U.S.GEOLOGICAL SURVEY CIRCULAR 1028 

Appalachian Basin SymposiumProgram and Extended Abstracts 
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Appalachian Basin SymposiumProgram and Extended Abstracts 

Arthur P. Schultz, editor and basin coordinator 

U.S. Geological Survey Circular 1028 

Twenty extended abstracts describing Appalachian 

thermal history, structure, and stratigraphy in studies 

that are part of ongoing research funded by the 

U.S. Geological Survey Evolution of Sedimentary 

Basins Program 
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 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1989 

Free on application to the Books and Open-File Reports Section, 

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

library of Congress Cataloging in Publication Data 

Appalachian Basin Symposium (1988 : Reston, Va.) 

Appalachian Basin Symposium program and extended abstracts edited by 

Arthur P. Schultz. 

p. em. - (U.S. Geological Survey circular ; 1028) 

Bibliography: p. 

Supt. of Docs. no.: I 19.4/2:1028 

1. Geology-Appalachian Basin-Congresses. 2. Appalachian BasinCongresses. I. Schultz, Arthur P. II. Title. Ill. Series. 

QE78.3.A67 1989 557.5-dc19 89-600079 
FOREWORD 

The abstracts in this circular were presented during a daylong symposium on the 

geology of the central part of the Appalachian basin held on November 9,1988, in 

Reston, Va. Participants of the symposium included U.S. Geological Survey geologists 

from the Office of Energy and Marine Geology and the Office of Regional Geology as 

well as scientists from local State surveys and universities. The symposium was held 

during the final stages of a 5-year multidiscipline basin analysis effort and is part of 

the USGS Evolution of Sedimentary Basins Program. This program focuses the 

research of a wide variety of disciplines into a combined stratigraphic, structural, and 

basin evolution synthesis. USGS Bulletin 1839 is a multichaptered series containing 

the full descriptions of the research presented at the symposium. The first four chapters of this bulletin have been published, and the remaining are in review or final preparation. 

Approximately 60 geologists attended the symposium. Stratigraphic syntheses 

included description of rocks ranging from lowermost Cambrian through the Pennsylvanian. Three talks presented differing interpretations of Carboniferous rocks from the 

same area. Other stratigraphic studies included work on Silurian stratigraphy and the 

Taconic unconformity, descriptions and interpretations of the syn-orogenic Ordovician 

Fincastle Conglomerate, and changes in Silurian facies in the Appalachian Valley and 

Ridge province. Fluid migration and basin thermal history were addressed in two presentations. The importance of considering fluid migration in thermal modeling was 

stressed. Basin tectonics and structure were the topics of several talks and posters. 

Included were discussions on the genesis of the Pennsylvanian salient, lateral ramps in 

the central and southern Appalachians, dome and basin features associated with thrusting in the southern Appalachians, and gravity slides in the Valley and Ridge province. 

Completing the program were a presentation of research on Eocene igneous rocks in 

the central Appalachian Valley and Ridge province and a review of the economic geology of the Big Chimney quadrangle, Kanawha County, West Virginia. 

Foreword Ill 

9:00AM 

9:10AM 

9:30AM 

9:50AM 

10:10 AM 

10:30 AM 

11:00 AM 

11:20 AM 

11:40 AM 

12:00 M 

1:30PM 

1:50PM 

2:10PM 

PROGRAM 

Wednesday, November 9, 1988 

Introductory remarks-Arthur P. Schultz, Appalachian 

Basin Coordinator 

Tectonically induced fluid migration in sedimentary basins: 

A new factor to be considered in the assessment of 

thermal history-by Paul P. Hearn, Jr., Harvey E. Belkin, and John F. Sutter 

Reevaluation of conodont color alteration patterns in Ordovician rocks, east-central Valley and Ridge and western 

Blue Ridge provinces, Tennessee-by Randall C. Orndorff, Anita G. Harris, and Arthur P. Schultz 

Stratigraphic framework of Cambrian and Ordovician rocks 

in the central Appalachian basin-by Robert T. Ryder 

The depositional environment of the Middle Ordovician 

Fincastle conglomerate-by Chrysa M. Cullather 

COFFEE BREAK 

Regional stratigraphy of Silurian rocks and an enigmatic 

Ordovician diamictite, southeastern New York-by Jack 

B. Epstein 

The origin of the Pennsylvania salient and CDP seismic 

imaging of the Cornwall-Kelvin displacement along the 

U.S. Atlantic conti~ental margin-by Robert C. Milici 

and Kenneth C. Bayer 

Lateral ramps and the structure of the central and southern 

Appalachians, with implication for thrust belts worldwide-by Howard A. Pohn 

LUNCH BREAK 

Carboniferous petrographic trends in the central Appalachian 

basin: An orogenic interpretation-by Joseph T. 

O'Connor 

Interpretations of sedimentary patterns in the Pennsylvanian 

of the central Appalachian basin-by Charles L. Rice 

Depositional trends in late Paleozoic coal-bearing strata of 

2:30PM 

4:00PM 

the central Appalachian basin-by Kenneth J. Englund 

and Roger E. Thomas 

POSTER SESSION: Art Exhibits Hallway 

Eocene igneous intrusive rocks of the central Appalachian 

Valley and Ridge province-by C. Scott Southworth and 

Karen J. Gray 

The geologic framework of the continental shelf and slope of 

Virginia, with emphasis on petroleum geology- by Kenneth C. Bayer and Robert C. Milici 

Petrographic characteristics of the New River Formation of 

the central Appalachian basin-by Joseph T. O'Connor 

and Nelson L. Hickling 

Economic geology of the Big Chimney quadrangle, 

Kanawha County, West Virginia-by John F. Windolph, 

Jr. 

Stratigraphy, sedimentology, and economic potential of the 

Chilhowee Group in the central and southern Appalachians-by K.Y. Lee 

Provenance and depositional history of the Fincastle Conglomerate of southwestern Virginia-by Nelson L. Hickling and Harvey E. Belkin 

Anticlines of the Copper Creek-Narrows thrust block, southwestern Virginia-by Robert C. McDowell 

Silurian stratigraphic changes and their effect on the distribution of large bedrock landslides, Appalachian Valley 

and Ridge province-by Calvin R. Wiggs and Arthur P. 

Schultz 

Central Appalachian Transect: Geology of the Radford, 

Virginia, 1° quadrangle-by Mervin J. Bartholomew, 

Arthur P. Schultz, and Robert C. McDowell 

Cenozoic epidermal gravity tectonics of the Colorado Front 

Range and Appalachian Valley and Ridge province-by 

Arthur P. Schultz 

SYMPOSIUM ENDS 

Program V 

Appalachian Basin Symposium-Program and 

Extended Abstracts 

Arthur P. Schultz, editor and basin coordinator 

Tectonically Induced Fluid Migration in 

Sedimentary Basins: A New Factor To Be 

Considered in the Assessment of Thermal 

History 

Paul P. Hearn, Jr., Harvey E. Belkin, and John F. Sutter 

A growing body of evidence now suggests that large 

volumes of fluids were expelled from deeply buried foreland basin sediments during plate collisions along the 

margins of the North American craton. Hot (100 to 200 °C) 

saline (10 to 20 weight percent NaCl equiv.) fluids apparently were driven out of peripheral basins and migrated 

considerable distances onto the craton during geologically 

brief periods of time. Temporally asynchronous but analogous fluid-migration events are believed to have occurred 

along the entire extent of the Marathon, Ouachita, Appalachian, and Caledonide orogenic belts. Similar events are 

believed to have occurred in the Alberta basin and in 

tectonically active basins of the continental interior. These 

conclusions are supported by a large body of data including 

K A d 40Ar/ 39 . ' - r an Ar analyses of secondary mmerals, paleomagnetic data, computer simulations of basin paleohydrology, fluid-inclusion analyses, and petrographic observations. The large-scale transfer of heat associated with the 

upward migration of hot basinal fluids is capable of producing abnormally high thermal gradients. While these 

anomalous gradients are geologically short lived, they 

persist long enough to be reflected in fluid-inclusion, 

conodont-alteration, fission-tract, and vitrinite-reflectance 

data. Also, potassium metasomatism, commonly associated 

with brine migration, may produce increased ordering in 

illite-smectite assemblages. As a consequence, some depthof-burial estimates based on these thermal indicators may be 

erroneously high. In numerous instances, the lack of agreement between stratigraphic estimates of burial depth and 

estimates based on thermal-maturity indicators has been 

cited as evidence that stratigraphic estimates are erroneously low. Clearly, the assumption that burial-induced 

Manuscript approved for publication February 10, 1989. 

heating is the sole influence on the thermal history of 

sediments is often not valid, and models that ignore thermal 

overprints from fluid migration events may lead to significant errors. 

Reevaluation of Conodont Color Alteration 

Patterns in Ordovician Rocks, East-Central Valley 

and Ridge and Western Blue Ridge Provinces, 

Tennessee 

Randall C. Orndorff, Anita G. Harris, and Arthur P. 

Schultz 

An anomalously low, unexplained, conodont color 

alteration index (CAl) was reported for Ordovician rocks in 

the Tuckaleechee Cove window of the Blue Ridge province 

in previous investigations. These data encouraged hydrocarbon explorationists to consider the eastward extension of 

Valley and Ridge rocks beneath the metamorphosed thrust 

sheets of the Blue Ridge as a potential hydrocarbon province. Reevaluation of old and new CAl data in the easternmost thrust belt of the Valley and Ridge province and in 

windows through the Blue Ridge in central eastern Tennessee show that ( 1) although the CAl anomaly in the Tuckaleechee Cove window is of less magnitude than first 

reported, the CAl values for rocks in this window are still 

lower than CAl values in correlative rocks northward and 

northeastward at the eastern limit of the Valley and Ridge 

province; (2) CAl patterns in central eastern Tennessee are 

more complex than those shown by earlier investigations 

based on considerably fewer localities; these more complex 

patterns appear to be related to primary depositional trends 

in Middle and Upper Ordovician chiefly clastic rocks; (3) 

CAl values in Ordovician rocks of the Tuckaleechee Cove 

window are slightly lower than those in correlative rocks in 

nearby windows; this pattern persists in the Dumplin Valley 

thrust belt opposite the windows and appears to mimic 

thickness patterns of Middle and Upper Ordovician rocks; 

and ( 4) the area of hydrocarbon potential for Valley and 

Ridge rocks beneath the crystalline rocks of the Blue Ridge 

is somewhat less than previous estimates; these rocks, 

however, still have thermal potential for natural gas but are 

probably beyond the thermal limit for liquid hydrocarbons. 

