackson County, Mo. 

Named for Unity Farm, sec. 25, T. 48 N., R. 32 W. 

The Unity Farm Shale Member of the Lees Summit Formation (new 

name) of the Pleasanton Group, here named, is in the Forest City basin 

in northwestern Missouri. Represents the last episode of marine 

sedimentation prior to withdrawal of the sea and the development of 

stream valleys and clastic sedimentation. Consists of gray, silty, 

micaceous, thinly laminated shale containing clay-ironstone concretions. 

Overlies the Exline Limestone Member of the Lees Summit, to which it 

is closely related; unconformably underlies the Weldon River Sandstone 

Member (new name) of the Shale Hill Formation (new name). Equivalent shales in Iowa, Illinois, and Kansas have the same lithology. 

Thickness at the type section is 65 ft but generally ranges from a few 

feet to 50 ft. Age is Late Pennsylvanian (early Missourian). 
336 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Univeter Formation of the New Georgia Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

McConnell, K.I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Type locality: Exposures at Univeter, Canton and South Canton 

7.5-minute quadrangles, Cherokee County, Ga. 

Subunits: Lost Mountain Amphibolite Member, Rose Creek Schist 

Member. 

The Univeter Formation of the New Georgia Group (new name), 

here named, occurs in the Greater Atlanta region of northwest Georgia. 

Includes the Lost Mountain Amphibolite Member (new name), which 

forms two limbs of a fold, and the intervening Rose Creek Schist 

Member (new name). Consists of amphibolite, hornblende gneiss, 

garnet-chlorite schist, and thin-banded iron formation associated with 

precious-metal deposits. On the southeast the Univeter is in fault 

contact with the Sandy Springs Group. Age is Late Proterozoic and (or) 

early Paleozoic. 

Upsal Hogback Bed of the Carson Desert Formation 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Measured section 6 of Morrison (1964), 2.4 km south of 

Upsal Hogback, Carson Desert, NWl/4 sec. 14, T. 20 N., R. 28 E., 

Churchill County, Nev. 

The U psal Hogback Bed of the Carson Desert Formation (new 

name), here named, is in the Carson Desert, Lake Lahontan area, 

Nevada. Consists of brown, potassium-poor, basaltic tephra containing 

blocky shards. Eruption may have continued over a considerable time 

and there may be several beds of similar composition. Some of the 

tephra included in the U psal Hogback may be from the younger Soda 

Lake Bed (new name) of the Carson Desert because the two vents may 

have shared the same magma source and therefore early Soda Lake 

tephra might resemble late U psal Hogback tephra. Overlies the lower 

member of the Sehoo Formation and the Wono and Leter Ranch Beds 

of the Pyramid Lake Member (all new names) of the Mount Mazama 

Formation. Age is Pleistocene, 35 to 11.5 ka. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 337 

Van Buren Till 

Pleistocene (Wisconsinan) 

Maine 

New England province 

Genes, A.N., Newman, W.A., and Brewer, T.B., 1981, Late Wisconsinan glaciation 

models of northern Maine and adjacent Canada: Quaternary Research, v. 16, no. 1, 

p. 48--65. 

Type locality: Van Buren, northern Aroostook County, Maine. 

The Van Buren Till, here named, is the surface unit throughout 

northern Aroostook County, Maine. Drift is present in Canada and 

extends southward to the moraines extending from Winterville to 

Caribou. Consists of clayey to silty, compact, buff to dark-brown till and 

stratified drift containing clasts of granite-gneiss. Was deposited by the 

Laurentide ice sheet and correlates with the Mars Hill Till (new name) 

of southern Aroostook County and the Lennoxville Till of southeastern 

Quebec. Unconformably overlies the St. Francis Till (new name) along 

the St. John River; underlies a 4-m-thick section of younger identical till 

at Golden Rapids, thought to represent an ablation facies or minor 

fluctuation during deposition of the Van Buren drift. Age is Pleistocene 

(late Wisconsinan). 

Vang Formation of the Coleharbor Group 

Pleistocene (Wisconsinan) 

North Dakota 

Williston basin 

Bluemle, J.P., 1984, Geology of Towner County, North Dakota: North Dakota Geological 

Survey Bulletin 79, pt. I, p. 1-44. 

Type locality: Outcrop near Vang, eastern Cavalier County, N. Dak. 

The Vang Formation of the Coleharbor Group, here named, was 

informally named by Howard Hobbs in an unpublished study of the 

glacial stratigraphy of northeastern North Dakota. Is the next to lowest 

of five glacial till formations representing separate advances of glacial 

ice in Towner County and occurs sporadically over northeastern North 

Dakota. Consists of sand, gravel, and buff and light-gray sandy till 

containing pebbles and cobbles of crystalline rocks. Unconformably 

overlies the Cretaceous Pierre Formation or the Pleistocene Cando 

(new name) or Tiber Formations of the Coleharbor. Does not directly 

underlie any other unit. Thickness ranges from 20 to 35 ft in Towner 

County to 150ft elsewhere. Age is Pleistocene (Wisconsinan). 
338 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Villa Rica Gneiss Member of the Mud Creek Formation of the 

New Georgia Group 

late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Abrams, C.E., and McConnell, K.I., 1981, Stratigraphy of the area around the AustellFrolona antiform; west-central Georgia, in Wigley, P.B., ed., Latest thinking on the 

stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 55-67. 

Type locality: Exposures around the town of Villa Rica, Villa Rica 

7.5-minute quadrangle, Carroll and Douglas Counties, Ga. 

The Villa Rica Gneiss Member of the Mud Creek Formation (new 

name) of the New Georgia Group (new name), here named, is in the 

Villa Rica antiform on the northwest flank of the Austell-Frolona 

antiform in west-central Georgia. Consists of biotite-quartz-plagioclase 

gneiss containing minor amounts of muscovite and epidote and is 

interpreted to be a felsic metavolcanic metadacite. Is interlayered with 

the Cedar Lake Quartzite Member (new name) of the Mud Creek. 

Grades into the stratigraphically overlying but structurally underlying 

Andy Mountain and Bill Arp Formations (both new names) of the 

informal Roosterville group. Age is Proterozoic(?). 

McConnell, K. I., and Abrams, C. E., 1984, Geology of the Greater Atlanta region: Georgia 

Geologic Survey Bulletin 96, 127 p. 

Age of the Villa Rica Gneiss Member is Late Proterozoic and (or) 

early Paleozoic. 

Viola Springs Formation of the Viola Group 

Middle and late Ordovician (Champlainian and Cincinnatian) 

Oklahoma 

South Oklahoma folded belt province 

Amsden, T.W., 1983, Welling-Fite-Corbin Ranch strata, in Amsden, T.W., and Sweet, 

W.C., Upper Bromide Formation and Viola Group (Middle and Upper Ordovician) in 

eastern Oklahoma: Oklahoma Geological Survey Bulletin 132, pt. I, p. 1-23. 

Type section: 1.5 mi southeast of Viola Springs, NWl/4NEV4 sec. 19, 

T. 2 S., R. 8 E., Connerville NE quadrangle, Johnston County, Okla. 

Over much of western Oklahoma, where the Viola Formation cannot 

be readily distinguished from the Welling Formation, the Viola is here 

raised to Group status, and encompasses all Ordovician strata between 

the Bromide Formation and the Sylvan Shale. Pre-Welling Viola strata, 

the Viola Limestone of Wengerd (1948) and stratigraphic units 1 and 2 

of Glaser (1965), are here named the Viola Springs Formation of the 

Viola Group. Consists of siliceous, laminated calcareous mudstones and 

bedded cherts containing sponge spicules, graptolites, and other fossils 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 339 

in the lower 137 ft and light-gray, nodular, bedded muddy limestone 

containing nodular chert in the upper 173 ft. Sharply overlies the 

Pooleville Member of the Bromide Formation; gradationally underlies 

the Welling Formation of the Viola Group. Maximum thickness is 800 ft 

in the southwestern Arbuckle Mountains. Wedges out to the east. Age 

is Middle and Late Ordovician (Champlainian and Cincinnatian). 

Virginville Formation 

Late Cambrian and Early Ordovician 

Pennsylvania 

Appalachian basin 

Lash, G.G., and Drake, A.A., Jr., 1984, The Richmond and Greenwich slices of the 

Hamburg klippe in eastern Pennsylvania-Stratigraphy, sedimentology, structure, 

and plate tectonic implications: U.S. Geological Survey Professional Paper 1312, 40 p. 

Type area: Outcrops in the southwest corner of the Kutztown and the 

southern part of the Hamburg 7.5-minute quadrangles, Berks County, 

Pa. Named for the town of Virginville. 

Subunits: Sacony Member, Onyx Cave Member, Moselem Member. 

