Articles 

22-172 

GEOLOGICAL SURVEY 

RESEARCH 1 963 

Short Papers in Geology 

and Hydrology 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 475-D 

Short Papers in Geology 

and Hydrology 

Articles 1 22-1 72 

GEOLOGICAL SURVEY RESEARCH 1963 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 475-D 

Scientific notes and sumntaries of investigations prepared . 

by members of the Conservation, Geologic, and Water 

Resources Divisions 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 
FOREWORD 

This collection of 51 articles is the last of the chapters of Professional Paper 4 75. The 

articles report on scientific and economic results of current work by members of the Geologic 

and Water Resources Divisions of the U.S. Geological Survey. Son1e of the papers present 

results of completed parts of continuing investigations; others announce new discoveries or 

prelin1inary results of investigations that will be discussed in greater detail in reports to be 

published in the future. Still others are scientific notes of lirnited scope, and short papers on 

techniques and instrumentation. 

Chapter A of this series presents a surnmary of investigations covering a wide range of 

work done during the 1963 fiscal year. It also includes rnaps showing the status of topographic 

rnapping, a list of publications by Survey authors, a list of cooperating agencies, addresses of 

principal offices, and a list of investigations in progress. 

THOMAS B. NOLAN, 

Director. 

m 

CONTENTS 

Page 

Forevvord---------------------------------------------------------------------------------------------------- 111 

GEOLOGIC STUDIES 

Stratigraphy and structural geology 

122. Comparison of late Paleozoic depositional history of northern Nevada and central Idaho, by R. J. Roberts and 

~- R. Thomasson----------------------------------------------------------------------------------- I>1 

123. Thrust-fault relations in the northern Coast Ranges, Calif., by R. I>. Brown, Jr_______________________________ 7 

124. Upper Pliocene marine strata on the east side of the San Joaquin Valley, Calif., by R. L. Klausing and K. E. Lohman_ 14 

125. ~iocene vertebrates of the Barstow Formation in southern California, by G. E. Lewis_________________________ 18 

126. The Thirsty Canyon Tuff of Nye and Esmeralda Counties, Nev., by I>. C. Noble, R. E. Anderson, E. B. Ekren, and 

J. T. O'Connor------------------------------------------------------------------------------------- 24 

127. St. Kevin Granite, Sawatch Range, Colo., by Ogden Tweto and R. C. Pearson________________________________ 28 

128. Reinterpretation of the late growth of the Gypsum Valley salt anticline, San ~iguel County, Colo., by F. W. Cater_ 33 

129. A Pleistocene section at Leonards Cut, Burke County, N.C., by J. C. Reed, Jr., Bruce Bryant, E. B. Leopold, and 

Louise Weiler--------------------------------------------------------------------------------------- 38 

130. Surface and subsurface stratigraphic sequence in southeastern ~ississippi, by I>. H. Eargle_____________________ 43 

Mineralogy and petrology 

131. ~agmatic differentiation in a volcanic sequence related to the Creede caldera, Colorado, by J. C. Ratte and T. A. 

Steven ___ ~----------------------------------------------------------------------------------------- 49 

132. Revised Tertiary volcanic sequence in the central San Juan ~ountains, Colo., by T. A. Steven and J. C. Ratte__ 54 

133. Valleriite and the new iron sulfide, mackinawite, by H. T. Evans, Jr., Charles ~ilton, E. C. T. Chao, Isidore Adler, 

Cynthia ~ead, Blanche Ingram, and R. A. Berner______________________________________________________ 64 

134. Eddies as indicators of local flow direction in rhyolite, by I> avid Cummings__________________________________ 70 

Geochemistry 

135. Cadmium in samples of the Pierre Shale and some equivalent stratigraphic units, Great Plains region, by H. A. 

Tourtelot, Claude Huffman, Jr., and L. F. Rader________________________________________________________ 73 

136. Analysis of geochemical prospecting data from the Rocky Range, Beaver County, Utah, by J. J. Connor and A. T. ~iesch_____________________________________________________________________________________________ 79 

137. Investigation of sampling-error effects in geochemical prospecting, by A. T. ~iesch and J. J. Connor_ _____ -_--__ 84 

138. Effect of cation exchange on the thermal behavior of heulandite and clinoptilolite, by A. 0. Shepard and H. C. 

StarkeY-------------------------------------------------------------------------------------------- 89 

139. I>etermination of the ion-exchange capacity of a zeolitic tuff, by H. C. Starkey __ ----------------------------- 93 

140. Geological and geochemical reconnaissance, southern part of the Smyrna ~ills quadrangle, Aroostook County, 

~aine, by Louis Pavlides and F. C. CanneY------------------------------------------------------------ 96 

Geochronology 

141. Age of basement rocks from the Williston basin of North I>akota and adjacent areas, by Z. E. Peterman and C. E. 

Hedge--------------------------------------------------------------------------------------------- 100 

142. Isotopic ages of glaucophane schists from the area of Cazadero, Calif., by I>. E. Lee, H. H. Thomas, R. F. Marvin, 

and R. G. Coleman---------------------------------------------------------------------------------- 105 

Geophysics 

143. Crustal structure in the vicinity of Las Vegas, Nev., from seismic and gravity observations, by J. C. Roller------ 108 

144. Hawaiian seismic events during 1962, by R. Y. Koyanagi__________________________________________________ 112 

145. Seismic investigations on Cape Cod, Mass., by R.N. Oldale and C. R. Tuttle________________________________ 118 

Economic geology 

146. Geologic setting of the Spar City district, San Juan ~ountains, Colo., by T. A. Steven ___ --------------------- 123 

147. Thorium and uranium in monazite from Spokane County, Wash., by J. W. Hosterman, W. C. Overstreet, and J. J. 

Warr, Jr------------------------------------------------------------------------------------------- 128 

148. Rich oil shale from northern Alaska, by I. L. Tailleur______________________________________________________ 131 

v 
VI CONTENTS 

Sedimentation 

Page 

149. Dissimilarity between spatial and volocity-weighted sediment concentrations, by H. P. Guy and D. B. Simons ____ D134 

150. Temporary storage of fine sediments in islands and point bars and alluvial channels of the Rio Grande, New Mexico 

and Texas, by C. F. Nordin, Jr., and J.P. Beverage_____________________________________________________ 138 

151. Fluvial sedimentation in Mammoth Cave, Ky., by C. R. Collier and R. F. Flint______________________________ 141 

152. Quaternary mudflow deposits near Santiago, Chile, by Kenneth Segerstrom, Octavio Castillo U., and Eduardo 

Falc6n M__________________________________________________________________________________________ 144 

Paleontology 

153. New occurrences of the rugose coral Rhizophyllum in North America, by W. A. Oliver_________________________ 149 

Gl'acial geology 

154. Glacial chronology of Ullsfjord, northern Norway, by G. W. Holmes and B. G. Andersen_______________________ 159 

Analytical techniques 

155. Effluent collector for gas chromatography, by D. F. Goerlitz and W. L. Lamar________________________________ 164 

156. Use of sodium-sensitive glass electrodes for solubility determinations, by A. H. Truesdell and C. L. Christ________ 167 

157. Semimicro X-ray fluorescence analysis of tektites using 50-milligram samples, by H. J. Rose, Jr., Frank Cuttitta, 

M. K. Carron, and Robena Brown____________________________________________________________________ 171 

158. Determination of total iron in hematitic iron ores by X-ray fluorescence spectrometry, by W. W. Niles__________ 174 

159. A gas jet for d-e arc spectroscopy, by A. W. Helz_________________________________________________________ 176 

HYDROLO·GIC STUDIES 

Geochemistry of water 

160. Dolomite solubility in ground water, by Ivan Barnes and William Back______________________________________ 179 

161. Effect of tree leaves on water quality in the Cacapon River, W.Va., by K. V. Slack___________________________ 181 

162. Relation of percent sodium to source and movement of ground water, National Reactor Testing Station, Idaho, 

by F. H. Olmsted ___________________________________________________________________________ - _____ - _ 186 

163. Relation of fluoride content to recharge and movement of ground water in Oasis Valley, southern Nevada, by G. T. 

1falmbergand T. E. Eakin___________________________________________________________________________ 189 

Analytical hydrology 

164. Reservoir storage on streams having log-normal distributions of annual discharge, by C. H. Hardison____________ 192 

Marine hydrology 

165. Environmental factors affecting attached macro-organisms, Patuxent River estuary, Maryland, by R. L. Cory____ 194 

Surface water 

166. Anomalous streamflow-ground-water regimen in the Mad River basin, near Springfield, Ohio, by W. P. Cross and 

A. J. Feulner ____________________________________________________________________________ -- _- _--- _- _ 198 

167. Height-frequency relations for New Jersey floods, by D. M. Thomas_________________________________________ 202 

Ground wat-er 

168. Seasonal temperature fluctuations in surficial sand near Albany, N.Y., by R. C. Heath ___________________ ------ 204 

169. Hydrogeology of the Santiago area, Chile, by W. W. Doyel, R. J. Dingman, and Octavio Castillo U_____________ 209 

170. Ground water in the Arica area, Chile, by W. W. DoyeL__________________________________________________ 213 

Hydrologic instrumentation 

171. "Lazy" thermometers and their use in measuring ground-water temperatures, by R. C. Heath__________________ 216 

172. Television apparatus for borehole exploration, by J. E. Eddy_---------------------------------------------- 219 

INDEXES 

Subjec~--------------------------------------------------------------------------------------- 221 

Author- -- _ - - - ____ - __ - _____________________________________ - - - ____ - - _ - - - - - - - - - - - -- - -- - - - - - - - - - - 223 
Article 122 

COMPARISON OF LATE PALEOZOIC DEPOSITIONAL HISTORY 

OF NORTHERN NEVADA AND CENTRAL IDAHO 

By RALPH J. ROBERTS and M. RAY THOMASSON,1 

Menlo Park, Calif., and Midland, Tex. 

Abstract.-Three major sequences of upper Paleozoic rocks 

have been mapped in northern Nevada: one deposited east of 

the Antler orogenic belt, one within the belt, and one west of 

the belt. Recognition of comparable sequences in central 

Idaho suggests similarity in depositional history of the two 

areas. 

In 1960, sections of Paleozoic rocks in the area 

between Arco, Challis, and Hailey, Idaho (fig. 122.1), 

were visited by Roberts in company with C. P. Ross 

and other geologists of the U.S. Geological Survey. 

Thomasson had previously studied sections of upper 

Paleozoic rocks in central Idaho in 1956, 1957, and 1958 

during fieldwork on his dissertation for the University 

of Wisconsin. 

The authors independently noted similarities between 

upper Paleozoic rocks and tectonics of north-central 

Nevada and those of central Idaho, which suggest that 

the two areas have related depositional histories. 

Although rock units cannot be traced from one area to 

the other because of the intervening volcanic rocks of 

the Snake River Plain, the stratigraphic succession, 

lithology, and structural histories are comparable. 

Comparison of the sequences in the two areas is shown 

in the accompanying table and on figure 122.2. 

ROCK SEQUENCES 

In north-central Nevada, three contemporaneous 

major sequences 2 have been described (Roberts and 

others, 1958) (fig. 122.2A): (1) the Eureka-Carlin 

sequence, a cmnbination of the Eureka sequenee, 

1 Shell Oil Co. 

z The term "sequence" is used here in an informal sense to denote a geographically 

discrete succession of major rock units that were deposited under related environmental conditions (Silberiing and Roberts, 1962). A single name is applied to a 

sequence in order to avoid repeating all the formation names. In the same way, 

comparable sequences in Idaho are given informal names of their own. 

CANADA 

---~-Tz' 1 

01 \ 

~I , ...... , \ 

<i ffi I "' ', e:l '\ I ( 

---\. '.J ) +. 

) . ',.J (.....1"\0¢ 

I . ',, \ ~. 

} ', ' \ ~ I ', .... \ ___,_.J~ l \ HAILEY 30'" l 

OREGON 1 Boise;.... \QUADRANGlE I 

1

/ 0 ....J ~Arco I::E; 

. t/ Hailey .. 0 I~ I (J • Ji?.: 

I t I D/ A H o ~~ , _____ j_dL---.-",.------~ I 0Q /.... (}: L ,.. • I 

I ~ /.Y 0 " EXPLANATION ~ «;'</ 0" / I 0 ~ /.0 / I -~~~--?-······· 

I ./!- .J 0 / I East boundary 

/ '((_O /-.....v Carlin° / I of orogenic belt I ~ f... I 

I 'i?' (/) / I Dashed where approxi1 :::J O,'Eureka I ma.tely located; dotted 

1 0 :J:IC ,' I where concealed; qu.e1 Reno /..., 1 r·ied where doubtful 

""' N E V /A D A 18 ', I I~ 

""'' I '-. I 

"""' I '""' ',, Las Vegasj I 

" 0 -, ', \ 

""'' ' \ 

0 100 200 MILES '~ 

FIGuRE 122.1.-Index map of report area in Nevada 

and Idaho, showing part of the Antler orogenic belt 

and the Snake River Plain (stippled pattern). 

ART. 122 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl-D6. 1964. 

Dl 
D2 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

Descriptions of late Paleozoic rocks in northern Nevada and central Idaho 

Sequence as shown in fig.l22.2 I Name, age, and thickness of formation Lithology Facies 

Northern Nevada 

Havallah Formation, Pennsyl- Up6er part: Upper part: 

vanian and Permian, 10,000+ alcareous sandstone, lime- Offshore but shoaling toward 

Havallah sequence ft stone, shale, minor con- the top. (Roberts and others, glomerate 1958; Silberling and Lower part: Lower part: Roberts, 1962) Sandstone, shale, chert Offshore. 

Pumpernickel Formation, Penn- Argillite, chert, sandstone, Eugeosynclinal, mostly offshore 

sylvanian(?), 7,000+ ft greenstone and moderately deep water. 

Edna Mountain Formation, Sandstone, shale, shaly lime- Nearshore, shallow water. 

Permian, 700+ ft stone 

Antler sequence Antler Peak Limestone, Upper Limestone, shaly and sandy Nearshore, shallow water. 

(Roberts and others, Pennsylvanian and Permian, limestone 

1958) 625ft 

Battle Formation, Middle Penn- Conglomerate, sandstone, shale, ·Terrestrial to shallow-water rna- sylvanian, 730+ ft limestone rine. 

Buckskin Mountain Formation, 

Permian, 1,200+ ft 

Sandstone, limestone Nearshore, shallow water. 

Strathearn Formation, Upper Limestone, fine conglomerate Shallow water. 

Pennsylvanian and Permian, 

Carlin 1,500+ ft 

sequence 

(AfterDott, 1955; Fails, Moleen and Tomera Formations, Limestone, fine conglomerate, Shallow water. 

1960) Lower and Middle Pennsyl- sandstone 

vanian, 3,200+ ft 

Tonka FoFmation, Lower Mis- Conglomerate, sandstone, shale, Offshore, foredeep, moderately 

sissippian to Pennsylvanian, graywacke deep water. 

2,500+ ft 

Central Idaho 

Ketchum sequence Wood River Formation, Penn- Sandstone, calcareous sandstone, Mostly offshore, moderately deep 

(Umpleby and others, sylvanian and Permian, 8,000+ limestone, chert to shallow water. 

1930; Bostwick, 1955; ft Basal conglomerate, 40-260 ft 

Thomasson 1) Milligen Formation, Mississip- Argillite, siliceous argillite, chert, Eugeosynclinal, offshore, modpian(?), 7,000+ ft limestone, quartzite erately deep water. 

Conglomerate on Summit Creek, Conglomerate, sandstone, shale Shallow water. 

Summit Creek sequence Upper Pennsylvanian, 1,910 

(Modified after ft 

Thomasson 1) 

Unnamed unit Shale Shallow water. 

Conglomerate in Muldoon area, Conglomerate, shale, sandstone, Shallow water. 

Lower Pennsylvanian, 1,324 ft limestone 

Muldoon Formation: Foredeep, offshore: 

Wildhorse Member, Upper Shale, minor conglomerate, lime- Moderately deep water. 

Mississippian or Lower stone 

Star Hope sequence Pennsylvanian, 2,586 ft 

(Modified after Thomas- Iron Mine Member, Upper Conglomerate, sandstone, silt- Do. 

son; 1 Ross, 1960; Skipp, Mississippian, 3,650 ft stone, mudstone 

1961a) Garfield Member, Upper Sandstone, siltstone, mudstone Do. 

Mississippian, 2,587 ft 

Copper Creek Member, Lower Graded graywacke, black shale Do. 

Mississippian, 861 ft 

Unnamed shale member, Siliceous argillite, minor chert, Moderately deep to deep 

Lower Mississippian, 4,000 ft sandstone, limestone water. 

t See footnote 3, p. D4. 
ROBERTS AND THOMASSON 

A. Northern Nevada, Mississippian through Early Permian. Following the Antler orogeny, sediments of the Antler 

sequence were deposited near the orogenic belt and those of the Havallah and Carlin sequence farther offshore 

B. Northern Nevada, Late Permian. During the Sonoma orogeny, the Havallah sequence moved eastward on the 

Golconda thrust, and clastic rocks were shed into eastern Nevada 

Summit Creek 

C. Central Idaho, Mississippian through Early Permian. Following the Mississippian orogeny, sediments of the 

Summit Creek sequence were deposted near the orogenic belt and those of the Ketchum and Star Hope sequences farther offshore 

D. Central Idaho, post-Early Permian. During the post-Early Permian orogeny, the Ketchum sequence moved 

eastward on the Hailey thrust 

Conglomerate 

Sandstone 

Shale or argillite 

EXPLANATION 

~ 

~ 

Shale and graywacke 

Bedded chert 

Volcanic rock 

Limestone 

Shaly limestone 

Dolomite 

D3 

FIGURE 122.2.-Diagrammatic sections showing a comparison of late Paleozoic depositional history in northern Nevada with that 

in central Idaho. 
D4 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

(composed of the Chainman Shale, Diamond Peak 

Forn1ation, Ely Lin1estone, and the Carbon Ridge and 

Garden Valley Forn1ations, exposed in the Eureka area) 

(fig. 122.1), and the Carlin sequence exposed farther 

north ( con1posed of the Tonka, Moleen and Tmnera, 

Strathearn, and Buckskin ~1ountain Formations of 

Dott, 1955, and Fails, 1960); (2) the Antler sequence, 

composed of the Battle Formation, Antler Peak Limestone, and Edna Mountain For1nation; and (3) the 

Havallah sequence, con1posed of the Pun1pernickel and 

Havallah Formations (Ferguson, Muller, and Roberts, 

1951; Silberling and Roberts, 1962). The Eureka and 

Carlin sequences were deposited east of the Antler 

orogenic belt; the Antler sequence was deposited within 

and near the belt; and the Havallah sequence was 

deposited west of the belt in a separate basin. The 

clastic rocks that predon1inate in these sequences were 

derived frmn the emergent Antler orogenic belt. 

Carlin and Star Hope Sequences 

Rocks cmnparable to the Carlin sequence have been 

described in central Idaho (Ross, 1934, 1960, 1962a; 

Skipp, 1961a, 1961b; Scholten, 1957; Thomasson, 1959a, 

1959b, Thomasson; 3 Shannon, 1961) and are here 

called the Star Hope sequence. In the Muldoon area, 

between Hailey and Mackay, the sequence is 15,340 feet 

thick (Thomasson 3) and is con1posecl of an unnamed 

shale at the base, the 11uldoon Fonnation, and an upper 

conglomerate. Correlative units have been recognized 

in the Copper Basin area, 10 n1iles west of 11ackay 

(Ross, 1960, 1962a, 1962b, 1962c; Skipp, 1961a, 1961b). 

The Carlin and Star Hope sequences are both characterized by shale and siliceous shale at the base of the 

section and by conglmnerate, graywacke, sandstone, 

shale, and lin1estone in the n1iddle and upper parts. 

In detail, the sections differ, but in general the rock 

types are similar. The conglon1erates in both sequences 

are cmnposed predon1inantly of fragments of chert and 

quartzite derived frmn eugeosynclinal rocks; these 

conglomerates coarsen westward, indicating derivation 

frmn a western source. Eastward, both sequences 

intertongue with finer elastic rocks and li1nestone of 

shelf facies. 

Antler and Summit Creek sequences 

Forn1ations of the Antler sequence, which were 

deposited within and near the orogenic belt in northern 

Nevada, are n1uch thinner and nwre lenticular than 

offshore correlative units on both sides of the belt (figs. 

122.1 and 122.2A). Locally, uplift during the late 

Paleozoic caused erosion of parts or all of the sequence. 

In eentral Idaho, cmnparable rocks thus far have been 

a Thomasson, M. R., 1959, Late Paleozoic stratigraphy and paleotectonics 

central and eastern Idaho: Wisconsin Univ., Ph. D. thesis, 244 p. 

recognized only at one place, on the ridge at the head 

of Sumn1it Creek. They are here called the Sunnnit 

Creek sequenee (figs. 122.20 and 122.3). This sequence 

consists of about 1,900 feet of conglomerate, sandstone, 

and shale of Pennsylvanian age (Thomasson 3). The 

basal unit, like the Battle Fonnation of the Antler 

sequence, rests unconformably on folded Ordovician 

rocks. 

Havallah and Ketchum sequences 

In the Hailey area the Milligen and Wood River 

Formations, together here ealled the Ketchum sequence, 

are respectively similar to the Pumpernickel and 

Havallah Forn1ations of the Havallah sequence in 

Nevada (Silberling and Roberts, 1962). The Milligen 

Forn1ation, at the base, is most.ly dark shale and chert; 

the Pumpernickel is mostly shale and radiolarian chert, 

but locally contains a good deal of volcanic rock; the 

Milligen apparently lacks volcanic rock. The Wood 

River Formation contains bedded chert, sandy limestone, and shale that are strikingly si1nilar to comparable units of the Havallah Fonnation; the Wood River 

differs in that it contains coarser clastic rocks near the 

base. 

The source of the clastic rocks in the Ketchu1n 

sequence has not yet been resolved. Thmnasson 3 

1neasured current directions in the Wood River Fonnation; north of Hailey these suggest derivation frmn the 

southwest; near Hailey, current directions suggest 

derivation frmn the northwest. No diagnostic current 

n1arks were noted in the Milligen Forn1ation. However, Roberts believes that smne detritus in the Milligen 

and Wood River Fonnations 1nust have been transported westward from the orogenic belt, as indicated in 

figure 122.2, but agrees that other sources may also 

have supplied detritus. 

Contrasts of the Ketchum with other Idaho sequences 

The sharp contrasts in lithology and stratigraphy 

between the Ketchun1, Sun1mit Creek, and Star Hope 

sequences in Idaho are due to differences in their 

depositional environ1nents. The Ketchun1 sequence 

represents 1nostly an offshore and deep-water facies in 

the lower part and shallow-water facies in the upper 

part, whereas the Su1nmit Creek represents a nearshore 

faeies that grades eastward into offshore facies of the 

Star Hope sequence. Ross (1962b, p. 385, 1962c, pl. 

1) shows a depositional contact between rocks here 

assigned to the Ketchun1 and Star Hope sequences. 

On the geologic 1nap of the Hailey quadrangle these 

roeks are shown in thrust-fault eontaet (Umpleby and 

others, 1930, pl. 1); 1noreover, the Ketchun1 sequence 

has been highly deformed (figs. 122.2, 122.3), in sharp 

contrast to the relatively simple deformation of the 

Summit Creek and Star Hope sequences. These con-
114 ° 20' 

EXPLANATION 

lliJ 

Tertiary volcanic rocks 

Cretaceous ~ (?) intrusive 

rocks 

~ . ' 

Wood River Formation 

Ccg, basal conglomerate 

[£]]] 

Milligen Formation 

1'9/:J 

Ordovician rocks 

[E) 

Algonkian rocks 

(/) 

:::::> 

0 

0::: 

I.J.J 

LL. 

z 

0 

Ill 

0::: 

<( 

u 

---- Contact 

-- Fault -- ....... 0 ••• ~ 

Thrust fault 

Teeth on upper plate 

Tv 

43 °50' 

~' 

114°10' 114°20' 

HAILEY QUADRANGLE 

Area 

shown in 

A and B 

•:Ketchum 

Hailey 

INDEX MAP 

KETCHUM 

SEQUENCE 

~ 

~ Wood River Formation 

IPwc, basal conglomera.te 

fMm] 

Milligen Formation 

0 2 4 MILES 

EXPLANATION 

[0 

Tertiary volcanic rocks 

Cretaceous ~ (?) intrusive 

rocks 

SUMMIT CREEK 

SEQUENCE 

~sfj 

Conglomerate on 

Summit Creek 

ANGULAR 

UNCONFORMITY 

IJ>.fd 

Ordovlcian rocks 

[0 

Algonkian rocks 

114°10' 

z 

STAR HOPE <( 

SEQUENCE ::E 

0::: 

~ z (/) 