Program and Extended Abstracts 
Stratigraphic Framework of Cambrian and 

Ordovician Rocks in the Central Appalachian 

Basin 

Robert T. Ryder 

Twelve restored stratigraphic cross sections through 

the subsurface of parts of Ohio, Pennsylvania, Kentucky, 

West Virginia, Virginia, and Tennessee provide new details 

of Cambrian and Ordovician stratigraphy, sedimentation, 

and tectonics in a broad segment of the Appalachian basin. 

Drilled thickness of the Cambrian and Ordovician sequence 

ranges from a maximum of about 14,500 ft (4.5 km) along 

the axis of the rift-controlled Rome trough in West Virginia 

to a minimum of about 2,900 ft (0.9 km) on the relatively 

stable shelf in Ohio. The partly drilled Cambrian and 

Ordovician sequence in the Rome trough of southwestern 

Pennsylvania is estimated to be as thick as 17,000 ft (5.2 

km). Sparse subsurface data combined with outcrop data 

suggest that the Cambrian and Ordovician sequence thins 

across the eastern margin of the Rome trough, but to a much 

lesser degree than on the western margin, before it thickens 

to at least 20,000 ft (6.1 km) in the thrust-faulted eastern 

segment of the Appalachian basin. 

Rift deposits, consisting primarily of the Rome Formation and the Conasauga Group, occupy as much as 

one-half of the Cambrian and Ordovician sequence. Near 

the central and eastern parts of the Rome trough, the 

sandstone- and multicolored-shale-dominated Rome Formation with several persistent carbonate units underlies the 

carbonate- and gray-shale-dominated Conasauga Group. 

However, along the western margin of the Rome trough, 

where a major east-dipping normal fault is present, the 

Rome Formation commonly climbs upsection at the 

expense of the Conasauga Group, and where more than one 

border fault is involved, the Rome Formation steps westward across progressively higher fault blocks. Generally, 

the Rome Formation terminates against the westernmost 

fault system of the Rome trough, and the name St. Simon 

Sandstone is applied to the basal sandstone on the adjoining 

hanging-wall block. 

In the thrust-faulted eastern margin of the basin, the 

Rome Formation thickens abruptly across one or more 

east-dipping normal faults and is as much as 5,000 ft (1.5 

km) thicker than in the Rome trough. In this part of the 

basin, the Rome Formation overlies the Shady Dolomite of 

Early and Middle Cambrian age, which in tum overlies the 

Chilhowee Group of earliest Cambrian age. Although the 

Rome Formation in the thrust-faulted eastern margin of the 

basin is older than in the Rome trough, its lithology remains 

dominated by sandstone, multicolored shale, and several 

persistent carbonate units. Judging from these data, the 

Rome Formation is a time-transgressive unit whose age, 

distribution, and thickness are controlled by basementinvolved extensional faults that, in general, are progres2 Appalachian Basin Symposium 

sively younger toward the west. Consequently, the age of 

the Rome Formation varies from Early Cambrian along the 

eastern margin of the basin, to latest Early and Middle 

Cambrian in the Rome trough, to earliest Late Cambrian on 

the faulted western margin of the Rome trough. 

Previously named limestone and shale units in the 

Middle and lower Upper Cambrian Conasauga Group from 

outcrops in the thrust belt of eastern Tennessee are recognized and correlated in the Rome trough. In central West 

Virginia, the Maryville Limestone, the middle limestone 

unit in the Conasauga, thickens at the expense of the 

overlying Nolichucky Shale, the upper shale of the Conasauga. The upper part of the Maryville Limestone in central 

West Virginia consists of dolomite that extends northwestward across the western margin of the Rome trough and into 

Ohio as a sandy dolomite unit that has been identified 

erroneously as the Rome Formation. 

The Upper Cambrian and Lower Ordovician Knox 

Group, Lower and lowermost Middle Ordovician Beekmantown Group, and the Upper Cambrian Gatesburg Formation 

thicken markedly eastward across the western margin of 

the Rome trough. The thickness of this predominantly 

dolomitic sequence is controlled by postrift subsidence that 

was greatest under the Rome trough and the rifted Appalachian continental margin farther east. The combined thickness of the Beekmantown Group and Gatesburg Formation 

in southwestern Pennsylvania and adjacent West Virginia is 

as much as 6,000 ft (1.8 km). The upper 1,000 ft (0.3 km) 

of the Beekmantown Group here consists of anhydritic 

dolomite and limestone of earliest Middle Ordovician age. 

The upper and lower sandy members of the Gates burg 

Formation in Pennsylvania and West Virginia correlate, 

respectively, with the Lower Ordovician Rose Run Sandstone in eastern Ohio and northeastern Kentucky and the 

Upper Cambrian Kerbel Formation in eastern and northern 

Ohio. The upper sandy member of the Gatesburg Formation 

includes the Olin Sandstone, which has been identified in 

Pennsylvania as a separate unit in the lowermost Gatesburg. 

The Rose Run Sandstone has a thickness of about 100 ft (30 

m) throughout eastern Ohio and northeastern Kentucky but 

thickens to as much as 300 ft (91 m) in ( 1) the Rome trough 

of southwestern Pennsylvania and adjacent West Virginia 

and (2) near its source area in northwestern Pennsylvania. 

Thin quartzose sandstone units near the top of the Upper 

Cambrian Copper Ridge Dolomite of the Knox Group in 

southwestern Virginia and near the base of the Lower 

Ordovician Chepultepec Dolomite of the Knox Group in 

eastern Tennessee correlated with the Rose Run Sandstone. 

The conflict created by an Upper Cambrian age for the 

upper sandy member of the Gatesburg Formation and by a 

Lower Ordovician age for the Rose Run Sandstone and the 

Chepultepec Dolomite has yet to be resolved. 

The well-documented Knox unconformity at the top 

of the Knox Group can be traced across the Rome trough in 

Kentucky and can be extended along the western part of the 
Rome trough in Pennsylvania and West Virginia on the 

basis of a thin sandstone unit in the overlying Middle 

Ordovician rocks. In the Rome trough of Pennsylvania and 

West Virginia, the Knox unconformity is located within the 

Beekmantown Group rather than at its more common 

position at the top of the Knox Group. 

The remaining part of the Ordovician sequence above 

the Beekmantown Group is composed of a Middle Ordovician limestone sequence, the Black River and Trenton 

Limestones, and an Upper Ordovician shale and sandstone 

sequence derived from the rising Taconic orogen to the east, 

the Antes Shale, Reedsville Shale, Bald Eagle Sandstone, 

and Juniata Formation. The combined thickness of these 

Middle and Upper Ordovician sequences is as much as 

5,500 ft (1.7 km) in Pennsylvania and West Virginia. These 

Middle and Upper Ordovician sequences maintain their 

lithologic character into central Ohio, but their combined 

thickness decreases to about 2,000 ft (0.6 km) there. The 

Middle Ordovician Black River and Trenton Limestones of 

Ohio, Pennsylvania, and West Virginia correlate with the 

High Bridge Group and Lexington Limestone, respectively, 

in eastern Kentucky and with the Stones River and Nashville Groups, respectively, in east-central Tennessee. The 

3,000- to 4,000-ft- (0.9- to 1.2-km-) thick Upper Ordovician shale and sandstone sequence in Pennsylvania and 

West Virginia thins to 1,000 ft (0.3 km) or less in eastern 

Kentucky and east-central Tennessee, where much of the 

sequence consists of argillaceous limestone. Thickness and 

facies variations in the Middle and Upper Ordovician 

sequence largely reflect the rapidly subsiding foreland basin 

west of the Taconic orogen rather than waning postrift 

subsidence under the Rome trough and the rifted Appalachian continental margin. 

The Depositional Environment of the Middle 

Ordovician Fincastle Conglomerate 

Chrysa M. Cullather 1 

The Fincastle Conglomerate is the northeasternmost 

of six Middle Ordovician conglomerates located west of the 

Blue Ridge structural front in the southern Appalachians. 

These conglomerates and their associated sands and shales 

are an important record of the early tectonic history of the 

Blue Ridge and the Appalachian basin. They are interpreted 

as a clastic wedge derived from a southeastern source area. 

The Fincastle Conglomerate is distinct from the other 

Middle Ordovician conglomerates because it consists dominantly of terrigenous clasts. 

The Fincastle Conglomerate is restricted to the overturned Pine Hills syncline, located 0. 96 km north of the 

town of Fincastle, Va. The syncline trends N. 30° E. for 

1 1500 South Barton Street, No. 597, Arlington, VA 22204. 

about 3 km and is truncated to the southwest by the Salem 

fault. The total exposed thickness ranges from 15 to 50 m. 

Shales, siltstones, and litharenites are discontinuously interbedded with granule to boulder conglomerates. The conglomeratic zones range in thickness from 0.30 to 4.09 m. 

The grains of the litharenites and the clasts of the conglomerates are thought to have been derived from the Early 

Cambrian Chilhowee Group, Cambrian and Ordovician 

limestones, and sediments from within the basin of deposition. 

Eight facies units can be recognized. These are ( 1) 

matrix-supported granule to boulder conglomerate and 

coarse-grained pebbly sandstone, (2) clast-supported granule to boulder conglomerate, (3) fine- to medium-grained 

sandstone, (4) laminated to bedded siltstone, (5) massive 

and finely laminated shale, (6) discontinuously interbedded 

conglomerate, coarse-grained sandstone, and shale, (7) 

interbedded shale and sandstone, and (8) convolute bedded 

shale. These units are interpreted as having been deposited 

by submarine gravity flows. Sedimentary structures include 

normal and reverse grading, convolute bedding, load casts, 

loaded flute marks, and intraformational shale clasts. Crosslamination, ripple marks, and imbrication are very rare. The 

dominant depositional processes thought to be responsible 

for the facies of the Fincastle Conglomerate are classified as 

mass sediment movement. The processes interpreted as 

being active during the Middle Ordovician include debris 

flows, high-, medium-, and low-density turbidity currents, 

grain flows, liquefied and fluidized flows, slumping, and 

rockfalls. The nature of these lithofacies, the sedimentary 

structures, and the implied depositional mechanisms indicate that the Fincastle Conglomerate was deposited from an 

eastern source in a submarine channel at the base of a 

Middle Ordovician paleoslope. 