The Virginville Formation, here named in the Richmond slice of the 

Hamburg klippe in Pennsylvania, was called Martinsburg Shale by 

Miller (1937). Includes the Sacony, Onyx Cave, and Moselem Members 

(all new names). Consists of quartzose rocks, micrite, calcarenite, 

peloidal limestone, carbonate-clast conglomerate, arid black shale and 

mudstone. Tectonically overlies the younger Windsor Township Formation (new name) in the Greenwich slice. Thickness is 565 m. Age is Late 

Cambrian to late Early Ordovician based on conodonts. 

Volcano Peak Group 

Late Triassic and Early Jurassic 

Nevada 

Great Basin province 

Taylor, D.G., Smith, P.L., Laws, R.A., and Guex, Jean, 1983, The stratigraphy and 

biofacies trends of the lower Mesozoic Gabbs and Sunrise formations, west-central 

Nevada: Canadian Journal of Earth Sciences, v. 20, no. 10, p. 1598-1608. 

Type locality: Volcano Peak, Gabbs Valley Range, Mineral County, 

Nev. 

Subunits: Gabbs Formation and its Nun Mine, Mount Hyatt, and Muller 

Canyon Members; Sunrise Formation and its Ferguson Hill, Five Card 

Draw, New York Canyon, Joker Peak, and Mina Peak Members. 

The Volcano Peak Group, here named in the Gabbs Valley Range, 

Nev., includes the revised Late Triassic Gabbs and Early Jurassic 

Sunrise Formations and their members, listed above (all new names). 

Conformably overlies the Luning Formation; gradationally underlies 
340 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

the Dunlap Formation. Provides a record of nearly continuous marine 

sedimentation across the Triassic-Jurassic boundary and probably 

yields the most complete ammonite-bearing sequence anywhere. The 

Muller Canyon-Ferguson Hill section at Ferguson Hill is proposed as 

the stratotype for the Triassic-Jurassic System boundary. 

Wachapreague Formation 

Pleistocene (Sangamonian and Wisconsinan) 

Virginia 

Atlantic Coast basin 

Mixon, R.B., 1985, Stratigraphic and geomorphic framework of uppermost Cenozoic 

deposits in the southern Delmarva Peninsula, Virginia and Maryland: U.S. Geological 

Survey Professional Paper 1067-G, 53 p. 

Type section: Borehole W-1, depth interval 0-37 ft, on the crest of relict 

Upshur Neck barrier ridge, 1 mi north-northeast of the center of the 

town of Wachapreague, Accomack County, Va. 

The Wachapreague Formation, here named, underlies the narrow 

coastal lowland of the Bell Neck sand-ridge complex, which extends 

from the southern tip of the Delmarva Peninsula northeastward to the 

vicinity of Metomkin Bay, Va. Contains distinctive floral and faunal 

assemblages that indicate deposition during cool climatic conditions. 

Consists of a lower lithic unit of fine-grained, gray sand and clay-silt, 20 

ft thick, and an upper lithic unit of medium- to coarse-grained gravelly, 

yellowish-gray sand containing pebbles of black chert and quartz, 17 ft 

thick. Unconformably overlies the Yorktown Formation or truncates 

and (or) overlaps the Omar Formation and Nassawadox Formation (new 

name). Thickness attains 40 ft. Age is Pleistocene (Sangamonian and 

early Wisconsinan) based on uranium-isotope and amino-acidracemization ages. 

Wadsworth Bed of the Eetza Formation 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Wadsworth Amphitheatre north of Wadsworth, Washoe 

County, Nev. 

The Wadsworth Bed, here named, is in the Eetza Formation in the 

area between Wadsworth and Nixon, Lake Lahontan area, Nevada. Is 

a 1-cm-thick layer of tephra of intermediate chemical composition. Age 

is Pleistocene, 75 to 35 ka. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 341 

Wahlstrom Hollow Formation 

Early Permian (Wolfcampian) 

Idaho 

Great Basin province 

Mytton, J.W., Morgan, W.A., and Wardlaw, B.R., 1983, Stratigraphic relations of 

Permian units, Cassia Mountains, Idaho, in Miller, D.M., and others, eds., Tectonic 

and stratigraphic studies in the eastern Great Basin: Geological Society of America 

Memoir 157, p. 281--303. 

Type section: Exposures south of the confluence of Third Fork and 

Fourth Fork of Rock Creek and south of Rock Creek Road and up the 

ridge toward Wahlstrom Hollow, from NElf4SWlf4NElf4 to 

SWlf4NElf4SWlf4 sec. 32, T. 13 S., R. 19 E., Grand View Peak, Rams 

Horn Ridge, Trapper Peak, and Pike Mountain 7.5-minute quadrangles, 

Cassia County, Idaho. 

The Wahlstrom Hollow sequence of Morgan (1980), here named the 

Wahlstrom Hollow Formation, is exposed in valleys and upthrown fault 

blocks in the central and northeastern Cassia Mountains, Idaho. Consists of gray, brown, or reddish, fine-grained, medium- to thick-bedded, 

fossiliferous silty limestone and calcareous siltstone containing spicules, 

pyrite, siliceous nodules and laminae, and zones of recumbently folded, 

laterally discontinuous beds; interpreted as subaqueous soft-sediment 

slumps. Laminations and scoured surfaces indicate deposition by turbidity currents. May be part of the depositional sequence of the 

northern Oquirrh basin. Lower contact is covered; gradationally underlies the Third Fork Formation (new name). Thickness at the type 

section is 500 m. Age is Early Permian (Wolfcampian, mostly late) 

based on conodonts and fusulinids. 

Wahoo Creek Formation of the Atlanta Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-40. 

Type locality: Exposures along Wahoo Creek, Newnan North quadrangle, Coweta County, Ga. 

The Wahoo Creek Formation of the Atlanta Group (new name), 

named in the Newnan-Tucker synform near Atlanta, Ga., consists of 

nearly white, fine- to medium-grained, slabby gneiss. Distinctive lithologies in the Wahoo Creek are purple-pink-weathering schist and 

amphibolite in the lower 15 to 30 m and very thinly layered slabby 
342 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

calc-silicate gneiss. Sharply and conformably overlies the Clairmont and 

Senoia Formations (both new names) of the Atlanta Group; sharply and 

conformably underlies the Stonewall and Clarkston Formations (both 

new names) of the Atlanta. Thickness is estimated at 300 to 800 m. Age 

is Late Proterozoic and (or) early Paleozoic. 

Walker lake Bed of the Salt Wells Member of the Mono 

Basin Formation 

Holocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Core E, from 180 to 182 em, at the south end of Walker 

Lake, Mineral County, Nev. 

The Walker Lake Bed of the Salt Wells Member (new name) of the 

Mono Basin Formation (new name), here named, is in the Lake 

Lahontan area, Nevada. Consists of a layer of rhyolitic tephra about 1 

em thick that contains glass-encased biotite phenocrysts and has a high 

silica, low magnesium content. May represent a dense, crystal-rich 

fraction of the Turupah Flat Bed (new name) of the Salt Wells. Source 

is believed to be Mono Basin because of its geographic distribution south 

of Carson Sink. Age is Holocene, about 1.2 ka. 

Walworth Formation 

Pleistocene (Wisconsinan) 

Wisconsin, Illinois 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Road cut and test hole along Highway 15 (BeloitMilwaukee Road), 3.2 km northeast of Clinton, NEl/4SWl/4 sec. 3, 

T. 1 N., R. 14 E., Clinton 7.5-minute quadrangle, Rock County, Wis. 

Named for Walworth County, Wis. 

Subunits: Foxhollow Member, Aliens Grove Member, Clinton Member. 

The Walworth Formation, here named in south-central Wisconsin 

and northern Illinois, consists of sandy, gray to brown till and associated 

sand and gravel deposits. Is subdivided into the lower, clayey Foxhollow Member (new name), the sandy Aliens Grove Member (new name), 

and the upper, sandier Clinton Member (new name). Unconformably 

overlies pre-Pleistocene rocks; sharply underlies the Capron Member of 

the Zenda Formation (new name) in eastern Walworth County and the 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 343 

Horicon Formation (new name) to the north, and is the surficial unit in 

western Walworth and eastern Rock Counties, Wis. Thickness ranges 

from a few meters to 80 m. Age is Pleistocene (early Wisconsinan or 

older). 

Wantagh Formation 

Pleistocene (Wisconsinan) 

New York 

Atlantic Coast basin 

Rampino, M.R., and Sanders, J.E., 1981, Upper Quaternary stratigraphy of southern 

Long Island, New York: Northeastern Geology, v. 3, no. 2, p. 116-128. 

Type section: Silty-clay facies: Borehole 200-C, Wantagh Pollution 

Control Plant, Wantagh. Sand facies: Borehole 238, Wantagh Pollution 

Control Plant outfall pipe, Jones Beach State Park, Nassau County, 

N.Y. 