zz 

~~~~ 0::: •• ' I.J.J <( I.J.J 

(IPJ;!~ o.. :i ~ 

Undifferentiated rocks}~ rF; ~ in Boulder Creek and 0::: Ill 

Muldoon areas ~ ~ (/) u (/) 

(/) 

(/) 

::;;: 

FIGuRE 122.3.-Geologic map of part of the Hailey quadrangle, Idaho, showing original and alternative interpretations. A, Original interpretation: generalized 

after Umpleby and others (1930, pl. 1). All Pennsylvanian clastic rocks are assigned to the Wood River Formation. B, Alternative interpretation: Pennsylvanian clastic rocks are differentiated and assigned to separate sequences; the Ketchum sequence is thrust over Algonkian(?) and Ordovician rocks and the 

Summit Creek sequence. Age assignments are according to Bostwick (1955) and Thomasson.3 

:::0 

0 

to 

J::!:j 

:::0 

~ 

U1 

> z 

t;j 

~ 

~ 

0 

~ 

> U1 

U1 

0 

z 

t:j 

01 
D6 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

trasts are interpreted as evidence that the Ketchum 

sequence moved into the Hailey area from the west or 

southwest on a major thrust (here na1ned the Hailey 

thrust), and is therefore allochthonous like the Havallah 

sequence in Nevada (Roberts and others, 1958, p. 

2849; Silberling and Roberts, 1962). 

CONCLUSION 

The striking similarities in major sequences of upper 

Paleozoic rocks in northern Nevada and central Idaho 

indicate similarity in depositional and orogenic history. 

Nolan and others (1956, p. 54) suggest Carboniferous 

uplift of a landmass to the west of Eureka, Nev., which 

supplied coarse detritus to the Diamond Peak Formation; Thomasson,3 Ross (1960, p. B232; 1962a), and 

Skipp (1961a, p. 387-388) also recognized that coarse 

clastic rocks in the Mackay quadrangle, Idaho, indicate 

Mississippian to Pennsylvanian orogeny to the west. 

The orogenic movements in Nevada took place along 

the Antler orogenic belt which probably extends northward into central Idaho (fig. 122.1). This belt now 

may be largely covered in Idaho by younger thrust 

plates. Remnants of the orogenic belt in the Hailey 

area show characteristic structural features and all9chthonous rock units like those of the orogenic belt in 

Nevada. 

The picture presented here is no doubt oversimplified, 

and additional fieldwork in central Idaho should be 

undertaken to test these suggestions in the field. The 

terms Milligen and Wood River should be restricted to 

the formations in their type areas and to continuations 

of these lithologic units within the Milligen-Wood River 

depositional basin. New terms should be used for 

correlative units deposited within the orogenic belt, in 

the Muldoon trough, and on the shelf east of the trough. 

REFERENCES 

Bostwick, D. A., 1955, Stratigraphy of the Wood River formation, south-central Idaho: Jour. Paleontology, v. 29, no. 6, 

p. 941-950. 

Dott, R. H., 1955, Pennsylvanian stratigraphy of Elko and 

northern Diamond Ranges, northeastern Nevada: Am. 

Assoc. Petroleum Geologists Bull., v. 39, p. 2211-2305. 

a See footnote, p. D4. 

Fails, J. G., 1960, Permian stratigraphy at Carlin Canyon, 

Nevada: Am. Assoc. Petroleum Geologists Bull., v. 44, no. 

10, p. 1692-1703. 

Ferguson, H. G., Muller, S. W., and Roberts, R. J., 1951, Geology 

of the Winnemucca quadrangle, Nevada: U.S. Geol. Survey 

Geol. Quad. Map GQ-11. 

Nolan, T. B., Merriam, C. W., and 'Villiams, J. S., 1956, The 

stratigraphic section in the vicinity of Eureka, Nevada: 

U.S. Geol. Survey Prof. Paper 276, 77 p. 

Roberts, R. J., Hotz, P. E., Gilluly, James, ano Ferguson, H. G., 

1958, Paleo?Oic rocks of north-central Nevada: Am. Assoc. 

Petroleum Geologists Bull., v. 42, no. 12, p. 2813-2857. 

Ross, C. P., 1934, Correlation and interpretation of Paleozoic 

stratigraphy in south-central Idaho: Geol. Soc. America 

Bull., v. 45, p. 937-1000. 

--- 1960, Diverse interfingering Carboniferous strata in 

the Mackay quadrangle, Idaho: in U.S. Geol. Survey Prof. 

Paper 400-B, p. B232-B233. 

--- 1962a, Upper Paleozoic rocks in central Idaho: Am. 

Assoc. Petroleum Geologists Bull., v. 46, no. 3, p. 384-387. 

--- 1962b, Stratified rocks in south-central Idaho: Idaho Bur. 

Mines and Geology Pamph. 125, 126 p. 

--- 1962c, Paleozoic seas of central Idaho: Geol. Soc. America 

Bull., v. 73, p. 769-794. 

Scholten, Robert, 1957, Paleozojc evolution of the geosynclinal 

margin north of the Snake River plain, Idaho-Montana: 

Geol. Soc. America Bull., v. ti8, no. 2, p. 151-170. 

Shannon, J. P., 1961, Upper Paleozoic stratigraphy of eastcentral Idaho: Geol. Soc. America Bull., v. 72, no. 12, p. 

1829-1836. 

Silberling, N. J., and Roberts, R. J., 1962, Pre-Tertiary rocks in 

northwestern Nevada: Geol. Soc. America Spec. Paper 72, 

58 p. 

Skipp, Betty A. L., 1961a, Interpretation of sedimentary features 

in Brazer Limestone (Mississippian) near Mackay, Custer 

County, Idaho: Am. Assoc. Petroleum Geologists Bull., v. 

45, no. 3, p. 376-389. 

--- 1961b, Stratigraphic distribution of endothyrid Foraminifera in Carboniferous rocks of the Mackay quadrangle, 

Idaho: in U.S. Geol. Survey Prof. Paper 424-C, p. C239-

C244. 

Thomasson, M. R., 1959a, Late Paleozoic stratigraphy and 

paleotectonics in central and. eastern Idaho [abs.]: Geol. Soc. 

America Bull., v. 70, no. 12, p. 1687-1688. 

--- 1959b ·Paleocurrent and sedimentary structure studies in 

upper P~leozoic rocks in central Idaho labs.]: Geol. Soc. 

America Bull., v. 70, no. 12, pt. 2, p. 1687. 

Umpleb.v, J. B., Westgate, L. G., and Ross, C. P., 1930, Geology 

and ore deposits of the Wood River region, Idaho: U.S. 

Geol. Survey Bull. 814, 150 p. 
Article 123 

THRUST-FAULT RELATIONS IN THE NORTHERN COAST RANGES, CALIFORNIA 

By ROBERT D. BROWN, JR., Menlo Park, Calif. 

Abstract.-A klippe of volcanic rock which covers about 50 

square miles in Glenn, Colusa, and Lake Counties provides evidence of a folded thrust fault that can be traced eastward into 

the Stony Creek fault zone. Rocks involved in the thrusting 

are of Late Jurassic and Cretaceous age. 

The structural relations described in this article 

involve strata in the northern Coast Ranges of California and in the foothills along the western border of 

the Sacramento Valley (fig. 123.1). The structural 

39° 

Point Arena 

38° 

0 25 

Redding 

50 75 

SACRAMENTO 

100 MILES I 

FIGURE 123.1-Index map of part of northern California, showing location of Stonyford (S) and Lodoga (L) quadrangles. 

interpretations and the map data shown in figure 123.2 

are based upon detailed mapping by the author and 

Ernest I. Rich in the Lodoga 15-minute quadrangle 

(Brown and Rich, 1961) and in the Stonyford 15-minute 

quadrangle (unpublished), which cover the area of 

figure 123.2 east of long. 122°45' W. (fig. 123.1), and 

upon reconnaissance mapping by the author in areas to 

the north, west, and south. 

STRATIGRAPHIC NOMENCLATURE 

The existing nomenclature for the rocks described is 

avoided in the discussion of structural relations. This 

is in part because the application of existing names 

would involve cun1bersome stratigraphic discussions 

that are not germane to this article, but also because 

some of the existing names involve stratigraphic and 

structural concepts that are incompatible with the field 

relations described here. The following brief discussion 

is intended to demonstrate some of the difficulties 

inherent in the use of the existing names. 

Along the foothills west of the Sacramento Valley, 

sandstone, siltstone, and conglomerate totaling more 

than 40,000 feet in thickness have been subdivided into 

formations chiefly on the basis of contained faunal 

ele1nents. Although some formational units are valid 

rock-stratigraphic units (for exa1nple, the V enado 

Forn1ation of Kirby, 1943), those with which thi8 paper 

is most concerned, the l{noxville, Paskenta, and Horsetown, are defined in age terms and the definitions differ 

slightly from author to author. Redefinition in strict 

lithologic terms is difficult because of cmnplex interfingering of lithologies and because many of the rocks 

of differing age are lithologically alike. Where lithologic distinctions are apparent and extensive, they 

generally do not coincide with boundaries based on 

geologic age, so that naming new lithologic units would 

see1n preferable to redefining existing biostratigraphic 

units. However, for a rock sequence so widespread 

and so variable in lithologic detail as that along the 

ART. 123 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D7-D13. 1964. 

D7 
D8 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

western border of the Sacranwnto Valley, new formation-name proposals should be based upon detailed 

1napping throughout several 15-minute quadrangles, 

and detailed geologie mapping of so large an area is not 

yet available. A n1ore complex proble1n is involved in 

the sheared and deformed roek sequenees thttt forn1 the 

core of the Coast Ranges. These roeks have been 

assigned by previous workers to the Franciscan Formation, the Franeisean Group, or the Franciscan Series; 

by smne the name has been used as a general term, but 

n1ost reeent workers have referred to the Franciscan 

Formation, thereby implying that the unit is a 

stratigraphie entity. 

Regardless of the rank of classification of the Franciscan, 

geologists who use the tern1 agree that it ineludes a 

diverse suite of lithologies, eharaeterized by graywacke, 

siltstone, sen1ischist, phyllonite, ehert, basic pillow 

lava, and flow breeeia that are locally altered to greenstone, 1ninor hypabyssal intrusive rocks, and glaucophane sehist; serpentine and ultra1nafie bodies are 

conunonly found in association with all these rocks. 

The thiekness and internal stratigraphy of the gross 

unit are unknown, and even estimates of thickness are 

subject to errors of several orders of magnitude because of the lack of struetural and stratigraphic detail 

in Franciscan terranes. Neither the upper nor the 

lower age limit of the Franciscan is known, but some 

of the glaucophane sehists have been radiometrieally 

dated at 130 to 1.50 inillion years ± 5 percent (Art. 142; 

and Lee and others, 1963), and fossils indieative of an 

age range fron1 Late Jurassic to L,tte Cretaceous have 

been described frmn Franciscan sedimentary rocks 

(Irwin, 1957). The Franciscan n1ust therefore range 

in age frmn Late Jurassie or older to as young as Late 

Cretaceous. The eontaet relations of the Franciscan 

with younger, older, or eontemporaneous, less deformed 

strata are generally obscured by major faults, and in 

areas where younger strata are found resting upon 

Franciscan rocks, the two are separated by major 

unconforn1ities representing long periods of geologic 

tin1e. 

In spite of the diversity in primary lithology and in 

degree of n1etamorphism, in spite of the uncertain age 

limits and little-known contaet relations, and in spite 

of the general absence of internal stratigraphie and 

structural detail within the Francisean, these rocks 

have long been considered a discrete lithologie unit. 

The concept of the Francisean as a structural entity 

is a useful one for broad regional studies, but nwst 

workers have used the tern1 in a stratigraphic sense 

(that is, Franciscan Formation) which does not seem 

to be justified by the field evidence that is now available. A further and nwre important objection t0 the 

use of the term Franciscan in loeal, detailed studies is 

that its use tends to eon1partnwntalize the geologic 

problems into two funda1nental units: the eomplex 

lithologic and structural asse1nblage of rocks referred 

to the Franciscan, and the more orderly rock sequences 

of the west border of the Sacran1ento Valley. The 

objections to this division are made obvious by the 

relations described in this paper, for in the part of 

northern California described here, the deformed roeks 

of the Coast Ranges (Franciscan) and those of the 

Sacramento Valley are inti1nately interrelated, both 

stratigraphically and structurally. Beeause of these 

interrelations, a twofold classification into Franciscan 

and Sacramento Valley rocks yields an oversimplified 

basic premise with which it is extremely diffieult to 

reconeile the observed field relations. 

SUMMARY OF STRUCTURAL RELATIONS 

Evidence of major thrusting is found throughout a 

large part of the Stonyford quadrangle of the northern 

Coast Ranges. The complexly folded and crushed 

terrane involved in the thrusting is separated frmn the 

simple structures and uniforn1 stratigraphy of the western border of the Saera1nento Valley by the Stony 

Creek fault zone, a n1ajor north-trending tectonic. 

feature that extends for more than 80 miles and is 

invaded by serpentinized peridotite along much of its 

length. 

East of the Stony Creek fault zone, siltstone, sandstone, and conglon1erate are more than 40,000 feet 

thick and range in age frmn Late ,Jurassic (Tithonian) 

to Late Cretaceous (Campanian). These rocks form 

a north-trending outcrop belt as much as 1.5 miles wide, 

which extends along the entire western border of the 

Sacramento Valley. Within this belt the major struetures trend northward, and although folding and 

faulting loeally reverse the dip and repeat parts of the 

seetion, an eastward dip predominates and the oldest 

rocks crop out to the west along the Stony Creek fault 

zone. 

West of the Stony Creek fault zone, a more varied 

suite of rocks underlies the Coast Ranges. These 

consist in part of sandstone and siltstone that are 

indistinguishable fron1 part of the rocks along the 

western border of the Saeramento Valley, but nwst of 

the sedimentary rock has been cataelastieally nletamorphosed to phyllonite or to cataclastie sandstone or 

sen1ichist. The cataelastically defonned roeks 1nay in 

places be partly reerystallized, but this is not generally 

apparent in the field; their most 'obvious lithologic 

eharacteristic is the crushing and shearing of n1ineral 

grains and bedding features along shear planes that 

parallel the bedding. Both the unmetamorphosed sedimentary rocks and their cataclastic counterparts contain one or 1nore thin flows of basaltic pillow lava which 
BROWN D9 

grades locally to flow breccia and in places is overlain 

by manganiferous chert. Fossils of Early Cretaceous 

(Valanginian) age are found a few hundred feet stratigraphically below the basalt, and fossils of Late 

Jurassic (Tithonian) age are found a little lower in the 

section. 

A much thicker sequence of 'ulcanic rock crops out 

on the summit and slopes of St. John Mountain and 

Snow "\'fountain and in the area between them (fig. 

123.2). These rocks consist of pillow lava and flow 

breccia with interbeds of chert and volcanic-rich 

sedimentary rock and sills of diabase. Because tl1ey 

form a mountainous area of rugged topography with as 

much as 5,000 feet of local relief, they can be studied in 

three dimensions. Detailed (1 :48,000) geologic 

mapping has disclosed that they form a klippe which 

rests in different places upon: (1) a friction carpet of 

chaotically sheared sedimentary debris; (2) bodies of 

serpentinized peridotite, sill-like in form and emplaced 

along a basal thrust plane; or (3) phyllonite and 

cataclastic sandstone, derived by bedding-plane shearing from siltstone and sandstone. Similar thrust sheets 

of sedimentary rock or phyllonite can also be recognized 

but are less obvious than the klippe of volcanic rock. 

EVIDENCE OF THRUSTING 

The Yolcanic klippe on Snow Mountain and St. John 

}.fountain consists of several thousand feet of basaltic 

lava, breccia, and tuffaceous sedimentary rock that are 

folded along west-trending axes. Except near the basal 

fault plane, primary textures and structures in the 

volcanic rocks are well preserved, the rocks are little 

altered, and they contrast sharply with the altered and 

intensely sheared phyllonitic sedimentary rocks that 

crop out elsewhere in the area west of the Stony Creek 

fault zone. Both the structural trends and mapped 

lithologic units within the klippe are truncated at a 

folded thrust fault that underlies the volcanic rocks and 

separates them from intensely deformed sedimentary 

rocks below. Additional evidence for the thrust fault 

is found in the relationship of the volcanic rocks to 

intensely she!tred chaotic sedimentary rocks northwest, 

north, and northeast of St. John Mountain. 

From Upper Nye Camp eastward, the fault surface 

at the base of the volcanic sequence traces a sinuous 

course along the northern face of St. John Mountain 

(fig. 123 .3), decreasing in altitude from about 5,200 

feet at Upper ~ye Camp to about 2,000 feet at the 

eastern boundary of the klippe. Below the projection 

of this surface, a broad relati,·ely low ttrea that extends 

north and northeast for se,·eral miles is underlain by 

crushed and sheared siltstone and sandstone, so thoroughly fault ed and mixed lhal they resemble shear-zone 

debris. These intricately faulted and folded rocks are 

cut by syntectonic quartz vems, and they contain 

scattered masses of resistant rock (fig. 123.3), a few 

feet to several hundred feet in diameter; many of the 

resistant masses show rounded altered borders and 

internal deformation features that suggest transport 

in a zone of tectonic movement. The resislanL rock 

masses are predominantly volcanic rocks or chert and, 

except for the alteration and tectonic borders, they 

resemble rocks found on St. John Mountain and Snow 

Mountftin; some of the masses, however, are of conglomerate, hard sandstone, or glaucophane schist. 

Although many of the resistant masses have clearly 

rotated or slumped downhill for short distances, others 

are clearly unaffected by landsliding and exhibit tightly 

sealed sinuous contacts with the enclosing crushed and 

sheared sedimentary rocks (figs. 123.4 and 123.5). In 

a few places, syntectonic quartz veins can be seen 

crossing the contacts between lhe country rock and the 

resistant masses. 

Most of the large resistant masses of volcanic rock 

and chert are found in topographically high positions 

within a few tens of feet beneath the projection of the 

fault surface that forms the base of the volcanic 

sequence on St. John Mountain. A few of these are 

so large and so near the projection of the thrust surface 

that they may actually be small klippen, but most 

appear to be tectonic inclusions that have been ripped 

from the upper plate and incorporated into the shear 

zone immediately below. True klippen probably are 

represented by several basalt outliers north and northeast of Upper Nye Camp, for some of these lie at or 

abo\·e the projected thrust surface, and in a few places 

thin zones of serpentine crop out at the base of the 

outliers. A larger klippe forms the upper part of 

Elephant Hill, where bedded chert, volcanic-rich 

sedimentary rock, and minor basalt with a relatively 

uniform strike and dip crop out. These rocks overlie 

chaotically deformed sedimentary rocks that crop out 

at lower elevations around the base of the hill, and the 

base of the chert-sediment-basalt sequence is marked, 

on the southwest side of Elephant Hill, by saline 

springs, abundant landslides, and in at least one place 

by lenses of serpentine. 

Tl10 chaotically deformed sedimentary rocks, together 

with the masses of chert, volcanic rock, and other 

resistant rock types, are interpreted as a flat-lying or 

gently east-dipping friction carpet, interposed between 

massiYc competent volcanic rocks above and less competent cataclastic sedimentary rocks below. The 

friction-carpet rocks superficially resemble landslide 

debris, and because they are weakly resistant to erosion 

and are lithologically and structurally heterogeneous 

they are subject to landslides. A few characteristics 
DlO 

A 

KJp 

5 

Rocks below (west of) 

Stony Creek fault zone 

Phyllonite and semischist with 

minor basaltic volcanic rocks 

~ Phyllonite and semischist 

STRATIGRAPHY AND STRUCTURAL GEOLOGY 

CREEK FAULT ZONE 

0 5 

EXPLANATION 

Rocks above (east of) 

Stony Creek fault zone 

t;~ [0 

~ ~ { Sandstone, siltstone, and 

Q conglomerate 

bKfOI 

Siltstone and sandstone 

~Jb 

Js, Tuffaceous siltstone 

Jb, Basaltic sandstone 

I Jv I 

Basaltic volcanic rocks with chert 

and minor sedimentary rocks 

lfl 

:J 

0 

w 

u 

<( 

f--

w 

0:: 

u 

10 

Rocks emplaced or formed 

along Stony Creek fault zone 

or along related fault zone 

Peridotite and serpentine 

c-!£.-j 

Friction-carpet debris 

o:LJ 

~ 

Sedimentary and volcanic 

rocks 

Occurs in tectonic lenses along 

peridotite -invaded parts of 

Stony Creek fault zone 

A' 

15 MI LES 

----- Contact 

Dashed where concealed 

+Syncline ---

0 

Fault 

D, downthrown side 

~· .... Thrust fault 

Mappedfault traces show 

location of eastern or upper limit of fault zones 

·FIGURE 123.2.- Generalized geologic map and structure section showing thrust-fault relations near Stonyford, Calif. For simplicity, 

landslides, alluvium, and terrace deposits are not showu. 
BROWN Dll 

FIGURE 123.3- North face of St. John Mountain, showing 

approximate trace of thrust, with volcanic rocks above the 

fault trace and friction carpet below. Resistant mass in 

foreground is altered diabase. Ridge on right skyline, underlain by friction carpet, is drainage divide between coastal 

(Eel River) drainage and interior (Stony Creek-Sacramento 

River) drainage. 

of the friction carpet that help distinguish it from landslides are: 

1. Abundance of resistant masses of exotic lithology, 

for which no local source is available (that is, 

intensely altered volcanic rock, glaucophane schist, 

conglomerate, and sandstone masses of distinctive 

lithology). 

2. Intense sublaminar shearing and quartz veining in 

sedimentary rock that encloses the resistant masses 

(fig. 123.5). 

3. Map distribution independent of topography: 

friction-carpet rock several hundred feet thick is 

found on major drainage divides where no higher 

slopes are available to supply landslide debris 

(fig. 123.2). 

4. Map distribution indicative of a widespread tabular 

unit. 

In the area north and northeast of St. John Mountain, 

no clearly defined lower plate can be mapped, and in 

some parts of this area the friction carpet appears 

to be as much as 800 feet thick. In other areas, however, it is thinner and can be seen to grade down 

into relatively undeformed sedimentary rocks of the 

lower plate. Accurate thickness estimates of the 

blanket are difficult to make because these rocks are 

relatively weak and slump into topographic lows, 

because the lower contact is gradational, and because 

716-626 0----64--2 

FIGURE 123.4-Resistant mass of altered volcanic rock (light 

gray) in North Fork of Stony Creek. Mass is about 50 feet 

by 30 feet across and is completely .:mclosed in chaotically 

sheared sedimentary rock (dark gray). Sealed contacts, 

shearing, and quartz veining of both rock types suggest a 

tectonic origin. 

FIGURE 123.5- Detail of shearing and contact relations of re- sistant volcanic mass (light gray) shown in figure 123.4. 

Width of photographed area about 5 feet. 

through-going faults or folds are unrecognizable within 

the terrane underlain by friction carpet. Nevertheless, 

the thickness estimate of 800 feet in the area north and 

northeast of St. John Mountain appears to be valid, 

for stream bottoms 800 feet beneath the projected 

surface of the thrust fault are underlain by chaotically 
D12 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

sheared, quartz-veined, sedimentary rock containing 

resistant masses with healed borders and crosscutting 

quartz veins. This abnormal thickness of frictioncarpet debris may be related to a broad southeasttrending anticlinal flexure of the thrust surface. This 

flexure is reflected both in the mapped distribution of 

Lhe thrust planes and in the plunging nose of serpentinized peridotite northwest of Stonyford. If the flexure 

predated or accompanied thrusting, the lower confining 

pressure along its crest would account for the abnormal 

thickness of friction carpet there. 

Thrust relations are more difficult to recognize on the 

eastern and southern sides of Lhe St. John Mountain-Snow 

Mountain klippe because on those sides the fricLion 

carpet is relatively thin and it, as well as other details 

along the base of the klippe, is obscured by landslide 

debris. Nevertheless, the tectonic nature of the basal 

surface of the volcanic sequence is still apparent, for 

where it can be examined the surface truncates structures and lithologies in the overlying rocks and is 

marked by intense shearing, saline springs, and sill-like 

bodies of serpentinized peridotite emplaced along the 

thrust zone. 

The western boundary of the klippe, also much 

obscured by landslides, has not yet been mapped in 

detail, but reconnaissance west of Snow Mountain 

has shown that the thrust surface dips gently westward for about 6 miles a11d extends nearly to the Eel 

River. The base of the klippe at its western boundary 

has a northward component of dip of about 200 feet 

per mile and is found at altitudes ranging from about 

3,250 feet on the south to about 2,500 feet on the north. 

Along the base, numerous landslides issue from a shear 

zone containing lenses of serpentine and finely comminuted serpentine debris. Bold exposures of volcanic 

rock are found immediately above the shear zone, 

and cataclastically deformed sedimentary rocks crop 

out below. The Snow Mountain- St. John .\fountain 

klippe therefore extends from the Korth Fork of Stony 

Creek nearly to the Eel River and covers an area of 

about 50 square miles. The basal thrust plane is 

gently arched along a north-trending axis that passes 

approximately through Snow ?\1ountain, and the thrust 

surface exhibits about 4,000 feet of structural relief. 

RELATIONS OF THRUST FAU'LTING TO STONY CREEK 

FAULT ZONE 

Although the Yolcanic klippe is the most obvious, 

seYcral other thrusL sheets, im-oh·ing chiefly sedimentary and cataclastically deformed sedimentary rocks, 

haYe also been mapped. These are less apparent because Lhc rocks of both the upper and lower plates are 

lithologically similar, and they can be mapped best 

where friction-carpet debris or peridotite bodies can be 

traced along the fault zone. 'T'he amount and direction 

of dip of the mapped thrust surfaces varies locally, but 

all have an average inclination of a few degrees toward 

the east, and all appear to converge eastward and to 

join the Stony Creek fault zone. Detailed relations at 

the lines of juncture with the Stony Creek fault zone 

are difficult to interpret because this fault zone, like 

many of the thrust faults in the area, is invaded by 

peridotite and serpentinized peridotite. In most places 

the fault zone is vertical and trends northward, parallel 

to the bedding in the sedimentary rocks to the cast, 

but ncar Stonyford the fault zone and the peridotite 

bodies along it swing sharply westward to outline an 

east-plunging structural basin. The stratigraphic and 

structural relations of the rocks within this basin and 

those to the west of it afford a key to the relation between the Stony Creek fault zone and the tectonic surface beneath Snow Mountain and St. John .\fountain. 

\Y est of Stonyford and east of the Stony Creek fault 

zone, an eastward-dipping volcanic sequence, identical 

with that on Snow Mountain and St. John Mountain, 

crops out. The upper contact of these volcanic rocks is 

concealed by t~1luvium and terrace deposits, but their 

mapped distribution, their structural attitude, and 

lithologic similarities of parts of this sequence to parts 

of the Late Jurassic sedimentary rock sequence to the 

east indicate that the volcanic rocks conformably underlie the sedimentary rocks, and locally are probably interbedded with them. On this basis, the Stonyford volcanic rocks are tentatively assigned a Late Jurassic age 

and are considered a part of the predominantly sedimentary rock sequence that underlies the western 

border of the Sacramento Valley. 

The volcanic sequence near Stonyford and that forming the ldippe farther west are lithologically alike; both 

are floored by major fault surfaces, and where the two 

volcanic sequences are in closest proximity, serpentinized peridotite is emplaced along the fault boundaries 

of each. Mapping of the serpentinized peridotite shows 

that these thin sill-like bodies were originally a single 

continuous sheet that has either been folded along 

north-trending axes into a syncline and anticline or was 

emplaced along a pre-existing undulttting shear surface. 

Erosion along the "anticlinal" axis has destroyed much 

of the original continuity, but in at least one place this 

continuity is preserved, and even where it is missing 

the map data are adequate to reconstruct it. The continuity of the serpcnt~ne together with the other stratigraphic and structural relations demonstrates that the 

thrust fault beneath Snow ~ountain and St. John 

~!fountain is at least a branch of the Stony Creek fault 

zone, and that it may be the structurally highest branch 

of that zone. 
BROWN D13 

SUMMARY 

The described relations show that the Stony Creek 

fault zone is a bedding-plane thrust, near vertical for 

n1ost of its mapped trace but flattening and branchino· ' b 

1nto a complex set of thrust surfaces toward the west. 

In the Stonyford quadrangle, thrusting seems to be 

localized along the contact between a competent sequence of volcanic rocks and a thick overlying sequence 

of clastic sedimentary rock; locally, however, the volcanic rocks may be found in the upper plate, as they 

are in the two areas west of Stonyford. The rocks below, or west of, this thrust zone are predmninantly 

cataclastically metan1orphosed; those above, or east of 

the thrust are little deformed. Aside fron1 the superimposed effects of cataelastic deforn1ation the sedinlentary rocks on opposite sides of the Stony Creek fault 

zone exhibit no marked differences in eit,her lithology 

or age, but conglmnerate, relatively comn1on in the 

Upper Jurassic and Lower Cretaceous rocks of the 

upper plate, is rarely found below the thrust. Volcanic 

rocks are thickest and 1nost widespread east of, or 

above, the Stony Creek fault zone, but at least one 

basalt flow of Early Cretaceous age is found in rocks 

west of, or below, the fault zone. 

Field evidence is still inadequate to establish the 

mechanism of thrusting or to prove either its a1nount or 

direction, but drag folds in1mediately above some of 

the thrust surfaces suggest that the upper-plate rocks 

have n1oved northward. This direction of 1novement 

agrees with the westerly trend of fold axes and faults 

in the Snow Mountain-St. John Mountain klippe, but 

additional data are needed before the history of thrust 

n1oven1ent can be reconstructed. 

REFERENCES 

Brown, R. D., Jr., and Rich, E. I., 1961, Geologic map of the 

Lodoga quandrangle, Glenn and Colusa Counties, California: U.S. Geol. Survey Oil and Gas Inv. Map OM-210. 

Irwin, W. P., 1957, Franciscan group in Coast Ranges and its 

equivalents in Sacramento Valley, California: Am. Assoc. 

Petroleum Geologists Bull., v. 41, no. 10, p. 2284-2297. 

Kirby, J. M., 1943, Upper Cretaceous stratigraphy of the west 

side of the Sacramento Valley south of Willows, California: 

Am. Assoc. Petroleum Geologists Bull., v. 27, no. 3, p. 

279-305. 

Lee, D. E., Thomas, H. H., Marvjn, R. F., and Coleman, R. G., 

1963, Isotope ages of glaucophane schists from Cazadero, 

California [abs.]: Geol. Soc. America 59th Ann. Mtg. Cordilleran Sec., Berkeley, Caiif., 1963, preprint, p. 42-43. 
Article 1 r24 

UPPER PLIOCENE MARINE STRATA ON THE EAST SIDE 

OF THE SAN JOAQUIN VALLEY, CALIFORNIA 

By R. L. KLAUSING and K. E. LOHMAN, 

Sacramento, Calif., and Washington, D.C. 

Work done in cooperation with the California Department of Water Resources 

Abstract.-Recent drilling on the east side of the San Joaquin 

Valley in Tulare County has revealed marine Pliocene strata 

that are about 1,050 feet thick and contain diatomb. The diatom 

assemblage indicates a late Pliocene age and suggests a correlation 

with part of the San Joaquin Formation exposed on the west 

side of the valley. 

The rocks of Pliocene age occurring in the subsurface 

along the southeast side of the San Joaquia Valley 

have generally been assigned to the Etchegoin and 

Chanac Formations of Pliocene age ("reaver and others, 

1944, and Sperber, 1952). Evidence reported in this 

article indicates that at Richgrove, just north of the 

Tulare-l{ern County line 8 miles east of Delano (fig. 

124.1), the entire marine Pliocene sequence should be 

assigned to the upper Pliocene and may be the equivalent of a part of the San Joaquin Formation which is 

exposed on the west side of the valley. 

In 1959 a core hole was drilled to a depth of 2,200 

feet at Richgrove to obtain information on the lithology 

and the physical and engineering properties of the 

sediments in the depth penetrated by water wells. 

This core hole, 24/26-36A2, is in the NEXNE~~ sec. 36, 

T. 24 S., R. 26 E., Mt. Diablo base line and meridian. 

As shown by the composite logs (fig. 124.2), the core 

hole penetrated unconsolidated continental deposits 

from the Sierra Nevada to a depth of 7 44 feet, a thick 

section of siltstone and claystone 1 containing a few 

sand interbeds from 744 to 1,900 feet and underlain by 

300 feet of sand from 1,900 to 2,200 feet. 

Thirty core samples spanning the depth interval 

frorn 754 to 2,101 feet were examined by Lohrnan, who 

1 Claystone as logged from core inspection at well, but particle-size analyses indicate 

mostly siltstone. 

identified an assemblage of marine diatoms in the 

interval between 1,141 and 1,641 feet (see accompanying table). . 

Most of the diatoms listed in the table have a wrde 

stratigraphic range, occurring throughout the Pliocene 

and some even into the Miocene. However, two 

short-ranging species, Hemidiscus ovalis and Rhaphoneis 

fatula (Lohman, 1938, pl. 22), have not been reported 

from strata older than late Pliocene. Furthermore, 

51 percent of the Richgrove species also occurs in ~he 

San Joaquin Formation ia the Kettleman Hrlls. 

Therefore, Lohman concludes that the diatom assemblage in the Richgrove cores indicates a late Pliocene 

age for the interval from 1,141 to-1,641 feet and that 

it may be the equivalent of the late Pliocene San 

Joaquin Formation of the Kettleman Hills area. 

The core interval between 744 feet and 1,141 feet, 

though unfossiliferous except for a few uniden~ifiable 

fragments of marine diatoms at 1,003 feet, IS ~ne 

gnained and lithologically simil.ar to. the ~nd~rl:ying 

diaton1aceous zone. On the basis of lithologic similarity, this upper unit is also tentatively assigned to the 

upper Pliocene. . 

A few marine invertebrate fossils were observed In 

the section between 1,641 and 1,900 feet. E. J. Moore 

(written communication, Nov. 10, 1960) identified 2 

marine pelecypod genera, Macoma sp. and Cryptomya 

sp., in the interval between 1,733 and 1,767 feet. N.o 

definite age determination could be made. T.his 

n1arine section is lithologically similar to the overlymg 

diatomaceous unit and is tentatively assigned to the 

Pliocene(?) in this article. . 

The sand below 1,900 feet is correlated with the 

Santa Margarita Formation of Diepenbrock (1933), 

ART.l24 IN U.S. GEOL. SURVEY PROF. PAPER. 475-D, PAGES D14-Dl7. 1964. 

D14 
WEST 

1000' 

2000' 

3000' 

4000' 

--=--=-;z--_:..:: =--=- Corcoran Clay 

Member of Tulare 

Formation 

......... . . . 

...... --, 0::: 00 '<t N cY') I I ('\") ('\") 

N N 

'- ' """ N '<t N 

I 

''· .... , 

0 

10 

I 

'<t 

N 

' L{) 

N 

I 

..._Area of '\ 

report - _s 

KLAUSING AND LO~AN 

z 

00 

N 

I 

'<t 

N 

' 

""" N 

I 

Continental deposits from 

the Sierra Nevada 

N 

...J 

Upper Pliocene and Pliocene(?) 

marine strata 

0 2 3 4 5 6 MILES 

0 

'<t 

I 

r--. 

N 

~EAST 

N 

basement 

complex 

I 

D15 

FIGuRE 124.1.-Geologic section along north line of Kern County through the Richgrove core hole. *Santa Margarita Formation 

of Diepenbrock (1933). 
D16 

fw 

w 

LL 

z 

:i 

fc... 

w 

0 

STRATIGRAPHY AND STRUCTURAL GEOLOGY 

(millivolts) (ohms m 2 /m) log 

Depth 

(feet) 

Generalized lithologic description 

(from core descriptions and electric logs) 

Sp;;t~an~~:lusJ Resistivity~ Graphic 

10 

o~----~~+.--F0--~20~-4~0~---.--~~--------+-------------------------------------------------------------~ ~~T 

c-- ' 

~ ~ ) ~ 600 r---~;~~--+~1:-~-----1 

~ [_L 

800~----~--H-------~ ~I~ 

I~ ~----~--h~~---------

~ c:: 1000 1-------~IE--+~...-------

~ 

1200 

!'IJ 

"'0 

!'IJ 

> f.-- Q) 

z 

e f-:-•-:-

Gi 

(Jj 

Q) :5 ~ ~ 

-

E-::::::-::-_ 

0-230 

230-412 

412-429 

429-535 

535-620 

620-637 

637-744 

744-779 

779-841 

~ ~=-;-:=~ 841-1,176 

en 

Q) 

c 

·;: 

!'IJ 

E -:::~-­

Q) 

c 

Q) 

0 

.Q 

1,176-1,206 

0::: ==;_-=~ 1,206-1,369 

Qj 

a. 

Sand, clean to silty, yellowish-brown: silt and sandy silt interbeds: several 

gravelly layers. 

Sand, silty and clayey, fine to coarse, yellowish-brown; calcareous toward 

bottom,carbonaceous matenal. 

Sand, clean to silty, medium, loose, dark-yellowish-brown. 

Silt, sandy, fine to coarse, moderate-yellowish-brown: some gravel, calcareous 

zones. 

Sand, silty and clayey, fine to coarse, yellowish-brown to olive-gray. 

Clay and silt, sandy, firm to lithified, brownish- to olive-gray. 

Sand, silty, greenish- to bluish-gray; thin interbeds of silt, clay, and claystone; 

some cementation. 

Claystone, siltstone, and silty sand, calcareous streaks, dark-bluish to 

greenish-gray. 

Claystone and clay, silty, with sandy layers, greenish-gray. 

Claystone, silty to sandy, dark-greenish- to blu1sh-gray: th1n Interbeds of clay, 

silt, and loose sand, plant remains: rhyolitic ash zone at 1,058 tt. 

Sand, silty, clayey, fine to medium, dark-greenish- to bluish-gray. 

Claystone, silty, sandy, dark-greenish- to bluish-gray: thin Interbeds of silt, 

sand, and fine gravel, diatomaceous, plant rema1ns. 

1400 f-----+---H~~------1 

~\ 

g ~~-~1~,3~6~9~-~1~,3~8~4~~S~a~n~d~·~s~il~ty~·~c~la~y~e~y~·~fi~n~e~t~o~m~e~d~iu~m~·~b~l~u~is~h~-~gr~a~y~·-------------------------4 

:_=-_-_-=_ 1,384-1,500 

1600 --------~---+f'-~-----1 

lr --ro'~-~= 1,500-1,745 - +"' -_-_-_-

Claystone and sand interbedded, firm to loose, dark-bluish- to greenish-gray; 

10-tt sand layer at base, diatomaceous. 

Claystone, silty, sandy, bluish- to greenish-gray; Interbeds of silt, sand, and 

fine gravel, more sand toward bottom, carbonaceous material, mollusk 

shells, crab remains, diatomaceous above 1,641 tt. 

~----~~~>L_ ____ ~ l ~ ~~ ~ 0 .s ~~~--------~------------------------------------------------------------~ ~ = >- - -~ Sand, silty, clayey, bluish-gray: claystone interbeds, mollusk shells and fish 

1~~ -1~~~ ~~oc~~~~~~~~~~---I_.7_4_5_-_1_.8_I_8+-C--~-y-s-~-n-e-.-s-a_n_d_y-,s-i-~-y-,b-l-u-is-h---g-~-y-;-:-:-n-:-i~-:-~-r_b_e_d_s.-m--o-11-u-sk __ S_h_e-ll-s.-f-is_h_s_c_a_IR-~~ 1/~ d -=~- 1,818-1,900 1il ~ !=::"-_-.::::.- and teeth, carbonaceous material. 

f---------4~~-----~ Em~.-=-=-1-------~-------------------------------------------------

~ ~~ ~ ~; 

2000 f-------~._._-D- -~ e -- - ~ ~~~,-~ :0~ ~Q) 

~-}--- __ ___._;__~-~ 

- 1.900-2,200 Sand, slightly clayey, some gravel, fine to coarse, greenish-gray; carbonaceous 

material, shell fragments. 

1 ~ £:: j~ 2200L-----~-J-L------~~-J~~L-------~-------------------------------------------------------------

FIGuRE 124.2.-Composite logs of test hole 24/26-36A2, Richgrove, Calif. 
KLAUSING AND LOHMAN D17 

Diatoms from U.S. Geological Survey core hole 21,./26-36A2 

[C, common; F, frequent; R, rare; *,fresh and brackish-water adventitious form~ Identifications by K. E. Lohman] ~. 

Diatoms 

Depth (feet) !=I >=I >=I 

·g~ ~:§ ·~ ~ 

g~ ~s ...... 00 00 "" "''"' ;::: ~I~ 0 "" ...... ;"?.; $ ..... 0 ..c::o C'l <:<:> 

"""' """' "" "" §~'« Of;<., .-.· ..... ~-- ..... ..... ..... ..... rn ~ -----------·---------------- Actinocyclus octonarius Ehrenberg ____ R F F F F F F X X Actinoptychus mawlatus Grove and ---- Sturt_ __ --------------------------- ____ F R ___________________________ _ senarius Ehrenberg_______________ F C F ____ F ____ F R X X 

Aul~~odiic~~8"P~obabiiiisch;nici-t~~==== ==== -R- ---- ---- R ---- ---- ---- ---- ---- Biddulphia aurita (Lyngbye) Brebis- ---- ---- ---- ---- ---- ---- ---- ----

c~f!~~~P~~~~~===================== ==== ~ =--- -R- ---- ---- ---- ---- X ---- Coscinodisws asteropmphalus Ehren- --- ---- ---- ---- ---- ---- ----

l~:!~S]~~~,;~--~m~-~ -~- :~: =m -=~- -~= ~~=- :~- -~~~ J ~ obscurus Schmidt__-------------- ____ R _______________________________ _ 

ocnlus-iridis Ehrenberg___________ F F ____ ____ F ____ R ____ X X 

Coscinodiscus t•etustissimus Pan- tocsek______________________________ ____ F ____________________________ X 

spp. (fragments) _________________ F C F F C C F R _______ _ 

Diploneis oz•alis var. o/ilongella 

c~~~ftn ?ier~b:sson)_c_Ie~e*-~====== ==== ==== -R- ==== -~- =--- ---- ---- · --- ---- Endictya robusta (Greville) Hanna --- ---- ---- ---- ----

F~a~~a~J:~~========================= _: __ ~ ==== ==== ==== _ ~- ---- ---- X ---- Frickea lewisiana (Grevillc)* Heiden _____ R ____ _ _ _ - ---- ---- ---- ---- Frustulia interposita (Lewis) DeToni* ________ R R -=== ---- ---- ---- ---- ---- Hemidiscus ovalis Lohman F ---- ---- ---- -:x- ---- Lzthod.esmium undulatum :Eilrenbe.rg= ==== R :::: :::: ==== :::: :::: ==== _: __ :::: Afeloszra recedens Schmidt ________________ C F F ________ F ____ X ___ _ sulcata (Ehrenberg) Kutzing_____ ____ C F ____ F F F C X X 

Nav~~~~rft~~~·a61e~~~~i-~~--========== ==== -R- ==== -~- ==== ==== ==== ==== -~- ==== 

N~~~~f~~e!~~~~~~~~~~~~~~~I~~~~~~~~ ~~~~ -~- -~- ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ ~~~~ -~- gramtlata Grunow ____________________ C F F F ____ F ____ X X 

:ilf.f!~~~f~~:.:~.~= ~;; :!: :~: :1; :~: i~: ~~: ~~~~ :~: :!: 

Trachyneis aspera (Ehrenberg) Cleve_ ____ ____ ____ ____ ____ _ __ R -

Xanthiopy:ris ovalis Lohman ______________________________ -=-- R -R- -X- -Xof Miocene age, on the basis of electric-log correlations 

north fr01n the Mt. Poso oil field (Park and Weddle, 

1959, pl. II). 

In the Richgrove core hole the marine diatomaceoussiltstone unit is differentiated from the overlying 

continental deposits by a marked change in lithology. 

This lithologic change, which is clearly shown on the 

electric log for the core hole (fig. 124.2), can be recognized on electric logs as far west as well 24/26-31L2 

(fig. 124.1). Westward from this point the top of the 

upper Pliocene is tentatively correlated with the upper 

Mya zone (Woodring and others, 1940, p. 28), which 

has been identified in numerous oil test wells. 

REFERENCES 

Diepenbrock, A., 1933, Mount Pozo oil field: Calif. Dept. Nat. 

Resources, Div. Oil and Gas, Summary of Operations, California Oil Fields, v. 19, no. 2, p. 12-29. 

Lohman, K. E., 1938, Pliocene diatoms from the Kettleman Hills, 

California: U.S. Geol. Survey Prof. Paper 189-C, 22 p., 

4 pls. 

Park, W. H., and Weddle, J. R., 1959, Correlation study of southern San Joaquin Valley: Calif. Dept. Nat. Resources, Div. 

Oil and Gas, Summary of Operations, California Oil Fields, 

v. 45, no. 1, p. 33-34, 3 pls. 

Sperber, F. H., 1952, Oilfields of central San Joaquin Valley 

province in AAPG-SEPM-SEG Guidebook field trip routes, 

Joint Ann. Mtg. Am. Assoc. Petroleum Geologists, Soc. 

Econ. Paleontologists and Mineralogists, and Soc. Exploration Geophysicists, p. 153-155. 

'Veaver, C. E., and others, 1944, Correlation of the marine 

Cenozoic formations of Western North America: Geol. Soc. 

America Bull., v. 55, p. 569-598. 

Woodring, W. P., Stewart, Ralph, and Richards, R. W, 1940, 

Geology of the Kettleman Hills oil field, Calif.; stratigraphy, 

paleontology, and structure: U.S. Geol. Survey Prof. 

Paper 195. 
Article 125 

MIOCENE VERTEBRATES OF THE BARSTOW FORMATION 

IN SOUTHERN CALIFORNIA 

By G. EDWARD LEWIS, Denver, Colo. 

Abstract.-The U.S. Geological Survey has adopted the name 

Barstow Formation and abandoned Rosamond Series for the rock 

unit that crops out from Alvord Mountain to Black Mountain, 

San Bernardino County, Calif. Between 2,000 and 2,800 feet of 

sedimentary and pyroclastic rocks make up the Barstow Formation. About the upper third of the Barstow constitutes one of 

two unnamed members; it yields late Miocene vertebrates 

(Eucastor, Hemicyon, Merychippus sumani, Parucosoryx, Paramoceros). The upper half of the lower member yields middle 

Miocene vertebrates (Protohippus tehachapiensis, Brachycrus, 

Merriamoceros). No fossil vertebrates have been reported from 

the lowest third of the Barstow Formation. 

In the Mojave Desert of southern California, fossil 

vertebrates of Miocene age are found in the Barstow 

Forn1ation, which includes at least two (perhaps n1ore) 

members and local faunas. The two known faunas 

from the Barstow range in age from middle to late 

Miocene; some authorities (Schultz and Falkenbach, 

1940, 1941, 1947, 1949) would extend this range to 

early Pliocene. Outcrops identified as the Barstow 

Formation have been mapped in the Mojave Desert, 

San Bernardino County, Calif., from lat 34 °40' to 

35°15' N., and from long 116°30' to 117°20' W. The 

belt of discontinuous outcrop stretches frorn Alvord 

Mountain on the east, through the Calico Mountains 

and Mud Hills, to Black Mountain on the west. 

NOMENCLATURE OF THE BARSTOW FO,RMATION 

More than a half a century ago, 0. H. Hershey 

(1902a, facing p. 2) published a" Geological Reconnaissance Sketch Map of Southern California" that showed 

the Quaternary of the Hinckley-Barstow-Daggett 

area of the Mojave Desert and the underlying Tertiary 

Rosamond Series. This map clearly showed the 

Quaternary of the Mojave River valley at Barstow 

and for several miles eastward, where it overlies Tertiary 

rocks along the Santa Fe Railway. Two n10nths later, 

Hershey formally named, defined, and designated the 

type section for the Rosamond Series, and identified 

outcrops north of the railroad "from Hinckley station 

eastward . . . Barstow . . . Daggett" as "typical of 

the Rosarnond Series" (Hershey, 1902b, p. 365-368). 

These are the rocks mistakenly called Barstow formation by Merriam (1915, p. 252-253; 1919, p. 441-442). 

But Hershey had already pre-empted the name Barstow 

for one of the Quaternary formations shown on his 

map; in the same publication where he named the 

Rosamond, he also named, defined, and designated the 

type section of the Barstow, spoken of both as formation 

and series, "in Mohave River valley ... about one 

and one-half miles east of Barstow . . . in . . . a 

bluff just north of the railroad ... this formation 

is ... thin, overlies unconformably the earlier series 

[Rosamond], and remains generally in a horizontal 

position" (Hershey, 1902b, p. 369). 

For many years after Hershey's original definition, 

geologists working in the Mojave Desert and specifically 

in the dissected, folded upper Miocene rocks of the 

Mud Hills and Rainbow Basin about 10 miles north of 

Barstow, consistently applied the name Rosamond to 

these sedimentary and pyroclastic rocks. In one 

recent published account, Durrell (1953, p. 24) says: 

"The Tertiary rocks of the Mud Hills, the higher beds 

of which are upper Miocene (~1erriarn, 1919, p. 454) in 

age, are generally known as the Rosan1ond Series, a 

name first applied by Hershey (1902, p. 349-372)." 

During this span of time, the same usage was followed 

by those later workers who were concerned with the 

mappable, physical, stratigraphic rock units, as exemplified by Baker (1911, p. 339-~~52, 357), Pack (1914, p. 

146), Knopf (1918, p. 258), Hulin (1925, p. 42, 47, 48; 

1934, p. 419-420), E. C. Simpson (1934, p. 395-396, 

400), and Gardner (1940, p. 278, 281). Miller (1944) 

applied no forrnal na1ne to this Miocene rock unit; 

he used Tertiary volcanics in his text and on his map 

of the area. Baker (1911, p. 341), in addition to 

ART.l25 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl8-D23. 1964. 

D18 
LEWIS D19 

following Hershey's usage of the Rosan1ond, also 

recognized the overlying Barstow of Hershey and used 

the term correctly. 

Wilmarth (1938, p. 1843) cited Hershey's map legend 

(1902a) for the first usage of Rosamond, gave it an age 

assignrnen t of "Tertiary (Miocene?)," and added (under 

his second contribution, 1902b) "uncon. underlies 

Barstow Series." She (1938, p. 119) cited Hershey's 

second contribution (1902b, p. 369-370) for the first 

usage of the term Barstow, emnplete with type section, 

and added "uncon. overlies Rosan1ond," thereby recognizing the validity of Hershey's Quaternary Barstow 

Formation. But, not realizing that two different formations were involved, she also cited Merriam (1915, 

1919) in the seeming belief that his usage of Barstow 

was identical with Hershey's. 

Merriam saw Hershey's (1902a) map but evidently 

did not see Hershey's formal description of the Rosamond and Barstow (1902b, p. 365-369) because 

Merriam (1911, p. 167-168) said: "According to a 

sketch 1nap published by Hershey the point at which 

the collection was made would fall within what is 

designated by Hershey as the Rosanwnd Series. This 

series has not, however, been characterized in any way 

so that the nature of the formation is unknown. As 

geographie location is one of the important factors 

concerned, the horizon at which this eollection was 

obtained may be referred to ... as the Mohave beds." 

Merriam 2 years later referred to "the fauna ... 

represen tring a stage near Upper Mioeene . . . from 

the typical Mohave beds north of Barstow," (1913, p. 

435-436). Then in 1915 he-inadvertently, it seems 

dear-began the misapplieation of "the term Barstow ... used for the beds eontaining the Upper 

Miocene fauna" (1915, p. 251). 

This Jnistaken applieation of the unavailable term 

Barstow was followed by those later workers who were 

not concerned with stratigraphy or other physical 

geology but with the morphology of the faunal elements 

and the eOI'felation of the fauna eolleeted from the area 

about 10 miles north of Barstow. Some of these 

paleontologists used the tenn Barstow formation: 

Merriam (1919, p. 441), Sin1pson (1933, p. 81, 90), 

Wood and others (1941, p. 12, 14), and Colbert (1942, 

p. 1494). Most have written of ages and faunas-not 

formations: Frick (1926, p. 27, 34) and Stirton (1930, 

p. 218) discussed fossils from the "Barstow l\1iocene." 

Frick also used "Barstow Mio-Pliocene" (193:3, p. 607); 

and Osborn (1936, p. 742) and Stock (1937, p. 398) 

referred to fossils from the "Barstow beds." Stirton 

(1940, p. 178, 181-182) and Stirton and Teilhard de 

Chardin (19~34, p. 279-282, 284) used Barstow with the 

stipulation that such names refer to a fauna and not 

to a formation. Sehultz and Falkenbaeh did not use 

the term Barstow to refer to either a fauna or a formation, but spoke of the "Miocene deposits, north of 

Barstow" (1940, p. 223; 1947, p. 244) and the "Pliocene 

deposits, north of Barstow" (1941, p. 32). 

In short, when writing of the Tertiary rocks about 

10 miles north of Barstow, 1nany geologists, particularly 

the earlier writers, have avoided the use of Merriam's 

Barstow Forination. Many paleontologists since Merriam have not used the tenn Barstow Formation for 

these same rocks, but have applied the name Barstow 

to the fauna eontained therein. Others, including the 

Wood (1941) Committee, have used the name Barstow 

Formation for these rocks of Miocene age. The confusion regarding the use of these nan1es caused the U.S. 

Geologieal Survey, in 1924, forn1ally to abandon the 

name Rosa1nond Series and fonnally to adopt the name 

Barstow Formation for the Miocene rocks in the 

Barstow syncline. It has been so used by all Survey 

geologists since that tin1e. Hewett (1954) has published 

a summary of the up-to-date knowledge of the general 

geology of the area involved. 

FAUNAS OF THE BARSTOW FORMATION 

The manunalian genera known from all zones of the 

Barstow Formation, according to published reports, 

are listed below, with tentative synonymy, and authors' 

initials in parentheses aceording to the following 

schen1e: Frick, 1926, 1933, 1937-(F); Hall, 1930-

(H); Lewis in Byers, 1960-(L); Macdonald, 1949-

(MD); Merriam, 1919-(M); Sehultz and Falkenbach, 

1940, 1941, 1947-(SF); Stirton, 1930, 1935-(ST); and 

Stoek, 1937-(S). 

Talpa (L) 

Limnoecus (ST) 

Hypolagus (H) (L) =Lepus? (M) 

Eutamias (H) 

Diprionomys (H) 

Peromyscus (H) 

Eucastor (L) = Monosaulax (ST) 

Tomarctus (L) = Tephrocyon (M) 

Leptocyon (L) =Canis? (M) 

Hernicyon (F) 

Amphicyon (L) 

Aelurodon (L) (M) 

Bassariscus (L) 

Brachypsalis (L) 

Martes (L) 

Pseudaelurus (M) 

machaerodont (M) 

Gomphotherium (L) = Trilophodon (F)= Tetrabelodon? (M) 

Archaeohippus (M) 

Hypohippus (L) (M) 

Merychippus (L) (M) 

Dyseohyus (S) = Prosthennops? (M) 

Brachycrus (L) (SF)= Merycochoerus? (M) 

Merychyus (L) (SF) 

Ustatochoerus (SF) 

Procarnelus (L) (M) 
D20 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

Aepycamelus (L) = Alticamelus (M) 

Hesperocamelus (L) (MD) 

Rakomeryx (F) = Dromomeryx (M) 

Ramoceros (F)= Merycodus? (M) 

Cosoryx (F) 

Meryceros (F) (L) = Merycodus (M) 

H. S. Mourning, J. R. Suman, C. L. Baker, and 

tT. P. Buwalda carried on fieldwork north of Barstow 

between 1911 and 1913; their eolleetions were those that 

Merria1n first assigned to the Mohave Beds (1911) and 

later to his Barstow Formation (1915). These collections are at the ~fuseum of Paleontology, University of 

California, Berkeley. By far the largest collection was 

made by the Frick Laboratory of the American Museum 

of Natural History, between 1920 and 1940. For these 

speein1ens no identifiable locations, geographic or stratigraphie, have been published, so that no cmnparisons 

can be n1ade with specimens frmn other known horizontal (geographic) and vertical (rock unit) loeations. 

For this reason, it is only possible to quote fron1 Frick 

(1937): 

"It has been deemed advisable to consider as broadly 

conten1poraneous the ... 'Middle Miocene' to 'Upper 

Pliocene' ... tentatively united as ... the 'Late' 

Tertiary" (p. 5). "Merycodont remains are of frequent 

occurrence in the main portion of the Late Tertiary .. . 

Certain collections have been secured, frmn ... restricted and well-defined horizons of ... California" 

(p. 276). "The First, Second, Third and Fourth Divisions ... in the Barstow area" (p. 436) are mentioned 

on nun1erous pages of this publieation, but with no 

explanation of the sequence or stratigraphic significance 

of these "Divisions." 

Merycodonts are recorded as having been collected 

frmn many distinctively-but not geographicallynanled localities whose stratigraphic position in the 

fonnation is not mentioned: they are only said to 

have con1e either "frmn Barstow, California" (Frick, 

1937, p. 331-333, 347-348, 367-368) or "Barstow 

localities" (p. 435-443). Although son1e few rnay be 

synonymous, there are 24 distinctively named localities: 

"botton1 layer" (p. 368), "Green Hills deposit" (p. 

332), "Lower Green Hills" (p. 443), "Green Hills, 

indefinite locality" (p. 333), "Hemicyon Stratum" 

(p. 368, 436, 438), "Hidden Quarry"* (p. 367), "Hidden 

Hollow Quarry" (p. 368, 440), "Leader Quarry"* 

(p. 367-440), "~fayday Quarry"* (p. 347), "New 

Year Quarry"* (p. 348, 436, 438), "North End"* 

(p. 347, 439), "North End, lower layer"* (p. 347), 

"Old Mill" (p. 368), "Skyline Quarry"* (p. 331, 347, 

436, 437), above "Skyline Quarry" (p. 331), "Starlight 

Quarry"* (p. 34 7), "Steepside Quarry" (p. 332, 333, 

347), "Valley View" (p. 368, 441), "Valley View 

Quarry" (p. 436), "White Layer" (p. 368), "White 

Operation" (p. 368, 436, 439), "Yern1o" (p. 333), 

and "Yerrno Quarry" (p. 442). The only information 

relative to stratigraphy is that the "Steepside Quarry" 

correlates with the "Green Hills horizon" (p. 332), 

and that the above listed localities marked with an 

asterisk (*) correlate with the "First Division" (Frick, 

1937, p. 347-348, 367). Frick also published on "the 

occurrence in one well-defined stratun1 of two forrns of 

Hem,z:cyon" from the "Hemicyon Stratum, Barstow 

Miocene" (1 926, p. 34). 

Schultz and Falkenbach described oreodonts from 

the Frick collections, and added the following infonnation: "Frmn the Miocene deposits, north of Barstow 

... Brachycrus remains in the Barstow area are recorded only fron1 the . . . Steepside Quarry . . . Ness 

Quarry . . . Green Hills . . . Green Hills horizon or 

Second Division which underlies the later deposits 

including the' Hemicyon Straturn' of the First Division'' 

(Schultz and Falkenbach, 1940, p. 223-228); "Merychyus (Metoreodon) relictus fletcheri . . . frmn the 

Miocene deposits, north of Barstow . . . from 'Red or 

Third Division' " (1 94 7, p. 244-245); and" Ustatochoerus 

medius mohavensis ... from the Pliocene deposits, 

north of Barstow ... frmn the 'Hemicyon Stratun1' 

of the First Division" (1941, p. 32). Schultz and 

Falkenbaeh (1949, p. 80) also published a stratigraphic 

distribution chart. This work gives the best idea of 

the stratigraphic succession of some elements of the 

Frick collections. 

From 1950 to 1955 the U.S. Geological Survey was 

engaged in n1apping much of the Mojave Desert; 

during this fieldwork a collection was made, chiefly 

by R. H. Tedford and R. L. Shultz, Jr. I studied this 

collection; one of my preliminary reports is a part of 

T. W. Dibblee, Jr.'s, report in preparation on the Opal 

Mountain and Fremont Peak quadrangles, California. 

Another of n1y reports is incorporated in F. M. Byers, 

Jr's, report (1 960) on the Alvord Mountain quadrangle, 

California. The specimens discussed in these reports 

are a part of the U.S. Geological Survey collections 

at the Denver Federal Center. Both Byers (1 960) and 

Dibblee (written conununication) have n1apped several 

carefully defined Tertiary forrnations, and have made 

illustrated sections to clarify the stratigraphic relations 

of the fossil-bearing beds. 

One of the best continuous sections of the Barstow 

Formation has been rneasured and described by Durrell 

(1953, fig. 12, sections A-A' and B-B', pl. 4) in the 

Barstow syncline area about 10 rniles north of Barstow. 

Section A-A' shows 1,955 feet of sedirnentary and subordinate pyroclastic rocks within the formation, which is 

here overlain unconformably by Pleistocene sedirnents. 

Section A-A' does not include the basal beds of the 

formation, which are included in section B-B' about 

4,000 feet west of section A-A'. The basal 139 feet of 
LEWIS D21 

granitic conglomerate overlies with angular unconfornlity an older formation of granitic breccia and 

rhyolitic tuff breccia. The total thickness of the forlnation included in Durrell's two measured sections is 

2,149 feet, nnwh less than in the fossil-yielding area of 

outcrop farther west in the Barstow syncline. The 

total thickness is far frmn constant; it and the thickness 

of each individual bed have a considerable range frmn 

one part of the Barstow syncline to another. :\!lost of 

the fossil vertebrates have been collected from 27~ to 

5 n1iles west-northwest of Durrell's sections, where the 

aggregate thickness of outQrops of different parts of the 

formation adds up to at least 2,500 and perhaps as 

much as 2,800 feet. The total original thickness is not 

)nown; the highest beds, having been eroded, are either 

still being eroded or are overlain unconforn1ably by. 

Pleistocene sediments. 

There are at least two distinct faunal assemblages 

from the strata that have been called the Barstow 

Formation, but the lack of published stratigraphic data 

about the Frick collections makes a conclusive statenlent impossible. The U.S. Geological Survey collections fron1 the Barstow syncline area all come from the 

uppern1ost third of the section exposed there, where 

many old diggings and large quarries were seen. These 

localities are all either above or only a few feet below 

(stratigraphically) a conspicuous bed of white tuff as 

n1uch as 15 feet thick that crops out on the skyline as 

one travels northward up the canyon (E% sec. 23, T. 

11 N., R. 2 W.) on Fossil Bed Road (USGS Opal 

Mountain, Calif., quadrangle). Dibblee (written con1-

munication) considers this tuff as marking the base of 

the upper, unnamed member of the Barstow Formation. 

Large quarries along the strike of this, Dibblee's 

lower n1arker tuff, may represent Skyline and other 

localities of Frick's (1937, p. 331, 347) First Division 

that yielded Aferyceros (Jderyceros), Cosoryx (Paracosoryx), and Ramoceros (Paramoceros). Specimens 

referable to the first of these subgenera and to the 

Jtferychippus (Protohippus) species described by Merriam (1919, p. 479-507) are by far the com1nonest 

fossils from the uppern1ost third of the forn1ation, 

where the U.S. Geological Survey collected specimens of 

15 genera. Eu.castor, 111erychippu,s (Aferychippus) sumani, Paracosoryx, and Paramoceros are key fossils in 

this upper faunal assen1blage. Aferychippus su.mani 

and Eucastor were collected, for example, at one locality 

300 feet above the lower marker tuff. The age see1ns 

to be latest 11iocene, most nearly equivalent to that of 

the Tonopah local fauna of Nevada and con1parable to 

the oldest fauna fron1 the Ogallala of Nebraska. 

Schultz and Falkenbach (1941, p. 32; 1949, p. 80) also 

assigned this fauna to the same stratigraphic position 

on the basis of a single speci1nen of Ustatochoerus medius 

mohavensis. 

A second distinct faunal assemblage seems to come 

frmn the middle third of the section that crops out in 

Coon Canyon of the Barstow syncline area (center 

NW~ sec. 23, T. 11 N., R. 2 W., Opal Mountain, 

Calif., quadrangle). Here several old diggings in 

greenish rocks were seen. They may represent Steepside and other localities of Frick's Green Hills (1937, 

p. 99-105, 332-333) or Second Division (Schultz and 

Falkenbach, 1940, p. 223-228) that yielded Brachycrus 

buwaldi, Ramoceros (Aierriamoceros), and Rakorneryx. 

This faunal asse1ublage is considered to be of the 

same age as the Sheep Creek local fauna according to 

Schultz and Falkenbach (1 949, p. 80). This view is 

supported by the U.S. Geological Survey discovery 

(SE7~ sec. 34, T. 12 N., R. 4 E.) of Jtferychippus tehachapiensis (Buwalda and Lewis, 1955, p. 148-150) 1,200 

feet above the base of the for1nation, and of Brachycrus 

buwaldi (NWX sec. 30, T. 12 N., R. 4 E.) 1,700 feet 

above the base of the formation in the Alvord l\1ountain quadrangle, California. To be sure, the Jtferych1:ppus tehachapiensis occurs 500 feet stratigraphically 

below the Brachycrus buwaldi and could possibly represent a fauna even older than the Brachycrus. But 

Buwalda and Lewis (1955, p. 150) believed that 

Aferychippus tehachap·iens£s is close both in age and 

nwrphology to _Z\1. primus of the Sheep Creek local 

fauna of Nebraska. Perhaps the Frick collections 

coptain evidence either for or against a common stratigraphic position for the two species found in the Alvord 

l\1ountain area. With the evidence now available, we 

n1ust assume that Brachycrus is the least rare fossil in 

the fauna from the n1iddle third of the formation, and 

is a key fossil together with Ramoceros (Aferriamoceros) 

and perhaps Aferychippus tehachapiensis. 

Insofar as published inforn1ation and known experience go, the lowest third of the formation has yielded 

no identifiable fossil vertebrates. 

Aferychippus tehachapiensis, as already stated, could 

possibly represent a third fauna older than either of 

the two that are definitely recognized. A fourth fauna, 

intennediate in age between those of the Tonopah 

and Sheep Creek faunas, may conceivably be present. 

Schultz and Falkenbach (1 94 7, p. 244-245) record one 

subspecies of oreodont whose age they consider interInediate betlveen that of B. buwaldi and that of U. m. 

m.ohavens1:s: It is "the holotype . . . the only speciInen known" of "Aferychyus (Afetoreodon) relictus .fietcheri . . . from the Miocene deposits, north of Barstow ... Red or Third Division." They show the 

"stratigraphic distribution of ... each genus and 

subgenus ... species and subspecies" on a chart with 
D22 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

corresponding epochs and Great Plains formations as 

follows (Schultz and Falkenbach, 1949, p. 80-81): 

"PLIOCENE Valentine 

MIOCENE 'Lower 

Snake 

Creek' 

U statochoerus medius 

mohavensis 

Merychyus (Metoreodon) 

relictus fletcheri 

'Sheep Creek' Brachycrus buwaldi." 

This opinion of these authorities must be given great 

weight. But it is based on a solitary fragment of 

maxilla with broken and badly worn cheek teeth of a 

subgenus whose stratigraphic range is shown to be 

exactly equivalent to that of Brachycrus on the same 

chart. The "Red or Third Division" of Frick (1937) 

is a stratigraphic nomen nudum, and of no help in the 

description of the formation; presumably it is lower 

than the lower marker tuff but higher than the rocks 

that yield Brachycrus, and thus within the middle third 

of the formation. 

In resume, then, we have: (1) undisputed evidence 

that the uppermost third of the formation corresponds 

to a zone that contains an assen1blage of fossil vertebrates usually thought to occupy an upper Miocene 

stratigraphic position; (2) suggestive evidence that 

the middle third of the formation corresponds to a zone 

that contains an assemblage of fossil vertebrates usually 

thought to occupy a middle l\1iocene stratigraphic 

position; and (3) empirical negative evidence that the 

lower third of the formation contains no identified fossil vertebrates (there are undetermined algae near the 

base) and is of unknown age not younger than middle 

Miocene. 

Differences of opinion do not exist as to the correlation with local faunas of the Great Plains, but only as 

to whether the uppermost fauna should be referred to 

the uppermost Miocene according to the usual practice 

(Merriam, 1919; Simpson, 1933; Wood and others, 

1941) or to the lowermost Pliocene according to different 

authoritative opinion (Frick, 1933; Schultz and Falkenbach, 1941). Most of the diagnostic key fossilsequines, merycoidodontids, and antilocaprids-are exclusively New World forms that cannot be used for 

intercontinental correlation. Hemicyon and Gomphotherium are two genera that give direct evidence for 

intercontinental correlation of the youngest fauna; 

most authorities consider then1 to represent a late 

Miocene migration from the Old World to the New as 

part of" the most extensive faunal interchange between 

the early Oligocene and the latest Pliocene" (Simpson, 

1947, p. 639). 

REFERENCES 

Baker, C. L., 1911, Notes on the later Cenozoic history of the 

Mojave Desert region in southeastern California: California 

Univ., Dept. Geol. Sci. Bull., v. 6, p. 333-383. 

Buwalda, J. P., and Lewis, G. E., 1955, A new species of Merychippus: U.S. Geol. Survey Prof. Paper 264-G, p. 147-152. 

Byers, F. M., Jr., 1960, Geology of the Alvord Mountain quadrangle, San Bernardino County, California: U.S. Geol. 

Survey Bull. 1089-A, 71 p. [1961]. 

Colbert, E. H., 1942, The geologic succession of the Proboscidea, 

in Osborn, H. F., Proboscidea; a monograph of the discovery, 

evolution, migration, and extinction of the mastodonts and 

elephants of the world, v. 2: New York, Am. Mus. Press, 

p. 1421-1521. 

Durrell, Cordell, 1953, Geological mvestigations of strontium 

deposits in southern California: California Div. Mines 

Spec. Rept. 32, 48 p. 

Frick, Childs, 1926, The Hemicyoninae and an American Tertiary bear: Am. Mus. Nat. History Bull., v. 56, p. 1-119. 

--- 1933, New remains of trilophodont-tetrabelodont mastodons: Am. Mus. Nat. History Bull., v. 59, p. 505-652. 

--- 1937, Horned ruminants of North America: Am. Mus. 

Nat. History Bull., v. 69, 669 p. 

Gardner, D. L., 1940, Geology of the Newberry and Ord Mountains, San Bernardino County, California: California Jour. 

Mines and Geology, v. 36, p. 257-292. 

Hall, E. R., 1930, Rodents and lagomorphs from the Barstow 

beds of southern California: California Univ., Dept. Geol. 

Sci. Bull., v. 19, p. 313-318. 

Hershey, 0. H., 1902a, The Quaternary of Southern California: 

California Univ., Dept. Geol. Sci. Bull., v. 3, p. 1-29, pl. 1. 

--- 1902b, Some Tertiary formations of Southern California: 

Am. Geologist, v. 29, p. 349-372. 

Hewett, D. F., 1954, General geology of the Mojave Desert 

region, California [Pt.] 1 in Chap. 2 of Jahns, R. H., ed., 

Geology of southern California: California Dept. Nat. Res., 

Div. Mines Bull. 170, p. 5-20. 

Hulin, C. D., 1925, Geology and ore deposits of the Randsburg 

quadrangle, California: California Div. Mines Bull. 95, 

152 p. 

--- 1934, Geologic features of the dry placers of the northern 

Mojave Desert: California Jour. Mines and Geology, v. 30, 

p. 416-426 [1935]. 

Knopf, Adolf, 1918, Strontianite deposits near Barstow, California: U.S. Geol. Survey Bull. 660-I. p. 257-270. 

Macdonald, J. R., 1949, A new Clarendonian fauna from northeastern Nevada: California Univ., Dept. Geol. Sci. Bull., 

v. 28, p. 173-194. 

Merriam, J. C., 1911, A collection of mammalian remains from 

Tertiary beds on the Mohave Desert: California Univ., 

Dept. Geol. Sci. Bull., v. 6, p. 167-169. 

--- 1913, New protohippine horses from Tertiary beds on 

the western border of the Mohave Desert: California Univ., 

Dept. Geol. Sci. Bull., v. 7, p. 435-441. 

--- 1915, Extinct faunas of the Mohave Desert, their significance in a study of the origin and evolution of life in America: 

Popular Sci. Monthly, v. 86, p. 245-264. 

--- 1919, Tertiary mammalian faunas of the Mohave Desert: 

California Univ., Dept. Geol. Sci. Bull., v. 11, p. 437-585. 

Miller, W. J., 1944, Geology of parts of the Barstow quadrangle, 

San Bernardino County, California: California Jour. Mines 

and Geology, v. 40, p. 73-112. 
LEWIS D23 

Osborn, H. F., 1936, Proboscidea; a monograph of the discovery, 

evolution, migration, and extinction of the mastodonts and 

elephants of the world, v. 1: New York, Am. Mus. Press, 

802 p. 

Pack, R. W., 1914, Reconnaissance of the Barstow-Kramer 

region, California: U.S. Geol. Survey Bull. 541, p. 141-154. 

Schultz, C. B., and Falkenbach, C. H., 1940, Merycochoerinae, 

a new subfamily of oreodonts: Am. Mus. Nat. History 

Bull., v. 77, p. 213-306. 

--- 1941, Ticholeptinae, a new subfamily of oreodonts: 

Am. Mus. Nat. History Bull., v. 79, p. 1-105. 

--- 1947, Merychyinae, a subfamily of oreodonts: Am. Mus. 

Nat. History Bull., v. 88, p. 157-286. 

--- 1949, Promerycochoerinae, a new subfamily of oreodonts: 

Am. Mus. Nat. History Bull., v. 93, p. 69-198. 

Simpson, E. C., 1934, Geology and mineral deposits of the 

Elizabeth Lake quadrangle, California: California Jour. 

Mines and Geology, v. 30, p. 371-415. 

Simpson, G. G., 1933, Glossary and correlation charts of North 

American Tertiary mammal-bearing formations: Am. Mus. 

Nat. History Bull., v. 67, p. 79-121. 

Simpson, G.G., 1947, Holarctic mammalian faunas and continental 

relationships during the Cenozoic: Geol. Soc. America Bull., 

v. 58, p. 613-687. 

Stirton, R. A., 1930, A new genus of Soricidae from the Barstow 

Miocene of California: California Univ., Dept. Geol. Sci. 

Bull., v. 19, p. 217-228. 

--- 1935, A review of the Tertiary beavers: California Univ. 

Dept. Geol. Sci. Bull., v. 23, p. 391-458. 

__ ,- 1940, Phylogeny of North American Equidae: California 

Univ., Dept. Geol. Sci. Bull., v. 25, p. 163-197. 

Stirton, R. A., and Teilhard de Chardin, Pierre, 1934, A correlation of some Miocene and Pliocene mammalian assemblages 

in North America and Asia with a discussion of the MioPliocene boundary: California Univ., Dept. Geol. Sci. Bull., 

v. 23, p. 277-290. 

Stock, Chester, 1937, A peccary skull from the Barstow Miocene 

of California: Natl. Acad. Sci. Proc., v. 23, p. 398-404. 

Wilmarth, M. G., 1938, Lexicon of geologic names of the United 

States: U.S. Geol. Survey Bull. 896, 2396 p. 

Wood, H. E., 2d, and others, 1941, Nomenclature and correlation 

of the North American continental Tertiary: Geol. Soc. 

America Bull., v. 52, p. 1-48. 
Article 126 

THIRSTY CANYON TUFF OF NYE AND ESMERALDA COUNTIES, NEVADA 

By D. C. NOBLE, R. E. ANDERSON, E. B. EKREN, and j. T. O'CONNOR, Denver, Colo. 

Work done in cooperation with the U.S. Atomic Energy Commission 

Abstract.-Rhyolitic ash-flow and air-fall tuffs assigned to a 

new formation, Thirsty Canyon Tuff, of Pliocene age crop out 

from Beatty to Goldfield. The formation is subdivided into 

five newly defined formal members-the Spearhead, Trail Ridge, 

Dry Lake, Gold Flat, and Labyrinth Canyon Members-and an 

informal upper member. 

A sequence of rhyolitic ash-flow and air-fall tuffs here 

name~ the Thirsty Canyon Tuff crops out over a large 

area m the general vicinity of Beatty and Goldfield, 

Nev. The presently known extent of the forn1ation 

based on recent geologic rnapping in twelve 7%-rninut~ and three 15-rninute quadrangles and on reconnaissance 

in parts of four additional 15-minute quadrangles, is 

shown on figure 126.1. 

The Thirsty Canyon Tuff is best exposed and attains 

its n1aximum thickness north-northeast of Beatty in the 

general vicinity of Thirsty Canyon (fig. 126.1), for which 

the formation is here narned. The forn1ation is here 

subdivided into five formal men1bers and an informal 

upper n1ember. The forn1alrnen1bers are, fron1 botton1 

to top, the Spearhead, Trail Ridge, Dry Lake, Gold 

Flat., and Labyri~th Canyon. A complete stratigraphic 

sectron of the Thrrsty Canyon Tuff is nowhere exposed; 

theref~re, only a type area located in the headward part 

of Thrrsty Canyon (fig. 126.1) is designated. Type 

localities are designated for the men1bers. 

In addition to being practical cartographic units, the 

five f?rmal men1bers of the Thirsty Canyon Tuff are 

genetre rock units. Welding and cooling characteristics 

i~dicate that each mernber was deposited within a relatrvely restricted interval of tilne, and that each member 

cooled to a greater or lesser degree as a single unit. 

T~e Spearhead Member is a composite sheet; the Trail 

Rrdge Member a multiple ash-flow simple cooling unit; 

the. Dry Lake Member a simple cooling unit, probably 

a smgle flow; the Gold Flat Me1nber a compound cooling unit; and the Labyrinth Canyon Member a single 

ash-flow silnple cooling unit. (The tern1inology of 

ash-flow cooling units is that of Smith, 1960.) 

Although in 1nost places the 111e1nbers are conformable or 

paraconformable, locally they are separated by lenses 

of conglomerate and sandstone and by intertonguing 

lava flows. These rocks are excluded from the Thirsty 

Canyon Tuff. ~ The Thirsty Canyon Tuff shows much lateral variability, chiefly because of the marked topographic irregularity of the surface on which it was deposited. 

The fonnation as a whole and the individual units 

within the fonnation thin and thicken laterally in a 

complex and often unsystematic manner. Pronounced 

lateral variation in degree of welding and in the amount 

and character of devitrification and vapor-phase 

crystallization are associated with changes in thickness 

of individual Jne1nbers and of smaller units within 

men1bers. 

Preliminary studies indicate that the rocks of the 

Thirsty Canyon Tuff have sirnilar 1nineralogic and 

che1nical con1positions. Phenocrysts, which con1prise 

5 to 30 percent of the roc,k, include soda-rich sanidine, 

pigeonite, a green clinopyroxene probably containing 

appreciable amounts of aegirene and (or) hedenbergite, fayalite, strongly absorptive brown an1phibole, 

and zircon. Rare quartz phenocrysts have been found 

only in the Gold Flat ~1ember. Chemically the rocks 

are soda rhyolites and pantellerites. The chemical and 

mineralogieal similarities strongly suggest that the 

1nembers of the Thirsty Canyon Tuff are comagmatic. 

Despite these similarities, the mernbers differ appreciably both in general appearanee and petrography. 

Also, there is significant lateral and vertical variation 

in phenocryst, lithic-fragment, and pmnice content 

within the individual mernbers. 

ART. 126 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D24-D27. 1964. 

D24 
NOBLE, ANDERSON, EKREN, AND O'CONNOR D25 

..---- ____ __, I I 

l 

: NEVADA 

~' \ 

-~I Area of"' ( .. ' 

report ','-l 

0 

0 5 10 15 MILES 

L-----~----~-~ 

FIGURE 126.1-Generalized map showing presently known surface and subsurface distribution of the Thirsty Canyon Tuff 

(stippled). The formation may extend beyond queried contacts. Type area of the Thirsty Canyon Tuff is enclosed by 

dashed line. Rectangle shows area covered by figure 126.2. 

The Thirsty Canyon Tuff unconformably overlies 

the Rainier Mesa Member of the Piapi Canyon Fornlation (Poole and McKeown, 1 962). Although it postdates nwst of the Tertiary faulting ·of the area, it is eut 

by numerous north-south trending nonnal faults and, 

south of Goldfield, has undergone strong hydrothern1al 

alteration. The formation is deeply incised by canyons 

and has been eroded frOJn large areas. In most areas 

it is the youngest sequence of volcanic strata, but locally it is overlain by intermediate to mafic lavas. 

The Thirsty Canyon Tuff is dated, primarily on isotopic evidence, as Pliocene in age. A potassimn-argon 

age of approxin1ately 7.5 m.y. (R. W. Kistler, written 

communication, 1 963) has been obtained on sanidine 

frmn the lower part of the Spearhead Me1nber. Potassium-argon ages of less than 13 m.y., the MiocenePliocene boundary. of Kulp (1961), have also been 

obtained on six units stratigraphically below the 

Thirsty Canyon Tuff. In addition to the potassiumargon age of 7.5 n1.y., the structural involvement, 

hydrothennal alteration, and degree of erosion that the 
D26 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

Thirsty Canyon Tuff has undergone indicate that the 

formation is of Pliocene rather than Pleistocene age. 

SPEARHEAD 1ME,MBER 

Ransome (1909) applied the name Spearhead Rhyolite 

to an ash-flow tuff that crops out west of Goldfield. 

The unit is " ... well exposed at Rabbit Spring ... 

and in Pozo Canyon" (Ransome, 1909, p. 71), about 

three-quarters of a mile southwest of the center of 

Goldfield (fig. 126.1), where it is overlain by basalt. 

Regional mapping shows that Ransome's Spearhead 

Rhyolite is part of a large con1posite sheet forming the 

lower part of the Thirsty Canyon Tuff. 

Where described by Ransome, the Spearhead Rhyolite is a simple cooling unit 20 to 80 feet thick. However, traced to the south, this cooling .unit incorporates 

additional ash flows and in a short distance becon1es a 

compound cooling unit several hundred feet thick. 

South of Gold Flat this cooling unit is underlain by 

another compound cooling unit of sin1ilar composition 

that overlies a sequence of rhyolitic lava flows and 

1ninor tuffs inforn1ally termed the rhyolites of Pillar 

Spring. The break between the 2 units becomes progressively less distinct to the south, and disappears 

completely approximately 8 miles south of Black Mountain. Because of this merger, the lower compound 

cooling unit is also included in the Spearhead Rhyolite, 

which is here reassigned as the Spearhead Member of 

the Thirsty Canyon Tuff. 

Where the two compound cooling unit·s of the Spearhead Member are distinguishable, they are informally 

designated the upper and lower parts of the n1ember. 

The upper part is distinguished by nmnerous red to 

brown lenses of scoriaceous to massive devitri:fied glass 

that are commonly several feet in dian1eter and as much 

as a foot thick. _ 

The rocks of the Spearhead Member are highly 

variable in lithology, ranging fron1 shard tuffs to tuffs 

containing abundant pun1ice, lithic fragments, and 

phenocrysts, and frmn air-fall tuffs and poorly welded 

ash-flow tuffs to densely welded vitric and devitrified 

ash-flow tuffs. Very commonly the tops of both the 

upper and lower parts of the Spearhead Member are 

composed of lithic-, pumice-, and crystal-poor shard 

tuff. The present volume of the Spearhead l\1ember 

exceeds that of the other men1bers of the Thirsty 

Canyon Tuff con1bined. The lower part of the member 

reaches a maxi1nun1 thickne.ss of about 400 feet in the 

lower part of Thirsty Canyon. East of Stonewall 

Mountain, rocks of the upper part of the Spearhead 

Member locally reach a thickness of almost 300 feet. 

TRAIL RIDGE MEMBER 

The Trail Ridge Member is here named for Trail 

Ridge (fig. 126.2). In most outcrops the member ineludes a basal bed of air-fall pumice, generally less than 

5 feet thick but locally as much as 30 feet thick. In 

the vicinity of Black Mountain and Thirsty Canyon 

the bulk of the member consists of lithic-rich moderately to densely welded ash-flow tuff, which is capped 

by a thin unit of densely-welded shard tuff containing 

v~ry few pumice fragments or lithic inclusions and few 

phenocrysts. To the north the lithic-rich part of the 

member is absent, and the member consists entirely of 

shard tuff. 

At the type locality (fig. 126.2), north of Black 

Mountain (lat 37°21' N., long 116°39' W.), about 7 

miles west of Trail Ridge, the Trail Ridge Member is well 

exposed for several miles along the walls of a northsouth-trending canyon. Here the member, approximately 100 feet thick, overlies the upper part of the 

Spearhead Member and is paraconformably overlain by 

the Gold Flat 1\!Iember. Both the lower lithic-rich zone 

and the upper shard tuff zone are well developed. 

The Trail Ridge Member locally reaches a thickness 

of almost 200 feet in the general vicinity of Thirsty 

Canyon, but in most places is much thinner. The 

member is essentially coextensive with the Spearhead 

Member; it is generally densely welded and forms the 

caprock of a large part of Pahute Mesa. 

DRY LAKE MEMBER 

The Dry Lake Member, as here named for Dry Lake, 

crops out northeast and southwest of Dry Lake and 

north of Tolicha Peak (fig. 126.2). The member, which 

nowhere exceeds 30 feet in thickness, is lithologically 

distinct from both the underlying Trail Ridge Member 

and the overlying Gold Flat Member. Approximately 

25 percent of a typical outcrop is composed of black to 

brown coarsely vesicular blocks of pumice as much as 

3 feet in diameter. Only the uppermost part of the 

member is devitrified. 

At the type locality (lat 37°26' N., long 116°41' W., 

fig. 126.2) a section extending from the Trail Ridge 

Member through the Gold Flat Member is exposed. 

GOLD FLAT MEMBE'R 

The Gold Flat Member is here named for outcrops 

near Gold Flat. However, its type locality is about 10 

miles south of Gold Flat in the upper reach of Thirsty 

Canyon (lat 37°15' N., long 116°36' W., fig. 126.2). 

Here approximately 170 feet of the me1nber is exposed 

on the walls of Thirsty Canyon and its tributaries. 

The base of the member consists of several inches to 

about 8 feet of densely to partially fused light-brown 

tuff probably of air-fall origin. This unit is succeeded 

by densely welded generally devitrified dark-green to 

bluish-gray tuff as much as 20 feet thick which passes 

abruptly upward into densely to moderately welded 

yellow-brown or brownish-red devitrified tuff. 
NOBLE, ANDERSON, EKREN, AND O'CONNOR D27 

116°45' 116°30' 

0 5 MILES 

EXPLANATION. 

Labyrinth Canyon 

and Gold Flat 

Members 

Gold • Flat and Dry 

Lake Members 

Labyrinth 

Canyon 

Member 

Dry Lake 

Member 

FIGURE 126.2.-Map showing the distribution of the Dry Lake, Gold Flat, and Labyrinth Canyon 

Members and type localities of the Trail Ridge (TR), Dry Lake (DL), Gold Flat (GF), and 

Labyrinth Canyon (LC) Members. 

The Gold Flat Member is characterized by abundant 

lithic fragments and by complexly twinned euhedral 

phenocrysts of alkali feldspar as much as 3 em long, in 

addition to the soda-rich sanidine crystals 1 to 5 mm 

in diameter that are typical of the Thirsty Canyon Tuff. 

A distinctive ash flow, characterized by very abundant 

phenocrysts and by nun1erous cognate ejecta as much 

as several feet in diameter and composed dominantly 

of phenocrysts, forms the top of the member in the 

vicinity of the type locality. 

The member reaches a maximu1n thickness of about 

200 feet in several places in the Thirsty Canyon-Black 

Mountain area. 

LABYRINTH CANYON 'MEMBER 

The Labyrinth Canyon Member, here named for 

Labyrinth Canyon, crops out west, north, and east of 

Black Mountain (fig. 126.2). At the type locality 

(lat 37°17' N., long 116°41' W.) in the headward part 

of Labyrinth Canyon (fig. 126.2), the Labyrinth Canyon 

Member reaches its maximum thickness of approximately 50 feet. The lower 5 to 20 feet of the member 

is composed of slightly to moderately welded light-gray 

or light-brown vitric ash-flow tuff containing about 20 

716-626 0-64-3 

percent white pumice fragments. The basal vitric 

zone is sharply overlain by pink to bluish-gray devitrified tuff. 

UPPER MEMBER 

The upper member consists of two beds of white to 

gray pumice-rich air-fall(?) tuff 1 to 8 feet thick that 

crop out on the dip slope of Boulder Cuesta (fig. 126.2), 

approximately 2 miles southeast of the summit of 

Black lvfountain. The upper member overlies the 

Gold Flat Member. Although the Labrinth Canyon 

Member and the upper member are nowhere in contact, 

colluvial gravels below the upper member appear to 

overlie the Labyrinth Canyon Member. 

REFERENCES 

Kulp, J. L., 1961, Geologic time scale: Science, v. 133, p. 

1105-1114. 

Poole, F. G., and McKeown, F. A., 1962, Oak Spring Group of 

the Nevada Test Site and vicinity, Nevada: Art. 80 in U.S. 

Geol. Survey Prof. Paper 450-C, p. C60-C62. 

Ransome, F. L., 1909, Geology and ore deposits of Goldfield, 

Nevada: U.S. Geol. Survey Prof. Paper 66, 258 p. 

Smith, R. L., 1960, Zones and zonal variations in welded ash 

flows: _U.S. Geol. Survey Prof. Paper 354-F, p. 149-159. 
Article 127 

ST. KEVIN GRANITE, SAWATCH RANGE, COLORADO 

By OGDEN TWETO and ROBERT C. PEARSON, Denver, Colo. 

Abstract.-Granitic rocks of a batholith in the Sawatch Range 

were in part intrusive and in part generated in place. They 

constitute a unit that originated independently of the Silver 

Plume Granite in the Front Range, to which they were one€: 

speculatively assigned. 

The name St. Kevin Granite is here given to the 

rocks of a small Precambrian batholith and related 

plutons in the northern Sawatch Range and part of 

the adjoining Mosquito Range near Leadville, Colo. 

In the past, these rocks have been called Silver Plume 

Granite (Stark, 1935) or Silver Plume(?) Granite 

(Behre, 1953, p. 20-22). This correlation with the 

well-known Silver Plume Granite of the Front Range 

assumes an identity that has not been proved. The 

two granites have in common only the facts that they 

are both biotite-mus.covite granites that have conspicuous trachytoid porphyritic facies, and that. each 

is the youngest major Precambrian granite in its 

respective area. They differ in minor degree in petrographic details, range of composition, and characteristic accessory minerals, and, in part, in form of the 

intrusive bodies and conditions of ernplacement. 

Most importantly, however, they seem to have been 

derived from separate bodies of magma. Isotopicage data currently available suggest that the two 

granites are of the same general age, but data for 

precise comparisons are not yet available. 

The St. Kevin Granite occurs principally in a batholith about 25 miles long and 12 miles wide centered 

near the crest of the Sawatch Range west of Leadville. 

About a third of the batholith lies in the Holy Cross 

quadrangle (fig. 127.1), where it has been mapped 

in detail; the remainder has been examined only in 

reconnaissance. Many satellitic bodies of the granite 

lie in the mapped areas north and east of the batholith; 

others probably exist in the unn1apped areas to the 

south and west. The granite takes its nan1e from 

St. I{evin Lake and the adjoining St. Kevin mining 

district (fig. 127.1). 

106°45' 106° 15' 

39° ~----------------~-------------------, 

30' 

1'--

\ 

0 

HOLY CROSS 

QUADRANGLE 

10 MILES 

FIGURE 127.1.-Generalized outline of the St. Kevin batholith. 

Where it has been mapped in detail, the batholith 

is characterized by extrernely intricate borders, as 

indicated in figure 127 .2. Similar complex interfingering of granite and the wallrocks of metasedimentary gneisses is known to exist in the southern 

part of the batholith, near Mount Massive, and in 

places, at least, in the western part. The only part 

of the batholith relatively free of "islands" and projecting fingers of gneiss is an area 3 or 4 miles in 

diameter near its center. Although many of the bodies 

of gneiss within the batholith are clearly xenoliths, 

many are in structural continuity and thus appear to 

ART. 127 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D28-D32. 1964. 

D28 
TWETO AND PEARSON D29 

0 2 MILES 

FIGURE 127.2.-Generalized map of part of the St. Kevin 

batholith. 

be parts of large, attached bodies only incipiently 

sundered by the granite. Contacts between the 

granite and the metasedimentary gneisses are predominantly concordant but in detail are discordant 

in many places. Smne are of knife-edge sharpness, 

particularly in crosscutting bodies, but typically the 

contacts are gradational. In places, sill-like bodies 

of granite a few inches to tens of feet wide alternate 

with strips of gneiss of the sa1ne general dimensions 

through contact zones hundreds of feet wide. Elsewhere the transition takes place in a broad pegmatitic 

zone that consists on one side of peg1natite and granite 

in con1plex 1nixture, and on the other, of pegmatite 

and gneiss in equally complex arrangen1ent. In 

many places the gradation frmn granite to gneiss is 

ahnost imperceptibly gradual for distances of tens or 

hundreds of feet and then is con1pleted abruptly in 

distances of only inches or a few feet. In the abrupt 

parts of such zones, gneiss is peppered with feldspar 

and 1nuscovite crystals typical of the granite. In 

the remainder of the zone, the granite is streaked with 

ghosts or delicate screens of partly granitized gneiss. 

The screens outline structural features that commonly 

are in strict continuity with those in the adjoining 

gneiss. Locally, streaky granite of this type loses its 

organized fold structure in a 1nass of complex swirls 

that presumably Inark the site of liquid flow. 

The St. Kevin Granite comprises n1any textural and 

compositional varieties of granitic rocks. Four 1nain 

facies-(1) trachytoid hybrid, (2) normal, (3) granodioritic, and (4) fine grained-were distinguished in 

mapping, but each of these has va,riants, and all 

intergrade. A fifth major facies, called Hell Gate 

Porphyry by Stark and Barnes (1932, p. 34), occurs in 

the unmapped western and southern parts of the 

batholith. As recognized later by Stark and Barnes 

(1935, p. 474), this rock is merely a textural facies of 

what is here called the St. Kevin Granite, and it therefore does not warrant a formal name. We shall refer 

to the rock hereafter as the coarse porphyritic facies 

of the St. Kevin Granite. 

The trachytoid hybrid facies is a coarse-grained 

inhomogeneous rock that appears at first glance to 

consist principally of closely packed parallel crystals 

of microcline ~-1 ineh long and coarse flakes of muscovite. The feldspar crystals lie in a matrix that ranges 

from little-altered biotite gneiss through partly reconstituted gneiss to fine- or mediun1-grained granitoid 

rock. The composition of the hybrid rock varies with 

the content of gneiss, but most of it has the composition 

of quartz monzonite (see accompanying table and 

fig. 127 .3). The hybrid facies typically contains 

abundant inclusions of gneiss in addition to the films 

and fine laminae between the feldspar crystals. Irregular biotite- and silli1nanite-rich clots sheathed in 

eoarse n1uscovite are especially characteristic. The 

hybrid fae.i.es is largely confined to the border zone of 

the batholith, where it for1ns long streaks ranging 

from a few inches to hundreds of feet in width. It 

charaeteristieally lies between gneiss on one side and 

some other facies of the St. Kevin Granite on the other 

although it occurs also as streaks within other faeies. 

Many bodies of gneiss within the batholith have 

selvages of the trachytoid hybrid granite, which 

clearly is a reaetion product. In such bodies, the 

foliation of the hybrid granite g·enerally parallels that 

of the gneiss, but it parallels the contacts wherever 

they transect the foliation of the gneiss. 

The normal facies of the St. ICevin is a light-gray to 

light-pink even-grained to n1arkedly porphyritic 

biotite-n1useovite granite or quartz 1nonzonite (see 

table and fig. 127 .3). The n1icrocline in it is generally 

in prismatic or tabular subhedral erystals, even in the 

non porphyritic faeics; in many places, but especially 

ncar contacts and in small bodies, these crystals are 

oriented in trachytoid texture. In 1nany places the 

normal facies has border zones a few feet to half a 

mile wide eharaeterized by abundant thin n1ica-rich 

wisps and streaks, many of which nre clearly ren1nants 

of earlier gneiss. Elsewhere, the granite appears compositionally uniform and uncontan1inated, but the 

widespread occurrence of accessory sillimanite, and 

loeally, of garnet and packets of metan1orphic(?) 

biotite, suggests n, derivntion in part at least from older 

rocks. Now here has the granite been found to contain 
D30 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

Chemical analyses, norms, and modes of St. Kevin Granite from Holy 

Cross quadrangle, Colorado 

Normal Trachy- FineNormal facies toid grained facies 1 com- hybrid facies 4 

posite 2 facies 3 

Chemical analyses (weight percent) 

Si02-------------- 71. 15 72.41 71. 20 67. 67 Al203 _____________ 14. 54 14.40 14. 71 15. 16 Fe203 _____________ . 95 . 42 . 64 1. 32 FeO ______________ 1. 35 1. 44 1. 72 2. 41 MgO _____________ . 52 . 48 . 73 . 85 CaO ______________ 1. 02 . 77 . 75 1. 86 N a20 _____________ 2.99 2. 76 2. 56 2. 84 K20 ______________ 5.94 5.66 5. 22 5. 75 H20+ _____________ . 40 .71 1. 09 . 43 H2o-_____________ . 02 . 06 .11 . 00 

Ti02-------------- . 34 . 23 . 31 . 70 

P205-------------- . 12 . 20 .18 . 27 MnO _____________ . 03 . 03 . 04 . 04 C02 ______________ . 22 . 07 . 07 . 03 Cl ________________ . 02 . 01 . 01 . 02 F ________________ . 13 . 06 . 05 . 34 s _________________ . 01 . 01 . 00 . 01 Sr ________________ ------ . 02 . 02 . 00 BaO ______________ . 05 . 05 . 07 . 13 ------------ SubtotaL _______ 99. 80 99. 79 99. 48 99. 83 

Less 0 ____________ . 06 . 03 . 02 . 15 ------------ TotaL __________ 99. 74 99. 76 99. 46 99. 68 

Norms 

Quartz ____________ 28. 56 31. 32 33. 18 23. 70 

Orthoclase ________ 35. 03 33. 36 30. 58 "34. 47 

Albite ____________ 25.15 24.12 21.48 24.10 

Anorthite_-------- 3. 06 3. 34 3. 34 6. 67 

Corundum ________ 2. 04 2. 65 3. 67 1. 73 

Magnetite_________ 1. 39 . 70 . 93 1. 86 

Ilmenite __________ .61 .46 .61 1.37 

Enstatite__________ 1. 30 l. 20 1. 80 2. 10 

Ferrosi1ite_ _ _ _ _ _ _ _ _ 1. 19 1. 56 2. 11 2. 11 

Epidote_____________________________ . 67 

Fluorite___________ . 23 ______ ______ . 62 

Calcite____________ . 50 . 20 . 20 _____ _ Pyrite ___________________________________ _ 

Quartz ___________ _ 

Microcline _______ _ Plagioclase _______ _ 

Biotite and 

chlorite ________ _ Muscovit,e ________ _ 

Magnetite and 

Modes (volume percent) 

27. 7 

38. 7 

25. 0 

3. 6 

4. 3 

29.3 

26. 1 

25. 4 

9. 1 

9. 1 

26. 0 

33. 2 

29. 5 

7. 0 

3. 1 

Granodioritic 

facies a 

66. 75 

15. 18 

1. 29 

3. 10 

1. 12 

2. 14 

3. 59 

3.95 

. 63 

. 03 

. 83 

. 35 

. 05 

. 30 

. 03 

. 19 

. 08 

------ .11 ---

99. 72 

. 13 ---

99. 59 

25. 14 

23. 35 ~0. 39 

5. 56 

2. 96 

1. 86 

1. 52 

2. 80 

3. 30 

1. 01 

. 16 

. 70 

. 36 

28. 5 

17. 7 

34. 9 

13. 9 

3. 2 

Granodioritic 

facies 6 

66. 46 

15. 02 

2. 53 

1. 91 

1. 04 

2. 13 

3. 15 

4. 91 

. 62 

. 10 

. 84 

. 36 

. 05 

. 27 

. 02 

. 24 

. 08 

------ . 09 ---

99. 82 

. 15 ---

99. 67 

25. 44 

28. 91 

26. 72 

5. 56 

2. 45 

3. 71 

1. 52 

2. 60 

1. 01 

. 39 

. 60 

. 36 

28. 4 

23. 2 

36. 6 

8. 1 

1.9 

hematite _______ _ 0. 6 _ _ _ _ _ _ _ _ _ _ _ _ Tr. 1. 1 1. 3 

Apatite __________ _ Tr. 1. 0 Tr. . 2 . 3 Zircon ___________ _ 0. 1 Tr. Tr. . 2 . 1 

Sillimanite _______ _ Tr. T r . _ _ _ _ _ _ _ _ _ _ _ _ _ ____ _ Epidote __________ _ Tr. Tr. Tr. _ _ _ _ _ _ _ ____ _ Fluor~e __________ _ Tr. _ _ _ _ _ _ _ _ _ _ _ _ Tr. Tr. Tr. 

Calcite ___________ _ Tr. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Tr. 

1 From dump at west portal Hagerman tunnel, southwest corner of quadrangle. Analyst, V. C. Smith. (Field No. 48T57, analyticallahoratory No. Dl773.) 2 Composite sample from head of Longs Gulch. Analyst, M. Seerveld. (Field No. 69T55, analytical laboratory No. D1417.) 3 From 0.65 miles southwest of Deckers Lake. Analyst, ~L Seerveld. (Field ~o. 

72T55, analytical laboratory N3. Dl419.) 4 From west side St. Kevin Lake. Analyst, M. Seerveld. (Field No. 142T56, 

analytical laboratory No. D1418.) 5 From elevation 10,500 feet on old Colorado Midland Railroad grade on cast side 

of Busk Creek. Analyst, Paula Montalto. (Field No. 25T57, analytical laboratory No. E-2208.) 6 From prospect pit at elevation 11,625 feet on east face of Bald Eagle Mountain. 

Analyst, Paula Montalto. (Field No. 30T57, analytical laboratory No. E-2209.) 

Plagioclase 

Plagioclase 

Quartz 

0 

. · ... & X o••o :: ... . .. && XSi~ • 60 

A 

Quartz 

0 

B 

FIGURE 127.3.-A, Plot of modal quartz, 

EXPLANATION 

. Normal facies 

0 

Trachytoid hybrid 

facies 

~ 

Fine-grained facies 

... Granodioritic 

facies 

X 

Coarse porphyritic 

facies 

K-feldspar 

Orthoclase 

K feldspar, and 

plagioclase in St. Kevin Granite. B, Plot of normative 

quartz, orthoclase, and plagioclase in St. Kevin Granite. 

monazite, a characteristic accessory mineral of the 

Silver Plume Granite in the Front Range. The normal 

facies is the principal rock of the batholith; it occurs at 

the borders as well as in the interior of the batholith, 

and also as the sole facies in many isolated bodies of 

granite. 

The granodioritic facies is darker than any of the other 

facies and is porphyritic to seriate porphyritic, fine to 

1nediun1 grained, and weakly foliated. Com positionally it is on the borderline between granodiorite and 

quartz monzonite (see table and fig. 127 .3). It is 

characterized by sparsely and irregularly scattered 

white to buff rounded feldspar grains that give it a 
TWETO AND PEARSON D31 

spotted appearance. The granodioritic facies is confined largely to the interior of the batholith, where it 

forms vaguely to sharply defined streaks a few tens of 

feet to several hundreds of feet wide in granite of the 

normal facies. 

The fine-grained facies is a gray, buff-weathering, 

fine-grained, equigranular, n1assive to weakly foliated 

biotite-muscovite quartz monzonite (see table and 

fig. 127 .3). Except for scattered large flakes or clusters 

of muscovite that weather .in relief, the rock is homogeneous. It is restricted to the border zones of the 

batholith, where it forms sharply defined bodies as 

~ uch as 2 miles long and 1 mile wide. 

The coarse porphyritic facies of the St. Kevin Granite 

is biotite-muscovite granite or quartz monzonite 

characterized by abundant blocky microcline phenocrysts about 1 inch long. The groundmass is almost 

identical to nonporphyritic granite of the normal facies 

but the large and thick microcline phenocrysts giveth~ rock an appearance different from that of any of the 

other facies of St. Kevin Granite. Relicts of gneiss are 

locally abundant in the rock. The coarse porphyritic 

facies seems to be restricted to the western and southern 

sides of the batholith, but it is not nearly so widespread 

as the map of Stark and Barnes (1 935, pl. 1) showed the 

Hell Gate Porphyry to be. 

Contact relations and gradations between the various 

facies of the St. Kevin Granite suggest that all the 

facies are of the san1e general age. In places, granite 

of the normal facies clearly cuts the trachytoid hybrid 

facie~, but as the hybrid facies is almost certainly a 

reactiOn front ge.nerated by magma of the normal 

facies, there can be little difference in age at any one 

place. Although some contacts between the normal 

and the granodioritic facies are sharp and show a 

sequence of intrusion, the time relations are inconsistent 

from body to body, or even from outcrop to outcrop; 

moreover, the two rocks intergrade imperceptibly in 

n1any places, and they evidently crystallized simultaneously. Similar almost imperceptible gradation 

?et':een the normal and the coarse porphyritic facies 

Is displayed conspicuously along the west side of the 

batholith, where the two facies alternate many times 

in a distance of a few hundred feet, and where no clear 

contacts exist. Only the fine-grained facies shows in 

part a definite and consistent age relation to the other 

facies; in places it cuts both the trachytoid hybrid and 

the normal facies and contains inclusions of these rocks. 

In other places, however, -the fine-grained facies seems 

to grade both into normal and granodioritic facies, 

and we therefore consider it to be of the same general 

age as the other facies. 

The St. Kevin Granite evidently was in part generated 

in place and in part crystallized from a mobile melt 

that was a magma in every sense of the word. Metasomatism or granitization in place is shown by the reaction 

selvages of trachytoid hybrid granite, and by the faithful 

preservation of folds and other structural features of 

the gneissic wall rocks in granite half a mile or more 

fro_m the edge of the batholith. On the other hand, 

evidence of intrusion is compelling. Many dikes and 

sills as well as parts of the border of the main batholith 

have sharp contacts that show no sign of granitization; 

foliation in the granite faithfully follows the contacts 

wherever they crosscut the gneiss; inclusions of unaltered wallrocks that can be traced with certainty 

to a nearby source lie within the granite; metasomatic 

rocks identified by their ghost gneissic structure are 

disrupted by local zones of flow, some of which extend 

as dikes into the wallrock gneisses; and the long, 

straight or arcuate, diffuse contacts between different 

varieties of rocks in the interior of the batholith suggest 

boundaries between streams of magma rather than 

any structure inherited from pre-existing metamorphic 

rocks. 

We conclude that (1) from the widespread evidence 

of liquid movement, most of the St. Kevin batholith 

wa~intruded as magma at the crustal level now exposed; 

(2) from the widespread evidence of n1etasmnatism, 

an additional substantial fraction of the St. Kevin 

Granite was generated at the level now exposed; (3) 

from the evidence of local mobilization of metasomatic 

rock, and from the intricate, generally concordant, 

form of the batholith borders, the wallrocks were at 

practically the same temperature as the invading 

granite and in a relatively plastic state; (4) from the 

occurrence of probable relict metamorphic minerals 

such as sillimanite and garnet in the intrusive part of 

the batholith, the batholithic mag~na was generated by 

melting of gneisses si1nilar to those which it intrudes; 

and (5), from conclusions 2, 3, and 4, the intrusive 

n1agn1a 1nay have been generated at a crustal level 

little deeper than the one now exposed. 

Thus we believe we see the St. Kevin batholith at 

about the top of its root zone, or the zone of transition 

fron1 One of lllagma generation by crustal n1elting below 

to one of intrusion above. If this is so, and the batholith is a product of local 1nelting, the granite is a 

unit genetically distinct from the Silver Plume Granite 

and its cognates in the Front Range, even though it 

is probably of the same general age. 
STRATIGRAPHY AND STRUCTURAL GEOLOGY 

REFERENCES 

Behre, C. H., Jr., 1953, Geology and ore deposits of the west 

slope of the Mosquito Range: U.S. Geol. Survey Prof. 

Paper 235. 

Stark, J. T., 1935, Migmatites of the Sawatch Range, Colorado: 

Jour. Geology, v. 43, p. 1-26. 

Stark, J. T., and Barnes, F. F., 1932, The structure of the Sawatch Range: Am. Jour. Sci., .5th ser., v. 24, p. 471-480. 

--- 1935, Geology of the Sawatch Range, Colorado: Colorado Sci. Soc. Proc., v. 13, p. 467-504. 
Article 128 

REINTERPRETATION OF THE LATE GROWTH OF THE GYPSUM VALLEY SALT ANTICLINE, 

SAN MIGUEL COUNTY, COLORADO 

By FRED W. CATER, Denver, Colo. 

Abstract.-Reinvestigation of outcrops in the southeast end of 

the anticline indicates that the relation of Cretaceous beds to 

Paleozoic rocks is explained best by faulting and landsliding 

rather than by sedimentary pinchouts and thinning as proposed 

previously. 

Reexamination of the Gypsun1 Valley area, San 

Miguel County, Colo., (fig. 128.1) has suggested changes 

in an earlier stratigraphic and structural interpretation of the area by the author. In an earlier report 

(Cater, 1955), the author stated that although upthrusting of salt into the core of the salt anticline 

underlying the valley seemed generally to have ceased 

by the beginning of Morrison (Late Jurassic) time, 

inconclusive field relations in the southeast end of the 

valley indicated that Paradox beds (Pennsylvanian) 

had intruded rocks as high as the Mancos Shale (Late 

Cretaceous). Earlier, Stokes and Phoenix (1948) 

reached virtually the same conclusion. Landis and 

others (1961) stated, however, that: "The overall 

distribution of the Mancos and l\!Iesaverde relative to 

the salt structures appears to be best explained by a 

pinchout of pre-Mancos Cretaceous rocks and a thinning of the Mancos on the salt structures." Inasmuch 

I 

I 

0

La Sall\ 

\~ 

0 

\--

1 

I 

I 

10 

Ur\~, .~~~~. 

MONTROSE ~.~ Naturita 

SAN MIGUEL 

20 MILES 

a.._ Area of 

geologic map 

FIGURE 128.1.-Index map showing location of area described in this article. 

as this interpretation differs radically from that of the 

earlier writers and because the scientific and economic 

implications of a correct explanation of the observable 

geologic relations are of considerable importance, the 

author reexamined part of the area. This reexamination indicates that neither of the preceding explanations 

is entirely consistent with the mappable relations. It 

now seems that Stokes, Phoenix, and the author were 

wrong in postulating possible late intrusion of Paradox 

beds into the Mancos, and that Landis and others were 

wrong in explaining the relations as a thinning and 

pinchout of Cretaceous rocks on salt structures. 

Mancos that rests on Paradox is explained best by 

landsliding, whereas the pinchout proposed by Landis 

and others is explained best by faulting, as indicated 

in an earlier paper (Cater, 1955). 

The differences between the interpretation presented 

herein and that of Landis and others (1961) arise from 

the identification of formations at some outcrops and 

from evaluation of evidence of faulting and landsliding. 

These differences are shown in figure 128.2. The 1nap 

in figure 128.2A is reproduced from part of figure 197.2 

of Landis and others (1961); that in figure 128.2B is 

of the same area, showing this author's revisions. The 

differences, though minor, are critical. The geologic 

section in figure 128.2A is reproduced from part of their 

figure 197 .3, and that in figure 128.2B is the author's 

revision of the same geologic section. 

In a gully in the southeast corner of the area (fig. 

128.2A) the Salt Wash Member of the Morrison Formation is shown by Landis and others as a thin sliver 

adjacent to a fault between the 7,180-foot and the 

7,240-foot contours, whereas according to the author's 

interpretation (fig. 128.2B) the Salt Wash is relatively 

flat lying and much more extensive and does not 

extend as far northwest down the gully. To the 

northwest, Landis and others have mapped outcrops in 

three localities as Burro Canyon(?); the author interprets them differently. At locality A (fig. 128.2B), in 

ART.128IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D33-D37. 1964. 

D33 
D34 

Qal / 

/ 

/ 

/ 

( 

\ 

\ 

\ 

j 

A 

STRATIGRAPHY AND STRUCTURAL GEOLOGY 

/6700 

c? 

"" 

Qg 

ml's 

o:u 

.(1):.6) 

(/):(/) 

Qg 

69oo 

7ooo 

Qg 

CONTOUR INTERVAL 100. FEET 

A 

Kmv 

f" 

\Qg) 

\} 

'YKmv 

1/ 

,----..._ 

I 3~ ',"' 

~~~--_) 

~.-l(Kmv 

~56 

,......\ 

0 

Km 

B 

g> 

38° 

00' 

30" 

Qg T. 

43 

N. 

7200 

CONTOUR INTERVAL 100 FEET 

A' A 

Qg 

------- ~~ 

Kmv 

--------- Km 

B 

500 1000 FEET 

-----

38° 

00' 

30" 

T. 

43 

N. 

A' 

FIGURE 128.2.-Geologic maps and ·sections of part of southeastern Gypsum Valley, San Miguel County, Colo. A, mapping and 

interpretation by Landis and others (1961, parts of figs. 197.2, 197.3); B, mapping and interpretation by the author. Circled 

letters in B are localities discussed in text. Numbers in sections refer to subdivisions of the Rico Formation and the upper member of the Hermosa F.o'l"..l:l:ation shown by Landis and others (1961, fig. 197.4). 
EXPLANATION 

>-

~ 0:: 

~i <( 

~ ~ Alluvium z 

~~ 0:: 

~ w 

~] I-

<( 

Gravel deposits :::l 

UNCONFORMITY 0 

~ 8 l-- 5 ~ ~ Mesaverde Formation (/) ~~ :::l 

~~ G 0 (5 w 

Mancos Shale u 

<( 

UNCONFORMITY I- ~ w 

~s { ~ 0:: ~~ u ;:s~ o.S Burro Canyon(?) Formation ~~ Shown only on Map A (5 

-~ 8 ~ u ~ Salt Wash Sandstone Member ~ of Morrison Formation (/) l-- (/) 

~ 0 <( 

l-- 0:: ~ 

~ :::l 

~ Entrada Sandstone ..., 

Shown only on Map A u -~ ~ UNCONFORMITY (/) ~ (/) 

~ -~ 

l--

{ 

Chinle ~ Formation _) ~~ I- ~ 

~ UNCONFORMITY z ~ 

~~ 

l--

Cutler 

G 

Formation }~ ~-~ UNCONFORMITY 0.. ~ 

]] { z I ~, I <( ~~ ~ 

~~ z 

~~ { 

Rico Formation <( 

> 

...J 

-

>- -~ (/) 

~a z 

Upper member of Hermosa Formation z 

~~ w 

~~ 0.. 

~ ----....___ _______ 

Contact 

Dashed where approximately located; 

dotted where concealed 

----tf------·· Fault 

Dashed where approximately located; dotted where 

concealed. U, upthrown side; D, downthrown side 

35;/ 

Strike and dip of beds 

90/ 

Strike of vertical joints 

c 

Prospect 

FIGURE 128.2.-Continued 

(/) 

:::l 

0 

0:: 

w 

LL 

z 

0 

ID 

0:: 

<( 

u 

CATER D35 

the gully at 7,060 feet altitude, an outcrop only 3 feet 

wide and 5 feet long is shown by them on figure 128.2A 

as Burro Canyon(?) Formation. It is fine-grained buff 

sandstone, and although it is conceivable that a bed of 

similar material thick enough to have produced a block 

of this size could be found in the Burro Canyon, the 

author has never seen one in the course of several field 

seasons of mapping in the region Furthermore, the 

outcrop possesses none of the diagnostic features 

characteristic of the Burro Canyon. It is, on the 

contrary, almost identical with sandstones of the 

Mesaverde Formation on the east side of the gully and 

apparently is a slice of that formation caught in a fault 

subsidiary to the main fault zone of the area. About 

1,200 feet north-northwest of this outcrop, at an 

altitude of 7,050 feet (locality B, fig. 128.2B), the 

outcrop called Burro Canyon(?) by Landis and others 

resembles conglomerates of that formation, but on close 

examination the rock is seen to be a conglomeratic 

arkose. As the Burro Canyon is nonarkosic, this 

outcrop is interpreted by the author as Permian Cutler 

Formation. Less than a hundred feet northwest of 

this outcrop is another, also shown by Landis and others 

as Burro Canyon(?). This second outcrop at locality B 

is fine-grained sandstone identical with the Mesaverde 

concealed beneath gravel deposits uphill to the east and 

is almost certainly a slumped block of Mesaverde 

resting on the Cutler. The actual contact with the 

Cutler is not visible. In summary, the Burro Canyon 

does not crop out in the area; thus it cannot be used as 

evidence in an argument favoring deposition of Cretaceous rocks on formations older than the Morrison. 

Other questionable identifications in this area are 

strata shown as Salt Wash on the 7,000-foot contour, 

where it crosses section A-A' (fig. 128.2A), and almost 

certainly the rock shown as Entrada Sandstone about 

200 feet to the north at an altitude of 6,990 feet 

(locally C, fig. 128.2B). The rock shown as Salt 

Wash is Mesaverde. That shown as Entrada resembles 

the Entrada superficially but differs from it in that it 

contains subangular pebbles of clear quartz Ys inch in 

diameter, it is less well sorted, and, although it contains 

large round frosted grains of quartz, the grains are 

scattered haphazardly through the rock rather than 

deposited in distinct layers.~ In all probability this 

rock also is Mesaverde, for there is similar material 

uphill in nearby outcrops of Mesaverde. At the 

northwest corner of the area, between the 6, 700-foot 

and 6,800-foot contours (locality E), Mancos is mapped 

as resting on Rico where, in fact, there are no exposures. 

There is little doubt, however, that beneath the soil 

cover and overburden,. Mancos does rest on Rico, but 

it is a mass of Mancos that has slumped downhill. 
D36 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

A few feet north of the pit that Landis and others 

show at an altitude of 6,690 feet on the map (locality 

D) is a second pit that they do not show; this pit 

exposes a contact of Mancos and Cutler. Bedding in 

the Mancos is not badly disturbed and is roughly 

parallel to the surface of the underlying Cutler to 

within about 15 inches of the contact. Bedding in 

this lower part, however, is cmnpletely destroyed; 

fragments are slickensided and crushed, and the basal 

4 to 6 inches contains stretched out lentils of pulverized 

Cutler as much as an inch thick and a foot longsuggesting a fault on the base of a landslide. All other 

isolated masses of Cretaceous rocks that rest on older 

rocks mentioned in the foregoing paragraphs are almost 

certainly masses of similar material that have moved 

downhill. In fact, were this an area where Cretaceous 

rocks wedged out against Paleozoic rocks, it would be 

reasonable to expect to find at least a few outcrops of 

Mesaverde to the west of the gully that generally 

follows the west edge of the Cretaceous rocks in the 

northwest part of the mapped area; however, none are 

found there. Furthermore, the Mesaverde on the east 

side of this gully is fractured and broken into jumbled 

but still juxtaposed blocks, a fact hinted at by Landis 

and others on their map (fig. 128.2A), which shows a 

strike-and-dip symbol east of the gully near the lower 

contact of the Mesaverde at 6,910 feet. This symbol 

shows beds striking east and dipping 38° S., an attitude 

unrelated to the mapped contact im1nediately below. 

The jumbled nature of the Mesaverde results from 

slumping of the underlying Mancos, a formation 

unsurpassed in the region for its ability to form 

landslides, son1e of then1 of enor1nous size. 

Although the trace of the fault that separates 

Cretaceous rocks from older rocks is covered by Mancos 

and Mesaverde rocks and by gravel of Quaternary age, 

north of where Landis and others mapped the fault in 

the southeast corner of the area of figure 128.2, fairly 

direct evidence for its north-northwestward continuation shows in the face of the previously mentioned pit 

at 6,960 feet (locality D). In the face of this pit is a 

north-northwesterly trending fault which is not shown 

on their map. Although this fault is in the Cutler 

Formation, it is parallel to and only a few feet from the 

edge of the Cretaceous rocks and is probably subsidiary 

to a n1uch larger fault. Considerable quantities of 

copper minerals (n1alachite) have been deposited in and 

adjacent to this fault, and it is perlu1ps significant that 

other similar copper occurrences in the area are closely 

associated with large faults (Vogel, 1960). 