Regional Stratigraphy of Silurian Rocks and an 

Enigmatic Ordovician Diamictite, Southeastern 

New York 

jack B. Epstein 

Fluvial, tidal-flat, and shallow-marine rocks of Silurian age in a generally fining-upward sequence were deposited northwestward of a linear highland that was uplifted 

during Taconic orogenesis from eastern Pennsylvania to 

southeastern New York. The regional stratigraphic relations 

of these strata generally have been poorly understood. The 

sequence in the northern part of the area near High Falls, 

N.Y., is firmly established and consists of, from the base 

upwards, the Shawangunk Formation (conglomerate, sandstone, shale), High Falls Shale (red beds), Binnewater 

Sandstone of Hartnagel (1905), and Rondout Formation 

(dolomite and limestone) (fig. 1). However, current mapping southwest of High Falls suggests that the 

Program and Extended Abstracts 3 
DELAWAFE WALLPACK PORT WURTSBORO HIGH 

FALLS 

I 4000 

3000 

m 

!: 

u; 2ooo C/) 

UJ 

z 

:X:: 

() 

LEHIGH GAP 

I 

WIND GAP WATER GAP BEND 

I I I 

·I 

POXONO 

BLOOMSBURG 

JERVIS OTISVILLE ELLENVILLE 

I I I 

·I NEW YORK -----+1 

NEW YORK 

PENNSYLVANIA 

iE -------- 1000 

0 20 40 60 80 100 120 

DISTANCE, IN Ml LES 

Figure 1. Generalized stratigraphic section showing the regional relations of Silurian rocks between southeastern New 

York and eastern Pennsylvania. Dashed lines indicate inferred contacts in areas of nonexposure or incomplete mapping. 

facies mosaic from New York through New Jersey and into 

Pennsylvania is more complex than previously reported. 

The Silurian sequence thins markedly from Pennsylvania to southeastern New York (fig. 1). The Shawangunk 

Formation of eastern Pennsylvania consists of three 

quartzite-conglomerate units (Weiders, Minsi, and Tammany Members) and a unit containing appreciable shale and 

some red beds (Lizard Creek Member). Farther southwest 

in Pennsylvania, only a basal quartzite (Tuscarora Sandstone) and shale-sandstone sequence (Clinton Formation) 

can be recognized. In New Jersey, the shales of the Lizard 

Creek become less abundant, and the member cannot be 

mapped to the northeast, but scattered intervals of shale, 

some containing red beds, persist into southeastern New 

York. These shales are generally not mappable, except 

locally, and appear to lie at various levels within the 

Shawangunk. The "Otisville Shale," named previously for 

beds that were believed to contain enough shale to be a 

distinct formation near Otisville, N.Y., fails the test of 

mappability and should be abandoned. 

4 Appalachian Basin Symposium 

The contact between the Bloomsburg Red Beds and 

Shawangunk Formation has been traced without complication from eastern Pennsylvania to Port Jervis, N.Y. 

Between Wurtsboro and Ellenville, red beds and gray 

sandstone and shale overlie the Shawangunk. Because of a 

similar sequence of red and gray rocks at High Falls, many 

workers have identified these units as the High Falls and 

Binnewater, respectively. Detailed and reconnaissance 

mapping suggests, on the contrary, that the red-bed 

sequence between Wurtsboro and Ellenville is a tongue of 

the Bloomsburg, and not the High Falls, and the overlying 

gray sandstone and shale are a tongue of the Shawangunk, 

and not the Binnewater. The High Falls Shale, which is 

very poorly exposed, crops out above the tongue of the 

Shawangunk near Wurtsboro. The tongue of the 

Bloomsburg disappears northeastward by gradual change in 

color from grayish red, through olive gray, into gray. In the 

past, the name "Guymard Quartzite" was applied to a 

portion of the tongue of the Bloomsburg, but this unit, like 

the "Otisville Shale," is unmappable and stratigraphically 
inappropriate. The rocks in the tongue of the Shawangunk 

contain quartzites that are more distinctly crossbedded than 

those in the lower part of the formation. The tongue also 

contains scattered red beds and polymictic conglomerates, 

some of which are similar to rocks in the Green Pond 

Conglomerate exposed in an outlier about 25 mi ( 40 km) 

southeast of the main outcrop belt. It is possible that the 

Shawangunk tongue of the main outcrop belt becomes 

thicker and encompasses most of the section in the Green 

Pond outlier. 

The High Falls Shale at High Falls contains not only 

red shales similar to those of the Bloomsburg but also 

abundant dolomite, fine-grained limestone, and green 

shale. Ripple marks and desiccation cracks are abundant. 

These rocks are very similar to rocks within the Poxono 

Island Formation of eastern Pennsylvania, so the two 

formations probably grade into each other. The High Falls 

and Poxono Island are very poorly exposed, and the 

location of the boundary between them has not been 

defined. The Binnewater Sandstone, which consists predominantly of crossbedded sandstone near High Falls, loses 

its character about 6 mi (9.6 km) to the southwest and 

pinches out within the Poxono Island. Thus, the Binnewater, High Falls, and Poxono Island are all part of a complex 

carbonate-siliciclastic marginal marine sequence. 

The consequence of this study has been to better 

define the stratigraphic variations in Silurian rocks in 

southeastern New York. It demonstrates that the name 

"High Falls Shale" is incorrectly used on the most recent 

New Jersey State geologic map for rocks that should be 

referred to as the Bloomsburg Red Beds. Present studies are 

concentrating on the petrology and sedimentology of these 

rocks. 

A thin diamictite (interpreted to be colluvium), generally less than 1 ft (0.3 m) thick and interbedded with a 

sticky clay containing slickensided quartz vein fragments 

(fault gouge), and a deposit of semiconsolidated shale 

fragments from the Martinsburg Formation (shale-chip 

gravel) have been found at several localities between the 

Martinsburg and Shawangunk Formations in southeastern 

New York. The diamictite is dark yellowish orange and 

consists of a poorly sorted, semiconsolidated mixture of 

angular to rounded clasts in a sand-silt matrix. The clasts 

comprise fragments of the underlying Martinsburg, quartz 

pebbles similar to those found in the overlying Shawangunk, and exotic pebbles and cobbles that are dissimilar to 

rock types immediately above or below the unconformity. 

Many cobbles show evidence of exposure to weathering 

prior to incorporation in the diamictite. The source of the 

pebbles is enigmatic and is still under investigation. 

These data add an interesting, hitherto unrecognized, 

chapter to Late Ordovician paleogeography in the central 

Appalachians during the Taconic hiatus, a period of 20 to 

30 million years. They suggest Taconic uplift of deep-water 

Martinsburg shales and graywackes, subaerial exposure, 

deposition of colluvium and shale-chip gravel, and incorporation of exotic pebbles and cobbles in the diamictite. 

Much of this material was subsequently removed during 

pre-Shawangunk erosion, and only scattered occurrences 

remain. The exotic clasts were derived from a source that is 

no longer exposed nearby. Perhaps the source was in 

Taconic thrust sheets that were subsequently eroded. These 

deposits were later covered by the coarse clastic sedimentary rocks of the Shawangunk Formation during Middle 

Silurian time. 

REFERENCE CITED 

Hartnagel, C.A., 1905, Notes on the Siluric or Ontario section of 

eastern New York: New York State Museum Bulletin 80, p. 

342-358. 

The Origin of the Pennsylvania Salient and 

COP Seismic Imaging of the Cornwall-Kelvin 

Displacement along the U.S. Atlantic 

Continental Margin 

Robert C. Milici1 and Kenneth C. Bayer 

Except for the Pennsylvania salient, the major 

salients and recesses of the central . and southern Appalachians show little or no relationship to deflections of 

regional gravity and magnetic trends. Nevertheless, it has 

been postulated that all of these salients and recesses have a 

common origin and are inherited from the configuration of 

the Late Proterozoic North American continental margin 

that was formed upon the opening of the Iapetus Ocean. In 

contrast, we postulate that the Pennsylvania salient is a 

unique, younger feature. As such, it was formed by 

differential movement along an east-west-trending rightlateral shear during the early Mesozoic opening of the 

Atlantic Ocean. 

The latter hypothesis relates movement along this 

east-west-trending fracture zone (the Cornwall-Kelvin displacement) to the Kelvin seamounts, the deformed Mesozoic strata in the narrow neck between the Newark and 

Gettysburg Mesozoic basins, and the conspicuous rightlateral bending of major geologic and geophysical features 

from the Pennsylvania salient to the Atlantic Ocean. The 

fracture zone apparently propagated both landward and 

seaward from the postrift continental margin. On the 

continent, the zone is buried beneath strata· of Cretaceous 

age and younger; however, it can be identified on CDP 

(Common Depth Point) seismic profiles along the continental shelf between the deepest part of the Baltimore Canyon 

1 Virginia Division of Mineral Resources, Charlottesville, VA 

22093. 

Program and Extended Abstracts 5 
trough and the Long Island platform. North-northwestdirected compressional forces generated by this right-lateral 

shear may be the cause of some of the deformation reported 

by other workers in the Appalachian Plateau regions of New 

York and Pennsylvania. 

Lateral Ramps and the Structure of the Central 

and Southern Appalachians, with Implications 

for Thrust Belts Worldwide 

Howard A. Pohn 

Field mapping combined with side-looking airborne 

radar (SLAR) and with proprietary seismic reflection data 

demonstrates that lateral ramps are significant structural 

elements of the Eastern Overthrust Belt. 

Lateral ramps, which are zones where decollements 

change stratigraphic level along strike, are recognized on 

SLAR data by abrupt changes in fold wavelength along 

strike or by zones of fold plunges across strike. Other 

surface criteria for recognition of lateral ramps include 

conspicuous changes in frequency of faults, long, linear 

river courses that cross the Piedmont, Atlantic Coastal 

Plain, or Appalachian Plateau, abrupt changes in strike or 

presence of gaps in the Blue Ridge, and interruption of 

eastern Mesozoic basins by east-west border faults or by 

blocks of Precambrian rocks. 

Examination of more than 150 proprietary seismic 

reflection profiles in the central and southern Appalachians 

confirms the presence of lateral ramps and shows their 

detailed configuration in the subsurface. Strike-line reflection profiles across lateral ramps show a structural complexity closely resembling typical dip lines in areas of complex 

thrust faulting. 