Widespread nearshore marine deposits in the subsurface of southcentral Long Island and the inner continental shelf off southern Long 

Island, N.Y., previously called the Gardiners Clay and the twenty-foot 

clay, are here named the Wantagh Formation. Consists of an olive-gray, 

fine-grained, silty clay facies, which occurs as a blanket deposit, and a 

white to tan, dense, shelly sand facies, which forms a lens beneath the 

Jones Beach barrier island. Unconformably overlies the Merrick Formation (new name); unconformably underlies the Bellmore Formation 

(new name). Thickness of the silty clay facies is 14.5 ft; thickness of the 

sand facies is 50 ft. Age is late Pleistocene (middle Wisconsinan). 

Warix Run Member of the Slade Formation 

late Mississippian 

Kentucky 

Cincinnati arch 

Ettensohn, F.R., Rice, C.L., Dever, G.R., Jr., and Chesnut, D.R., 1984, Slade and 

Paragon Formations-New stratigraphic nomenclature for Mississippian rocks along 

the Cumberland Escarpment in Kentucky: U.S. Geological Survey Bulletin 1605-B, 

37 p. 

Type section: Roadcut along Kentucky Highway 801, north of the 

intersection of Kentucky Highways 801 and 1274, near the head of 

Warix Run, a tributary of Licking River (Cave Run Lake), Bangor 

quadrangle, Rowan County, Ky. 

The Warix Run Member of the Slade Formation (new name), used 

informally by Dever (1977) and here named, is in the Cumberland 

Escarpment area of east-central and northeastern Kentucky. Strata of 

the W arix Run were previously assigned to the Newman Limestone and 

other units, which are now restricted from the Cumberland Escarpment 
344 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

area. Consists of light-olive-gray quartzose calcarenite and lesser 

calcilutite. Disconformably overlies the Borden Formation or Renfro, 

St. Louis, or Ste. Genevieve Members of the Slade Formation; intertongues with or conformably underlies the Mill Knob Member (new 

name) of the Slade. Thickness ranges from 0 to 31 m. Age is Late 

Mississippian. 

Warner Formation 

Silurian 

New Hampshire 

New England province 

Nielson, D.L., 1981, The bedrock geology of the Hillsboro quadrangle, New Hampshire: 

New Hampshire Department of Resources and Economic Development, Bulletin 8, 

76 p. 

Type locality: Outcrops along Interstate Highway 1-89, south of the 

village of Warner, Mt. Kearsarge 7.5-minute quadrangle, Merrimack 

County, N.H. 

Metasedimentary rocks previously mapped as the Littleton Formation in the Hillsboro quadrangle, New Hampshire, are here named the 

Warner Formation. Consists of dark-gray to brown calc-silicate granofels and sillimanite-biotite schist containing calc-silicate boudins. Overlies the Francestown Formation; underlies the Littleton Formation. 

Thickness is 3,000 ft. Age is Silurian based on lithologic similarities to 

the Silurian Madrid Formation in the Merrimack Synclinorium in 

Maine. 

Warnick Member of the Chuckanut Formation 

Eocene 

Washington 

Bellingham basin 

Johnson, S.Y., 1984, Stratigraphy, age, and paleogeography of the Eocene Chuckanut 

Formation, northwest Washington: Canadian Journal of Earth Sciences, v. 21, no. 1, 

p. 92-106. 

Type section: Logging road SP-410 above Canyon Creek, SEl/4 sec. 24, 

T. 39 N., R. 6 E., Whatcom County, Wash. Named for the town of 

Warnick. 

The Warnick Member of the Chuckanut Formation, here named, is 

in the easternmost part of the largest outcrop belt of the Chuckanut, 

which extends from the San Juan Islands into the foothills of the North 

Cascades, Wash. Consists of intervals of conglomeratic coarse-grained 

sandstone alternating with fine-grained massive to laminated mudstone, interpreted as alluvial plain and fan deposits. Overlies the Slide 

Member (new name) of the Chuckanut; is bounded on the north by 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 345 

faults. Thickness is 1,000 mat the type section. Age is middle to late(?) 

Eocene based on stratigraphic correlation with the Maple Falls and 

Padden Members (both new names) of the Chuckanut. 

Waste Gate Formation of the Potomac Group 

Early Cretaceous (Neocomian) 

Maryland, Delaware, New jersey, Virginia 

Atlantic Coast basin 

Hansen, H.J., 1984, Hydrogeologic characteristics of the Waste Gate Formation, a new 

subsurface unit of the Potomac Group underlying the eastern Delmarva Peninsula: 

Maryland Geological Survey Information Circular 39, 21 p. 

Type section: Ohio Oil Company L.G. Hammond Number 1 (Wi-Cg 37*) 

well, depth interval 4, 745-5,360 ft, near the crossroads of Waste Gate, 

Wicomico County, Md. 

The Waste Gate Formation of the Potomac Group, here named, 

occurs at depths from 3,500 to 5,670 ft in the subsurface of the eastern 

Delmarva Peninsula of Somerset, Wicomico, and Worcester Counties, 

Md., Accomack County, Va., and probably Sussex County, Del., and 

Cape May Point, N.J. Previously included in the Potomac Group, 

undivided, or the lower Patuxent Formation. Consists of nonmarine 

alluvial, unconsolidated to moderately lithified, gray to white, arkosic to 

feldspathic sandstone interbedded with drab, silty shale or clay. Unconformably overlies Jurassic rocks; unconformably underlies the Patuxent 

and Arundel Formations, undivided, of the Potomac Group. Thickness 

at the type section is 615 ft. Age is Early Cretaceous (N eocomian). 

Watauga River Gneiss of the Forge Creek Suite 

Middle Proterozoic 

North Carolina, Tennessee 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Along Bethel Church Road, 0.5 mi north of where it 

crosses the Watauga River, lat 36°17' N., long 8P52' W., Sherwood 

quadrangle, Watauga County, N.C. 

The Watauga River Gneiss of the Forge Creek Suite (new name), 

here named, is in the Watauga massif in the Blue Ridge of North 

Carolina and Tennessee. Consists of a granitoid lacking abundant biotite 

and is gradational into the Comers Gneiss of the Forge Creek Suite. Age 

is Middle Proterozoic based on a rubidium-strontium age of 1,175 Ma. 
346 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Waubeek Member of the Scotch Grove Formation 

Early Silurian (Wenlockian) 

Iowa 

Iowa shelf 

Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River fault zone and 

the structural and stratigraphic framework of eastern Iowa: Iowa Geological Survey 

Technical Information Series 13, 126 p. 

Type locality: Exposures along the Wapsipinicon River 1 mi northeast 

ofWaubeek, SE1/4SW1/4NE1/4 sec. 17, T. 85 N., R. 5 W., Linn County, 

Iowa. Reference core section: Near Walford, SE1/4SW1/4SW1/4SW1/4 sec. 

5, T. 81 N., R. 8 W., Johnson County, Iowa. 

The informal Waubeek facies of Witzke (1981) is here named the 

Waubeek Member in the upper Scotch Grove Formation (new name) in 

eastern Iowa. Consists of dense to vuggy, chert-free, sparsely fossiliferous, finely crystalline to microcrystalline dolomite. Fossil molds are 

locally common in some beds. Overlies the Buck Creek Quarry Member 

(new name), reassigned from the revised Hopkinton Formation, or the 

Fawn Creek Member (new name), both of the Scotch Grove in the 

western portion of the study area; is replaced laterally by the Buck 

Creek Quarry, Fawn Creek, and Palisades-Kepler (new name) Members; sharply underlies the Anamosa Member of the Gower Formation. 

Thickness averages 40 ft but attains a maximum of 56 ft. Age is Early 

Silurian (early and middle Wenlockian). 

Wausau Member of the Marathon Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Gravel pit on west side of Ryan Street, 1.5 mi south of 

Highway 29, SW1/4SW1/4NE1/4 sec. 27, T. 28 N., R. 8 E., Wausau 

15-minute quadrangle, Marathon County, Wis. Named for Wausau, 

Marathon County. 

The lower member of the Marathon Formation (new name) in the 

Chippewa sublobe in Marathon and Wood Counties, Wis., is here named 

the Wausau Member, following the informal usage of LaBerge and 

Myers (1971). Consists of brown pebbly loam to clay loam till in which 

more than 30 percent of the clasts are rotted. Unconformably overlies 

Precambrian bedrock; is the surficial unit in much of the area or 

underlies the Edgar Member (new name) of the Marathon or the Merrill 

Member of the Lincoln Formation (both new names) to the north. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 347 

Thickness is less than 10m. Age is Pleistocene (early Wisconsinan or 

older) based on organic deposits on top of the overlying Merrill Member. 