To the southeast, beyond the area shown in figure 

128.2, the fault swings to the southeast and for 6 miles 

forms the southwest margin of the synclinal graben 

occupying the collapsed crest of the Gypsum Valley 

anticline. Vogel (1960) shows the throw on this fault 

to exceed 3,500 feet immediately southeast of the 

mapped area. It seems unlikely that a fault of this 

magnitude could die out completely along the strike in 

a distance that is less than the throw. 

At a number of localities shown by Landis and others 

(1961, fig. 197.2), but not shown on figure 128.1A of 

this article, Mancos rests directly on Paradox beds. 

Landis and others consider the contact to be sedimentary, whereas Stokes and Phoenix (1948) and Cater 

(1955) believed that the salt was intruded into the 

Mancos. It is doubtful whether either of these explanations is valid. With collapse and erosion of the crestal 

rocks in the anticline, conditions became ideal for 

landsliding of the Mancos from the partly surrounding 

uncollapsed masses of Mancos and Mesaverde that 

formed relative highlands. It seems most likely that 

these masses of Mancos that now rest on the Paradox 

are but the partly eroded remnants of former landslide 

blocks. In this connection it is interesting to note that 

Vogel (1960) described a butte in Disappointn1ent 

Valley, a few miles south of this area, that is capped by 

a landslide consisting of the upper part of the Mancos 

and the Mesaverde; this slide rests on Mancos that 

belongs stratigraphically 1,300 feet below the top of the 

formation. The slide is several n1iles from the nearest 

outcrops of the Mesaverde. 

A more spectacular structural history than that 

shown by the evidence is implied if the thesis of Landis 

and others is accepted. For the Mancos to wedge out 

against Rico and Cutler beds would require a spire of 

the Rico and Cu tier less than a mile across to rise 

more than 4,000 feet above the base of the surrounding 

Salt Wash during Mancos time. Field observation does 

not support this supposition; in fact, one of the reasons 

why the history of development of the salt anticlines is 

so well preserved in the southeast end of Gypsum Valley 

is that the rise of salt was less pronounced in this area. 

Upper Paleozoic beds are preserved as are pre-Morrison 

Mesozoic formations, and the unconfor1nities between 

these formations preserve the record of anticlinal 

growth. In other places the salt rose more vigorously; 

overlying beds were turned up sharply and removed 

from the crest of the salt cores, and pinchouts of preMorrison beds are abrupt and mostly buried under 

younger rocks in the flanks of the anticlines. Yet here 

in the very area where the rise of salt had been relatively slow during growth of the salt cores, the interpretation of Landis and others requires that a spire of 

Rico and Cutler beds be thrust upward several thousand 

feet, tens of millions of years after substantial flowage 

of salt had ceased (at the beginning of Morrison time). 

Then, by their interpretation, this same spire would 

have had to subside to a position lower than the one it 
CATER D37 

originally occupied, and all without appreciable 

faulting. 

REFERENCES 

Cater, F. W., Jr., 1955, Geology of the Gypsum Gap quadrangle 

Colorado: U.S. Geol. Survey Geol. Quad. Map GQ-59. 

Landis, E. R., Shoemaker, E. M., and Elston, D. P., 1961, Early 

and late growth of the Gypsum Valley salt anticline, San 

Miguel County, Colorado: Art. 197 in U.S. Geol. Survey 

Prof. Paper 424-C, p. C131-C136. 

Stokes, W. L., and Phoenix, D. A., 1948, Geology of the EgnarGypsum Valley area, San Miguel and Montrose Counties, 

Colorado: U.S. Geol.- Survey Oil and Gas Inv. Prelim. 

Map 93. 

Vogel, J. D., 1960, Geology. and ore deposits of the Klondike 

Ridge area, Colorado: U.S. Geol. Survey open-file report, 

205 p. 
Article 129 

A PLEISTOCENE SECTION AT LEONARDS CUT, 

BURKE COUNTY, NORTH CAROLINA 

By JOHN C. REED, JR., BRUCE BRYANT, ESTELLA B. LEOPOLD, and LOUISE WEILER, 

Denver, Colo. 

Abstract.-An exposure of peat described by Kerr in 1875 at 

Leonards Cut probably accumulated on a former flood plain of 

the Catawba River well below the Piedmont Upland surface. 

Pollen assemblages and field relations show that the deposit is 

nonglacial and probably represents an interglacial episode of 

Pleistocene age. The Piedmont Upland surface in the area may 

therefore be pre-Pleistocene. 

Organic remains in surficial deposits are very unusual 

in the Piedmont Province in North Carolina. We were 

therefore surprised and interested when R. A. Laurence 

of the U.S. Geological Survey (written communication, 

1961) called attention to the following description of 

Leonards Cut by Kerr (1875, p. 157): 

The railroad cuts through the piedmont region, especially 

from Morganton to the foot of the Blue Ridge furnish many 

admirable sections of hill side drift. The most interesting is 

9 miles beyond Morganton, known as Leonards cut. On the 

upper slope of a high hill a cut of 80 feet exposes a bed of peat 

and drift wood 15 feet thick with the underlying soil filled with 

stumps and roots. Above the peat is a bed of rudely stratified 

gravel and sand, 10 to 15 feet deep, on which grows the present 

forest. In the peat are numerous shining wing-covers of beetles 

and seeds of many species of plants, cones of several kinds of 

pine, and of hemlock, squirrel-gnawed hickory nuts, seed pods 

of kalmia, etc. No species have been observed which are not 

found at present living in the region . . . 

With the aid of Mrs. M. R. McVey of the MorgantonBurke County Public Library in Morganton, we 

located Leonards Cut 2.45 miles west of the Glen 

Alpine railroad station along the Southern Railroad 

(figs. 129.1 and 129.2). 

Leonards Cut is in the southwestern part of the 

Morganton basin, a northwestern extension of the Piedmont physiographic province enclosed by the Blue 

Ridge on the northwest, the Hickorynut Mountains on 

the southwest (outside the area shown on fig. 129.1), 

35°45' 

5 0 

_,.,,.., Iz;;;;---7- f1 report NORTH 

CAROLINA ------""' 0 

[____j 

lOO:~L~, 

5 10 MILES 

FIGURE 129.1.-Map of part of western North Carolina, showing 

location of Leonards Cut (X). The outlined area surrounding 

Leonards Cut is shown on figure 129.2. 

the South Mountains on the southeast, and the Brushy 

Mountains on the northeast (outside the area shown 

on fig. 129.1). The basin is drained by the Catawba 

River and its tributaries, which have excavated steepsided flat-bottomed valleys 100 to 300 feet deep separated by flat even-crested interfluves. Farther east the 

interfluves are less dissected and form the flat surface of 

the Piedmont Upland. 

ART. 129 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D38-D42. 1964. 

D38 
REED, BRYANT, LEOPOLD, AND WEILER D39 

1000 0 3000.FEET 

L_ __ ~CO~N~T~O~UR~IN=T~ER~V AL 40 FE --~ 

FIGURE 129.2.-Topographic map of the area surrounding 

Leonards Cut (X). 

Near Leonards Cut the interfluve surfaces are at altitudes of about 1,300 feet; the surface of the Catawba 

River, 0.6 mile north of Leonards Cut, is at an altitude 

of about 1,040 feet. 

Since Kerr made his visit the cut has slumped and 

become much overgrown with hon eysuckle, but a small 

gully (fig. 129.3) south of the tracks exposes a fairly 

complete section of surficial material, including Kerr's 

peat bed (table 129.1, fig. 129.4). 

The peat bed does not extend more than 50 feet east 

of the erosion gully, and it is absent on the north side of 

the tracks opposite the exposure in the gully. It may 

extend several hundred feet farther west. 

The deepest part of the cut, several hundred feet cast 

of the gully, exposes only 10 to 15 feet of red colluvial 

clay overlying 30 to 40 feet of saprolitizcd mica schist 

and gneiss. In the north side of the cut, less than 40 

feet north of the gully, yellow-gray alluvial silt and 

clay rest directly on saprolitized bedrock. 

The uppermost surficial deposits are exposed in cuts 

along the north side of a dirt road parallel to and about 

200 feet south of the railroad (fig. 129.2). This material 

is rudely sorted angular gravel and coarse brown sand 

FIGURE 129.3.-Gully on south side of Leonards Cut in which 

peat and overlying unconsolidated deposits are exposed. 

U.S. Geological Survey paleobotanical localities D1995A and 

D1995B indicated by A and B, respectively. 

containing saprolitized fragments of gneiss, schist, and 

pegmatite arranged in crude foreset beds that dip 

30°-40° W. To the west it grades into finer grained 

material that overlies the red clay layer at the top of 

the measured section. The sand and gravel deposit 

is absent in cuts on the south side of the road and in the 

railroad cut to the north. 

The peat probably accumulated in a shallow pond or 

swampy area at the edge of a former flood plain of the 

Catawba River. Similar swampy areas are common 

along modern streams in the area. The overlying 

stratified silt and clay is similar to material underlying 

the present flood plain of the Catawba. The red clay 

is typical of the residual and colluvial clay that 

mantles most slopes in the area. The rudely stratified 

sand and gravel probably filled a gully cut into the 

colluvial clay before the Catawba assumed its present 

course. The field relations of the gully-fill deposit 

indicate considerable modification of the topography 

since its deposition. 

The deposits at Leonards Cut offer the only known 

clue to the minimum age of the Piedmont Upland 

surface in the Morganton basin. The organic material 

lies well below the level of the upland surface, but more 

than 120 feet above the present master drainage. A 

radiocarbon age of 2,270 ± 200 years for organic material 

near the base of the alluvial deposits on the present 

flood plain of Muddy Creek about 7 miles southwest of 

Leonards Cut (Suess, 1954) indicates that the master 
D40 

FEET 60 DISTANCE ABOVE 

BASE OF SECTION 

50 

40 

30 

20 

10 

Dl9958 

Dl995A / 

STRATIGRAPHY AND STRUCTURAL GEOLOGY 

-.- Approximate trend of section N.1o•w. 

0 

APPROXIMATE SCALE 

z 

0 

;:: 

u 

w 

1/J 

~ 

Gully-fill deposits 

gneiss 

Approximate trend of section due east ___.. 

50 FEET I 

FIGURE 129.4.- Diagrammatic section of unconsolidated deposits exposed in gully on south side of Leo nards Cut. D1995A and 

D1995B, locations of pollen samples described in table 129.2. 

TABLE 129.1.-Stratigraphic section of unconsolidated deposits exposed in a gully on the south side of Leonards Cut 

[Base of section 2 feet below level of top of railroad track>; elevation about 1.160 feet] 

Type of deposit Distance 

(fig. 129.4) above base 

(feet) Lithology Remarks 

Colluvial 28- 33 Unstratified red clay; 6-inch gray layer at base. Basal contact Similar red clay rests directly on 

irregular and gradational. saprolitized bedrock 200 feet 

east of section. 

Colluvial or 19-28 Unstratified yellow-gray silty clay containing scattered mica 

flood plain flakes and feldspar grains. 

Flood plain 

Stratified gray silt and clay containing thin sanely layers. A few 

12-19 organic layers as much as 2 inches thick becoming less common near top. Scattered fragments of carbonized wood near top. 

10--12 Dark, brown silt and clay containing thin sanely layers. 

5-10 Dark-gray organic silt and peat containing scattered wood frag- USGS paleobot. Joe. D1995B at 

ments. top of interval. 

Swamp 

Dark-gray organic silt and peat containing wood fragments, USGS paleobot.loc. Dl995A 3 feet 

0-5 flattened logs as much as 6 inches in diameter, and a few nuts above base of section. 

and hemlock('!) cones. Base not exposed. 
REED, BRYANT, LEOPOLD, AND WEILER D41 

drainage has been at about the present level for at 

least that length of time. 

Pollen and spores from samples of organic silt and 

peat from 3 feet (USGS paleo bot. loc. D 1 995A) and 

10 feet (USGS paleobot. loc. D1995B) above the base 

of the exposed section in Leonards Cut have been 

examined and the pollen assemblages compared with 

those from samples of organic muck from nearby 

modern bogs (table 129.2). All identified pollen and 

spores in the Leonards Cut fossil material are representative of plants that g:row in the area today; no 

relict Tertiary genera and no northern ele1nents were 

found. The main difference between the assemblages 

of fossil and 1nodern pollen is that spruce and fir, which 

make up between 1 and 4 percent of the fossil material, 

TABLE 129.2-Pollen types identified in organic layer at Leonards 

Cut and in new·by muck deposits of Recent age (percent of total 

pollen) 

[X, present] 

Leonards Cut fossil ModE'rn samples 

samples 

D1995A D1995B Dl991 D1992 

--------------·1-------------

Gymnospermae: 

Pinus (pine)_-----··-------------- ___ _ Picea (spruce) __ ---·------------------ Abies (fir) ________ -··-- _______________ _ Tsuga caroliniana (hemlock) ________ _ T. canadensis (hemlock) ____________ _ Juniperus type (juniper?) ___________ _ 

Angiospermae: 

52.5 

3.9 

.4 

1.5 

1.5 

.8 

61. 5 76. 0 62. 0 

. 4 ---------- ---------- 1.3 ---------- ---------- .5 . 5 

. 8 ---------- ----------

Corylus (hazel)________________________ __________ . 4 ___________________ _ 

Carya (hickory)_______________________ 7. 8 1. 7 1.0 4. 2 

Ouercus (oak)________________________ 7. 0 4. 6 1.0 11 2 

Alnus(alder)________________________ 

i~~~i.1Irt~!~~~1~i"~n~~-~~~ =====:}: 

3.1 

;;;;::::;; 

2.9 

=:: :=:~::: 3.0 =::: =: -,~: 4.7 

~;~~gz~~~hs~~eef!i:;r)-~~============= x . 4 ========== ========== -------~~~ Nemopanthus (mountain holly)______ .4 X ___________________ _ 

ChenopodiaeE'ae _____ ---------------- __________ . 4 . 5 

n~;:!~~~~~~~~~~=:-~~~~=~~~~~===~==== ~ricales_______________________________ 5. i:~ 0 iJ 1. 7 ======~=~= __________ ----------=======~=~ ypha latifolia (cattail)_----------------------- . 4 ---------- _________ _ Dicots undE'L __ ----------------- 4. 7 3. 4 2. 0 2. 8 Monocotsund~·t_________________ 5.0 3.4 1.0 _________ _ Campanula?__________________________ X _____________________________ _ 

Symphoricarpus (sllowherry)_________ __________ __________ 4.5 1.0 

Total number pollen grains counted_____ 258 238 207 214 

Lower plants: Spores: 

Alga~V;;J~~~~u~i(ci~'b~~~~)~)--_~===== ~ ========== ========== ========== 

~::~~~J:~~~- ~~~-e---=~============= ----~---- i========== I========== ----X---- Veryhachium type________________ X _____________________________ _ 

U.S. Geological Survey palE'obotanicallocalities. 

D1995A._ Leonards qut locality, Burke County, N.C. Prat 3 frrt ahow base 

of sectiOn exposed m gully on south side of railroad. Location indicated on figures 129.2 and 129.3. 

D1995B .. Leonards c_ut locality, Burke County, N.C. Peat 10 feet above hase 

of sectiOn exposed m gully on south side of railroad. Location indicated on figures 129.2 and 129.3. 

D1991. Organic muck from depression on flood plain of Catawba Hivrr immediately north of bridge at Bridgewater (fig. 129.1). 2.05 miles N. 85° W. of 

Leonarcls Cut (collected by C. T. Sumsio11). 

D1992. Organic. muck from spring o.r seep on hillside about 200 feet south of 

Leonarcls Cut (collected by C. T. Sumsion). 

are absent in the modern material. Since these genera 

now grow at higher elevations 25 miles west of the fossil 

locality, this suggests that these gymnosperms were 

growing at least in small numbers closer to the Leonards 

Cut locality at the tin1e of deposition than at the 

present time, but the climate was probably not much 

different than the present one. 

Deposits silnilar to those at Leonards Cut are unusual in the Piedmont province, although logs associated with organic clays have been discovered in 

exhu1ned gully fills in Cleveland County, N.C., and 

Spartanburg County, S.C. C\Vhitehead and Barghoorn, 

1962). The radiocarbon age of a log from near the 

base of one deposit north of Shelby in Cleveland 

County is greater than 30,000 years (Suess, 1954). 

A pollen profile froin this locality (Whitehead and 

Barghoorn, 1962) records little change within the 

4-foot section, and contains an assemblage very similar 

to that at Leonards Cut. However, it contains two 

elements not found at Leonards Cut: Ephedra (Mormon's tea), a western shrub now exotic to the eastern 

United States, and Arceuthobium (dwarf mistletoe) 

now occurring in the northeastern United States. 

This locality is about 40 miles from the nearest present 

day occurrence of spruce and fir; it is about 100 feet 

lower than Leonards Cut and is about 30 miles to the 

southeast. 

Eargle (1940) has described deposits of organic 

material deeply buried by soil in Spartanburg County, 

S.C. The radiocarbon age of logs imbedded in two of 

these deposits is greater than 34,000 years (Rubin and 

Alexander, 1958) or greater than 35,000 years (Whitehead 

and Barghoorn, 1962). Cain (1944) studied pollen 

frmn four sections of these buried soils. Assernblages 

near the top of one of his sections closely resemble 

pollen rain one would expect at the localities today, 

but near the base of two of his sections the abundance 

of spruce and fir (as n1uch as 25 percent of the total 

pollen) suggests a eli1nate cooler than the present. 

Whitehead and Barghoorn ( 1962) studied three 

other localities in Spartanburg County about 30 1niles 

due south of Leonards Cut. They found relatively 

little change within two sections and a pronounced 

shift from hemlock to pine in the third. Although the 

nearest spruce and fir trees are now frmn 30 to 45 

miles away, fossil spruce pollen con1prises as much as 

8 percent of the tree-pollen count, and fir pollen is 

present. Northern and montane elements recorded 

in all three sections (vVhitehead, 1963) strengthen the 

interpretation that these localities record a cli1nate 

somewhat cooler than now. 
D42 STRATIGRAPHY A~D STRUCTURAL GEOLOGY 

Frey (1953) found that pollen from Singletary Lake 

near the coast of North Carolina indicates a climate 

consistently cooler than the present from more than 

20,000 to about 10,000 years ago. 

The absence of relict Tertiary genera in the Leonards 

Cut material is indicative of Quaternary age. Frey 

(1953) has shown that cool, glacial climates during the 

Pleistocene extended as far south as the coastal plain 

of North Carolina. The similarity between the fossil 

pollen assemblages from Leonards Cut and modern 

assemblages in the same area shows, however, that the 

deposit is not glacial. The present elevation of the 

deposit above the modern master stream suggests that 

it is not Recent; it is therefore believed to be of interglacial or interstadial Pleistocene age. The surface of 

the Piedmont Upland in the Morganton basin is 

older than the Leonards Cut deposit and may be 

pre-Pleistocene. 

REFERENCES 

Cain, S. A., 1944, Pollen analysis of some buried soils, Spartanburg County, South Carolina: Torrey Bot. Club Bull., v. 71, 

p. 11-22. 

Eargle, D. H., 1940, The relations of soils and surface in the 

South Carolina Piedmont: Science, v. 91, p. 337-338. 

Frey, D. G., 1953, Regional aspects of the late-glacial and postglacial pollen succession of southeastern North Carolina: 

Ecol. Mon., v. 23, p. 289-313. 

Kerr, W. C., 1875, Report of the Geological Survey of North 

Carolina, v. 1, Physical geography, resume, economical 

geology: Raleigh, North Carolina, 325 p., map. 

Rubin, Meyer, and Alexander, Corrine, 1958, U.S. Geological 

Survey radiocarbon dates IV: Science, v. 127, p. 1476-1487. 

Suess, H. E., 1954, U.S. Geological Survey radiocarbon dates I: 

Science, v. 120, p. 467-473. 

Whitehead, D. R., 1963, "Northern" elements in the Pleistocene 

flora of the Southeast: Ecology, v. 44, p. 403-406. 

Whitehead, D. R., and ·Barghoorn, E. S., 1962, Pollen analytical 

investigations of Pleistocene deposits from western North 

Carolina: Ecol. Mon., v. 32, p. 347-369. 
Article 130 

SURFACE AND SUBSURFACE STRATIGRAPHIC SEQUENCE 

IN SOUTHEASTERN MISSISSIPPI 

By D. HOYE EARGLE, Austin, Tex. 

Work done on behalf of the Atomic Energy Commission 

Abstract.-The stratigraphic sequence in southeastern Mississippi includes outcropping units of Miocene to Recent age; 

many subsurface units of Tertiary, Cretaceous, and Jurassic age 

down to the Jurassic(?) salt; and possibly older sedimentary 

rocks that are underlain by the basement crystalline rocks. Two 

newly named units are described-the Tatum Limestone Member, a basal unit of the Catahoula Sandstone of Miocene and 

Oligocene(?) age; and the Andrew Formation of Early Cretaceous age. 

A detailed knowledge of the stratigraphic section of 

southeastern Mississippi was required for use in geologic 

and geophysical studies of the Tatum salt dome, Lamar 

County, Miss., for the U.S. Atomic Energy Commission. 

The deepest well in the southeastern Mississippi region 

penetrated only a few feet of bedded salt believed to be 

the Louann; consequently, the rocks below the salt are 

not known. Because detonations at the site, however, 

are expected to give geophysical data on rocks beneath 

the salt, the units that are found below the salt in 

adjoining areas are shown in the accompanying table. 

Subsurface sections were constructed radiating outward from the salt dome at least 25 n1iles in all directions 

in which veloeity surveys of wells were available. 

Study of the continuous-velocity logs of wells shows, as 

expected, a close correlation between lithology and zones 

of relatively uniform velocity characteristics. The 

zones c01npare closely with na1ned stratigraphic units. 

The stratigraphic nomenclature is here brought up to 

date and, for several units, names that more nearly 

conforrn to the rules of stratigraphic nomenclature are 

herein introduced. Son1e names in common usage have 

been adopted, and some lithologic names have been 

changed to indicate more specifically the lithology of 

the subsurface units. Type sections in wells are designated and briefly described. The accompanying table 

shows the names and stratigraphic relations of the 

units. 1 

As described by Matson (1916) the Citronelle Formation (Pliocene) (1, in table) is the sequence of sediments, 

chiefly nonmarine, above the Pascagoula Formation 

(Miocene) and below stream-terrace deposits. Its type 

locality at the town of Citronelle (Mobile County) in 

nearby southwestern Alabama includes (a) sand and 

gravel, considered to be Pleistocene in age (Roy, 1939; 

Carlston, 1951), that caps the uplands and lies unconformably on the deposits below, and (b) littoral, 

estuarine, and shallow marine deposits considered to 

be Pliocene in age (Berry, 1916; Stringfield and LaMoreaux, 1957). In Mississippi, only the sand and 

gravel deposits have been mapped as Citronelle, and 

they are considered by some geologists to be Pleistocene 

in age (Brown and others, 1944; Fisk, 1938; Doering, 

1956). More recently Brown is of the opinion that 

the Citronelle is Pliocene in age (written communication to G. V. Cohee, June 23, 1959). The Citronelle is 

several hundred feet thick along the coast of southeastern Mississippi and contains important aquifers. 

Inland it is thinner than along the coast and forms 

extens~ve upland plains and caps interstream divides. 

Remnants are found as far north as 140 miles from the 

Gulf of Mexico. 

1 Formal use of these names was considered at a conference in Jackson, Miss., on 

September 17, 1962, arranged by Esther R. Applin, of the U.S. Geological Survey, 

and attended by representatives of the U.S. Geological Survey, the Mississippi 

Geological Survey, the Mississippi Geological Society, and the Trowbridge Sample 

Service. Thicknesses given in the accompanying table were obtained from well logs 

of southeastern Mississippi and from data from Andrews (1960), Nunnally and Fowler 

(1954), Rainwater (1960, 1961), and Scott and others (1961). The author thanks his 

colleagues of the U.S. Geological Survey and Jules Braunstein, Shell Oil Co.; E. H. 

Rainwater, Shell Development Co.; and Eleanor Caldwell, Humble Oil and Refining 

Co.; for discussions and advice as to the use of these names. 

ART. 130 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D43-D48. 1964. 

716-626 Q--64----4 D43 
D44 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

The Pascagoula and Hattiesburg Formations (2) 

together form an indivisible stratigraphic unit. The 

Pascagoula Formation was described near the ~oast, 

along the Pascagoula River, where the beds are chiefly 

marine, and the Hattiesburg was described about 50 

miles or more inland at Hattiesburg, Miss., where the 

beds are less marine and consist in large part of sands 

that are important fresh-water aquifers. 

The Catahoula Sandstone is divided into an upper 

part, chiefly nonmarine sand and clay, and a lower part 

termed the Tatum Limestone Member (3), a new name 

introduced to replace "Limestone of the Heterostegina 

Surface and subsurface units in southeastern Mississippi and adjoining areas 

[Numbers in parentheses keyed to text discussion] 

--

Sys- Series Group Unit Approximate Lithologic character tern thickness (feet) 

-

l. C)~ Coastal terrace deposits 300± Silt, sand, gravel. C) ::>, ~ C) ~ .... C) 0 ce ce 0 C) ;:j ~ 

0' ;.§~ Gray to mottled red and orange silty clay, sand, 

-- P.,o (1) Citronelle Formation 150± gravel. ~ 

C) (2) Pascagoula and Hattiesburg 350-2, 300+ Greenish-gray silty clay, sand, and gravelly sand. ~ C) Formations, undifferentiated. 0 

0 

~ Upper part 250-700 Gray to olive sand, silt, and silty clay. 

't:1 

~_.....,_ 

ceQ./ White to gray sandy limestone and marl; glau- -$:1 cet.:- ;:jo 

0~ conitic calcarenite. 

;:-~ ~00 

ce't:l (3) Tatum '-'C) 

C)O ~$:1 Limestone 90-300 cece $:10 Uoo Member. C)b() 

O'"' 

o-

.... o 

:;g 

(4) Chickasawhay(?) Limestone 60-470 Gray to white sandy limestone and fossiliferous 

sandstone and clay. 

C) Bacatunna Clay Member of Calcareous clay. $:I Byram Formation. C) 

0 

0 

.~ Vicksburg Glendon Limestone Member of 50-215 White to gray sandy limestone and marl. 

0 Byram Formation and Mari- anna Limestone, undifferentiated. 

Red Bluff Clay 30± Gray, fine sand and clay interbedded, and soft 

fossiliferous limestone. 

Yazoo Clay 0-253 Olive to gray calcareous clay. 

::>, Jackson (5) Moodys Branch Limestone 30-300 White sandy limestone, fossiliferous glauconite, .... (Ocala Limestone to south) . and fossiliferous calcarenite. . ;s 

~ 

.... Cockfield Formation 25-215 Lignitic clay and fine sand. C) 

~ 

(6) Cook Mountain Limestone 115-235 Hard to soft white calcarenite (lime sand) and C) glauconitic, bentonitic clay. ~ C) 

0 

0 Claiborne (7) Sparta Sand and Zilpha 90-625 Gray shale and thin siltstone, interbedded. 

r£l Clay. 

(8) Winona Marl Glauconite, marl, green sand, and shale. 

90-200 

(9) Tallahatta Siltstone Hard gray siltstone, glauconite. 

Undivided (Salt Mountain LimeI 

2, 250-3, 200 Gray fine-grained sandstone and green to gray --?- (10) Wilcox stone equivalent near base). shale, interbedded. Q.i I Chalky white fossiliferous limestone. ~ C) 

0 

0 Porters Creek Clay 650-1,050 Gray shale. C) Midway ~ p., (11) Clayton Limestone 10-25 Limestone. 
EARGLE D45 

Surface and subs1trjace units in southeastern Mississippi and adjoining areas-Continued 

[Numbers in parentheses keyed to text discussion] 

Sys- Series Group 

I 

Unit tern 

rn (12) Selma Group and Eutaw Formation, un-

::::l differentiated. 0 

<l) 

Q 

~ 

-+" <l) Gordo Formation (upper Tus0 ""' caloosa of oil geologists). 

""' <l) (13) Coker Formation (includes 0.. 

0.. Tuscaloosa marine Tuscaloosa and lower p Tuscaloosa of oil geologists 

with "massive sand" at base). ----

(14) Dantzler Formation rn 

;:::l 

0 

<l) rn Q (15) Andrew Formation ~ ;:::l 

-+" 0 <l) <l) Paluxy Formation ""' Q 

0 ~ 

-+" 

<l) Mooringsport Formation .o ""' 

""' Ferry Lake Anhydrite <l) 

~ 0 

H Rodessa Formation, James Limestone, and Pine Island Shale, 

undifferentiated. 

----

<t!o Sligo Formation -Q ·a·;:< 

...c:::<l> 

g~ Hosston Formation 

Ot: 

(16) Cotton Valley Formation 

Q 

'iii .~ rn 

~ (17) Haynesville Formation (in- rn ""' eludes Buckner Member) rn 

~ ::::l 

""' ~ 

::l 

~ ""' <l) Smackover Formation 0.. 

0.. 

p 

Norphlet Formation 

~£ (18) Louann Salt ""' Q ::::l•..-< 

~rn Werner Formation 

,--.. 

I~ 

~ ; (19) Eagle Mills Formation (re0.. ...... stricted). 

s 

.c;: 

~';::' (20) Morehouse Formation rn .,.. 

a ·a <l) ~ 

P-4 > 

Pennsylvanian and older 

Precambrian Basement rocks 

zone" or "Heterostegina limestone." The following is a 

description of the Tatum Limestone Member. 

Type section.-U.S. Atomic Energy Commission hydrologic 

test well 1, Tatum dome area, Lamar County, Miss., is the type 

Approximate Lithologic character 

thickness (feet) 

925-1, 500 White chalk to gray marl, shale, and calcareous 

sandstone at base. 

300-900 Sandstone and gray shale. 

620-1, 160 Shale and some sandstone, mostly marine (ineludes thick sand, containing few shale lenses 

at base, and some gravel). 

575-1, 150 Red to gray mottled shale, buff, red, and green 

sandstone and siltstone. 

1,000-1,880 Limestone, sandstone, and gray to green shale. 

1,000-1,450 Sandstone and shale, buff, pink, white, micaceous. 

200-1,000 Marine shale, some sandstone. 

160-240 Anhydrite, shale, limestone. 

Limestone, shale, sandstone, anhydrite (hard 

750± calcareous sandstone, gray to red limy mica- ceous shale, oolitic to finely crystalline limestone.) 

300 Sandstone, shale, mudstone, reddish to greenish 

gray . 

1, 800-2, 650± Sandstone, red shale, conglomerate. 

2, 000-2, 900± Sandstone, shale, mudstone, red to purple, and 

green. 

Sandstone and red beds (Buckner Member contains salt in Alabama). 

1, 500-3, 450 ± Oolitic limestone. 

Sand and shale in Mississippi and Alabama, red 

shale and conglomerate in Arkansas and 

Louisiana. 

0-5, 000± White coarsely crystalline halite. 

200± Anhydrite, red shale, sandstone. 

Red beds, alluvial, continental flood-plain; some 

7, 000± gray and green beds, gray to white siltstones 

and sandstones, in association with diabase. 

Dark-gray shale. 

1, 200± 

Unknown. Sedimentary and metasedimentary rocks. 

Unknown Crystalline igneous and metamorphic rocks. 

I 

section. Well 1 is in the NEHSWH sec. 12, T. 2 N., R. 16 W., 

and the datum is 321 feet above sea level. Hydrologic test 

well 2 in the SWHSW?~ sec. 14, T. 2 N., R. 16 W., for which the 

datum is 302 feet, is a reference section. 
D46 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

Areal extent.-Southern Mississippi to northern Florida and 

the northern part of the Florida parishes of Louisiana. 

Thickness.-In well 1, 163 feet, from a depth of 1,373-1,536 

feet; in well 2, 170 feet, from 1,470-1,640 feet. The T:1tum 

thins to about 90 feet in the southeastern part of the area and 

thickens to 300 feet toward the west. 

Lithology.-Sandy limestone, marl, glauconitic calcarenite, and 

calcirudite (made up chiefly of fossil and limestone fragments). 

Electrical-log characteristics.-High resistivity; generally very 

low self-potential, which is characteristic of a fresh-water 

aquifer. 

Sonic-log characteristics.-High in sonic velocity. It is the 

first zone of high velocity found in drilling and in geophysical 

exploration of southern Mississippi. 

Paleontology.-Larger foraminifers are chiefly Heterostegina 

sp., Miogypsina sp., and Sorites sp. Many species of smaller 

Foraminifera have been identified from cores from well 1 by 

Ruth Todd and Doris Low. 

Age.-Miocene(?) and Oligocene(?). Larger foraminifers are 

said to be definitely Oligocene in age (Cole and Applin, 1961); 

smaller foraminifers suggest Miocene age (Ruth Todd and Doris 

Low, personal communication, 1962), although an Oligocene age 

is not necessarily precluded. The Tatum is tentatively correlated with fossiliferous limestones and marls of the Paynes 

Hammock Sand (Miocene) and the upper bed of the Chickasawhay Limestone (Oligocene) as described by MacNeil (1944). 

Chickasawhay Limestone (4) has been defined from 

surface outcrops only, and use of the name for a unit of 

the subsurface is questioned because exact correlation 

with surface outcrops is uncertain. 

Moodys Branch Lin1estone (5) is used in southeastern 

Mississippi instead of Moodys Branch Formation to 

indicate the characteristic subsurface lithology of the 

unit. The Ocala Limestone, in the southern part of 

the report area, as in western Florida and southern 

Alabama, is equivalent to the Moodys Branch Limestone and the Yazoo Clay farther updip. 

Cook Mountain Limestone (6) is used instead of 

Cook Mountain Forn1ation to indicate the characteristic subsurface lithology of the unit. It has been 

called the Camerina limestone by some geologists, but 

this genus is also present in other forn1ations. 

The terms Sparta Sand and Zilpha Clay (7) are used 

collectively in this article for the unit that underlies 

the Cook Mountain Limestone. "Upper part of Cane 

River equivalent" (of Louisiana) has been used for 

this unit in southwestern Mississippi. Some sandy 

beds in the middle of the chiefly clayey and silty unit 

are the downdip equivalents of the Sparta Sand. 

Winona Marl (8) is used for the green sand and shale 

and glauconitic 1narl whose equivalent is the Winona 

Sand of the outcrop. The tenn "Cane River Marl" 

(or, as used by some geologists, "Lower part of Cane 

River equivalent") is commonly used by oil geologists 

for this subsurface unit in southwestern Mississippi. 

Tallahatta Siltstone (9) is used in the report area 

instead of Tallahatta Formation to indicate 1nore 

definitely the characteristic subsurface lithology of 

the unit. 

Recent studies in Mississippi show that the different 

units in the Wilcox section (10) are closely correlative 

with the various formations of the Wilcox Group in 

Alabama. However, in this subsurface study, the 

Wilcox Group has not been subdivided. 

Clayton Limestone (11) is used instead of Clayton 

Formation of the outcrop to indicate the characteristic 

subsurface lithology of the unit. 

Some geologists consider that the shale and sandstone 

section below the chalk of the Selma Group and Eutaw 

Formation, undifferentiated (12), correlates with the 

basal part of outcropping Eutaw Formation equivalents 

in Arkansas. 

"Massive sand" (13) for the basal beds of the Upper 

Cretaceous is used informally (a formal name is not 

recommended) since the beds are not of uniform 

lithologic character and they vary in stratigraphic 

position. 

The Dantzler Formation (14) was originally described 

by Hazzard, Blanpied, and Spooner (1947). The following is a description of the formation. 

Type section.-Humble Oil and Refining Co. No. B-1 Dantzler 

Lumber Co. well, Jackson County, Miss. The well is in sec. 

30, T. 5 S., R. 8 W., and the derrick floor elevation is 108 feet 

above sea level (datum, 1 foot above rotary, or about 110 feet). 

Depth 8,905-9,910 feet (Nunnally and Fowler, 1954, p. 25). 

Areal extent and thickness.-Southeastern Mississippi, extending into the southwest corner of Alabama; 1,200 feet thick 

(Nunnally and Fowler, 1954, p. 28) but thins rapidly to the 

west. Western limit, Franklin and Amite Counties; northern 

limit, from northern boundaries of Lincoln and Covington 

Counties southeast to Greene County. Beyond these limits the 

formation cannot be distinguished from the underlying Andrew 

Formation. 

Lithology.-Nonmarine sands, fine- to medium-grained, white 

to dull-red, and green; shales, dark-purplish-red, generally 

mottled with white, yellow, ochre, and gray; some shales are 

dark gray; some are micaceous, slightly chloritic, silty. Some 

beds are carbonaceous and lignitic, others are calcareous and 

contain gray, red, or white limestone nodules 

Electrical-log characteristics.-Generally lower resistivity and 

self-potential than beds above and below. 

Sonic-log characteristics.-Generally lower sonic velocity than 

beds above and below. 

Paleontology.-F. W. Rolshausen, of the Humble Oil and 

Refining Co., has found oyster shells, ostracods, and Chara in 

some cores from the type well, and one specimen of Haplophragmoides in one core from a depth of 9, 779-9,789 feet. 

Age.-May include beds of Cenomanian age at top, as originally correlated by Hazzard, Blanpied, and Spooner, but is 

unconformably overlain by beds of known Cenomanian age, the 

Tuscaloosa Group. 

The Andrew Formation (15) is here named and 

described as generally marine rocks previously called 

"Pre-Dantzler rocks of Washita and Fredericksburg 

Groups, undifferentiated" (Nunnally and Fowler, 1954, 
EARGLE D47 

p. 22-25). The following is a description of the Andrew 

Formation. 

Type section.-Gulf Oil Co. No. 25 J. M. Andrew well, sec. 6, 

T. 1 N., R. 16 W., Baxterville oil field, Lamar County, Miss. 

Elevation of the derrick floor is 233 feet above sea level (datum is 

1 foot above rotary, about 2 feet above derrick floor, or about 

235 feet). Cuttings and cores were examined by Esther R. 

Applin (written communication, October 1962), who found that 

the formation extends in depth from 9,800 feet (electrical-log 

point, or the 9,810--9,820-foot sample) to 11,360 feet (electricallog point, or the 11 ,38Q--11 ,390-foot sample). 

Areal extent and thickness.-Across southern Mississippi and 

into adjoining States. Northern limit is defined by a change in 

facies to nonmarine sands and shales whose lithology is similar 

to overlying and underlying formations. Northern limit of 

recognizable Andrew Formation extends from Claiborne County 

on the northwest to southeastern Greene County on the southeast (Nunnally and Fowler, 1954). 

Lithology.~According to Mrs. Applin's sample and core 

descriptions the Andrew Formation consists, toward the top, of 

dull- to dark-red, gray, and olive-gray shale containing beds of 

brownish-gray finely sandy limestone, some shell fragments, and 

some beds of olive-gray dolomite and light-cream limestone. 

This grades down into gray and greenish-gray to dull-red micaceous shale alternating with limestone, minor beds of fine-grained 

sandstone containing some carbonaceous matter, and grayishgreen siltstone. Much of the lower part is dark-gray shale. 

Electrical-log characteristics.-Generally low self-potential and 

alternating zones of moderately high and low resistivity. 

Sonic-log characteristics.-Generally high sonic velocity, but 

thin zones of strongly contrasting velocities. 

Paleontology.-According to Mrs. Applin, the upper part of 

the Andrew Formation contains abundant bivalves and ostracods. 

A few specimens of Lituola injlata were found in samples from 

depths of 10,280-·10,300 and 10,360--10,370 feet. Ostrea fragments were common throughout the section; ostracods were 

abundant and scattered throughout. Quinqueloculina and other 

Miliolids were found at 10,596--10,601 and at 10,626--10,628% 

feet. Plicatula- and Pecten-like pelycypods were found at 

10,611--10,616 feet. 

Age.-The formation has been correlated with the lower part 

of the Washita and Fredericksburg Groups of Texas. Exact 

correlations on the basis of diagnostic faunas, however, are 

unknown to the author. 

Cotton Valley Formation (16) is used instead of 

Cotton Valley Group because the formations making 

up the group in other States have not been differentiated in southeastern Mississippi. 

Haynesville Formation (17) includes the Buckner 

Member in the subsurface of southestern Mississippi. 

The Buckner is believed to include some salt beds in 

Alabama. 

The Louann Salt (18) (greatly contorted) has been 

intruded as diapirs into overlying sediments. One 

well in the report area is reported to have penetrated 

the bedded Louann Salt. Applin and Applin (1953) 

state that a core composed of 1 foot of anhydrite and 1 

foot of rock salt was recovered in a basket core barrel 

from the lowermost 9-foot interval of George V asen 

fee well No. 1, Stone County, Miss., drilled to a depth 

of 20,450 feet. The units listed here as occurring 

below the Louann have not been drilled in southeastern 

Mississippi and are, therefore, not known to be present 

there. They have been found, however, in one or 

more States adjoining Mississippi, where the salt 

occurs at shallower depths. 

The Eagle Mills (1 9) was originally described 

(Imlay, 1940) to include beds now included in the 

Norphlet, Louann, Werner, and the Eagle Mills, 

restricted. The exact age of this sequence is unknown, 

but has been considered by various authors as Permian(?), Triassic(?), or Jurassic(?). Scott, Hayes, and 

Fietz (1961) tentatively include the Eagle Mills in the 

Triassic, partly on the basis of identification by Erling 

Dorf of a plant fossil that is similar to one of the Chinle 

Formation of Arizona and the Newark Group of 

Virginia, and partly on lithologic similarities to the 

Newark Group. 

The structural and stratigraphic relations of the 

Morehouse Formation (20) to the Eagle Mills Formation, restricted, are not known. 

REFERENCES 

Andrews, D. I., 1960, The Louann salt and its relationship to 

Gulf Coast salt domes: Gulf Coast Assoc. Geol. Societies 

Trans., v. 10, p. 215--240. 

Applin, P. L., and Applin, E. R., 1953, The cored section in 

George Vasen's fee well 1, Stone County, Mississippi: U.S. 

Geol. Survey Circ. 298, 29 p. 

Berry, E. W., 1916, The flora of the Citronelle Formation: U.S. 

Geol. Survey Prof. Paper 98--L, p. 193--208. 

Brown, G. F., and others, 1944, Geology and ground-water resources of the coastal area in Mississippi: Mississippi Geol. 

Survey Bull. 60, 232 p. 

Carlston, C. W., 1951, Profile sections in Citronelle Formation in 

southwestern Alabama: Am. Assoc. Petroleum Geologists 

Bull., v. 35, no. 8, p. 1888--1892. 

Cole, W. S., and Applin, E. R., 1961, Stratigraphic and geographic distribution of larger Foraminifera occurring in a 

well in Coffee County, Georgia, in Contributions from the 

Cushman Foundation for Foraminiferal Research, v. 12, 

pt. 4: p. 127--135. 

Doering, J. A., 1956, Review of Quaternary surface formations 

of Gulf Coast region: Am. Assoc. Petroleum Geologists 

Bull., v. 40, no. 8, p. 1816--1862 

Fisk, H. N., 1938, Geology of Grant and LaSalle Parishes: 

Louisiana Dept. Conserv., Geol. Bull. 10, 246 p. 

Hazzard, R. T., Blanpied, B. W., and Spooner, W. C., 1947, 

Notes on correlation of the Cretaceous of east Texas, south 

Arkansas, north Louisiana, Mississippi, and Alabama: 

Shreveport Geol. Soc. 1945 Reference Rept., v. 2, p. 472--

481. 

Imlay, R. W., 1940, Lower Cretaceous and Jurassic Formations 

of southern Arkansas and their oil and gas possibilities: 

Arkansas Geol. S~rvey Inf. Circ. 12. 

MacNeil, F. S., 1944, Oligocene stratigraphy of southeastern 

United States: Am. Assoc. Petroleum Geologists Bull., v. 

28, no. 9, p. 1313-1354. 
D48 STRATIGRAPHY AND STRUCTURAL GEOLOGY 

Matson, G. C., 1916, The Pliocene Citronelle Formation of the 

Gulf Coastal Plain: U.S. Geol. Survey Prof. Paper 98, p. 

167-192. 

Nunnally, J. D., and Fowler, H D., 1954, Lower Cretaceous 

stratigraphy of Mississippi: Mississippi Geol. Survey Bull. 

79, 45 p. 

Rainwater, E. H., 1960, Stratigraphy and its role in the future 

exploration for oil and gas in the Gulf Coast: Gulf Coast 

Assoc. Geol. Societies Trans., v.' 10, p. 33-75. 

Rainwater, E. H., 1961, Outline of geological history of Mississippi: Gulf Coast Assoc. Geol. Societies Trans., v. 11, p. 43-45. 

Roy, C. J., 1939, Type locality of Citronelle Formation, Citronelle, Alabama: Am. Assoc. Petroleum Geologists Bull., v. 

23, no. 10, p. 1553-1559. 

Scott, K. R., Hayes, W. E. and Fietz, R. P., 1961, Geology of 

the Eagle Mills Formation: Gulf Coast Assoc. Geol. 

Societies Trans., v. 11, p. 1-14. 

Stringfield, V. T., and LaMoreaux, P. E., 1957, Age of Citronelle Formation in Gulf Coastal Plain: Am. Assoc. Petroleum Geologists Bull., v. 41, no. 4, p. 742-746. 
Article 131 

MAGMATIC DIFFERENTIATION IN A VOLCANIC SEQUENCE 

RELATED TO THE CREEDE CALDERA, COLORADO 

By JAMES C. RATTE and THOMAS A. STEVEN, Denver, Colo. 

Work done in cooperation with the Colorado State Metal Mining Fund Board 

Abstract.-Arranged in order of age, the ash-flow sheets and 

interlayered lava flows related in origin to the Creede caldera 

display progressive changes in (a) the abundance and composition 

of phenocrysts, (b) chemical composition, and (c) mode of eruption. These changes are evidence of continuing differentiation 

of the source magma. 

A complex pile of welded ash-flow tuffs, lava flows, 

and intrusive .rocks surrounds the Creede caldera, a 

nearly circular subsidence structure 10 to 12 miles in 

diameter in the central San Juan Mountains, Colo. 

The volcanic rocks were in part derived from a source 

area in the vicinity of the caldera and in part from 

other sources. Those from the caldera source area 

comprise 5 ash-flow units (terminology of Smith, 1960; 

Ross and Smith, 1961) and 3 lava-flow units. These 

units are listed according to order of eruption in figure 

131.1, which also lists formational names defined by 

the authors in another article (Art. 132). When 

considered in order of age, the volcanic units show an 

irregular progression from early phenocryst-poor rhyolites to later phenocryst-rich quartz latites. Parallel 

with these changes in composition, the mode of erupQi~ 

Composition of phenocrysts Ul 

Q) 

"'OC Volume "'0 

.... 0 (order of 0 

0:;; E 

Formation cc. magnitude Abundance of phenocrysts (percent) Q) Q) ..... ::.2 in cubic Ul 2 Q) 0 0 

+'Q) ro Q) .... u -~ :;; c .D Q) ·c\f- kilometers) N 2 Q) Q) 

::lo 0 3:! t c X .J::. .D 

"iiO c ro :;; tiD 0 c. E 

0 10 20 30 40 ro ro ::J .Q ro >- E ::J 50 60 70 a: (/) 0 a:l ::2: a.. <( z ---,. T T 

F isher Quartz 8 10-100 M 0-m O-m m-M m 0-M 0-M 17 Latite Lava flows 

Snow shoe Mountain 7 100-1000 M m m M m m 0-m 26 

Q uartz Latite Ash flows 

Lava flows 6 1-10 M 0 0 m-M m 0-M 0 6 

Lava flows 

Wason Park 5 100-1000 M M 0 m m 0 0 29 

Rhyolite Ash flows 

Lava flows 4 1-10 M 0 0 m-M m m-M 0 27 

} 100-1000 

Lava flows 

1moth Mountain 3b M m-0 0 M m 0-m 0 53 

Rhyolite { ,...._.. Ash flows (phenoc.ysH;ch) 1moth Mountain 3a M M 0 m m 0 0 13 

Rhyolite Ash flows (phenocryst -poor) 

Marr 

Marr 

Fa • rmers Creek 2 10-100 1--+--1 M M 0 m m 0 0 12 

Rhyolite Ash flows 

Bac :helor Mountain 1 10-1000 1-+-i M M 0 m m 0 0 12 

Rhyolite Ash flows 

FIGURE 131.1.-Abundance and composition of phenocrysts in the volcanic sequence related to the Creede 

caldera source area. These rocks have porosity ranging generally from 2 to 10 percent; thus compaction 

effects are negligible for purposes of comparison of abundance of phenocrysts. Lines represent range 

of abundance; dots, average abundance; M, generally greater than 10 percent of total phenocrysts; m, 

generally less than 10 percent of total phenocrysts; 0, phenocrysts not observed, or present only in 

trace amounts. 

ART. 131 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D49-D53. 1964. 

D49 
D50 MITNERALOGY AND PETROLOGY 

tion changed from predominantly ash-flow eruption 

through alternating ash-flow and lava-flow eruptions to 

a final predominance of lava-flow eruptions. We interpret these changes as evidence of differentiation in the 

source magma chamber throughout the general period 

of eruptivity. Progressive changes in the Mammoth 

Mountain Rhyolite, a single ash-flow sheet, illustrate the 

stratified nature of the magma in the chamber during a 

particular eruptive stage. We shall first discuss the 

evidence from the entire sequence of flows, and then the 

details displayed by the Mammoth Mountain. 

DIFFERENTIATION EXHIBITED BY FLOW 'SEQUENCE 

The early phenocryst-poor rhyolites consist of ash 

flows of the Bachelor Mountain Rhyolite, Farmers 

Creek Rhyolite, and the older ash flows of the Mammoth Mountain Rhyolite. The phenocryst content of 

these ash flows ranges from about 2 to 12 percent. The 

phenocrysts are predominantly sodic plagioclase and 

sanidine in nearly equal amounts and some biotite 

and magnetite. The younger ash flows of the Mammoth Mountain Rhyolite range in composition from 

rhyolitic quartz latite to quartz latite and contain 

15 to nearly 60 percent phenocrysts. With the change to 

quartz latite, sanidine decreases relative to plagioclase, 

and mafic phenocrysts become more abundant. 

Beginning with the Mammoth Mountain, lava flows 

are interlayered with the ash flows and become more 

abundant upward. Near the top of the sequence, 

the ratio of ash flows to lava flows is about 1:10. The 

bulk of the lava flows are quartz latites with an average 

of 30 to 40 percent phenocrysts, predon1inantly 

plagioclase of intermediate con1position, although 

mafic minerals, including biotite, magnetite, pyroxene, 

and hornblende are abundant. Sanidine and quartz 

are present in some flows of the Fisher Quartz Latite 

which range in composition from rhyolite to rhyodacite. 

The two ash-flow units in the upper part of the 

sequence, the Wason Park Rhyolite and the Snowshoe 

Mountain Quartz Latite, range in . eomposition from 

rhyolite to quartz latite and are rich in phenoerysts. 

The Wason Park eontains about 30 pereent phenoerysts, 

mainly plagioclase and sanidine with son1e biotite, 

n1agnetite, and a traee of pyroxene, and is definitely 

less 1nafie than the ash flows of the underlying Mammoth Mountain. The Snowshoe Mountain, the uppernlOst ash-flow unit, eontains 30 to 60 pereent phenoerysts; plagioclase is dominant, but 1nafie crystals--

biotite, magnetite, pyroxene, and amphibole--are 

more abundant than in any of the earlier ash-flow 

units. Sanidine and quartz also are present in small 

amounts. 

The mineralogic. ehanges outlined above express 

progressive ehanges in ehemical eomposition. Analyses 

of samples praetieally free from alteration effeets, 

other than hydration of the glass of vitrophyres, are 

given in table 131.1. The changes in composition with 

time, or with the position in the sequenee, are shown 

graphieally in figure 131.2 by plotting the differentiation index (D.I.) of Thornton and Tuttle (1960) 

against siliea in the various roek units. The D .I. is 

simply the sum of normative quartz, orthoclase, and 

albite, and is deseribed by Thornton and Tuttle as 

a measure of the basieity of a roek and as an indication 

of the position of a roek along the path toward 

petrogeny's residua system (Bowen, 1937). 

The ehemieal analyses (table 131.1) and the differentiation diagram (fig. 131.2) indieate that: (a) the 

younger units of the sequenee are generally more mafie 

in eomposition than older units; (b) the ash flows and 

lava flows, eonsidered as separate series, show a similar 

trend toward more mafie roeks in the younger units; 

(c) the lava-flow series (units 4, 6, and 8) is slightly 

out of step with the ash-flow series, as each lava-flow 

unit is more mafic than the ash-flow unit that follows 

in the order of eruption; (d) the Wason Park Rhyolite 

(unit 5) plots out of the order of eruption in the ashflow series on the differentiation diagram because these 

ash flows are considerably more rhyolitic than the lava 

flows (unit 4) and phenocryst-rich Mammoth Mountain ash flows (unit 3b) that precede the Wason Park. 

COMP'OSITIONAL STRATIFICATION IN THE MAMMOTH 

MOUNTAIN RHYOLITE 

The Mammoth Mountain Rhyolite is a thick composite ash-flow sheet representing many successive 

ash flows. It is exposed for at least 300° around the 

margin of the Creede ealdera, and it ranges in thickness 

from 0, where it wedges out against a local high in the 

underlying topography northwest of Creede, to about 

1, 700 feet on the north side of the caldera. Although 

the full extent of the sheet is incompletely known, 

its original volume was well in excess of 100 cubic 

kilometers. 

The composite sheet changes laterally from a simple 

cooling unit, near its probable source within the 

caldera, through a compound cooling unit, to separate 

cooling units farther from the source. The successive ash flows of the Mammoth Mountain Rhyolite 

were not all coextensive; early ash flows were confined 

by an irregular topography and had a 1nore limited 

distribution than s0111e of the late:r: ash flows. Several representative seetions of the ash-flow sheet are 

located by letters on figure 131.3, and approximate 

thicknesses of the sheet are given in parentheses. 

The formation is exposed ahnost continuously east of 

the ealdera between sections A and F, but the area 

near Rat Creek and Miners Creek stood high when 
RATTE AND STEVEN D51 

TABLE 131.1.-Chemical analyses and differentiation index of volcanic rocks in the sequence related to the Creede caldera source area 

Units (in order of eruption) 

Formation__________ Bachelor 

Mountain 

Rhyolite 

Description _________ Ash flow 

Field No ___________ _ 

Laboratory No _____ _ 

Chemical constitu- ents: 

(vitrophyre) 

C-769 

153631 

2 

Farmers 

Creek 

Rhyloite 

Ash flow 

(vitrophyre) 

R-40 

154777 

Si02------------- 71.7 72.5 

Ah03----------- 13.0 13.7 Fe203. __________ . 8 . 6 FeO_____________ . 85 . 52 

Mg ___ ---------- . 22 .11 cao_ ___________ . 78 . 67 

Na20 .. --------- 3. 4 3.6 

K20_____________ 4. 7 5.1 

H20+----------- 4. 0 3.1 H20-___________ . 37 .1 

Ti02------------ .19 .18 

P20s. ----------- . 00 . 02 

MnO __ --------- .11 . 08 

C02------------- <. 05 <. 05 CL ________ ----- ___ -------- _____________________ _ 

F --------------- ---------------- ---------------- D. J.1 (ash 91. 8 93. 7 flows) 

D. J.1 (lava 

3a 

Mammoth 

Mountain 

Rhyolite 

Ash flow 

(phenocryst poor) 

C-985b 

C-1164 

72.69 

13.85 

1. 51 

.18 

.40 

.89 

3.11 

5.46 

.49 

. 70 

.25 

.05 

.04 

.00 

.03 

. 05 

91 

3b 

Mammoth 

Mountain 

Rhyolite 

Ash flow 

(phenocryst rich) 

C-539a 

151484 

67.2 

16.8 

2. 2 

. 32 

.66 

2.2 

4. 0 5. 0 

1.3 

.54 

.38 

.10 

.05 

<.05 

79.8 

flows) _________ ---------------- ---------------- ---------------- ---------------- Analysts and date P. L. D. El- P. L. D. El- D. Taylor, P. L. D. Elofanalysis more, I. H. more, I. H. G. H. Neu- more, S.D. 

Barlow, S. Barlow, S. erburg; 1957 Botts, M. D. Botts; D. Botts, D. Mack; 

1958 G. Chloe; 1957 

1959 

1 Differentiation index (Thornton and Tuttle, 1960). 

90 80 70 

DIFFERENTIATION INDEX 

(normative Q+Or+Ab) 

60 50 

FIGURE 131.2.-Differentiation diagram, showing differentiation index versus silica in the volcanic se- quence derived from the Creede caldera source area. Numbers refer to units listed in table 131.1, and 

indicate order of eruption. Dots represent ash flows, 

and X 's lava flows. 

4 

Lava flows 

Lava flow 

(Larsen, 

1956, table 

23, No.l4, 

p.190) 

Lag 1598 

65.29 

15.56 

4.13 

. 55 

. 78 3. 41 3.66 

4. 61 

.94 

.60 

.85 

.26 

77.4 

J. G. Fairchild; 1925 

Wason Park 

Rhyolite 

Ash flow 

(vitrophyre) 

C-341b 

D-1423 

69.24 

13.96 

1.15 

. 72 

.49 

1.18 

3.19 

6. 06 2. 65 

. 27 

. 35 

. 07 

. 08 

. 04 

.12 

. 05 

87 

M. Seerveld; 

1957 

Lava flows 

Lava flow 

(Larsen, 

1956, table 

23, No.6, 

p.190) 

Lag 1027 

60.54 

16.01 

3.63 

2. 34 

2.49 

5.44 

3.69 

3.80 

1. 07 

. 23 

1.10 

. 51 

66.3 R. E. Bailey; 

1923. Alkalies by F. A. Gonyer; 

1942 

107°00' 

37° 

45' 

@ 

(1600) 

CREEDE 

0 

7 

Snowshoe 

Mountain 

Quartz Latite 

Ash flows 

(average of 3, 

with range) 

S-54-13; S-56A; 

S-56B 

D-1422; 153105; 

153106 

62. 9 (61. 7-66. 0) 

15. 9 (15. 4-16. 5) 3. 4 (2. 6--4. 6) 

1. 7 (1. 0-2. 2) 1. 5 (1. 3-1. 8) 

4. 0 (3. 2-4. 6) 

3. 6 (3. 5-3. 6) 

3. 9 (3. 6-4. 3) 

}1.1 (. 88-1. 42) 

. 59 (. 54-. 68) 

. 25 (. 22-. 29) . 11 (. 09-. 14) 

(. 04-1. 4) 

8 

Fisher Quartz 

Latite. 

Lava flow 

(vitrophyre). 

R-284 

153630 

60.0 

15.5 

3. 6 2.8 

3. 0 5.1 

3.6 

2. 6 2.1 

.25 

. 78 

.25 

.16 

<.05 

72.9 (69-76. 8 ) ----------------

S.D. Botts, 

H. H. 

Thomas, M. D. Mack; 

1958 

62.4 

P.L.D.Elmore, I. H. 

Barlow, S. D. Botts; 

1958. 

®(1000) 

5 MILES 

FIGURE 131.3.-Location map for representative sections (letters 

in circles) of Mammoth Mountain Rhyolite. Thickness of 

sections, in feet, shown in pa.rentheses. 
D52 MLNERALOGY AND PETROLOGY 

TABLE 131.2.-Modes of Mammoth Mountain Rhyolite 

Rock constituents (percent) 

NumRepresentative Description ber of Total pheno- Sanidine Plagioclase section (fig. 131.3) modes crysts Biotite Magnetite Pyroxene Amphibole 

(avg) (avg) (avg) (avg) 

Avg Range Avg Range Avg Range 

A, B, C _____ Phenocryst poor _______ 13 8 5-11 3 2-4 4 2-5 <1 <1 Tr. Tr. 

B ___________ Phenocryst rich _______ 4 27 16-33 10 6-12 14 8-18 2 1 Tr. <1 D __________ Phenocryst rich _______ 2 27 26-28 <1 o-Tr. 21 20-22 3% 1 1 Tr. 

E ___________ Phenocryst rich _______ 41 43 39-53 Tr. -------- 34 25-44 5 2 1 Tr. 

G __________ Phenocryst rich _______ 6 39 18-58 3~~ Tr-6 29 11-45 3% 2 Tr. Tr. 

these ash flo.ws were deposited, and sections G and H 

are not continuous with the sections to the east. 

The abundance and modal composition of phenocrysts in the Mammoth Mountain Rhyolite change 

ooth vertically and laterally, and no one section shows 

the full range of either (table 131.2). The rhyolite 

near sections A and B, north of the caldera (fig. 131.3), 

is poorest in phenocrysts. At section A, the rock 

contains less than 10 percent phenocrysts, and at section B, the lower 1,000 feet contains less than 10 percent 

phenocrysts, but grades upward into rock that contains 

15 to 30 percent phenocrysts. Phenocryst-rich rocks 

become more abundant southeastward frmu sections 

A and B; they constitute all but the basal few feet of 

section C, and all of sections D, E, and F. Sections G 

and H have a wide range in phenocryst content; 

welded tuff near section G contains 18 to 58 percent 

phenocrysts, and rocks with relatively few phenocrysts 

predominate in the lower part of the section. 

In general, the change from early phenocryst-poor 

rocks to later phenocryst-rich rocks in the Ma1nn1oth 

Mountain ash-flow sheet is paralleled by a change 

from rhyolitic composition to one progressively more 

quartz latitic, as indicated by phenocryst modes 

(table 131.2) and by chemical analyses (table 131.1, 

units 3a and 3b). Where phenocrysts are scarce, as 

in sections A and B, they are :~;nainly sanidine and sodic 

to intermediate plagioclase in nearly equal proportions, 

and sparse mafic minerals. Where they are abundant, 

as in sections D, E, and F, plagioclase predominates 

over sanidine, and mafic minerals including green 

pyroxene are more abundant. 

Chemical analyses of samples of Mammoth Mountain 

Rhyolite from section B (fig. 131.3) indicate that the 

change from phenocryst-poor rocks in the lower part 

of the section (table 131.1, unit 3a) to phenocryst-rich 

rocks above (table 131.1, unit 3b) is accompanied by 

significant decreases in silica and by notable increases 

in Al203, MgO, and CaO. The ratio K20:Na20 decreases from 1.76 in the lower part of the section to 1.14 

above. Chemical analyses of Mammoth Mountain 

Rhyolite from other sections were made only for K20 

and N a20 content. Changes in composition laterally in 

the ash-flow sheet are shown by comparing K20:N a20 

ratios at the different sections (table 131.3). 

TABLE 131.3-K20 and Na20 in the Mammoth Mountain Rhyolite 

[Analysts: Wayne Mountjoy and George T. Burrow, 1959-60] 

Repre- Num- K20 1 (weight Na20 1 (weight Aversentative ber of percent) percent) age 

section Description anal- ---------ratio of 

(fig. 131.3) yses K20: 

Avg Range Avg Range Na20 

----- ---- ------ A,B _______ Phenocryst poor __ 4 5.1 4. 65-5.50 3.1 2. 90--3.24 1. 65 c __________ Phenocryst poor __ 3 5. 5 5. 41-5.65 3.2 3.10-3.34 1. 73 D __________ Phenocryst rich ___ 2 4.5 4. 21-4.83 3. 9 3. 90--3. 96 1.15 E __________ Phenocryst rich ___ 3 4.2 4.05-4.31 3.9 3. 81-3.91 1.08 G __________ Phenocryst rich ___ 6 4.6 4.15-5.05 3. 7 3 .. 50-3. 92 1. 22 

1 Analyses by flame photometric methods. 

The volcanic rocks from the Creede caldera source 

area fonn a genetic sequence that represents the crystallization and differentiation of a magma that lay beneath the area. We can only speculate on the processes of differentiation that were operative, but whether 

they were gaseous transfer of alkalies, crystal setting, 

filter pressing, or son1e other process, we believe it evident that the magma had a layered aspect. The early 

phenocryst-poor rhyolitic ash flows were erupted from 

a differentiated magn1atic "crean1" rich in alkalies, 

silica, and volatiles at the top of the 1nagma. Later 

phenocryst-rich rhyolitic to quartz latitic rocks show 

progressive changes in the composition of the n1ag1na. 

Changes in phenocryst content and chemical composition within the Ma1nmoth Mountain Rhyolite indicate 

that successively deeper levels of a layered mag1na were 

tapped during the eruption of this single ash-flow sheet. 

In addition, the change in the type of eruptive activity 

from d01ninant ash-flow eruptions to alternating ashflow and lava-flow eruptions is in accord with loss of 

alkalies and the effective de,Tolatilization of the 1nagn1a 

during the sequence of eruptions. Eruptive cycles are 

suggested by alternating ash-flow and lava-flow pairs 

(units 3 and 4, 5 and 6, 7 and 8, table 131.1), and 

temporary reversals in compositional trends may be 

explained if a relatively silicic fraction were generated 
RATTE AND STEVEN D53 

in the upper part of the magma during periods of 

quiescence in the eruptive history. 

The geologie importance of recording changes in 

physical character and chemical composition in successive ash flows from a common source was recognized by 

Smith (1960, p. 833), who also suggested that changes 

in the abundance of phenocrysts (crystal :glass ratio) 

and changes in magma chemistry 1nay be recorded in 

single compound cooling units. Roberts and Peterson 

(1961) observed that welded "ash" tuffs (phenocrystpoor rocks) in the Great Basin province are more rhyolitic and have higher differentiation indices than welded 

"crystal" tuffs (phenocryst-rich rocks). On the basis 

of these data, they discussed possible relationships between magma composition, eruptive activity, and 

phenocryst content of ash flows that are similar in 

many respects to the conclusions reached in this article. 

REFERENCES 

Bowen, N. L., 1937, Recent high-temperature research on silicates and its significance in igneous geology: Am. Jour. Sci., 

v. 33, p. 1-21. 

Larsen, E. S., Jr., and Cross, Whitman, 1956, Geology and 

petrology of the San Juan region, southwestern Colorado: 

U.S. Geol. Survey Prof. Paper 258, 301 p. 

Roberts, R. J., and Peterson, D. W., 1961, Suggested magmatic 

differences between welded "ash" tuffs and welded crystal 

tuffs, Arizona and Nevada: Art. 320 in U.S. Geol. Survey 

Prof. Paper 424-D, p. D73-D79. 

Ross, C. S., and Smith, R. L., 1961, Ash-flow tuffs: their origin, 

geologic relations and identification: U.S. Geol. Survey Prof. 

Paper 366. 

Smith, R. L., 1960, Ash flows: Geol. Soc. America Bull., v. 71, 

no. 6, p. 795-842. 

Thornton, C. P., and Tuttle, 0. F., 1960, Chemistry of igneous 

rocks; differentiation index: Am. Jour. Sci., v. 258, p. 664-

684. 
Artide 132 

REVISED TERTIARY VOLCANIC SEQUENCE 

IN THE CENTRAL SAN JUAN MOUNTAINS, COLORADO 

By THOMAS A. STEVEN and JAMES C. RATTE, Denver, Colo. 

Work done in cooperation with the Colorado State Metal Mining Fund Board 

Abstract.-Rock units record a complex sequence of volcanic 

events in which eruptions were in part concurrent and in part 

sequential, and many of the larger pyroclastic eruptions culminated in cauldron subsidence. The previously used volcanic 

sequence in the area is inadequate to explain the geology; several older stratigraphic names are not used in the report area, 

others are redefined, and new names are given to many of the 

rock units. 

Most of the rock units in the central San Juan Mountains, southwestern Colorado, have been described 

previously as belonging to a sequence of six formations 

1n the Potosi Volcanic Series (Larsen and Cross, 1956, 

p. 90-167); rocks exposed within the area discussed here 

were assigned largely to the upper three of these units, 

the Alboroto Rhyolite, Huerto Quartz Latite, and 

Piedra Rhyolite (table 132.1). The Creede Formation 

and Fisher Quartz Latite were believed by Larsen and 

Cross (1956, p. 168, 172) to have accumulated after the 

Potosi Volcanic Series, and to be separated from the 

older rocks and from each other by unconformities representing deep erosion and significant periods of time. 

The Potosi units were believed to have wide lateral 

extent, and correlations were made principally on 

topographic position and rock type. 

In contrast, our investigations, covering several hundred square miles in the vicinity of Creede, Colo., 

(fig. 132.1), have shown that the rock units record a 

complex sequence of volcanic events in which eruptions from local centers were in part concurrent and 

in part sequential, and in which many of the larger 

TABLE 132.1.-Comparison of stratigraphic names used for volcanic units in the central San Juan Mountains 

Rock units interpreted by Larsen and Cross (1956) 

Fisher quartz latite __________________ _ Creede formation ____________________ _ Potosi volcanic series _________________ _ Piedra rhyolite ____________________ _ 

Rhyolitic ~atite member __________ _ 

Tuff member ____________________ _ Local dark quartz latite __________ _ 

Tridymite rhyolitic latite member __ _ Lower rhyolite member ___________ _ 

Rock units interpreted by Emmons and Larsen (1923) 

Fisher quartz latite_-------------------

Creede formation ___ ------------------- Potosi volcanic series _________________ _ Piedra group _________________________ _ 

Nelson Mountain quartz latite _________ _ Rat Creek quartz latite _________ ,.. _____ _ 

Quartz latite tuff ____ ------------------ Andesite _________ - ____ - - - - - - - - - - - - - - - Tridymite latite ___________ ------------ Windy Gulch rhyolite breccia, rhyolite 

tuff, hornblende quartz latite, Mammoth Mountain rhyolite. 

Huerto quartz latite _________________ (Believed absent) ____________________ _ Alboroto rhyolite___________________ Alboroto group _______________________ _ Upper rhyolitic latite member_ _____ Equity quartz latite __________________ _ Phoenix Park quartz latite _____________ _ 

Lower rhyolite member____________ Intrusive rhyolite, Campbell Mountain 

rhyolite, Willow Creek rhyolite, Outlet 

Tunnel quartz latite. 

Correlative units used in this article (see table 132.2 for correct startigrapbic sequence) 

Fisher Quartz Latite. 

Creede Formation. 

(Not used in report area.) 

(Not used in report area.) 

Nelson Mountain Quartz Latite. 

Rat Creek Quartz Latite. 

Rat Creek Quartz Latite. 

Huerto Formation. 

Wason Park Rhyolite. 

Farmers Creek Rhyolite, Mammoth Mountain Rhyolite, Shallow Creek Quartz 

Latite, Windy Gulch Member of Bachelor 

Mountain Rhyolite. 

H uerto Formation. 

(Not used in report area.) 

Nelson Mountain Quartz Latite. 

Phoenix Park Member of La Garita Quartz 

Latite. 

Campbell Mountain and Willow Creek 

Members of Bachelor Mountain Rhyolite, 

Outlet Tunnel Member of La Garita 

Quartz Latite. 

ART. 132 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D54-D63. 1964. 

D54 
(j /'--....---

....----X---------

Spring Creek 

Pass .;,-a. 

~e 

COLORADO 

..._Area of report 

X Bristol 

Head 

107"00' 

0 

STEVEN AND RATTE 

X San Luis Peak 

X Beautiful 

Mountain 

5 

Wagon 

Wheel 

Gap 

<'1 X "' s_ov." Half G Moon ..<l 1y 1 Pass 1' 4 

10 Ml LES 

FIGURE 132.1.-Locality m~p of the central San Juan Mountains, Colo. 

D55 

\ 
D56 MINERALOGY AND PETROLOGY 

pyroclastic eruptions in the Potosi culminated in cauldron subsidence (table 132.2). Three 1najor cauldrons 

are well documented, and a fourth is known but has 

not yet been studied in detail. As a result, many of 

the units were confined by rough preexisting structural 

topography, and topographic position n1ay have little 

bearing on the relative age of a unit. In addition, 

typical rocks frmn many of the formations appear so 

nearly identical that lithologic si1nilarity alone is not 

a reliable basis for correlation. The Creede Formation 

and Fisher Quartz Latite in part intertongue, and both 

units filled the margin of the Creede caldera (Steven 

and Ratte, 1 960b) shortly after subsidence and doming of the caldera core; the pyroclastic and flow rocks 

appear to represent a continuation of the same period 

of volcanic activity and to be comagmatic with the 

earlier so-called Potosi units. 