Frontal ramps have long been known to control the 

presence and orientation of folds that form perpendicular to 

the direction of transport. Data from my study indicate that 

the sizes and location of these fold plunges are controlled by 

the change in stratigraphic level of decollements across 

lateral ramps. 

Lateral ramps have been seen throughout the central 

and southern Appalachians. SLAR and Landsat data indicate that lateral ramps are also present in the Ouachitas, the 

Western Overthrust Belt, the Brooks Range, northwest 

Africa, Papua New Guinea, and southeastern China, in 

effect everywhere that thin-skinned tectonics dominates the 

style of deformation. 

In the Eastern Overthrust Belt, lateral ramps are 

coincident with nearly 50 percent of modem earthquakes, 

although the ramps themselves occupy no more than 15 

percent of the geographic area. That this localized seismic 

activity may have ruptured seals above hydrocarbon reservoirs accords with the observation that lateral ramps and 

hydrocarbon-producing fields are nearly mutually exclusive. 

6 Appalachian Basin Symposium 

The generation of lateral ramps is believed by the 

author to be related to the reactivation of a fundamental 

Precambrian fracture system, and it is hypothesized that this 

system produced zones of least resistance that became 

transform faults as continents separated during episodes of 

sea-floor spreading. 

Carboniferous Petrographic Trends in the 

Central Appalachian Basin: An Orogenic 

Interpretation 

Joseph T. O'Connor 

Carboniferous clastic rocks from the central Appalachian basin show petrographic trends in texture and composition that may relate to Alleghanian orogenic activity. 

The analysis and interpretation of the Pennsylvanian sandstone petrography presented here follow formal stratigraphic subdivisions, but because of unresolved areal differences in nomenclature, the presentation is divided into 

northern and southern parts. The study is based on the 

examination of about 500 thin sections of Carboniferous 

sandstones and on review of work published by other 

authors. 

Upper Mississippian Sandstones 

These sandstones tend to be mineralogically mature 

and deposited in fluvial and (or) coastal environments. They 

appear to be derived from tectonically stable terranes 

possibly including igneous and metamorphic rocks to the 

southeast and the northwest. The sandstone contains predominantly quartz grains, relatively few rock fragments, 

and 1 to 2 percent rounded and abraded potassium feldspar 

grains. 

Pennsylvanian Sandstones-Southern Area 

All of the Pennsylvanian sandstones examined by the 

author are quartz-dominated clastics (quartz content 

between 50 and 100 percent). The quartz content of 

individual stratigraphic units is quite variable, is dependent 

upon several provenance-related and depositional factors, 

and is not generally a reliable indicator of depositional 

environment. Only some siltstone and finer grained rocks 

had quartz contents below 50 percent, and very few of the 

coarser sandstone samples had quartz contents greater than 

95 percent. 

1. The sandstones of the Pocahontas Formation (earliest 

Pennsylvanian) of Virginia and West Virginia contain 

relatively abundant potassium feldspar and plagioclase and 

also contain broken and angular quartz grains. Rare mafic 

minerals and the textural immaturity of the sandstones 
probably indicate increased tectonic activity in the southeastern source area. These immature sandstone units alternate with more mature sandstone units that are similar to 

those of the Mississippian. 

2. The composition of the sandstones of the Early Pennsylvanian New River Formation of West Virginia is markedly different from those of the Pocahontas Formation, 

although both derived their sediments from the same general southeastward direction. The sandstones of the upper 

part of the New River Formation consist of a mixture of 

reworked quartz grains, micaceous and chloritic rock fragments, and clay minerals (detrital and authigenic) and were 

derived almost wholly from sedimentary and low-grade 

metamorphic terranes. The sandstones of the lower part of 

the New River Formation appear to be transitional in 

composition and texture between those of the Pocahontas 

Formation and those of the upper part of the New River 

Formation. The author suggests that a belt of folded and (or) 

thrusted Paleozoic sedimentary rocks emerged between the 

eastern orogen and the basin (east of what is now the West 

Virginia-Virginia border) to create a source for the new 

feldspar-impoverished sediments for both parts of the New 

River Formation. This same belt may have blocked off or 

overwhelmed the sediment source from the older orogen 

during the time of deposition of the upper part. To the 

south, in Kentucky and southeastern Virginia, the petrographic trends are poorly understood, but the paleocurrent 

directions of the Lee Formation equivalents of the New 

River Formation suggest that sediment for this unit was 

supplied from both the eastern and northwestern sources. 

3. Sandstones of the Kanawha Formation (Middle Pennsylvanian): 

A. The sandstones of the lower part of the Kanawha 

Formation in West Virginia show an abrupt compositional transition from those of the New River Formation. 

Untwinned albite and twinned oligoclase-andesine are 

relatively abundant mineral phases in these clastic rocks 

along with twinned and untwinned potassium feldspar 

and microperthite. Biotite or chlorite pseudomorphs of 

biotite and muscovite are more abundant in the lower 

part of the Kanawha. Relict sedimentary features (partial 

quartz overgrowths and broken rounded grains) are not 

as common in the lower Kanawha sandstones, and relict 

"granitic" and low- to middle-grade metamorphic rock 

fragments make up some of the clasts of this unit. These 

features imply that the sedimentary-rock-dominated 

source area for the upper part of the New River Formation was replaced by one in which igneous and metamorphic rocks were the main components. 

B. The sandstones of the middle part of the Kanawha 

Formation are compositionally similar to those described 

for the lower part of the formation. The plagioclase to 

potassium feldspar ratio is variable in these rocks, 

possibly decreasing in the upper part of the unit, 

although the total feldspar increases to greater than 10 

percent locally. Biotite (or chlorite pseudomorphs) 

remains as a scant but ubiquitous mineral phase. The 

occurrence of many marine and brackish-water zones in 

this part of the section suggests that these rocks were 

deposited in lower delta plain or near shore environments. The middle Kanawha sedimentary rocks appear 

to mark a period of continued erosion of an igneous and 

metamorphic source area. 

C. The sandstones of the upper part of the Kanawha 

Formation are very immature and contain a relatively 

high percentage of potassium feldspar (4 to 12 percent) 

as microcline, cryptoperthites and microperthites, and 

some zoned orthoclase. The plagioclase to potassium 

feldspar ratio drops noticeably in the upper part of the 

Kanawha Formation through the diminution of 

untwinned albite, which is abundant in the lower and 

middle parts. The relict rock-fragment fabrics indicate 

that metamorphic rocks were a major contributor to the 

sedimentary deposits, but surprisingly, neither igneous 

nor high-grade metamorphic rock fragments have been 

observed in these sandstones. The freshness of the rock 

components, however, implies that a high-grade metamorphic and igneous "basement" was close at hand, 

perhaps as part of an advancing thrust plate that overwhelmed the provenance supplying sedimentary and 

low-grade rock fragments to the middle part of the 

Kanawha Formation. 

Pennsylvanian Sandstones- Northern Area 

1. In the area of study, the Pottsville Formation is represented by the upper Connoquenessing Sandstone Member, 

the Mercer Member, and the Homewood Sandstone Member, all of Middle Pennsylvanian age. The Pottsville is, 

therefore, a partial equivalent of the Kanawha Formation. 

The arenites of the Pottsville Formation in this area are 

composed of conglomerate and sandstone derived from an 

entirely sedimentary or low-grade metamorphic source 

area. High-grade metamorphic and igneous terranes were 

apparently not exposed to erosion in the source areas for 

these units during this time. 

2. The Allegheny Formation, in northern West Virginia, 

Maryland, and Pennsylvania, is a sequence of Middle 

Pennsylvanian fluvial strata that contain a mixture of 

feldspar-rich and feldspar-impoverished quartzose sandstones. Diagenetic alteration of the sandstones is very 

extensive in the strata and greatly impairs mineralogic 

classification. However, the identified mineral and clast 

contents indicate derivation from a mixture of source 

terranes that could include sedimentary, metamorphic, and 

Program and Extended Abstracts 7 
igneous rocks. The author suggests that, by the time of 

Allegheny Formation deposition, the Alleghanian orogeny 

had largely homogenized the source area. 

Interpretations of Sedimentary Patterns in the 

Pennsylvanian of the Central Appalachian Basin 

Charles L. Rice 

The Pennsylvanian central Appalachian basin was a 

foreland basin development that was controlled by the 

emplacement and western migration of thrust sheets on the 

North American continental margin. Only the northwestern 

side of the basin, a southeastward-thickening prism of 

coal-bearing sandstone and siltstone, is preserved. The lack 

of easily recognizable regional datums, the rapid facies 

changes of these largely coastal plain deposits, and the 

ruggedness of the topography of the thicker (as much as 

1 ,450 m) southeastern part of the prism have hampered 

development of a comprehensive understanding of depositional patterns during the Pennsylvanian. Whereas the 

distribution of Middle and Upper Pennsylvanian sediments 

generally agrees with the predicted sedimentary model, that 

is, an upward-coarsening clastic sequence reflecting westward migration of the orogen and its deltas, the Lower 

Pennsylvanian contains as a western facies the anomalously 

coarse-grained and conglomeratic quartz arenites of the 

New River and Lee Formations. The latter formations have 

been interpreted as beach and barrier-bar deposits fringing a 

northwestward-thinning delta complex. However, evidence 

of fluvial origin for these sandstones is abundant (they 

contain unidirectional crossbedding, which parallels their 

broadly linear geometry, and form persistent upward-fining 

channel-in-channel units that commonly contain plant fossils and thin coal beds), and they are here interpreted as 

braided-stream deposits for which the emergent craton was 

an important source area. 

The presence of many thin deposits of epicontinental 

seas in the upper Middle and Upper Pennsylvanian sections 

in the northwesternmost part of the Appalachian basin and 

in the Illinois basin has led to an exaggeration of the 

importance of that area as a depocenter for clastics derived 

from the Appalachian orogen and has tended to obscure the 

fact that the essentially linear central Appalachian basin 

oriented along the continental margin was closed at its 

northeastern end and open to the south and southwest during 

much of the Pennsylvanian. This basin configuration is 

indicated by many southwest- to southeast-oriented channels and paleovalleys filled with Pennsylvanian clastics that 

have been identified both in outcrop and in the subsurface of 

the Mississippian/Pennsylvanian unconformity in areas 

8 Appalachian Basin Symposium 

west of the limits of the Pocahontas Formation. These 

features appear to be part of a coherent southwest-trending 

drainage pattern that is corroborated by numerous studies of 

paleocurrent directions in the basal Pennsylvanian sandstones. Thus, the thick (almost 500 m) Lower Pennsylvanian sequences of conglomerates and conglomeratic quartz 

arenites near the southeastern margin of the Pennsylvanian 

outcrop belt in southwestern Virginia and southeastern 

Kentucky are not the conglomeratic facies of northwestfacing deltas as suggested by some workers but represent 

deposits of braided streams that flowed toward a major 

southern depocenter that is now largely eroded away. 