Waweig Formation 

Early to late Silurian (llandoverian to Pridolian) 

New Brunswick, Maine 

New England p rovi nee 

MacKenzie, G.S., 1940, The St. Stephen map-area, Charlotte County, N.B.: New 

Brunswick Department of Lands and Mines, Mining Section, 46 p. 

Type locality: Outcrops on Waweig peninsula and the east shore of Oak 

Bay in the St. Croix River, extending for 3 mi south from the head of the 

bay, St. Stephen map-area, Charlotte County, N.B., Canada. 

The Waweig Formation, here named, crops out on the Waweig 

peninsula in Charlotte County, N. B., and includes sediments on the east 

and west shores of Oak Bay. Consists of gray, fine-grained, cherty 

quartzite and purplish graywacke, siltstone, and siliceous argillite. 

Faulting and lack of outcrop obscure the relationship to the underlying 

Dennis Formation; unconformably underlies the Oak Bay Formation. 

Grades laterally into the facies equivalent Digdeguash Formation (new 

name). Age is Late Silurian based on fossils. 

Ruitenberg, A.A., and Ludman, Allan, 1978, Stratigraphy and tectonic setting of early 

Paleozoic sedimentary rocks of the Wirral-Big Lake area, southwestern New Brunswick and southeastern Maine: Canadian Journal of Earth Science, v. 15, p. 22-32. 

The Waweig Formation is here traced from the Wirral to the Calais 

area, where it is truncated by Devonian plutons west of the St. Croix 

River in Maine. In this area, consists of dense, fine-grained sandstone 

and siltstone of graywacke composition and nongraphitic slate. Transitionally overlies the Oak Bay Formation or unconformably overlies the 

Cookson Formation (new name); interfingers with the partially equivalent Digdeguash Formation (new name); grades upward into the 

overlying Flume Ridge Formation (new name). Age is Early to Late 

Silurian (Llandoverian to Pridolian) based on brachiopods, cephalopods, 

corals, and other fossil fauna. 

Weisenberg Member of the Windsor Township Formation 

Middle Ordovician 

Pennsylvania 

Appalachian basin 

Lash, G.G., and Drake, A.A., Jr., 1984, The Richmond and Greenwich slices of the 

Hamburg klippe in eastern Pennsylvania-Stratigraphy, sedimentology, structure, 

and plate tectonic implications: U.S. Geological Survey Professional Paper 1312, 40 p. 
348 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type locality: Exposures 1 km south of Weisenberg Church, Slatedale 

7.5-minute quadrangle, Lehigh County, Pa. 

The Weisenberg Member, here named, is in the Windsor Township 

Formation (new name) in the Greenwich slice of the Hamburg klippe in 

Pennsylvania. Consists of poorly cleaved to fissile gray shale, mudstone, claystone, and siltstone and the informal Werleys conglomerate, 

lenticular channel fill deposits thought to be debris flows, best exposed 

near W erleys Corner in the Slatedale 7. 5-minute quadrangle. Deposits 

are interpreted as open-fan or levee mudstones and siltstones cut by 

channel and interchannel facies of the Dreibelbis and Switzer Creek 

Members (both new names) of the Windsor Township. Maximum 

thickness is 1, 740 m. Age is Middle Ordovician based on graptolites. 

Weiser Basalt of the Columbia River Basalt Group 

Miocene 

Idaho 

Snake River basin 

Fitzgerald, J.F., 1982, Geology and basalt stratigraphy of the Weiser embayment, 

west-central Idaho, in Bonnachsen, Bill, and Breckenridge, R.M., eds., Cenozoic 

geology of Idaho: Idaho Bureau of Mines and Geology Bulletin 26, p. 103-128. 

Type locality: Basalt flows in the Weiser embayment at the eastern 

edge of the Columbia Plateau, Washington and Payette Counties, 

Idaho. 

Post-Grande Ronde basalt flows in the Weiser embayment, here 

named the Weiser Basalt of the Columbia River Basalt Group, are 

characterized by pumice breccia, scoria, volcaniclastic debris, and ash. 

Four informal members are defined on the basis of combined outcrop 

characteristics and unconformable relations with the underlying Imnaha 

and Grande Ronde flows. From oldest to youngest these members are 

the basalts of Cambridge, Sugarloaf, Star Butte, and the geographically 

isolated basalt of Black Canyon. Age is middle and late Miocene. 

Weldon River Sandstone Member of the Shale Hill Formation 

of the Pleasanton Group 

late Pennsylvanian (Missourian) 

Missouri 

Forest City basin 

Howe, W.B., 1982, Stratigraphy of the Pleasanton Group, Pennsylvanian System in 

Missouri: Missouri Department of Natural Resources, Open File Report Series 

OFR-82-10-GI, 99 p. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 349 

Type area: Exposures along Weldon River, Mercer and Grundy 

Counties, Mo. 

The Weldon River Sandstone Member is here named the basal 

member of the Shale Hill Formation (new name) of the Pleasanton 

Group in the Forest City basin in northwestern Missouri. Consists of 

channel- and valley-fill deposits of conglomerate, sandstone, and shale. 

Unconformably overlies the Unity Farm Shale Member (new name) of 

the Lees Summit Formation (new name); underlies the Locust Creek 

coal in the Blue Mound Shale Member (new name) of the Shale Hill. Age 

is Late Pennsylvanian (early Missourian). 

Welton Member of the Scotch Grove Formation 

Early Silurian (llandoverian, Telychian) 

Iowa 

Iowa shelf 

Johnson, M.E., 1983, New member names for the Lower Silurian Hopkinton Dolomite of 

eastern Iowa: Iowa Academy of Science Proceedings, v. 90, no. 1, p. 13-18. 

Type section: Behr quarry, 5 km south of Welton, NWlf4SWlf4 sec. 2, 

T. 81 N., R. 3 E., Clinton County, Iowa. 

Previously divided on the basis of paleontologic units, the Hopkinton 

Dolomite is here divided into lithologic members to facilitate interregional correlations based on sea-level curves. Rocks formerly called 

the Cyrtia Beds of the Hopkinton are here named the Welton Member 

of the Hopkinton Dolomite in eastern Iowa. Consists of tan, poorly 

bedded, very finely crystalline dolomite having a diversity of brachiopods, crinoids, trilobites, and bryozoans. Overlies both the patch-reef 

and inter-reef facies of the Johns Creek Quarry Member (new name) of 

the Hopkinton; underlies the Buck Creek Quarry Member (new name) 

of the Hopkinton. Thickness is 12.5 m or more. Age is Early Silurian 

(Llandoverian, Telychian). 

Bunker, B.J., Ludvigson, G.A., and Witzke, B.J., 1985, The Plum River fault zone and 

the structural and stratigraphic framework of eastern Iowa: Iowa Geological Survey 

Technical Information Series 13, 126 p. 

The Johns Creek Quarry, Welton, and Buck Creek Quarry Members, all new names of Johnson (1983), are here reassigned from the 

upper part of the Hopkinton Dolomite to the lower part of the Scotch 

Grove Formation (new name), a unit defined between the Hopkinton 

and the Gower Formation, for the purpose of preserving the original 

definitions of these units. 
350 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Wenatchee Formation 

Oligocene 

Washington 

Northern Cascade Range-Okanogan province 

Gresens, R.L., Naeser, C.W., and Whetten, J.W., 1981, Stratigraphy and age of the 

Chumstick and Wenatchee Formations: Tertiary fluvial and lacustrine rocks, Chiwaukum graben, Washington: Geological Society of America Bulletin, v. 92, no. 5, pt. I, 

p. 233-236; pt. II, p. 841-876. 

Type section: Outcrop on the northwest flank of Squilchuck Canyon in 

the foothills southwest of Wenatchee, SE1/4 sec. 21, SW1/4 sec. 22, NW1/4 

sec. 27, and NE1/4 sec. 28, T. 22 N., R. 20 E., Chelan County, Wash. 

Four reference sections are designated. 

The Wenatchee Formation, here named following the informal usage 

of Buza (1976) and Gresens (1977), is in the Chiwaukum graben in the 

eastern foothills of the central Cascade Range in Washington. May be 

present below the Columbia Plateau basalt flows to the east; is absent 

to the west, due partly to erosion. Is divided into two members at the 

type section: a lower sandstone and shale member subdivided into lower 

shale-dominated fluvial beds, sandstone-dominated fluvial beds, and 

shale and sandstone beds of lacustrine origin; and an upper white 

conglomerate member. Unconformably overlies crystalline basement 

rocks of the Swakane Biotite Gneiss or the Chumstick Formation (new 

name); unconformably underlies post-Miocene diamictite derived from 

the Yakima Basalt. Thickness at the type section is about 155 m; the 

maximum observed thickness is 300 m. Age is early Oligocene based on 

an age of 34 Ma on zircon from tuff. 