The previously established volcanic sequence (table 

132.1) in the central San Juan Mountains (Enunons 

and Larsen, 1923; Cross and Larsen, 1935; Larsen and 

Cross, 1956) is inadequate to explain the geology. 

Because so many of the rock units are n1iscorrelated, 

we are unable to accon1nwdate the tern1inology of the 

Potosi Volcanic Series to the revised voleanic sequence 

we have determined (tables 132.1 and 132.2), and thus 

we do not use the Potosi Volcanic Series in the Creede 

area. Likewise, the Alboroto and Piedra Rhyolites 

include units so widely scattered within our local sequence that we have not been able to retain them in 

any sense equivalent to their original intent, and we 

do not use them in the Creede area either. 

In the western San Juan Mountains, Luedke and 

Burbank (1963) have recently redefined the Potosi 

Volcanic Series to Potosi Volcanic Group, an assemblage of rocks which is not believed to contain any 

of the units in the central San Juan ~fountains discussed here. 

The age of the volcanic rocks in the central San Juan 

Mountains is uncertain, as no diagnostic fossils have 

been found anywhere within the volcanic succession. 

The Telluride Conglomerate and Blanco Basin Formation underlying the volcanic rocks have been considered 

to be Oligocene(?) in age (Larsen and Cross, 1956, p. 

61), but the evidence adn1ittedly was not conclusive. 

So far as we can ascertain, the succeeding volcanic activity could have begun any tin1e within the middle 

Tertiary. The Creede Formation, which is mnong the 

youngest of the units related to volcanic activity in the 

San Juan Mountains, contains abundant well-preserved 

plant fossils, but none have proved diagnostic. EstiTABLE 132.2.-Volcanic stratigraphy of the central San Juan Mountains, Colo. 

(*redefined name; **new name] 

Age 

Middle or 

late 

Tertiary 

GEOGRAPHIC DISTRIBUTION OF UNITS 

+---- Generally west or south Generally east or north --~ 

*Fisher Quartz Latite *Creede Formation 

DOMING OF CREEDE CALDERA 

**Snowshoe Mountain Quartz Latite 

*Nelson Mountain Quartz Latite 

*Rat Creek Quartz Latite 

*Huerto Formation J **Wason Park Rhyolite } 

*Mammoth Mountain Rhyolite 

Quartz latite and 

rhyolite lava flows 

I 

I **Farmers Creek Rhyolite 

SUBSIDENCE OF BACHELOR MOUNTAIN CAULDRON 

**Shallow Creek 

Quartz La ti te 

{ 

**Bachelor Mountain Rhyolite 

*Windy Gulch Member 

*Campbell Mountain Member 

*Willow Creek Member 

Rhyolite of Miners Creek 

**La Garita Quar:z Latite 

I 

I J *Phoenix Park Member 

SUBSIDENCE OF LA GARITA CAULDRON 

*Outlet Tunnel Member 
STEVEN AND RATTE D57 

mates of the age of the formation based on the same 

fossils have ranged from very late Miocene or very early 

Pliocene (Brown, R. W., in Larsen and Cross, 1956, p. 

167) to early to n1iddle Pliocene (MacGinitie, 1953, p. 

60-7 5). Pollen studies by Estella Leopold (written 

communication, 1961) suggest an age between late 

Miocene through middle Pliocene. 

The rock units in the central San Juan Mountains 

near Creede, and their relations to recurrent cauldron 

subsidence, are sumn1arized in table 132.2. The relations of these units to those fron1 other centers of eruption in the San Juan Mountains are not as yet fully 

established. 

LA. GAR IT A QUARTZ LA TITE 

La Garita Quartz Latite is a new name here given to 

a part of the assemblage of rocks formerly included in 

the Alboroto Rhyolite by Larsen and Cross (1956, p. 

132). The La Garita Quartz Latite is well exposed along 

the upper canyon of East Willow Creek north of Creede, 

and forms the bulk of La Garita Mountain farther 

northeast (fig. 132.1), which serves as type area for the 

formation. 

The La Garitu. Quartz Latite consists largely of identical densely welded ash-flow tuffs that are equivalent to 

the former Outlet Tunnel and Fhoenix Park Quartz 

Latites of Emmons and Larsen (1923, p. 18, 30). The 

Outlet Tunnel unit was described by them as underlying rocks here called Bachelor Mountain Rhyolite and 

the Phoenix Park unit as interbedded with and overlying them. In addition to the difference in stratigraphic position noted by Emmons and Larsen, we have 

determined that accumulation of the two units was 

separated by subsidence of the La Garita cauldron 

(table 132.2). We are calling those rocks that accumulated before the Bachelor Mountain Rhyolite and before 

cauldron subsidence the Outlet Tunnel Member, and 

those that accmnulated concurrently with and after the 

Bachelor Mountain Rhyolite and after cauldron subsidence the Phoenix Park Member. Emmons and Larsen (1923, p. 30) erroneously believed that the bulk of 

these rocks along upper East Willow Creek and La 

Garita Mountain belonged to their Phoenix Park unit, 

whereas we have found that they formed before cauldron 

subsidence and clearly belong to the redefined Outlet 

Tunnel Member. 

Typical rocks from both members of the La Garita Quartz 

Latite appear identical and consist of crystal-rich ashflow tuff, largely densely welded, that consists of about 

half reddish, lithoidal matrix, and half phenocrysts and 

fragments of foreign rock types. Plagioclase phenocrysts constitute about 30 percent of the rock, sanidine 

6 percent, quartz 4 percent, biotite 4 percent, hornblende 

4 percent, and magnetite and accessory minerals 2 percent. 

The Outlet Tunnel Member is more than 2,000 feet 

thick in the type area, but the base of the member is 

nowhere exposed in this vicinity and the full thickness 

could not be determined. The Phoenix Park Member 

is between 350 and .500feet thick along the east flank 

of East Willow Creek, and it wedges out a short distance 

northeast against steep underlying topography. 

RHYOUTE OF MINERS. CREEK 

The oldest rock unit known in the western part of 

the Creede area in the central San Juan Mountains is 

an accumulation of rhyolite flows and pyroclastic rocks 

more than 1,200 feet thick exposed along the flanks of 

Miners Creek. It is overlapped on its southeast margin 

by the Bachelor Mountain Rhyolite, and the abrupt character of the overlap suggests that the main mass of the 

underlying rhyolite 1nay be a bulbous volcanic dome or 

steep-sided flow. The rock is a gray to pink porphyry 

consisting of about 20 percent phenocrysts and 80 

percent lithoidal groundmass. Plagioclase and sanidine 

predominate among the phenocrysts, but sparse, small 

biotite crystals are widespread. 

A formal name is not proposed for the rhyolite of 

Miners Creek because there is little evidence of its 

areal extent or of its relations with rock units other 

than the Bachelor Mountain Rhyolite. 

BACHE.LOR MOUNTAIN RHYOLITE 

Bachelor Mountain Rhyolite is a new name given here 

to all the rhyolitic rocks included by Emmons and 

Larsen (1923) in their Willow Creek Rhyolite, Campbell 

Mountain Rhyolite, Windy Gulch Rhyolite Breccia, 

and intrusive rhyolite porphyry. Emmons and Larsen 

(1923, p. 19-30) described the Willow Creek and Campbell Mountain Rhyolites as two sequences of rhyolitic 

lava flows and flow breccias separated by an irregular 

erosion surface, and included both in their Alboroto 

Group. They believed (1923, p. 38-40) that the Windy 

Gulch Rhyolite Breccia was separated from the Campbell Mountain Rhyolite by a major unconformity, and 

that it belonged to their younger Piedra Group. Instead, we have found the Willow Creek, Campbell 

Mountain, and Windy Gulch units to be members of 

an intergradational sequence of pumiceous pyroclastic 

rocks that warrants formation rank. These rocks range 

upward from densely welded tuff closely resembling 

fluidal rhyolite flow rock (Willow Creek Member), 

through compact welded tuff in the middle (Campbell 

Mountain Member), to a porous moderately welded to 

non welded tuff at the top (Windy Gulch Member). 

Breaks within this sequence occur only where the 

Bachelor Mountain rocks intertongue with other volcanic rocks at the margins of the deposit. 
D58 MINERALOGY AND PETROLOGY 

Bachelor Mountain Rhyolite is named for discontinuous but representative exposures in the type area 

of the formation on Bachelor Mountain, northwest of 

Creede. No single complete section of the formation 

is exposed anywhere in the central San Juan Mountains. 

The greatest thickness observed of the Willow Creek 

Member is more than 2,000 feet thick, and the base is 

not exposed. More than 1,000 feet of the Campbell 

Mountain Member and more than 900 feet of the Windy 

Gulch Member are exposed locally, but the full thick~ess 

of either unit could not be measured. 

The Campbell Mountain and Windy Gulch Members 

intertongue laterally with flows and breccias of Shallow 

Creek Quartz Latite to the west, and a lens of typical 

Campbell Mountain welded tuff is interlayered with 

the Phoenix Park Member of the La Garita Quartz 

Latite to the east. 

The Bachelor Mountain Rhyolite consists mainly of 

microcrystalline to cryptocrystalline matr~x with 5 

percent or less of phenocrysts and 20 percent or less 

of foreign rock fragments. The phenocrysts are largely 

sanidine and plagioclase, with sparse biotite and magnetite. Inclusions of foreign rock fragments range from 

a few percent in the Willow Creek Member, to as much 

as 20 percent in parts of the Campbell Mountain and 

Windy Gulch Members. 

Eruption of the Bachelor Mountain Rhyolite culminated in collapse of the Bachelor Mountain cauldron 

(table 132.2) near the town of Creede, and in the development of a series of normal faults that extend north 

to northwest out from the more strongly subsided area. 

SHALLOW CREEK QUARTZ LA TITE 

Shallow Creek Quartz Latite is a new name here 

applied to a group of lava flows and volcanic breccias 

that crop out in the drainage basins of Rat Creek, 

Miners Creek, and Shallow Creek 2 to 4~~ miles west of 

Creede. The flows and breccias are irregularly mixed, 

and the unit varies so greatly from place to place that 

no single section is representative; the largest known 

body, along the northern flank of the Shallow Creek 

drainage basin, is designated as the type area of the 

formation. Maximum thickness in this . vicinity is 

600 to 700 feet. 

The rocks included in the Shallow Creek Quartz 

Latite were originally described by Emmons and Larsen 

(1923, p. 36-38) under the informal name hornblende 

quartz latite. This unit marked the base of their 

Piedra Group in the western part of the Creede district, 

and they believed that it was separated from the underlying Alboroto rocks by an irregular erosional unconformity. Larsen and Cross (1965, p. 143) called the 

same rocks hornblende rhyolitic latites, and agreed 

with the earlier stratigraphic interpretations. Our 

mapping, on the other hand, has shown that the Shallow 

Creek Quartz Latite intertongues laterally with the 

upper members of the gradational sequence of rocks in 

the Bachelor Mountain Rhyolite, and that the supposed 

unconformity between rocks included by Emmons and 

Larsen (1923) in their Alboroto and Piedra Groups does 

not exist. 

The Shallow Creek Quartz Latite consists largely of 

volcanic breccias; lava flows are thin and are estimated 

to make up less than 10 percent of the formation. 

The rock is porphyritic, with small phenocrysts, rarely 

exceeding a few millimeters in maximum dimensions, 

set in an aphanitic groundmass. The phenocrysts 

consists mainly of plagioclase, 15 percent; hornblende, 

5 percent; and a few percent each of biotite and magnetite. Sanidine and clinopyroxene occur locally. 

Much of the Shallow Creek Quartz Latite is irregularly 

altered, and either is oxidized and burnt in appearance, 

or is irregularly altered to clay and crisscrossed with 

veinlets of quartz and carbonate. 

FARMERS CREEK RHYOLITE 

Farmers Creek Rhyolite is a new name here given to 

a heterogeneous assemblage of pyroclastic rocks and 

minor flow rocks that was deposited locally on the rough 

topography left by subsidence of the Bachelor Mountain 

cauldron. Larsen and Cross (1956, p. 146-147) refer 

the rocks here called Farmers Creek Rhyolite to the 

basal part of the lower member of their Piedra Rhyolite. 

The different rock types in the Farmers Creek Rhyolite 

are well exposed in its type area along Farmers Creek, 

2,% to 4,% miles east of the town of Creede where a 

thickness of more than 1,000 feet is indicated. 

The Farmers Creek Rhyolite can be divided into 

three subequal parts in the type area and along West 

Bellows Creek to the east. The lower third is a soft, 

cavernous-weathering pumiceous tuff breccia that 

forms massive, unsorted layers a few feet to a few tens 

of feet thick. Foreign rock fragments constitute 15 to 

26 percent of the rock. Some of the rocks are moderately welded, but most are only slightly welded or are 

nonwelded. A few lenses of red porphyritic flow 

breccia are interlayered with the predominant tuff 

breccias. 

The middle third of the formation consists of a succession of layers .of differentially welded tuffs whose 

harder units form prominent ledges along the hill 

slopes. Massive dark-brown densely welded tuff is the 

most widely exposed rock type. This grades both 

vertically and laterally into a lighter brown obviously 

fragmental welded tuff with good eutaxitic texture. 

Phenocrysts constitute 5 to 10 percent of the rock and 
STEVEN AND RATTE D59 

consist of sanidine, plagioclase, biotite, and magnetite. 

Foreign rock fragmentd con.stitute 5 to 10 percent of 

the rock. 

Crystal-rich welded tuff forming the upper third of 

the Farmers Creek Rhyolite is exposed only along the 

canyon of West Bellows Creek. Phenocrysts of 

plagioclase, sanidine, biotite, hornblende, clinopyroxene, sphene, quartz, and magnetite are so abundant that the matrix is largely obscured and most of 

the rock appears structureless in hand specimen. The 

composition of these rocks appears anomalous with 

respect to the rest of the formation, and its inclusion in 

the Farmers Creek Rhyolite is provisional. 

MAMMOTH MOUNTAIN RHYOLITE 

Mammoth Mountain Rhyolite was originally named 

by Emmons and Larsen (1923, p. 40-44), who believed 

it to be a single thick lava flow. An overlying unit 

consisting largely of parti51lly welded to nonwelded 

tuffs was mapped separately. Larsen and Cross (1956, 

p. 147) later assigned all these rocks, as well as the 

underlying Farmers Creek Rhyolite, to the lower 

rhyolite member of their Piedra Rhyolite. As redefined here, the Mammoth Mountain Rhyolite 

includes the Mammoth Mountain and the overlying 

soft tuffs of Emmons and Larsen (1 923), as well as all 

laterally equivalent rocks, which together form a great 

composite ash-flow sheet (Smith, 1960, p. 158). 

The Mammoth Mountain Rhyolite is widespread in the 

central San Juan Mountains, and good exposures have 

been recognized as far as 15 miles southeast, 10 miles 

southwest, and 18 miles south of Creede. It is absent 

along the Continental Divide north of Creede, where 

mountainous terrain stood above the level of accumulation at the time the Mammoth Mountain ash flows 

were erupted. The formation is locally as much as 

2,000 feet thick, and is 500 to 1,000 feet thick over 

wide areas. 

The Mammoth Mountain Rhyolite ranges from crystal-poor welded ash-flow tuffs with 5 to 10 percent 

phenocrysts to crystal-rich welded ash-flow tuffs with 

30 to 60 percent phenocrysts. The matrix of the 

densely welded tuff is typically lithoidal and reddishbrown except for the black glass of the basal vitrophyre 

layer. Plagioclase phenocrysts are predominant in all 

of the rock. Sanidine phenocrysts are common in the 

crystal-poor rocks, but are absent in most of the crystalrich phase. Biotite is the most prevalent n1afic phenocryst in the Mammoth Mountain Rhyolite; green 

clinopyroxene phenocrysts are characteristic of and are 

restricted to the crystal-rich rocks. The ash-flow tuffs 

range in composition from rhyolite to quartz latite. 

716-195 0-64-5 

WASON PA'RK RHYOLITE 

Wason Park Rhyolite is a new name given to a distinctive sheet of rhyolitic welded tuff that forms prominent cliffs throughout much of the central San Juan 

area near Creede. It forms the floor of Wason Park, 

a high flat beneh on the southern flank of the La Garita 

Mountains northeast of Creede, which is taken as the 

type area. Wason Park Rhyolite is equivalent to the 

tridymite latite unit of Emmons and Larsen (1923, 

p. 45), and in its type area and in most other places was 

included by Larsen and Cross (1956, p. 152-153) in the 

tridymite' rhyolitic latite member of their Piedra 

Rhyolite. 

The Wason Park Rhyolite is 600 to 700 feet thick 

over wide areas in the central San Juan Mountains; it 

wedges out northward toward the Continental Divide. 

The formation is largely coextensive with the underlying 

Mammoth Mountain Rhyolite, except that it extends 

somewhat farther laterally over the rough underlying 

topography. A tongue of Huerto Formation separates 

the Mammoth Mountain and Wason ·Park Rhyolites 

south of Bristol Head, about 10 miles southwest of 

Creede, and several quartz latite lava flows intervene 

between the formations east of Wagon Wheel Gap, 8 to 

15 miles southeast of Creede. 

Typical Wason Park Rhyolite is a crystal-rich densely 

welded tuff with 25 to 30 percent phenocrysts set in a 

reddish-brown lithoidal matrix. Distinctive white to 

light-gray tridymitic streaks representing collapsed 

pumice fragments are widespread and are characteristic 

of the formation. The phenoerysts are predominantly 

plagioclase and sanidine, with minor. biotite and magnetite. A dense black vitrophyre 10 to 15 feet thick is 

generally present at the base of the formation, and the 

top locally retains a few feet to a few tens of feet of less 

welded rock. 

HUERTO FORMATION 

The name Huerto Formation was originally used by 

Patton (1917, p. 20), ana. later by Emmons and.Larsen 

(1923, p. 12) and Knowlton (1923, p. 184). The same 

rocks were called Huerto Andesite by Cross and Larsen 

(1935, p. 82), and Huerto Quartz Latite by Larsen and 

Cross (1956, p. 143); they believed that the Huerto 

rocks accumulated during a separate period of volcanic 

activity between eruption of their Alboroto and Piedra 

Rhyolites. 

In contrast, we have found that the Huerto rocks 

were erupted fron1 a number of separate but areally 

assoeiated centers in the central San Juans concurrently 

with many of the units included by Larsen and Cross 

in their Piedra Rhyolite. Also, a local assemblage of 

lavas and breccias 6 to 10 miles southwest of Creede, 
D60 MITNERALOGY AND PETROLOGY 

called Conejos Quartz Latite by Larsen and Cross (1956, 

p. 99), is now known to be part of the compound Huerto 

accumulation. Although it eventually may be possible 

to separate out individual mappable units, present 

limited data make it expedient to refer to the volcanic 

accumulation as a whole as the Huerto Formation. 

The main mass of the Huerto Forn1ation lies southwest of Creede, where three n1ain centers of accun1ulation were reported by Larsen and Cross (1956, p. 143). 

Marginal rocks of the Huerto Formation intertongue 

with the widespread welded tuff units north and northeast of these centers. The dark lavas and breccias 

underlie Mammoth Mountain Rhyolite; a thin tongue 

of breccias intervenes locally between the Man1moth 

Mountain and Wason Park Rhyolites; and a tongue of 

lavas and breccias above the Wason Park Rhyolite 

extends nearly to Creede. 

The Huerto Formation thickens and thins n1arkedly 

from place to place, and the different flow and breccia 

accun1ulations n1ay originally have ranged widely in 

thickness. l\1ore than 2,000 feet of rudely bedded 

Huerto breccias is exposed on the west face of Bristol 

Head, southwest of Creede; the local accmnulation of 

Huerto underlying the Manunoth Mountain Rhyolite 

south of Bristol Head is more than 800 feet thick; and 

the maxim un1 preserved thickness of H uerto rocks overlying the Wason Park Rhyolite near Creede is about 

450 feet. 

Most rocks in the Huerto Formation are dark, finegrained lavas and breccias. They range widely in composition, but most appear to be dacitic. Phenoerysts 

are generally small and inconspicuous, and consist of 

predominant plagioclase and minor associated clinopyroxene, hornblende, and n1agnetite. 

INTRACALDERA LAVA FLOWS 

Local thick quartz latitic to rhyolitic lava flows are 

interlayered with the widespread ash-flow sheets in the 

central San Juan Mountains (table 132.2). Most of 

these flows and son1e related volcanic necks are exposed 

around the outer margin of the Creede caldera, suggesting that this margin served to localize lnany of the 

eruptions. Most of the rocks are drab gray, coarsely 

porphyritic quartz latites; some lighter colored rhyolitic 

flows are interspersed with the quartz latite flows or 

occur singly. 

The oldest of these local lava-flow accumulations 

underlies the Mammoth Mountain Rhyolite east of 

Goose Creek and 5 miles south of Wagon Wheel Gap. 

A number of flows intervene between the Mammoth 

Mountain and Wason Park Rhyolites east and northeast 

of Wagon Wheel Gap, and a distinctive white rhyolite 

flow occupies the saiYte position near Shallow Creek, 

northwest of the caldera. A quartz latite flow overlies 

the Wason Park Rhyolite and forms the floor of Silver 

Park northeast of the Creede caldera. Similar flows 

and a related neck are exposed about 5~ miles north of 

Creede; these rocks are believed to underlie the Rat 

Creek Quartz Latite, but available evidence is not 

conclusive. 

RAT CREEK QUARTZ LATITE 

Rat Creek Quartz Latite as here redefined is a widespread sequence of welded and non welded ash-flow tuffs, 

with both the base and top of the forrnation marked by 

surfaces that show evidence of erosion, but with no erosional break recognized within the sequence. A local 

near-vent accumulation of lavas and pyroclastic rocks 

along West Willow Creek intertongues laterally with the 

more widespread ash-flow tuffs. 

As originally defined by Emmons and Larsen (1923, 

p. 57-58), the name Rat Creek Quartz Latite was applied only to the upper part of this sequence. They 

believed the rocks to be interlayered lava flows and 

tuffs, but recognized that they were closely related to 

the underlying tuff to which they gave the inforn1al 

name "quartz latite tuff" (Emmons and Larsen, 1923, 

p. 54-57). Larsen and Cross (1956, p. 153-156) generally followed Emmons and Larsen in separating the 

lower tuff fron1 the upper rnixed unit. The lower unit 

was called the tuff men1ber of their Piedra Rhyolite, 

and the upper mixed unit was lumped with the overlying Nelson Mountain Quartz Latite of Emmons and 

Larsen (1923, p. 59) into the rhyolitic latite rne1nber of 

their Piedra Rhyolite. Hence their upper rhyolitic 

member included an erosional surface representing a 

significant break in deposition of the pyroclastic rocks, 

and their upper and lower melnbers met at a gradational 

contact. 

The Rat Creek Quartz Latite is now found only in the 

high mountains extending east fr01n the Spring Creek 

Pass area, 13 miles northwest of Creede, through the 

Nelson Mountain area north of Creede, to the La 

Garita Mountains area northeast of Creede. It is 

excellently exposed at Wheeler Monun1ent, just south 

of Half Moon Pass. The forn1ation consists largely of 

soft pyroclastic rocks, which typically forrn steep debriscovered slopes beneath the highest cliff-forming welded 

tuff unit in the area. The formation is 600 to 800 feet 

thick over wide areas, but ranges in thickness frorn 0 

where it wedges out against older hills to nearly 1,000 

feet locally. 

Most of the Rat Creek rocks are slightly welded to 

nonwelded ash-flow tuffs. A distinctive pink welded 

tuff 50 to 100 feet thick forms a prominent ledge in 

the middle of the unit north of Creede. Thin layers 

of air-fall tuff or reworked sedimentary tuff intervene 

locally between the ash-flow layers. The welded tuffs 
STEVEN AND RATTE D61 

contain 20 to 30 percent phenocrysts, chiefly plagioclase, minor biotite and clinopyroxene; and sparse 

sanidine, quartz, hornblende, and magnetite. 

NELSON MOUNTAIN QUARTZ LATITE 

As redefined in this report, Nelson Mountain Quartz 

Latite includes all rocks in the former Equity Quartz 

Latite (Alboroto Group), and Nelson Mountain 

Quartz Latite (Piedra Group) of En1n1ons and Larsen 

(1923, p. 32-34, 59-60). Larsen and Cross (1956) did 

not mention the former Equity unit specifically, but 

show the area underlain by it as Alboroto Rhyolite on 

their geologic Inap, and the for1ner Nelson Mountain 

Quartz Latite was included in the rhyolitic latite mmnber of their Piedra Rhyolite. We have found that these 

units intergrade and forn1 a single genetic unit to which 

we have extended the name Nelson Mountain Quartz 

Latite. The name Equity Quartz Latite is herewith 

abandoned. 

Nelson Mountain Quartz Latite characteristically 

forms resistant capping ledges on flat-topped ridges 

from the Nelson Mountain area north of Creede to the 

Snow Mesa area, 12 miles northwest of Creede, and 

on the flat crest of the La Garita Mountains eastward 

from the Half Moon Pass area 9 1niles northeast of 

Creede. In addition, a great mass of Nelson Mountain 

Quartz Latite underlies the San Luis Peak area 9 miles 

north of Creede, where it apparently fills a cauldron 

structure. The widespread sheet of Nelson Mountain 

Quartz Latite ranges generally from 0 to 500 feet in 

thickness, but according to Larsen and Cross (1956, p. 

132) nearly 4,000 feet of the unit (which they called 

Alb oro to Rhyolite) is exposed in the San Luis Peak area. 

The Nelson Mountain Quartz Latite is a con1posite 

ash-flow sheet that changes from a simple cooling unit 

(Smith, 1960, p. 157) of predominantly densely welded 

tuft in the Nelson Mountain area, north of Creede, 

laterally, both to the east and the west into a compound cooling unit, and eastward at least into several 

individual cooling units that range from predominantly 

densely welded to predominantly nonwelded. 

Phenocrysts range from 20 to 50 percent of the 

Nelson Mountain Quartz Latite, and consist for the 

most part of plagioclase, with lesser quantities of biotite, and minor or accessory clinopyroxene, quartz, 

sanidine, hornblende, and magnetite. 

SNOWSHOE MOUN.TAIN QUARTZ LATITE 

Snowshoe Mountain Quartz Latite is a new na1ne 

given to the n1ass of quartz latite ash-flow tuffs, 

mostly densely welded, that constitutes most of the 

core of the Creede caldera. The type area of the 

formation is Snowshoe Mountain which forms the 

highest part of the caldera core, south of Creede. 

Larsen and Cross (1 956, p. 132, 138) believed that 

the great mass of quartz latite under Snowshoe Mountain was a local accumulation, possibly a single large 

flow, within the upper rhyolitic latite member of their 

Alboroto Rhyolite. In contrast, we have found the 

Snowshoe Mountain Quartz Latite to be the youngest 

major ash-flow unit in the central San Juan Mountains, 

and it is thus more equivalent to the upper part of the 

Piedra Rhyolite of Larsen and Cross (1956, p. 144-155). 

The Snowshoe Mountain Quartz Latite is restricted 

to the core of the Creede caldera, and the sum of several 

partial sections indicates that the formation is at least 

4,000 feet and perhaps more than 6,000 feet thick. 

Talus breccias are intertongued marginally with at 

least the upper 2,000 feet of this unit, indicating that it 

accumulated within an existing depression. Caldera 

subsidence and accumulation are believed to have been 

concurrent. 

TheSnowshoeMountainQuartzLatiteconsistsentirely 

of crystal-rich ash-flow tuff. Most of the rock is densely 

welded, and toward the center of the caldera only a few 

local less welded partings indicate the compound cooling 

characteristics of the deposit. Toward the southern 

part of the caldera, however, at least two different 

segments of the formation, each several hundred feet 

thick, soften laterally from densely welded to slightly or 

moderately welded. The top of the for1nation is everywhere marked by less welded rocks that range up to 

several hundred feet in thickness. 

The Snowshoe Mountain Quartz Latite is a drab crystal rich welded tuff that closely resembles much of the 

more densely welded rock in the Nelson Mountain 

Quartz Latite. Snowshoe Mountain rocks consist 

of an average of nearly half phenocrysts, and have a 

distinctly granular aspect in hand specimen. As in the 

other quartz latitic ash-flow units, plagioclase predominates among the phenocrysts, followed in abundance by biotite, and by 1ninor clinopyroxene, hornblende, quartz, sanidine, and magnetite. 

FISHE'R QUARTZ LATITE 

As used by Larsen and Cross (1956, p. 172), the 

Fisher Quartz Latite (or latite-andesite) was a sequence 

of local accumulations of coarsely porphyritic flows 

and breccias in the San Juan Mountains and was believed to be younger than the Potosi Volcanic Series and 

the Creede Formation, and older than the Hinsdale 

Formation. Larsen and Cross (1 956, p. 172) state 

that these rocks have certain textural and mineralogical characteristics which distinguish them from 

rocks of the Potosi Volcanic Series, and that at different places they rest unconformably on the Silverton 

Volcanic Series, the Potosi Volcanic Series, and the 

Creede Formation. Rocks assigned to this formation 
D62 MINERALOGY AND PETROLOGY 

occur throughout the central San Juan Mountains. 

Our work has shown that this earlier concept n1ust be 

revised in in1portant aspects. The rocks in the type 

area of the formation on Fisher Mountain were 

erupted after the last 1nain subsidence of the 

Creede caldera and followed don1ing of the caldera 

core. We therefore restrict the Fisher Quartz Latite 

to lavas of this age. Son1e Fisher flows around the 

Creede caldera underlie the Creede Formation, others 

intertongue with it, and still others appear smnewhat 

younger; the bulk of the Fisher Quartz Latite, however, 

appears to have been erupted concurrently with Creede 

sedin1entation. The evidence for the Fisher being 

equivalent in age to the Creede Formation directly 

contradicts Larsen and Cross (1956, p. 168, 172), 

who believed that the Fisher lavas flowed down deep 

valleys cut into the Creede. 

Many Fisher rocks appear identical with coarsely 

porphyritic flows interlayered with earlier widespread 

ash-flow sheets adjacent to the Creede caldera (Piedra 

Rhyolite of earlier terminology), and Larsen and Cross 

( 1956, pl. 1) have inel uded several of these older flows 

in their Fisher Quartz Latite. The only clear distinction between these different flows is in age relative 

to caldera subsidence. Thus the contention of Larsen 

and Cross (1956, p. 172) that Fisher Quartz Latite is 

distinct fron1 all rocks in the Potosi Volcanic Series in 

ti1ne and petrologic character does not appear tenable, 

and in our opinion the Fisher eruptions represent 

merely a continuation of a related sequence of volcanic 

events. 

Most Fisher Quartz Latite near Creede was erupted 

around the margin of the Creede caldera, or along 

grabens extending outward from the caldera. The 

largest mass underlies Fisher Mountain and adjacent 

areas south of the ealdera; another substantial body 

accumulated in the Wagon Wheel Gap area 5 to 8 

miles southeast of Creede. A smaller accumulation is 

exposed on the west flank of the caldera core 7 miles 

southwest of Creede, and several flows cap the ridge 

between upper Rat and lvliners Creeks northwest of 

Creede. 

Possibly some of the other relatively late accumulations of coarsely prophyritic lava through the central 

San Juan Mountains correlate with the Fisher Quartz 

Latite as we have redefined it, but we would prefer not 

to extend the name to these until their age relations 

can be established n10re definitely. 

Fisher Quartz Latite consists of coarsely porphyritic 

lava, predominantly quartz latite but with some 

rhyolite. Plagioclase, biotite, and clinopyroxene are 

the most abundant phenoerysts, and small quantities 

of magnetite are invariably present. In addition, 

some flows contain significant quantities of hornblende, 

sanidine, and quartz. 

CREEDE FORMATION 

The Creede Formation was originally named and 

deseribed by Emmons and Larsen (1923, p. 61-70), 

who divided it into a lower member consisting largely 

of fine-grained well-bedded deposits with interbedded 

travertine, and an upper n1ember consisting of coarser 

material, largely stream deposits, and a few thin lava 

flows. Larsen and Cross (1956, p. 167-172) closely 

followed the earlier description. We also include the 

same assemblage of rocks in the Creede Formation, but 

have found that the earlier recognized subdivisions are 

in a large part laterally equivalent facies not readily 

separated. 

The Creede Formation consists largely of sedimentary 

rocks that were deposited in a structural trough around 

the margin of the domed core of the Creede caldera. 

These deposits follow the western, northern and eastern 

margin of the caldera for nearly 270° of arc, from Lime 

Creek, down the Rio Grande to Wagon Wheel Gap, 

and up Goose Creek for nearly 5 miles. The original 

thickness of the formation is not known, but present 

remnants extend over a vertical range of at least 2,400 

feet. 

The Creede Formation consists of several distinct 

facies that are so complexly intermixed that it is not 

practical to separate them. Thin-bedded tuffaceous 

lake beds, largely shale and sandstone with some tuff 

beds, inte~ongue marginally with fluviatile sandstone 

and conglomerate beds in the vicinity of old tributary 

valleys, and with fanglomerate and coarse sedimentary 

breccias of local derivation elsewhere along the margins. 

The edge of the formation against buried rough topography is commonly marked by accumulations of talus, 

landslide, slopewash, and similar debris. Travertine 

and calcareous tufa were deposited widely by mineral 

springs that were active concurrent with sedimentation. 

Some volcanic breccia and a few layers of welded tuff 

are interlayered locally. 

REFERENCES 

Cross, Whitman, and Purington, C. W., 1899, Description of 

the Telluride quadrangle [Colorado}: U.S. Geol. Survey 

Geol. Atlas, Folio 57. 

Cross, Whitman, Howe, Ernest, and Ransome, F. L., 1905, 

Description of the Silverton quadrangle [Colorado}: U.S. 

Geol. Survey Geol. Atlas, Folio 120. 

Cross, Whitman, and Larsen, E. S., 1935, A brief review of the 

geology of the San Juan region of southwestern Colorado: 

U.S. Geol. Survey Bull. 843, 138 p. 

Emmons, W. H., and Larsen, E. S., 1923, Geology and ore 

deposits of the Creede district, Colorado: U.S. Geol. Survey 

Bull. 718, 198 p. 
STEVEN AND RATTE D63 

Knowlton, F. H., 1923, Fossil plants from the Tertiary lake beds 

of south-central Colorado: U.S. Geol. Survey Prof. Paper 

131, p. 183-192. 

Larsen, E. S., Jr., and Cross, Whitman, 1956, Geology and 

petrology of the San Juan region, southwestern Colorado: 

U.S. Geol. Survey Prof. Paper 258, 303 p. 

Luedke, R. G., and Burbank, W. S., 1963, Tertiary volcanic 

stratigraphy in the western San Juan Mountains, Colorado: 

Art. 70 in U.S. Geol. Survey Prof. Paper 475-C, p. C39-

C44. 

MacGinitie, H. D., 1953, Fossil plants of the Florissant beds, 

Colorado: Carnegie Inst. Washington Pub. 599, 198 p. 

Patton, H. B., 1917, Geology and ore deposits of the PlatoroSummitville mining district, Colorado: Colorado Geol. 

Survey Bull. 13, 122 p. 

Smith, R. L., 1960, Zones and zonal variations in welded ash 

flows: U.S. Geol. Survey Prof. Paper 354-F. 

Smith, R. L., and Bailey, R. A., 1962, Resurgent cauldronstheir relation to granitic ring complexes and large volume 

rhyolitic ash-flow fields, [abs.) in International Symposium 

on Volcanology, Japan: Internat. Assoc. Volcanology, 1962, 

p. 67-68. 

Steven, T. A., and Ratte, J. C., 1960a, Geology and ore deposits 

of the Summitville district, San Juan Mountains, Colorado: 

U.S. Geol. Survey Prof. Paper 343, 70 p. 

--- 1 960b, Relation of mineralization to caldera subsidence 

in the Creede district, San Juan Mountains, Colorado: Art. 

8 in U.S. Geol. Survey Prof. Paper 400-B, p. B14-B17. 
Article 133 

VALLERIITE AND THE NEW IRON SULFIDE, MACKINAWITE 

By HOWARD T. EVANS, JR., CHARLES MILTON, E. C. T. CHAO, ISIDORE ADLER, 

CYNTHIA MEAD, BLANCHE INGRAM; and RICHARD A. BERNER/ Washington, D.C.; La Jolla, Calif. 

Abstract.-Valleriite from Loolekop, South Africa, and Kaveltorp, Sweden, is rhombohedral, space group R3m or R3m, with 

a=3.792 A, and c=34.10 A, and its probable unit-cell content 

is 6CuFeS2. Mackinawite, a new copper-free iron sulfide from 

the Mackinaw mine, Snohomish County, Wash., is tetragonal, 

space group P4jnmm, with a=3.679 A, c=5.047 A, and a unitcell content of 2FeS. Both minerals evidently have layer structures, in accord with their extreme optical anisotropy. Many 

occurrences of mackinawite have probably been mistaken for 

valleriite. 

Few minerals have caused mineralogists more justified uncertainty or unsound assurance than the sulfide 

valleriite. Since its discovery at Nya Kopparberg, 

Sweden, by Blon1strand (1870) almost a century ago, 

it has led an uneasy life in the n1ineralogicalliterature. 

Its first description was encumbered with a con1plex 

and implausible proposal for composition, which led 

Petren (1898) to reject the work of Blomstrand and 

consign the mineral to the limbo of species discredited 

as mixtures. It was revived by Ramdohr and Odman 

(1932) on the basis of a restudy of the Swedish material 

already described by Blomstrand and Petren. Only 

recently has the existence been suspected of another 

distinct sulfide phase occurring in mineral assemblages 

similar to those which contain valleriite (Milton and 

Milton, 1958; Kouvo and Vuorelainen, 1959). This 

new phase, which we designate mackinawite, is so 

similar in physical properties to valleriite that it has 

evidently been the object of a great deal -of confusion. 

In this article we present new data for valleriite and 

descriptive data for a previ,ously undefined mineral 

which we call n1ackinawite; and we take note of the 

difficulties that have arisen from confusion of the two 

minerals. 

NEW DATA FO·R VALLERIITE 

We have not had available Blon1strand's type 

material from Nya Kopparberg, but our specin1en fron1 

1 Scripps Institution of Oceanography; work done in preparation of a thesis at 

Harvard University, Cambridge, 2\fass. 

Kaveltorp, described in detail by Odman (1933), is 

closely similar. The apparently homogeneous bronzy 

graphitic mineral gives a characteristic powder pattern, 

but attempts to obtain single-crystal patterns from 

tiny flakes yielded such poor information that a unit 

cell could not be deduced. Fortunately, new material 

of much better quality from Loolekop in northeast 

Transvaal, South Africa, recently became available to 

us through the courtesy of L. R. Page, of the U.S. 

Geological Survey. The mineral occurrence, in small 

pea-sized n1asses in carbonate rock associated with 

nther iron-copper sulfides, is quite like that of the 

Swedish mineral, but the crystal flakes are generally 

larger and better formed. The chemical composition 

is entirely analogous to that found for the Kaveltorp 

Inaterial, and to that given by Blomstrand (see table 

133.1), showing again the anomalous presence of about 

TABLE 133.1.-Chemical analyses of valleriite 

Constituent 

Cu ____________________ _ 

Fe ____________________ _ s _____________________ _ AhOa ____ --------------- MgO __________________ _ CaO __________________ _ K20 ___________________ _ 

N a20 ___ ----- -- -- ------- H2o ___________________ _ 

Insoluble + Si02- _- __ ---

TotaL ____ ----------

1 

17. 7 

26. 3 

22. 5 

5. 1 

10. 6 

0. 3 

0. 3 

0. 6 

10. 8 

Sample 

~-- 3 

17.6 19.8 

21. 2 20. 0 

21. 4 21. 6 

8. 1 8. 5 

16. 2 16. 0 

1.7 1.3 

12. 2 

1.8 

10.8 

3. 3 

94. 2 100. 2 101. 3 

4 

18. 6 

21. 1 

21. 3 

1. Nya Kopparberg, Sweden; Blomstrand (1870), from 5 

partial analyses. 

2. Kaveltorp, Sweden; Blanche Ingram, analyst; MnO, 0.5 

percent. 3. Loolekop, South Africa; Blanche Ingram, analyst; MnO, 

0.5 percent. 4. Theoretical for CuFeS2, corresponding to 61.0 percent of 

total. 

the same amount of aluminun1 and magnesium hydroxides together with iron, copper, and sulfur. The 

characteristic X-ray powder-diffraction pattern, shown 

in table 133.2, conclusively establishes the identity 

ART. 133 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D64-D69. 1964. 

D64 
EVANS, MILTON, CHAO, ADLER, MEAD, INGRAM, AND BERNER D65 

TABLE 133.2,_ X -ray powder-diffraction data for valleriite 

Calculated 1 Loolekop 2 KaveUorp_2 KaveUorp 3 

hkl ~ d(A, obs.) ! ~ !. ~ I 

00.3 11. 367 11. 39 10 11. 48 9 11. 5 10 00. 6 5. 683 5. 71 10 5. 68 10 5. 75 10 00. 9 3. 789 3. 80 5 3. 83 8 10. 1 3. 269 3. 27 6 3. 27 7 3. 29 10 10. 2 3. 225 3. 23 5 3. 23 8 10.4 3. 064 3. 07 2 3. 08 2 10. 5 2.959 2.958 1 2.974 1 

00. 12 2. 842 2. 846 5 2. 842 5 2. 87 8 10. 7 2. 723 

10. 8 2. 601 2. 604 1 

2. 531 3 2. 48 2 10. 10 2. 365 2. 346 2 ·2. 364 1 2.37 8 00. 15 2. 273 2. 275 6 2. 29 8 10. IT 2. 254 2. 259 2 

10. 13 2. 050 2. 041 2 2. 05 6 10. 14 1. 956 

11. 0 1. 896 1. 91 10 00. 18 1. 894 1. 885 5 1. 894 6 1. 90 10 11. 3 1. 870 1. 860 5 1. 870 5 1. 87 10 11. 6 1. 799 

10. 16 1. 788 1. 780 

10. I7 1. 712 

1 1. 794 1 1. 80 8 

11. 9 1. 696 

20. I 1. 640 

20. 2 1. 634 1. 636 1 1. 64 4 00. 21 1. 624 1. 629 1 1. 620 1 

20. 4 1. 612 

20. 5 1. 596 

11. 12 1. 577 

1. 59 6 

10. 19 1. 575 

20. 7 1. 556 

20. 8 1. 532 1. 526 1 1. 534 2 1. 54 6 

10. 20 1. 513 1. 52 2 

20. 10 1. 479 1. 485 1 1. 50 2 

11. 15 1. 456 1. 47 2 

20. 11 1. 451 

1. 23 2 

1. 22 3 

1. 14 4 

1. 09 4 

1. 06 6 

1. 04 10 

1. 03 10 

1. 01 10 

t Calculated for unit cell given in table 3. 2 Patterns made by the authors with FeKa radiation, camera diameter 114.6 mm. Intensities are on a geometric scale. a Data from Hiller (1939). 

of the South African and Swedish minerals. The 

powder-diffraction data given by Berry and Thompson 

(1962) for I{aveltorp valleriite agrees well with that 

obtained by us. 

Single flakes isolated from specimens from Loolekop, 

South Africa, were studied with the Buerger precession 

camera in an atternpt to obtain single-crystal diffraction 

patterns. The best photographs were readily interpreted in terms of a rhombohedral unit cell with the 

properties shown in table 133.3. The similarity in 

syn1n1etry and dimensions of the valleriite unit cell 

to that of the recently described iron sulfide, smythite, 

is striking and significant, although the character of 

diffraction-intensity distribution on the single-crystal 

patterns precludes any type of isostructural relationship. 

The crystallographic studies of Hiller (1939) are not 

supported by these findings. On the basis of powder 

TABLE 133.3.-Unit-cell data for valleriite, smythite, and 

mackinawite 

Mineral species 

Property Valleriite 1 Smythite.!_ Mackinawite 3 -----

Crystal sys- Rhombohedral Rhombohedral Tetragonal 

tern. 

Space group __ R3m or R3m R3m P4/nmm a (A) ________ 3. 792 ± 0. 005 3. 47 3. 673 ±0. 001 c lA) ________ 34. 10 ±0. 05 34. 5 5. 035 ± 0. 002 

Cell content 6CuFeS2 3Fe3S4 2FeS 

Density (X- 4. 26 4.09 4. 30 

ray). 

Density 3. 14 4.06 ------------ (measured). 

1 Loolekop, South Africa; unit cell derived from least-squares analysis of first 

12 d-spacings of data for Loolekop material, table 133.2; density from Blomstrand 

(1870). 

2 Bloomington, Ilfd.; Erd and others (1957). 3 Synthetic, Berner (1962); parameters derived by least-squares analysis of Berner's 

diffraction data as shown in table 133.4. 

data alone, which correspond well with ours (table 

133.2), he deduced an orthorhombic unit cell and even 

a crystal structure for valleriite. Evidently, his 

overextended hypotheses need not be further considered. 

The crystal structure of valleriite is not yet known, 

but its crystallography places severe restrictions on 

its constitution. Just as in smythite, the space-filling 

sulfur atoms must lie on the threefold symmetry axes, 

and the hexagonal unit cell is sufficiently large to 

contain three S4 units. Accordingly, the c axis length 

of 34.3 A corresponds to 12 layers of sulfur atoms in 

closest packing. Further, it is readily deduced that 

not less than 3 nor more than 4 cations also lie on the 

threefold axes. This reasoning leads us to the possible 

formulas: CuFe2S4, Cu2FeS4, and Cu2Fe2S4. The 

chemical analyses, apart from the magnesium and 

aluminum hydroxides, conform closely with the last. 

Thus it appears most probable that valleriite is a 

dimorph of chalcopyrite, CuFeS2. 

All single-crystal patterns of valleriite show the 

presence of a second, much weaker lattice originating 

from some other phase. This lattice is also rhombohedral, with a hexagonal a axis of about 3.0 A. Its 

smaller dimension corresponds well to that expected 

of an oxide compound of some sort. There is little 

doubt that this lattice is to be associated with the 

magnesium and aluminum hydroxides which have 

always appeared in chemical analyses of valleriite. 

Evidently these hydroxides correspond to a foreign 

mineral phase, hexagonal or rhombohedral in crystal 

character, interleaved in syntactical orientation on 

a submicroscopic scale with the valleriite. The identity 

of this foreign phase and its genetic relationship to 

valleriite ren1ain a mystery. 

MACKINAWITE 

Recently, Milton and Milton (1958) described the 

occurrence of a sulfide n1ineral from the Mackinaw 
D66 MINERALOGY AND PETROLOGY 

mine in Snohomish County, Wash., which they identified as . valleriite, n1ainly on the basis of its physical 

properties. The identification was tentative and the 

doubt which arose late in their study was ex~lained in 

a footnote: 

Preliminary studies in progress by C. Milton, E. C. T. Chao and 

H. T. Evans, Jr. indicate that the mineral identified as valleriite 

isT this paper is, in fact, distinct from the type valleriite from 

Kaveltorp, Sweden. The Mackinaw mineral is probably an 

undescribed iron sulfide, the Kaveltorp valleriite is perhaps a 

?opper-iron-magnesium sulfide. Probably both these phases, 

If not others also, are to be found among material from other 

localities that has been called valleriite. 

Both _vaiieriite and mackinawite are extremely anisotropiC and strongly reflection pleochroic. This feature is so outstanding that ore microscopists for many 

years have frequently labelled phases as "valleriite" 

on the basis of its anisotropism alone. We have 

observed that the pleochroism differs slightly between 

the two, valleriite appearing pale yellow to deep creamv 

brown (Skinner and Milton, 1955), while mackinawit~e 

shows a pale pink to pinkish gray color. 

The existence of a mineral different from valleriite 

was first definitely suspected when enough powder was 

successfully isolated from a chalcopyrite matrix bv 

means of an ultrasonic vibrating needle (Kehl and 

others, 1957) to obtain a characteristic X-ray diffraction 

pattern. The pattern showed that a large amount of 

chalcopyrite and a small amount of cubanite were 

still present in the sample, but when the characteristic 

reflections for these minerals were discounted 14 

reflections remained to be associated with the' new 

phase, as shown in table 133.4. These d-spacings bore 

no relation to those of valleriite. 

Examination of individual grains of the mineral in a 

polished section with an electron-microprobe apparatus 

by Birks and others (1959) showed that the copper 

content is very low and that the composition of the 

mineral is approximately FeS. This finding has been 

confirmed by new analyses with the electron-probe 

apparatus in our laboratory. Figure 133.1 (upper left) 

shows a polished section of ore from the Mackinaw mine 

containing feathered inclusions of n1ackinawite, which 

show as gray regions in the light-gray chalcopyrite 

matrix. Dark round spots indicate points probed by 

the electron beam and analyzed by X-ray spectroscopy. 

Copper was not detected, and on the basis of 16 determinations the following composition was determined 

by the authors: 

Fe ____________ _ Ni ____________ _ s _____________ _ 

Measured Theoretical 

(weight percent) (Feo.GoNio.MS) 

63±5 

3. 1 ±0. 5 

34±4 

60.5 

3. 0 

36.4 

The determinations were made by comparison with 

TABLE 133.4.-X-ray powder-diffraction data and unit-cell parameters for mackinawite 

Least- Synthetic 1 Mackinaw Outokumpo 3 "Kansite" 4 

squares mine2 ---- parameters: 5 ---- a ____ ------- 3. 673±0. 001 3. 675±0. 002 3. 6773±0. 003 c ____ ---------------... --· ---- 5. 035±0. 002 5. 030±0. 003 5. 021 i ±0. 0007 ---------------- hkl d(A,calc.)o d(A,obs.) I d(A,obs.) I d(A,obs.) I d(A,obs.) I ooL _____ 5. o3.s ~ 100 ~ 100 ~ VS ~ 50 10L _____ 2. 967 2. 97 80 2. 96 70 2. 966 s 2. 99 50 110 _______ 2. 597 2.60 20 2. 600 vw 002.. _____ 2. 518 111__ _____ 2. 308 2. 305 80 2. 31 90 2. 309 fl 2. 32 100 102 _______ 2. 077 200 _______ 1. 8365 1. 835 60 1. 838 50 1. 838 M 112 _______ 1. 8077 1. 805 80 1. 809 80 1. 806 s 1.80 100 201__ _____ 1. 7253 1. 723 60 1. 729 50 1. 726 M 1. 73 50 003__ _____ 1. 6784 1. 677 20 1. 674 w 21L _____ 1. 5616 1. 564 40 1. 564 20 1. 563 MW 1. 54 10 103 _______ 1. 5265 1. 527 20 1. 523 w 202 _______ 1.4837 1. 481 20 113 _______ 1. 4096 1.410 30 1. 410 30 1. 408 w 1. 42 30 212 _______ 1. 3757 220 _______ 1.2986 1. 298 50 1. 300 MW 1. 31 50 OOL _____ 1. 2588 1. 258 50 1. 257 22L _____ 1. 2574 35 1. 259 MW 1. 26 50 

203 _______ 1. 2389 1. 239 30 1. 237 30 1.238 w 104 _______ 1. 1908 1.190 10 1.191 vw 30L _____ 1. 1897 2]3 _______ 1. 1739 1.174 20 1. 173 vw 310 _______ 1.1615 222 _______ 1. 1541 llL _____ 1. 1327 1.133 50 1.132 35 1.133 MW 311 _______ 1.1318 

302__ _____ 1. 1010 

312 _______ 1. 0547 1. 055 80 1. 055 40 L055 MS 204__ _____ 1. 0383 1. 038 20 1.040 B 223 _______ 1. 0271 1. 027 B 005__ _____ 1. 0070 214_ ______ . 9991 . 9994 --13 32L _____ . 9985 303 _______ . 9891 

I Berner (1962). 2 Measured by E. C. T. Chao on material removed from chalcopyrite matrix with an ultrasonic needle; 13 reflections due to chalcopyrite and 5 due to cubanite are omitted. FeKa radiation, 114.6-mm-diameter camera. 3 Kouvo and others (1963). V=very strong, S=strong, M=medium, W=weak, B=broad. 4 Artificial product, measured by Meyer and others (1958); ASTM powder data file No. 7-26. < Unit-cell parameters and standard deviations calculated from the powder-diffrac- tion data by least-squares analysis. 6 d-spacings calculated for the unit cell found for Berner's synthetic FeS, assuming the space group P4jnmm. 

analyzed pyrite, pyrrhotite, and pentlandite as primary 

standards. Accuracy was limited by the small size 

of the grains, which are only a little larger than the 

electron beam, and the difficulty of obtaining quite 

plane surfaces on the relatively soft mackinawite. 

It is apparent that the determined composition is not 

significantly different from that corresponding to the 

formula, (Fe0• 96Nio. o4)S. 

The key distinguishing characteristic of this mineral, 

namely, its X-ray powder-diffraction pattern, was soon 

found to resemble that of an artificial iron sulfide 

labelled "kansite" by Meyer and others (1958). This 

substance was identified by its X-ray pattern in the 

corrosion product caused by the action of hydrogen 

sulfide on pipeline steel. It could not be isolated for 

ordinary chemical and physical tests, but it did yield 

a rather diffuse X-ray pattern of 10 measurable lines 

(see table 133.4). These matched approximately the 

recorded pattern for pentlandite, and Meyer and others 

derived from it a cubic unit cell with a=10.1 A. Following this lead, they suggested a composition of Fe9Ss 

for this phase, by analogy with pentlandite. Our 

X-ray data (table 133.4) showed a close relationship 
EVANS, MILTON, CHAO, ADLER, MEAD, INGRAM, AND BERNER 

FIGURE 133.1.-Polished section showing mackinawite from the Mackinaw mine, Snohomish 

County, Wash. The upper left view (plain light) 

shows cubanite (Cub in lower left drawing) as medium gray, chalcopyrite (Ch) as light gray, and 

the silicate gangue as black. The mackinawite 

in the chalcopyrite appears as dark-gray streaks 

that are brightly illuminated between crossed 

nicols, as shown in the upper right view. Four 

mackinawite areas probed by the electron beam are shown by p in the lower left drawing and as black-stained spots in the upper left view. 

D67 
D68 MINERALOGY AND PETROLOGY 

with "kansite," but on the other hand it was certain 

that the Mackinaw mine iron sulfide could not be cubic 

because of its high anisotropy in polished section 

(fig. 133.1, upper right). 

:Meanwhile, Kouvo and Vuorelainen (1959) published 

a short paper describing a new iron sulfide mineral 

resembling vallerite but distinct from it. They list 

the X-ray diffraction data obtained from this mineral, 

consisting of 23 lines (table 133.4) . These contain the 

lines found by us for the Mackinaw mineral and also, 

as they noted, for "kansite," as well as many other lines. 

They found the mineral in chalcopyrite assemblages, 

showing strong pleochroism and very strong optical 

anisotropy, quite analogous to the Mackinaw mineral. 

Evidently, Kouvo and Vuorelainen were able to prepare 

pure samples from which they could obtain sharper and 

stronger X-ray patterns than we have been able to get. 

Subsequently, evidence for the formation of an iron 

sulfide phase in the sediments of the Mystic River, 

Boston, Mass. was found by Berner (1962). He noted 

that this phase, as identified by its X-ray diffraction 

pattern, is the same as one which he prepared synthetically by the action at room temperature of an aqueous 

solution of H2S on reagent-grade iron wire in the absence 

of air. The pattern corresponds well with those of the 

Mackinaw mine and Outokumpo minerals, and "kansite." Berner discovered that all these patterns can be 

quite satisfactorily indexed on the basis of a primitive 

tetragonal unit cell with parameters which he gave as 

a=3.679±0.002 A and c= 5.0471±0.002 A. It was 

found that this crystallography closely resembled that 

described by Hiigg and Kindstrom (1933) for Fe~e, for 

which they determined the crystal structure. Berner 

further showed that a similar structure for tetragonal 

FeS yielded calculated diffraction intensities which 

agreed well with those observed for the natural and 

artificial iron sulfide phase. Thus, the key to the constitution of these phases is provided. 

Kouvo and others (1963) have now described their 

study of the new iron sulfide in detail, based on beautifully crystallized material associated with cubanite, 

pyrrhotite, and chalcopyrite from Outokumpo and other 

Finnish localities. Single crystals up to 1 mm in size 

allowed these authors to determine the unit-cell dimensions and symmetry by the Weissenberg method. 

They found a tetragonal unit cell in the probable space 

group P4/nmm, with parameters which they reported 

as a=3.676±0.002 A and c=5.032 A. 

Kouvo and others (1963) also were able to obtain 

good chemical and electron-probe analyses leading to a 

formulation (Fe0. 91Ni0. 13Co0 •007)S, with no Cu present. 

The slight departure from stoichiometry is also reminiscent of the behavior of other iron sulfide phases. The 

close correspondence between the chemical and physical 

data given by Kouvo and others for their "tetragonal 

iron sulfide" and those found by us for the Mackinaw 

material leaves no doubt that the two are the same 

mineral. We have named the mineral "mackinawite" 

in allusion to the locality name. Dr. Olavi Kouvo, who 

gave the first clear description of this new mineral 

(Kouvo and others, 1963), has generously agreed LO this 

choice of name. 

The X-ray powder-diffraction data given by Berner 

for synthetic iron sulfide and by Kouvo and others for 

the Mackinaw mine material are given in table 133.4. 

We have subjected all these data to least-squares analysis in order to find the best unit-cell parameters for each 

set. For this purpose we have used a new self-indexing 

computer program written for our Burroughs B220 digital computer, which extracts the standard deviations of 

the parameters from the inverse matrix of the normal 

equations based on the residuals of the measured _20 

angles. These unit-cell parameters and standard deviations are shown at the beginning of table 133.4. The 

result for Berner's data is given in table 133.3 to represent the pure FeS phase. The differences between the 

cell parameters as we found them and the published 

values are hardly significant. The variation in the three 

sets of cell parameters doubtless reflects the influence 

of the substitution of varying amounts of Ni for Fe, 

but the data available now are not sufficient to define 

this variation quantitatively. 

CONFUSION OF VALLERIITE AND MAC KINA WITE 

To the ore microscopist, the outstanding characteristic of both valleriite and mackinawite is their extreme 

anisotropism. Ramdohr and bdman (1932) in their 

restudy of Blomstrand's material evidently considered 

the evidence of this striking anisotropism to be more 

significant than the available chemical _informa_tion ~nd 

assumed on this basis that the material was IdentiCal 

with a mineral found by Schneiderhohn (1929) in the 

platinum-ore deposits of the Transvaal. In his careful 

studies Schneiderhohn noticed in sections of chalcopyrite and pentlandite, lamellar or irregular inclusions of 

a highly birefringent mineral, which he termed an 

"unbekanntes Nickelerz." Most important, he was 

able to isolate enough pure sample from a pentlandite 

matrix for a spectrographic analysis, which showed 

that the anisotropic mineral was primarily an ironnickel sulfide ~ith no detectable copper. All aspects 

of his descrip,tion match the properties of mackinawite 

as we now know them and it seems entirely probable 

that mackinawite is a~tually the mineral he describes 

in "Lehrbuch der Erzmikroskopie" (Schneiderhohn and 

Ramdohr, 1931), without mentioning the Swedish mineral, and without giving it a name. Ramdohr, in subse-
EVANS, MILTON, CHAO, ADLER, MEAD, INGRAM, AND BERNER D69 

quent editions of his "Die Erzmineralien" (Ramdohr, 

1960), combined the information about the South 

African and Swedish occurrences into one description 

under the name "V allerii t." Consequently, most subsequent descriptions of a soft sulfide mineral having 

extreme anistropism and occurring as fine inclusions 

in chalcopyrite or pentlandite have given it the name 

"valleriite," even though no other evidence was available to establish the identification. Thus, the numerous 

literature references to valleriite are ambiguous and 

could equally well apply to mackinawite. 

In conclusion, we believe that the occurrence in other 

sulfide crystals of tiny inclusions giving the appearance 

of an exsolution phase is quite characteristic of mackinawite and not valleriite, and that as this feature is 

usually mentioned in most literature references to "valleriite," probably what these references describe is actually 

mackinawite. Authentic valleriite, on the other hand, 

has been established from only two localities, Loolekop 

in South Africa, and southern Sweden. A probable 

third locality has been reported by Skinner and Milton 

(1955) at the Elizabeth mine, South Stratford, Vt. 

X-ray powder patterns of a soft highly birefringent 

sulfide mineral from this mine show reflections for 

chalcopyrite, pyrrhotite, and a third phase. The dspacings for this phase match those determined for 

Kaveltorp valleriite, and the data given by Hiller (1939). 

Kouvo and Vuorelainen (1959) also mention an occurrence of valleriite at Vihauti, Finland, verified by its 

diffraction pattern. The validity of any given occurrence of valleriite or mackinawite may evidently be established only by X-ray diffraction or electron-microprobe 

techniques. From what we know now, it appears that 

mackinawite is a common and widespread mineral, 

while valleriite is quite rare. 

REFERENCES 

Berner, R. A., 1962, Tetragonal iron sulfide: Science, v. 137, 

p. 669. 

Berry, L. G., and Thompson, R. M., 1962, X-ray powder data 

for ore minerals; The Peacock atlas: Geol. Soc. America 

Mem. 85, p. 61. 

Birks, L. S., Brooks, E. J., Adler, Isidore, and Milton, Charles, 

1959, Electron probe analysis of minute inclusions of a 

copper-iron mineral: Am. Mineralogist, v. 44, p. 974-978. 

Blomstrand, C. W., 1870, On some new Swedish minerals and the 

composition of pyrrhotite: Ofversigt af Kung!. VetenskapsAkademiens Fiirhandlingar (Stockholm), v. 27, p. 19-27. 

[In Swedish] 

Erd, R. C., Evans, H. T., Jr., and Richter, D. H., 1957, Smythite, 

a new iron sulfide, and associated pyrrhotite from Indiana: 

Am. Mineralogist, v. 42, p . 309-333. 

Hagg, G., and Kindstriim, A.-L., 1933, X-ray study of the system 

iron-selenium: Zeitschr. fiir physik. Chern., v. B22, p. 

453-464. [In German] 

Hiller, J. E., 1939, On the crystal structure of valleriite: Zeitschr. 

Kristallographie, v. 101, p. 425- 434. [In German] 

Kehl, G. L., Steinmetz, H., and McGonnagle, W. J., 1957, The 

removal of inclusions for analysis by an ultrasonic jackhammer: Metallurgia, v. 55, p. 151-154. 

Kouvo, Olavi, and Vuorelainen, Yrjii, 1959, On valleriite: 

Geologi, v. 11, p. 32-33. 

Kouvo, Olavi, Vuorelainen, Yrjii, and Long, J. V. P., 1963, A 

tetragonal iron sulfide: Am. Mineralogist, v. 48, p. 511-524. 

Meyer, F . H., Riggs, 0. L., McGlasson, R. L., and Sudbury, 

J. D., 1958, Corrosion products of mild steel in hydrogen 

sulfide environment: Corrosion, v. 14, p. 69- 75. 

Milton, Charles, and Milton, D .. J., 1958, Nickel-gold ore of the 

Mackinaw mine, Snohomish County, Washington: Econ. 

Geology, v. 53, p. 426- 447. 

Odman, 0. H., 1933, Ore-microscopic study of the sulfide ores of 

Kaveltorp: Geol. Fiirenings Fiirhandlingar, v. 55, p. 563-

611. [In German] 

Petren, J., 1898, On so-called valleriite : Geol. Fiirenings Fiirhandlingar, v. 187, p. 183-192. [In Swedish] 

Ramdohr, P ., 1960, Die Er zmineralien: Berlin, Akademie Verlag, 

p. 527-531. 

Ramdohr, P., and Odman, 0. H., 1932, Valleriite: Geol. Fiirenings Fiirhandlingar, v. 54, p. 8\J-98. [In German] 

Schneiderhiihn, Hans, 1929, The mineragraphy, spectrography 

and genesis of the platinum-bearing ni ckel-pyrrhotite ores 

of the Bush veld igneous complex; chap. 17 in Wagner, P. A., 

Platinum deposits and mines of South Africa: London, 

Oliver and Boyd, p . 206- 246. 

Schneiderhiihn, Hans, and Ramdohr, P., 1931, Lehrbuch der 

Erzmikroskopie: Berlin, Verlag von Gebriider Borntraeger, 

v. 2, p. 127-130. 

Skinner, B. J., and Milton, D. J., 1955, The Elizabeth copper 

!lline, Vermont-a discussion: Econ. Geology, v. 50, p. 

751~752. 
Article 134 

EDDIES AS INDICATORS OF LOCAL FLOW DIRECTION IN RHYOLITE 

By DAVID CUMMINGS, Denver, Colo. 

Work done in cooperation with the U.S. Atomic Energy Commission 

Abstract.-Eddies form on the downflow side of inclusions in 

rhyolite and indicate a single local direction of flow. The more 

commonly made observations of flow folds and lineations of 

phenocrysts in rhyolite indicate two possible directions of flow. 

Eddies or eddy zones develop on the downflow side 

of inclusions in rhyolite flows. Because a phenocryst 

or lithic inclusion has a greater inertia than the flowing 

lava, the inclusion moves more slowly than the surrounding fluid. Friction and drag result. The velocity of the lava is less on the downstream side of the 

inclusion than on the upstream side because part of 

the kinetic energy of the fluid particles is dissipated in 

overcoming resistance caused by shear stresses as the 

flow passes around the inclusion. As a result, the 

fluid particles are unable to flow completely around the 

inclusion. At some point beyond the center of the 

inclusion, fluid particles become momentarily static, 

accumulate, and are given a rotary motion by the 

surrounding flow (fig. 134.1). The pattern of the flow 

lines differs with differently shaped inclusions. If the 

long axis of a rectangular inclusion is not oriented 

parallel to the flow direction, the flow lines are offset 

slightly (fig. 134.2). 

The hypothetical outcrop shown on figure 134.3 

illustrates the determination of flow direction from eddy 

Direction of 

flow 

FrouRE 134.1-Development of eddies on the downflow side of an inclusion. 

FIGURE 134.2- An inclusion and eddy zone in a rhyolite flow. 

Top, eddy zone and inclusion as seen in outcrop; bottom, 

diagrammatic view of outcrop. Eddy zone to the left of the 

lithic inclusion indicates that the flow moved to the left. 

ART. 134 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D7Q-D72. 1964. 

D70 
CUMMINGS D71 

zones. As can be seen, the outcrop face need not be 

parallel to the direction of flow but should be no more 

than 45° from that direction. Eddy zones are most 

clearly seen in the devitrified parts of a lava flow but 

can also be seen in vitrophyres. 

The generalized geologic map (fig. 134.4) shows the 

inferred direction of movement of a rhyolite flow as 

determined by the direction of eddy zones. Flow 

foliation and lineation are also shown on the map. 

The eddy-zone directions are all northerly, ranging from 

about N. 45° W. to N. 30° E. The strike of the flow 

foliations is n1ost com1nonly east-west, and the trend 

of the lineations is generally north-south. The foliations and lineations suggest either a north or a south 

direction of flow. The eddy zones, however, indicate 

that the flow direction is northerly. 

/ 

20 Fiow-band •udace 

/f! 

FIGURE 134.3-Determination of flow direction by use of eddy zones. Dip of flow layer, 40°; plunge of lineation, 20°. Lineation shows that direction of flow is either northeast or southwest. Face A is almost normal to direction of flow and shows no eddy zone. Faces Band C show east and north components 

of flow direction. Direction of flow is northeast. 
D72 

116°30' 

Contact 

Dashed where appro:n:mately 

located 

D 

--u--········ 

Fault 

Approximately located. Dotted 

where concealed; U, upthrown s-ide; D, downthrown 

side 

MINERALOGY AND PETROLOGY 

0 

EXPLANATION 

20 

Strike and dip of 

flow foliation 

~ 

Strike of vertical flow 

foliation 

+ 

Horizontal flow foliation 

1 MILE 

Tr 

8 

~\ Tr 

-30 

Bearing and plunge of 

lineation 

Horizontal lineation 

Planar and linear symbols 

may be combined 

Flow direction -- of rhyolite, 

based on eddy zone 

I 

(.. 

\ 

FIGURE 134.4.-Flow direction of rhyolite, based on eddy zones, Scrngham Peak quadrangle, Nye County, 

Nev. Alluvium (Qal) is of Quaternary age; rhyolite (Tr), olcll'r volcanic rocks (Tvo), and younger 

volcanic rocks (Tvy) are of Tertiary age. Geology by David Cummings and F. M. Byers, Jr., 1962-63. 
Article 135 

CADMIUM IN SAMPLES OF THE PIERRE SHALE 

AND SOME EQUIVALENT STRATIGRAPHIC UNITS, GREAT PLAINS REGION 

By HARRY A. TOURTELOT, CLAUDE HUFFMAN, JR., and LEWIS F. RADER, Denver, Colo. 

Abstract.-The cadmium content of 84 samples (10 of bentonite, 

66 shale and claystone, and 8 marls tone) averages 1.4 ppm and 

ranges from <o.3 to 11.0 ppm. The median value of 0.8 ppm 

probably represents the cadmium content of the average shale. 

Some of the samples with high cadmium content contain relatively large amounts of organic matter which may serve as a 

collector for cadmium. Other high-cadmium samples, however, 

contain as little organic matter as most of the low-cadmium 

samples, suggesting that there may have been variation in the 

amount of available cadmium in the sea water in which these 

rocks were deposited. 

Data on the cadmium content of sedi1nentary rocks 

are very sparse. Preuss' (1941, p. 19) spectrographic 

analysis showing 0.3 parts per million of cadmiun1 in a 

composite sample of 36 shales from Gern1any is the 

basis for n10st estin1ates of the abundance of cadmiun1 

(Rankan1a and Sahama, 1950, p. 713; Turekian and 

Wedepohl, 1961, p. 184 and table 2). Mullin and Riley 

(1956) report cad1niu1n contents ranging frmn 0.39 to 

0.45 ppm for marine oozes. Cadmiun1 is concentrated 

in zinc sulfides (Fleischer, 1955, p. 992) and has long 

been known to be concentrated in coal ashes and black 

marine carbonaceous shales (Krauskopf, 1955, p. 417). 

The cadmium content is reported here for 10 san1ples 

of bentonite, 8 of madstone, and 66 of shale and 

claystone from the Pierre Shale, a thick and widespread 

n1arine unit of Late Cretaceous age in South Dakota 

and adjacent parts of Nebraska, Wyon1ing, and 

Montana. The samples come n1ostly from the Black 

Hills and Missouri River areas in these States. The 

samples were analyzed by H uffn1an using a method 

by which cadmimn is separated and concentrated by 

ion exchange before its spectrophotmnetric determin~­

tion with dithizone (Huff1nan, 1962). Under the 

conditions of the detenninations, 1 division on the 

transmission scale of the spectrophotometer is equal 

to 0.12 ppm cadmiunL The lower limit of detection is 

taken as 0.3 ppm, and the standard deviation for 

concentrations near 1 ppn1 is also about 0.3 ppm 

cadn1ium. 

Cadmium content was determined for two groups of 

samples. The first group consists of samples described 

by Tourtlelot (1962) in part of a reconnaissance 

investigation of the composition of the Pierre Shale. 

Table 135.1 shows the cadmium analyses for most of 

these samples for which other analytical data have been 

published. This group includes two sets of closely 

spaced samples representing weathering profiles 

(Tourtelot, 1962, p. 28-32); only the freshest samples 

are included in the statistical discussions that follow. 

The second group of samples analyzed for cadmium is 

from the Pierre Shale of South Dakota and parts of 

adjacent States and was selected for more detailed 

investigation than the first group. Stratigraphic, 

mineralogic, chemical, and spectrographic data for this 

group have been summarized by Tourtelot and others 

(1960). The cadmium content of both groups of 

samples is shown graphically in figure 135.1 and is 

included in the statistical treatment of all samples in 

which cadmium has been determined. 

The analytical methods, their precision, and the 

names of analysts determining the elements reported 

in this and other shale studies have been described by 

Rader and Grimaldi (1961) and Barnett (1961). The 

method for determining total carbon has been changed 

since some of the early analyses were made. Since 

the present method is more precise and has a lower 

limit for the total carbon determination of 0.05 percent 

C, all of the samples containing too little carbon for 

determination previously have now been analyzed, and 

certain other samples reanalyzed to make all the data 

comparable. The carbon data in table 135.1 should 

ART. 135 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D73-D78. 1964. 