Studies of the distribution and crossbedding of Middle 

Pennsylvanian strata in this area also may indicate a strong 

influence of that depocenter on sedimentation patterns and 

show major southwest sediment transport during that time. 

Depositional Trends in Late Paleozoic CoalBearing Strata of the Central Appalachian Basin 

Kenneth j. Englund and Roger E. Thomas 

The deposition of terrestrial coal-bearing strata in the 

central Appalachian basin began in Late Devonian time in 

association with westward-prograding delta lobes situated 

along the eastern margin of the basin. Most sediments were 

derived from siliciclastic detritus eroded from tectonic 

highlands that were elevated to the east by plate collision 

during the Acadian orogeny. During Mississippian time, 

terrestrial sediments continued to prograde westward in the 

slowly subsiding foreland basin, and by Early Pennsylvanian time they extended onto the cratonic shelf. Marine 

deposition prevailed in a shallow epicontinental sea on the 

cratonic shelf and periodically encroached eastward over 

the terrestrial sediments. A transition from marine to 

terrestrial deposition is recorded by time-equivalent 

sequences of (1) marine limestone and shale, (2) barrierand offshore-bar sandstone, (3) lagoonal and bay-fill shale, 

(4) coal and related swamp deposits, and (5) fluvial and 

deltaic sandstone. Westward progradation was dominant 

during periods of increasing rainfall and sufficient subsidence to accommodate a high influx of clastic sediments, 

whereas marine incursions extended eastward during periods of decreasing rainfall and low clastic input. Periods of 

equilibrium, as during the change from regression to transgression, were accompanied by stillstands of sea level and 

the development of widespread peat swamps and longshore 

bars. In Early Pennsylvanian time, the strandline or wedgeout of terrestrial coal-bearing deposits changed from N. 30° 

E. to N. 65° E., probably in response to collision with the 

African plate during the early phase of the Alleghany 

orogeny. As the Appalachian basin evolved and the plates 
continued to merge, terrestrial deposits extended farther 

northwestward and, by Middle Pennsylvanian time, occupied the entire central Appalachian basin. The apparent 

effects of plate collision on sedimentary patterns are 

reflected also in a similar change in the strike of deformed 

strata in the faulted and folded Appalachians. 

Eocene Igneous Intrusive Rocks of the Central 

Appalachian Valley and Ridge Province 

C. Scott Southworth and Karen J. Gray 

Late Eocene basaltic and rhyolitic dikes, sills, plugs, 

and diatremes intruded Paleozoic rocks of the Valley and 

Ridge province of the central Appalachian basin. Two main 

areas of silicic rocks surrounded by basaltic rocks are found 

in Pendleton County, W. Va., and Highland County, Va. 

Major-element and trace-element geochemistry of 46 samples of probable Eocene age suggests a mantle or lower 

crustal source of rift-related origin. Minimal mixing of the 

igneous rock with crustal rock, little contact metamorphism, and consistent radiometric dates of late Eocene age 

suggest that the igneous activity was short lived. No 

evidence of surface extrusions is preserved after 46 m.y. of 

erosion. 

The proximity of Eocene igneous rocks to the western 

terminus of Late Jurassic igneous dikes suggests emplacement along possibly reactivated basement faults. A change 

in the regional strike of Jurassic alkalic igneous dikes across 

the zone indicates a variation in stress during Mesozoic 

extension. Both concordant and discordant relationships of 

Eocene rocks with allochthonous Paleozoic country rock 

allow only generalizations about the structural trend of the 

crustal fracture. Insufficient geologic data are available to 

suggest that the basement fracture zone is the eastward 

extension of the 38th Parallel lineament or a fault of the 

Cambrian Rome trough. 

A possible tectonic model for the Eocene igneous 

intrusive rocks in this region is extensional reactivation near 

the intersection of two basement fracture zones, a growth 

fault parallel to regional strike that is of Paleozoic age and 

a cross-strike basement fault. Lateral boundaries of 

duplexes formed in Cambrian-Ordovician carbonate rocks, 

tectonic ramps at the lowermost decollement above basement, and tear faults that bound allochthonous blocks on the 

folded Appalachian Plateau province may reflect the basement faults (fig. 1). 

The igneous intrusive rocks provide evidence that 

basement faulting has taken place in the Appalachian Valley 

and Ridge province since the Alleghanian orogeny. The role 

that basement fractures played in the thin-skinned deformation and Cenozoic tectonics can be determined only by 

detailed mapping and subsurface investigations. 

The Geologic Framework of the Continental 

Shelf and Slope of Virginia, with Emphasis on 

Petroleum Geology 

Kenneth C. Bayer and Robert C. Milici1 

Stratigraphic intervals selected from publicly available seismic common depth point (CDP) reflection profiles 

from the Virginia Coastal Plain eastward to the continental 

rise were used to evaluate the oil and gas potential of the 

Virginia onshore-offshore area. Our reconnaissance seismic 

survey consisted of 729 statute miles (1, 173 km) of profiling across approximately 15,000 mi2 (38,850 km2

). 

Four identified stratigraphic reflectors (top Upper 

Cretaceous, top Lower Cretaceous, top Upper Jurassic, and 

an acoustic basement reflector) were correlated with the 

COST (Continental Offshore Stratigraphic Test) B-2 well. 

Depths were calculated from the same traveltimes from 

which isopach and structure contour maps were constructed. Preliminary results from the Shell B-92-1 well, 

drilled through Cenozoic and Mesozoic strata, offshore 

Virginia, and from wells adjacent to our Virginia study 

area, indicate low source-rock quality and thermal immaturity for Cenozoic and Mesozoic rocks. Therefore, deposition was probably in an oxidizing, open-shelf environment. 

On the Continental Shelf, the acoustic "basement" 

reflector (ABR) is generally the most dominant, continuous 

band of seismic energy on the seismic profiles. The band 

suggests a relatively dense, thick sequence of dolomite or 

limestone. The postrift (probably Early to Middle Jurassic) 

ABR overlies older Triassic synrift basins, such as the 

Norfolk basin, offshore Virginia, and may act as a seal or 

trap. 

Offshore Mesozoic basins, the Norfolk for example, 

and onshore concealed Mesozoic basins, such as the Taylorsville basin, may contain sandstones, shales, and interbedded carbonates analogous to the exposed Triassic basins 

of eastern Canada and the United States. The depth of burial 

of the basins is insufficient to create the thermal maturation 

temperatures necessary for the generation of liquid hydrocarbons. However, the basin's rocks could act as reservoirs 

if hydrocarbons migrated laterally from offshore strata of 

equivalent age or vertically from older Paleozoic strata. 

Although defined seismically, and as yet untested, 

stratigraphic traps on the Outer Continental Shelf may be 

important in future wildcat drilling. Recent offshore drilling 

indicates Middle to Upper Jurassic rocks as the most 

favorable hydrocarbon source rocks. Thus, the updip pinch 

out of the Jurassic, west of seismic CDP line 10 and east of 

the Virginia coastline, may be a suitable target for hydrocarbon exploration. Offshore from Virginia, additional 

1 Virginia Division of Mineral Resources, Charlottesville, VA 

22903. 

Program and Extended Abstracts 9 
A 

FOLDED I' .' 

APPALACHIAN 1 

I 

I 

PLA~EAU ,., . \ I / \ 

D-M 

~ ( 

\ 

I 

I 

I 

,' /. ~ I (, .. " 

\ 

i I __., 

I J • .. 

I ,.'i\., ~ ·~ ,, .. . / I ::L ,• .. !.fJ.I!· I I ...... : .'t.l, .. . I • ,. t • I I 

ANTICLINORIUM 

0-S-D 

'i BROADTOP -. / I. 

/ 

NITTA NY 

• 

SYNCLINORIUM 

S-D-M 

0 5 10 MILES 

0 5 IOKILOMETERS 

- Eocene intrusions M Mississippian 

= Jurassic intrusions D Devonian 

--v- North Mountain thrust fault s Silurian 

0 Ordovician 

) 

N 

I 

ELKINS VALLEY BLOCK 

DIKES 

MOUNTAIN THRUST SHEET 

A 

A' 

A' 

Figure 1. Tectonic model for the jurassic and Eocene igneous intrusive rocks of the central Appalachian Valley and Ridge 

province. Extensional reactivation near the intersection of a growth fault and cross-strike fault in basement rocks may 

relate to Alleghanian cross-strike structures . £ , Cambrian . [Southworth and Gray abstract] 

10 Appalachian Basin Symposium 
stratigraphic, clastic-wedge traps near the shelf edgepinch 

out against the ABR and Upper Jurassic to Lower Cretaceous rocks, which are reef or carbonate bank deposits on 

the continental slope. On the Outer Continental Shelf, 

horsts and grabens in older, prerift Paleozoic strata are 

identified as possible traps for hydrocarbon accumulations. 

We rate the potential of the Virginia continental 

margin to contain commercially recoverable hydrocarbons 

as fair (moderate) to poor (low). Structural traps on the 

continental slope may continue as prime drilling objectives; 

however, we suggest employing a drilling program to 

evaluate stratigraphic traps on the Continental Shelf. In 

shelf waters, drilling at a depth of 20,000 ft (6, 100 m) is 

recommended to explore below the acoustic basement rocks 

for either locally derived or migrated hydrocarbons. 

Petrographic Characteristics of the New River 

Formation of the Central Appalachian Basin 

Joseph T. O'Connor and Nelson L. Hickling 

The New River Formation lies stratigraphically 

between the lowest Pennsylvanian Pocahontas Formation 

and the lower Middle Pennsylvanian Kanawha Formation of 

the central Appalachian basin in Virginia, West Virginia, 

and Kentucky. The Pocahontas and Kanawha Formations 

contain abundant clastic sedimentary rocks that were 

derived from igneous and medium- to high-grade metamorphic source rocks; paleocurrent measurements from West 

Virginia indicate that the source areas for all three formations are to the southeast of the current location of the basin. 