Wernecke Supergroup 

Middle Proterozoic 

Canada, Alaska 

Yukon-Porcupine province 

Delaney, G.D., 1981, The mid-Proterozoic Wernecke Supergroup, Wernecke Mountains, 

Yukon Territory, in Campbell, F.H.A., ed., Proterozoic basins of Canada: Geological 

Survey of Canada Paper 81-10, p. 1-23. 

Type area: Wernecke Mountains, lat 64°30'-65° N., long 133°-135° W., 

Yukon Territory, Canada. 

Subunits: Fairchild Lake Group, Quartet Group, Gillespie Lake Group. 

Rocks previously referred to as the Wernecke type Proterozoics or 

the Wernecke Assemblage are here named the Wernecke Supergroup in 

the Wernecke Mountains, Yukon Territory. Is divided into the lower 

Fairchild Lake Group, Quartet Group (new name), and upper Gillespie 

Lake Group. The Quartet Group, a monotonous succession of darkgray-weathering siltstone, fine sandstone, mudstone, and claystone at 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 351 

least 5 km thick, extends into Alaska in the Keele Range of the 

Porcupine Plateau. Wernecke Supergroup is correlated with the lower 

three groups of the Belt-Purcell Supergroup of the southern Cordillera. 

Age is Middle Proterozoic, 1,700 to 1,200 Ma. 

West Felda Shale Member of the Lehigh Acres Formation of the 

Glades Group 

Early Cretaceous (Comanchean) 

Florida 

South Florida province 

Applegate, A.V., Winston, G.O., and Palacas, J.G., 1981, Subdivision and regional 

stratigraphy of the Pre-Punta Gorda rocks (Lowennost Cretaceous-Jurassic(?)) in 

south Florida: Gulf Coast Association of Geological Societies Transactions, October 

(supplement), v. 31, p. 447-453. 

Type section: Humble Number 1 Lehigh Acres well P-407, depth 

interval12,760-12,800 ft, sec. 14, T. 45 S., R. 27 E., Lee County, Fla. 

Named for the West Felda oil field. 

The West Felda Shale Member is here named the lower member of 

the Lehigh Acres Formation (new name) of the Glades Group in the 

subsurface of the South Florida basin, where four regionally persistent 

anhydrite units are identified below the Punta Gorda Anhydrite of the 

Glades. Consists of dark-gray, micaceous, calcareous shale and shaly 

limestone. Overlies the Pumpkin Bay Formation (new name); underlies 

the Twelve Mile Member (new name) of the Lehigh Acres. Thickness at 

the type well is 40ft. Age is Early Cretaceous (earliest Comanchean). 

West Sak Sands 

Late Cretaceous 

Alaska 

Arctic Coastal Plains province 

Jamison, H.C., Brockett, L.D., and Mcintosh, R.A., 1980, Prudhoe Bay-A 10-year 

perspective, in Halbouty, M.T., ed., Giant oil and gas fields of the decade 1968-1978: 

American Association of Petroleum Geologists Memoir 30, p. 289-314. 

Type section: ARCO West Sak River State 1 well, depth interval 

3,742-3,842 ft, Prudhoe Bay field, T. 11 N., R. 10 E., Umiat Base Line, 

Alaska. 

The West Sak Sands, here named, is in the Prudhoe Bay field and 

consists of two sand units, each about 40 ft thick, separated by a 

25-ft-thick mudstone unit. Consists of fine-grained, friable, quartzose, 

argillaceous, and glauconitic, oil-bearing sands that are transitional 

from the underlying Upper Cretaceous Seabee Formation to the 

overlying Upper Cretaceous Prince Creek Formation. Age is Late 

Cretaceous. 
352 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Whaley Gneiss of the Cranberry Suite 

Middle Proterozoic 

North Carolina 

Piedmont-Blue Ridge province 

Bartholomew, M.J., and Lewis, S.E., 1984, Evolution of Grenville massifs in the Blue 

Ridge geologic province, southern and central Appalachians: Geological Society of 

America Special Paper 194, p. 229-254. 

Type locality: Along North Carolina State Road 1316 for about 0.5 mi 

north of Cannon Gap, which is 1 mi south of the community of Whaley, 

lat 36°13'30" N., long 82°56' W., Elk Park quadrangle, Avery County, 

N.C. 

The Whaley Gneiss, here named, is in the Cranberry Suite, the 

revised Cranberry Granite of Keith (1903), which is now restricted to 

the plutonic rocks of the Elk River massif in the Blue Ridge in North 

Carolina. Color is red or pink due to abundant pink feldspar. Forms 

numerous small igneous bodies within the Elk River massif. Age is 

Middle Proterozoic. 

Wheeler Coal Member of the Swede Hollow Formation of 

the Cherokee Group of the Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Outcrop at the former Wheeler Bridge spanning the 

Swede Hollow tributary to Whitebreast Creek, NWlf4NEl/4 sec. 33, 

T. 73 N., R. 22 W., Lucas County, Iowa. 

The Wheeler Coal Member, here named, is in the Swede Hollow 

Formation (new name) of the Cherokee Group in southeastern and 

south-central Iowa. Is closely related to the overlying Bevier Coal 

Member of the Swede Hollow; the interval between them is generally 

less than 20 ft, and they appear to coalesce in some areas. Together they 

may be considered as the biostratigraphic equivalent of the Lowell Coal 

[Member of the Carbondale Formation] of Illinois. Thickness rarely 

exceeds 2ft. Age is Middle Pennsylvanian (Desmoinesian). 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 353 

Whirlwind Creek Formation 

late Silurian to late Devonian (ludlovian to Frasnian) 

Alaska 

Holitna basin 

Dutro, J.T., Jr., and Patton, W.W., Jr., 1982, New Paleozoic formations in the northern 

Kuskokwim Mountains, west-central Alaska: U.S. Geological Survey Bulletin 1529-H, 

p. H13-H22. 

Type section: Exposures on the ridge between Whirlwind and Soda 

Creeks, sec. 23, T. 24 S., R. 23 E.; supplemental section: sees. 29 and 

30, T. 23 S., R. 25 E., Medfra (B-3) quadrangle, Alaska. 

The Whirlwind Creek Formation, here named, is in the Nixon Fork 

terrane of the Kuskokwim Mountains, Alaska, where it was deposited in 

a shallow-water carbonate environment. Consists of 300- to 400-m-thick 

cycles of algal dolomite and pelletoidal, silty, and reefy limestone. 

Overlies the Paradise Fork Formation (new name) north of Stone 

Mountain and disconformably overlies the Telsitna Formation (new 

name) through most of the region; unconformably underlies Permian 

through Lower Cretaceous strata west of White Mountain Creek. Is in 

fault contact with the East Fork Hills Formation (new name) of the East 

Fork terrane. Thickness ranges from 1,000 to 1,500 m. Age is Late 

Silurian to Late Devonian (Ludlovian to Frasnian) based on ostracodes, 

brachiopods, and corals. 

Whitebreast Coal Member of the Swede Hollow Formation of 

the Cherokee Group of the Des Moines Supergroup 

Middle Pennsylvanian (Desmoinesian) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Swede Hollow type section, exposures along a tributary 

to Whitebreast Creek in Swede Hollow, sees. 33 and 34, T. 73 N., 

R. 22 W., and sec. 3, T. 72 N., R. 22 W., Lucas County, Iowa. 

The White breast Coal Member, here named, is at the base of the 

Swede Hollow Formation (new name) of the Cherokee Group in 

southeastern and south-central Iowa. Is laterally persistent over a 

14-county area and has a uniform thickness of about 1ft. Is equivalent 

to the Colchester (Number 2) Coal in Illinois and the Croweburg Coal in 

Kansas and Missouri. Age is Middle Pennsylvanian (Desmoinesian). 
354 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Whitney Granodiorite 

late Cretaceous 

California 

San Joaquin basin 

Moore, J.G., 1981, Geologic map of the Mount Whitney quadrangle, Inyo and Tulare 

Counties, California: U.S. Geological Survey Geologic Quadrangle Map GQ-1545, scale 

1:62,500. 

Type locality: Exposures 200m north of the summit of Mount Whitney, 

Mount Whitney 15-minute quadrangle, Tulare County, Calif. 

The Paradise-Whitney nested sequence extends 83 km southeastward from the central part of the Marion Peak quadrangle on the 

northwest, through the Mount Whitney quadrangle, to the southeastern part of the Olancha quadrangle on the southeast in Inyo, Tulare, and 

Fresno Counties, Calif. Includes the Whitney pluton, here named the 

Whitney Granodiorite, which intrudes the center of the nested 

sequence, and the Paradise pluton, named the Paradise Granodiorite 

(new name). Consists of porphyritic granodiorite and granite having 

large phenocrysts of potassium feldspar. Is domical in profile, and the 

present level of exposure is apparently near its top. The ParadiseWhitney sequence was emplaced as a single intrusion about 85 Ma, but 

before complete solidification occurred, the partly molten and more 

differentiated siliceous Whitney Granodiorite core burst through the 

solidified wall of the Paradise Granodiorite on the southeast side. 