D73 
D74 GEOCHEMISTRY 

TABLE 135.1.-Analyse.s for cadmium and forms of carbon 

[Cadmium analyses by Claude Huffman, Jr., carbon analyses by I. C. Frost. See 'J'ourtelot (1962) for rock analyses and spectrographic and chemical analyses for miner 

ronstituents in these same samples] 

Location Description 

CadCarbon (percent) 

Sample 

I 

mium Town- Forma- (ppm) Total Car- grgan- Section ship Range County State tlon Member Material carbon bonate IC car- carbon bon 

--------- CS711 _____ NW~31 1S N. 19 E. Fergus ____ Montana .. Claggett __ ------------------ Shale, black, soft_ _____________________ 0. 5 1.3 <0.03 1.2 CS72 I 2 __ - NW~31 1S N. 19 E ___ do __________ do _______ ___ do _______ ------------------ ____ do _________________________________ .5 1.4 <.03 1.4 cs7312 ____ NW~31 1S N. 19 E. ___ do __________ do _______ ___ do _______ ------------------ Shale, brownish-gray, flaky, hard ______ .s .s <.03 .s CS7412 ____ NW~4 31 1S N. 19 E. ___ do __________ do _______ ___ do _______ ------------------ Residual soillike weathering product_ __ 1.6 1.0 <.03 1.0 CS70 ______ 20 6 s. 23 E. Carbon ___ ___ do _______ _ __ do _______ ------------------ Shale, dark-gray, silty _________________ .5 1.6 1.3 .3 CS76. _____ NEH32 54 N. 67W. Crook _____ Wyoming_ Pierre Mitten __________ Shale, black, hard, flaky ______________ .5 1.5 <.03 1.5 

Shale. CSS6 ______ NW~41S 1S N. 30 E. Corson ____ South ___ do _______ Upper part of Shale, dark-gray, hard, flaky __________ .s 1.3 .5 .s Dakota Virgin Creek SE~ 29 CSS7 ______ 16N. 31 E. Dewey ____ ___ do _______ ___ do ____ _ ______ do __________ Shale, black, flaky ____________________ .s 1.1 <.03 1.1 

CSSL ----- SE~4 36 6N. 30 E. Stanley ___ do _______ ___ do _______ Verendrye _______ Claystone, dark-gray with brownish 1.0 1. 0 .05 1.0 cast. CSS2 2 _____ SE%36 6N. 30 E. ... do __________ do _______ ___ do _______ _____ do ____ ___ .do ______________________________ . __ .6 .9 <.03 .9 C883 2 _____ SE~ 36 6N. 30 E. ... do _______ ... do _______ ___ do _______ _ ____ do __________ Residual soillike weathering product__ .s 1.5 .07 1.4 CSS4 ______ SE~ 36 6N. 30 E. ___ do _______ ... do _______ ___ do _______ ____ .do ___________ Claystone, dark-gray with brownish .5 2.0 .5 1.5 cast. CSS5 ______ SE% 36 6N. 30 E. ... do _______ ... do _______ ___ do _______ _ ____ do ___________ Claystone, dark-gray to black; some .s 2.2 .7 1. 5 

silty layers. CS7S ______ 1 111N. sow. Hughes ___ ... do _______ ___ do _______ DeGrey _________ Claystone, black; some silt layers (core .s 1.1 <.05 1.1 

sample from 32.S ft). 

CS79_ ----- 1 111 N. sow. ... do _______ ... do _______ ___ do _______ Crow Creek _____ Marlstone, yellowish-gray, slightly .s 7. 5 6.6 .9 

sandy (core sample from 51.0 ft). CSSO ______ 1 111 N. sow. .•• do _______ •.. do _______ ___ do _______ Gregory _________ Claystone, black, bentonitic (core .s 1.1 .1 1.0 

sample from 66.S ft). 

CSSS __ ---- 17 104 N. 71 W. Lyman ____ ... do _______ ___ do _______ DeGrey _________ Claystone, dark-gray, bentonitic _______ 1.4 . 7 <.03 .7 C889 ______ 17 104 N. 71 w. ... do _______ ... do _______ ___ do _______ Crow Creek _____ Marls tone, creamy-gray--------------- 1. 2 5.3 4. 7 .6 CS90 ______ 17 104 N. 71 W. •.. do _______ ... do _______ ___ do _______ Gregory _________ Claystone, gray, highly bentonitic _____ 1. 5 1.1 .5 .6 CS9L .•••. 17 104 N. 71 w. 10.3 .03 ... do _______ ... do _______ ... do _______ Sharon Springs __ Shale, black, hard; rich in organic 3.5 10.3 matter. 

I Samples re.present a weathering profile from the center of a roadcut (CS71) into the coluvium and soil zone on the flank of the hill (CS74). 'I'he samples were taken about a foot above a tuffaceous siltstone bed, 1 to 2 inches thick, that could be traced into the colluvium. 2 Not included in statistical discussion of cadmium. 

+ 

+ 

+ 

+ + ~ 0 + 0 0 + + 

0:: 0 + + 5 0 + + +o UJ 0 0 + 0 + O++ [D 0 0 + 0 0 + 0 ++ +• ~ 0 0 0 0 • o •o• +· • ::> 0 0 0 • • 0 ••• 0 ++· + 0• o• z 0.1 0.2 0.3 0.4 0.5 1.0 2.0 3.0 4.0 5.0 10.0 

CADMIUM, IN PARTS PER MILLION 

FIGURE 135.1.-Distribution of cadmium in 84 samples of Pierre 

Shale. Triangles, bentonite; squares, madstone; circles, 

shale and claystone containing <0.5 percent organic carbon; 

crosses, shale and claystone containing 0.5 to 1.0 percent 

organic carbon; dots, shale and claystone containing > 1. 0 

percent organic carbon. Such samples containing less than 

0.3 ppm cadmium are plotted arbitrarily at 0.15 ppm, half 

of the lower limit of detection. 

be substituted for those shown previously by Tourtelot 

(1962, p. 57). 

Currently, total carbon is determined by burning a 

weighed sample at 1350°C in a stream of oxygen. 

Iron chips and tin metal act as burning accelerators 

and catalysts, the evolved gases being passed through 

manganese dioxide and hot copper oxide to remove 

sulfur and to convert carbon monoxide to carbon 

dioxide. The volume of the gas, collected in a closed 

system under standard conditions of temperature and 

pressure, is measured; then the gas is scrubbed with 

potassium hydroxide solution to remove the carbon 

dioxide, and the volume is redetermined. Total carbon 

is calculated, carbon dioxide from carbonates determined separately is subtracted, and the remainder 

reported as organic carbon. 

The 10 samples of bentonite studied represent beds 

throughout the section of the Pierre Shale; 4 of these 

samples are of beds of practically the same age. The 

8 madstone samples include 3 from the Crow Creek 

Member in the lower-middle part of the Pierre Shale, 

and 5 from the Mobridge Member in the upper part of 

the Pierre Shale in the Missouri River area of South 

Dakota. The 66 samples of shale and claystone represent rocks throughout the Pierre Shale and equivalent 

stratigraphic units; these samples are grouped for convenience according to organic-carbon content: <o.5 

percent (19 samples), 0.5 to 1.0 percent (26 samples), 

and > 1.0 percent organic carbon (21 samples). Of the 

samples containing > 1.0 percent organic carbon, 14 

come from the Sharon Springs and Mitten Members 

in the lower part of the Pierre Shale and from the 

Claggett Shale, which make up a relatively thin unit 

of generally organic-rich shale of the same age from 

South Dakota to central Montana. 

CADMIUM CONTENT 

The statistical distribution of cadmium according to 

rock type is shown in figure 135.1 and, with other data, 

is sun1marized in table 135.2. The cadmium content 

of all samples ranges fron1 <o.3 ppm to 11.0 ppm and 

averages 1.4 ppm. Sa1nples reported with <o.3 ppm 

of cadmium, the lower limit of detection, are arbitrarily 
TOURTELOT, HUFFMAN, AND RADER D75 

assmned to contain 0.15 ppm. The graphic distribution 

(fig. 135.1) shows, however, that the average is too 

much influenced by the few high values to represent the 

expectable cad1niun1 content of clayey rocks. The 

modal value of 0.8 ppm cad1niun1, which is the median 

value (table 135.2), seems to be a more reasonable 

figure. 

TABLE 135.2.-Cadrniurn, zinc, total sulfur as sulfur, organic 

carbon, and vanadiurn in groups of sarnples 

[Values reported as less than respective. limits of detection are as counted half the limit 

of detection in calculating averages. Number of samples shown in parentheses] 

Shale and claystone, grouped 

All Benton- by organic carbon content Marlsamples ite stone <0.5 0.5-1.0 >LO 

percent precent percent 

(84) (10) (8) (19) (26) (21) 

------------ Cadmium (ppm): Range ___________ <0.3-11.0 0. 5-11.0 0. 4-10.0 <0.3-0. 8 <0.3-1.8 0. 5-8.4 Average _________ Median 1.4 2. 8 2. 6 .35 .8 2.0 __________ .8 . 8-.9 .9 .3 . 7-.8 1.2 Zinc (ppm): Range ___________ 38-380 38-330 60-210 65-190 90-360 37-380 Average_-------- Median 138 110 130 128 163 140 __________ ----------- 62-65 150 130 165 130 Total sulfur as sulfur (per- cent): Range ___________ <.1-13. 5 <.1-3. 2 <.1-2.1 <.1-.4 <.1-.9 <.1-13. 5 Average _________ Median .8 .9 .99 .2 .4 2.1 __________ ----------- .4 .9 .1 .4 1.2 Organic carbon 

(percent): Range ___________ <. 2-10.3 <.2 <.2-2. 9 . 2-.4 .5--1.0 1. 1-10.3 Average _________ Median 1.4 ---------- 1.5 .3 .8 3. 5 __________ ----------- .9 .3 . 7-.8 3.1 Vanadium (ppm): Range ___________ 50-740 20-580 I 70-380 2 50-300 3 310 3130-740 Average _________ 214 100(4 42) 200 170 200 390 Median __________ ----------- 40 210 170 210 390 

1 Excluding 2 samples for which only semiquantitative spectrographic analyses are available. 2 Excluding 1 sample for which only semiquantitative spectrographic analyses are available. 

a Excluding 5 samples for which only semiquantitative spectrographic analyses are available. 4 Average, excluding high value of 580 ppm. 

The average composition of 17 samples of Pierre 

Shale discussed by Tourtelot (1962, p. 37-44, 67) is very 

similar to that of several other average shales, mostly 

of pre-Cretaceous age (Clarke, 1915, p. 23; Vinogradov 

and Ronov, 1956, p. 6, 7; and others). The differences 

between these and the published averages are chiefly 

in alumina, silica, and potassium. The differences in 

silica and alumina reflect the variable admixtures of 

quartz and clay typical of such rocks; the lower potassium content of the Pierre Shale is attributable to the 

greater abundance in it of montmorillonite relative to 

potassium-rich clays. Data from the Pierre Shale thus 

are applicable to problems of average composition. 

These 17 sa~nples provided 15 of the samples analyzed 

for cadmium (table 135.1). The average cadmiun1 

content of these 15 samples is 1.1 ppm and the median 

value is 0.8 ppm. 

Many uncertainties surround selection of an average 

value for the content of any element in shale. Clearly, 

there is much rock in the Pierre Shale that contains 

71'6-626 0-64--6 

<0.3 ppm cadmium, and the analysis of additional 

samples of Pierre Shale and of other shales, particularly 

those with low organic content, no doubt would lower 

the n10dal value. It is probably unlikely that any 

rocks in the Pierre contain n1ore than about 10 ppm 

cadn1ium, although other black shales for which analytical data were published by Davidson and Lakin 

(1961, 1962) contain as 1nuch as 300 ppm cadmium, as 

determined by semiquantitative spectrographic analysis (D. F. Davidson, oral comn1unication, March 1963). 

Cissarz (1930, p. 64) also reports spectrographic analyses of 100 to 1,000 ppm cadmium in parts of the Mansfeld Kupferschiefer in Germany. Such high values, 

even though they are typical of a special kind of shale, 

must be taken into account as well as the low values. 

No rational basis for doing so, however, is apparent, 

and the median and 1nodal value of 0.8 ppm cadmiu1n 

derived from the Pierre samples seems to be an acceptable and usable average content for shale until 

much 1nore work has been done. 

RELATION TO OTHER CONSTITUENTS 

All statistical n1easures of the cadmiun1 content of 

the samples increase as the organic carbon content 

increases, but the relation is a general one (fig. 135.1 

and table 135.2). Most of the bentonite and n1arlstone 

samples contain 1.0 ppn1 cadmimn or less, but 2 of each 

contain >5.0 pp1n cadmium. The organic-carbon 

content of bentonite is negligible, being less than the 

arbitrary cutoff of 0.2 percent for the peroxide-bomb 

analytical method (Rader and Grimaldi, 1961, p. 37). 

Hence, cadmium in the bentonite sa1nples is independent of organic-carbon content. The 2 samples 

of madstone that contain the most cadmium each 

contain 2.0 percent or more organic carbon, but 1 

other san1ple of madstone that contains >2.0 percent 

organic carbon contains only 0. 7 ppn1 cadmium. 

Thus, cadmium in madstone may be related to organic 

carbon, but the relation is not evidently a genetic one. 

The organic ·carbon in the Pierre sam pies is similar 

in composition to lignite or subbituminous coal and 

is inferred to be derived largely from land plants 

(Breger and others, 1960; see also Breger and Brown, 

1962). Cadmium and other metals in the Pierre 

organic-rich samples may be original constituents of 

the plants, derived frmn their growing sites, or the 

metals n1ay have been adsorbed by the plant n1aterial 

fron1 the sea water during the transport, accumulation, 

and diagenesis of the plant material in the Pierre rocks. 

Each of these explanations has been advanced for 

1netals in coal and marine carbonaceous rocks, and it 

seems likely that both could be operative. The data 

on the Pierre samples are not helpful in identifying 
D76 GEOCHEMISTRY 

which mode of origin may have played the largest role 

in controlling the accumulation of cadmium. 

The zinc/cadmimn ratio plotted against the zinc content (fig. 135.2) has been used to divide the sa1nples into 

500 

400 

300 f~~~ 8.4 

.o. . 

• '7.0 

200 

z 

0 

::i 

::::! 

:::E 

0:::100 

w 

ll. 

(/) 

f-0::: 

<( 

ll. 

~ 

<.5 

z 

N 

50 

40 

30 

20 

10 

10 

10.0° 0

6.5 

'3.5 

'3.5 

,2.1 

• 1.6 

20 30 40 50 

!' 

• 

•• 

l1 + 

+ + 

.I . +' • .f. j + 0+ + +_. + • + 

•o +.o. ++ o+~ + o+o +I 

• 0 0 

o.llit +-+-0 I 0 0 

0 • 0 

+crustal 

abundance 

100 200 300 500 1000 

ZINC/CADMIUM RATIO 

FIGURE 135.2.-Relation between the zinc/cadmium ratio and 

zinc content of the Pierre Shale. Numbers on svmbols show 

cadmium content, in parts per million. Triangles, bentonite; 

squares, marlstone; circles, shale and claystone containing 

<0.5 percent organic carbon; crosses, shale and claystone con- taining 0.5 to 1.0 percent organic carbon; dots, shale and claystone containing > 1.0 percent organic carbon. 

two groups-one with ratios of <so and the other with 

ratios of >so. The zincjcadmiun1 ratio of the earth's 

crust is 270, using 0.15 ppm for cadn1ium (Brooks and 

Ahrens, 1961, p. 112) and 40 pp1n for zinc (Wedepohl, 

1953, p. 94). Both zinc and cadmimn are concentrated 

in nwst samples of Pierre Shale considerably above their 

crustal abundance. The group with ratios less than 50 

includes the 9 samples of bentonite, marlstone, and 

organic-rich shale with a cad1nium content of 2.0 ppn1 

or more. The remaining sample contains 1.6 ppm cadmium. The ratio of zinc to cadmiun1 is relatively eonstant, and the cadmiun1 content is related directly to the 

zinc content. 

Results of semiquantitative spectrographic analyses 

show that zincjcadmimn ratios of 10-30 are conunon for 

black-shale samples which contain as much as 1,000 

ppm zinc (D. F. Davidson, oral connnunication, March 

1963). 

In the group with ratios of >so, the eadmimn content 

ranges fr01n <o.3 pp1n to only 1.8 ppm, and the zinc/ 

cadmiu1n ratio increases in direct proportion to the zinc 

content. A subgroup of nine samples lies somewhat 

above the main trend but parallel to it. The cadmium 

content of these 9 samples ranges fr01n 1.5 to 1.8 ppm, 

whereas the main trend includes only a few samples that 

eontain > 1.0 ppm cadmium. 

These relations suggest that where the cadmium content is more than about 2 ppm, it is directly proportional 

to the zinc content at a relatively uniform ratio. Where 

the cadmium content is less than about 2 ppm, it does 

not vary systematically with zinc content and tends to 

be rather uniform in amount while the zinc content 

fluctuates. 

These relations may mean that (1) the proportions of 

cadmium and zinc in sea water varied at the depositional 

sites, either because of different amounts delivered to 

the sea water from source areas or because of the chemical composition of the sea water itself, or that (2) the 

conditions under which the sediments accumulated 

varied in controlling the fixation of both cadmium and 

zinc. For example, the stronger chalcophile tendencies 

of cadmium at low and moderate temperatures in acid 

solutions, compared with those of zinc (Goldschmidt, 

1954, p. 269), may account for the enrichment of cadmium in the organic-rich shales, which are also rich in 

syngenetic sulfide minerals. These tendencies may 

even account for enrichment of cadmium in marlstone. 

Samples that contain sulfide minerals, but only relatively small amounts of cadmimn, may have accumulated where there was little cadmium in the environment, or the sulfide n1inerals n1ay be late diagenetic to 

sec:_ondary in origin and thus have had no chance to 

reflect the cadmiun1 content of the environn1ent as a 

whole. 

The high cadmiun1 content and low zinc/cadmium ratio 

of both bentonite and black shale in a single widespread stratigraphic unit suggest that these cOinpositional features have a c01nmon origin. The generally 

low zinc/cadmium ratios of the bentonites studied here 

may be interpreted as reflecting the original relations 

of zinc and cadmiun1 in the volcanic n1aterial that was 

altered to fonn the bentonite. The bentonites that 

accumulated on the botton1 of the Pierre sea hundreds 

of n1iles east of the source of the volcanic n1aterial in 

Montana (Tourtelot~ 1962, p. 10-11) 1nust represent 

onlv a fraction of the total a1nount erupted. Bentonitic n1aterial is also abundant in the shales, as indicated by high n1ontlnorillonite content. Much of 

the total eruption produet accmnulated on land, but 

much also must have been n1oved aerially into the sea, 

along with whatever volatile substances ace01npanied 

the eruptions. The n1etal content of the sea water 

could be increased by solution of the volatile substances and the ele1nents in the disse1ninated volcanic 

material. The elements then would be adsorbed by 

organic 111atter and by clay 1ninerals that the1nselves 

were partly the result of alteration of the volcanic 

material. The volcanic material in discrete beds that 
TOURTELOT, HUFFMAN, AND RADER D77 

altered to bentonite would either retain its minorelement content, or lose it to sea water, depending on 

the nature of the alteration process. Cadn1iu1n and 

zinc thus were available in the sea water at a tilne 

when organic rnatter was abundant enough to participate directly in adsorption reactions or to rnake possible the forn1ation of syngenetic sulfides by generally 

reducing the oxidation potential of the bottom sediments. The volcanic material did not necessarily 

contain more cadmium and zinc than volcanic n1aterial 

delivered at other times to the Pierre sea. 

Zinc, total sulfur as sulfur, organic carbon, and vanadium (table 135.2) have n1uch the same distribution 

pattern among the rock types that cadrnium has, and 

statistical correlations between n1any of them are positive and significant. This is not surprising, of course, 

because most past work has shown the co-enrichment 

of these elements in similar rocks. The mode of 

occurrence of these elernents in such rocks still is 

largely unknown, so that the explicit factors that 

operated to produce at one place a sulfide-rich organicrich rock with a relatively high content of cadmium and 

other elements, and at another place a silnilar rock 

with little cadmium, also are unknown. Variations 

from place to place of temperature, pressure, pH, and 

oxygen potential obviously would affect, directly or indirectly, the amount of cadmiun1 that would be incorporated 

in clayey rocks. Such factors were different for a site 

where marlstone was deposited, compared to one 

where a sulfide-rich shale was deposited, yet the cadmium contents of some samples of such rocks are 

similar. At the same time, the cadmiun1 contents of 

organic-rich shales differ considerably, and yet the 

enumerated factors, excepting oxygen potential, rnust 

have been of nearly the same order of magnitude during 

the deposition of the sediments represented by the 

samples. Consequently, other variable factors also 

must have been operating. 

RELATION TO STRATIG'RAPHIC AND GEOGRAPHIC 

POSITION 

Eight of the 10 samples with the highest cadmium 

content and a zinc/cadmium ratio of <so include 

2 samples of bentonite and 6 of organic-rich shale from 

the Sharon Springs Member in the lower part of the 

Pierre Shale. These samples are fron1 widely scattered 

localities in the lower part of the Missouri River valley 

in South Dakota and the southern part of the Black 

Hills in South Dakota and Wyon1ing. One sample 

comes from the Irish Creek well (Tourtelot and Schultz, 

1961), almost halfway between the Black Hills and the 

Missouri River. The high cadmium content of the 

two bentonite samples rr;ny be related to the stratigraphic association of high-cadmiurn organic-rich shale 

and bentonite in the Sharon Springs Member. No 

regularity in relative position of samples with high 

cadmium content in the shale and in the bentonite can 

yet be seen-the high-cadmium shale may be either 

above or below the high-radrnium bentonite. Two 

additional samples of bentonite from the Sharon 

Springs have a cad mimn content of 0.6 and 0.8 pprn 

and a zinc/cadrnitml ratio of only 70. Relatively low 

zinc/cadmiurn ratios seern characteristic of bentonites 

from other units, too, all having a ratio of less than 

about 100. 

The two marlstone san1ples with a high cadmium 

content and low zinc/cadmium ratio are from the 

Mobridge Member in the upper part of the Pierre Shale. 

They suggest the possibility that there were local areas 

in the Pierre sea in which the content of cadmium and 

other metals was higher than elsewhere during the san1e 

span of time. The samples are frmn localities about 

35 miles apart, in southeastern Gregory County, 

S.Dak., and Knox County, Nebr. These two sarnples 

also contain relatively large amounts of rnolybdenum, 

seleniun1, and arsenic that, like cadmiun1, cannot be 

explained on the basis of what is known of the geochemistry of these elements in carbonate-rich rocks. 

Three other marlstone samples fron1 the Mobridge 

Mernber at localities 50 miles or more northwest of 

Gregory County contain less than 1 ppm cadrnium, 

and 6 samples of the same age but from a noncarbonate 

facies also have a low cadmimn content. The mineralogical composition of these and other samples from the 

upper part of the Pierre Shale in this part of the 

Missouri River valley in southern South Dakota and 

adjacent parts of Nebraska differs frorn sarnples of 

rocks of the sa1ne age at other localities in a way that 

suggests that son1e of the rnaterials were derived from 

land areas bordering the Pierre sea on the east. It is 

possible that the high cadmium content of the two 

marlstone san1ples reflects unusual arnounts of cadmiun1 

and other elernents in the sea water in this area during 

the latter part of Pierre tirne. The metals rnay have 

come frorn the eastern shore area, although no discrete 

sources for thern are known. The metals could also 

have become locally concentrated in the water of the 

Pierre sea by physical and chernical processes of oceanic 

circulation after having been derived frorn sources west 

of the Pierre sea. Although they are unsatisfying, 

such speculations are about all that the present data 

permit. Bur'yanova (1960, p. 217) also postulates 

unknown metal-rich source areas for the cadmiun1 

n1inerals and camouflaged cadmium in Devonian 

sandstones in Tuva, south-central Siberia. 
D78 GEOCHEMISTRY 

SUMMARY 

The cadn1ium content of 84 samples (10 of bentonite. 

66 shale, and 8 madstone) averages 1.4 ppn1 and 

ranges from <0.3 to 11.0 ppm. The median value of 

0.8 ppm probably represents the cadmimn content of 

the average shale. 

Cadmium tends to be concentrated in the san1e pattern as sulfur and vanadium in rocks of the Pierre Shale 

rich in organic carbon. Much of the cadn1imn in such 

rocks may be in syngenetic sulfide minerals. Bentonite 

that contains no organic carbon itself but which is 

associated with organic-rich shale also may contain 

relatively large amounts of cadmiuln. High-cadlnimn 

samples of bentonite and organic-rich shale are from 

the Sharon Springs Member at widespread localities. 

The close geographic association of two high-cadn1iun1 

samples from the Mobridge Member in southern South 

Dakota and adjacent Nebraska n1ay indicate that 

locally the sea in this area was enriched in cadmium 

and other metals during the deposition of the Mobridge 

Member. 

REFERENCES 

Barnett, P. R., 1961, Spectrographic analysis for selected mi~or 

elements in Pierre shale: U.S. Geol. Survey Prof. Paper 

391-B, p. B1-BIO, 13 figs. 

Breger, I. A., and Brown, Andrew, 1962, Kerogen in the Chattanooga Shale: Science, v. 137, no. 3525, p. 221-224. 

Breger, I. A., Tourtelot, H. A., and Chandler, J. C., 1960, Geochemistry of kerogen from the Sharon Springs Member of 

the Pierre Shale: Geol. Soc. America Bull., v. 71, no. 12, pt. 

2, p. 1832-1833. 

Brooks, R. R., and Ahrens, L. H., 1961, Some observations on 

the distribution of thallium, cadmium and bismuth in silicate rocks and the significance of covalency on their degree 

of association with other elements: Geochim. et Cosmochim. 

Acta, v. 23, p. 100-115. 

Bur'yanova, E. Z., 1,960, Mineralogy and geochemistry of cadmium in the sedimentary rocks of Tuva: Geokhimija, no. 2, 

p. 177-182 [in Russian]: translation in Geochemistry, 1960, 

no. 2, p. 209-217. 

Cissarz, Arnold, 1930, Quantitative-spektralanalytische Untersuchung 

eines Mansfelder Kupferschieferprofiles: Chemie d. Erde, v. 

5, (Linck-Festschr.) p. 48-75. 

Clarke, F. W., 1915, Analyses of rocks and minerals from the 

laboratory of the United States Geological Survey, 1880 to 

1914: U.S. Geol. Survey Bull. 591, 376 p. 

Davidson, D. F., and Lakin, H. W., 1961, Metal content of .some 

black shales of the Western United States: Art. 267 in U.S. 

Geol. Survey Prof. Paper 424-C, p. C329-C331. 

--- 1962, Metal content of some black shales of the western 

conterminous United States, pt. 2: Art. 85 in U.S. Geol. 

Survey Prof. Paper 450-C, p. C7 4. 

Fleischer, Michael, 1955, Minor elements in some sulfide minerals, in pt. 2 of Bateman, A. M., ed., Economic Geology, 

50th anniversary volume, 1905-55: Urbana, Ill., Econ. 

Geology Pub. Co., p. 970-1024 

Goldschmidt, V. M., 1954, Geochemistry: London, Oxford Univ. 

Press, 730 p. 

Huffman, Claude, Jr., 1962, Ion-exchange separation and spectrophotometric determination of cadmium: Art. 214 1:n U.S. 

Geol. Survey Prof. Paper 450-E, p. E126-E127 [1963]. 

Krauskopf, K. B., 1955, Sedimentary deposits of rare metals, in 

pt. 1 of Bateman, A. M., ed., Economic Geology, 50th anniversary volume, 1905-1955: Urbana, Ill., Econ. Geology 

Pub. Co., p. 411-463. 

Mullin, J. B., and Riley, J. F., 1956, The occurrence of cadmium 

in seawater and in marine organisms and sediments: Jour. 

Marine Research, v. 15, no. 2, p. 103-122. 

Preuss, E., 1941, Beitrage zur spektralanlytichen Methodik. II. 

Bestimmung von Zn, Cd, Hg, In, Tl, Ge, Sn, Pb, Sb, Bi 

durch fraktionierte Destillation: Zeitschr. angew. Mineralogie, v. 3, p. 8-20. 

Rader, L. F., and Grimaldi, F. S., 1961, Chemical analyses for 

selected minor elements in Pierre Shale: U.S. Geol. Survey 

Prof. Paper 391-A, p. A1-A45, 19 figs. 

Rankama, Kalervo, and Sahama, Th. G., 1950, Geochemistry: 

Chicago, Chicago Univ. Press, 912 p. 

Tourtelot, H. A., 1962, Preliminary investigation of the geologic 

setting and chemical composition of the Pierre Shale, Great 

Plains region: U.S. Geol. Survey Prof. Paper 390, 74 p. 

Tourtelot, H. A., and Schultz, L. G., 1961, Core from the Irish 

Creek well, Ziebach County, South Dakota: U.S. Geol. Survey open-file report, 20 p. 

Tourtelot, H. A., Schultz, L. G., and Gill, J. R., 1960, Stratigraphic variations in mineralogy and chemical composition 

of the Pierre Shale in South Dakota and adjacent parts of 

North Dakota, Nebraska, Wyoming, and Montana: Art. 

205 in U.S. Geol. Survey Prof. Paper 400-B, p. B447-B452. 

Turekian, K. K., and Wedepohl, K. H., 1961, Distribution of the 

elements in some major units of the Earth's crust: Geol. Soc. 

America Bull., v. 72, p. 175-192. 

Vinogradov, A. P., ap.d Ronov, A. B., 1956, Composition of sedimentary rocks of the Russian platform in relation to the 

history of their tectonic movements: Geokhimiya 1956, no. 

6, p. 3-24 [In Russian; translation in Geochemistry, 1956, 

v. 6, p. 533-559].· 

Wedepohl, K. H., 1953, Untersuchungen zur Geochemie des 

Zinks: Geochim. et Cosmochim. Acta., v. 3, p. 93-142. 
Article 136 

ANALYSIS OF GEOCHEMICAL PROSPECTING DATA 

FROM THE ROCKY RANGE, BEAVER COUNTY, UTAH 

By J. J. CONNOR and A. T. MIESCH, Denver, Colo. 

Abstract.-A spatial relation has been found between copper 

in alluvium and a copper ore body 20 to 225 feet beneath the 

surface. The relation became clear through statistical procedures used to reduce the effects of local variation and area-wide 

trends. 

Methods of trend analysis used in interpretations of 

geophysical data (Grant, 1957, p. 309; Oldhmn and 

Sutherland, 1955, p. 295) and applied to geologic problems by Krumbein (1956, p. 2163; 1959, p. 823), Whitten 

(1959, p. 835), and others have not been adequately 

tested for their applieation to data-interpretation problems in geochernical prospecting. This article presents 

the results of such an application. 

The geochen1ical data used in this study were collected by Erickson and Marranzino (1960, p. B98) in 

the Rocky Range of southwestern Utah and consist of 

110 chemical analyses for trace amounts of copper in 

samples of pediment alluvium. The samples were collected on approxiinately 100-foot centers and were taken 

at a depth of 8 to 12 inches below the surface. The 

sampled area overlies a small copper ore body which 

lies at a depth of 20 to 225 feet below the surface. 

The alluvium over the ore body ranges from 6~ to 45 

feet in thickness. 

Trend analysis, and analysis of variance tests of the 

trends, show statistically significant lateral variations 

in the data that can be described by low-order polynomial surfaces, but small-scale local variation (probably due to sampling error) obscures subtle features of 

the data important to geochemical prospecting. These 

subtle features are brought out by applying a "moving 

average" operation (which serves to reduce randon1 

local variation) in conjunction with the ordinary methods of trend analysis. 

Figure 136.1 is a map of the sampled area showing 

devi~tions of the copper values from their n1ean and is 

equivalent to figure 47.1 of Erickson and Marranzion 

EXPLANATION 

Copper content 

More • than 25 

parts per million 

25 to -25 

parts per million 

§ 

Less than -25 

parts per million 

• 

Mineralized 0 500 FEET core hole 

UTAH 

~Area of 

report 

Sampled 

locality 

FIGURE 136.1-Copper content of alluvium in the Rocky Range, Utah 

(contoured on deviations from the mean). Contour interval 25 ppm; 

values larger than 100 ppm and smaller than -100 ppm not contoured. 

Modified from Erickson and Marranzino (1960). 

ART. 136 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D79-D83. 1964. 

D79 
D80 GEOCHEMISTRY 

(1960, p. B99). The ore body is roughly outlined by 

the black dots, which show locations of 1nineralized 

drill holes. There is no obvious spatial relation of 

copper values at the surface to ore, a conclusion also 

reached by Erickson and Marranzino. Cursory examination of figure 136.1, however, reveals that, in 

general, the copper content tends to be high on the east 

side of the n1ap and low on the west. 

relative sense, at least, to judge the degree of fit for 

verious trends. Signifieanee levels for the F ratios 

should be viewed cautiously. 

Analysis of variance of polynomial surfaces fitted to the data of 

figures 136.1 and 136.3 

[Fo.gs (2,107) =3.09; Fo.95 (3,104) =2.70; Fo.95 (4,100) =2.46; Fo.gs (5,95) =2.31; Fo.95 (6,89) = 2.20; Fo.95 (7,82) =2.12; Fo.95 (8, 74) =2.06) 

Using methods of trend analysis, described fully in 

papers previously cited, seven polynomial surfaces 

were fitted by least-square techniques to the data of 

figure 136.1. Four of these surfaces or trends, of 

degree 1 through 4, and deviations from the trends, are 

shown in figures 136.2A-D. The deviations identify 

variance in the data that cannot be described by loworder polynomial equations, and is ascribed to local 

effects, in part geologic factors that do not act in a continuous fashion across the entire area of investigation. 

Some part of the variance of the deviationB is due to 

analytical error and possibly other nongeologic factors. 

Original data Movingaverage 

data 

Analysis of varianee tests of the computed trends 

are given in eolumns 1 through 4 of the accompanying 

table. Deviations of observed data from the trends 

were not tested for fit to a normal curve or for degree 

of independenee, but the F ratios n1ay be used in a 

The proportions of the total sum of squares accounted 

for by the linear through quartic trends (see table, 

first colu1nn) amount to 16, 23, 26, and 40 percent, 

respeetively. Though the F ratios suggest that the 

A. LINEAR TREND AND DEVIATfONS FROM LINEAR TREND 

C. CUBIC TREND AND DEVIATIONS FROM CUBIC TREND 

EXPLANATION 

0 

Copper content 

More • than 25 

parts per million 

25 to -25 

parts per million 

Less 

~ than -25 

parts per million 

• 

Mineralized 

core hole 

Sampled 

locality 

N 

I FEET 

500 

B. QUADRATIC TREND AND DEVIATIONS FROM QUADRATIC TREND 

D. QUARTIC TREND AND DEVIATIONS FROM QUARTIC TREND 

FIGURE 136.2-Trends (dashed line), in parts per million, and trend deviations of copper in alluvium, Rocky Range, Utah. 

Contour intern.! 25 ppm; values larger than 100 ppm and smaller than -100 ppm not contoured. 
CONNOR AND MIESCH D81 

linear, quadratic, and quartic trends may be statistically significant, the low-percentage sun1 of squares 

associated with the trends partially explains the 

similarities between the deviation maps (figs. 136.2AD) and the map of the original data (fig. 136.1). 

San1pling error appears to be one major factor displayed by the deviation maps, and it gives rise to sharp 

local fluctuations of both the original data and the 

deviations of values about the trends. Comparison of 

replicate analyses n1ade on the same sample indicates 

that analytical variation is cmnparatively sn1all. 

Sampling error does not in1ply mistakes in selection of 

samples or in the san1pling procedure, but refers only 

to the difference between the value obtained on a 

sample and the mean value that would have been 

obtained had all possible samples occurring at the 

sample site been taken. Such complete sampling, of 

course, is impossible and all san1ples contain error; the 

error is inversely proportional to the number of san1ples 

taken at the site and directly proportional to the 

natural local variation in the alluvium. 

The map in figure 136.3 shows the n1oving-average 

copper content of the alluvium across the area. In 

construction of this n1ap, each original copper value was 

replaced by an unweighted average of that value and 

the four values closest to it on the n1ap in figure 136.1. 

The effect of the moving average is to smooth out local 

variation-to reduce the effects of sampling error and 

other small-scale fluctuations in the data. A trend in 

the data across the area is now rnore apparent. 

Four trends cmnputed on the rnoving-average data, 

and deviations of the averages from the trends, are 

shown in figures 136.4A-D. Analysis of variance 

tests of the trends could not be made because of 

interdependence of data imposed by the n1oving-average 

rnethod. The proportions of the total sun1s of squares 

QUARTZITE 

1 '""""" 0 500 FEET 

accounted for by the linear through quartic trends, 

however, range from 35 to 78 percent. 

Deviations of moving-average values from trends 

fitted to the averages appear to clearly outline the 

major part of the copper ore body beneath the alluvial 

cover. Deviations from the quartic trend may be 

especially significant. Although "negative anomalies" 

are connnonly not regarded as ore indicators by geochernieal prospectors (Hawkes and Webb, 1962, p. 27), 

the presence of the negative deviations over the ore 

body in figures 136.3 and 136.4A-D necessitates consideration of their importance here. The possibility 

that the negatlve deviations over the ore body (figs. 

136.3 and 136.4) are n1erely a result of the adjacent 

high values that elevate the trend in this region may 

be excluded for two reasons: (1) the negative deviations correspond closely to the ore body, except over 

the southern part, and (2) they occur on only one side 

of the high, the side where the ore body is located. It 

is assun1ed, therefore, that the copper low over the ore 

body is real and originated from natural processes. 

The copper high southwest of the ore body, though 

pronounced (figs. 136.3 and 136.4), is caused in very 

large part by one extreme value (600 ppm) in this area. 

Recon1putation of the trends and trend deviations, excluding the extren1e value, results in severe depression 

of the high, although the low deviations over the ore 

persist. 

Low copper contents in alluvium over the ore body 

might have resulted frmn circulation of sulfate solutions and consequent leaching of copper in this area; 

cores taken from the ore body contain tactite, abundant 

sulfide rninerals, and secondary copper oxides. 

The positive deviations adjacent to the ore body on 

its southwest side (figs. 136.3 and 136.4A-D) may have 

resulted from precipitation of leached copper downdip 

EXPLANATION 

Copper content 

• • Mineralized 

More than 25 core hole 

parts per million 

D Sampled 

locality 

25 to -25 

o· parts per million 

§ 

Less than -25 

parts per million 

FIGuRE 136.3.-Moving-average copper content of alluvium in soils, Rocky Range, 

Utah (contoured on deviations from the mean). Contour interval 25 ppm; 

values larger than 100 ppm and smaller than -100 ppm not contoured. 
D82 GEOCHEMISTRY 

EXPLANATION 

Copper content 

More • than 25 

parts per million 

25 to -25 

parts per million 

-~ 

Less than -25 

parts per million 

A. LINEAR TREND AND DEVIATIONS FROM LINEAR TREND 

• 

Mineralized B. QUADRATIC TREND AND DEVIATIONS FROM QUADRATIC TREND core hole 

Sampled 

locality 

N 

0 

C. CUBIC TREND AND DEVIATIONS FROM CUBIC TREND 

FEET 

500 

D. QUARTIC TREND AND DEVIATIONS FROM QUARTIC TREND 

FIGURE 136.4.-Trends (dashed lines), in parts per million, and trend deviations of moving-average copper content in alluvium, 

Rocky Range, Utah. Contour interval 25 ppm; values larger than 100 ppm and smaller than -100 ppm not contoured. 

from its source, or from mechanical transportation of 

copper downhill during formation of the alluvial cover. 

This geologic interpretation of the trend-analysis 

results is only one of a nurnber that could be advanced, 

but whether it is correct or not has no bearing on the 

value, or the potential value of these results or results 

frmn future work. There can be little doubt that deviations fron1 progressively higher order trends, 1st 

through 4th degree, show an increasingly better spatial 

correspondence to the known ore body in the area, or 

that the nwving-average trend deviations in general 

show a clearer correspondence to the ore body than do 

the original data. 

Polynomial terrns of 5th, 6th, and 7th degree account 

for nonsignificant portions of the variance of the original data and, similarly, small portions of the total smn 

of squares in the n1oving averages (see table). Consequently, the quartic trend is regarded as the probable 

appropriate rnodel to describe the trend (Ostle, 1954, 

p. 141-142). The question of selecting a model to describe the trend in a particular set of data (that is, how 

to decide whether the trend should be described by a 

1st, 2d, or higher order equation in a particular problem) has not been completely resolved by previous 

workers, and a great deal of experimentation needs to 

be d.one. Trend analysis of geologie data is not yet 

developed to the stage where it ean be applied with 

preset objective rules. 

Statistical tests for trend significance, employing the 

F ratio, are not strictly valid if local concentrations of 

positive or negative deviations are present. Such concentrations imply the absence of independenee of the 

deviations, a fundamental assumption prerequisite to 

the test. Thus, the very property of the data being 

sought is a hindrance to an important part of the statistical analysis. The use of moving averages further reduces 

the independence of the deviations, to a point where 

F tests should not be presented as even approximately 

correct tests of significance. On the other hand, if the 

statistical significanee determined for trends in the 

original data is accepted, there may be little need to test 

the almost identical trends in the moving-average data. 

The con1putation of trends in the moving-average 

data rnay be cireumvented by applying the movingaverage method to the deviations frmn trends in the 

original data. Contour n1aps constructed in this 

rnanner are given in figures 136.5A-D. In this partie-
CONNOR AND MIESCH D83 

EXPLANATION 

Copper content 

More • than 25 

parts per million 

D 

25 to -25 

A. MOVING AVERAGES OF DEVIATIONS FROM LINEAR TREND 

SHOWN IN FIGURE 136. 2 A 

parts per million 

§ 

Less than -25 

parts per million 

• 

Mineralized 

core hole 

B. MOVING AVERAGES OF DEVIATIONS FROM QUADRATIC TREND 

SHOWN IN FIGURE 136. 2 B 

Sampled 

locality 

C. MOVING AVERAGES OF DEVIATIONS FROM CUBIC TREND 

SHOWN IN FIGURE 136. 2( 

0 

N 

l FEET 

500 0~. 

o. . . 0 

ALLUVIUM () 

D. MOVING AVERAGES OF DEVIATIONS FROM QUARTIC TREND 

SHOWN IN FIGURE 136.20 

FIGURE 136.5.-Moving averages of trend deviations shown in figure 136.2. Contour interval 25 ppm. Values larger than 

100 ppm and smaller than -100 ppm not contoured. 

ular study such rna ps do not exhibit as clear a reltioan 

of alluvial copper to the ore body as observed in the 

moving-average deviations (figs. l36.3A-D), but the 

patterns are similar. Which method, if either, will 

prove to be the better one on further application is 

unknown. 

One additional and highly pertinent matter deserves 

attention here; this is the problem of anomaly definition. 

In the trend-analysis method, a geochen1ical anomaly 

(a local feature of the data deserving of investigation) 

should be defined in tern1s of its magnitude, both in 

lateral extent and in intensity, but such definition 1nust 

await additional experience with trend analysis in 

geochemical prospecting problems. 

REFERENCES 

Erickson, R. L., and Marranzino, A. P., 1960, Geochemical 

prospecting for copper in the Rocky Range, Beaver County, 

Utah: Art. 47 in U.S. Geol. Survey Prof. Paper 400-B, 

p. B98-B101. 

Grant, Fraser, 1957, A problem in the analysis of geophysical 

data: Geophysics, v. 22, p. 309-344. 

Hawkes, H. E., and Webb, J. S., 1962, Geochemistry in mineral 

exploration: New York, Harper and Row, 413 p. 

Krumbein, W. C., 1956, Regional and local components in facies 

maps: Am. Assoc. Petroleum Geologists Bull., v. 40, no. 9, 

p. 2163-2194. 

--- 1959, Trend surface analysis of contour-type maps with 

irregular control-point spacing: Jour. Geophys. Research, 

v. 64, no. 7, p. 823-834. 

Oldham, C. H. G., and Sutherland, D. B., 1955, Orthogonal 

polynomials: their use in estimating the regional effect: 

Geophysics. v. 20, p. 295-306. 

Ostle, Bernard, 1954, Statistics in research: Ames, Iowa, The 

Iowa State College Press, 487 p. 

Whitten, E. H. T., 1959, Composition trends in a granite: modal 

variation and ghost stratigraphy in part of the Donegal granite, Eire: Jour. Geophys. Research, v. 64, no. 7, p. 835-848. 
Article 137 

INVESTIGATION OF SAMPLING-ERROR EFFECTS 

IN GEOCHEMICAL PROSPECTING 

By A. T. MIESCH and J. J. CONNOR, Denver, Colo. 

Abstract.-Large local variation in soils and rocks causes large 

sampling error, and may obscure variation that is of interest in 

geochemical prospecting. A simulation experiment illustrates 

how the effects of sampling error may be overcome by dividing 

the area into cells and randomly selecting a number of samples 

per cell. 

Analysis of geochemical data from the Rocky Range, 

Utah, by Connor and Miesch (Art. 136) points to the 

probable importance of sampling error in obscuring 

subtle relations between minor elmnents in alluvium and 

buried ore deposits. Sampling error does not in1ply 

incorrect sampling procedures or mistakes in carrying 

out the procedures, but merely the difference between a 

sample and the total material that might have been 

sampled at the same locality. Locality here can n1ean a 

point on a sampling grid, a cell within a grid, an outcrop, 

or an entire rock body, depending on what the sa1nple 

is intended to represent. In the following discussion, 

we shall assume that there is no sampling bias, that the 

average of a number of values representing a san1pling 

locality tends toward the true average value for that 

locality, as the number of sample values is increased. 

In this sense, we are concerned here with sampling 

precision, one specific aspect of sampling error. Sampling precision obtained in any specific sampling program is determined entirely by local variation or local 

heterogeneity in the material being sampled. 

In the design of a geochemical prospecting san1pling 

plan, the selection of the sampling interval is of particular importance. For the plan to be efficient, the 

interval n1ust depend on the dimensions of the target 

being sought. An unnecessarily coarse sampling interval may prevent detection of the target and too fine 

an interval will result in sample and analytical waste. 

Actually, too little can be predicted about target sizes 

(that is, dimensions of dispersion halos) resulting from 

various sizes and types of ore deposits in different 

geologic environments to select the interval rigidly on 

this basis. The interval is commonly selected by consideration of target size gained through experience in 

specific areas or types of geologic environments. 

Once the sam piing interval has been selected, on 

whatever basis, the area may be divided into a number 

of square cells, each cell having the dimensions of the 

sampling interval. The purpose of the sampling, then, 

is to exa1nine variation among cells. Variation within 

cells is not of particular interest, except to evaluate the 

effects of sampling error. Due to natural local heterogeneity in many rocks and soils, the variation within 

cells may be significantly larger than that anwng cells. 

If this happens to be the case, any variation among 

cells will probably be obscure if one collects one or a 

number of samples per cell and plots the individual 

sample values on n1aps. Plotting average values for 

each cell will help clarify the pattern of variation among 

cells because the variation of an average is less than that 

of the individual values. The number of values on 

which each average should be computed in order to 

reduce the effects of within-cell variation sufficiently 

can be estimated fron1 preliminary results, as shown in 

the following discussion. 

A simulation experiment has been conducted to 

illustrate the approach. A linear trend identical to 

that shown in figure 136.2A of Connor and Miesch 

(Art. 136), having the forn1 Cu=90.4+0.88 .. X--0.31 Y, 

is assun1ed to represent a trace-copper trend (fig. 

137.1A). Copper is measured in any arbitrary unit 

(for example, parts per million) and "'y and Y are units 

of distance from an arbitrarily selected origin. The 

map area measures 80 by 120 units and has been 

divided into cells 20 units on a side; values of the trend 

were calculated for 2 randon1ly selected positions in each 

cell. To each of these trend values was added a randmn 

ART. 137 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D84-D88. 1964. 

D84 
MIESCH AND CONNOR D85 

X -----.10 30 50 70 90 110 

y.--,,--,---,--.. --.---.--n,--,--~~~--~---

~ 10 

30 + 

70 

y 

~ 10 

30 

50 

70 

13 

A. ORIGINAL TREND (Cu =90.4+0.88X -0.31Y) 

X-----. 10 30 50 70 90 llO 

3 \ \' \ 

-\- 10 

+2 +~ \ +ll 5 + 8 + 

~ \ 6 \7 9 \12 

\ 14 '6 

17 T 24 ~ + + + +\ + 23 

j 15 \ 18 \ 19.1?0 ~1 2< \ 

}5 26 32 3 30 ""' 01 

\+ + +9 +~ 34 

\ 28 i-

!>;) 31 \ 

+ ~ 1---0 27 ~ \ 36 \35 

0 38 40 \ 43 45 \ t "I + 42 + +44 

\ 

+ \ +4A 

\ 39 41 I \48 46 

C. COMPUTED TREND DETERMINED FROM SAMPLE 

VALUES IN FIGURE 137.1 B (Cu =102.8+0.71X-0.16Y) 

y 

~ 

X_____. 10 30 50 70 90 110 

B. SAMPLE VALUES (2 VALUES PER CELL) 

X-+10 30 50 70 90 110 

D. DEVIATIONS OF SAMPLE VALUES FROM COMPUTED 

TREND IN FIGURE 137.1C 

FIGURE 137.1.-Contour maps of original trend, sample values, computed trend, and trend deviations (contour interval equivalent 

to 25 parts per million). 

deviation drawn from a normal population with J.t=O 

and u2=7,487, providing 48 "sample values." 

A sample value, V, is determined by: 

V -90.4+0.88X-0.31 Y +ud, 

where u= .J7487 =86. 52, and d is a normal random 

deviate with J.t=O and a-;,;= 1 taken from tables of The 

Rand Corp. (1955). The symbol JL refers to the 

population n1ean, the n1ean of an infinite number of 

deviates that could have been used. The sJinbol u2 

refers to the population variance, and u is the population standard deviation. 

The variance of the random deviations, 7,487, is 

identical to the mean sun1 of squares cmnputed for the 

linear-trend deviations in the table of Connor and 

1fiesch (Art. 136). The 48 san1ple values, each consisting of a trend value and a random-error deviation, 

are contoured in figure 137.1B. The random error has 

obliterated the trend of figure 137.1A. Table 137.1 

TABLE 137.1.-Estimation of variance components 

Degrees Mean Estimate 

Sum of of Mean square is of 

Source of variation squares free- square estimate variance 

dom of- component 

A. 48 trend values (fig. 

137.1A): Between cells ____________ 44,109 23 1, 918 u2+2uc2 933 

Within cells _____________ 1,260 24 53 q2 53 TotaL _________________ 45,369 47 

B. 48 sample values (fig. 

137.1B). Between cells ____________ 195,224 23 8,488 u2+2u,2 892 Within cells ______________ 160,917 24 6, 705 u2 6, 705 TotaL _________________ 356,141 47 

c. 192 sample values (fig. 

137.20). Between cells ____________ 321,199 23 13,965 u2+8u2 638 Within cells ______________ 1,489,298 168 8,865 q2 8,865 

TotaL _________________ 1,810, 497 191 

D. 384 sample values (fig. 

137.2E). Between cells ____________ 372,560 23 16,198 u2+16u2 509 Within cells _____________ 2,894,465 360 8,040 q2 8,040 

TotaL _________________ 3,267,025 383 

(parts A and B) shows estimates of the within- and 

between-cell variance components of values contoured 
D86 GEOCHEMISTRY 

in figures 137.1A and 137.1B. 1 The variation of trend 

values from figure 137.1A is predominantly between 

cells, whereas the variation of san1ple values contoured 

in figure 137.1B is predominantly within cells. 

A least-squares regression surface, fitted to the values 

of figure 137.1B using a technique described by 

Krumbein (1959, p. 826), is shown in figure 137.1C. It 

approximates the original trend in figure 137. L4, is 

statistically significant at the SO-percent confidence level 

(table 137.2, part A), but accounts for only 8 percent 

TABLE 137.2-Analysis of variance of regress1:on surfaces 

I Percent 1

Degrees Source of variation Sum of of total of free- Mean 

squares sum of dom square 

squares 

F 

A. 48 samples: 

Regression surface 

(fig. 137.1C)______ 28,900 

Residuals (fig. 

137.1D)- --------- 327,300 TotaL ________ 356,200 

B. Means of 2 samples 

per cell (fig. 

137.2B): 

Regression sur- face ______________ 20,590 

Residuals __________ 8.~.310 

TotaL _________ 105,900 

C. Means of 8 samples 

per cell (fig. 

137.2D): 

Regress ion sur- face______________ 10,810 

Residuals _________ 29,200 

TotaL ________ 40,010 

D. Means of 16 samples 

per cell (fig. 

137.2F): 

Regress ion sur- face______________ 12,520 

Residuals__________ 10,750 

TotaL. ______ 23,270 

92 

19 

81 

27 

73 

54 

46 

2 14• 450 }1.99 [F2,4s(o.9s) =3.21; 

45 7, 273 Fz.4s(o.so) =1.67] 

2 10,295 }2.53 [Fz.zt (o.9s) =3.47; 21 4, 062 Fz.zt (o.9o) =2.57] 

2 

21 

2 

21 

5. 405 } 1, 390 3.89 [F2.21 (o.9s) =3.47] 

6, 260 } 512 12.23 [Fz.2l(0.999) =9.77] 

of the total sum of squares. The rmnaining portion of 

the total sum of squares is contained in the residuals, 

or the deviations of values from the trend. Contours 

of the residuals (fig. 137.1D) are very similar to those 

drawn on the original data (fig. 137 .1B), before the 

trend was rmnoved. 

The only stable part of the sin1ulated copper distribution is the trend; the deviations are entirely random 

with respect to position on the map. If the simulation 

experiment were repeated, it may be expected that 

something approximating the imposed trend would 

again be recovered, but the second deviation 1nap is 

likely to be entirely different frorn that in figure 137. 

1D. The patterns of variation a1nong cells as shown 

by the original values (fig. 137.1B) and by the trend 

deviations (fig. 137.1D) are unstable, due in large part 

to variation within cells, or to eell-sn,Jnpling error. Inasnmch as the analysis of variance shows the importance 

of san1pling error in this problmn, average values for 

each cell are computed to reduce the sampling-error 

1 The method of estimation of variance components is described in numerous 

statistical tests, such as Tippett (1952, p. 172). Krumbein and Slack (1956) also 

present a discussion of the method applied to a geochemical problem. 

effects. The variance of an average is 1/Nth of the 

variance of the N values: (J'i=fi2jN. 

Figure 137 .2A shows the distribution as determined 

from 24 cell means, each mean computed on the 2 

values in the cell. The extreme variation of figure 

137 .1B is subdued, but the original trend is still not 

apparent. A regression surface fitted to the data of 

figure 137.2A and deviations from the surface are shown 

in figure 137 .2B. The surface is nearly significant at 

the 90-percent confidence level, and accounts for 19 

percent of the total sum of squares in the average data. 

The deviations from the trend are still pronounced. 

The effects of within-cell variance can be further 

reduced by "collecting" a number of additional "samples" per cell sufficient to reduce the variance of their 

Inean to an amount more similar to the between-cell 

variance. This number can be approxi1nated from 

variance-component estimates, using a method applied 

to soil sampling by Youden and Mehlich (1937, p. 68). 

Their method applied to these data show that the 

collection of n samples per cell should provide a mean 

for each cell that tends to have less variance than means 

among cells: fi2

jn5: fi~, where fJ'2 is the variance within 

cells and (J'~ is the variance between cells. Table 137.1 

(part B) gives variance components for the 48 initial 

san1ples of figure 137.1B. Accordingly, by the above 

inequality, 6,705/n5:892; n~8. 

Instead of 2 samples per cell, 8 are needed to provide 

a cell-mean variance roughly equal to the estimate of 

between-cell variance. 

Accordingly, 6 additional samples were collected 

frmn each cell, using the same procedures used in 

obtaining the first 48. Figure 137.20 shows the 

distribution of copper based on means of eight values 

per cell. The strong highs and lows of figure 13 7 .2A 

are reduced, but the imposed trend is still not particularly apparent. A regression surface fitted to the 

data of figure 137.20 and deviations from the surface 

are shown in figure 137.2D. Analysis of variance 

(table 137.2, part C) indicates that the trend is statistically significant at the 95-percent confidence level 

and accounts for 27 percent of the total sum of squares 

in the average data. The trend deviations are becoming less in1pressive. 

Variance components within and between cells are 

esti1nated in table 137.1 (part C) for the 192 sample 

values used in figure 137.20. It is presumed that the 

new esti1nate of within-cell variance, based on 4 times 

as many samples per cell, is more stable than that 

previously estimated from the 48 samples (table 

137.1, part B). Applying the technique of Youden 

and Mehlich again to the revised component estimates, 

a new estimate of samples needed per cell to reduce 

within-cell effects to an amount equal to or less than 
MIESCH 

X-+10 30 50 70 90 110 

y 

~ 10 

70 

y 

~ 10 

50 

70 

y 

t 

10 

30 

70 

+ 

A. CELL MEANS, EACH COMPUTED FROM 2 SAMPLE 

VALUES , USING THE 48 SAMPLE VALUES FROM 

FIGURE 137. 28 

X-+10 30 50 70 90 110 

C. CELL MEANS, EACH COMPUTED FROM 8 SAMPLE 

VALUES . MAP BASED ON 192 SAMPLE VALUES 

X-+10 30 50 70 90 llO 

+ + + + 

+ + 

+ + 

E. CELL MEANS, EACH COMPUTED FROM 16 SAMPLE 

VALUES . MAP BASED ON 384 SAMPLE VALUES 

AND CONNOR D87 

X-+10 30 50 70 90 llO 

y 

t 

10 

B. COMPUTED TREND (DASHED LINES) AND TREND DEVIATIONS USING CELL MEANS FROM FIGURE 137.2A 

TREND EQUATION: Cu =112.4+0.82X-0.38Y 

X-+10 

y.-~------.--.----,.-.---'"~--~,-~--"-r' 

30 50 70 90 110 

t 

10 

50 

70 

D. COMPUTED TREND (DASHED LINES) AND TREND DEVIATIONS USING CELL MEANS FROM FIGURE 137. 2C 

TREND EQUATION: Cu =103.1+0.61X-0.15Y 

X-+10 

v~~--~--.-----.,,---r--,--~r-~-----,--, 

30 50 70 90 llO 

t 

10 

30 

50 

F. COMPUTED TREND (DASHED LINES) AND TREND DEVIATIONS USING CELL MEANS FROM FIGURE 137. 2f 

TREND EQUATION: Cu = 93.6+0.66X-0.13Y 

FIGURE 137.2.-Contour maps of cell mean sample values, computed trends, and trend deviations (contour interval equivalent 

to 25 parts per million). 
D88 GEOCHEMISTRY 

those among cells is obtained: 8,865/n~ 638; n ~ 14. 

In an attempt to insure that within-cell effects are 

reduced below those between cells, 8 additional samples 

(rather than the indicated 6) were taken from each 

cell of figure 137.1A using the same procedures used 

in obtaining the previous 192. A total of 384 samples 

have now been collected. 

Figure 137.2E is a contour map of the 24 cell means 

based on 16 samples per cell. The regression surface 

fitted to the 24 cell n1eans and the deviations from the 

surface are shown in figure 137.2F. The analysis of 

variance test of the trend is given in table 137.2 (part 

D). This trend is highly significant and accounts for 

54 percent of the total sum of squares in the average 

data. A comparison of figure 137.2F with figure 

137.1D indicates the large reduction of local or withincell effects when cell means are computed from a larger 

number of samples. 

A new estimate of the nmnber of samples per cell 

needed to reduce within-cell effects to an a1nount less 

than those between cells n1ay be obtained from the 

components of table 137.1 (part D): 8,040;n~509; 

n ~ 16. This estimate is equal to the actual nu1nber of 

samples used in the analysis and is twice that of the 

initial estimate (8 samples) computed from the original 

48 values. The initial estimate was based on too few 

samples to be stable, but did serve as a rough estimate 

or guide to the number of samples required from each 

cell. Increasing the number of samples per cell beyond 

16 would clarify the trend and suppress the effects of 

within-cell variance on trend deviations even farther. 

In order to use the variance-component technique 

provided by Y ouden and Mehlich, it is not necessary to 

sample every cell in the preliminary survey. Cells to 

be examined in a preliminary survey might be picked 

randomly. Reliability of the results will in all cases 

depend on randomization procedures, the validity of 

other assumptions prerequisite to analysis of variance 

(Eisenhart, 1947), the number of cells sampled, and the 

number of samples taken per cell. 

Geochemical prospecting by soil analysis is well 

suited to the use of statistical designs. The restriction 

on sampling design imposed by lack of outcrops in most 

geologic sampling is, for the most part, not present. 

Generally, samples are taken over an area at more or 

less equal spacing, frequently on a square grid. Merits 

of grid samples, unalined stratified samples, and random 

samples and stratified random samples, are discussed by 

Quenouille (1945), Krumbein (1954), and Berry (1962), 

but the variance-component approach used here requires random sampling within each cell (stratified 

random samples). 

In the geochemical prospecting study in the Rocky 

Range (Connor and Miesch, Art. 136),· the problem of 

sampling error was tentatively resolved by using a 

moving-average method to smooth out the data, but 

even though this procedure clarified the possible geologic 

relations shown by the data, it did introduce other 

problems. Variation among adjacent cells is suppressed, and independence of deviations from computed 

trends, important from statistical considerations, is 

partially destroyed. It is suggested that the estimation 

of variance components to determine within- and 

between-cell effects, and estimation of the number of 

samples required to sufficiently reduce the within-cell 

effects, is a more satisfactory method for reducing effects 

of local variation or sampling error in geochemical 

prospecting. 

REFERENCES 

Berry, B. J. L., 1962, Sampling, coding, and storing flood plain 

data: U.S. Dept. Agriculture, Agriculture Handb. 237, 27 p. 

Eisenhart, Churchill, 1947, the assumptions underlying the 

analysis of variance: Biometrics, v·. 3, no. 1, p. 1-21. 

Krumbeiu, W. C., 1954, Statistical significance of beach sampling 

methods: Beach Erosion Board, Tech. Memo. 50, 33 p. 

--1959, Trend surface analysis of contour-type maps with 

irregular control-point spacing: Jour. Geophys. Research, 

v. 64, no. 7, p. 823-834. 

Krumbein, W. C., and Slack, H. A., 1956, Statistical analysis of 

low-level radioactivity of Pennsylvanian black fissle shale in 

Illinois: Geol. Soc. America Bull., v. 67, no. 6, p. 739-761. 

Quenouille, M. H., 1945, Problems in plane sampling: Math. 

Statistics Annals, v. 20, p. 355-375. 

The Rand Corporation, 1955, A million random digits, with 

100,000 normal deviates: Glencoe, Ill., The Free Press, 

600 p. 

Tippett, L. H. C., 1952, The methods of statistics, 4th ed.: New 

York, John Wiley and Sons, Inc., 395 p. 

Youden, W. S., and Mehlich, A., 1937, Selec~.~ion of efficient 

methods for soil sampling: Boyce Thompson Inst. Contr., 

v. 9, p. 59-70. 
Article 138 

EFFECT OF CATION EXCHANGE ON THE THERMAL BEHAVIOR 

OF HEULANDITE AND CLINOPTILOLITE 

By ANNA 0. SHEPARD and HARRY C. STARKEY, Denver, Colo. 

JiVork done in cooperation with the U.S. Atomic Energy Commission 

Abstract.-Heulandite has the thermal stability of clinoptilolite 

when the calcium is largely replaced by potassium. Clinoptilolite has the thermal behavior of a heulandite-like mineral, 

associated with some natural clinoptilolites, when calcium 

replaces most of the alkalis. X-ray analysis was used in the 

experiments. 

Heulandite and clinoptilolite, zeolites with nearly 

identical X-ray patterns, differ in thermal behavior. 

The crystal structure of heulandite is changed on heating; that is, the mineral inverts. The higher temperature form has been referred to as heulandite B (Slawson, 

1925; Milligan and Weiser, 1937; Koizumi and 

Kiriyama, 1953; and Mumpton, 1960). The temperature of inversion varies with the length of time that it is 

heated. Clinoptilolite does not invert on heating, 

and it withstands higher temperatures and longer 

heating than heulandite (Mumpton, 1960; Shepard, 

1961). In chemical composition, these minerals differ 

in two respects: (1) the calcium content is higher than 

that of alkalis in heulandite, whereas alkalis- exceed 

calcium in clinoptilolite, and (2) clinop tilolite has the 

higher silica-alumina ratio. Mumpton (1960, p. 363) 

considered that the essential difference between the 

two minerals is in the silica-alumina ratio: he reasoned 

that a mineral should not be defined by its exchangeable 

cation. Mason and Sand (1960, p. 348-349) emphasized the difference in cations and illustrated graphically that the two minerals differ more in content of 

CaO · Alz03 and (N a, K) 2 0 · Al20 3 than in silica content. 

l\1umpton, Mason, and Sand, contrary to Hey and 

Bannister (1934), all considered heulandite and clinoptilolite distinct minerals because of the apparent absence 

of minerals of intermediat,e composition that would 

characterize an isomorphous series. 

Investigation of the effect of chemical composition 

on the thermal behavior of these two zeolites has been 

difficult because clinoptilolite, unlike heulandite, is 

not easily obtained in a pure state. A possible means 

of studying the effects of alkalis and alkaline earths is 

by the exchange of cations in the minerals. Results 

of preliminary tests that were limited largely to a single 

set of conditions are reported at this stage of the study 

because the properties of some of the products are 

similar to those of certain natural minerals that occur 

as intergrowths with clinoptilolite. 

The samples used in these cation-exchange experiments included heulandite from Summit and Paterson, 

N.J., and Berufiord, Iceland, and clinoptilolite from 

the Pierre Shale, Buffalo County, S. Dak. The 

heulandites were well crystallized. Clinoptilolite from 

the Pierre Shale had an exceptionally strong X-ray 

pattern that showed no impurities, but minute inclusions could be detected optically. Nor mal solutions of 

calcium, potassium, and sodium chlorides, neutralized 

with their respective hydroxides, were used to provide 

the exchangeable cations. Samples were of two grain 

sizes, less than 100 mesh and less than 2 microns. 

The process of exchange was accelerated by heating 

samples in a pressure cooker for 16 hours (Starkey, 

Art. 139), a method that might be classed as 1nildly 

hydrothermal. The thermal behavior of the minerals 

before and after exchange was determined by X-ray 

analysis of sa.mples heated for 10 minutes at 50° C 

temperature intervals (Shepard, 1961). Samples were 

X-rayed as soon as cool enough to handle and scanned 

rapidly (2° /min) because heulandite B begins to change 

back to the low-temperature form 15 minutes after 

cooling. 

With the heating schedule adopted, the natural 

heulandite samples ~tarted to invert at 250°0, the 

pattern of heulandite B attained maximum intensity 

between 300°0 and 350°0, and its structure was nearly 

ART. 138 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D89-D92. 1964. 

D89 
D90 GEOCHEMISTRY 

Non heated 

typical heulandite (fig. I38.7, A, B). A si.milar 

behavior has been observed in some heulandite-like 

minerals from the Nevada Test Site. 

Clinoptilolite from the Pierre Shale (fig. I38.2, 0) 

treated with a IN CaCl2 solution is rendered less stable; 

it inverts and the positions of nine strong peaks are 

similar to those of heulandite B (fig. I38.2, D). This 

modified clinoptilolite is not identical with heulandite, 

A however; the temperatures of inversion and of destruction are both approximately I00°C higher than those of 

heulandite. 

The stabilizing effect of potassium on heulandite and 

the loss of stability of clinoptilolite when alkalis are 

replaced by calcium indicate that potassium is an 

important factor in determining the thermal stability of 

""" these two zeolites. 

Treatment with INN aCl did not affect the thermal A A 1\;V\. A /\.,...., • • • h A A soooc c ;J~ w · -~... ~ v~' behavior of either clinoptilolite or heulandite. The 

~~ . 1 sodium content is usually higher than potassium in 

natural clinoptilolite, and the amount of exchange of 

D 

~~ f 400,C A 

10\ ~JJ\ ry ~vrl J"" 

)

\ l F'~ 5WC )V~ FIGURE 138.1.-X-ray diffractograms illustrating thermal be- _}\. \ lif

1 ~~ j Heulandite 

3.0 4.0 5.0 

d-SPACING, IN ANGSTROM UNITS 

havior of heulandite. A-C, untreated mineral; D, mineral " Heulandite 

treated with 1 N K61. 

destroyed at 500°C (fig. I38.I, A-0). When these 

samples were treated with IN KCl and heated, some did 

not invert at all and others contained only a minor 

constituent that inverted, forming a weak 020 heulandite-B peak. Like clinoptilolite, the heulandite 

that did not invert could be heated above 800°C before 

its structure was destroyed (fig. I38.I, D). 

The effects of the length of time the sample was 

heated, grain size, and concentration of the solution 

Non heated 

used for cation exchange were tested in samples that . 1 ~Jfiu~4soXoj \~~ showed a small amount of heulandi te B after exchange .r 

with potassium chloride. Increase of the heating period 

landite-B 

from I6 to 

020 

48 

peak, 

hours 

but 

did 

when 

not 

grain 

eliminate 

size was 

the 

reduced 

weak heuto ~ 

less than 2 microns, a dimension still well above the 

limits of X-ray resolution, no trace of the peak remained. 

Increase of the concentration of the potassium chloride 

solution from IN to 2N affected the inversion of the 

020 heulandite-B peak without decreasing its intensity; 

contraction of the peak was more gradual than it is in 

Clinoptilolite 

~ ----~--~~~--~~It- 4.0 5.0 

~--___l_, ____ _ 

3.0 

d-SPACING, IN ANGSTROM UNITS 

FIGuRE 138.2.-X-ray diffractograms illustrating thermal 

behavior of heulandite and clinoptilolite. A, B, heulandite 

treated with 2N KCl; C, D, clinoptilolite treated with lN 

CaCh. 
SHEPARD AND STARKEY D91 

potassium is as yet undetermined. Lack of change in 

the thermal behavior of heulandite treated with 1N 

N aCl emphasizes the importance of determining the 

extent of exchange. If the cations of the heulandite 

after treatment with sodium chloride are comparable to 

those of natural clinoptilolite and the heulandite retains 

its original thermal behavior, the possibility that the 

silica-alumina structure also affects thermal behavior 

has to be considered. 

The composition of the minerals after the cation 

exchange has not yet been determined by wet chemical 

analysis. Estimations of the extent of alteration 

induced by these exchange procedures are based on 

results of analyses of leachates. The cations of the 

natural and the treated n1inerals were released by IN 

neutral ammonium chloride by exchange methods. 

Comparison of results is therefore limited to exchangeable cations. In the' analysis of leachates, alkalis were 

determined with a flame photmneter and calcium by 

versene titration. 

TABLE 138.1.-Comparison of cations released by NH4+1 front 

natural and from previously heated minerals 

[Cations in milliequivalents per 100 g of sample] 

Heulandite from Summit, N.J. Clinoptilolite from Pierre Shale 

Mineral treated Mineral treated 

Natural with- Natural withCation minerall---,----l mineral I----.---

KCl NaCl CaCb NaCl 

------1----1----------------

Ca __________________ 169.5 91.1 124.1 43.9 167.0 9.6 Na _________________ 14.5 106.0 69.4 122.2 

K_----------------- 20.0 162.3 ---------- 59.6 13.9 20.2 

The analyses show high percentages of critical cations 

in the treated n1inerals. Expressed in meq/100 g of 

sample, potassiun1 made up 63 percent of the exchanged 

cations in the leachate of the KCl-treated heulandite 

that did not invert, and calcium made up 93 percent 

of the exchanged cations in the leachate of the CaCl2-

treated clinoptilolite that inverted. The calciumpotassium ratios of the determined cations (meq/100 g 

of sample) in the leachates from the natural and 

comparable treated minerals are in si1nilar ranges: 

natural heulandite, 8.48, calcium-treated clinoptilolite, 

12.01; natural clinoptilolite, 0.74; KCl-treated heulandite, 0.56. 

Analyses of the ammonium chloride leachate of the 

sodium-treated heulandite indicate a complete replacement of the potassiun1 with sodium and depletion of 

the calcium; nevertheless, the amount (in milliequivalents) of calcium is still greater than the amount of 

sodium, a fact that may account for the typical 

heulandite-like thermal behavior of the mineral. 