Examination of more than 200 thin sections of surface 

and core samples from sandstones of the New River 

Formation and perusal of existing petrographic data show 

that this formation may be separated petrographically into 

two parts. The upper part of the New River Formation, 

which is here defined as all units from the top of the Nuttall 

Sandstone Member down to the top of the Raleigh Sandstone Member, is characterized by a very low (biotite + 

chlorite)/muscovite ratio and a virtual absence of feldspar. 

Some sandstone units in the lower part of the New River 

Formation, which includes all units from the top of the 

upper Raleigh Sandstone Member to the bottom of the 

formation, are characterized by a moderate (biotite + 

chlorite)/muscovite ratio and moderate to abundant quantities of feldspar. A coarse-pebble channel-filling conglomerate in southwestern Virginia has been correlated with the 

lower part of the New River Formation by Englund and 

Thomas (USGS Research on Energy Resources-1988 

Program and Abstracts, U.S. Geological Survey Circular 

1 025). This conglomerate contains pebbles of arkosic sandstone and metasandstone, granitic igneous rocks, and highgrade metamorphic rocks. The arkosic sandstone and 

metasandstone pebbles are mineralogically and texturally 

similar to Cambrian Chilhowee Group sandstone. 

Because the upper part of the New River Formation 

lacks mineral phases of igneous or high-grade metamorphic 

derivation and because an effective depositional mechanism 

for removing such phases from the host rock does not 

appear to occur in this area, we conclude that the upper part 

of the New River Formation was derived from a sedimentary and low-grade metamorphic source area. The source 

rocks were almost certainly the earlier Paleozoic section 

now exposed in the fold-and-thrust belt of the Appalachian 

basin. The lower part of the New River Formation exhibits 

a compositional transition between the Pocahontas Formation provenance, which included igneous and metamorphic 

rocks from the Late Mississippian orogen, and the mainly 

sedimentary provenance of the upper part. 

Economic Geology of the Big Chimney 

Quadrangle, Kanawha County, West Virginia 

John F. Windolph, Jr. 

Recent geologic mapping of Pennsylvanian strata in 

the Big Chimney quadrangle 2.5 mi (4 km) northeast of 

Charleston, W.Va. , suggests a possible association between 

syntectonic depositional influences and the occurrences of 

economically important mineral deposits. Coal and flint 

clay were deposited in the Middle Pennsylvanian Charleston Sandstone during periods of stillstand. The Mahoning 

sandstone is disconformable with underlying strata and 

locally contains Precambrian and Early Paleozoic pebbles. 

The member is thick in synclinal troughs and thin or absent 

on the crests of anticlines. These anticlines also have a 

thinner underlying stratigraphic sequence. 

Flint clay deposits reach their maximum quality on 

the crests of anticlines and in areas adjacent to suspected 

paleotopographic highs. These deposits are laterally gradational with underclay, ganister, and paleosol. The Elk fire 

clay (No. 6 Block underclay) may in part have originated as 

a volcanic ash fall. The No. 5 Block coal bed reaches 60 in 

(152 em) in thickness on the Milliken anticline and has 

minor fault displacement at Big Chimney. The Pittsburgh 

coal bed is as much as 90 in (229 em) thick, cropping out in 

high ridges. It is absent on the northern edge and eastern 

part of the quadrangle. 

More than 260 oil and gas wells have been drilled in 

the overlapping Elk-Poca, Big Chimney, and Blue Creek 

gas or oil fields. Natural gas, paraffin-base oil, and (or) 

minor amounts of condensate are produced from structural 

and stratigraphic traps in four units: the Weir sand and the 

Oriskany, Keefer, and Tuscarora Sandstones. The Oriskany 

Sandstone, however, is used almost exclusively as a gas 

storage reservoir. Oil is produced largely from repressurized stripper wells. 

Program and Extended Abstracts 11 
Table 1. Stratigraphic nomenclature and correlations of the Chilhowee Group in the 

central and southern Appalachians 

[Thickness in meters] 

Southern Appalachians Central Appalachians 

East-central Northeasternmost NE. Roanoke to South Mountain, Age Tennessee 

Chilhowee Tenn. to SW. Northern Maryland and 

Mountain Virginia Virginia Pennsylvania 

Shady Dolomite Shady Dolomite Tomstown Dolomite Tomstown Dolomite 

Helenmode 

Member 

35-45 

Hesse 

~ Quartzite 0 ~ ·~ Member Erwin Antietam Antietam (';J 

'i: § 203-210 ~ ,0 Formation Formation Formation (';J E & Murray 'i: 0.. ,0 (';J ::l Shale fj u ~ ~ 200-550 200-330 130-275 ...... ·~ Member u v 

~ v ~ 50-110 0 v .....:1 ~ Nebo 0 

= Quartzite :.2 

u Member 

35-108 

Nichols Hampton Harpers Harpers 

Shale Formation Formation Formation 

40-145 380-558 340-520 105-800 

..... 

o-C'-• Cochran Unicoi Weverton Weverton 

o- u-- Formation* Formation Formation Formation ..... C'-· ·-0 (';J ~ u-- N.- 110-185 300-755 120-470 490-658 ·- ~ e..s 0 (';J 2 E 

Mou~~ctin~ 0 N ·-...... 0 (';J 1-<,0 Q::U Rogers Formation and 2 E Ocoee 2 (';J ~ ~ Formation Swift Run Q..U 0..~ Supergroup 0..0 Basement Formation Basement ~.....:I Rocks Rocks 

* Fault truncation 

Stratigraphy, Sedimentology, and Economic 

Potential of the Chilhowee Group in the Central 

and Southern Appalachians 

K.Y. Lee 

A detailed stratigraphic and sedimentologic study of 

the Lower Cambrian Chilhowee Group has been carried out 

along the outcrops flanking the Blue Ridge anticlinorium in 

the central and southern Appalachian orogen. The purpose 

of this study is to clarify the provenance, stratigraphic 

sequences, depositional framework, and economic potential 

of sedimentary rocks of the Chilhowee Group. 

The outcrops of the Chilhowee Group in the study 

area occupy a part of the eastern border of the Appalachian 

basin, and they cover an area of about 46,000 km2 that 

include parts of southern Pennsylvania, west-central Maryland, northeastern West Virginia, northern, central, and 

southwestern Virginia, and northeasternmost and eastcentral Tennessee. In the southern Appalachians, the 

Chilhowee Group in the Chilhowee Mountain of east12 Appalachian Basin Symposium 

central Tennessee consists, in ascending order, of the 

Cochran Formation, Nichols Shale, and Erwin Formation 

(table 1). The Erwin is, however, divided into the Nebo 

Quartzite, Murray Shale, Hesse Quartzite, and Helenmode 

Members. In northeasternmost Tennessee and southwestern 

Virginia, this group consists of the Unicoi, Hampton, and 

Erwin Formations. In the central Appalachians, the 

Chilhowee Group from central Virginia to the South Mountain of Pennsylvania consists, in ascending order, of the 

Weverton, Harpers, and Antietam Formations (table 1). 

Generally, the Chilhowee Group is made up of terrestrial 

and marine, detrital, very fine-grained to pebbly quartzconglomeratic sedimentary rocks, locally containing thin 

tholeiitic basalt flows; the Chilhowee Group attains a 

thickness of 1,863 min the Washington County, Va., and 

1, 723 m in the northern part of South Mountain, Pa. Most 

of the lower Chilhowee Group is characterized by the 

arkose, arkosic sandstone, and graywacke intercalated with 

the transverse to linguoid and longitudinal pebbly quartzconglomeratic sheets and lenses. Planar crossbedding in 

which the angles of inclination are greater than 10° is 
common, and trough crossbedding and ripple marks are 

present locally throughout this clastic sequence. The upper 

part of the lower Chilhowee Group and the middle and 

upper Chilhowee Group consist chiefly of thin- to massivebedded quartzite, arkosic sandstone, mudstone, and shale 

and are characterized by herringbone cross-stratification, 

horizontal lamination, and planar crossbedding having 

angles of inclination less than 10° and locally in the upper 

part of this sequence have well-developed ripple marks. 

During the Late Proterozoic, the initial depositional 

framework of the Chilhowee Group along the eastern 

margin of the North American craton consisted of intracratonic rift-faulted depressions in association with plate fragmentation within the Grenville basement rocks. Those rifted 

depressions were filled with the detrital sedimentary rocks 

and volcanic flows of the Catoctin and the Mount Rogers 

Formations and the clastic sedimentary rocks of the Ocoee 

Supergroup. As the sedimentation proceeded within individual depressions, successive subsidence events subsequently permitted the continuation of the deposition of most 

of the lower Chilhowee detrital sedimentary rocks on broad 

flood plains by the braided drainage systems in the southern 

Appalachians and as a coalescent fan and deltaic system in 

the central Appalachians. During this time, an aulacogen 

existed that separated the central Appalachians from the 

Southern Appalachians near Roanoke, Va. Linear, sheeted 

arkose and arkosic sandstone within a thick black shale 

sequence attest to this transition. As subsidence proceeded 

during extensional tectonics, transgression occurred from 

the east. Thereafter, detrital sediments of the upper part of 

Cochran, Unicoi, and Weverton Formations, the Nichols 

Shale, and the Hampton and Harpers Formations were 

deposited in a marine shelf environment; the Erwin and 

Antietam Formations were deposited in a marine coastal 

environment under a relatively stable tectonic regime. The 

Chilhowee strata formed a wedge-shaped sedimentary body 

that thickened seaward toward the shelf edge and thinned 

out toward the ocean basin at the time of deposition. In 

places, the Chilhowee sequence is conformable with underlying detrital sedimentary rocks believed to be found within 

individual depressions. Elsewhere, this sequence unconformably overlies older granitic and metamorphic rocks. 

Discovery of the trace fossil Rusophycus in the upper part of 

the Unicoi Formation of southwestern Virginia places the 

age of the Chilhowee Group into the Lower Cambrian. Age 

of the lower part of Chilhowee would depend on more 

precise radiometric dating of underlying rocks of the Catoctin Formation that give conflicting dates of U-Pb age (810 

m.y.) and Rb-Sr age (570 m.y.). 