Western and eastern contacts of the Whitney dip under the Paradise, 

and its axis plunges north beneath the Paradise. Granite porphyry dikes 

and sills, probably originating from the deeper, still molten parts of the 

pluton, intrude the Whitney. Age is Late Cretaceous based on a 

potassium-argon biotite age of 83 Ma. 

Wildcat Basin Rhyolite Member of the Strawberry Volcanics 

Miocene 

Oregon 

Snake River basin 

Thayer, T.P., Case, J.E., and Stotelmeyer, R.B., 1981, Mineral resources of the 

Strawberry Mountain wilderness and adjoining areas, Grant County, Oregon: U.S. 

Geological Survey Bulletin 1498, 67 p. 

Type locality: Exposures extending southwest from a vent complex in 

the head of Indian Creek, just north of and into Wildcat Basin, 

Strawberry Range, Grant County, Oreg. 

The Wildcat Basin Rhyolite Member of the Strawberry Volcanics, 

here named, is in the Strawberry Mountain block in Grant County, 

Oreg. Consists of white or pale-gray to pinkish rhyolitic tuffs and flows 

that extend southwestward from a vent complex in the head of Indian 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 355 

Creek and includes two or more platy rhyolites having spherulitic 

glassy tops that appear to be about 300 m thick and obsidian breccia 

flows. Overlies beds of the Strawberry Volcanics; interfingers with and 

underlies andesite flows from the main Strawberry vent. The Wildcat 

Basin eruptive center appears to have been located at the intersection 

of two faults, now buried under younger flows and tuffs. Age is late 

Miocene (12 Ma). 

Wildcat Den Coal Member of the Caseyville Formation of the 

Morrow Supergroup 

Middle Pennsylvanian (Morrowan) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Exposures at Wildcat Den State Park, SWl/4 sec. 17 and 

SEl/4 sec. 18, T. 77 N., R. 1 E., Muscatine County, Iowa. 

The Wildcat Den Coal Member, here named, is the lowermost and 

most widely traceable of the coals in the Caseyville Formation in 

southeastern and south-central Iowa. Consists of shaly, pyritic coal1.5 

ft thick at the type section. Age is Middle Pennsylvanian (Morrowan). 

Wildcat Mountain Rhyolite of the St. Francois Mountains 

Volcanic Supergroup 

Middle Proterozoic 

Missouri 

Ozark uplift 

Berry, A.W., Jr., 1976, Proposed stratigraphic column for Precambrian volcanic rocks, 

western St. Francois Mountains, Missouri, in Kisvarsanyi, E.B., ed., Studies in 

Precambrian geology of Missouri with a guidebook to parts of the St. Francois 

Mountains: Missouri Geological Survey Report of Investigations 61, Contribution to 

Precambrian Geology 6, p. 81-90. 

Type section: Exposures along the north slope of Wildcat Mountain, 

Sl/zNE1/4 sec. 6, T. 33 N., R. 3 E., Johnson Shut-ins quadrangle, 

Reynolds County, Mo. 

Rocks exposed on Lee, Bell, North Bell, Wildcat, Taum Sauk, 

Russell, and Crane Mountains and on College Hill in the western St. 

Francois Mountains, southeast Missouri, are here named the Wildcat 

Mountain Rhyolite. Includes rocks previously called the Shut-ins fragmental ash flow of Anderson (1962) and all but the upper part of Unit D 

of the tuff of Stouts Creek of Anderson (1970). Consists of deep-maroon 

ash-flow tuff containing quartz and feldspar phenocrysts and white 
356 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

stringers of microcrystalline quartz and feldspar. Overlies the Russell 

Mountain Rhyolite (new name); underlies the Bell Mountain Rhyolite 

(new name). Thickness is 90 m. Age is Middle Proterozoic. 

Kisvarsanyi, E.B., 1976, Missouri Precambrian revisited: Progress in studies of Precambrian geology, 1961-1976, in Kisvarsanyi, E. B., ed., Studies in Precambrian geology of 

Missouri with a guidebook to parts of the St. Francois Mountains: Missouri Geological 

Survey Report of Investigations 61, Contribution to Precambrian Geology 6, p. 66-80. 

The formal name St. Francois Mountains Volcanic Supergroup, here 

adopted for all the Precambrian volcanic rocks of southeast Missouri, 

includes the Wildcat Mountain Rhyolite. 

Wildhorse Meadows Quartzite of the Big Bear Group 

Precambrian 

California 

Mohave basin 

Cameron, C.S., 1982, Stratigraphy and significance of the upper Precambrian Big Bear 

Group, in Cooper, J.D., Geology of selected areas in the San Bernardino Mountains, 

western Mohave desert, and southern Great Basin, California: Geological Society of 

America, Cordilleran Section, 78th Annual Meeting, guidebook, field trip 9, p. 5-20. 

Type section: Northwest ofWildhorse Meadows, SWl/4 sec. 4, T. 1 N., 

R. 2 E., Moonridge 7.5-minute quadrangle, San Bernardino County, 

Calif. 

The lowermost unit of the Big Bear Group (new name), widely 

exposed near Sugarloaf Mountain in the Big Bear area of the San 

Bernardino Mountains, Calif., and informally named the Wildhorse 

Quartzite by Cameron (1981), is here named the Wildhorse Meadows 

Quartzite. Includes two informal members. Basal conglomerate of the 

lower member, W1, overlies Precambrian basement gneisses with 

spectacular angular unconformity and grades rapidly upward into 

clast-free quartzite. The upper member, W2, consists of cliff-forming, 

light-gray or white, fine- to medium-grained orthoquartzite, and an 

uppermost conglomerate that directly underlies the Lightning Gulch 

Formation (new name) of the Big Bear Group. At the type section 

member W1 is 244 m thick and member W2 is 151 m thick. Age is late 

Precambrian. 

Wilson Grove Formation 

Miocene and Pliocene 

California 

Northern Coast Range province 

Fox, K.F., Jr., 1983, Tectonic setting oflate Miocene, Pliocene, and Pleistocene rocks in 

part of the Coast Ranges north of San Francisco, California: U.S. Geological Survey 

Professional Paper 1239, 33 p. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 357 

Type locality: Area between Wilson Grove and Mark West Creek, 2.5 

km due south, 11 km north of Sebastopol, T. 8 N., R. 9 W., Sonoma 

County, Calif. 

Rocks previously assigned to the Merced(?) Formation in the 

Sebastopol block in Sonoma County, Calif., are here named the Wilson 

Grove Formation. Consists of unconsolidated, fine-grained, massive 

sand and minor amounts of gravel and tuff deposited under beach and 

shallow-marine conditions. A conspicuous but discontinuous interbed of 

pumice lapilli tuff 15 to 75 m above the base of the Wilson Grove was 

erupted from the Sonoma Volcanics and probably correlates with a tuff 

in the Petaluma Formation. Local deposits of sand and gravel of alluvial 

origin overlying the marine beds and previously included with them in 

the Merced(?) Formation are here treated as a separate unit, the 

informal sand and gravel of Cotati. Overlies a surface of low to moderate 

relief beveled across Franciscan and Great Valley basement rocks; 

contact with the Petaluma Formation to the east is concealed by 

younger alluvial deposits. Correlates with the lower Merced of Glen 

(1959) at the Merced Formation type section. Thickness attains 150 m. 

Age is late Miocene and Pliocene and spans the revised boundary 

between the Miocene and Pliocene, based on potassium-argon ages of 

6.1 and 5. 7 Ma on tuff in the Wilson Grove and Pliocene molluskan 

faunas. 

Winchester Creek Member of the Tiger Formation 

Eocene, Oligocene, and Miocene 

Washington 

Northern Cascade Range-Okanogan province 

Gager, B.R., 1983, Stratigraphy of the Tiger Formation, northeastern Washington: 

Northwest Geology, v. 12, p. 25-41. 

Type section: Outcrop in roadcut on west side of Winchester Creek, 

southeast corner NE1/4 sec. 5, T. 32 N., R. 42 E., Pend Oreille County, 

Wash. 