716--626 0-64-7 

Sodium did not fully replace the potassium in the 

clinoptilolite, but it constitutes 80 percent of the sum 

of the three cations, expressed in n1illiequivalents, and 

calcium is reduced to 6 percent. 

The extent of exchange with ammonium chloride in 

these tests is indicated by comparison of the calcium, 

potassium, and sodium cations determined in leachates 

of heulandite and clinoptilolite with the determination 

of these ions by wet chemical analysis of these minerals. 

(table 138.2). 

TABLE 138.2.-Percentage of original cat1:ons in leachate from cation 

exchange 

[Cations in meq/100 g of sample] 

Heulandite from Summit, N.J. Clinoptilolite from Pierre Shale 

Cation Mineral! Leachate Percent Mineral Leachate Percent exchanged exchanged 

--------------- Ca __________________ 244.0 169.5 69.5 51.8 43.8 84.7 

Na __ --------------- 21.0 14.5 69.0 78.3 69.4 88.6 

K.----------------- 29.3 20.8 71.0 56.1 56.9 101.4 

1 Cations in original mineral determined by wet chemical analysis and converted to meq/100 g of sample. 

Approximately 70 percent of the cations expressed 

in meq/100 g in samples of heulandite and an average 

of 90 percent of those in samples of clinoptilolite were 

exchanged. 

The refractive indices of the minerals also show the 

effects of exchange, although they are less definitive 

than the thermal effeets. The untreated Paterson 

heulandite with indices in white light of a, 1.494, 

{3, 1.495+, and -y, 1.500-1.501 appeared as a fine 

aggregate with an average index of 1.482 after treatment with potassiu1n chloride. The average index of 

the untreated Pierre clinoptilolite, also an aggregate, 

was 1.470. Treatment with calcium chloride raised it 

to 1.480, not quite as high as that of the KCl-treated 

heulandite. 

Natural zeolites that behave thermally as though 

both clinoptilolite and heulandite or a "heulandite-like" 

mineral are present occur in tuffs of the Nevada Test 

Site (Shepard, 1961) and in other areas where clinoptilolite is the principal zeolite. Some of these zeolites are 

zoned, but most crystals are too fine to determine their 

optical homogeniety. The "heulandite-like" component of these samples does not invert at as low a temperature as typical heulandite. Its thermal behavior is 

similar to that of calcium-exchanged clinoptilolite. 

Natural zeolites with the thermal behavior of both 

clinoptilolite and a heu1andite-like mineral may have 

been formed by continuous crystallization under a 

changing environment to produce zoning comparable to 

that of plagioclase or they may have been formed by 

partial natural exchange of cations of clinoptilolite 
D92 GEOCHEMISTRY 

during some period after crystallization. The preliminary tests of the effects of cation exchange on the thermal behavior of heulandite and clinoptilolite suggests 

that partial natural exchange may have been the cause 

of the anomalous behavior of the heulandite-like mineral. 

Anomalous effects that have been reproduced in the 

laboratory include the higher ten1peratures as compared 

with those of heulandite at which the mineral inverts 

and is destroyed, the modification of the contraction 

of the 020 reflection during inversion, and the change in 

refractive indices. 

Cation size and charge must both affect the results 

obtained in the attempt to exchange cations of 

heulandite and clinoptilolite. It has semned doubtful 

that a univalent cation larger than calcium could 

replace it and balance the negative charge of heulandite, 

but the thermal behavior of the KCl-treated heulandite 

clearly indicates that an effective an1ount of potassium 

was introduced. The replacement of potassiun1 and 

sodiun1 by bivalent calcium in the clinoptilolite structure should not be difficult, yet a heulandite-like 

mineral rather than typical heulandite was produced 

in the attempted exchange. The extent of exchange 

and the effect of the silica-alumina ratio of the two 

minerals are both factors to be considered in future 

experiments. 

REFERENCES 

Ames, L. L., Jr., Sand, L. B., and Goldich, S. S., 1958, A contribution on the Hector, California, bentonite deposit: Econ. 

Geology, v. 53, p. 22-37. 

Bramlette, M. N., and Posnjak, E., 1933, Zeolitic alteration of 

pyroclastics: Am. Mineralogist, v. 18, p. 167-171. 

Hay,· R. L., 1963, Stratigraphy and zeolitic diagenesis of the 

John Day Formation of Oregon: Univ. Calif. Publ. in 

Geology, v. 42, p. 199-262. 

Hey, M. H., and Bannister, F. A., 1934, Studies on the zeolites, 

Part VIII, "Clinoptilolite," a silica-rich variety of heulandite; Mineralogical Mag., v. 23, p. 556-559. 

Koizumi, M., and Kiriyama, R., 1953, Structural changes of 

some zeolites due to their thermal dehydrations: U niv. 

Osaka Sci. Rept. no. 2, p. 67-85. 

Mason, B., and Sand, L. B., 1960, Clinoptilolite from Patagonia; 

the relationship between clinoptilolite and heulandite: 

Am. Mineralogist, v. 45, p. 341-351. 

Milligan, W. D, and Weiser, H. B., 1937, The mechanism of the 

dehydration of heulandite: Jour. Phys. Chemistry, v., 41, 

p. 1029-1041. 

Mumpton, F. A., 1960, Clinoptilolite redefined: Am. Mineralogist, v. 45, p. 351-370. 

Piersson, L. V., 1890, On mordenite: Am. Jour. Sci., v. 40, p. 

232-237. 

Shepard, A. 0., 1961, A heulandite-like mineral associated with 

clinoptilolite in tuffs of Oak Spring Formation, Nevada 

Test Site, Nye County, Nevada: Art. 264 in U.S. Geol. 

Survey Prof. Paper 424-C, p. C32D-C323. 

Slawson, C. B.l 1925, The thermo-optic properties of heulandite: 

Am. Mineralogist, 10, p. 305-331. 
Article 139 

DETERMINATION OF THE ION-EXCHANGE CAPACITY 

OF A ZEOUTIC TUFF 

By HARRY C. STARKEY, Denver, Colo. 

Abstract.-Determination of the exchange capacity of some 

zeolitic tuffs may require an extremely long time for the reaction 

rate to attain a constant value. A heating method is suggested 

whereby the rate of the reaction is increased, so that the exchange-capacity determinations can be made within a period of 

time as short as 24 hours. 

Studies of the ion-exchange capacities of volcanic 

tuffs collected at the Nevada Test Site showed that the 

longer the samples were leached, the higher were the 

observed capacities. A method was sought which 

would enable a constant value to be attained within a 

reasonably short time. 

The sample used for most of the experimental work, 

sample B, had the following mineralogical composition, 

based on X-ray diffraction analysis using nickel-filtered 

copper radiation: Approximately two-thirds consisted 

of quartz and feldspar with a trace of montmorillonite; 

one-third was made up of a zeolite which appeared to 

be a heulandite-clinoptilolite type. The latter had a 

strong (004) peak at 22.3 °28 which, according to 

Mumpton (1960), indicates clinoptilolite. 

Mumpton described clinoptilolite, however, as having 

a structure which, on heating, persisted to above 700°0, 

whereas heulandite showed a phase change at 

230°± 10°0. For sample B, the intensity of the diffraction peaks began to diminish at about 270°0 and the 

peaks disappeared at about 600°0. Mason and Sand 

(1960) state that heulandite and clinoptilolite have the 

same structure, but that heulandite is a calcium-rich 

zeolite and clinoptilolite is a sodium-potassium-rich 

1nineral. The leachate of sample B contained about 

three times as much calcium as sodium and potassium. 

These data indicate that the zeolite is better described, 

following Mason and Sand (1960), as heulandite than as 

clinoptilolite. 

An ammonium chloride batch method was used to 

determine the exchange capacity of the experimental 

material. The sample was crushed lightly to break up 

aggregates and then put through a 60-mesh sieve; no 

grinding was necessary except for some quartz and 

feldspar. One hundred fifty ml of 1.0 N NH40l solution 

neutralized with ammonium hydroxide was added to 

1 gram of sample. After soaking without agitation for 

specified times in covered beakers at room temperatures 

which ranged from 17°0 to 30°0, the mixtures were 

centrifuged and the supernatant liquids retained for 

cation analysis. To samples which were leached longer 

than 24 hours, distilled water was added periodically to 

maintain the volume. The samples were then washed 

4 times with ethyl alcohol, the first 2 washings being 

added to the supernatant liquid. The sodium and 

potassium in the supernatant liquid were analyzed by 

flame photometry; the calcium and magnesium by 

versene titration. The amount of ammonia adsorbed 

on the sa1nple was determined by distillation. 

Sample A, a soil containing montmorillonite, mica, 

kaolinite, quartz, and feldspar, as determined by X-ray 

diffraction, was run for comparative purposes. As can 

be seen on figure 139.1, sample A reached a constant 

value almost immediately, but the exchange-capacity 

values of sample B increased with time. The values are 

plotted on semilog paper. Other tuff samples, not 

shown, exhibited the same characteristics. 

In an attempt to reduce the long leaching times 

necessary to achieve a constant value in the observed 

capacities of the tuff, a series of experiments was 

carried out at a temperature (95 °0) just short of 

boiling, using the same leaching ti1nes as in the studies 

at roon1 temperature. As can be seen in figure 139.2, 

the heated samples reached a constant value at 84 

milliequivalents/100 grams in about 16 days. By 

extending both curves, and assuming no leveling off of 

the room-temperature curve, it appears that it would 

take at least 4 years to reach a constant value at room 

temperature. 

ART. 139 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D93-D95. 1964. 

D93 
D94 GEOCHEMISTRY 

60 

en 

~ 50 a:: 

<!l 

0 

8 40 a:: 

LLI 

a.. 

en 

~ 30 LLI 

....J 

<( 

::: 

:::::> 

0 20 LLI 

:::J 

....J 

~ 

B 

2 4 8 16 32 64 128 

DAYS 

FIGURE 139.1-Exchange capacity of samples A (soil) and B 

(zeolitlc tuff), determined at room temperature as a function 

of time. 

To see if the rate of exchange could be further 

increased, a series of runs was made in which the time 

remained constant at 24 hours but in which the temperatures were varied. The values produced a straight line 

when plotted on arithmetic graph paper (fig. 139.3). 

The highest temperature was obtained by heating the 

covered samples in an atn1osphere of 100 percent 

relative humidity in a household pressure cooker, which 

produced approximately 2 atmospheres of pressure. 

The temperature, 118°C, was calculated fron1 the 

pressure. The exchange capacity rneasured after 24 

hours was 84 meq/100 g, identical with that determined 

at 95°C, indicating that a constant value had been 

obtained. The pH of the arnmoniun1 chloride was 

lowered from 7.0 to 6.4. Increasing the heating time 

at 118 °C to 48 hours on another sample resulted in no 

change in the n1easured exchange capacity. 

~100 

<( 

a:: 

<!l 80 0 

8 

ffi 60 a.. 

en 

~ 40 LLI 

....J 

<( 

3 20 

0 

LLI 

:::J 

....J o~--~~~--~~--~....l-~--~~~--~-L--~-L 

~ 2 4 8 16 32 64 128 256 5121024 2048 

DAYS 

FIGURE 139.2.-Comparison of rates of exchange in zeolitic tuff, as determined at room temperatures and at 95°C. 

en 

::!: 

90 

80 

~ 70 

<!l 

§ 60 

a:: 

LLI 

a.. 50 

en 

~ 

z 

LLI 

....J 

<( 

::: 

:::::> 

0 

LLI 

:::J 

....J 20 

~ 

10 

0 

0 

0 

0 

0 0 

0 

0 

0 

0~--~--~--~--~--~--~--....l---....l---~--~ 

20 30 40 50 60 70 80 90 100 110 120 

DEGREES CENTIGRADE 

FIGURE 139.3.-Determined exchange capacity of zeolitic tuff 

(heated for 24 hours) as a function of temperature. 

As the exchange reaction approached a constant 

value, the ratio of the magnesium to the sum of the 

cations in the leachate increased (see accompanying 

table). In the unheated series the ratio increased fron1 

0.10 at half an hour to 0.20 after 128 days; in the series 

heated at 95 °C the ratio increased from 0.14 to 0.26. 

Ratios of 0.26 were also obtained for sarnples heated at 

118 °C for 24 and 48 hours. 

As determined by visual estimation of X-ray diffraction pattern, which may be in error by ± 10 percent, 

approximately a third of sample B is zeolite. If the 

determined exchange capacity is multiplied by 3 a value 

of 252 meq/100 g is obtained. This value is reasonable 

when compared with the exchange capacity of heulandite (330 meq/100 g) given by Barrer (1958), who obtained the value by calculation from the hydrated 

formula weight. 

Effect of time and temperature on exchange capacity and ratio of 

magnesium to sum of cations in zeolitic tu.ff 

Treatment 

Unheated (17°-30°C) ~hour ____________________ _ 

128 da~s __________________ --

Heated (95 C) ~hour ____________________ _ 

16 days ______________ ------

Heated (l18°C) 24 hours ___________________ _ 48 hours ___________________ _ 

Exchange 

capacity 

(meq/100 g) 

12. 8 

59. 2 

19. 6 

84. 0 

84.0 

84.0 

Ratio of mag- nesium to sum of cations 

0. 10 

. 20 

. 14 

. 26 

. 26 

. 26 
STARKEY D95 

Comparison of X-ray diffraction patterns made of 

samples both before and after treatment did not indicate any structural changes in the sample. 

In summary, the long period of time for the exchange 

reaction of son1e zeolites to reach a constant value at 

room temperatures n1ay be shortened by heating. The 

identical values obtained at both 95°C and l18°C indicate that heating does not alter the exchange capacity 

or the ratios of the cations. The increase, with time, 

in the ratio of magnesium to the sum of the cations 

indicates that the 1nagnesium 1s more difficult to exchange in this type of sample. 

REFERENCES 

Barrer, R. M., 1958, Crystalline ion-exchanges: Chern. Soc. 

(London) Proc., April 1958, p. 99-112. 

Mason, Brian, and Sand, L. B., 1960, Clinoptilolite from Patagonia; the relationship between clinoptilolite and heulandite: 

Am. Mineralogist, v. 45, p. 341-350. 

Mumpton, F. A., 1960, Clinoptilolite redefined: Am. Mineralogist, v. 45, p. 351-369. 
Article 140 

GEOLOGICAL AND GEOCHEMICAL RECONNAISSANCE, SOUTHERN PART OF THE SMYRNA 

MILLS QUADRANGLE, AROOSTOOK COUNTY, MAINE 

By LOUIS PA VLIDES and F. C. CANNEY, Beltsville, Md., and Denver, Colo. 

Abstract.-Closely folded Paleozoic rocks, mostly impure calcic 

and ankeritic limestone, micaceous siltstone and quartzite, and 

slate, comprise the principal sedimentary rocks of the southern 

part of the Smyrna Mills quadrangle. Felsic plutons locally 

have intruded and thermally altered these regionally metamorphosed rocks (chlorite zone) to cordierite-biotite and calc-silicate 

hornfels. Thus, the plutons are enclosed by hornfels aureoles 

up to 2 miles wide. Stream-sediment sampling revealed a 

slightly higher-than-background molybdenum content in four 

streams draining an area underlain by felsic rocks and plutons. 

Tests also were made for antimony, zinc, and heavy metals. 

Seasonal variations of copper and molybdenum were detected. 

Closely folded sedimentary rocks of Paleozoic age in 

the chlorite zone of regional metamorphism have been 

locally intruded and thermally metamorphosed by felsic 

plutons in the southern part of the Smyrna Mills 

quadrangle. Thin glacial till mantles much of the 

upland areas, whereas stratified deposits of sand and 

gravel cover the lowlands. The topography is controlled by the bedrock except for local eskers and 

kames. High ridges of hornfels surround areas of 

rounded and subdued hills and ridges underlain by 

felsic plutons (fig. 140.1). The northwest part of the 

area is underlain by folded sedimentary rocks and is 

mostly a lowland with gently rolling hills, except for 

the ridge formed by a small felsic mass and its 

associated hornfels aureole. 

The ribbon rock n1ernber of the Meduxnekeag Formation (Pavlides, 1962, p. 11-12 and 21-23) of Middle 

Ordovician and probably Late Ordovician age contains 

the oldest rocks of the region. It consists chiefly of 

thin- to mediun1-bedded gray-blue impure calcic and 

ankeritic limestones, interlayered with each other and 

with slate. Fossils have not been found in the green 

and gray-green phyllite that lies between the Meduxnekeag Formation and the Silurian rocks, and these 

phyllites can only be dated as of Late Ordovician or 

Early Silurian age or both. Locally this phyllite is 

calcareous and contains minor amounts of conglomerate. 

The undifferentiated Silurian rocks span Early 

through Late Silurian time as determined from the 

graptolite faunas identified by W. B. N. Berry (written 

communications, 1961, 1962) from several localities 

within them. Gray and gray-green micaceous siltstone 

and quartzite, commonly interlayered with gray and 

gray-green slate, are the dominant rock types in this 

unit; conglomerate is locally abundant. Manganeseand iron-bearing lenses are also present at several 

horizons. 

Calcareous slate that contains brachiopods of Silurian 

or Devonian age (A. J. Boucot, oral communication, 

1963) may be the youngest sedimentary unit of the 

area. 

The sedimentary rocks are closely folded along steep 

to vertical axial planes that trend east to northeast. 

Bedding normally dips 70 ° to vertical and well-developed fracture cleavage with equally steep dips trends 

east to the northeast, except in the northeast part of 

the area where it locally trends northwest. The final 

folding of the region occurred during the Acadian disturbance, following which the folded rocks were intruded 

by felsic plutons. 

The felsic plutons are not well exposed. The Hunt 

Ridge pluton appears to contain mostly fine to mediumgrained biotite-hornblende granodiorite, whereas in the 

Pleasant Lake pluton porphyritic medium- to coarsegrained hornblende-biotite quartz monzonite is present 

near the center and biotite granodiorite along the 

southwest margin. The two much smaller masses 

(fig. 140.1) are granitic. Thermal aureoles up to 2 

miles wide rim the plutons and consist of cordieritebiotite and calc-silicate hornfels in which stratification 

is preserved but cleavage is obliterated. On the northeast side of the Hunt Ridge pluton, hornfels formed 

ART. 140 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D96-D99. 1964. 

D96 
Su 

Granodiorite and 

quartz monzonite 

Calcareous slate 

~ 

Undifferentiated 

~ sedimentary rocks 

H 

~ ~ :::a:::z 

cr:oo 

::l > ..J LJJ 

- Cl (f) 

PAVLIDES AND CANNEY 

0 2 MILES 

CONTOUR INTERVAL 200' 

EXPLANATION 

u <( 

;o::O: 

~ z 

oO::J 

Cl ..J a:: -

~ ]~ m 

Phyllite 

~ > 

Meduxnekeag Formation, ~ ribbon rock member 0 

e 

Thermally metamorphosed 

sedimentary rocks 

Diagonal dashes indicate 

injected zones 

~~!~] Thermally metamorphosed 

phyllite 

Thermally ~ metamorphosed 

Meduxnekeag Formation, 

ribbon rock member 

Inferred contact Inferred fault 

.40 

Sample locality 

D97 

FIGURE 140.1.-Reconnaissance bedrock geology and stream-sediment sample sites, southern part of Smyrna Mills quadrangle, 

Maine. 
D98 GEOCHEMISTRY 

from sedimentary rocks of Silurian age is intruded by 

sills and minor dikes of granodiorite, quartz monzonite, 

and granite of Devonian age. 

Many magnetic anomalies, some of considerable 

magnitude, are present in the hornfels aureoles (Dempsey, 1962). The formation of abundant magnetite by 

thermal metamorphism of the ferruginous lenses present in the undifferentiated Silurian unit is believed to 

be the cause of these local magnetic anomalies. 

Small amounts of galena, chalcopyrite, and stibnite 

occur in quartz veins in hornfels on the east side of 

Meduxnekeag Lake (Houston, 1956, p. 109-110), just 

beyond the east margin of figure 140 .1. 

A reconnaissance geochemical drainage survey was 

made in 1960 and 1961 of the felsic plutons and their 

aureoles. Samples of fine-grained active stream sediment were collected at the 41 sites shown on figure 

140.1. The samples were dried, screened through a 

50-mesh sieve (0.25-mm opening), and the fine fractions (lg to 25g) analyzed by geochemical prospecting 

field methods (Ward and others, 1 963). All samples 

were analyzed for copper, lead, zinc, molybdenum, 

cold-extractable copper, and cold-extractable heavy 

metals (see accompanying table); the 1960 samples 

were also analyzed for tungsten and antimony. 

In general, the values are quite low and with a few 

exceptions fall within normal background ranges elsewhere in Maine in similar geologi~ terrane. Interpretation of these data, however, is complicated because 

the copper and molybdenum contents of the active 

alluvium in some of the streams appear to show time 

variations. 

The eight paired samples listed in the table were 

collected in 1960 and 1961. The data for these show 

that the copper and rnolybdenum contents of rnany of 

the 1961 samples are appreciably lower than the corresponding 1960 values. No significant differences 

were noted in the zinc content, however. Although 

the variability between the 1960 and 1961 copper and 

molybdenum values is such that no single normalizing 

factor would be entirely correct, all the data for these 

can be made more directly comparable by doubling 

the 1961 values wherever a definite figure is given. 

Variations in the metal content of stream sediments 

with time are known to exist. Barr and Hawkes (1963), 

who 'described time variations in the copper content of 

the stream sediments in two areas in British Columbia, 

also noted a weak inverse relationship between stream 

discharge and metal content of the sediments. In the 

Smyrna Mills area, too, both rainfall and average 

strean1 dischargP were distinctly less in the summer 

of 1960 than in the corresponding period of 1961. The 

Partial chemical analyses of stream-sediment samples taken in 

1960 and 1961 in the southern part of the Smyrna Mills quadrangle, Maine 

[Asterisk on sample number indicates 196I sample. Analyses by G. A. Nowlan, G. H. Van Sickle, and M. J. Bright, Jr.] 

Metal content (parts per million) 1 

Site Sample Cold-ex- Cold-ex- Cu Zn Mo Sb tractable tractable Cu heavy 

metals 2 

-------------- l_ ____ ------------ AI580 15 100 <4 I I 11 2 ___ -------------- I 58 I 20 100 4 1 <1 25 3 ___ -------------- I579 I5 IOO <4 2 1 11 4 ___ -------------- 1576 40 100 <4 1 3 17 5 ___ -------------- 1575 30 100 4 .5 2 14 6 ___ -------------- *1728 30 175 <4 -------- 2 35 7----------------- *1729 <10 100 <4 -------- <1 9 8 ___ -------------- 1577 30 100 4 1.5 <1 9 

9_ ---------------- 1578 10 75 <4 1 <1 4 10 ___ ------------- *1725 10 50 <4 -------- <1 2 1L _______________ *1726 <10 50 <4 -------- <1 7 12 ___ ------------- *1727 10 75 <4 -------- <1 9 13 ________ -------- *1724 10 50 <4 -------- <1 4 14 ___ ------------- *1722 10 75 <4 <1 7 15 ___ ------------- 1558 20 110 12 1 <1 20 *1742 10 100 6 -------- <1 3 16 ___ ------------- 1556 20 80 3 <.5 <1 11 *1741 5 75 2 -------- <1 11 

17---------------- 1555 10 80 6 .5 <1 4 *1740 10 90 3 -------- <1 5 18 ______ ---------- 1721 15 50 <4 -------- <1 5 19 ___ ------------- 1720 10 50 <4 -------- <1 9 20 ____________ --- 1554 10 75 6 <.5 <1 3 *1739 5 75 3 -------- <I 3 21_ __________ ---- 1553 20 60 12 .5 <I 7 *1738 10 75 4 -------- <1 4 22 ___ ------------- 1571 20 100 4 1 2 7 23 _____ ----------- 1570 30 100 4 1.5 <1 5 24 __________ ------ 1569 40 100 4 1.5 <1 7 25 ___ ------------- 1568 30 100 4 1.5 1 7 26 ___ ------------- 1573 15 100 4 .5 <I 4 

27---------------- 1572 30 100 4 1 <1 9 28 __________ - ----- I567 30 75 4 .5 <I 9 29 ___ ------------- I574 20 IOO 4 I I 5 30 ___ ------------- I566 5 60 6 <.5 <I 7 *I743 5 70 2 -------- <I 7 31_ ______ --------- I732 20 IOO 4 -------- I 7 32 ___ ------------- I73I I5 75 8 -------- I 9 33 ___ ------------- I730 I5 IOO 8 -------- <I 9 34 ___ ------------- I565 20 100 24 .5 <1 7 *1733 20 80 8 -------- <I 7 35 _____ ----------- 1735 <10 100 8 -------- <1 25 36 ________________ 1736 10 75 4 -------- <1 9 

37---------------- 1737 <10 75 8 -------- <1 5 38 _____ ----------- 1723 <10 50 <4 <I 3 39 ____ ------------ 1564 IO 110 16 1 <1 4 *I734 IO 75 16 -------- <I 2 40 ________________ 1563 30 75 4 1 <1 5 41_ _______________ I562 I IO 75 4 .5 <I 4 

I 

1 Lead (all samples)~25 ppm. Tungsten (I960 samples only)<20 ppm. 2 Undifferentiated copper, lead, and zinc, expressed as equivalent parts per million zinc. 

reasons for such variations of metal content are imperfectly understood. Because the metal content 

normally is higher in the finer fractions of a sediment 

sample, possible variations in the average grain size of 

the sediment with stream discharge must be considered. For the Smyrna Mills samples, however, 

mechanical analyses revealed only erratic and generally small differences in the percentage of fines between 

corresponding sample pairs. 

In at least 4 streams (sites 15, 21, 34, and 39) that 

drain areas underlain either by the Hunt Ridge pluton 

or its contact zone, the molybdenun1 content is slightly 

anon1alous if background is taken as 4 ppm or less. 

Appraisal of these weak anon1alies is in1possible on the 

basis of the available data because little is known about 
PAVLIDES AND CANNEY D99 

the dispersion of molybdenum from molybdenitebearing rock in the northern Appalachians. Several 

fel3ic plutons elsewhere in eastern and southeastern 

Maine, however, are associated with small noneconomic deposits of n1olybdenite (Canney and others, 

1961). The n1olybdenun1 anomalies in the two strean1s 

in the southern part of the Hunt Ridge pluton (sites 34 

and 39) can be considered slightly more significant 

because their watersheds are contiguous and the contrast of the anon1alies is slightly greater. 

The sample at site 6 from a stream draining the 

northwestern contact zone of the Hunt Ridge pluton 

is weakly anomalous in zinc (175 ppm), cold-extractable heavy metals (35 pp1n), and possibly anomalous 

in copper. However, we believe that this anom<tly is 

caused by contamination, because much metallic trash 

is present in the headwaters of the stream. 

REFERENCES 

Barr, D. A., and Hawkes, H. E., 1963, Seasonal variations in 

copper content of stream sediments in British Columbia 

[abs.]: Mining Eng., v. 15, p. 61. 

Canney, F. C., Ward, F. N., and Bright, M. J., Jr., 1961, Molybdenum content of glacial drift related to molybdenitebearing bedrock, Aroostook County, Maine: Art. 117 in 

U.S. Geol. Survey Prof. Paper 424-B, p. B276-B278. 

Dempsey, W. J., 1962, Aeromagnetic map of the Smyrna Mills 

quadrangele, Aroostook County, Maine: U.S. Geol. Survey 

Geophys. Inv. Map GP-294. 

Houston, R. S., 1956, Genetic study of some pyrrhotite deposits 

of Maine and New Brunswick: Maine Geol. Survey Bull. 

7, p. 1-117. 

Pavlides, Louis, 1962, Geology and manganese deposits of the 

Maple and Hovey Mountains area, Aroostook County, 

Maine: U.S. Geol. Survey Prof. Paper 362 [1963]. 

Ward, F. N., Lakin, H. W., and Canney, F. C., 1963, Analytical 

methods used in geochemical exploration by the U.S. 

Geological Survey: U.S. Geol. Survey Bull. 1152. 
Article 141 

AGE OF BASEMENT ROCKS FROM THE WILLISTON BASIN OF NORTH DAKOTA AND 

ADJACENT AREAS 

Bv Z. E. PETERMAN and C. E. HEDGE, Washington, D.C. 

Abstract.-Eleven Rb-Sr age determinations of bottom-hole 

well samples confirm subsurface extensions of the Churchill and 

Superior provinces of the Canadian Shield in the Williston basin 

of North Dakota and of adjacent areas. The boundary between the Churchill (1.7 b.y.) and the Superior (2.5 b.y.) provinces trends south through western North Dakota. 

Recent radioactivity dating of rocks from the 

Canadian Shield by laboratories in the United States 

and Canada has indicated that the geologic provinces 

of the shield (fig. 141.1) originally defined on the 

basis of dominant structural trends, rock types, 

and mineralization (Wilson, 1941; Gill, 1949; Wilson, 

1949) are age provinces as well. Tracing of these age 

provinces in the subsurface is possible by radioactivity 

dating of basement samples obtained in deep oil-well 

tests. The Williston basin area is of special interest 

because of the availability of samples of basement 

rocks and because of the existence of two age provinces. 

Eleven samples, including 8 K-feldspar concentrates 

and 1 whole-rock sample from drill cores and 2 biotite 

separates from drill cuttings, were dated by the Rb-Sr 

method. The approximate location of the wells in 

North Dakota, Montana, and Saskatchewan is shown 

on figure 141.2 (locs. 1-11). Well names, locations, 

and sample descriptions are given in table 141.1. The 

material dated, analytical data, and computed ages are 

given in table 141.2. Potassium-argon age determinations for biotite, hornblende, and pyroxene from seven 

of the cores, as well as other samples fr01n the area, 

have been reported earlier by Burwash and others 

(1962) and by Peterman (unpublished PhD. thesis, 

1962). Sample depths below the Precambrian contact 

range from a few feet to 150 feet. These ages are 

included in table 141.2 or are shown on figure 141.2. 

The writers are indebted to R. A. Burwash, University 

of Alberta at Edmonton; J. P. Gries, South Dakota 

School of Mines and Technology, Rapid City, S. Dak.; 

and H. L. Hurley, Amerada Petroleum Corp., Williston, 

N. Dak., for supplying the samples. 

The shield area of northern Saskatchewan and northern Manitoba is part of the extensive Churchill province 

which was last affected by a major orogeny 1.7-1.8 b.y. 

(109 years) ago. In Minnesota and adjacent regions 

this event is called the Penokean orogeny (Goldich and 

others, 1961), whereas in Canadian terminology it is 

TABLE 141.1.-Descriptions of dated samples from oil-well tests to the basement 

Locality Location (fig. 141.1) Sample Well 1---------l Sample depth (feet) Rock type 

Sec. T. R. -------------------·--------1----1--------1----------------

L _ _ _ _ _ _ 3633 

2----- -- 3634 3 _______ 4219 

4- - - - - - - 4483 

5_------ 4234 

6 _______ 3798 

7------- 4679---

8_ _ _ _ _ _ _ BT--8.5 __ 9 _______ 4678 

10 ______ BT-86 

1 L _ _ _ _ _ 4680 

D100 

Mobile Oil Woodley Sinclair 21 

Cantuar X-2-21. 

British American Wilhelm 1-9 _ _ 9 

Ceepee Bail don 2-11 _ _ _ _ _ _ _ _ _ _ 11 

Imperial Stoughton 3-27 _ _ _ _ _ _ _ 27 

Socony Western Prairie Imperial 4 

Carievale 1. 

Shell N. P. 32-33B ____________ 33 

Amerada 1 Iverson-Nelson Unit_ 2 

Amerada N.D. "A" Unit 9 ____ 16 

Amerada 1 Antelope Unit A_ _ _ _ 1 

Amerada 8 Scoria Unit_________ 10 

Herman Hanson 1 Mueller_____ 20 

16 

17 

15 

8 

3 

22 N. 

155 N. 

156 N. 

1.52 N. 

139 N. 

140 N. 

17 W.3 

14 W.3 

26 W.2 

8 W.2 

32 W.1 

48 E. 

96 w. 

95 w. 

95 w. 

101 w. 

65 w. 

7,285-7, 305_ _ _ _ Porphyritic biotite granite. 

6, 735-6,7 55_____ Porphyritic rhyolite. 

7, 738 _ _ _ _ _ _ _ _ _ _ Biotite-quartz monzonite. 

8,830 _ _ _ _ _ _ _ _ _ _ Cordierite gneiss. 

8,328 _ _ _ _ _ _ _ _ _ _ Biotite-quartz monzonite. 

11' 0.50- - - - ----- 13.603 ________ _ 

14,825-14,827---

15,128 ________ _ 13,645 ________ _ 

3,305 

Pegmatite and amphibolite. 

Altered svenite. 

Garnet-biotite gneiss. 

Hornblende-hypersthene gneiss. 

Biotite-quartz monzonite (?). 

Biotite-quartz monzonite. 

ART. 141 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl00-Dl04. 1964. 
PETERMAN AND HEDGE DlOl 

PRINCIPAL AGES OF METAMORPHISM 

[IJJ 

"'1.0 b.y. 

"'2.5 b.y. 

150 0 150 300 MILES ~~~----~-----

FIG URE 1~1.1_.-Structural provinces of the Canadian Shield showing age of major orogenies. Combinations of patterns show some pnnc1pal areas of mixed isotopic ages resulting from overlap of orogenic belts. Boundaries between provinces arc shown by dotted lines. 

called the Hudsonian orogeny (Stockwell, 1961). The 

western part of the Superior province includes the shield 

areas of Ontario and parts of Manitoba and northern 

Minnesota. Rocks from this province yield ages commonly ranging from 2.4 to 2.6 b.y. and represent the 

Algoman (Goldich and others, 1961) or Kenomn (Stockwell, 1961) orogeny. In the exposed Precambrian of 

northern Manitoba, the boundary between the Churchill 

and Superior provinces is marked by well-developed 

faulting, ultramafic intrusions, and a regional gravity 

low paralleled by gravity highs. On the basis of 

geologic and gravity data, Innes (1960) and Wilson ltnd 

Brisbin (1961) have suggested that this :wne is the 

remnant of an island arc or alpine mountain system. 

The gravity anomalies (Innes, 1960; Wilson and Brisbin, 

1961) and the K-Ar ages of subsurface samples (Burwash and others, 1962) indicate a southward extension 

of the boundary zone in the subsurface to the international border. The location of the boundary in 

Nor·th Dakota, as shown in figure 141.2, is a projection 

from Canada fitted to the isotopic ages of basementrock samples. The terminology used in this report is 

that of Goldich and others (1961). 
D102 GEOCHRONOLOGY 

TABLE 141.2.- Rb-Sr and K-Ar agPs of samples of basement rocksf1·om the Williston bas1:n area 

[K-Ar ages from Burwash and others (1962), except Nos. 3 and 6 (hornblende), from Peterman (unpublished PhD. thesis, 1962)] 

Locality 

(fig. 141.1) 

Material 

Hb-Sr 

Rb" (ppm) 

Radiogenic 

Sr" (ppm) 

Radiogenic Sri' 

Total Sr" 

Age (b.y.) Age (b.y.) 

K-Ar 

Mineral 

----- - --------------- ------------ 1---------------1----1---------

1_ _ _ _ _ _ _ _ _ K-feldspar __________ ____ _____ _ 2 _______ __ vVhole rock ___ _____ _______ ___ _ 

3 _ _ _ _ _ _ _ _ _ K-felrlspar_ _______ _______ __ __ _ 4 ___ _______ ____ do __ ____ ________________ _ 

5 ____ _________ _ do _____ ___ ____ _________ _ _ 6 ______ ___ _____ do __________________ ____ _ 

7 ___ __________ _ do _____________ ______ ___ _ 

8 ______ ___ Biotite (t\Yo ______ __ ____ ___ __ _ 

determinations) ____ __________ _ 9 _________ K-feldspar ________ ______ ____ _ 1 0 _ _ _ _ _ _ _ _ Biotite ______________ ________ _ 

I L __ ____ K-fcldspar_ __________________ _ 

184 

52. 1 

95. 8 . 61. 8 

64. 8 

75. 6 

(\.5. 1 

128 

128 

131 

187 

103 

Decay constants, ab undances, and normal isotopic ratios used in 

RbB7: 1.47X 10- 11 yr- 1 

K40: 0.585X 10-10 yr- 1 (electron capture) 

4.72 X I0- 10 y r- 1 (beta decay) 

Rb'7: 0.283 g/g Rb 

K40 : 1.22X IO- •g(g K 

SrR7fSrS6= 0.703 (assumed initial) 

Sr86(Srss= 0.1194 

1 10' 

45! • 

. 1.8 

I 50 ' 

106' 

SASKATCHEWAN 

3. 

1.8 I . 7 

4. 5.5 0 .. 52 1. 66±. 08 1. 20 

1. 33 . 12 1.71 ± .19 1. 49 

2. 52 . 12 1. 77±. 19 1. 71 

2. 35 . 24 2. 54±. 15 1. .'i7 

1. 63 . 16 1. 69 ± . Hi l. 51 

2. 02 . 10 l. 79 ± . 22 1. 72 

l. 77 

<- 90 <- 01 <- 93 - - ---- --

. 992 . 3.5 . 52 ±. 03 - - - - - -- -

. 988 . 37 . 52 ± . 03 - - - --- - -

3. 32 . 16 1. 70 ± . 15 2. 20 

4. 32 .77 1. 55±. 08 --------

3. 29 . 25 2. 1-! ± . 13 --- --- --

calculations: 

MANITOBA 

I 

4. 

2.5 1.6 '· so. 1.9 

48' 

0 

I 52. L s. Z4 -- ---- --.. CANADA I 5 UNITJins1-:U:Es-··- -- -- 1 -- - -- ----··u .. ~ -- -- -- -- ---------~,-__ -- --

18 . 19.._ I. 7 

. ~~4 I ! 8 ·. W 7~0.5 ILLISTON \ 0.9.9 

1.7 

MONTANA 

6. 

!.B I. 7 NORTH DAKOTA 

54. 2.5 

11. 

2.1 

\ 

46' ·- ·- - ··-··- ··--·--·-··---- --------·-··--·--) 100 

Exposed Precambrian 

Shield rocks 

200 MILES 

EXPLANAT ION 

Boundary zone between subsurface 

extension of Churchill province 

to west and Superior province to 

east 

/ Locality 6

•1. 7 K-Ar age, b.y. 

!.B, Rb-Sr age, b.y. 

... Outcrop samples, Little 

Rocky Mountains 

\ 

FraunE 141.2.-Rb-Sr and K-Ar ages of samples of basement rocks from the Williston basin 

of North Dakota and of adjacent areas. Locality numbers 1- 11 refer to this article (see 

tables 141.1 and 141.2); locality num bers 18, 19, 45, and 50-54 refer to Burwash and others (I 962). . 

Biotite. Hornblende. Biotite. 

Do. 

Do . Do. 

Hornblend e. 

Hypersthene . 
PETERMAN AND HEDGE D103 

DISCUSSION 

Isotopic ages, ranging fron1 0.5 to 2.5 b.y., are available for a total of 18 localities in an area of over 220 000 ' 

square miles (fig. 141.2). The age determinations, 

however, fall into a useful and interpretable pattern 

(fig. 141.3). Two n1ajor periods of metan1orphism and 

orogeny, the Algoman approximately 2.5 b.y. ago and 

the Penokean approximately 1.7 b.y., are indicated and 

one or rnore younger events suggested. The pattern 

of ages, in part, shows the cumulative effects of two or 

more thermal events in which the Rb-Sr and 1{-Ar 

systems are variously affected in different rninerals. 

For example, at locality 4 in Saskatchewan, the Rb-Sr 

age of 2.5 b.y. for feldspar indicates an Early Precanlbrian rock, and the l{-Ar age of 1.6 b.y. for biotite 

reflects the Penokean event at the close of Middle 

Precambrian time. Similarly, at locality 50 in Manitoba a K-Ar age of 1.93 for biotite was reported by 

Burwash and others (1962, p. 1621). The hornblendebiotite gneiss represented in the core is probably also of 

Early Precan1brian age. If the lowering of the K-Ar 

age is attributed to the Penokean event 1.7-1.8 b.y. ago, 

as is suggested in figure 141.3, loss of the radiogenic 

argon was incomplete, and the somewhat older a~e of 

1.9 b.y. for the biotite may be referred to as a sur~ival 

value. The quartz monzonite cored at locality 5 

between localities 4 and 50 rnay have been emplaced 

during the Penokean orogeny. The Rb-Sr age for 

feldspar fron1 this rock is 1.7 b.y., and the K-Ar age for 

biotite is 1.6 b.y. 

Early 

Precambrian 

Algoman 

orogeny 

Middle Precambrian 

Penokean 

orogeny 

The pattern of the isotopic ages frmn east to west 

clearly indicates that two age provinces are present in 

the basenwnt rocks. The buried Precan1brian rocks 

of Manitoba are related to the Superior province of 

the Canadian Shield exposed to the east in Manitoba ' Ontario, and Minnesota. The buried basement rocks 

of southestern Saskatchewan show isotopic ages that 

are characteristic of the Churchill province. There 

appears to be a broad transitional zone (fig. 141.2) 

between the Superior province age of 2.4-2.5 b.y. 

and the Churchill province age of 1.7-1.8 b.y. A 

similar broad zone of rnixed ages, between 2. 5 and I. 7 

b.y., was found (Lowdon and others, 1963; Burwash 

and others, 1962; Moore and others, 1960) for rocks 

of the Superior province adjacent to the ChurchillSuperior boundary zone in northern Manitoba (fig. 

141.1). 

The subsurface extension of the Superior province 

in eastern North Dakota is indicated by K-Ar ages of 

2.4-2.5 b.y. for biotite from gneissic rocks at localities 

53 and 54 (Burwash and others, 1962). K-feldspar 

from a quartz monzonite cored at locality 11 was 

dated at 2.14 b.y. The analytieal error is estin1ated 

at ± 130 m.y. (table 141.2), but it cannot be assun1ed 

that the feldspar rernained a closed systmn. It cannot 

be said, therefore, whether the determined age rnarks 

the time of origin of the quartz rnonzonite or represents 

a survival value. 

The ages for the sarnples from western North 

Dakota, Montana, and Saskatchewan give the peak at 

Late Precambrian j Paleozoic 

Unknown events 

D K-Ar 

~< ] Rb-Sr 

1.5 1.0 0.5 

AGE, IN B.Y. (10 9 YEARS) 

FIGURE 141.3.-Bar graph of Rb-Sr and ~-Ar age determinations shown in figure 141.2. Locality numbers are indicated. Termmology is that of Goldich and others (1961). 
D104 GEOCHRONOLOGY 

1.7 b.y. shown in the histogram (fig. 141.3). The 

Rb-Sr age of 1.7 b.y. for the whole-rock sample of 

rhyolite (loc. 2) and 5 feldspar ages in the range 1.66 

to 1.79 b.y. suggest a specific event, the Penokean. 

The range of 130 m.y. in the ages may represent 

differences in ages of the igneous rocks, but analytical 

errors must also be considered, and the time differences 

rnay be apparent rather than real. The Rb-Sr ages, 

however, are rnore consistent than the K-Ar ages for 

which the overall analytical precision of 5 percent is 

generally n1uch better than that of the Rb-Sr rnethod. 

The K-Ar age of 1.2 b.y. for biotite from the granite 

at locality 1 clearly indicates some disturbance in the 

area subsequent to the Penokean orogeny, and this is 

substantiated by Rb-Sr ages of 520 m.y. for biotite 

(loc. 8) and of approximately 900 m.y. for K-feldspar 

(loc. 7). 

Altered syenite was cored at a depth of 13,603 feet 

at locality 7. The age of 930 m.y. (table 141.2) computed for K-feldspar from the syenite is a maximum 

value, and the age calculation is uncertain because of 

the small content of radiogenic Sr87• The biotite with 

a Cambrian age of 520 m.y. is from a garnet-biotite 

gneiss cored at a depth of 14,825 feet. The low ages 

at localities 7 and 8 might be attributed to thermal 

effects due to the depth of burial except that K-feldspar 

from a hornblende-hypersthene gneiss at locality 9, 

cored at a depth of 15,128 feet, had an Rb-Sr age of 

1.7 b.y. Hypersthene from this core was dated by 

K-Ar at 2.20 b.y., but this age is suspect because it 

has been shown that pyroxenes may contain excess 

argon (Hart and Dodd, 1962). 

It should be noted that the wells at localities 7 and 

8 were drilled on a basement high. Localities 1 and 2, 

which yielded low K-Ar ages for biotite, are also a 

basement high. Possibly these high points of the buried 

basement were centers of later igneous or metamorphic 

activity. The Little Rocky Mountains in Montana 

(locs. 18 and 19) contain Tertiary intrusive rocks in 

Precambrian gneisses. The Penokean age of 1.7 b.y. 

(fig. 141.2) represents K-Ar ages for hornblende from 

the gneisses (Burwash and others, 1962). 

CONCLUSIONS 

The major part of the Williston basin of western 

North Dakota and adjacent areas is underlain by Precambrian rocks which yield isotopic ages of 1. 7-1.8 

b.y., indicating that the buried basement rocks are an 

extension of the Churchill province of the Canadian 

Shield. The eastern part of the basin is floored by a 

subsurface extension of the Superior province with 

rocks approximately 2.5 b.y. in age. The projection 

of the Churchill-Superior boundary trends southward 

through eastern Saskatchewan and western North Dakota. Mixed isotopic ages in the range 2.5 to 1.6 b.y. 

indicate that Early Precambrian rocks were affected in 

varying degree by the Penokean orogeny approximately 

1. 7 b.y. ago. The Churchill-Superior boundary in the 

subsurface, as delimited by isotopic age determinations, 

probably is a broad zone rather than a sharp line. 

Younger thermal events in the area are indicated by 

Rb-Sr and K-Ar ages in the range 0.5 to 1.5 b.y. 

The data, however, are too few for evaluation, and 

these ages may represent survival values via updating 

through Tertiary activity or one or more events in 

Late Precambrian or Cambrian time. 

REFERENCES 

Burwash, R. A., Baadsgaard, H., and Peterman, Z. E., 1962, 

Precambrian K-Ar dates from western Canada sedimentary basin: Jour. Geophys. Research, v. 67, no. 4, p. 

1617-1625. 

Gill, J. E., 1949, Nat ural divisions of the Canadian shield: Royal 

Soc. Canada Trans., sec. 4, v. 43, p. 61-69. 

Goldich, S. S., Nier, A. 0., Baadsgaard, H., Hoffman, J. H., and 

Krueger, H. W., 1961, The Precambrian geology and 

geochronology of Minnesota: Minnesota Geol. Survey, 

Bull. 41, 193 p. 

Hart, S. R., and Dodd, R. T., Jr., 1962, Excess radiogenic argon 

in pyroxenes: Jour. Geophys. Research, v. 67, no. 7, p. 

2998-2999. 

Innes, M. J. S., 1960, Gravity and isostasy in northern Ontario 

and Manitoba: Canada Dominion Observatories Pub., v. 21, 

no. 6, p. 263-338. 

Lowdon, J. A., Stockwell, C. H., Tipper, H. W., and Wanless, 

R. H., 1965, Age determinations and geological studies: 

Canada Geol. Survey Pap. 62-17, 140 p. 

Moore, J. M., Jr., Hart, S. R., Barnett, C. C., and Hurley, P. M., 

1960, Potassium-argon ages in northern Manitoba: Geol. 

Soc. America Bull., v. 71, no. 2, p. 225-230. 

Stockwell, C. H., 1961, Structural provinces, orogenies, and time 

classification of rocks of the Canadian Precambrian Shield: 

Canada Geol. Survey Pap. 61-17, p. 108-118. 

Wilson, H. D. B., and Brisbin, W. C., 1961, Regional structure of 

the Thompson-Moak Lake nickel belt: Canadian Mining 

and Metall. Bull., no. 595, p. 815-822. 

Wilson, J. T., 1949, The origin of continents and Precambrian 

history: Royal Soc. Canada Trans., sec. 4, v. 43, p. 157-184. 

Wilson, M. E., 1941, Pre-Cambrian; in Geology, 1888-1938 

(Fiftieth anniversary volume); Geol. Soc. America, p. 269-

305. 
Article 142 

ISOTOPIC AGES OF GLAUCOPHANE SCHISTS 

FROM THE AREA OF CAZADERO, CALIFORNIA 

By D. E. LEE, 1 H. H. THOMAS, 2 R. F. MARVIN, 2 and R. G. COLEMAN, 1 

1 Menlo Park, Calif./ Washington, D.C. 

Abstract.-Glaucophane-bearing tectonic blocks are stratigraphically out of place with respect to the glaucophane-bearing 

bedrock terrain on which they rest. Five isotope age determinations ranging from 130 to 150 m.y. indicate that both the 

tectonic blocks and the bedrock schists were recrystallized as 

part of a Late Jurassic and Early Cretaceous metamorphic event. 

Field study has shown that muscovite-bearing 

glaucophane schists are present in two different structural positions within the Franciscan Formation in the 

area of Cazadero, Sonoma County, Calif., north of the 

San Francisco area (fig. 142.1) (Coleman and Lee, 

1963). Glaucophane-bearing tectonic blocks are stratigraphically out of place with respect to the glaucophanebearing bedrock terrain on which they rest. Laboratory study shows also that the tectonic blocks can be 

distinguished mineralogically from the bedrock terrain, 

even though glaucophane and muscovite are present 

in both (Coleman and Lee, 1963; Lee and others, 1963). 

This article presents isotope-age data determined for 

muscovites from three samples of tectonic blocks 

(type-IV rocks of Coleman and Lee) and two samples of 

bedrock schist (type-III rocks). 

Franciscan rocks designated types III and IV are 

described by Coleman and Lee (1963) as follows: 

Bedrock glaucophane schists [type III] as exemplified by a 

conformable sequence of metabasalts and metasediments exposed at the bottom of Ward Creek canyon near Cazadero, 

California. Some of the minerals present along with glaucophane and muscovite in these rocks are aragonite (Coleman and 

Lee, 1962), lawsonite, and almandine-spessartine-grossular 

garnet. 

Coarsely crystalline gneissic schists [type IV] that occur as large 

isolated blocks; these blocks cannot be mapped as in place or as 

stratigraphically equivalent to the bedrock terrain on which 

they rest. Some of the minerals present along with glaucophane 

and muscovite in these rocks are epidote, rutile, and almandinegrossular garnet. The mineral assemblages present in these 

tectonic blocks indicate that they were recrystallized at higher 

pressure-temperature conditions than were the bedrock schists. 

Near Cazadero these tectonic blocks are concentrated in a band 

that conforms to some of the major faulting in the area. 

The K-Ar and Rb-Sr ages of muscovite from 

glaucophane schists near Cazadero (fig. 142.1) are 

listed in the accompanying table. Potassium was 

determined by a flame photometer using lithium as an 

internal standard. Rubidium and strontium were 

determined by isotope-dilution techniques described 

by Goldich and others (1961, p. 8-35). The overall 

analytical error is approximately ± 5 percent of the 

quoted age value. 

Although type-III glaucophane schists may be distinguished from those of type IV, both on the basis of 

mineralogy and on the basis of field occurrence, the 

isotope-age results listed in the table indicate that both 

type-III and type-IV rocks were recrystallized as part 

of a metamorphic event that took place during Late 

Jurassic and Early Cretaceous time (Holmes, 1960). 

Pending further isotope-age work on these rocks, it 

appears that some of the glaucophane schists in this 

area represent the metamorphic equivalents of volcanic 

and sedimentary rocks that were laid down during preCretaceous time. 

ART. 142 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES, Dl05-D107. 1964. 

D105 
D 

Landslide area 

EJI2] 

Sandstone 

~>- ~0:: 

<(<( 

:JZ 

}

%>- o::O:: 

w<( 

~ 

Graywacke, 

~ shale, and 

conglomerate 

D 

Greenstone 

J 

EXPLANATION 

lll~~l~lfillfillfll Serpentine 

,., .-1 

Gneissic glaucophane schist 

(tectonic blocks, type IV) 

otll Z:J ~ b.=...::::J j' <( 0 Bedrock metamorphosed to 

~ ~ glaucophane schist facies 

~ <( (includes type III) 

O::o::- <(Gi 

:J u Contact ., _.....------.... Fault 

Dashed where approximately located 

J. W. Stewart, and 

A 

Sample locality 

FIGURE 142.1.-Geologic map of area surrounding Ward Creek, Cazadero, Calif. 

Area of 

report 

··-··-·i 

0 : 

'P I 

-(': 

...,.~""·· 0 '·· 

.L-. 'l"-<t> '· ., 

~ ·, 

'1 } 

__ j 

0 

....... 

0 

OJ 

0 

l"J 

0 

(") 

~ 

~ 

0 

z 

0 

~ 

0 

0 

~ 
LEE, THOMAS, MARVIN, AND COLEMAN 

Analytical data and isotopic ages of muscovite from glaucophane schists in the area of Cazadero, Calif. 

[Analysts: Potassium-argon age, H. H. Thomas, R. F. Marvin, Paul Elmore, and Ivan Barlow; rubidium-strontium age, F. G. Walthall and W. D. Long] 

Potassium-argon age 

Map locality Field No. Host rock 2 K20 K40 *Ar4o 

(fig. 142. 1) (percent) (ppm) 

A ____________ 55-CZ-59 ________ Type-IV metabasalt ___________ 8. 81 8. 92 0. 0805 

(1) ---- - - - - - - - - 27-CZ-60 ________ B ____________ 50-C Z-60 ________ A ____________ 201-RGC-59!_ ____ A ____________ 26-CZ-59 ________ 

Map locality Field No. 

(fig. 142. 1) 

A ____________ 55-CZ-59 ________ 

Constants: K40Xe =0.585 X lQ-1°/year 

K40X{3 =4.72 X 10-1°/year 

K40=1.22X10-4 gm/gm K 

Symbol: * radiogenic. 

Type-IV metabasalt ___________ 9. 96 10. 09 

Type-IV metabasalt ___________ 9. 06 9. 18 

Type-III metashale ____________ 8.41 8. 52 

Type-III metashale ____________ 7. 62 7. 72 

Rubidium-~Lrgon age 

Host rock 2 RbB7 Normal Sr 

(ppm) (ppm) 

Type-IV metabasalt ___________ 73:73 21. 8 

Rb87X{3= 1.47 X 10-11 /year 

Rb87 = 0.283 gm/gm Rb 

1 Near Moffitt Ranch Road, SW~4 sec. 11, T. 10 N., R. 12 W., Tombs Creek quadrangle, 7).-2-minute series, California. 

2 Type-III rocks are bedrock glaucophane schists; type-IV rocks are tectonic blocks (Coleman and Lee, 1963). 

. 0858 

. 0750 

. 0694 

. 0596 

*SrB7 

(ppm) 

0. 164 

Ar4o *Ar40fK4o 

(percent) 

94 0. 00902 

86 . 00850 

88 . 00817 

94 . 00815 

92 . 00772 

*SrB7 *SrB7fRbB7 

(percent) 

9. 7 0. 02224 

D107 

Age 

(m.y.) 

150 

140 

135 

135 

130 

Age 

(m.y.) 

150 

REFERENCES 

Coleman, R. G., and Lee, D. E., 1962, Metamorphic aragonite 

in the glaucophane schists of Cazadero, California: Am. 

Jour. Sci., v. 260, p. 577-595. 

Goldich, S. S., Nier, A. 0., Baadsgaard, H., Hoffman, J. H., and 

Krueger, H. W., 1961, The Precambrian geology and 

geochronology of Minnesota: Minnesota Geol. Survey 

Bull. 41, 193 p. 

--- 1963, Glaucophane-bearing metamorphic rock types of 

the Cazadero area, California: Jour. Petrology, v. 4, p. 

26Q-301. 

716-62'6 0-64--8 

Holmes, Arthur, 1960, A revised geological time-scale: 

Edinburgh Geol. Soc. Trans., v. 17, pt. 3, p. 183-216. 

Lee, D. E., Coleman, R. G., and Erd, R. C., 1963, Garnet types 

from the Cazadero area, California: Jour. Petrology, 

v. 4, no. 3, p. 460-492. 
Article 143 

CRUSTAL STRUCTURE IN THE VICINITY OF LAS VEGAS, NEVADA, 

FROM SEISMIC AND GRAVITY OBSERV AllONS 

Bv JOHN C. ROLLER, Denver, Colo. 

Work done under Advanced Research Projects Agency Order No. 193-62 

Abstract.-According to a seismic-refraction profile the thickness of the crust north of the Las Vegas Valley shear zone is 

32 km, but it thins to 27 km, south of that structure, within the 

short distance of 25 km. This decrease correlates with an increase in the Bouguer anomaly and a decrease in the average 

surface altitude. The data imply that (1) major fracture zones 

may extend to the Mohorovicic discontinuity, and probably 

penetrate the mantle, and (2) the Mohorovicic discontinuity is 

not flat, but instead includes major flexures over relatively short 

horizontal distances. 

The U.S. Geological Survey recorded a seismic-refraction profile 265 kilometers long frmn a shot point near 

Kingman, Ariz., northwest across the Las Vegas Valley 

shear zone (Longwell, 1960) toward the Nevada Test 

Site (NTS) during June 1962 (fig. 143.1). Seismic 

waves, generated by 4 chemical explosions that ranged 

in size from 2,000 to 10,000 pounds, were recorded at 

24 positions. 

Standard seismic-refraction procedures and wide-band 

recording on both photographic paper and magnetic 

tape were used in the field (Warrick and others, 1961). 

Recording positions were spaced approximately 10 km 

apart along the profile, and at each position 6 vertical 

seismometers were spaced 0.5 km apart in a line generally parallel to the line of profile. Two horizontal 

seismometers (radial and transverse) were placed beside 

one of the vertical seismometers. 

The area traversed by the seismic profile is characterized by a series of mountain ranges composed mainly 

of Paleozoic sedin1entary rocks and Tertiary volcanic 

rocks. The ranges are separated by alluvial basins 

(Bowyer and others, 1958). The profile crosses a major 

geologic structure, the Las Vegas Valley shear zone, 

north of Las Vegas, Nev. (fig. 143.1). North of this 

zone the ranges and many geologic features strike 

generally north and the average surface altitude is 

significantly higher than in the area south of the shear 

zone, where the structural and topographical pattern 

is more complex (Longwell, 1960). 

The generalized Bouguer anomaly contours (fig. 

143.1) show a relatively flat, although locally conrplex, 

pattern immediately south and east of Las Vegas, and a 

general regional decrease to the north. The Bouguer 

anomaly contours are based on data fron1 stations on 

pre-Tertiary bedrock. 

This profile approximately reverses a seismic-refraction profile recorded by the U.S. Geological Survey from 

NTS to Kingn1an during nuclear testing in 1957 and 

1958 (Diment and others, 1961). 

RESULTS 

Results of observations of the previous profile, from 

NTS to Kingrnan, show that the crust is about 28 km 

thick with an apparent compressional-wave velocity of 

6.15 km/sec, and is underlain by the n1antle with an 

apparent velocity of 7.81 km/sec (Diment and others, 

1961). These data were based on first-arrival direct 

waves (Pg) through the crust from NTS to a point 

near Boulder City, Nev., and on first-arrival waves 

refracted along the mantle from Boulder City to a 

point near Kingman. The reversed profile fron1 

Kingman toward NTS indicates a thin surface layer 

with an apparent velocity of 5.2 km/sec overlying a 

crustal layer with an apparent velocity of 6.1 km/sec 

(fig. 143.2). 

The seismic waves that are refracted from the n1antle 

(P n) south of the Las Vegas Valley shear zone fit a 

line with an apparent velocity of 7.8 km/sec, and 

indicate that the crust is 27 km thick. P n waves that 

are refracted from the mantle north of the shear zone 

ART 143 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl08-Dlll. 1964. 

D108 
ROLLER 

38~1r6_o __________________________ ~115o 

EXPLANATION 

oH-3 

Recording station 

• Shot point 

.,.-----,/~0_____., 

Bouguer gravity contour 

0 10 20 30 MILES 

0 10 20 30 40 50 KILOMETERS 

FIGURE 143.1.-Index map showing the location of the Kingman, Ariz., shot point, seismicrecording stations, and generalized Bouguer anomaly contours. The Bouguer anomaly 

contours are from Diment and others (1961). 

D109 
DllO GEOPHYSICS 

en 

0 

z 

0 

u 

SOUTH 

Shot point 

Kingman 

+1 

~ -1 

z 

\0. -2 

' <J 

I 

~ -3 

t= 

-4 

NORTH 

> ..J -50 ceen 

:::i!:..J -70 0c( z(!) -90 c(:J 

[r= -110 

W:::i!: -130 :::> 

---::::;.::..-..::..-.:z(!_~~oretical (0"=0.4 gm/cc) 

------------------=--===----==-=---

(!)Z -150 :::>-

0 -170 III 5 MEAN Ground-surface profile 

SEA LEVEL 

5 

zen 10 -[r 

WI- ·w 15 Ow 20 :::>:::!: 

t:::o 25 1-..J ..J- cell:: 30 

35 

0 50 100 150 200 250 

DISTANCE FROM SHOT POINT, IN KILOMETERS 

FIGURE 143.2-Seismic and gravity profiles, showing traveltimes of first arrivals in the report area, generalized theoretical 

and observed Bouguer anomalies for the seismic crustal model, and the crustal boundary as computed from seismicrefraction data. Location numbers refer to recording stat,ions shown in figure 143.1. 

are delayed 0.55 sec with respect to those south of the 

shear zone, and indicate a crustal thickness of 32 km. 

The change in thickness occurs within a horizontal 

distance of 25 km or less, and may even be due to a 

vertical or near-vertical displacement. The P n arrivals 

at station Q-3 and possibly at P-3 (fig. 143.1) that 

produce the apparent slope in the flexure (fig. 143.2) 

could actually be diffracted waves from a fault-type 

structure (Heiland, 1 940). The delayed arrivals may 

be related in part to the thickening of Paleozoic sedimentary rocks northwest of Lake Mead. The seismic 

profile crosses the Las Vegas Valley shear ·zone in the 

same general area that the Paleozoic section increases 

in thickness (Bowyer and others, 1 958). 

The above crustal n1odels were con1puted assuming 

flat layers with constant velocities. The velocity in 

the crust probably increases with depth, as shown by 

several authors (Berg and others, 1960; Healy, 1963; 

and Ryall and Stuart, 1 963), so these depths are 

minimums. The relative depths should be correct, 

however. 

The first-arrival tin1es (fig. 143.2) that define the 5.2-

knl/sec line and the 6.1-km/sec line are the uncorrected 

observed times. Arrival times that define the P n 

lines have been corrected for low-velocity material near 

the surface, either from gravity and seisrnic data or by 

estimating the thickness of these low-velocity sediments 

from the geologic environment of the recording positions. The seismograms also contain rnany secondary 

arrivals, the discussion of which is beyond the scope of 

this article. 

The observed Bouguer anomaly profile (fig. 143.2) 

shows a general regional correlation with the crustal 

cross section, as con1puted fron1 a delay-time analysis 

of the seis1nic-refraction data (Pakiser and Black, 

1 957). An area of relatively high Bouguer gravity 

values is observed over the thinner crust, and an area 

of lower gravity values is observed over the thicker 

crust. 

Two theoretical Bouguer anon1aly curves based on 

assumed density contrasts between the crust and mantle 

of 0.4 g/cc and 0.5 g/cc were computed (fig. 143.2). 

If a density of 3.3 g/ce for the rnantle is assurned, 

which corresponds to a compressional-wave velocity of 

7.8 krn/sec (Talwani and others, 1959), the density 

contrast of 0.5 g/cc gives a crustal density of 2.8 g/cc, 

which corresponds to the observed P g velocity of 6.1 

km/sec. The density contrast of 0.4 g/cc corresponds to 
ROL·LER Dlll 

a compressional-wave velocity of 6.5 km/sec and a 

density of 2.9 g/cc. The theoretical curve using a density 

contrast of 0.4 fits the observed curve within 10 n1gals. 

This may indicate an increase in crustal velocity with 

depth. 

The most significant difference between the theoretical and the observed Bouguer anomalies is that the 

gradient on the observed eurve is steeper, which indicates that only part of this gradient ean be attributed 

to the erust-mantle boundary; part n1ust be attributed 

to density eontrasts within the crust. Inunediately 

east of Las Vegas, the trends of the gTavity contours 

deviate northward fr01n the shear zone and generally 

follow a line between predominantly Paleozoic outerops 

to the northwest and Precambrian outcrops to the 

southeast. 

The surface altitude of the area also shows a general 

eorrelation with the seismie and gravity data (Mabey, 

1960). South of the shear zone the average altitude is 

less than 1 km above sea level and the Bouguer anomaly 

is about -100 mgals. North of the shear zone the 

altitude above sea level averages about H~ lu11 and the 

Bouguer an01naly decreases to -160 mgals at station 

H-3. 

Three major implieations ean be drawn from these 

data: major fracture zones may extend to the 

Mohorovicie discontinuity and probably penetrate the 

mantle; the Mohorovieic diseontinuity is not a flat 

surface but may inelude 1najor flexures over relatively 

short horizontal distances; and in the report area there 

is a regional eorrelation between thickness of the crust, 

Bouguer gravity anomaly, and average surface altitude. 

REFERENCES 

Berg, J. W., Jr., Cook, K. L., Narans, H. D., and Dolan, W. M., 

1960, Seismic investigations of crustal structure in the 

eastern part of the Basin and Range province: Bull. Seismol. 

Soc. America, v. 50, p. 511-536. 

Bowyer, Ben, Pampeyan, E. H., and Longwell, C. R., 1958, 

Geologic map of Clark County, Nevada: U.S. Geol. Survey 

Min. Inv. Map MF -138. 

Diment, W. H., Stewart, S. W., and Roller, J. C., 1961, Crustal 

structure from the Nevada Test Site to Kingman, Arizona, 

from seismic and gravity observations: Jour. Geophys. 

Research, v. 66, p. 201-214. 

Healy, J. H., 1963, Crustal structure along the coast of California 

from seismic-refraction measurements: Jour. Geophys. 

Research, v. 68, p. 5777-5787. 

Heiland, C. A., 1940, Geophysical exploration: New York, 

Prentice-Hall, p. 514-521. 

Longwell, C. R., 1960, Possible explanation of diverse structural 

patterns in southern Nevada: Am. Jour. Sci., v. 258-A, p. 

192-203. . 

Mabey, D. R., 1960, Regional gravity survey of part of the Basin 

and Range province: Art. 130 in U.S. Geol. Survey Prof. 

Paper 400-B, p. B283-B285. 

Pakiser, L. C., Jr., and Black, R. A., 1957, Exploring for ancient 

channels with the refraction seismograph [Ariz.-Utah]: 

Geophysics, v. 22, p. 32-47. 

Ryall, Alan, and Stuart, D. J., 1963, Traveltimes and amplitudes 

from nuclear explosions-Nevada Test Site to Ordway, 

Colorado: Jour. Geophys. Research, v. 68, p. 5821-5835. 

Talwani, Manik, Sutton, G. H., and Worzel, J. L., 1959, A 

crustal section across the Puerto Rico trench: Jour. Geophys. 

Research, v. 64, no. 10, p. 1545-1555. 

Warrick, R. E., Hoover, D. B., Jackson, W. H., Pakiser, L. C., 

and Roller, J. C., 1961, The specification and testing of a 

seismic-refraction system for crustal studies: Geophysics, 

v. 26, p. 820-824. 
Article 144 

HAWAIIAN SEISMIC EVENTS DURING 1962 

By ROBERT Y. KOY ANAGI, Hawaiian Volcano Observatory 

Abstract.-Six hundred ninety two earthquakes of magnitude 

2.0 and greater were recorded in the Hawaiian Islands region 

during 1962. Most of these quakes were of magnitude less than 

3%, and only one was of magnitude greater than 6. The Kaoiki 

fault, the east rift of Kilauea, the Kalapana Trail region, and 

Kilauea caldera at 30 km depth . were areas of concentrated 

earthquake activity. 

The U.S. Geological Survey Volcano Observatory 

maintains a seismic net primarily for monitoring seismicity of the island of Hawaii. Limitations on station 

location imposed by the 'geographic linearity of the 

Hawaiian Islands leads to moderate uncertainty in the 

determination of focal depths and epicenters beyond the 

Hawaii Island net. Nevertheless, it is possible to 

locate earthquakes of magnitude greater than 2.5 

beneath the island of Hawaii within a 5-kilometer sphere 

of error. Similar quakes offshore are subject to an 

uncertainty in location of perhaps 10 km. 

Epicenter-location maps and lists presented here were 

compiled from the work of the author, Arnold Okamura, Harold Krivoy, and George Kojima. With some 

exceptions, these epicenters have been reported by 

Koyanagi and others (1963), Okamura, Koyanagi, and 

Krivoy (196"3), Okamura, Kojima, and Yamamoto 

(1963), and Krivoy and others (1963); quakes smaller 

than n1agnitude 2.0 were not reported. Epicenter, 

depth, and magnitude determinations are based on 

travel-time studies and methodology instituted and 

applied at the Hawaiian Volcano Observatory by Jerry 

P. Eaton between 1956 and 1961. Generally, all earthquakes of magnitude 2.5 and greater which occur in the 

Hawaiian Ridge, within the geographical coordinates 

lat. 18° N. to 23° N. and long. 154° W. to 161° W., 

are detected by the island of Hawaii seismic network. 

A map of Hawaiian earthquake distribution prepared 

by Eaton for the period April 1958 to September 1959 

showed a high earthquake concentration in the southeast sector of the island of Hawaii (Eaton, 1962, p. 14). 

A similar pattern of distribution was noted in 1962. 

Throughout 1962, many earthquakes took place in 

the region of the east rift zone of Kilauea (fig. ·144.1). 

Most of these epicenters plot south of the surface trace 

of the rift zone (figs. 144.2 and 144.3), and hence support 

the concept that the rift dips south (Richter and others, 

1 964). 

160" 155" 

156°W 

FIGURE 144.1.-Map of the island of Hawaii, showing significant 

geologic features and towns used for earthquake-epicenter location references. The five volcanic systems are after Macdonald 

( 1956). Contour interval is 2,000 feet; datum is I?ean sea lev~l. 

Lines made up of dots and dashes are boundanes of volcamc 

systems. 

Three other conspicuous zones of seismic activity 

during 1962 were Kilauea caldera, at a depth of 30 

ART. 144 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D112-D117. 1964. 

D112 
KOYANAGI D113 

km; the Honuapo-Kaoiki fault systen1, at a depth of 

5 to 8 km; and the Kalapana Trail region, at a depth of 

about 3 km. In plotting quakes of these groups, 

symbols were placed at the respective epicenters, and 

quakes of magnitude 2.0 and greater were counted for 

each quarter year. 

HIGHLIGHTS OF EARTHQUAKE ACTIVITY 

The first quarter of 1962 (fig. 144.2, top) was marked 

by a swarm of 30-km-deep quakes which began on 

February 7 and diminished greatly in frequency by 

the following day. Several of these were felt; the 

largest exceeded magnitude 4. 

During the second quarter the Honuapo-Kaoiki 

fault system, on the southeast boundary of Mauna 

Loa, was the site of greatest activity (fig. 144.2, bottom). For several weeks, 15 to 20 small quakes were 

recorded daily in that area until the evening of June 

27 (HST), when a quake of magnitude 6.1 occurred. 

Several thousand aftershocks were recorded in diminishing frequency during the week that followed; 

however, most of the aftershocks were smaller than 

magnitude 2. 

In the third quarter there was a pronounced increase 

in activity off the west coast of Hawaii (fig. 144.3, 

top). Two shocks of shallow origin were felt throughout the island on July 23 and 24; the magnitudes 

were 4.5 and 4.9, respectively. Numerous deeper 

earthquakes occurred throughout this quarter off the 

southwest shore of the island of Hawaii. 

In the fourth quarter, increased activity was noted 

on the south and west flanks of Mauna Loa (fig. 144.3, 

bottom). Also, a flurry of intermediate-depth quakes 

was recorded in the Mauna Kea region in November 

and Decernber. 

A swarm of quakes began on November 20 and continued until November 23 in the Kalapana Trail 

region, on the southeast flank of Kilauea. Several of 

these were felt by some residents of the eastern section 

of the island, but most were of magnitude less than 2 

and were not felt. 

On December 7, 8, and 9 a sn1all eruption occurred 

in and near Aloi Crater (about 10 km from Kilauea 

caldera on Kilauea's east rift). At about 1930 hours 

(HST) December 6, harmonic tremor and small shallow 

quakes commenced. These shallow quakes originated 

several kilometers southeast of Kilauea caldera along 

the east rift zone and are grouped as "Upper east 

rift zone" on figure 144.3 (botton1). At about 0100 

hours (HST) on December 7, an eruption began at 

Aloi Crater. Tren1or and quakes decreased and died 

out on December 9 after five more small eruptive outbreaks in the same region. 