Framework modes of the Chilhowee sandstones 

based on the triangle diagrams of quartz and feldspar grains 

and on lithic fragments with three auxiliary plots suggest 

that the multicyclic sands of the Chilhowee were derived 

from the granitic highlands of the North American craton to 

the west and northwest. Monocyclic sands were derived 

from the granitic and metamorphic terranes of a nearby 

magmatic arc along the rifted continental margin. Chemical 

analysis of seven shale samples from the Nichols Shale, 

Hampton Formation, and the Murray Shale Member, 

Tenn., and the Harpers and Antietam Formations, east of 

Buena Vista, Va., confirms that the mode composition of 

Chilhowee sandstones was chiefly derived from the granitic 

terranes. The Chilhowee shales are high in Al20 3 , K20, and 

Ti02 and low in Si02 , Fe20 3 , MgO, CaO, Na20, and P20 5 • 

In comparison with younger Paleozoic shales, these data 

signify a change of shale composition over time. Generally, 

older shales are more enriched in K20 and depleted in N a20 

and CaO than younger shales are. A maturity index, M = 

Al20 3 + K20 I MgO + N a20, has been used for differentiating Paleozoic stratigraphic sequences and provenance 

siting. High content of Ti02 indicates the high concentration of ilmenite minerals in the detrital sediments. 

Organic carbon in two black shale samples, one from 

the Nichols Shale and the other from the Murray Shale at 

the Chilhowee Mountain in Tennessee, shows less than 0.1 

percent organic carbon. Pyrolytic hydrocarbon yields are 

low, 0.08 and 0.03 mg/g, respectively. It is unlikely these 

shales warrant consideration as petroleum source rocks 

(G.E. Claypool, written commun., 1987). Extensive silica 

sands from the Erwin Formation have been quarried in 

central Virginia and South Mountain of Pennsylvania. High 

concentrations of zircon and ilmenite locally from the 

Hampton, Harpers, Erwin, and Antietam Formations have 

important resource potential throughout the study area. 

Provenance and Depositional History of the 

Fincastle Conglomerate of Southwestern Virginia 

Nelson L. Hickling and Harvey E. Belkin 

The Middle Ordovician Fincastle Conglomerate is 

preserved in a tightly folded, overturned syncline near the 

town of Fincastle, southwestern Virginia. It crops out for a 

distance of 2. 7 km along the strike of the synclinal axis. The 

conglomerate conformably overlies the Liberty Hall Shale 

and is conformably overlain by probable Martinsburg Formation, both marine units. The Fincastle, as much as 55 m 

thick, is composed of beds and lenses of conglomerate from 

0.15 to 12 m thick interbedded with shale and siltstone. 

Some of the individual conglomerate beds have a siltstone 

to sandstone matrix, whereas others have a graywacke 

matrix. 

The present study includes detailed sampling (1 ,656 

clasts) of the conglomerate and subsequent chemical, petrographic, X-ray diffraction, dimensional, and scanning 

electron microscope (SEM) analysis. Table 1 compares 

previous descriptions of the Fincastle Conglomerate lithologies with the results of the current study. 

We have not identified dolostone, dolomitic cement, 

or high-grade metamorphic clasts. Dimensional analysis 

Program and Extended Abstracts 13 
Table 1. Clast lithologies of the Fincastle Conglomerate as previously reported and found in this study 

Stow and Bierer, Butts, 1940 Kellberg and Grant, 1 Karpa, 2 This study,3 

1937 1956 (in percent) 1974 (in percent) (in percent) 

" .. .largely pebbles " ... mostly gray limestone 38.6 limestone 6.0 limestone 31.2 

of diabase" quartzite" quartzite 29.0 dolostone 2.7 quartzite and 

vein quartz 22.1 vein quartz 13.0 metasandstone 30.6 

sandstone and sandstone and vein quartz 17.2 

siltstone 5.7 siltstone 75.0 sandstone and 

chert 3.7 chert 2.0 siltstone 11.7 

other .9 chert 5.9 

other 3.4 

1 Based on > 1,000 clasts. 2 Data are an unweighted average of three separate collections. 3 Based on 1,656 clasts identified at Big Gulch and at the new excavated exposure at the Dixon Construction Co. site on U.S. 

220, 1.8 km north of Fincastle, Va. 

Butts, C., 1940, Geology of the Appalachian Valley in Virginia: Virginia Geological Survey Bulletin, pt. 1, 129 p. 

Karpa, J.B., III, 1974, The Middle Ordovician Fincastle Conglomerate north of Roanoke, Virginia and its implications 

for Blue Ridge tectonics: unpublished M.S. thesis, Virginia Polytechnic Institute and State University. 

Kellberg, J.M., and Grant, L.F., 1956, Coarse conglomerates of the Middle Ordovician in the southern Appalachian 

Valley: Geological Society of America Bulletin: v. 67, p. 697-716. 

Stow, M.H., and Bierer, J.C., 1937, The significance of an Athens Conglomerate near Fincastle, Virginia [abs.]: 

Virginia Academy of Science Proceedings, 1936-193 7, p. 71. 

indicates that the clasts are subrounded to rounded and 

range in size (long dimension) from 0.5 to 21 em (4.5 em 

average). 

Removal from the matrix has shown that all the clasts 

are coated by a thin layer of material that resembles desert 

varnish. The color of this layer ranges from yellow orange 

and tan to brown and brownish black. The clast/coating 

bond varies in strength, although most clasts retain some 

portion of the coating after removal from the matrix and 

preparation of polished sections. Examination by SEM 

(energy dispersive analysis) has been used to characterize 

the coating chemically and mineralogically. All the clasts 

have a clay coating composed of an iron-bearing potassium 

clay approximately 10 to 30m thick. Another coating layer, 

common on 50 percent of the clasts, is composed mainly of 

titanium (oxide?) with minor amounts of clay. This 

titanium-rich layer (10 to 20m thick) occurs either directly 

on the clast substrate or on the iron-bearing potassium clay 

layer. A manganese-rich layer was found on only two 

clasts. 

A model for the depositional history and provenance 

of the Fincastle Conglomerate must address the following 

constraints: (1) the conglomerate is within a margin 

sequence, (2) the clasts are subrounded to rounded, (3) the 

clasts are composed of a wide variety of lithologies including major amounts of limestone, (4) no high-grade metamorphic clasts were identified in this study, and (5) a 

coating similar to desert varnish is found on all the studied 

clasts. We propose that the conglomerate represents material from alluvial fan deposits that was rapidly transported to 

a marine environment near the source. The alluvial fan(s) 

14 Appalachian Basin Symposium 

formed in an arid or semiarid environment from an upland 

(high-energy) drainage area to the east or southeast. The 

uplands were probably associated with a stage of the 

Taconic orogeny (the Blountian phase; Rodgers, 171, 

Geological Society of America Bulletin, v. 82, p. 

1141-1178). However, the erosion was insufficient to 

produce clasts of the underlying metamorphic basement. 

The Fincastle clasts probably represent Lower Cambrian to 

Middle Ordovician source rocks. The presence of abundant 

limestone clasts and a "desert varnish" coating strongly 

suggests rapid transport from the uplands source to form 

alluvial fans in an arid or semiarid environment. Titaniumrich desert varnish has not been reported to have formed in 

current desert environments; further study is in progress to 

characterize this unusual occurrence more completely. Tectonic and (or) climatic changes could have resulted in rapid 

erosion and subsequent deposition in the proximal marine 

environment. 

Anticlines of the Copper Creek-Narrows Thrust 

Block, Southwestern Virginia 

Robert C. McDowell 

The Roanoke reentrant marks the boundary between 

the southern Appalachians and the more northerly striking 

central Appalachians. Northeast of the juncture, folds 

predominate in the foreland fold-and-thrust belt; southwest 

of Roanoke, thrust faults are more common. In the Tennessee salient of the southern Appalachians, a succession of 

southeastward-dipping homoclinal sequences are separated 
VIRGINIA rl INDEX MAP 

~ 1lTust faUt 

~ Anticlire 

~ Dome, showing cUniration 

RD, Rockdell BA, Bane 

0 10 Miles l lV, 1horTl>son Valley 

BG, EU1<es Garden 

KB, Kirrtlerling basin 

CH, aover l-lolbN 

SM, Seven Mile 

16 Kilometers 

Figure 1. Anticlines and domes of the Copper Creek-Narrows fault block. 

by imbricate thrusts. In southwestern Virginia, however, at 

the northeastern end of the southern Appalachians, thrusts 

are fewer, and several thrust sheets contain first-order folds. 

Unlike the relatively long, linear folds of the central 

Appalachians, folds in southwestern Virginia are relatively 

short, and anticlines are particularly conspicuous. Many 

folds have axial trends that are oblique to the regional trends 

of the thrusts. The most striking examples of these anticlines occur in the Copper Creek-Narrows thrust block (fig. 

1). 

The Copper Creek-Narrows thrust system extends 

from the Roanoke reentrant southwestward for about 480 

km. It has a gap of about 40 km in Tazewell County, Va., 

where the thrust shortening is transferred to an anticline 

(fig. 1). The Copper Creek-Narrows block, bounded on the 

southeast by the Saltville fault, contains a series of doubly 

plunging anticlines or domes extending southwestward 

from the Roanoke juncture for about 200 km (fig. 1). These 

domes range in length from 3 to 19 km and in structural 

relief from 300 to several thousand meters. As shown on 

figure 1 , their axial surfaces strike a few degrees more 

northerly than the bounding thrust faults, the result being in 

an en-echelon arrangement as first noted by Cooper (1944, 

p. 197). Recent mapping by McDowell (1988) has shown 

that a domal structure consistent with this pattern occurs in 

the Kimberling basin of eastern Bland County, Va. (fig. 1). 

Although this structure was first noted by Campbell ( 1896), 

more recent workers have overlooked it (Butts, 1933; 

Cooper, 1961 , pl. 21), and the Kimberling basin has been 

described as an example of "contemporaneous downwarp" 

of a "depositional syncline" containing an abnormally thick 

section of Devonian clastic rocks (Butts, 1940, p. 460; 

Cooper, 1964, p. 108-109; ThomZts, 1977, p. 1249). The 

recognition of an anticline in the Kimberling basin obviates 

the need to consider the section anomalously thick and 

removes the basis for postulating contemporaneous subsidence. 