The Winchester Creek Member, here named, is in the revised Tiger 

Formation in the Cusick region of northeastern Washington. Consists of 

fine-grained sandstone, siltstone, and shale in 1- to 5-mm-thick finingupward sequences, and subordinate medium- to coarse-grained sandstone. Base is not exposed but probably unconformably overlies the 

Sanpoil Volcanics east of the Pend Oreille River and older strata west of 

the river; is a facies equivalent of, intertongues with, and is separated 

by a vertical arbitrary boundary from the Gibraltar Rock Member (new 

name) of the Tiger; conformably and unconformably underlies the 

Calispell Lake Member (new name) of the Tiger. Thickness is 40 mat 

the type section; inferred total thickness is 900 m. Age ranges from 

early middle Eocene, based on inclusions of late early to early middle 
358 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Eocene volcanic rock clasts, through middle Miocene, based on middle 

Miocene regional faults that bound the Tiger Formation, although the 

age determination of middle Miocene is less definite. 

Windsor Township Formation 

Early and Middle Ordovician 

Pennsylvania 

Appalachian basin 

Lash, G.G., and Drake, A.A., Jr., 1984, The Richmond and Greenwich slices of the 

Hamburg klippe in eastern Pennsylvania-Stratigraphy, sedimentology, structure, 

and plate tectonic implications: U.S. Geological Survey Professional Paper 1312, 40 p. 

Type locality: Exposures along the east and west banks of Maiden 

Creek, between the towns of Dreibelbis and Kempton, Windsor Township, Kutztown and Hamburg 7.5-minute quadrangles, Berks County, 

Pa. 

Subunits: Weisenberg Member, Switzer Creek Member, Dreibelbis 

Member. 

The Windsor Township Formation, here named, was mapped as 

Lithotectonic Unit A by Alterman (1972). Is an allochthonous unit in the 

Greenwich slice of the Hamburg klippe, Berks County, Pa., deposited in 

the middle fan area of a large submarine fan. Includes the Weisenberg 

Member (new name), a shale, siltstone, and mudstone unit, and the 

Switzer Creek and Dreibelbis Members (both new names), graywacke 

and gray-green shale units. Locally contains older units of boulder 

conglomerate and limestone, chert, and variegated shale and mudstone 

that are not restricted to any particular member but are found throughout the formation. Underlies the Virginville Formation (new name) in 

the tectonically overlying, but older, Richmond slice of the Hamburg 

klippe. Minimum thickness is 6,215 m. Age of the graywacke and shale 

members is Middle Ordovician based on graptolites. Age of the limestone, chert, and variegated shale units may be Early and Middle 

Ordovician based on graptolites and conodonts; if the age determination 

is correct, these units may be allochthonous with respect to the 

graywacke and shale. 

Windy Hill Quartz Dioritic Orthogneiss 

late Triassic or Early jurassic 

Washington 

Northern Cascade Range-Okanogan province 

Menzer, F.J., Jr., 1983, Metamorphism and plutonism in the central part of the Okanogan 

Range, Washington: Geological Association of America Bulletin, v. 94, no. 4, 

p. 471-498. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 359 

Type locality: Outcrops on the slopes of Windy Hill east of Buzzard 

Lake, T. 34 N., R. 25 E., Okanogan County, Wash. 

The Windy Hill Quartz Dioritic Orthogneiss, a late synmetamorphic 

plutonic unit, here named, is in the Okanogan Range, Wash. Intrudes 

the Salmon Creek schists and gneisses; is intruded by the Late 

Cretaceous Conconully Granodiorite (new name). Is of the same general 

age as the Leader Mountain Granodioritic Gneiss and the Reed Creek 

Quartz Dioritic Gneiss and is similar to them in mineralogy, texture, and 

structure. Age is Late Triassic or Early Jurassic. 

Winn Formation of the Saginaw Group 

Early and Middle Pennsylvanian (Morrowan to Desmoinesian) 

Michigan 

Michigan basin 

Vugrinovich, Ray, 1984, Lithostratigraphy and depositional environments of the Pennsylvanian rocks and the Bayport Formation of the Michigan basin: Michigan Geological 

Survey Division, Report of Investigation 27, 33 p. 

Type section: McClure Oil Company Number 1-20 Paul and Karen 

Bigelow well, depth interval 573-706 ft, SElf4SEl/4NWl/4 sec. 30, 

T. 13 N., R. 4 W., Lincoln Township, Isabella County, Mich. Derivation 

of name not stated. 

Subunit: Verne Member. 

The Winn Formation of the Saginaw Group, here named, occurs in 

the subsurface of the Michigan basin. Includes the Verne Member, 

reassigned from the Saginaw Formation. Consists of gray, soft, clayey 

shale, siltstone, and sandstone and, in the upper part, the Verne 

Member, a persistent thin bed of calcareous black shale or argillaceous 

limestone containing brachiopods and molluscs. Gradationally overlies 

the Lake George Formation (new name) of the Saginaw Group; unconformably underlies unnamed Jurassic red beds or unconsolidated postJurassic deposits. The lower part of the Winn represents channel 

deposits of fluvial origin, and the Verne Member represents a return to 

marine conditions. Thickness is 133 ft at the type well. Age is Early and 

Middle Pennsylvanian (late Morrowan to late Desmoinesian). 

Winterhaven Formation 

Jurassic(?) 

Arizona, California 

Salton basin, Basin and Range province 

Haxel, G.B., Tosdal, R.M., and Dillon, J.T., 1985, Tectonic setting and lithology of the 

Winterhaven Formation: A new Mesozoic stratigraphic unit in southeasternmost 

California and southwestern Arizona: U.S. Geological Survey Bulletin 1599, 19 p. 
360 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Exposures on the northern limb of an anticline just west 

of Little Picacho Wash, lat 33° N., long 114°37'30" W., southeast corner 

of the Picacho SW 7.5-minute quadrangle, Imperial County, Calif. 

Derivation of name not stated. 

The Winterhaven Formation, named informally by Haxel (1977) and 

here named, is in the Picacho-Peter Kane Mountain area, Imperial 

County, Calif., and Yuma County, Ariz. Consists of a basal dacite 

member, 80 m thick; a medial quartz arenite member, 60 m thick; and an 

upper argillitic siltstone member, 300 m thick. Was originally part of the 

upper plate of the Chocolate Mountains thrust and was subsequently 

placed directly over the late Mesozoic Orocopia Schist. Depositionally 

overlies and interfingers with Jurassic(?) rhyodacitic metavolcanic rocks 

along the Mesozoic Chocolate Mountains thrust fault; unconformably 

underlies Oligocene to Holocene volcanic and sedimentary rocks. Thickness at the type section is more than 440 m. Age is Jurassic(?) based on 

field relations and lithologic correlation with the lower part of the 

Jurassic and (or) Cretaceous McCoy Mountains Formation. 

Wolf Canyon Quartz Diorite 

Cretaceous 

Washington 

Northern Cascade Range-Okanogan province 

Menzer, F.J., Jr., 1983, Metamorphism and plutonism in the central part of the Okanogan 

Range, Washington: Geological Association of America Bulletin, v. 94, no. 4, 

p. 471-498. 

Type locality: Exposures south ofWolfCanyon, east side of the Methow 

Valley, T. 34-35 N., R. 22-23 E., Okanogan County, Wash. 

The Wolf Canyon Quartz Diorite, a postmetamorphic plutonic unit, 

here named, is in the Okanogan Range, Wash. Consists of massive, 

magmatic diorite and quartz diorite. Plagioclase is andesine; green 

hornblende is the principal mafic mineral. Contact with the Red Shirt 

Gabbro (new name) may be intrusive or gradational; intrudes the Lower 

Cretaceous Newby Formation. Age is Cretaceous. 

Wolf Creek Formation of the Atlanta Group 

Late Proterozoic and (or) Paleozoic 

Georgia 

Piedmont-Blue Ridge province 

Higgins, M.W., and Atkins, R.L., 1981, The stratigraphy of the Piedmont southeast of 

the Brevard Zone in the Atlanta, Georgia, area, in Wigley, P.B., ed., Latest thinking 

on the stratigraphy of selected areas in Georgia: Georgia Geologic Survey Information 

Circular 54-A, p. 3-4 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 361 

Type section: Exposures along and near Wolf Creek, Luxomni quadrangle, Gwinnett County, Ga. 

The Wolf Creek Formation of the Atlanta Group (new name), here 

named, is in the Newnan-Tucker synform near Atlanta, Ga., and 

consists of interlayered laminated amphibolite and biotite-muscovite 

button schists. Grades into button schists of the Brevard Zone to the 

northwest, and into the Promised Land Formation (new name) of the 

Atlanta Group to the southeast. Is in sharp contact with the Clairmont 

Formation and Norcross Gneiss (both new names) of the Atlanta to the 

southwest. Thickness is 1,200 m. Age is Late Proterozoic and (or) early 

Paleozoic. 