Earthquakes recorded by the volcano observatory 

but outside the area of figures 144.2 and 144.3 are 

listed in the accompanying table. 

Earthquakes in 1962 within lat 18° N. to 23° N., long 154° W. 

to 161 ° W., and outside the area shown in figures 144.2 and 144.3 

[All times are Hawaiian standard time] 

Time (hrs., 

Date min., sec.) Location, depth, magnitude 

Jan. 10 16:59:52. 1 125 km northeast of Upolu Point, 

Hawaii, at a depth of 12% km; long 

155°25' W., lat 21 °16' N. Magnitude 

2.9. 

Feb. 1 

Feb. 10 

Feb. 23 

April 8 

May 1 

June 22 

June 29 

June 29 

19:30:08. 3 

16:00:46. 6 

19:03:59. 3 

07:08:15. 4 

18:58:13. 4 

00:21:59. 1 

14:41:53. 0 

21:13:33. 0 

25 km east of Cape Kumukahi (eastern 

point of Hawaii) at a depth of 127~ km; 

154°35' W., 19°31' N. Magnitude 2.5. 

35 km southeast of Cape Kumukahi at a 

depth of 3 km; 154°33.0' W., 19°18.2' 

N. Magnitude 4.0. 

102 km north-northeast of Upolu Point 

at a depth of 127~ km; 155°38' W., 

21 °09' N. Magnitude 2.8. 

70 km west-southwest of Kealakekua, at 

a depth of 8 km; 156°33.0' W., 19°16.0' 

N. Magnitude 2.8. 

117 km southwest of Kealakekua at a 

depth of 12% km; 156°40' W., 18°40' 

N. Magnitude 3.7. 

128 km northeast of Kamuela at a depth 

of 12% km; 155°01' W., 20°58' N. 

Magnitude 2.9. 

87 km north-northeast of Upolu Point at 

a depth of 127~ km; 155°22' W., 20°52' 

N. Magnitude 3.0. 

85 km west-southwest of Upolu Point at 

a depth of 12.% km; 156°39' W., 20°06' 

N. Magnitude 2.7. 

July 16 13:03:53. 6 62 km south-southeast of Apua Point at a 

depth of 127~ km; 15.5°01' W., 18°14' 

N. Magnitude 2.8. 

Aug. 1 09:57:39. 2 100 km northeast of Upolu Point at a 

depth of 127~ km; 155°08' W., 20°57' 

N. Magnitude 3.0. 

Aug. 13 22:32:06. 0 40 km southeast of Cape Kumukahi at a 

depth of 5 km; 154°34' W., 19°14' N. 

Magnitude 2.4. 

Sept. 19 03:29:45. 1 55 km north-northeast of Upolu Point at 

a depth of 12% km; 155°49' W., 20°46' 

N. Magnitude 2.8. 

Sept. 20 22:46:05. 9 108 km east-northeast of Upolu Point at 

a depth of 12% km; 155°01' W., 20°46' 

N. Magnitude 3.7. 

Sept. 28 12:44:43. 7 165 km northwest of Upolu Point at a 

depth of 127~ km; 156°47' W., 21 °27' 

N. Magnitude 3.3. 

Oct. 17 21:59:01. 0 1.;20 km west-southwest of Upolu Point at 

a depth of 12% km; 156°59' W., 20°05' 

N. Magnitude 3.0. 

Dec. 21 16:20:08. 0 140 km east-northeast of Upolu Point at 

a depth of 8 km; 154°38' W., 20°40' 

~. Magnitude 2.8. 
D114 GEOPHYSICS 

Numbers of quakes of I 

Location of magnitude 2.0 to 3.5 i 

concentrations (first figure) and >3.5 I 

of quakes (second figure) 

1st quarter 2nd quarter 

Kilauea area Q) 42,4 36,3 

(30 km depth) 

Kalapana Trail ® 17,0 26,1 

area 

Kaoiki fault ® 52,3 

system 

Depth (km) Magnitude 

2.0-3.5 >3.5 

<IO • 0 

10-20 + + 20-60 X X 

+ + 

........... : ............ .......... ......__ ." '-.. 

\ ""'-. + + \ "------·-·-· 

j X X 

+.-· -· 

X t 

• + + 

•• 

A-.~/ 

"""" ............. . +"' . '""" . ......__ \ ""' ...__.-·-·-·-· ., 

.. . . .../ ·-·;;- . /. 

•/ ........... 

x-·-··/ • //" • ++ -

• •a/ _:(Dt, _____ _.--ox 

; // '.-.- @, 

I ,/ 

I .· t t + I ~/ + 

+ 

I 

/. 

!. 

I -' 

I 

+ 

+ 

FIGURE 144.2.-Epicenter plot of 

earthquakes of magnitude 2.0 and 

greater for the first quarter of 1962 

(top) and second quarter (bottom). 

The large number of quakes located 

30 km beneath Kilauea and those 

located along the Kalapana Trail 

and Kaoiki fault system were counted and listed numerically. 

Epicenters which were located off 

the map are listed in the accom- panying table. Geographic names are shown on figure 144.1.s 
Location of 

concentrations 

of quakes 

Kilauea area <D 

(30 km depth) 

Kalapana Trail ® area 

Kaoiki fault ® 

system 

Upper east @) 

rift zone 

Depth (km) 

<10 

10-20 

20-60 

Numbers of quakes of 

magnitude 2.0 to 3.5 

(first figure) and >3.5 

(second figure) 

3rd quarter 4th quarter 

23,2 20,1 

25,0 19,2 

26,0 15,0 

6,0 

Magnitude 

2.0-3.5 >3.5 

• 0 

+ + X X 

+ 

·-.......... ............ "· ''---.. "' ++ + ............. + 

+ 

I 

I 

KOYANAGI 

+ 

+ 

• + 

+ 

* 

+ 

\ + "· . , '-.-·-·-·-· 

• • 

I •• / 

+ -·-I 

II 

•• 

I + 

+ 

• 

D115 

+ 

+ 

'"'-. """ . .......... .'---.. 

I I 

'\ . 

~\ + ""'· . '-.......-·-·---· 

\ 

__ ........ ~-~ .. + 

0 

• 

FIGURE 144.3.-Epicenter plot of 

earthquakes of magnitude 2.0 and 

greater for the third quarter of 1962 

(top) and fourth quarter (bottom) . The large number of quakes located 

30 km beneath Kilauea and those 

located along the Kalapana Trail, 

Kaoiki fault system, and upper east 

rift zone were counted and listed 

numerically. Epicenters which were located off the map are listed in 

the accompanying table. Geographic names are shown on figure 

144.1. 
D116 GEOPHYSICS 

NUMBER OF QUAKES FOR 1962 

336 186 25 

~ 

5 

(/) 

IJJ 70 :::.:: 

<( 

:::> 

0 

1..1... 

0 

0::: 

IJJ 

co 

~ 

:::> 

z 

10 

1 2 3 4 

15 <( 

:J Z<( 

<( :JO ..J <(..J 

~ ~ 

<( :3 

Z<( <( :JW I <(~ 0 

~ ~ 

9 

<( 

..J 

<( 

..J 

<( 

:J 

I 

year 

EXPLANATION 

D 

20-60 km deep 

(deep) 

IJ 

10-20 km deep 

(intermediate) 

0-10 km deep 

(shallow) 

L__ Active ___) '---- Dormant or extinct -----' 

VOLCANOES 

FIGURE 144.4.-Bar graph showing earthquakes of magnitude 2.0 or greater on, and offshore from the island 

of Hawaii in 1962. ' 

VOLCANOES AND SEIS'MICITY 

Seismic activity on the island of Hawaii during 1962 

was greatest beneath IGlauea Volcano (fig. 144.4), 

although the number of quakes in the Mauna Loa 

region was also high. Seventy-five percent of all 

quakes were from the Mauna Loa and Kilauea systems. 

The large nmnber of quakes originating from a highly 

seismic zone at a depth of 30 km beneath Kilauea 

caldera was responsible for the high count of deep 

quakes from the Kilauea system. However, 66 percent of the quakes from Mauna Loa and Kilauea were 

of shallow origin. Many shallow quakes occurred 

north of the Honuapo-Kaoiki fault systmn and therefore have been assigned to the Mauna Loa system 

(fig. 144.4). Such quakes, located near the surface 

trace separating two volcanic systems, have been 

assigned somewhat arbitrarily to one system or the 

other. 

The dormant or extinct volcanoes Hualalai, Mauna 

I\:ea, and Kohala accounted for few earthquakes in 

comparison with the active volcanoes Kilauea and 

Mauna Loa. 

A relatively high proportion of offshore quakes were 

assigned to intermediate-depth sources. Seismograms 

of earthquakes more than 50 km from the nearest 

station yield little information on focal depth; therefore, "normal" depth travel-time curves are used to 

locate them. 

Relative to previous years, there was in 1962 a 

Inarked decrease in the number of quakes deeper than 

30 km. This fact is not obvious on the maps and bar 

graph but it marks an important difference between 

1962 and recent years since 1956. Those years were 

characterized by almost quarterly swarms of thousands 

of quakes beneath Kilauea and Mauna Loa from 

depths between 45 and 60 km. Such deeper events 

prior to 1962 (and their sudden cessation) are being 

studied further. 

REFERENCES 

Eaton, J. P., 1962, Crustal structures and volcanism in Hawaii, 

in Macdonald, G. A., and Kuno, Hisashi, eds., Crust of the 

Pacific Basin: Am. Geophys. Union Geophys. Mon. 6, 

p. 13-29. 

Koyanagi, R. Y., Krivoy, H. L., and Okamura, A. T., 1963, 

Hawaiian Volcano Observatory summary: U.S. Geol. Survey Hawaiian Volcano Observatory Summary 25 (Jan., 

Feb., and March 1962). [In press] 

Krivoy, H. L., Koyanagi, R. Y., Okamura, A., and Kojima, G., 

1963, Hawaiian Volcano Observatory summary: U.S. Geol. 

Survey Hawaiian Volcano Observatory Summary 28 (Oct., 

Nov., and Dec. 1962). [In press] 

Macdonald, G. A., 1956, The structure of Hawaiian volcanoes: 

Gravenhage, K. Nederlandsch Geol.-Mijn. Genootschap 

Verh. Geol. Ser., Deel 16, p. 274-295. 
KOYANAGI D117 

Okamura, A. T., Koyanagi, R. Y., and Krivoy, H. L., 1963, 

Hawaiian Volcano Observatory summary: U.S. Geol. Survey Hawaiian Volcano Observatory Summary 26 (April, 

May, and June 1962). [In press] 

Okamura, A. T., Kojima, G., and Yamamoto, A., 1963, Hawaiian 

Volcano Observatory summary: U.S. Geol. Survey Hawaiian Volcano Observatory Summary 27 (,Tuly, Aug., and 

Sept. 1962). [In press] 

Richter, D. H., Ault, W. U., Eaton, J. P., and Moore, J. G., 

1964, The 1961 eruption of Kilauea Volcano, Hawaii: U.S. 

Geol. Survey Prof. Paper 474-D. [In press] 
Article 145 

SEISMIC INVESTIGATIONS ON CAPE COD, MASSACHUSETTS 

By R. N. OLDALE and C. R. TUTTLE, Boston, Mass. 

Work done in cooperation with the Massachusetts Department of Public Works and U.S. Bureau of Public Roads 

Abstract.-Seismic studies on Cape Cod show that sedimentary 

deposits of post-Paleozoic age, ranging from 250 to possibly 

more than 960 feet in thickness, overlie crystalline basement 

rocks. A trough in the basement surface extending to about 

900 feet below sea level was found on outer Cape Cod near 

Truro. 

Thirteen seismic-refraction traverses made on Cape 

Cod between 1958 and 1963 form the basis for interpretations presented here. Additional traverses in 

the Harwich and Dennis areas have been reported 

previously (Oldale and others, 1962). Three of the 

13 traverses reported were made in the Faln1outh area 

in October 1958 to determine the nature of the surficial 

deposits and the depth to bedrock along the proposed 

relocation of Massachusetts Route 28. The 10 other 

traverses, made for a similar purpose, were along the 

outer arm of Cape Cod between Orleans Beach and 

Race Point (fig. 145.1). Nine of these traverses were 

made in 1962 (Oldale and Tuttle, 1962); the other, an 

unreversed traverse (traverse 3, fig. 145.1), was made 

in 1960 at Pilgrim Spring State Park in Truro at a 

deep borehole drilled by the Woods Hole Oceanographic 

Institution (Zeigler and others, 1960). 

All seismic traverses were of the inline refraction 

type. Traverses before 1962 were made with a 12-

channel portable refraction amplifier and oscillograph. The 1962 traverses were made using the same 

equipment coupled in "series" with a 12-channel refraction amplifier and oscillograph designed to record 

very low frequencies. The original equipment was 

used to record the first set of 12 geophones, and the 

very low frequency equipment recorded a second set 

of 12 geophones. Traverses in the Fahnouth area 

were 1,100 feet long and those made in 1962 on outer 

Cape Cod between Orleans Beach and Race Point 

were 1,800 to 2,100 feet long. The unreversed traverse 

made at Pilgrim Spring State Park in 1960 was 1,555 

feet long. Thickness of layers and the depth to bedrock were calculated for each traverse, using recorded 

velocities and critical distances. 

OUTER CAPE COD 

The upper two seismic layers (L1 and L2) recorded in 

this area probably represent unconsolidated deposits of 

Pleistocene or, in places, possibly of Tertiary age. A 

third seismic layer (L3) recorded at traverse 4 may 

represent semiconsolidated or consolidated deposits of 

Cretaceous(?) age. 

The uppermost layer (L1), having velocities of 1,300 

to 3,800 feet per second, was recorded at traverses 4, 7, 

and 8 (see accompanying table). This layer, which is 

thought to represent the unsaturated Pleistocene glacioThickness of the seismic layers, and depth, altitude, and average 

seismic velocity of the basement rocks at 13 traverses on Cape 

Cod 

[Minimum thickness, depth, and altitude indicated where traverse was not long enough to detect underlying material] 

Thickness of layers (feet) Computed Traverse depth to (fig. 145.1) basement 

-Lt -, zr-Ls (feet) 

k 3 _____________ ~~~=~=====~=I========== ---------- 4_____________ 60 

5_-- ---------- ---------- 6 _____________ ··--------- 7_____________ 30 8 _____________ 50 

9_--- --------- ---------- 10 ____________ ----------

n ___ ----- -~ 12_--

13_-------------------- ~I 80 

Outer Cape Cod 

510 

510 

>620 

. 440 

390 

400 

470 

480 

470 

400 

>460 

Falmouth Area 

~ 1--------1 180 ---------- 170 ---------- I 

510 

510 

>620 

>960 

390 

400 

500 

530 

470 

400 

250 

~I 250 

Altitude of 

basement, mean 

sea lev<>l 

datum 

(feet) 

-500 

-500 

>-580 

>-910 

-380 

-3i0 

-450 

-480 

-430 

-390 

-150 -100 I -160 

Average 

seismic 

velocity of 

basement 

(feet/ 

second) 

21,250 

21,250 

14, 750 19, 500 19,200 

23,500 

14, 100 20,500 

15,450 

17,750 

12,150 

ART. 145 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D-118-D122. 1964. 

Dl18 
OLDALE AND TUTTLE D119 

70'30' 70' 15' 70'00' 

~Truro 0 

9T\ 

CAPE COD \ 

41 '45' 

~11 

113 0 

BAY 

5 

Dennis 

0 

10 MILES 

Eastham 

O<l:s:t., .. "' 

0 10~ Beach 

Harwich 

0 

Falmouth 

0 L_L_L_L_L_L_ ________ j 

FIGURE 145.1.-Map of Cape Cod showing the location of seismic traverses described. Symbol shows approximate azimuth, hut 

not length, and number of seismic traverse. 

fluvial deposits above the water table, ranges from 30 to 

60 feet in thickness. A second layer (L2 ) was recorded 

at all traverses and has average velocities in the range 

from 4,700 to 5,700 fps. The L2 layer presumably represents glaciofluvial sand and gravel of Pleistocene n.ge 

underlain by sand, silt, and clay of Pleistocene and, in 

some places, of Tertiary age (Woodworth and Wigglesworth, 1934, and Zeigler and others, 1960). 

At traverse 3 the L2 layer is made up of 2 distinct 

acoustic layers with velocities of 4,600 and 5,900 fps. 

This traverse was made at a deep borehole drilled by 

the Woods Hole Oceanographic Institution at Pilgrim 

Spring State Park that found Eocene deposits at a 

depth of only 86 feet, overlain by materials of Pleistocene age. However, the contact between the acoustic 

layers was at 17 5 feet, indicating no correlation between 

the acoustic boundaries and geologic-time boundaries at 

this site. 

Two seismic traverses (1 and 2, fig. 145.1) near 

Province~own in the vicinity of a second borehole made 

by the Woods Hole Oceanographic Institution indicated 

average velocities of 5,250 and 5,500 fps, respectively, 
D120 GEOPHYSICS 

for the L~ layer. The borehole penetrated 193 feet of 

glaciofluvial material above 10 feet of sand and silt of 

Eocene age (Zeigler and others, 1960). The seismic 

data gave no suggestion of this contact, indicating that 

materials of Pleistocene and Eocene age have similar 

acoustic characteristics. Therefore, it is impossible to 

tell from. seismic data alone whether unconsolidated 

deposits of Tertiary age occur beneath the Pleistocene 

glaciofluvial deposits in this part of Cape Cod. The 

L 2 layer ranges in thiclmess from 390 feet at traverse 5 

to more than 620 feet at traverse 3, where the traverse 

was not long enough to detect the velocity and depth of 

the underlying material. 

The absence of velocities in the 6,000 to 9,000 fps 

range indicates that there is little or no compact till 

beneath the glaciofluvial deposits in this part of Cape 

Cod; compact till commonly has velocities between 

6,000 and 9,000 fps in other parts of Massachusetts 

(Tuttle, 1961). Near Harwich, Mass., material having 

an average seismic velocity of 10,500 fps and underlying 313 feet of stratified drift was identified in a borehole as compact till (Koteff and Cotton, 1962). In 

seismic studies in the Harwich and Dennis areas, material having velocities of 6,000 to 11,000 fps and overlain by 82 to 357 feet of stratified drift has been interpreted to be compact till (Oldale and others, 1962). 

A third seismic layer (L3) recognized at traverse 4 is 

thought to represent sem.iconsolidated or consolidated 

deposits overlying crystalline basement rocks. The 

average velocity computed for the material below the 

L2 layer at this traverse is 12,100 fps. This velocity 

is about 7,000 fps slower than the average of the velocities of crystalline basement rocks in the area and more 

than 2,000 fps slower than the lowest basement velocity 

recorded in this area by the authors. Similar velocities 

have been recorded on Block Island, R.I. (Tuttle and 

others, 1961), and from offshore seismic-refraction 

studies in Cape Cod Bay (Hoskins and Knott, 1961), 

in Nantucket Sound south of Woods Hole, Mass. 

(Ewing and others, 1950), in the Gulf of Maine (Drake 

and others, 1954), and south of Nova Scotia (Officer 

11nd Ewing, 1954). ln these investigations, velocities 

of 9,750 to 13,000 fps were interpreted to represen t 

semiconsolidated or consolidated rock of Cretaceous 

age or rocks of Triassic age similar to the sediments 

found in the Connecticut Valley. These interpretations were based on other seismic measurements from 

areas where these lithologic units crop out or where 

seismic velocities and lithology can be correlated on the 

basis of borehole data. 

If the velocity recorded at traverse 4 for the L3 

seismic layer actually represents a semiconsolidated or 

consolidated layer, the layer is more than 450 feet thick 

and overlies crystalline basement rocks at an altitude on 

the order of 900 feet below sea level. The L3 layer 

occurs in what appears to be an eastward extension of 

a trough found in Cape Cod Bay by Hoskins and Knott 

(1961), the bottom of which is more than 700 feet below 

sea level. This trough is in part filled with material 

having velocities of 10,000 to 12,500 fps, interpreted by 

Hoskins and Knott to be a semiconsolidated deposit of 

Cretaceous age. 

The crystalline basement in this area presumably 

consists of Paleozoic or Precambrian rocks similar to 

those exposed along the shore of Massachusetts Bay 

from Plymouth northward, because the average seismic 

velocities of 14,100 to 23,500 fps are comparable to the 

seismic velocities measured in the outcrop areas of the 

crystalline rocks. Comparison of variation in velocities 

with azimuth suggests that in the Wellfleet area the 

basement is composed of a bedded or foliated rock 

striking eastward, possibly similar to phyllite identified 

in a borehole near Harwich, Mass. (Koteff and Cotton, 

1962). At traverse 8 the average of the rock velocities 

measured in an easterly direction was 23,500 fps, and at 

traverse 9 the average of the rock velocities measured in 

a northerly direction was 14,100 fps. Similar results 

were noted near Harwich, where seismic studies in the 

immediate vicinity of the borehole indicated an average 

velocity of 23,250 fps in an easterly direction, and a 

traverse 1.1 miles southeast of the borehole indicated 

an average velocity of 15,650 fps in a northerly direction 

(Oldale and others, 1962). 

As portrayed on figure 145.2 the basement surface is 

deepest at traverses 3 and 4, where the seismic lines 

were not long enough to detect basement rocks. Instead, minimum depths were computed on the assumption that the critical distance for the basement surface 

was equal to the length of the traverse. On this assumption the basement surface at traverse 3 was computed to be more than 580 feet below sea level. 

At traverse 4, two interpretations for the depth to 

the basement surface are possible, depending upon 

whether the 12,100 fps velocity recorded for the L3 

layer is interpreted as representing crystalline basement 

rocks or a semiconsolidated to consolidated rock overlying the basement. By the latter interpretation and 

on the assumption that the critical distance for the 

basement is equal to the total length of traverse 4, the 

altitude of the basement surface is computed to be 910 

feet below sea level. However, if the 12,100-fps velocity 

actually represents the basement rocks, the surface of 

the basement in this area would be 440 feet below sea 

level and the maximum depth would then be at traverse 3. The authors' preferred interpretation is that 

the basement surface dips steeply north of traverse 5 

and south of traverse 2 to form a valley whose floor is 
OLDALE AND TUTTLE D121 

N 

Q) 

~ Q) 

> 

ro 

~ 

SEA 

LEVEL 

-200' 

-400' 

-600' 

-800' 

()'\ 

iJ 

c 

ro 

C\1 <:t \D 00 

Ill Q) Q) Q) Q) 

~ ~ ~ ~ Q) Q) Q) Q) 

> > > > ro ro ro ro 

~ ~ ~ ~ 

and Tertiary deposits 

Semiconsolidated or 

consolidated sediments 

(Cretace\ous?)- __ f 

~- - I 

"-...."-.... I 

"-.... I "-....'-..../ 

Basement (Paleozoic and 

Precambrian) rocks 

0 5 MILES 

s 

s 

Q) 

~ Q) 

> 

ro 

~ 

-lOOO'_J.__ _____________________ _j 

FIGURE 145.2-Generalized cross section of outer Cape Cod 

from Orleans Beach to Race Paint, showing computed average 

altitude of the basement surface at 8 seismic traverses. 

Dashed lines indicate alternate interpretations in area of 

deepest basement rock. 

more than 900 feet below sea level 1n the vicinity of 

traverse 4 (fig. 145.2). 

FALMOUTH AREA 

At 3 traverses on the Buzzards Bay moraine in 

Falmouth (fig. 145.1), 2 seismic layers (L1 and L2) 

representing unconsolidated deposits of Pleistocene 

and possibly Tertiary and Cretaceous age were recorded over crystalline basement rocks. Velocities 

in the Lt layer ranged from 1,400 to 2,300 fps and are 

thought to represent an unconsolidated layer composed 

in part of unsaturated Pleistocene glaciofluvial sand 

and gravel and in part of unsaturated loose till similar 

to sandy till found in other areas of Massachusetts. 

The L1 layer ranged in thickness from 70 to 80 feet. 

Velocities in the L2 layer ranged fron1 2,900 to 6,600 

fps. The lower velocities in this layer probably represent loose sandy till. The intermediate and higher 

velocities are thought to represent a layer composed for 

the most part of compact till similar to high-velocity 

till in other parts of Massachusetts (Tuttle, 1961). 

On the other hand, it n1ay be a complex layer composed 

of glaciofluvial deposits and till of Pleistocene age, and 

unconsolidated marine and lacustrine deposits of 

Pleistocene, Tertiary, and Cretaceous age. Unconsolidated marine and nonmarine deposits of sand, 

silt, and clay of Pleistocene, Tertiary, and Cretaceous 

age crop out 20 n1iles to the southwest on Marthas 

Vineyard and 7 miles to the south on N onamesett 

Island. Similar deposits of Tertiary and possibly 

Cretaceous age are exposed 31 n1iles to the north at 

Duxbury and Marshfield (\Voodworth and Wigglesworth, 1934; En1erson, 1917). The L2 layer ranges in 

thickness from 170 feet at traverse 13 to 200 feet at 

traverse 11. 

The basement in this area is thought to be Paleozoic 

sedimentary and crystalline rock, possibly the Dedham 

Granodiorite that crops out along the west shore of 

Buzzards Bay. Average velocities measured on the 

basement rocks range from 12,150 to 17,750 fps, and 

seismic measurements on the bedrock in areas mapped 

as Dedham Granodiorite by Emerson in New Bedford, 

Dartmouth, and Westport, Mass. (Emerson, 1917), 

ranged from 11,900 to 16,600 fps. At traverse 13 the 

12,150-fps velocity could represent a semiconsolidated 

or consolidated deposit of Mesozoic age similar to 

that recorded at traverse 4 in Truro, but is thought to 

more likely represent a low-velocity facies of the Dedham Granodiorite similar to those recorded in New 

Bedford, Dartmouth, and Westport. The high percentage of Dedham Granodiorite stones in the drift 

of the Buzzards Bay moraine (Mather and others, 

1942) also suggests that the bedrock in this area is 

Dedham Granodiorite. 

REFERENCES 

Drake, C. L., Worzel, J. L., and Beckmann, W. C., 1954, Geophysical investigations in the emerged and submerged 

Atlantic Coastal Plain, Part IX, Gulf of Maine: Geol. 

Soc. America Bull., v. 65, p. 957-970. 

Emerson, B. K., 1917, Geology of Massachusetts and Rhode 

Island: U.S. Geol. Survey Bull. 597. 

Ewing, W. M., Worzel, J. L., Steenland, N.C., and Press, Frank, 

1950, Geophysical investigations in the emerged and submerged Atlantic Coastal Plain, Part V, Woods Hole, New 

York, and Cape May sections: Geol. Soc. America Bull., 

v. 61, p. 877-892. 

Hoskins, Hartley, and Knott, S. T., 1961, Geophysical investigation of Cape Cod Bay, Massachusetts, using the continuous seismic profiler: Jour. Geology, v. 69, p. 330-340. 

Koteff, Carl, and Cotton, J. E., 1962, Preliminary results of 

recent deep drilling on Cape Cod, Massachusetts: Science, 

v. 137, p. 34. 

Mather, K. F., Goldthwait, R. P., and Thiesmeyer, L. R., 1942, 

Pleistocene geology of western Cape Cod, Massachusetts: 

Geol. Soc. America Bull., v. 53, p. 1127-1174. 

Officer, C. B., and Ewing, M., 1954, Geophysical investigations 

in the emerged and submerged Atlantic Coastal Plain, 

Part VII, Continental shelf, continental slope, and continental rise south of Nova Scotia: Geol. Soc. America Bull., 

v. 6fi, p. 653-670. 

Oldale, R. ~., and Tuttle, C. R., 1962, Preliminary report on the 

seismic investigations in the Orleans, Wellfleet, North 

Truro, and Provincetown quadrangles, Massachusetts: 

U.S. Geol. Survey open-file report. 

Oldale, R. N., Tuttle, C. R., and Currier, L. W. 1962, Preliminary report on the seismic investigations in the Harwich 

and Dennis quadrangles, Massachusetts: U.S. Geol. Survey 

open-file report. 

Tuttle, C. R., 1961, Seismic high-speed till in Massachusetts 

[abs]: Geol. Soc. America Spec. Paper 68, p. 288-289. 

Tuttle, C. R., Allen, W. B., and Hahn, G. W., 1961, A seismic 

record of Mesozoic rocks on Block Island, Rhode Island: 

Art. 240 in U.S. Geol. Survey Prof. Paper 424-C, p. C254-

C256. 
D122 GEOPHYSICS 

Woodworth, J. B., and Wigglesworth, Edward, 1934, Geography 

and geology of the region including Cape Cod, the Elizabeth 

Islands, Nantucket, Mart has Vineyard, No Mans Land 

and Block Island: Harvard Coll. Mus. Comp. Zoology 

Mem., v. 52, 322 p. 

Zeigler, J. M., Hoffmeister, W. S., Geise, Graham, and Tasha, 

Herman, 1960, A discovery of Eocene sediments in the subsurface of Cape Cod, Massachusetts: Science, v. 132, p. 

1397-1398. 
Article 146 

GEOLOGIC SETTING OF THE SPAR CITY DISTRICT, 

SAN JUAN MOUNTAINS, COLORADO 

By THOMAS A. STEVEN, Denver, Colo. 

Work done in cooperation with the Colorado Metal Mining Fund Board 

Abstract.-The district is along the south margin of the Creede 

caldera, near the intersection of a narrow graben cutting the 

core of the caldera and a reactivated fault along the margin of 

the caldera. The exposed veins appear to ha\ e been deposited 

in a near-surface environment and may represent the upper parts 

of the original vertical range of ore deposition. 

The Spar City district, a srnall mineralized area along 

the south flank of the Creede caldera in the central 

San Juan Mountains, southwest Colorado (fig. 146.1), 

has been prospected sporadically since the early 1900's. 

Several n1ine workings were driven in the early days 

to explore some of the exposed veins in the district, and 

vein fragn1ents containing galena, sphalerite, barite, 

manganese oxides, and jaspery to amethystine quartz 

are strewn over several of the old dumps. Systematic 

exploration, however, has been discouraged by thick 

soil and dense forest cover, and by widespread landslides and glacial drift. Recent regional geologic studies 

in and adjacent to the Creede caldera have outlined 

the geologic frmnework of the Spar City district, and 

although many specific details remain obscure, the 

additional knowledge should help guide future prospecting and exploration programs. 

The mineralized area in the Spar City district is 

localized near the intersection of two differently trending struetures that were active during voleanie aetivity, 

and the known veins appear to be along rninor faults 

assoeiated with this interseetion. Mineralization took 

place late in the loeal sequence of volcanie and struetural events, and was assoeiated with or later than the 

last main period of faulting. Exposed veins were 

deposited in a near-surfaee environment. 

The Creede caldera (Steven and Ratte, 1960) is a 

subcireular collapse strueture 10 to 12 miles in diarneter 

whose margin is clearly marked in the present topography for nearly 300° of are by the valley of the Rio 

Grande and its tributaries (fig. 146.1). This ealdera is 

the youngest of at least four separate overlapping 

eauldron struetures that together eaused an area at 

least 25 miles long and 5 to 15 miles wide in the eentral 

San Juan Mountains to subside now and again in 

response to volmninous ash-flow eruptions during 

rniddle or late Tertiary tirne (Steven and Ratte, 1963, 

and Art. 132). The last period of subsidenee of the 

Creede ealdera aeemnpanied eruption of the Snowshoe 

Mountain Quartz Latite, a erystal-rich ash-flow tuff, 

largely densely welded, that eonsists of 40 to 60 pereent phenoerysts in a drab gray to brownish matrix. 

The phenoerysts consist largely of intermediate plagioclase, with lesser biotite, clinopyroxene, hornblende, 

sanidine, and quartz. The Snowshoe Mountain Quartz 

Latite aeeumulated to a thiekness of more than 6,000 

feet within the ealdera, but has not been reeognized 

outside. Talus and landslide breceias fron1 the walls 

of the ealdera intertongue marginally with the Snowshoe Mountain and indieate that subsidenee and 

ttecumulation were eoneurrent over an extended period 

of time. 

Final subsidenee of the Creede ealdera left a flatfloored basin at or below the level of the present Rio 

Grande, and talus and roekfall breeeias spread widely 

over the floor. Northwest-trending tangential grabens, 

now followed by the Rio Grande both upstrearn and 

downstream frorn the ealdera, fonned late in the period 

of subsidenee, and son1e faults in the reeurrently active 

Creede graben extending north-northwest frorn the 

ART. 146 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D123-Dl27. 1964. 

716-626' 0-64-9 D123 
D124 ECONOMIC GEOLOGY 

COLORADO 

Area of 

..--report 

0 4 8 MILES 

FIGuRE 146.1-Geologic sketch map of the Creede caldera aud adjacent areas. Snowshoe Mountaiu Quartz Latite (Ts) accumulated in core of caldera during subsidence. Sedimentary 

rocks of the Creede Formation (Tc) filled a structural moat around the domed core of the 

caldera, and viscous lava flows and breccias of Fisher Quartz Latite (Tf) were erupted locally 

around the margin of the caldera. Undifferentiated volcanic rocks that accumulated outsidP 

the caldera before and during subsidence are shown as blank. Contact lines indicate the 

general limit of distribution of the formations. Heavy li11es are generalized faults, dashed when~ poorly known or hypothetical. 

northern margin of the caldera may have been active at 

the same time. 

The core of the Creede caldera was resurgently 

domed (Smith and Bailey, 1962) following final subsidence, and some parts near the center v.rere uplifted 

more than 4,000 feet above a residual topographic moat 

left all around the 1nargin. A eomplex keystone graben 

formed aeross the eenter of the core during doming; 

displace1nen t in this graben was 1ninor near the northern 

and southern margins of the caldera, but some blocks 

near the eenter are nearly 4,000 feet below equivalent 

rocks in the adjacent uplifted blocks. 

Volcanie aetivity broke out around the margin of the 

caldera following doming, and viseous flows and domes 

of Fisher Quartz Lntite formed several loea1 neeumulations, particularly along the south margin of the caldera 

(fig. 146.1). Concurrently, stream and lake sediments, 

voleanie ash, and travertine frmn mineral springs were 

deposited elsewhere around the caldera to form the 

Creede Formation. 
STEVEN D125 

The last major period of faulting known around the 

Creede caldera followed accumulation of the Fisher 

Quartz Latite and Creede Formation. Many of the 

faults that forrned earlier during the period of recurrent 

volcanic eruptions and cauldron subsidence were reactivated at this time. Faults active at this time are 

economically significant, as the important ore deposits 

in the Creede district north of the caldera formed 

concurrently with or shortly following movement, and 

the active or recently active faults were favored sites 

for mineralization ('Steven and Ratte, 1960). The 

mineral deposits in the Spar City district were formed 

at about the san1e tin1e. 

Erosion of the Creede Formation has reexposed the 

margin of the Creede caldera. Although the adjacent 

slopes have been considerably dissected, the original 

form of the domed caldera core, as well as other constructional landforn1s in adjacent areas can still be 

recognized in many places. 

In detail, the Spar City district is localized near the 

intersection of a fault marking the southern extension 

of the core graben of the Creede caldera and a reactivated fault linking the northwest-trending tangential 

graben with the caldera margin (figs. 146.1 and 146.2). 

The exposed faults near the Bird Creek rnine and Emma 

mine (fig. 146.2) all appear to be minor fractures subsidiary to larger faults that seem required under the 

adjacent landslide and moraine cover. At its southern 

end, the core graben changes southward from a wide 

zone of jumbled fault blocks between persistent marginal faults to a single fracture that can be followed 

closely north of Lime Creek, although it has not been 

seen in outcrop farther south. The position of the 

fracture shown in figure 146.2, adjacent to the mineralized area of the Spar City district, is hypothetical and 

depends strictly on projection frorn the well-defined 

trends farther north. 

The arcuate but generally east-trending fault 

postulated to separate the rnineralized area of the 

Spar City district from the top of Fisher Mountain to 

the south (fig. 146.2) also has not been seen in outcrop. 

A fault south of the Ernrna mine seems certainly 

required, however, by the relations of the distinctive 

coarsely porphyritic quartz latite flow that caps 

Fisher Mountain. The base of this flow is clearly 

exposed along the west side of the spur ridge extending 

north fron1 the sun1mit of Fisher Mountain. The 

base ranges generally frorn an elevation of 11,250 

feet near the north end of the spur, to 11,400 feet near 

the south end. The same capping flow comprises 

all the island of outcrop containing the Emma n1ine 

and the Denver Tunnel a short distance northwest 

across the postulated fault; the flow extends as low as 

10,750 feet nea.r the Denver Tunnel, but the base is 

not exposed. 

No bedrock is exposed where the hypothesized easttrending fault crosses the ridge extending northwest 

from the summit of Fisher Mountain, and no evidence 

either for or against the fault was seen in the soil or 

float that covers the ridge in this vicinity. Unbroken 

exposures of the capping flow, short distances north 

and south of the projected trend, limit the position 

of the fault to a span about 1,000 feet wide. 

The east-trending fault required between the Emma 

mine area and the top of Fisher Mountain projects 

northwesterly toward the southwest margin of the 

tangential graben that extends northwestward from 

the Creede caldera (fig. 146.1). Overlap relations at 

the southeastern end of the graben clearly indicate 

that the graben formed before the Creede Formation 

and Fisher Quartz Latite were deposited, and thus the 

arcuate east-trending fault in the Spar City district 

appears to represent post-Fisher reactivation of older 

trends related to caldera subsidence. 

The capping quartz latite flow on Fisher Mountain 

appears to have been the youngest lava flow deposited 

in this area. To the west, rnarginal breccias along the 

flank of this flow intertongue with sedin1ents of the 

Creede Formation, and to the north a thin wedge of 

Creede Formation appears to separate the flow from 

the underlying Snowshoe Mountain Quartz Latite 

near the Bird Creek rnine (fig. 146.2). All these 

younger rocks are cut by mineralized minor faults, 

indicating that late faulting and mineralization here 

as well as in the Creede district north of the caldera 

postdated accmnulation of the Creede and Fisher. 

The exposed veins rnust have been deposited very 

near the surface, as the youngest Tertiary rocks 

deposited in the area form the host rocks. The 

common occurrence of barite, manganese oxides, and 

dense jaspery quartz in the gangues further suggests 

a near-surface environn1ent of deposition. Deductively 

it would seem more probable that the present exposures 

represent the upper rather than the lower parts of the 

original vertical range of ore deposition, and that 

somewhat deeper levels rnay be nwre favorable for the 

discovery of ore deposits. 
D126 

107°00' 

37°45' 

0 

CONTOUR INTERVAL 400 FEET 

Contact 

Dashed where a.pproximat.ely 

located; short dashed where 

gradational or indefinite 

ECONOMIC GEOLOGY 

EXPLANATION 

....!--------? 

Fault 

Dashed where approximately 

located; dotted where concealed; queried where hypothetical. Bar and ball on 

downt.hrown side 

"-<0 

Strike and dip of compaction 

foliation or bedding 

Qm' 

FIGURE 146.2-Geologic map of the Spar City district, Colorado. Tertiary rocks: Ts, Snowshoe Mountain Quartz 

Latite (in core of caldera); Tf, Fisher Quartz Latite; Tc, Creede Formation (in structural moat). Quaternary 

rocks: Qm, moraine; Qls, landslide debris; Qal, alluvium. Base from U.S. Geological Survey topographic quadrangle: Rpar Citv, HH>7. 
STEVEN D127 

REFERENCES 

Smith, R. L., and Bailey, R. A., 1962, Resurgent cauldronstheir relation to granitic ring complexes and large volume 

rhyolite ash-flow fields [abs.], in International symposium 

on volcanology, Japan: Internat. Assoc. Volcanology, 

1962, p. 67-68. 

Steven, T. A., and Ratte, J. C., 1960, Relation of mineralization 

to caldera subsidence in the Creede district, San Juan 

Mountains, Colorado: Art. 8 in U.S. Geol. Survey Prof. 

Paper 400- B, p. B14-B17. 

--- 1963, Resurgent cauldrons in the Creede area, San 

Juan Mountains, Colorado [abs.J: Am. Geophys. Union 

44th Ann. Mtg., April, 1963, Program, p. 112-113. 
Artic'le 147 

THORIUM AND URANIUM IN MONAZITE 

FROM SPOKANE COUNTY, WASHINGTON 

By JOHN W. HOSTERMAN, W. C. OVERSTREET; and j. j. WARR, JR., Beltsville, Md.; and Washington, D.C. 

Abstract.-Monazite occurs in residual clay derived from 

granodiorite and related rocks (saprolite) and sedimentary clay 

deposits of the Latah Formation. In three samples of monazite 

separates, thorium oxide (Th02) averages 3.6 percent and 

uranium oxide (U30 8) averages 0.37 percent. The tenor of the 

monazite is not high enough to be considered commercial. 

OCCURRENCE 

Monazite, an anhydrous phosphate of the cerium 

earths containing variable amounts of thorimn, has 

been known for a number of years to occur in saprolite 

of crystalline rocks in Spokane County (fig. 147.1) 

(Goodspeed and Weyn1outh, 1928, p. 687-695), but 

determinations of the amount of thorium and uranium 

in the monazite have not been reported heretofore. 

In this article, analyses are given of Inonazite collected 

by the senior author in 1962 during investigations of 

residual and sedimentary clay deposits in Spokane 

County. Analyses of two san1ples of Inonazite from 

residual clay deposits and one sa1nple from sedimentary 

clay show that the amount of thorium is below the 

normal commercial specifications for monazite, but 

they add to inforn1ation on the composition and resources of n1onazite in the Pacific Northwest. 

Monazite-bearing residual clay deposits occur on 

quartzose gneiss and granodiorite exposed in the FreeInan clay pit, and on silli1nanite gneiss reached in an 

auger hole located on the point of a hill 0. 95 mile south 

of Saltese Flats. The deposits consist chiefly of kaolinite and halloysite formed by the weathering of almninasilicate minerals, variable amounts of unaltered quartz, 

and minor quantities of resistate accessory minerals 

(Hostern1an, 1960, p. 289-291). The residual deposits 

are soft cmnparecl to the underlying crystalline rocks. 

They preserve the textures and structures of the 

original gneiss and granodiorite even though n1uch of 

the rock has been replaced by n1inerals forn1ed during 

weathering. The term "saprolite" has been widely 

used by geologists and soil scientists for such decomposed rocks since it was introduced by Beeker (1895, 

p. 289-290), and it will be used here for these materials. 

The conclusion that the residual clay deposits are 

saprolites formed by weathering is supported by the 

wide distribution of clay deposits in eastern Washington 

and northern Idaho (Hosterman and others, 1960, fig. 

1), and the observations that extensive kaolinitic and 

halloysitic saprolites are now known to develop during 

weathering in n1any parts of the world (Campbell, 

1917, p. 67; Fox, 1923, p. 4; 1936, p. 419; Harrassowitz, 

1926, p. 320-382; Gordon and others, 1958, p. 137-146). 

5 MILES 

FIGURE.147.1- Index map showing location of monazite deposits, 

Spokane County, Wash. 

ART. 147 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D128-D130. 1964. 

D128 
HOSTERMAN, OVERSTREET, AND WARR D129 

Three n1onazite-bearing concentrates were panned 

from saprolite of the quartzose gneiss, granodiorite, 

and sillimanite gneiss, but only the concentrates from 

granodiorite saprolite (sample 160816, accompanying 

table) and sillimanite gneiss saprolite (sample 160817) 

contained a sufficient percentage of monazite for analysis. In these two samples monazite made up about 

20 percent of the concentrate. Less than 5 percent 

of the concentrate frorn the quartzose gneiss saprolite 

was n1onazite. Monazite was estimated to rnake up 

from less than 0.001 percent to about 0.003 percent of 

the original rock from which the saprolite was derived. 

Thorium and uranium in monazite from Spokane County, Wash. 

[Analyses by J. J. Warr, Jr.] 

Laboratory Percent 

sample Source of Location 

No. monazite 

Th02 UaOs 

-- 160816 ________ Granodioritic Clay pit at Freeman; sec. 1, T. 23 2. 74 0.65 saprolite. N., R. 44 E. 160817-------- Sillimanite Auger hole on point of hill 0.95 4. 06 . 20 gneiss mile south of Saltese Flats; sec. saprolite. 32, 'I'. 25 N., R. 44 E. 160818 ________ Sedimentary Sommers clay pit; sec. 35, T. 25 N., 3. 92 .26 clay. R. 44 E. 

The mineralogic composition of the n1onazite-bearing 

concentrates varies with the type of rock from which 

the saprolite developed. Concentrates from saprolite 

of quartzose gneiss in the clay pit at Freeman were 

observed by Goodspeed and Weymouth (1928, p. 687-

692) and the senior author to contain monazite, zircon, 

magnetite, ilmenite, cassiterite, rutile, tourmaline, and 

staurolite relict from the original rock. Concentrates 

from this saprolite also have accessory anatase, which 

is probably a secondary mineral formed by weathering. 

Concentrates from saprolite of granodiorite exposed at 

the same locality contain monazite (sample 160816), 

zircon, magnetite, ilmenite, cassiterite, rutile, tourmaline 

topaz, and lepidolite, but lack staurolite. They also 

have anatase of probable secondary origin. A concentrate panned from saprolite of sillimanite gneiss 

sampled with the aid of an auger at a locality west of 

the Saltese Flats consisted of monazite (sample 160817), 

zircon, ilmenite, spessartite, tourmaline, sillimanite, and 

actinolite. 

The resistate heavy minerals recovered from the 

saprolites are not abraded. The rninerals occur mostly 

as discrete grains, sorne of which are euhedral, and as 

inclusions in quartz, or as intergrowths with quartz 

or other heavy n1inerals. 1-Iost monazite grains are 

subhedral to anhedral, and they are up to about 0.02 

inch in rnaximum dimension. About 10 percent of 

the n10nazite grains from granodiorite saprolite are 

euhedral tabular crystals, but only a percent or two 

of the grains frOin the saprolite of gneiss are euhedral. 

The monazite is uniformly dark yellow with no perceptible difference in color relatable to kind of source 

rock. 

A nwnazite-bearing clayey sand bed occurs in a sedimentary clay deposit in the Tertiary age Latah Formation at the Sommers clay pit, about 67§ miles north of 

Freeman and 3% rniles west of Saltese Flats. The 

sedimentary material is thought to have been derived 

from local sources inasmuch as the heavy minerals show 

few if any effects of transportation. Weathered gneiss 

seems to be the rnost likely source because the sedirnentary rock contains detrital heavy minerals of the 

same species that occur as accessory rninerals in the 

gneisses and because the detrital n1onazite in the clay 

has uranium and thorium contacts sirnilar to the 

monazite in the sillimanite gneiss saprolite. Detrital 

monazite (sarnple 160818) was estimated to n1ake up 

approximately 0.01 percent by weight of the total 

sample from the Sommers clay pit. This may not be 

appreciably greater than the amount of monazite in 

saprolite of the gneisses if there is a large loss of heavy 

minerals in panning clay (Theobald, 1957, p. 16-17). 

COMPOSITION OF THE MONAZITE 

Monazite for analysis was prepared from the panned 

concentrates by standard procedures of heavy liquids 

and n1agnetic separation, and the final n10nazite separate from each sarnple was handpicked using a rniniature vacuurn cleaner with a small orifice under a binocular microscope. J. J. Warr, Jr., determined the arnount 

of thorium in the rnonazite (see table) by colorimetric 

methods slightly nwdified frOin the procedure described 

by Grimaldi and others (1957), and the an1ount of 

uranium was determined by the visual fluorirnetric 

methods discussed by Grimaldi and Levine (1954). 

The analyzed san1ples of monazite contain an average 

of 3.6 percent thorium oxide (Th02 ). This is sirnilar to 

the average of 3.3 percent Th02 observed for a large 

number of samples of n1onazite from placers in northern 

and central Idaho (Schrader, 1910, p. 188), but less 

than the average of 4 percent Th02 shown by 34 published analyses of detrital rnonazite in the area of the 

Idaho batholith (Staley, 1952, p. 306; Kauffnum and 

Baber, 1956, p. 6). The an1ount of uraniurn in the 

three samples is sirnilar to that found in monazite frorn 

central Idaho (Kauffman and Baber, 1956, p. 6). 

ECONOMIC ASPECTS 

The sarnples of n1onazite were collected primarily as 

part of an investigation of clays. They are neither 

large enough nor sufficiently nmnerous to furnish a 

basis for an estimate of the amount of monazite in the 

rocks. However, in the few sarnp~es taken, monazite 

was appreciably less than 0.01 percent of the rock, 

showing that at the sampled loealities the anwunt of 
D130 ECONOMIC GEOLOGY 

n10nazite in gneiss, granite, and day is unacceptably 

low for mining. Moreover, the n10st thorium-rich 

n1onazite sample contained 4.06 percent Th02 , an 

amount falling near the lower end of the range shown by 

monazite in sillin1anite gneiss and associated granite 

elsewhere (Overstreet, 1960, table 27.1), and considerably less than the present commercially accepted minin1un1 grade of 6 percent. On the basis of results of 

analyses of the three samples reported in this article, it 

is not to be expected that monazite containing significantly higher tenor of Th02 will prove to be of widespread occurrence in this part of Washington. 

REFERENCES 

Becker, G. F., 1895, Reconnaissance of the gold fields of the 

southern Appalachians: U.S. Geol. Survey 16th Ann. Rept., 

pt. 3, p. 251-319. 

Campbell, J. M., 1917, Laterite: its origin, structure, and 

minerals: Mining Mag. [London], v. 17, no. 2, p. 67-77: 

no. 3, p. 12Q-128; no. 4, p. 171-179; no. 5, p. 220-229. 

Fox, C. S., 1923, The bauxite and aluminous laterite occurrences 

of India: India Geol. Survey Mem., v. 49, pt. 1, p. 1-287. 

--~ 1936, Buchanan's laterite of Malabar and Kanara: India 

Geol. Survey Recs., v. 69, pt. 4, p. 389-422. 

Goodspeed, G. E., and Weymouth, A. A., 1928, Mineral constituents and origin of a certain kaolin deposit near Spokane, 

Washington: Am. Ceramic Soc. Jour., v. 11, no. 9, 

p. 687-695. 

Gordon, Mackenzie, Jr., Tracey, J. I., Jr., and Ellis, M. W., 1958, 

Geology of the Arkansas bauxite region: U.S. Geol. Survey 

Prof. Paper 299, p. 1-268. 

Grimaldi, F. S., Jenkins, L., and Fletcher, M. H., 1957, Selective 

precipitation of thorium iodate from a tartaric acid-hydrogen 

peroxide medium: Anal. Chemistry, v. 29, p. 848-851. 

Grimaldi, F. S., and Levine, Harry, 1954, The visual fluorimetric 

determination of uranium in low-grade ores, pt. 6 in 

Grimaldi, F. S., May, Irving, Fletcher, M. H., and Titcomb, 

Jane, 1954, Collected papers on methods of analysis for 

uranium and thorium: U.S. Geol. Survey Bull. 1006, 

p. 43-48. 

Harrassowitz, Hermann, 1926, Laterit Material und Versuch 

erdgeschichtlicher Auswertung: Fortschr. Geol. Palaeont., 

v. 4, no. 14, p. 253-566. 

Hosterman, J. W., 1960, Clay deposits in parts of Washington 

and Idaho, in Clays and clay minerals: Proc. of the 7th 

N atl. Conf. on Clays and Clay Minerals, p. 285-292. 

Hosterman, J. W., Scheid, V. E., Allen, V. T., and Sohn, I. G., 

1960, Investigations of sohle clay deposits in Washington 

and Idaho: U.S. Geol. Survey Bull. 1091, p. 1-147. 

Kauffman, A. J., Jr., and Baber, K. D., 1956, Potential heavymineral-bearing alluvial deposits in the Pacific Northwest: 

U.S. Bur. Mines Inf. Circ. 7767, 36 p. 

Overstreet, W. C., 1960, Metamorphic grade and the abundance 

of Th02 in monazite: Art. 27 in U.S. Geol. Survey Prof. 

Paper 400-B, p. B55-B57. 

Schrader, F. C., 1910, An occurrence of monazite in northe!'n 

Idaho, in Hayes, C. W., and Lingren, Waldemar, 1910, 

Contributions to economic geology, 1909: U.S. Geol. 

Survey Bull. 430, pt. 1, p. 184-191. 

Staley, W. W., 1952, Monazite in Idaho: The Compass, v. 29, 

no. 4, p. 303-312. 

Theobald, P. K., Jr., 1957, The gold pan as a quantitative 

geologic tool: U.S. Geol. Survey Bull. 1071-A, p. 1-54. 
Article 148 

RICH OIL SHALE FROM NORTHERN ALASKA 

By IRVIN L. TAIL LEUR, Menlo Park, Calif. 

Abstract.-Samples of oil shale of Jurassic(?) age from the 

foothills along the north edge of the Brooks Range assay 26-146 

gallons of oil per ton of rock. The oil yield is greater than that 

of the Green River Formation, but owing to insufficient information the economic potential of the oil shale cannot be determined. 

Samples of an organic shale of Jurassic(?) age, which 

crops out in the foothills along the north edge of the 

Brooks Range (fig. 148.1), assay 26-146 gallons of oil 

per ton of rock, several times nwre than assays of the 

minable beds of oil shale in the Green River Formation 

in the Rocky Mountain region. This Alaskan oil shale 

may be a significant resource, but more stratigraphic 

and structural infonnation will be required for its 

assessment. 

The oil shale seems to have been utilized for fuel in 

prehistoric tirnes. Abnormal distribution of float, especially near old trailways and encan1prnents, indicates 

that the Eskinws who lived in the interior before 1900 

collected and transported the rock. It was probably 

carried for fuel. This is suggested by their identificaof the material as wood in the times before the arrival 

of the white n1an (Stoney, 1900, p. 69). 

Material inferred to have been oil shale was observed 

on several early expeditions to northern Alaska, and 

oil shale was specifically identified along later geologic 

traverses. Dr. John Sin1pson, surgeon aboard the 

H.M.S. Plover wintering at Point Barrow during 1852 

to 1854, noted that "there is strewed along the beach 

a quantity of coal, ... bituminous enough to make 

an excellent fire for cooking. It is of the sort called 

candle-coal, and some of the pieces are sound enough 

to be carved by the natives into lip ornaments" 

(Collinson, 1875, p. 125). On his overland trek in 

1886 Lt. Howard found a substance on the rniddle 

Etivluk River "called wood by the natives; it was 

hard, brittle, light brown in color, very light in weight 

and burned readily, giving out quantities of gas" 

(Stoney, 1900, p. 69). Specimens collected from the 

mouth of the Kukpuk River in 1904 that Collier (1906, 

p. 45) described as cannel coal were n1ore likely to have 

been fragments of oil shale, for such fragn1ents have 

been found on gravel bars upstrean1 by the present 

writer. Sn1ith (Smith and Mertie, 1930, p. 282-286) 

collected and identified oil shale fron1 bedrock along 

the Kivalina River and fron1 float along the Etivluk 

River in the 1920's. The material was cmnposed 

ehiefly of megaspores. He speculated that the rock 

occurred at the base of the geosynclinal sedirnen tary 

deposits of Mesozoic age in northern ~laska an? might 

be the source of the petrolemn shows rn the regwn. 

Geologic n1apping of Naval Petrolemn Reserve No. 

4 (1 948-53) indicated that oil shale sin1ilar ~o that 

frorn the Green River Formation occurs rn the 

Tiglukpuk Forrnation (Jurassic) (W. W. Patton, Jr., 

written communication, 1959) and in rock units that 

appear to be correlative with the Tiglukpuk. Hig~ly 

organic shales also oecur in the Shubhk Forrn~tr?n 

(Triassic) and in the Lisburne Group locally (Mrssrs0 100 MILES 

FIGURE 148.1.-Index map of northern Alaska. 

ART. 148 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl31-D133. 1964. 

D131 
D132 ECONOMIC GEOLOGY 

sippian) but lack the massive woody aspect of the 

.Jurassic(?) shale (see accompanying table). The oil 

shale is known to crop out sporadically from the Ipewik 

River on the west to the Anaktuvuk River on the east, 

a distance of more than 300 miles. Owing to its low 

density and toughness, the shale is distributed widely 

as float and as outsized clasts in coarse-grained younger 

rocks. 

Exposures of oil-shale strata are sparse and incomplete, and most show strong defonnation. Thickness 

and other stratigraphic details, therefore, are difficult 

to determine. Oil shale apparently is present in at 

least two distinct stratigraphic successions. One consists of oil shale and chert near the base of the Tigl ukpuk 

Formation, which overlies the Shublik and Siksikpuk 

(Permian) Formations and the Lisburne Group; the 

Analyses and descriptions of organic shale samples 

[Specific gravity determined by author; Fischer analyses by J. Budinsky] 

Stratigraphie unit Laboratory No. Location I (coordinates) and (field No.) 

-------------------·--------------

1. Jurassic(?) 160 127 Mid part of Kiligwa 

(51ATr220) River 

(68°41'50" N., 

158°28'00" W.) 

2. Jurassic('?) 160 134 East of mid part of 

(50AKt261) Kuna River 

(68°40'05" N., 

157°32'15" W.) 

3. Jurassic(?) 160 129 Mid part of Kiligwa 

(51AKt67) River 

(68 °39' 45" N ., 158°28'10" W.) 

4. Jurassic(?) 160 128 Mid part of Kiligwa 

I 

(51ATr228) River 

(68°42'25" N., 

158°27'45" W.) 

5. Tiglukpuk Formation lGO 133 West of mid part of 

(50AKt237) Ipnavik River 

(68°41'30" N., 

157 o 17'40" W.) 

6. Tiglukpuk Formation 160 132 West of mid part of 

(50ATr60) Etivluk River 

(68°37'40" N., 

156 o 43'00" W.) 

7. Shublik Formation 160 130 Mid part of Kiligwa 

(51ATr248) River 

(68°44'50" N., 

158 °24'50" W.) 

8. Lisburne Group 160 131 East of mid part of 

(50AKt106) Ipnavik River 

(68°40'05" N., 

156 o 57' 40" W.) 

1. Cutbank. Brownish-black woody shale; tough, compact, 

incipient very thin plates with conchoidal, resinous transversP fracture: wca thcrs pale brown; thinly interlwdded 

with varicolored cht'rt; within 70 fPl't of unconformable 

basal contact of Okpikruak Formation on south flank of 

anticline. 

2. Float along small str0am. Dark-ydlowish-brown woody 

shale; tough, compact; resinous, irregular fracture; crcnulated varicolorc•d chert and Okpikruak Formation nearby. 

3. Cutbank. Grayish-black papery to woody sbak; platy, 

Wl'akly exfoliated; 12 feet thick; overlies moderately 

dipping, faulted, varicolored chert. Oil shale and oilstained sandstone exposed in adjacent cutbanks. 

4. Cutbank. Black organic shale; compact ·with incipient 

parting; dull with very fine resinous layers: grayishyellow bloom; 20-foot thickness exposed, subordinate chert; 

I 

Fischer analyses 

------------------------------ Specific 

gravity Oil (gal/ \Vater Oil Water Gas, plus Ash at ton) (gal/ton) (percent) (percent) loss 900°C (percent) (percent) 

----· ------------------------------

1. 22 146 6. 3 53. 7 2. 6 8. 9 30. 0 

1. 27 144 17. 7 

I 

60. 6 7. 4 13. 7 23. 1 

I 

I __ I 

----

1. 20 52. 6 25. 2 19. 7 10. 7 ! 18. 7 12. 7 

I 

1. 51 40. 91 12. 9 17. 1 5. 3 8. 0 26.0 

1. 61 48. 8 14. 9 20. 3 6. 3 6. 1 48. 1 

1. 86 26. 6 9. 8 11. 1 4. 1 I 

6. 0 57. 6 

1. 90 24. 7 8. 8 8. 2 3. 7 4. 1 59. 2 

2. 4 6. 7 3. 4 2. 8 1.4 1.8 58. 3 

I I 

associated with strongly ddornwd varicolored chert, shale, 

sandstone, and very finely stratifil'd limestone. 

.5. Rubble bank. Grayish-black organic shale; compact, very 

fin0, platy partings, dnll luster; associated ·with chert. 

Apparently crPimlakd with underlying Shublik Formation 

and ovt•rlying Fortress Mountain Formation. Float of 

asphaltum also in rubble. 

6. Outcrop. Dark brownish-gray papPry shale; calcareous; 

bdemllitl's; weathers light gray and pale brown; 15 feet 

of 2-:~ mch layPrs, subordinate thin dark chert beds; 

overlies cn~nulated Shublik Formation. 

7. Cutbank. Brownish-black papNy shale; calcareous; abundant 

Halobia (pectenoid mollusk) imprints; 2-4-inch beds with 

inte-rbeds of dark, very fine limestoue and black chert. 

8. Rubble. Grayish-brownish-black, platy shale; calcareous; 

associatPd with thin platy, brittle, very dark gray limestone. 

1 From 1:63,360 manuscript maps for Howard Pass quadrangle, Alaskan Topographic Series. 
TAILLEUR D133 

other consists of oil shale and chert lying between 

ill-defined stratigra.phir units of Permian and Jurassic 

age and the Okpikruak Formation (lo\\·crrnosL Cretaceous) .1 Oil-stained eandstone crops out near exposui'C~s of oil shale in the second sueeession on the 

Kiligwa River. 

FJGuRE 148.2.- Location of oil-shale samplPs (x ), otlHor exposures 

of oil shale (o) , a nd outcrops of oil-stain!'d sandstone (s) on tlw middle Ki!ig"·a Ri ver (from n·ctified twinplex photo GS TAL 18- 104L) . 

The oil shale has not been given special attention 

during current mapping because of the structural 

complexity and an apparent lack of appreciablE> 

thickness. However, sa1nples of organic shale from 

the Nuka-Etivluk Rivers region were ~tna lyz ed recently 

ns p~-trt of a general compihttion of oil-shale d<ttn (D. 

Duncan and V. Swanson, oral eo nun unication ,-1 962). 

Assayed yields of 26- 146 gallons/ton of the Jurassic(?) 

S!tmples are high in comparison with yields of the 

Green River Formation, in which reserves arc computed in terms of 15 and 25 p:allons/ton yields, with a 

maximum yield of 60- 90 g-allons/Lon (Cashion , 1957, 

p. 135). 

Stratigraphic descriptions of the samples, locaLion 

of outcrops, and Fischer analyses ~tre given in the 

accompanying table. 

Additional study of the oil shalf' will be required to 

assess its potential. T n t he author's experience, slutle 

along the Kiligwa River offers the most promise. 

Known exposures of oil shale along th is river are shown 

on figure 148.2. 

REFERENCES 

Cashion, W. B., 1957, Stratil-\raphic relat ions and oil shale of 

the Green River Formation in the eastern Uinta Basin, 

in Guid ebook to t luo gnology of the Uinta Basin: Intermountain Assoc. Petroleum Geologists, p. 131-135. 

Collier, A. J., 1906, Geology and coal resources of tlw Cape 

Lisburne region, Alaska : U.S. Geol. Survey Bull. 27S, 54 p . 

Collinson, R ., 1S75, Notes on the state of t he ice, and on the 

indications of open ·water from Behring Strait to Bellot 

Strait, along the coa t~ of Arctic America and Siberia, 

including the accounts of Anjou and Wrangell, in Royal 

Geographical Society, A selection of papers on Arctic 

geography and ethnology: London , .John Murray, p. 105-

162. 

Smith, P . S., and Mertie, J. 13., .Jr. , 1D30, Geology and mineral 

resources of northwest ern Al a~ka : U.S. Geol. Survey Bull. 

tl15, 351 p. 

Stoney, G. Ivi., 1900, Naval explorations in Alaska: Annapolis, 

Md., U.S. ="aval Inst., 105 p. 

1 R. A. Scott (written communirat,ion, ) palynolog:icall y examinrd seven oiiShfde samples and found that tlwy t•ontailwd only planktonic for ms ehir fl ' dinofl agrllates and hystrichosphucrifls) and pn•sumai>Iy re\\·orked pollen of Permhtn or 

Early Triassic age. Il c inferred that tlw samph'S Wt'rc of post-'l'rinssif' age antl 

possibly "·ere deposited far enough from shore to c.xcludt• contemporaneous pollen. 
Article 149 

DISSIMILARITY BETWEEN SPATIAL AND VELOCITY-WEIGHTED 

SEDIMENT CONCENTRATIONS 

Rv H. P. GUY and D. B. SIMONS, Fort Collins, Colo. 

Abstract.-Theoretical and measured differences between 

spatial and velocity-weighted concentrations show (1) that the 

spatial concentration is normally the grPater and increases as 

the velocity and concentration gradients incmase, (2) that 

velocity-weighted concentration must be used to compute sediment discharge, and (3) that spatial concentration must be used 

to compute the pressure or specific weight on the bed. 

Sediment-concentration data in natural streams are 

used mostly to determine the amount of solids, either 

by weight or by volume, moving with streamflow. 

Such concentration data must be discharge weighted; 

that is, they must be a mean of velocity-weighted 

concentrations at many points in the stream cross 

section. The depth-integrating suspended samplers 

give a velocity-weighted concentration when a uniform 

vertical transit rate is used at evenly spaced verticals 

in the cross section. A discharge-weighted concentration is also obtained by traversing the nappe of flow 

from a flume at a uniform transit rate with an interception device having a uniform width of slot. 

The sediment concentration computed from a spatialcollection procedure is defined as the relative quantity 

of sediment contained in an immobilized prism of 

water-sediment mixture over a specific area of the 

channel. The chief distinction between velocityweighted and spatial concentrations is that one is 

based on sediment and water discharged through a 

cross section and the other on sediment and water in 

motion above an area of streambed at a particular 

instant. The difference between the two concentration 

measures (velocity-weighted and spatial) has been 

understood, to some degree, by a few sedimentologists 

for several years. Much confusion still exists, however, 

and the quantitative differences between the measures 

have seldom been determined even approximately. The 

purposes of this article are (1) to explain the differences 

between, and some uses of, these concentrations and 

(2) to show differences between the two concentrations 

as determined experimentally by use of plastic pellets 

transported by water in a small flume. 

THEORETICAL DIFFERENCES 

Differences between the velocity-weighted and spatial 

concentrations can be evaluated theoretically by consideration of the four equations that follow. 

Equation 1 is the Prandtl-von Karman relation used 

by Einstein (1950) 

UY = 5 75 1 30.2 yx 

U* . og K. ' (1) 

where Uv=average point velocity at distance y above 

the streambed; 

U*=shear velocity, ..jgDS; 

g= acceleration due to gravity; 

D= depth of flow; 

S=slope of the energy grade line; 

x= a corrective parameter; and 

Ks=grain roughness. 

For the distribution of sediment concentration with 

respect to depth, 

Cy=[D-y._a Jz' 

Ca y D-a (2) 

where Ov=concentration of particles at distance y above 

the bed, 

Oa=concentration of particles having the settling 

velocity w at distance a from the bed, and 

z=w/0.40 u*. 

The concentration, 0, obtained by velocity-weighted 

samples, and the water discharge in the sampled zone, 

Qm, are used to compute the sediment discharge per 

unit of time, q., through the sampled zone 

(3) 

ART. 149 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D134-Dl37. 1964. 

Dl34 
GUY AND SIMONS D135 

Equation 3 is also equivalent in concept to the sediment 

discharge, q8 , determined by the relation 

(4) 

where Cu and Uu are defined by equations 1 and 2. 

Figure 149.1 shows the approximate variation of 

velocity, sedi1nent concentration, and sediment discharge with depth. This illustration and the preceding 

equations show that the mean concentration as weighted 

with velocity is considerably lower than the spatial 

concentration. The relatively low velocity-weighted 

concentration is due to the integration with depth 

ranging from low concentration and high velocity near 

the strean1 surface to high concentration and low 

velocity near the streambed. The spatial concentration, on the other hand, is the mean of the concentration 

from top to bottom and thus is considerably greater 

than the velocity-weighted concentration. Under the 

rare condition when all the sedi1nent being transported 

is very fine, the concentration 1nay be uniform fron1 

top to bottOin. Under this condition, spatial and 

velocity-weighted concentrations are equal. 

I 

I 

I 

I 

I 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\. 

·§! 

0 

lj 

I 

I 

j'-........s~Cii 

/ 

....._tqe,.,t ........ co,., 

Flow ------+ 

..._ __ -.c!:._ntration 

/ Streambed ---

Increasing values ---~ 

FIGURE 149.1.-Relative gradients of velocity, sediment con- centration, and sediment discharge with depth. 

Streamflow data show that neither Uu nor Cu are 

spatially or temporally consistent as defined in the 

equations; therefore, a sample of sediment or velocity 

at a point in a stream vertical or cross section cannot 

define the concentration or velocity distribution in 

such a vertical or cross section. To overcome this 

difficulty, the "precise method" was developed. This 

method, as described by the U.S. Inter-Agency Committee on Water Resources, Report 1 (1940, p. 63) 

involves collection of a relatively large number of point sediment 

samples simultaneously with velocity measurements. Sufficient 

data are collected to construct accurate vertical velocity and 

sediment distribution curves, the corresponding abscissas of 

which are multiplied to obtain a sediment-velocity curve. The 

area under this curve represents the sediment discharge in the 

vertical. 

Needless to say, the "precise method" was too laborious 

for routine investigations of sediment movement in 

streams. The velocity-weighting technique, commonly 

called the depth-integration method, was developed 

to facilitate sediment-data collection and analysis. 

The technique, as described by the U.S. Inter-Agency 

Committee on Water Resources, Report 6 (1952, p. 14) 

is as follows: 

The discharge of the depth-integrating sampler was predicated 

on the hypothesis that an integrated sample of the watersediment mixture existing at the place and time of sampling 

would be obtained if the filling rate were such that the velocity 

at the point of intake is equal to the local stream velocity while 

the sampler is moved at a uniform vertical speed in the stream. 

The spatial concentration may be used to determine 

the actual load (weight per unit area) in transport over 

the streambed. It is also the correct concentration for 

determining the specific weight of the water-sediment 

con1plex. The spatial concentration can be obtained in 

strean1flow by averaging the concentration of several 

equally spaced point samples in the stream cross section. 

In the laboratory, Bagnold (1955) used a mechanical 

device for isolating a rectangular slug of flow in a flu1ne 

(fig. 149.2). A representative sample of spatial concentration is generally difficult to obtain because of the 

unsteady motion of particles near the bed. Most point 

samplers do not operate closer than within 0.3 or 0.4 

foot of the bed. The Inechanical-isolation device cannot distinguish between stationary and moving particles 

and thus cannot be used on an alluvial bed. 

EXPERIMENTAL RESULTS 

The difference between the velocity-weighted and 

spatial concentrations was studied by a series of runs in 

an 8-inch-wide recirculating flume. Plastic pellets with 

a specific gravity of 1.04 to 1.06 and with a Inedian 

diameter of about 3 mm were used to represent the 

sediment grains. Samples were taken with a mechanical-isolation device after the velocity was sufficient to 

insure that all sedi1nent over the bed was in motion, 

even though son1e particles were moving very slowly. 

The variation of sedinwnt concentration and velocity 

with depth appeared to approxin1ate that indicated by 

equations 1 and 2 and as illustrated in figure 149.1. 

Sediment concentration was san1pled by both Inethods 

for six different series of runs whereby each series contained a different amount of sediment circulating in the 

flume. To maintain the same amount of sediment in 

circulation, an equivalent volume of sample was returned to the flume for each sample removed. Two of 

these series were sampled at three widely different 
D136 SEDIMENTATION 

velocities. Velocity-weighted san1ples were taken by 

collecting in a nylon-mesh b31sket all partieles discharged at the tail end of the fimne. San1pling periods 

ranged fron1 8 to 15 seconds. Spatial-concentration 

sarnples were taken by quickly isolating with a sharpedged frame having wire mesh ends, the water and 

sedinwnt n1oving in a 1-foot length of the flmne. This 

device is similar to the sarnpler illustrated in figure 149.2. 

\ 

----Flow 

-------------------------------

FIGURE 149.2.-Side view of sampling device for determining 

the spatial concentration of sediment moving in an open 

channel (after Bagnold, 1955). 

The flow was stopped irnrnediately after isolating the 

sample, and the partieles were rernoved by siphoning 

frorn the known volmne of water. 