Origin of the anticlines of the Copper Creek-Narrows 

block is problematic. Many published interpretations of the 

Bane dome show a thrust ramp under the anticline. One of 

these interpretations, based on seismic reflection data, 

suggests that a subsurface duplex of horse blocks at a ramp 

is responsible for the dome (Gresko, 1985, p. 49). It is 

unclear, however, how the ramping of a sole thrust, as 

commonly suggested, would produce a series of doubly 

plunging en-echelon anticlines. Two alternative explanations follow. The structures may have been formed during 

central Appalachian folding and modified by later southern 

Appalachian thrusting. They would, thus, represent an 

interference pattern produced by nonsynchronous and nonparallel Alleghanian deformation of the two Appalachian 

segments at the Roanoke juncture. Or, the folds may have 

formed in response to a wrench-fault component acting on 

the Copper Creek-Narrows block. 

Program and Extended Abstracts 15 
REFERENCES CITED 

Butts, C., 1933, Geologic map of the Appalachian Valley of 

Virginia with explanatory text: Virginia Geological Survey 

Bulletin 42, 56 p., 1 pl., scale 1:250,000. 

---1940, Geology of the Appalachian Valley in Virginia, pt. 

1, Geologic text and illustrations: Virginia Geological 

Survey Bulletin 52, 568 p. 

Campbell, M.R., 1896, Description of the Pocahontas quadrangle 

[Virginia-West Virginia]: U.S. Geological Survey Geologic Atlas, Folio 26, 6 p., 4 maps. 

Cooper, B.N., 1944, Geology and mineral resources ofthe Burkes 

Garden quadrangle, Virginia: Virginia Geological Survey 

Bulletin 60, 299 p. 

---1961, Grand Appalachian field excursion: Virginia Polytechnic Institute Geological Guidebook No. 1, 187 p. 

---1964, Relation of stratigraphy to structure in the southern 

Appalachians, in Lowry, W.D., ed., Tectonics of the 

southern Appalachians: Virginia Polytechnic Institute 

Department of Geological Sciences Memoir 1, p. 81-114. 

Gresko, M. J. , 1985, Analysis and interpretation of compressional 

(P-wave) and shear (S-wave) reflection seismic and geological data over the Bane dome, Giles County, Virginia: 

Blacksburg, Virginia Polytechnic Institute and State University, unpublished Ph.D. thesis, 74 p. 

McDowell, R.C., 1988, Domal structure in Devonian rocks of 

Kimberling basin, Bland County, Virginia [abs.]: American Association of Petroleum Geologists Bulletin, v. 72, 

no. 8, p. 967-968. 

Thomas, W.A., 1977, Evolution of Appalachian-Ouachita salients 

and recesses from reentrants and promontories in the 

continental margin: American Journal of Science, v. 277, 

p. 1233-1278. 

Silurian Stratigraphic Changes and Their Effect 

on the Distribution of Large Bedrock Landslides, 

Appalachian Valley and Ridge Province 

Calvin R. Wiggs and Arthur P. Schultz 

Large bedrock landslides have been recognized 

recently in the Appalachian Valley and Ridge province of 

eastern North America. Individual failures can be several 

kilometers in length and involve a hundred meters of 

stratigraphic section. Most of the landslides involve Silurian 

rocks that form the dip slopes of the major mountain ridges. 

Thickness and lithologic changes in the Silurian rocks of the 

Valley and Ridge may be important factors that control the 

size, distribution, and frequency of these large slope failures. Silurian formations that make up the landslides 

compose a three-part lithotectonic unit: an upper part of 

sandstone and quartzite (Keefer Sandstone), a middle part 

of shale, siltstone, and sandstone (Rose Hill Formation), 

and a lower part of sandstone and quartzite (Tuscarora 

Sandstone). The Keefer Sandstone and the upper part of the 

Rose Hill Formation are the main rock units in the landslides. The majority of the slope failures occur in a zone 

16 Appalachian Basin Symposium 

approximately 160 km long near Roanoke, Va., where dip 

slopes of mountain ridges exhibit the three-part lithotectonic 

unit, characterized by a thick (36-91 m) Keefer Sandstone. 

Stratigraphic changes in the Keefer Sandstone have the 

most dramatic effect on modifying the three-part lithotectonic unit. Northeast of Roanoke, in northern Virginia, 

Maryland, and Pennsylvania, the Keefer thins to 10 m or 

less. Southwest of Roanoke, in southwest Virginia and 

Tennessee, the Keefer Sandstone and, locally, the entire 

lithotectonic unit are missing because unconformities occur 

in the Silurian and Devonian stratigraphic section. In 

general, the amount of missing section increases from west 

to east and from northeast to southwest in the Valley and 

Ridge of southwest Virginia. These stratigraphic changes 

are significant because major landslides occur only where a 

thick Keefer Sandstone is present. 

While stratigraphy alone does not control the distribution of the landslides (structural dip, topographic relief, 

and landslide triggering mechanisms are also important 

factors), it has a major influence over the distribution of 

bedrock landslides in the Appalachian Valley and Ridge 

province. Recognizing the stratigraphic controls on the 

distribution of the Valley and Ridge bedrock landslides may 

prove useful in evaluating and predicting future landslides. 

Central Appalachian Transect: Geology of the 

Radford, Virginia, 1 o Quadrangle 

Mervin j. Bartholomew,1 Arthur P. Schultz, and Robert 

C. McDowell 

From southeast to northwest, the Radford, Va., 1 o 

quadrangle traverses the Piedmont, Blue Ridge, Valley and 

Ridge, and Appalachian Plateau physiographic provinces. 

These physiographic provinces contain rocks that range in 

age from Middle Proterozoic through Mesozoic and contain 

a record of the sedimentologic and structural evolution of 

this part of the central Appalachian basin. Detailed 

1 :24,000-scale mapping and structural analysis have 

resulted in a comprehensive synthesis across this part of the 

fold-and-thrust belt. 

Structural domains of the Blue Ridge thrust sheet 

include 1.1-b.y.-old Grenville basement of the Lovingston 

and Pedlar Massifs and Lower Cambrian rocks of the 

Chilhowee Group. Structural analysis indicates multiple 

folding in the Blue Ridge massifs and transposition of older 

foliations along the Rockfish Valley ductile deformation 

zone. The basement and cover rocks that were subjected to 

metamorphism and ductile deformation during the middle 

and late Paleozoic subsequently were thrust westward over 

1 Montana Bureau of Mines and Geology, Butte, MT 59701. 
Valley and Ridge sedimentary rocks during the late Paleozoic Alleghanian orogeny. 

West of the Blue Ridge fault, the Pulaski fault system 

consists of a complex series of Alleghanian thrusts that can 

be distinguished from faults to the east by a thick broken 

formation in the hanging wall of the fault, ubiquitous 

tectonic breccias, and numerous fensters and duplexes. The 

Pulaski fault system, like the Blue Ridge fault, ramps 

westward from a thrust well below the Cambrian Rome 

Formation. The Rome is the major lower level decollement 

of thrust faults west of the Pulaski fault system. Palinspastic 

reconstructions based on facies analysis combined with 

balanced cross sections have shown that minimum shortening for the complex Pulaski thrust system is about 80 

percent and that shortening for thrusts in the western part of 

the Valley and Ridge is about 15 percent. 

Large-scale folds are in the hanging walls of three 

major southeast-dipping thrust faults west of the Pulaski 

thrust system in the western part of the Valley and Ridge 

province. Decollements are located in the Cambrian Rome 

Formation, the Ordovician Martinsburg and Moccasin Formations, and the Devonian Millboro and Brallier Formations. Mesoscopic deformation (cleavage, small-scale 

intense folding, and fracturing) is concentrated in these 

lithotectonic units. The Saltville and St. Clair thrust faults 

lose displacement in large anticlines (fault propagation 

folds) near the central-southern Appalachian junction zone. 

The Narrows thrust loses displacement in an imbricate fan 

that apparently continues into the central Appalachian fold 

belt. 

The Alleghany structural front separates thrustfaulted and folded rocks of the Valley and Ridge from 

gently folded rocks of the Appalachian Plateau. The axis of 

the Glen Lynn syncline, a subthrust fold in the footwall of 

the St. Clair fault, is the structural boundary of the two 

provinces. The gentle folds of the Appalachian Plateau 

probably formed above minor blind thrusts that propagated 

westward from a Devonian-level decollement in the Valley 

and Ridge into the plateau. 

Cenozoic Epidermal Gravity Tectonics of the 

Colorado Front Range and Appalachian Valley 

and Ridge Province 

Arthur P. Schultz 

Recently recognized large epidermal gravity slides, 

some as much as 5 km long, in the Appalachian Valley and 

Ridge province are found in similar stratigraphic, structural, 

and geomorphic settings as are previously described large 

bedrock blockglides of the Colorado Front Range. In both 

settings, slope failures have occurred over periods of 

millions of years and involve many single events of up to a 

billion cubic meters of rock. Epidermal slide sheets have 

similar cross-sectional geometries and styles of internal 

deformation. This deformation consists predominantly of 

folding within the sheet and minor fracturing along the basal 

shear surface. Comparable emplacement kinematics include 

slip along bedding on the higher parts of the dip slope and 

movement across a shear plane lower on the slope. Modification of the gravity slides following emplacement consists of large-scale slumping and colluviation. In areas of 

massive slope failure, geologic elements common to both 

the Appalachians and the Front Range are dip slopes in an 

elevated terrain, a distinctive three-part lithotectonic unit of 

high anisotropy, a history of climate extremes, and possible 

paleoseismic activity. These features have been misinterpreted previously as deep-seated compressional structures 

in both the Front Range and the Valley and Ridge. Thus, 

recognizing epidermal gravity failures is critical in correctly 

deciphering both past and more recent structural evolution 

of these mountain belts. Detailed comparative studies of 

these features have led to criteria needed to recognize them 

in similar geologic settings elsewhere. 

Program and Extended Abstracts 1 7 

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"Publications of the U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche. 

Supplements for 1982, 1983, 1984, 1985, 1986, and for subsequent 

years since the last permanent catalog may be purchased by mail and 

over the counter in paperback book form. 

State catalogs, "List of U.S. Geological Survey Geologic and 

Water-Supply Reports and Maps For (State)," may be purchased by mail 

and over the counter in paperback booklet form only. 

"Price and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet form only. 

Selectedcopiesofamonthlycatalog "New Publications of the U.S. 

Geological Survey" available free of charge by mail or may be obtained 

over the counter in paperback booklet form only. Those wishing a free 

subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 

National Center, Reston, VA 22092. 

Note.--Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the 

prices charged may differ from the prices in catalogs, announcements, 

and publications. 
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