Wono Bed of the Pyramid Lake Member of the Mount 

Mazama Formation 

Pleistocene 

Nevada 

Great Basin province 

Davis, J.O., 1978, Quaternary tephrochronology of the Lake Lahontan area, Nevada and 

California: Nevada Archeological Survey Research Paper 7, 137 p. 

Type section: Agency Bridge on the east side of the Truckee River, 

NWl/4NWl/4NEl/4 sec. 1, T. 22 N., R. 23 E., Nixon 15-minute quadrangle, Washoe County, Nev. Named for the Paiute Indian word for 

Pyramid Island. 

The Wono Bed of the Pyramid Lake Member (new name) of the 

Mount Mazama Formation, here named, is in the Lake Lahontan area 

where it occurs in many localities from Pyramid Lake to the Carson 

Desert. Consists of three or more graded beds of white tephra, at least 

10 em thick, and represents several airfall events. Characteristic of the 

W ono is the presence of long thin pipes among the glass shards. Is 

interbedded with the lower member of the Sehoo Formation. Overlies 

the Timber Lake Bed (new name) and underlies the Leter Ranch Bed 

(new name), both of the Pyramid Lake. Age is Pleistocene, 35 to 11.5 

ka. 

Wood River Formation 

late Jurassic(?) 

Florida 

South Florida province 

Applegate, A.V., Winston, G.O., and Palacas, J.G., 1981, Subdivision and regional 

stratigraphy of the Pre-Punta Gorda rocks (Lowermost Cretaceous-Jurassic(?)) in 

south Florida: Gulf Coast Association of Geological Societies, Transactions, October 

(supplement), v. 31, p. 447-453. 
362 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

Type section: Bass Collier Company 12-2 well P-778, depth interval 

16,510-18,610 ft, sec. 12, T. 52 S., R. 27 E., Collier County, Fla. Named 

for Wood River, a creek 4 mi southeast of the type well. 

The Wood River Formation, here named, is in the subsurface of the 

South Florida basin, where it is the lowermost of four regionally 

persistent anhydrite units below the Punta Gorda Anhydrite of the 

Glades. Consists of basal coarse clastic rocks overlain by anhydrite and 

microcrystalline brown dolomite and minor amounts of micritic limestone. Overlies Jurassic (189 Ma) rhyolite porphyry; underlies the Bone 

Island Formation (new name). Thickness at the type well is 2,100 ft. 

Age is Late Jurassic(?) based on the estimated time interval between 

rhyolite emplacement and deposition of the basal clastic rocks. 

Wyoming Hill Coal Member of the Caseyville Formation of 

the Morrow Supergroup 

Middle Pennsylvanian (Morrowan) 

Iowa 

Iowa shelf 

Ravn, R.L., Swade, J.W., Howes, M.R., Gregory, J.L., Anderson, R.R., and Van Dorpe, 

P.E., 1984, Stratigraphy of the Cherokee Group and revision of Pennsylvanian 

stratigraphic nomenclature in Iowa: Iowa Geological Survey Technical Information 

Series 12, 76 p. 

Type section: Escarpment along Iowa Highway 22, NE1/4 sec. 34, 

T. 77 N., R. 1 W., Muscatine County, Iowa. Named for Wyoming Hill. 

The Wyoming Hill Coal Bed, here named, occurs near the top of the 

Caseyville Formation in southeastern and south-central Iowa. Consists 

of two coal beds separated by a narrow detrital clastic split. Lies only a 

few feet below the "Spoon" Formation sandstones. Thickness is 1.5 ft. 

Age is Middle Pennsylvanian (Morrowan). 

Yahoo Clay of the Snake River Group 

Pleistocene 

Idaho 

Snake River basin 

Malde, H. E., 1982, The Yahoo Clay, a lacustrine unit impounded by the McKinney Basalt 

in the Snake River canyon near Bliss, Idaho, in Bonnichsen, Bill, and Breckenridge, 

R.M., ed., Cenozoic geology of Idaho: Idaho Bureau of Mines and Geology Bulletin 26, 

p. 617-628. 

Type locality: Exposures near the mouth of Yahoo Creek, which joins 

the Snake River 4 mi south-southwest of Hagerman, sees. 3, 4, 5, 8, 9, 

and 10, T. 8 S., R. 13 E., Yahoo Creek quadrangle, Twin Falls County, 

Idaho. Eleven reference localities listed. 
LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 363 

Clay previously correlated with and mapped as the Bruneau Formation by Malde and Powers (1972) is here named the Yahoo Clay of the 

Snake River Group. The Yahoo accumulated in McKinney Lake behind 

a lava dam formed by the McKinney Basalt and occupies a much 

younger canyon than that occupied by the Bruneau. Consists of pinkishwhite to light-yellowish-brown compact, laminated clay. Overlies the 

McKinney Basalt; underlies surficial sand and silt deposits related to the 

Crowsnest Gravel of the Snake River Group. Thickness attains 280 ft. 

Age is Pleistocene. 

York Slate 

late Proterozoic 

Alaska 

Yukon-Koyokuck province 

Sainsbury, C.L., 1974, Geologic map of the Bendeleben quadrangle, Seward Peninsula, 

Alaska: U.S. Bureau of Mines, U.S. Geological Survey, and The Mapmakers, 31 p., 

scale 1:150,000. 

Type locality: None designated. Crops out widely over the Bendeleben 

quadrangle, York region of the Seward Peninsula, Alaska. 

Rocks of the Seward Peninsula previously called the Slate of the 

York region, Hurrah Slate, Puckmummie Slate, and Kuzitrin Series are 

here named the York Slate. Is metamorphosed in varying degrees and 

consists of weakly lineated, calcareous quartz siltite, graywacke, and 

limestone; graphitic slate; metamorphosed quartz gneiss; black phyllite 

with quartz veins; and quartz-biotite-graphite schist. Placer gold deposits are associated with the York Slate. Conformably underlies the 

Kanauguk Formation (new name) with a transitional boundary several 

hundred feet thick. Age is Late Proterozoic based on a rubidiumstrontium minimum age of 750 Ma for gneiss derived from the York. 

Yorkshire Formation 

late Proterozoic and (or) Early Cambrian 

Virginia 

Piedmont-Blue Ridge province 

Drake, A.A., Jr., and Morgan, B.A., 1981, The Piney Branch Complex-A metamorphosed fragment of the Central Appalachian ophiolite in northern Virginia: American 

Journal of Science, v. 281, no. 4, p. 484-508. 

Type locality: Exposure on the east bank of Bull Run, directly opposite 

the village of Yorkshire, Manassas 7.5-minute quadrangle, Prince 

William County, Va. 

The Yorkshire Formation, here named, is a thin discontinuous 

precursory ophiolitic melange underlying the Piney Branch Complex-

(new name) in Fairfax County, Va. Consists of quartz-plagioclasechlorite granofels that has a pronounced scaly foliation, and contains 
364 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

fragments of quartz, serpentinite, metagabbro, plagiogranite, and mafic 

volcanic rock. The Yorkshire is thought to record the first movement of 

the allochthonous Piney Branch slab. The Yorkshire and Piney Branch 

allochthon was thrust upon the Peters Creek Schist, and, together, they 

form a composite allochthon that was emplaced on the Sykesville 

Formation, perhaps by gravity sliding. The discontinuous nature of the 

Yorkshire is attributed to partial shearing-out during transport. Age is 

Late Proterozoic and (or) Early Cambrian, as movement of the allochthon began in Late Proterozoic and ended during the Taconic orogeny. 

Zenda Formation 

Pleistocene (Wisconsinan) 

Wisconsin 

Wisconsin arch 

Mickelson, D.M., Clayton, Lee, Baker, R.W., and others, 1984, Pleistocene stratigraphic 

units of Wisconsin: Wisconsin Geologic and Natural History Survey, University of 

Wisconsin Extension, Miscellaneous Paper 84-1, p. 1-15. 

Type section: Road cut on south side of Highway B, east of its 

intersection with Hillside Road, 1.8 km northeast of the locality of 

Zenda, NWlf4NWl/4SWlf4 sec. 26, T. 1 N., R. 17 E., Lake Geneva 

7.5-minute quadrangle, Walworth County, Wis. 

Subunits: Capron Member, Tiskilwa Member. 

The Zenda Formation, here named, is in the Lake Michigan Lobe in 

Walworth County, southeastern Wisconsin. Is divided into the Capron 

and Tiskilwa Members, both named in Illinois by Wilman and Frye 

(1970). Both members consist mainly of pink, calcareous, mediumgrained till. Sharply overlies the Clinton Member (new name) of the 

Walworth Formation (new name); sharply to gradationally underlies the 

New Berlin Formation (new name) or is the surficial unit in Walworth 

County. Age is Pleistocene (Wisconsinan). 

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LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 365 

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366 LEXICON OF GEOLOGIC NAMES OF THE UNITED STATES 

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