The concentrations in parts per rnillion by weight for 

both methods of san1pling are smnmarized in the accompanying table. This shows the concentration n1ean, the 

Concentrat£on of velocity-wdghted and spatial samples of plastic 

pellets from 8-inch flume 

I Velocity-weighted concentra- I Spatial eoncentration on flume 

tion at tailbox (ppm) bed (ppm) 

Flume Mean run velocity 1 1 I 

1\Iean deviatiOn probable Mean deviation probable 

(ft/sec) Stanrlardl Limit of Standard Limit of 

error 1 error I 

------1----1-------'--

l_________ 2.09 85,000 1,350 I 2,290 I 110,600 6,920 I 6,830 

2_________ 1.72 63,200 6.950 11,700 92,100 10,300 12,200 

3_________ 1.66 41,3oo I.9oo 1 3.22o 58,7oo 7,31o 7,o5o 

4 ___ ------ 1. 18 20, 900 890 i 2, 610 40, 300 4, 450 7, 530 4_________ 1. 67 24. 8oo 1.14o 1 2. 69o 29, 4oo 5.14o 4. 92o 

4 2_______ ~ •• 6

46

7 24.8oo 1.

7

14

5

o

0 

I 2,690 21.4oo 95o 1.161 4_ __ _ __ _ _ _ _ 24. 400 1. 280 26. 800 2. 500 I 4. 220 

5________ 1.81 I 10,800 560 I 940 13,400 2, 760 3,260 

6_________ 1.13 3,500 130 I 220 5,760 890 850 6_________ 1. 42 3, 440 I 260 i 440 5, 250 970 i 1,140 

6_________ 2.871 3,890 I 1051 180 3,870 670 I 640 

I Limit of probable error of measurement at 90-pereent confidence level. z Spatial samples collected near head box of flume. 

standard deviation, and the limit of probable error of 

measuren1ent at the 90-pereent confidence level for each 

run. The sedin1en t coneen tra tion ranges from t1 velocity-weighted value of 85,000 pp1n and a spatial value of 

110,600 ppn1 on the flume bed for run l to a velocit.vwpighted value of 3,440 ppm and a spatial value of .5,250 

ppm on the flume bed for run 6. The error of measurement is appreeiably less at the tailbox bec~1use of the 

greater time of sampling; hence., only 3 samples were 

taken at the tail box for each run, \vhereas 5 were taken 

on the flume bed for nwst runs. 

The sample concentrations compared in figure 149.3 

illustrate the differences between the two methods of 

detern1ining concentration. As expected, the spatial 

concentration is greater than the velocity-weighted 

concentration. The limits of the probable error of concentration rneasurement (90-pereent confidence level) 

are shown (fig. 149.3) in the forrn of a rectangle approximately centered over each coneentration mean. These 

rectangles indicate that the variability in the movement 

of sedirnent, and consequently the measurement error, 

is greater for the spatial means than for the velocityweighted means. 

z 

0 

i= 

<( 

0::: 

I- z z 0 LLJ :i () ....1 z 

0 ~ 

() 

0::: 

Cl LLJ 

LLJ ll.. 

I- (j) I 

(!) I0::: w <( 

~ ll.. 

I->- ~ 

0 

0 

....1 

LLJ 

> 

50'000 f.------+--S-p-at-ia-1-+s-am-p-le._c_o-ri'le-c-te-d--"""71"--

near headbox of flume 

I " 

20,000 1-~---+----t---~ <::-----,i'~---1 <::-..::.~ (;0 

o~ I 

~(; I ~ 0 ]i-"5'-l------+----+--i 10,0001-------+-, - .... -

0

o.v , 

I o .;;:-0 

v 

5000 ~~--~L---t-------+----+----t---1 

I I 

I 

I 

\ 

SPATIAL CONCENTRATION, IN PARTS PER MILLION 

FIGURE 149.3.-Relation of velocity-weighted concentration to 

spatial concentration. The rectangle centered approximately 

around each concentration shows the limit of probable error of measurement at t.he 90-percent confidence level. Numbers 

correspond to tlume runs described in table. 

The larger the variation of velocity and sediment 

concentration with respect to depth ( eomparatively 

high V near the surface and a comparatively large C 

near the bed) the greater the differenee between the 

two concentrations. As indicated by the highest velocities sampled (runs 4 and 6) the two methods nuty be 

comparable when the sediment is thoroughl~r suspended. 

In fact, the reverse of the normal result was found by 

compa~ing spatial eoncentrations fron1 near the head box 

with the velocity-weighted eoneentrations at the tailbox. 

The lower mean concentration of the spatial samples 

(see table and fig. 149.3) is caused by an inversion 

of the normal concentration gradient due to centrifugal 

foree on the sedi1nent particles. 

CONCLUSIONS 

V eloei tv n.nd seclimen t-eoncen tra tion clistri bu tions in 

a cross s~ction of streamt1ow can be predicted only 
GUY AND SIMONS D137 

within rough limits. Theoretical n,nd measured differenees between spatial and velocity-weighted concentrations show that: 

] . The dissimilarity between the two measures of concentration widens as the velocity and concentration gntdients increase with respeet to depth. 

2. Sediment discharge in t't stream should be comp.uted 

from a velocity-weighted concentration obtained 

by sampling at several points or verticals in the 

stream cross seetion. Routine men,surements of 

velocity-weighted eoncentration are made with 

several kinds of depth-integn1ting samplers. 

3. Spatial concentration is needed when either the 

actual load or amount of sediment exerting pressure on the bed or the n.verage specifie weight of 

the sedin1ent-water mixture over the bed is desired. 

lVIeasnreinent of spatial concentration is usmtlly 

difficult because innnobile particles eannot be 

distinguished frmn moving particles. 

REFERENCES 

Bagnold, R. A., 1955, Some flume experiments on large grains 

but little denser than the transporting fluid, and their implications: Civil Engineers Proc., Excerpt pt. III, London, 

p. 192. 

Einstein, H. A., 1950, The bed-load function for sediment transport in open channeis: U.S. Dept. Agriculture Tech. Bull. 

1026, p. 7-17. 

U.S. Inter-Agency Committee on Water Resources, 1940, Report 

1-Field practice and equipment used in sampling suspended 

sediment: U.S. Army Corps of Engineers, Iowa City, Iowa. 

U.S. Inter-Agency Committee on Water Resources, 1952, Report 

6-The design of improved types of suspended sediment 

samplers: U.S. Army Corps of Engineers, St. Paul, Minn. 
Article 150 

TEMPORARY STORAGE OF FINE SEDIMENT IN ISLANDS AND POINT BARS 

OF ALLUVIAL CHANNELS OF THE RIO GRANDE, NEW MEXICO AND TEXAS 

By CARL F. NORDIN1 JR. 1 and JOSEPH P. BEVERAGE1 

Fort Collins1 Colo. 1 and Albuquerque1 N. Mex. 

Abstract.-Islands and point bars are semipermanent features 

of alluvial channels. They contain as much as 20 percent surficial material finer than 0.062 mm which is deposited during 

receding flows. Some of the scatter generally noted in discharge-transport relations probably derives from the transient 

storage of the fine material, which is flushed during higher 

discharges. 

The fine material transported by a stream is obtained 

from the soil of the watershed, from old flood plains 

by bank cutting and sloughing, and frOln deposits 

within the active channel of the stream. Deposits in 

the channel include islands, point bars, and other slackwater deposits. Although islands and point bars may 

be sernipennanent channel features, they are periodically inundated and reworked in strearns that have fairly 

wide variations in flow. The Rio Grande in New 

Mexico is such a stream. 

Figure 150.1 shows the particle-size distribution of 

channel bed 1naterial and bar material fron1 the Rio 

Grande near Bernalillo, N. Mex., on June 1, 1962, at 

a sampling location designated section F. At the time 

of sampling, the bar projected 0.1-0.4 feet above the 

water surface and occupied about half of the high-flow 

channel width. Samples from the bar contained about 

9 percent n1ore fine material (diameter <0.062 nun) 

than san1ples from the wetted perimeter. Figure 150.2 

shows similar curves for the Rio Grande, downstream, 

near Anthony, Tex., on April 16, 1962. Bar material 

at this site contained about 17 percent n1ore fine material (diarneter <0.062 mm) than channel material. 

These san1ples were collected from bars or islands 

formed in areas of decreased velocity during receding 

flows. At both sampling sites the bars occupied a 

third to a half of the bankfull channel width. 

Islands and point bars are generally considered to be 

deposits of coarser rnaterial, which is transported in 

appreciable quantities only at high flows. The san1ples 

99 

I 

98 

0 Bar /, 95 01 e Channel 

90 I. 

80 10/ c:: 70 w 

z 60 Li: 

1- 0 • z 

w 

/0/0/ I u 40 c:: 

w 

0.. 30 

I 

• / 

0.1 0.5 

DIAMETER, IN MILLIMETERS 

FIGURE 150.1.-Particle-size analyses of 

bar and channel material from the Rio 

Grande near Bernalillo, N. Mex., on 

June 1, 1962. 

from the Rio Grande near Bernalillo, N. Mex., and 

Anthony, Tex., indicate, however, that the bars and 

islands of the river may include from 10 to 20 percent 

fine n1aterial. Wolman and Leopold (1957, p. 95) reported three point-bar samples fron1 Watts Branch near 

Rockville, Md., that averaged 20 percent fine rnaterial. 

They concluded that part of the n1aterial eroded from 

the drainage basin "is stored ten1porarily in point bars 

and in the flood plain at various places m the channel 

systenL'' 

ART. 150 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl38-Dl40. 1964. 

D138 
NORDIN AND BEVERAGE D139 

99 

98 

0 Bar I I 

95 0 • e Channel I 90 

80 

0:: 70 LIJ 0 z 60 I ~ • ~ 50 z 

LIJ 

(.) 40 0 0:: 

0/ 

LIJ 

c.. 30 

20 / • 

10 I 5 

2 

1 

0.06 0.1 0.5 

DIAMETER, IN MILLIMETERS 

FIGURE 150.2.-Particle-size analyses of 

bar and channel rna terial from the Rio 

Grande near Anthony, Tex., on April 

16, 1962. 

The fine material in islands and point bars of the Rio 

Grande is generally flushed out by high flows, such as 

spring snow1nelt and sustained reservoir releases. The 

accompanying table lists discharge and concentration 

of various size elasses of suspended sediment for the 

Rio Grande near Bernalillo during two spring runoff 

periods. In both runoff periods, the concentration of 

fine rna terial decreased with tin1e regardless of wide 

variations in discharge. 

Discharge and concentration of suspended sediment, by s1:ze class, 

in the Rio Grande near BernaWlo, N. }.;lex., dur,ing the spring 

runoff of 1952 and 1958 

Concentration, by size class (ppm) 

Discharge Date (cfs) 

<0.062 0.062-0.125 0.125-0.250 nun nlnl 111111 

1952: 

April 25 ___________ 2, 910 1,270 9Ml 423 Th1ay 12 ____________ 6,390 1, 160 646 753 

June 17 ____________ 6, 100 375 390 555 

June 20 ____________ 4, 720 321 336 55.5 

June 26 ____________ 2, 8.50 222 264 273 

1958: 

Th1ay 8 _____________ 6, 730 2,020 1,080 1, 360 ~ay 13 ____________ 8, 310 1, 650 1, 270 1,060 Th1ay 21 ____________ 8, 700 1, 210 904 1, 070 ~ay 27 ____________ 9, 970 1, 040 796 1, 040 

June 4 _____________ 7, 790 750 575 675 

June 10 ____________ 5, 450 621 476 724 

June 13 ____________ 4, 380 318 418 856 

716-626 0--64--10 

98 

95 

90 

0:: 70 LIJ 

~ 60 

!z 50 LIJ 

~ 40 LIJ 

c.. 

0.1 0.5 

DIAMETER, IN MILLIMETERS 

FIGURE 150.3.-Particle-size analyses of 

bed material from the Rio Grande near Bernalillo, N. Mex., ~ay 8 and June 13, 

1958. 

The apparent lack of relation between discharge and 

concentration of the sand sizes (>0.062 1n1n) suggests 

that these fractions, like the fine 1naterial, behave as 

"wash load." Wash load is that part of suspended 

sediment "which is washed through the stream channel 

without any deposition" at a rate dependent only on 

its availability frmn the watershed (Einstein and Chien, 

1953, p. 31). Although changes in availability of 

material frmn the watershed may explain so1ne of the 

lack of relation for the sand fractions, changes in the 

size distribution of the bed n1aterial should be considered as well. Figure 150.3 indicates that the diameter 

of the bed 1naterial can increase markedly during several 

weeks of sustained high flow. As the size of bed 

material increases, the an10unt of the finer sand fractions 

available for suspension and transport by the stream 

decreases. 

During receding and low flows, clayey silt and fine 

sand are stored on islands and point bars and, to son1e 

extent, within the active channel (fig. 150.3). During 

rising stages and during sustained high flow, t,he b.ars 

and islands serve as a source for fine n1atenal. 

Throughout sustained high flows, the concentrations of 

the fine 1naterial and of the fine sand fractions seen1 to 

vary as a function of time rather th~n of discharge (see 

table). Both the magnitude of the concentration and 

the rate of change in concentration with tin1e probably 
D140 SEDIMENTATION 

depend partly upon antecedent conditions, that is, 

upon how much fine rnaterial was stored during previous 

low flows. 

Storage tin1e of fine rnaterial in bars and islands of 

the Rio Grande ranges from several rnonths to a year 

and depends on subsequent climatic and hydrologic 

conditions, which detern1ine when the channel features 

again becorne part of the wetted perimeter. When the 

stage rises, the strearn begins to erode the deposits and 

to resuspend the fine material. 

This study indicates that some of the apparently 

randorn scatter in discharge-transport relations can be 

explained in terms of the time dependency of the 

concentration of the finer sand classes and of rnaterial 

finer than 0.062 nun. This tirne dependency is due, in 

part, to temporary storage within the active channel. 

REFERENCES 

Einstein, H. A., and Chien, K., 1953, Transport of sediment 

mixtures with large ranges of grain sizes: California Univ. 

Inst. Eng. Research, Missouri River Div. Sediment Ser. 2. 

Wolman, M. G., and Leopold, L. B., 1957, River flood plainssome observations on their formation: U.S. Geol. Survey 

Prof. Paper 282-C, p. 87-109. 
Article 151 

FLUVIAL SEDIMENTATION IN MAMMOTH CAVE, KENTUCKY 

By CHARLES R. COLLIER and RUSSELL F FLINT, 

Columbus, Ohio 

Work done 1:n cooperation with the National Park Service 

Abstract.-Alternating deposition and erosion occur in Mammoth Cave by flooding from the Green River. In 2% years, 

numerous low floods deposited 0.5 foot of sediment in the lowest 

levels. Three high floods removed that sediment, but caused 

thinner deposits at higher levels. The coarsest sediment is 

deposited in the lower parts of the cave. 

The sources of sediment and rate at which it is being 

deposited in Ma1nmoth Cave, Ky., have long been of 

interest to geologists and speleologists. Detailed 

n1easurements by the U.S. Geological Survey of erosion 

and deposition between October 1959 and June 1962 

indicate that sedimentation in the cave is closely related to flooding of the nearby Green River. 

The Green River, which is hydraulically connected to 

-rvianunoth Cave by Echo River spring and River Styx 

spring, is the chief source of sedi1nent and floodwater to 

the cave. These springs are submerged during floods of 

the Green River, and water then enters the cave through 

them so that the water level in the cave corresponds 

closely to the level of the Green River (Hendrickson, 

G. E., 1961). W. E. Davies and E. C. T. Chao (written 

communication, 1959) found in their studies of "Nlalnmoth Cave that the sedin1ents in the lower levels of the 

cave are similar in physical character and mineralogy 

to the sediments on the flood plain of tJ1e Green River. 

The turbulence Hnd velocity of the floodwater entering 

the cave are sufficient to transport sediinent into the 

cave, particularly during rapidly rising water levels. 

These saine forces may c~tuse a Hushing of sedin1ent 

fron1 the cave during rapidly falling water levels. 

Thirteen lines were surveyed across cave passageways 

that are subject to flooding, and the elevations above 

gage datum of the sediment deposits on these lines were 

determined. These lines, or ranges, served as bases 

from which changes in deposition were determined by 

later surveys. The approximate locations of the ranges 

are shown in figure 151.1, and the elevations of the cave 

floor at each range are shown in the accompanying table. 

Resurveys of the ranges in August 1961 and in 

January and June 1962 indicated that the greatest 

changes in deposition occurred at the lowest elevations 

(see table). Alternating deposition a,nd erosion were 

observed at some ranges. Movement and redeposition 

of sediinents were shown by recovery of ribbons placed 

vertically in the deposits of sedi1nent. The lower and 

more frequent floods apparently eaused deposition in 

the boat-ride section of Echo River. The higher and 

less frequent floods, however, tend to remove these 

deposits from the Eeho River ehannel but cause 

deposition at the highest flooded and intervening levels. 

Frmn October 1959 to January 1962, as much as 0.4 

foot of sedi1nent wa,s deposited in the boat-ride section 

of Echo River (ranges 1, 2, 3, table). In the higher 

passages, at elevations of .5 to 25 feet above the gage 

datum, only smnll ehanges in deposition or erosion were 

observed. No floods exceeded 31.4 feet during this 

period, although 2 floods exceeded 21.5 feet and 8 

exeeeded 17.7 feet. 

Three floods exeeeded 21.5 feet in tlanuary, February, 

and early ~lareh 1 H62. One of these floods reached 

.57.1 feet and is the highest flood of reeord. All three 

floods generally eaused deposition in the passages n.hove 

the 5-foot elevation1 but they rmnoved a.bout 0.5 foot 

of sediment from the boat-ride section of Eeho River. 

The partiele size of the deposited sedi1nent is somewhat related to the elevation of the deposit. Deposits 

at elevations below 16 feet are predominantly sand 

(0.062 to 2.0 nun diameter)) ~tnd the deposits at higher 

elevations are predominantly silt (0.004 to 0.062 mm 

dinmeter). This correlation is shown by the grouping 

of points in figure 151.2, a plot of the median particle 

ART. 151 IN U.S. GEOL. 8URVEY PROF. PAPER 475-D, PAGES Dl41-Dl43. 1964. 

D141 
D142 SEDIMENTATION 

Flooding and changes in deposition at sedimentation ranges in Mammoth Cave, October 1959 to June 1962 

Oct. 1959 to Aug. 1961 Aug. 1961 to Jan. 1962 Jan. 1962 to June 1962 Oct. 1959 to June 1962 Elevation of cave floor (ft) 

Oct. 1959 1 

Range No. Percen- Net Net Percen- Net Percen- Net 

---------- Times tage of change I Percen- Times tage of change Times tage of change Times tage of change flooded2 days (ft) flooded 2 days (ft) flooded2 days (ft) flooded2 days (ft) Low High Mean flooded2 flooded2 flooded2 flooded2 

------ ----------

1 __________ -1.3 +5. 0 +O. 3 ------ 100 +O. 48 ------ 100 -0.03 ------ 100 -0.55 ------ 100 -0.10 2 __________ -4.9 -. 3 -2. 1 ------ 100 +. 20 ------ 100 -------- ------ 100 3 -. 45 ------ 100 -. 25 3 __________ --3.2 +L7 -1.6 ------ 100 +. 34 ------ 100 -------- ------ 100 3 -. 46 ------ 100 -. 12 4 __________ -8.0 +1.5 -5.4 ------ 100 . 00 ------ 100 -------- ------ 100 3 +. 04 ------ 100 +. 04 5 __________ -5.2 18. 1 9. 8 18 34 +. 22 2 17 -. 15 6 58 -. 24 26 36 +. 31 6 __________ 13.4 18.2 15. 3 19 12 -.11 2 7 +. 08 6 20 -.18 27 12 +. 15 7 __________ 11. 2 14. 9 11. 9 18 15 +. 01 2 7 +. 14 6 23 +. 42 26 15 +.57 8 __________ 3. 5 11. 4 6. 6 15 77 -.10 6 29 -. 13 ------ 100 +. 33 21 75 +. 10 9 __________ 3.4 9. 5 5. 6 15 86 -. 29 6 44 +. 07 ------ 100 +. 13 21 83 -. 09 10 _________ 17. 8 24. 6 20. 0 6 4 +. 05 1 2 . 00 3 14 +.13 10 6 +.18 11_ ________ 17. 7 26.4 20.3 7 4 +. 13 1 2 +. 06 3 14 -. 02 11 6 +.17 12 _________ 21. 5 30. 9 25. 6 2 1 -.11 0 ------ -------- 3 10 +. 28 5 3 +. 17 13 _________ 31. 4 34. 5 32. 2 0 ------ -------- 0 ------ -------- 1 5 +. 20 1 1 +. 20 

I Arbitrary gage datum. 2 Includes both complete flooding and partial flooding. a August 1961 to June 1962. 

;V~ (River Hall 

0 200 

0 

EXPLANATION 

Passage dry during 

low water level 

Submerged area 

during low water 

600 1000 FEET 

N 

I 

FIGURE 1_51.1.--Ma~ of lower ~evel of Mammoth Cave, showing 

approximate locatiOn of sediment ranges. Pattern indicates area submerged at low water level. Base from National 

Park Service map, 1935. 

size against the average elevation of the floor at each 

range. A noticeable inconsistency in this grouping is 

the January 1962 sampling from ranges 7 and 8. The 

sarnples frorn these. two ranges included only the 

surface material, whereas san1ples at the other ranges 

were taken at depths of 1 to 4 feet. 

The coarser particles tend to rnigrate by successive 

floods to higher elevations. This conclusion is supported by the position of the June 1962 triangles in 

figure 151.2 for elevations between 10 and 25 feet. 

Sediment deposited at these elevations generally 

had a larger rnedian diameter after the floods of 

January to March 1962 than before. This increase 

in median diameter would occur if, during rising water 

level, there were sufficient turbulence and velocity to 

~ 35 ~ 

::J 

1-

~ 30 

w 

(!) 

< 8 25 

1-

w 

w 

LL. 20 0 11(/) 

10 ffi ~ 

ci 

0 15 0 

III 

~ 

0 '\1 6 ::J 

z ...J w LL. 

LL. 10 0 

l:::. '\1 (!) 

z .6. 0 \1 < 0::: 

z 

0 

i= 5 < 

l:::. ~\1 0 0 

\1 

> w 

...J 

w 0 t:::.w z 

< w l:::.'ifJ % ~ -5 

0.005 0.01 0.05 0.1 0.5 

MEDIAN PARTICLE-SIZE DIAMETER, IN MILLIMETERS 

FIGURE 151.2.-Relation of median particle size of deposited 

sediment to mean elevation of floor, Mammoth Cave, Ky. 

Circles, samples taken October 1959; triangles (point up), 

August 1961; squares, January 1962; triangles (point down), 

June 1962. 
COLLIER AND FLINT D143 

transport coarser particles through the passages to 

settle at higher elevations. Hydrographs of the water 

level in the cave show that during floods the water 

generally rises more rapidly than it falls. Turbulence 

and velocities probably are greatest during the more 

rapidly changing water levels during the rise of a flood. 

Clay particles are more easily transported than silt 

or sand and therefore are moved for greater distances 

by floodwater. After every flood, a thin layer of clay 

is deposited over all the submerged passageways. The 

record flood in February-March 1962 left an average 

deposit of 0.2 foot of clay and silt at range 13, elevation 

32.2 feet. 

The three resurveys of the range lines in Mammoth 

Cave over a period of less than 3 years provide an 

indication of sediment movement in the cave. Deposition or erosion during a given flood depends upon (1) 

the rate at which the water rises, (2) the height of the 

flood, (3) the duration of the flood, and (4) the rate of 

fall. The rate of rise or fall and the height of the flood 

influence the turbulence and velocity of the water in 

the cave and, therefore, the capacity of the water to 

transport sediment. The duration of the flood, particularly the period of little change in water level at the 

flood crest, determines the time available for settling 

and deposition of the sediment. 

REF'ERENCE 

Hendrickson, G. E., 1961, Sources of water in Styx and Echo 

Rivers, Mammoth Cave, Kentucky: Art. 308 in U.S. Geol. 

Survey Prof. Paper 424-D, p. D41-D43. 
Article 152 

QUA TERNARY MUDFLOW DEPOSITS NEAR SANTIAGO, CHILE 

By KENNETH SEGERSTROM; OCTAVIO CASTILLO U./ and EDUARDO FALCON M./ 

Denver1 Colo.; Santiago1 Chile 

Work done in cooperation with the I nstituto de I nvestigaci6nes Geol6gicas de Chile 

under the auspices of the Agency for Internat£onal Development, U.S. Department of State 

Abstract.-~vludfiows appear to have played an important role 

in the accumulation of nonsorted, nonstratified Quaternary 

valley rill in central Chile. 1\1 uch of the mudflow material in 

the vicinity of Santiago is pumiceous. A widely accepted 

hypothesis of glacial origin for these deposits is rejected. 

Santiago, the capital city of Chile, is in a tectonic 

depression or graben that forms the Valle Central of 

Chile (fig. 152.1). The depression is partly filled with 

unconsolidated sediments of Quaternary age. 

Large volumes ofnonsorted and virtuallv nonstratified 

valley-fill sediments at or near Los Cerriflos, Pudahuel, 

Cerro Apoquindo, and Puente Alto (fig. 152.2), have 

been described by various workers as moraines (Brtiggen, 1950; I{arzulovic, 1958; Mufioz Cristi, 1960). 

Brief observations by R. F. Flint in April 1959 of some 

of the deposits, particularly of those containing large 

volumes of pumiceous ash, cast considerable doubt 

on a glacial origin. Later and more detailed examination by the authors confirms the nonglacial origin of 

these deposits, which are now believed to result from 

mudflow deposition and creep. The general term 

"diamicton" is applicable to at least some of these 

nonsorted noncalcareous terrigenous deposits composed 

of sand and larger particles in a matri.x of mud (Flint 

and others, 1960a, b). 

The Valle Central near Santiago is filled to a depth of 

more than 400 meters with sedimentary materials 

eroded from the surrounding highlands and transport,ed 

by running water, mudflows, or as slides. Most of the 

J Instituto de Investigaciones Geo16gicas. 

materials are derived fron1 the Cordillera de los Andes 

to the east; lesser amounts have been eroded from the 

Cordillera de la Costa to the west. The bedrock in both 

ranges is mainly igneous, including both volcanic and 

intrusive types, and is predominantly of Mesozoic age. 

The oldest valley-fill sediments known in the area are 

lacustrine silt, clay, and sand at a depth of as much as 

250 m in study well 1, near Pudahuel, and 236 m in 

well E3-26, in Santiago (fig. 152.2). The age of these 

sedi.ments is unknown, although in well 1, small freshwater gastropods were found in microlaminated clay 

at a depth of 157 m. 

The fine-grained lacustine sediments of the valley are 

overlain by coarse-grained fluvial materials which in 

well E3-26 extend to a depth of 150 m below the surface. Alluvial-fan deposits of the Rfos Lampa, Colina, 

Mapocho, and Maipo make up the bulk of these materials. Gravels are exposed in terraces along the Rio 

Maipo and in gravel pits around the fringes of Santiago. 

Colluvium resulting from sheet erosion occurs in narrow zones bordering the valley, particularly north and 

west of Santiago. Knowledge of the origin and character of the valley fill is especially important in problems 

of ground-water supply, which are discussed in Article 

169. 

Diamicton deposits overlie altered bedrock along ~he 

mountain front east of Santiago and interfinger with 

alluvium in the basin. Pumiceous deposits, which contain large blocks of andesite and granodiorite and cover 

the fluvial and lacustrine deposits west of Santiago, appear to be of sim1lar origin. Other pumiceous deposits 

ART. 152 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D144-D148. 1964. 

Dl44 
SEGERSTROM, CASTILLO U., AND FALCON M. Dl45 

72 ' 33' 

0 

L--·- --' 

FrcuRE 152.1.- Index map of part of central Chile. 

which do not contain large blocks of other rock, found 

in the valley of Estero Papeta and in the basin of the 

Rio Rapel, southwest of Santiago (fig. 152.1), appear to 

be lacustrine (Briiggen, 1950, p. 221). 

Within the area of figure 152.1, unquestioned till is 

limited to the high Cordillera de los Andes. Moraines 

are found at minimum aHiLudcs of 1,600 m in one or 

two valleys (that of the Rio Colorado, for example), 

but mos·L till and all glacial cirques occur above 2,000 

rn at lat 33 °- 34 ° S. The best exposed and most accessible moraine in the region extends 12 km along the 

Rio Ycso, between 1,670 and 2,700 m above sea level, 

and terminates on the south side of Laguna Negra 

(fig. 152.1). The till of this moraine has a matrix of 

grny unweathered rock flour. The included blocks arc 

angular and are of two lithologic types, granodioriLe 

and andesite. The granodiori te blocks are as much as 

4 m across; those of andesite are as much as 1 m or a 

liLtle more. Through much of the moraine Lhe two 

kinds of boulders are segregated in to alternate bands 

subparallel to the valley trend. The bands are boulder 

trains derived directly from intrusive and volcanic bedrock farther up the valley. 

5 rJ \ 

1) 

~ 

0 

() 

50 KILO M E"TE RS I . 

70' 

<1l 

~ 

(/) 

Quaternary valley-fill deposits outlined by dashed line. 

DIAMICTON DEPOSITS 

The diamicton deposits of the region are of two types: 

one contains little or no pumice, and the other contains 

abundant pumice. 

Diamicton deposits of the first type form a hummocky topography along the foot of the steep Andean 

front at the east edge of the Valle Central between the 

Rio ~apocho and the Rio Maipo (fig. 152.2), in a belt 

800 m to 4 km wide. An outstanding feature of this 

belt is a row of hills that extends 5 km from Loma de 

los Banos northwest to Cerro Calan. The material that 

makes up the hillocks is well exposed in a cut between 

Loma de los Banos and Cerro Apoquindo, where an ~ 

gular to subrounded blocks of granodiorite and andesite 

as much as 2 m or 3 min diameter are found in a matrix 

of weathered clasts ranging from clay size to coarse 

gravel. Here and in other parts of the deposit are 

scattered lenses, 1 to 2 rn thick and as much as 10 or 

15 m long, of pumiceous ash and sand or gravel, generally consisting of subangular grains. A gravel lens 

on Cerro Calan contains rounded cobbles. Deposits 

resembling those exposed in t he cut between Lorna de 

los Banos and Cerro Apoquindo crop out on the south 
D146 SEDIMENTATION 

; · 

SANTIAGO 

'I\ 

I 

I . 

:I. r-! · 

-----,\ . \ EXPLANATION 

Silt and sand deposited 

by modem streams 

Diamicton 

deposits 

Contact 

Slope • wash 

deposits 

Pumiceous 

diamicton 

deposits 

0 

L.:_j 

~ 

Coarse fluvial 

materials 

(chiefly gravel) 

D 

Bedrock 

5 KILOMETERS 

J /-

./ 

__.,· 

. . . .. . ~~:.~ . 

. Puente Alto . 

------=-~ 

FIGURE 152.2.-Map of surficial deposits in the vicinity of Santiago. 

side of the Rio. Mapocho and between Lorna de los 

Banos and the Rio .Maipo. All these deposits are more 

than 30 m thick, and at Cerro Calan they are approximately 100 m thick. They overlie deeply weathered 

rock to the east and interfinger with fluvial deposits 

from the Cordillera de los Andes toward the west. 

East of Puente Alto, immediately north of where the 

Ri6 M aipo emerges from the Cordillera de los Andes, is 

an enormous fan-shaped diamicton deposit that extends 

downward and outward from an amphitheater-shaped 

hollow in the mountain front to the northeast. Angular blocks of granodiorite within and on top of the 

mass are so large and numerous that some of the diamicton deposits are easily confused with bedrock. Near 

the foot of the deposit a small lens of pumiceous sand 

is exposed in a highway cut 2 km north of the junction 

of the Santiago- El Volcan highway with the road to 

Puente Alto. 

The most extensive deposit of the pumiceous diamicton forms a hummocky surface in the lowest part of 

the valley (Pudahuel- Los Cerrillos), immediately west 

of the city of Santiago at 450 to 485 m above sea level 

(fig. 152.2). It is exposed to depths of 10 m or less in 

a dozen or more large quarries, and study of drill cuttings indicates that the deposit extends to depths of as 

much as 30 m. The material consists of white or 

grayish fragments of pumice, predominantly of sand 

size, but including also silt and gravel. The deposits 

are poorly sorted and without stratification. Irregularly distributed subangular to subrounded blocks of 

andesite and granodiorite as large as 80 em in diameter, 

some of which are highly decomposed, make up, on an 

average, about 20 percent of the total volume. 

Other pumiceous diamicton sediments crop out on 

the south side of the valley of the Rio Y eso, along the 

Estero Collanco near its junction with the Rio Maipo 

and in the Melipilla area (fig. 152.1). On the summit 

and north flank of a ridge between the Rio Y eso and El 

Volcan, there are small bodies of sand, locally pumiceous 

and containing scoriaceous fragments as much as 20 
SEGERSTROM, CASTILLO U., AND FALCON M. D147 

cn1long. These deposits fill small depressions and form 

scattered patches on slopes 300 m to 450 n1 above the 

valley floor. Pumiceous float is found in colluvial deposits that consist chiefly of andesitic materials as much 

as 650 In above the valley. In a stream terrace 30 m 

above the lower course of the Estero Collanco a diainicton deposit is exposed that contains angular to subangular blocks as large as 2 n1 across in a light-gray 

ashy, partly puiniceous matrix. The blocks are of 

varied composition and are decomposed. 

The western slope of the Andes is very steep, dropping 

from 3,200 to 700 m above sea level in a horizontal 

distance of 12 kn1, just east of Santiago. Because of 

the great relief, mass n1oven1ent of n1aterials evidently 

has been a very active process along the Andean front 

and in the high Andes during Pleistocene and Recent 

tiine. A contributing factor is the smniarid climate, 

which has inhibited the growth of protective forest on 

the slopes. 

Mudflows are a con1mon phenomenon on the western 

slopes of the Andes under present climatic conditions. 

Many n1udflows were produced on the upper Rio Maipo 

by an exceptionally heavy rainstonn on April 18, 1959. 

The canal that supplied a hydroelectric plant (fig. 

152.1) was destroyed in several places, and the river 

upstrean1 was dan1med by a Inudflow that descended 

a valley south of that of the Rio Y eso and formed an 

unsorted deposit 10 kin long and as Inuch as 100 n1 

thick. The resulting diainicton deposit, which contains 

blocks as large as 2 or 3 In in diameter (Pierre St. 

Amand, written communication, February 1963), 

closely resembles the diamictons of the Lorna de los 

Banos-Cerro Calan area in lithology and thickness. 

Mass moveinent presuinably produced the great 

tongue-shaped deposits, later modified by erosion, that 

extend fron1 L01na de los Banos to Cerro Calan. Other 

deposits are fan shaped, like the deposit east of Puente 

Alto. The practically continuous belt of dian1icton deposits along the Andean front between the mouths of 

th~ canyons of the Rios Mapocho and Maipo (fig. 152.2) 

evidently fonned by the coalescing of many mudflows. 

All degrees of transition between soupy mudflows 

and other types of n1ass movmnent can be recognized 

in central Chile, depending on steepness of the slope 

and proportion of water in the total mass as shown in 

the acc01npanying table. 

. The ~uthors agree with Borde (1955) that the pumice 

1n1med1ately west of Santiago was deposited as nludflows. Explosive eruptions of pmniceous ash are known 

to have taken place in Recent tilne in the Cordillera de 

los ~ndes. Heavy rains presmnably washed the easily 

erodible ash down the slopes and into the valleys, 

Types of rnass rnovernent in the vicinity of Santiago 

[Classification after Sharpe, 1938] 

Movement Earth or rock, dry or with Earth or rock, Chiefly water minor with water Type Rate amounts 

of water 

------------

Usually Creep Fluvial 

Flow imperceptible transportation 

Mudflow 

Perceptible 

Slip (land- to rapid Debris avalanche 

slide) 

carrying cobbles and boulders of the pre-existing colluvium with it. Lubricated by abundant water, some of 

the pmniceous Inixture evidently flowed out across the 

Santiago basin, lost monentun1, and stopped in the flat 

lowlands of the western part. Boulders were dropped 

enroute because of deceleration of the mudflow but ' 

some of the blocks were carried to the terminus of the 

flow. 

The present authors reject the supposed glacial origin 

of the relatively unsorted deposits of the Valle Central 

near Santiago for the following reasons: 

1. Similar dian1icton deposits have been forined by 

n1udflows in n1odern times in the saine general 

area. 

2. The bedrock underlying the deposits is deeply 

weathered; n10untain glaciers scour deeply and 

their till commonly rests on fresh rock. 

3. The fine matrix of the diamicton sedin1ents is yellowish brown due to limonitization; nowhere is it 

gray and unweathered like the rock flour of the 

known glacial deposits of the Rio Yeso 

Inoraine. The coarse material of the diamicton 

sediments shows no evidence of glacial transport. 

4. Neither U-shaped valleys nor cirques, which characterize glacial sculpture, occur in or near the 

Santiago area. 

5. At the latitude of Santiago, glacialinoraines can be 

traced only as far downslope as 1 ,600 m above 

sea level, more than 1,000 n1 higher than the 

valley floor at Santiago. 

REFERENCES 

Borde, Jean, 1955, Las depresiones tect6nicas del Maipo inferior-glaciaciones y cenizas volcanicas: Informaciones Geograficas 1, Santiago, Chile, Editorial Universitaria, p. 6-16. 

Brti.ggen, Juan, 1950, Fundamentos de la geologia de Chile: 

Instituto Geografico Militar, Santiago, 37 4 p. 

Castillo, Octavio, Falc6n, Eduardo, Doyel, W. W., and Valenzuela, Manuel, 1963, El agua subterranea de Santiago, Segundo 

informe: Instituto de Investigaci6nes Geol6gicas de Chile. 

[In press] 
Dl48 SEDIMENTATION 

Flint, R. F., Sanders, J. E., and Hodgen;, J., 1960a, Syrnmictite, 

a name for 110nsorted terrigenous sedimentary rocks that 

contain a wide range of particle sizes: Geol. Soc. America 

Bull., v. 71, p. 507-510. 

--- 1960b, Diamictite, a substitute term for synunictite: 

Geol. Soc. America Bull., v. 71, p. 1809-1810. 

Karzulovic, Juan, 1958, Sedimentos cuaternarios y aguas subterraneas en la Cuenca de Santiago: Universidad de Chile, 

Instituto de Geologia, publ. 10, 120 p. 

Mufioz Cristi, Jorge, 1960, Contribuci6n al conocimiento geologico de la Cordillera de la Costa de la zona central: Minerales, no. 69, p. 28-47. 

Sharpe, C. F. S., 1938, Landslides and related phenomena: 

New York, Columbia Univ. Press, 137 p. 
Article 153 

NEW OCCURRENCES OF THE RUGOSE CORAL RHIZOPHYLLUM 

IN NORTH AMERICA 

By WILLIAM A. OLIVER, JR., Washington, D.C. 

Abstract.-Rhizophyllurn is known from Middle or Upper 

Silurian rocks in Tennessee, Kentucky, Indiana, California, 

Nevada, Alaska, and Maine; from Lower Devonian rocks in 

Nevada; and from probable Middle Devonian rocks in Alaska. 

Four of these occurrences are first noted here, and specimens 

from Alaska, California, Nevada, and Maine are illustrated. 

The externally similar Calceola is not kno·wn to occur in North 

America. 

The genus Rhizophyllum has worldwide distribution 

in rocks of Late Silurian and Early Devonian age; 

it occurs less commonly in rocks of probable Middle 

Silurian (Wenlock) and early Middle Devonian 

(Eifelian) age. In North Americ~1, Rh1:zophyllum is 

now known fron1 coast to coast in rocks representing 

its full age range. 

Rhizophyllum is t1 near relative of the genus Calceola, 

with which it has often been confused because of 

external similarity. Calceola is apparently restricted 

to the Middle Devonian (Eifelian and Givetian) and 

i~ widely distributed on nwst continents but is not 

known from North America. Reported occurrences of 

Calceola in North America are nun1erous, but all so far 

have been based on the similar-looking Rhizophyllum. 

The purpose of this contribution is to illustrate and 

briefly describe speeimens of Rhizophyllum frorn Alaska, 

California, Nevada, and Maine, where no specin1ens 

have previously been described or in some cases even 

noted, and to point out that the "Calceola" from 

Alaska listed by Kindle (1907) and later by Kirk 

(in B uddington and Chapin, 1929) is actually a 

Rhizophyllum. 

Helen Duncan and C. W. Merria1n read the manuscript and made Inany helpful suggestions which were 

accepted in the final version; both provided specin1ens 

and information on occurrences. Thin sections were 

prepared by W. C. Pinckney, Jr.; photographs are by 

the author. 

PREVIOUSlY NOTED O·CCURRENCES 

Middle or Upper Silurian (Niagaran)-Tennessee, Kentucky, and Indiana 

Seven nominal species of Rhizophyllum (as Calceola) 

were described from the Brownsport Formation in 

Tennessee and the Louisville Limestone in Kentucky 

and southern Indiana by Roemer (1854), Safford (1860),· 

Lyon (1879), Hall (1882), and Davis (1887). Prior to 

this, Troost (1840) had described some Tennessee 

specimens as Calceola sandal1:na Lnmarek (type speeies 

of Calceola). Bassler (1915, p. 157-158) grouped all 

of these in three speeies which he referred to "Calceola 

(Rhizophyllum.)". No review of these has since been 

atte~npted, but additional specin1ens of two of the 

three species were illustrated or described by Foerste 

(1931) and by Amsden (1949). 

The Brownsport and Louisville Formations are of 

Niagaran (Wenlock or early Ludlow) age. 

Middle or Upper Silurian-Great Basin, California, and 

Nevada 

Stauffer (1930, p. 107, pl. 12, figs. 2-3) described 

and illustrated a single specimen of" Calceola sandalina 

Lamarck" from a section near Kearsarge, Calif. that 

he considered to be Devonian in age (1 930, p. 85-89). 

Subsequently, Waite (1953, p. 1521) reidentified the 

coral as Rhizophyllum and dated the beds as "late 

Niagaran or early Cayugan". 

Ross (1963) restudied the stratigraphy and named 

the formations involved. Merriam (in Ross, 1963, 

p. 83) listed Rhizophyllum among other corals fron1 

the Vaughan Gulch Lirnesto:Ife. Through the courtesy 

of C. W. Merriatn, I have been able to examine the 

speci1nen he studied, and a brief description is included 

under Rhizophyllum sp. D. Apparently Merriam's 

Rhizophyllum is frorn the sa1ne strntigraphic unit and 

locality as Stauffer's. 

ART. 153 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl49-D158. 1964. 

D149 
Dl50 PALEONTOLOGY 

Merriam (1963, p. 3 7) listed Rh1" zophyllum from the 

Silurian at Ikes Canyon, Toquima Range, N eY. This 

is the first published report of Rh1:zophyllum from 

Nevada. 

Middl1e(?} Devonian-southeastern Alaska 

Kindle (1907, p. 325-327) listed fossils frmn a lower 

as well as an upper diYision of the "Inassive limestone 

of Long Island, Kasaan Bay". Fron1 the upper 

division (Kindle collection 819) he listed Calceola ef. 

sandalina Lamarck with a few other corals and 52 

species of brachiopods, nwllusks, and arthropods. 

He regarded the upper fauna as 11iddle Devonian 

mage. 

Kirk (in Buddington and Chapin, 1929, p. 99-101) 

reexamined Kindle's collections and n1ade Ininor 

changes of identification, but repeated Calceola ef. 

sandalina. IGrk considered IGndle's upper and lower 

faunas to be the sa1ne and thought that they Inight be 

Early Devonian but were more likely Middle Devonian 

in age. 

The identification of Calceola ef. sandalina in both 

i·eports was based on a single individual which was not 

sectioned. It is described and illustrated here as 

Rhizophyllum sp. B. 

Corals in the IGndle collection have been sectioned 

and restudied, and are listed in the following table. 

New identifications are in the left column, while the 

names assigned to the san1e specin1ens by Kindle and 

later by Kirk are in the right column. 

This report 

Amphiphora sp. (stromatoporoid) 

Aulocystis sp. 

Favosites sp. 

Thamnopora sp. 

Eddastraea? sp. 

Rhizophyllum sp. B 

Pseudamplexus sp. cf. P. princeps Etheridge 

stauriid coral 

indeterminate cyathophylloid 

Kindle (1907) 

Syringopora sp. 

Cyathophyllum sp. 

Favosites cf. F. radiciformis 

Not identified 

Cyathophyllum sp. 

Calceola cf. C. sandalina 

Orthophyllum? sp. 

Cyathophyllum sp. 

Zaphrentis sp. · 

The coral assemblage is either Early or Middle 

Devonian in age. The genus Eddastraea and Pseudamplexus princeps are known from both Lower and 

Middle Devonian rocks of Australia (Hill, 1956, p. 306; 

Hill, 1950, p. 142). The stromatoporoid genus Amphiphora indicates a probable Middle Devonian age 

for the collection. 

Miscellaneous records 

North American examples of Rhizophyllum or 

"Calceola" have been formally described only from the 

Tennessee-Kentucky-Indiana area. Other listings and 

citations known to the author have been discussed in 

the preceding paragraphs but it is likely that some 

records have been missed since a comprehensive review 

of all literature dealing with the Silurian and Devonian 

of North America is impractical. Bassler (1950) 

presented extensive lists of corals by formation and 

geographic area but noted only the TennesseeKentucky-Indiana occurrences of "Calceola" in North 

America. 

Conrad (1840, 1841) in his preliminary reports on the 

paleontology of New York, twice Inentioned "Calceola". 

His Calceola plicata (Conrad 1840, p. 207) is a Platyceras 

(Hall, 1859, p. 334). His Calceola indenta (nomen 

nudum, Conrad, 1841, p. 37) was listed as a "univalve" 

along with gastropods, cephalopods, a conulariid, and 

a tentaculitid. It seen1s likely that the 1841 specimen 

was not a coral, but I have not found a later reference to 

it or attempted to trace the specimen. 

NEW OCCURRENCES 

Upper Silurian-southeastern Alaska 

USGS 1005-SD. Vermont marble prospect, south 

shore of Kosciusko Island, betwe~n Edna Bay and 

Holbrook. Collection of Edwin Kirk, 1917. 

Brachiopods from this locality were described by 

Kirk and Amsden (1952) with a brief summary of their 

occm·rence and stratigraphy. On the basis of the 

brachiopods, Kirk and Amsden (1952, p. 53) suggested 

an "Upper Silurian" age for the collection. 

In addition to the brachiopods, collection 1005 

includes tabulate and rugose corals and bryozoans. 

The following corals have been identified by the present 

author: Heliolites spp., Thamnopora sp., Cystiphyllum 

sp., Rhizophyllum sp. A, and Try plasma spp. These 

are suggestive of a Late Silurian age but are not so 

restricted. The identification of Rhizophyllum is based 

on five specimens that are described in a following 

section. 

Silurian(?}-northwestern California, 

USGS 5922-SD. Dislocated block of limestone, 

4 by 5 by 8 feet, on west bank of Trinity River in the 

center of sec. 2, T. 32 N., R. 10 W., Weaverville 

quadrangle, Trinity County. Collected by W. P. 

Irwin, 1961. 

A small collection of fossils, principally corals, was 

submitted by W. P. Irwin for examination and age 

determination. In a written comn1unication to Irwin, 

Helen Duncan (October, 19bl) listed "cystiphyllid 

corals (Rhizophyllum ?) " an1ong other forms and indicated that the age of the collection was Silurian or 

Devonian, more- likely Silurian. With the help of 

additional sections, the presence of several specimens 

of Rkizophyllum ·has been confirrned. These are 

described below as R. sp. C. In addition, the associated corals have been restudied by Miss Duncan and 

myself, and the following list is the result of our joint 

efforts: heliolitid coral fragrnents, Rhizophyllum sp. 
OLIVER D151 

C, Spongophylloides? sp., streptelasmatoid corals, 

Tryplasma? sp., Zelophyllum'? sp. The corals are 

badly recrystallized and somewhat distorted in shape 

due to metamorphisn1, and nwst of the identifications 

are queried. In spite of this, the apparent growth 

form of Rhizophyllum sp. C, the probable presence of 

Spongophylloides and Zelophyllum, and the internal 

nwrphology of the streptelasmatoids, are all strongly 

suggestive of Wenlock or Ludlow (~;[iddle or Late 

Silurian) age. 

The loose block fron1 which the corals were collected 

was in an area mapped as Bragdon Formation (in 

centralmetamorphie belt of Irwin, 1960, p. 18). The 

Bragdon is considered to be .N1ississippian in age but 

contains fragments of older fossiliferous limestones in 

son1e conglon1erate beds (Irwin, 1960, p. 18). 

Lower Devonian-Nevada 

USGS 6267-SD. Unnamed limestone unit forming 

a prmninent ledge on the east side of Coal Canyon, 

at an elevation of approximately 6,280 feet; SE7~ sec. 

17, T. 25 N., R. 49 E., northern Simpson Park Mountains, Horse Creek Valley 15-nlinute quadrangle, 

Eureka County, Nev.; collected by M. R. Murphy, 

1957 (J. G. Johnson, written comn1unication, 1963). 

The following eorals were present in a collection 

submitted for identifieation by J. G. Johnson, California Institute of Technology: Favosites sp., Endophyllum sp., 111ucophyllum sp., Papiliophyllum elegantv.lum Stumn1, Rhizophyllum sp. ef. R. enorme 

Etheridge, and cystiphylloid and chonophylloid corals. 

The identifieation of the Rhizophyllu.m is based on a 

single speeimen cleseri bed below. 

Papiliophyllum elegantulum suggests an Early Devonian age as the spPcies is most eommon in the 

Spirijer kobehana zone of ~ferriam (1940, p. 52-53). 

.N1erriam considered the zone to be Early Devonian, 

Oriskany or later, in age, and subsequent workers 

have agreed with this evaluation. Endophyllum is 

principally a Devonian coral, but species have been 

deseribed frmn the Upper Silurian of Europe (Prantl, 

1952). Mu.cophyllu.m is a Middle and Upper Silurian 

genus that has not been described or illustrated frmn 

younger rocks although there are incidental references 

to Devonian occurrences (for example, Wang, 1950, 

p. 228). The other listed corals could be either Silurian 

or Devonian. 

As a whole, the corals support an Early Devonian age. 

The presence of llfucophy!lum suggests that the fauna 

may represent an en,rly part of the early Devonian. 

According to Johnson (written communication, 1963), 

who is describing the braehiopods, the unnamed limestone frmn which the corals were colleeted is of Gedinnian (early Early Devonian) age and "is overlain by the 

Rabbit Hill Formation [Merrian1, 1963, p. 42-44] with 

an upper Gedinnian brachiopod fauna." Further, "the 

Rabbit Hill is in turn overlain by theN evada Formation 

with the zone of Acrospirifer kobehana in which Papiliophyllwn elegant-ul1t1n is typical. Accordingly, the oecurrence of P. elegantul1J.,m in the unna1ned lin1estone extends the range of the species eonsiderably downward". 

Upper Silurian-Maine 

USGS 6525-SD. On the boundary line between the 

Spider Lake and Telos Lake quadrangles, on the shore 

of Third Lake Mattagamon. Colleeted by Bradford A. 

Hall, University of Maine, 1961. 

A collection of eorals which was submitted for identification by B. A. Hall, includes the following: Cladopora? 

sp., ]avosites sp., Halysites sp., Heliolites sp., Syringapara sp., "Cystiphyllum" sp., Disphyllum sp., Entelophylhtm sp., Rhizophyllum sp. ef. R. gotlandicum 

(Romner), and Triplasma? sp. The eoral assemblage 

is definitely Silurian, either Wenloek or Ludlow in age. 

Brachiopods from the san1e collection have been studied 

by A. ~T. Boucot, California Institute of Technology; 

they indicate a Ludlow (Late Silurian) age (Boucot, 

written con1munication, 1962). 

The identification of Rhizophyllvm is based on a 

single speci1uen which is described and illustrated below. 

SYSTEMATIC DESCRIPTIONS 

Genus Rhizophyllum Lindstrom 

Rhizophyllum Lindstrom, 1866a, p. 287; 1866b, p. 411; 

1883, p. 22; Sherzer, 1891, p. 296; Hill, 1940, p. 394; 

Wang, 1948, p. 1, 3; Hill, 1956, p. 314. 

Calceola of 1nany authors (ineluding all known descriptions or citations of North An1erican specin1ens). 

Type species.-By rnonotypy, Calceola gotlandica 

Roen1er, 1856, p. 798; Silurian, Island of Gotland, 

Sweden. 

Diagnosis.-Rhizoph yll1Im includes calceoloid rugose 

corals with a semieircular operculum which articulates 

on the flat, eounter side of the eorallum. The interior is 

filled with arehed dissepirnents and tabellae arranged in 

an inverted eone pattern. Septa are acanthine or 

la1ninar and are lirnited to the flat side; the counter 

septum is comrnonly longer and thicker than the other 

septa. The wall on the flat side of the eorallun1 is 

formed by the fusion of the marginal edges of the septa; 

the curved part of the wall is apparently for1ned in the 

san1e way, although the septa do not project into the 

lumen even as septal ridges. The axis is straight or 

eurvecl. The corallmn in smne speeies was supported 

by raclieifonn proeesses. . 

Discuss·ion.-Lindstronl (1866a, b) established the 

genus Rhizophyllum to separate the "Calceola" with 
D152 PALEONTOLOGY 

cystiphylloid internal strueture from typical Calceola 

with stereoplasm-filled interiors. He discussed operculated corals at length (1866a, b, 1883) and placed all 

of the American "Calceola" in two speeies of Rhizophyllum. 

Bassler (1915) considered Rk1~zophyllum to be a 

subgenus of Calceola and was followed in this usage by 

Foerste (1931) and Shimer and Shrock (1944). Sherzer 

(1891) and Amsden (1949) are the only two American 

paleontologists who have published taxonomic papers 

using Rhizophyllwn as a genus; European and Australian workers have recognized the genus since its first 

description. 

Rhizophyllum ranges from the Middle Silurian 

(Wenlock) to the lower Middle Devonian (Eifelian). 

Speeies have been described from rocks of both Silurian 

and Devonian age in Europe, Asia, Australia, and 

North An1erica. Middle Devonian occurrenees are 

uneontmon but have been reported from the Eifelian 

of Mongolia (Spassky, 1960, p. 124_-12.5) as well as 

from Ala~ka (this article). Hill ·(1942, p. 13-16) 

reported Rh1:zophyllum and Calceola frmn the same 

limestone in Queensland, but she concluded that the 

age was latest Early Devonian. 

Descriptions.-The following descriptions are of 

speeimens rather than species, 1 being based on 5 

speeimens, 1 on 10 specimens, and the other 4 on one 

specimen each. Two of the "speeies" are eompared 

with previously named spceies that are morphologieally 

similar; at least one "species" is new but fonnal 

description must await the acquisition of n1ore n1aterial. 

The dimensions of all speeimens described are given 

in millimeters. Length was measured in a straight line 

from the counter side of the calice margin to the apex; 

since 1nost specimens are incomplete at one or both 

ends, the figures represent minimum length. The 

diameters were measured at the calice margin or at the 

uppermost con1plete growth line. 

Rhizophyllum sp. A 

Figure 153.1a-e, 153.2a-j, 153.3b 

Description.-Five specimens of solitary Rhizophyllum, lacking radiciform processes probably represent 

a new species. Two cycles of growth lines are pro min en t 

on the exteriors; where the outer surface is worn, the 

traces of the septa can be seen on both fiat and convex 

sides. 

T n transverse section the counter septun1 is two or 

more times the length of the other septa and is thickened 

to a spindle shape. The septmn is formed of calcite 

fibers radiating upward and from the center of the 

spindle within an outer sheath of lainellar tissue. 

This gives an elongate rosette appearance in transverse 

section and a fan pattern in longitudinal section. 

Other septa are numerous and closely spaced; they are 

enveloped in lamellar tissue but the microstructure of 

their inner portions has not been observed. 

Tn longitudinal section, the dissepiments are very 

steep and elongate near the curved, cardinal side but 

almost horizontal near the counter margin. From the 

counter side, the dissepiments steepen toward the 

eceentric axis about which the tabellae are large and 

horizontal. 

11easurements are as follows: 

Specimen (USNAf No.) 

121200 ________ _ 

1 2120 L _______ _ 121202 ________ _ 

121203 _________ _ 121204 ________ _ 

Length (mm) 

14 

19 

26 

24 

Diameter (mm) 

J..fajor Afinor 

12. 7 

17. 2 

27. 2 

21. 8 

18. 5 

7. 1 

9. 6 

11.8 

11.0 

10. 1 

Discussion.-R. sp. A is characterized by its inflated 

counter septum. A similar structure is seen in R. 

yotlandicum of Rozkowska (1946, p. 145-146, 154-155, 

pl. 5, figs. 4a-b) from the Silurian of Podolia. The 

Podolian material differs in having comparatively few, 

but large dissepiments and tabellae. R. gotlandic11m 

of Soshkina (1937, p. 82, pl. 19, fig. 1-2) fron1 the 

Upper Silurian of the Urals, lacks the prominent 

counter septmn but is similar in other respects. Typical R. gotlandic11,m (Lindstrom, 1866a, p. 287, pl. 30, 

fig. 10-15, pl. 31, fig. 1-8; 1883, p. 23, pl. 3, fig. 1-12, 

18, pl. 4, fig. 7) from the Middle and Upper Silurian of 

Gotland, has a less prominent counter septmn and 

reduced (acanthine?) lateral septa; in addition, typical 

R. gotlandicum has numerous supporting radiciform 

processes. 

~faterial.-Five specimens from the Upper Silurian 

of Alaska (USGS 1005-SD; see stratigraphic discussion). Illustrated specimens, USNM 121200 to 121203. 

Unillustrated specimen, USNM 121204. 

Rhizophyllum sp. B 

Figure 153.1/,g 

Description.-A single specimen of solitary Rhizophyllum frmn the Devonian of Alaska, has a eurved, conical 

shape and lacks radiciform processes; dimensions are: 

length, 15+ nun; and diameter, 11.4 by 20.7 Inm. The 

exterior is 1narked by growth rugae. In a transverse 

section, 26 discrete septa are present along 15 mm of 

the straight margin; the septa are vertically discontinuous and may be acanthine. The presumed eounter 

septum is only slightly longer than the other sept,a. 

Dissepiments are small and elongate; large tabellae surround the eceentric axis. A neanie section indicates 

that the dissepimentarium was relatively narrow in 

en,rly growth stages, but ephebic and neanic sections 

are similar in other respects. 
OLIVER D153 

c 

b 

d 

f 

e g 

FIGURE 153.1.-Rhizophyllwn sp. A and sp. B. The counter septum is toward the top of the plate in the transverse thin sections 

and to the left in the longitudinal thin section. All specimens X 4. a-e, Rhizophyllum sp. A; ephebic sections; ?-- b, USNM 

121203; c-d, USXM 121202; e, USXM 121201 ; Upper Siluri an , Alaska. f-g, R. sp. B; neanic and ephebic sectwn; US:'ifM 

140899; Middle(?) Devonian, Alaska. 

Discus&ion.-'l'h e one a ,·ailable specimen is morphologically similar to H. robustum Shearsby (1906 , p. 548 , 

pl. 26, fi g. 1-6; Hill, Hl40, p. 396 , pl. 11 , fig. lla-b) 

from the Silurian of .'\ E'\Y So uth ·wales. R. robnsl11:m 

differs in being more erect and in ha,·ing finer tabellae 

and orcnsional radiciform processes. 

i\1aterial.-One specimen from the .\fiddle'? De,·oni1tn 

of Alaska (Kindle 897; see stratigrap hic discussion). 

Illustrated specimen , USNM 140899; collected by 

E. M. Kindle, 1905. 

Rhizophyllum sp. C 

F igure 153.4 a- e 

Description.- 'l'en or more specimens of a small 

Hhizophyllum ar e known from trans,'erse sections only. 

The specimens were found in 2 groups, 1 with 3 or more 

indi,·iduals and the other with 7 or more; the presence 

of numerous r adieifo nn processes and the spatial 

relationships of t he indi,·iduals suggest that they 

occurred in clumps or small colo nies. Incli,·idual diameters range from 2.5 by 3.0 mm to approximately 5 by 
D154 PALEONTOLOGY 

a b c 

d e 

f g h ~ J 

FIGURE 153.2.- Rhizophyllum sp. A; exterior views; Upper Silurian, Alaska. a-c, cardinal, counter, and side views; USNM 

121201. d- e, counter and side views; USN M 121202. f- g, cardinal and side views; USNM 121203. h-j, cardinal, counter, 

and side views; USNM 121200. All specimens X 1?~. 

a b 

FIGURE 153.3.-a, Rhizophyllum sp. cf. R. enorme; detail of figure 153.5b; USNM 121205; Lower Devonian, Nevada. b, R. sp. A; 

detail of figu,re 153.1e; USNM 121201; Upper Silurian, Alaska. Transverse thin sections, X 10. 
OLIVER D155 

c 

a 

d 

b e 

FIGURE 153.4.-Rhizophyllum sp. C; USNM 121344 ; Silurian(?), northwestern California. a-b, Sections through group or clump 

of specimens, X 3; immature and mature transverse sections of individuals and sections of radieiform processes and probable 

opercula are shown. c, Detail of b, X 10; transverse sections t hrough neanic portion of two corallites and partial section of ephebic portion of another. d, Detail of b, X 10; transverse section of neanic portion of a corallite. e, Detail of a, X 10; 

transverse section of early ephebic portion of a corallite. 

9 mm (3 specimens). All specimens have a relatively 

thick wall (0.3-0.5 mm) with a prominent counter septum on the straight side. In smaller sections (neanic 

and brepbic?; diameter less than 3.5 by 5.0 mm) other 

septa form the wall but do not project into the lumen; 

one or two dissepiments are present in some of the 

sections. In the larger sections (ephebic) the lumen is 

filled with dissepimental plates and . septa project 

slightly from the straight margin. The calice is relatively deep and V -shaped. Several cresent-shaped 

objects in the thin sections may represent the opercula 

of this species. 

Discussion.- In apparent growth form and general 

morphology, Rhizophyllum sp. C is similar to R. elongatum Lindstrom (1883, pl. 2) from the Middle or 

Upper Silurian of Gotland, Sweden, and to R. attenuatum (Lyon) (Lindstrom, 1883, pl. 3, fig. 17) from the 

Middle or Upper Silurian, Louisville Limestone in 

716-626 0-64--11 

Kentucky. R. sp. C is closer to R. attenuatum in size 

and number of radiciform processes, but adequate 

comparison is not possible because of the nature of the 

California specimens. R. sp. C may be allied to one 

of the two clump-forming species or may represent a 

third species but is, in either case, suggestive of Silurian 

age. 

Material. - Two groups totaling ten or more specimens from the Middle or Upper Silurian of northwestern 

California (USGS 5922-SD; see stratigraphic discussion). Illustrated group, USNM 121344; unillustrated 

group, USNM 121345. 

Rhizophyllum sp. D 

I?] Calceola sandalina Stauffer, 1930, p. 107, pl. 12, 

figures 2- 3 (not Linnaeus) 

Description.- A single specimen of solitary Rhizophyllum from the Silurian of eastern California, has a 
D156 PALEONTOLOGY 

curved conical shape and apparently lacks radiciform 

processes; dimensions are: length, 43+ mm; and diameters, 15+ by 35 mm. The specimen is poorly preserved with beekitized exterior and normally silicified 

interior. The counter septum projects 2 to 3 mm in 

large sections; other septa are half as long, discrete, 

probably acanthine, and limited to the straight side. 

Dissepiments are steeply inclined on both sides of the 

eccentrically located axial zone of tabellae; dissepiments and tabellae are of approximately the same 

SlZe. 

Discussion.- The specimen is too poorly preserved 

for comparison with other species of the genus, but it 

is probably conspecific with Stauffer's specimen (see 

stratigraphic discussion). 

Material.-·One specimen from the Middle or Upper 

Silurian of California (USGS 6839-SD). Unillustrated 

specimen, USNM 121346. 

Rhizophyllum sp. cf. R. enorme Etheridge 

Figures 153.3a, 153.5a,b 

Rhizophyllum enorme Etheridge, 1903, p. 232- 233, pl. 

47; Hill and Jones, 1940, p. 182, pl. 2, fig. 3-4. 

Description.-A single specimen with curved axis is 

20+ mm in length, with diameters of 15.8 and 27.5 

mm; the exterior is poorly preserved but there is no 

evidence of radiciform processes. In transverse section, 28? septa are present along 14 mm of the straight 

margin. The counter septum is twice the length of the 

adjacent septa and is thickened by a sheath of lamellar 

tissue. 

c 

a 

b 

d 

A longitudinal section in the cardinal-counter plane 

shows rather coarse tabellae at the eccentric axis with 

smaller, elongate, steeply inclined dissepiments on 

either side. The structure of the septa cannot be 

determined from available sections but they seem to 

be laminar. 

Discussion.- The described specimen is similar to 

R. enorme as illustrated by Hill and Jones (from the 

Lower Devonian of New South Wales) in internal 

structure but is much smaller and has relatively coarser 

tabellae and dissepiments. 

Material.- One specimen from the Lower Devonian 

of Nevada (USGS 6267-SD; see discussion). Illustrated specimen, USNM 121205. 

Rhizophyllum sp. cf. R. gotlandicum !Roemer) 

Figures 153.5 c-e 

Calceola gotlandica Roemer, 1856, p. 798. 

Rhizophyllum gotlandicum (Roemer), Lindstrom, 1866a, 

p. 287, pl. 30, fig. 10- 15, pl. 31, fig. 1-8; 1866b, p. 

406-411, pl. 14, fig. 8-18; 1883, p. 23, pl. 3, fig. 1-12, 

18, pl. 4, fig. 7. 

Description.-One specimen of Rhizophyllum from the 

Upper Silurian of Maine is incomplete but represents 

a solitary, erect form with radiciform processes in the 

apical region; dimensions are: length, 45 + mm; and 

diameters, 26 by 16 mm. The appearance of the external surface is not known. In transverse section the 

counter septum is relatively long and inflated; there 

is a suggestion of a radiating structure and there is a 

e 

FIGURE 153.5.-Rhizophyllum sp. cf. R. enorme and R. sp. cf. R. gotlandicum. The counter septum is toward the top of the plate 

in the transverse thin sections and to the left in the longitudinal thin section. All specimens X 4. a-b, Rhizophyllum 

sp. cf. R. enorme; ephebic longitudinal and transverse sections; USNM 121205; Lower Devonian, Nevada. c-e1 R. sp. cf. 

R. gotlandicum; brephic?, neanic, and ephebic transverse sections; circular and oval bodies above and to the nght of the 

specimen in e are sections of radiciform processes; USNM 121206; Upper Silurian Maine. 
OLIVER D157 

sheath of lamellar tissue. Other septa are short and 

acanthine. 

The dissepiments are elongate and steeply inclined; 

the axial tabellae are more globose but not much 

larger than the dissepiments. Both dissepiments and 

tabellae are thickened with excess stereome deposits. 

A neanic section shows a few tabellae with an incomplete marginal row of dissepiments and a short, stumpy 

counter septum; no other septa are developed. An 

even earlier section (brephic?) shows only a bulge in 

the straight side representing the counter septum and 

a single tabella. 

Discussion.--The Maine specimen is re1narkably 

similar to specimens illustrated by Lindstro1n (1883). 

A weathered longitudinal section is like Lindstrom's 

figure 6 and the neanic section (my fig. 153.5d) is close 

to his figure 5. Lindstrom did not publish an illustration of an ephebic transverse section but his calice 

illustrations (1866b, pl. 14, fig. 8-11, 14) suggest that 

the septal development is similar to that described here 

for the Maine specimen. 

Material.-One individual from the Upper Silurian 

of Maine (USGS 6525-SD; see stratigraphic discussion). 

Illustrated specimen, USNM 121206. Collected by 

Bradford A. Hall, 1961. · 

REFERENCES 

Amsden, T. W., 1949, Stratigraphy- and paleontology of the 

Brownsport Formation (Silurian) of western Tennessee: 

Peabody Mus. Nat. Hist., Yale Univ., Bull. 5, 138 p., 34 pl. 

Bassler, R. S., 1915, Bibliographic index of American Ordovician 

and Silurian fossils, v. 1 and 2: Smithsonian Inst., U.S. 

National Mus. Bull. 92, 1521 p. 

--- 1950, Faunal lists and descriptions of Paleozoic corals: 

Geol. Soc. America Mem. 44, 315 p. 

Buddington, A. F., and Chapin, Theodore, 1929, Geology and 

mineral deposits of southeastern Alaska: U.S. Geol. Survey 

Bull. 800, 398 p. 

Conrad, T. A., 1840, Third annual report on the palaeontological 

department of the Survey: New York Geol. Survey Ann. 

Rept. 4, p. 199-207. 

--- 1841, Fifth Annual report on the paleontology of the 

State of New York: New York Geol. Survey Ann. Rept. 5, 

p. 25-57. 

Davis, W. J., 1887, Kentucky fossil corals, pt. 2: Kentucky 

Geol. Survey, 139 plates and expl. 

Etheridge, Robert, Jr., 1903, An unusually large form of Rhizophyllu.rn lately discovered in New South Wales: Recs. Geol. 

Survey New South Wales, v. 7, p. 232-233, pl. 47. 

Foerste, A. F., 1931, The Silurian fauna: Kentucky Geol. Survey, 

ser. 6, Paleontology of Kentucky, p. 167-214. 

Hall, James, 1859, Descriptions and figures of the organic remains 

of the Lower Helderberg group and the Oriskany sandstone: 

New York Geol. Survey, Paleontology of New York, v. 3, 

text, 532 p. 

--- 1882, Fossil corals of the Niagara and Upper Helderberg 

groups: New York State Mus., Ann. Rept. 35, advanced 

Rheets, 59 p. 

Hill, Dorothy, 1940, The Silurian Rugosa of the Yass-Bowning 

district, N .S. W.: Linnean Soc. New South Wales Proc., 

v. 65, p. 388-420, pl. 11-13. 

--- 1942, The Lower Devonian rugose corals from the Mt. 

Etna limestone, Qld.: Royal Soc. Queensland Proc., v. 54, 

p. 13-22, pl. 1. 

--- 1950, Middle Devonian corals from the Buchan district 

Victoria: Royal Soc. Victoria Proc., v. 62, p. 137-164; 

pl. 5-9. 

--- 1956, Rugosa, in Moore, R. C., ed., Treatise on invertebrate paleontology, pt. F. Coelenterata: Geol. Soc. America 

and Kansas Univ. Press, Lawrence, Kans., p. 233-324. 

Hill, Dorothy, and Jones, 0. A., 1940, The corals of the Garra 

beds, Molong district, New South Wales: Royal Soc. New 

South Wales Jour. and Proc., v. 74, p. 175-208. 

Irwin, W. P., 1960, Geo ogic reconnaissance of the northern 

Coast Ranges and Klamath Mountains, California: California Div. Mines Bull. 179, 80 p. 

Kindle, E. M., 1907, Notes on the Paleozoic faunas and stratigraphy of southeastern Alaska: Jour. Geology, v. 15, 

p. 314-337. 

Kirk, Edwin, and Amsden, T. W., 1952. Upper Silurian brachiopods from southeastern Alaska: U.S. Geol. Survey Prof. 

Paper 233-C, p. 53-66, pl. 7-10. 

Lindstrom, Gustav, 1866a, N agra iakttagelser ofver zoantharia 

rugosa: Ofvers. Kongl. Vetensk.-Akad. Forhandl., v. 22, 

p. 271-294, pl. 30-31. 

---1866b, Some observations on the Zoantharia Rugosa: 

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--·- 1883, Om de Palaeozoiska formationernas Operkelbarande 

Koraller: Bihang Kongl. Svensk. Vetensk.-Akad. Handl., 

v. 7, 112 p., 9 pl. 

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Sci. Philadelphia Proc., p. 43-46. 

Merriam, C. W., 1940, Devonian stratigraphy and paleontology 

of the Roberts Mountains region, Nevada: Geol. Soc. 

America Spec. Paper. 25, 114 p., 16 pl. 

--- 1963, Paleozoic rocks of Antelope Valley, Eureka and 

Nye Counties, Nevada: U.S. Geol. Survey Prof. Paper 423, 

67 p. 

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Haime and Spongophyllu.rn Edwards and Haime in the 

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Bronn, H. G., Lethaea Geognostica, 3d ed.: Stuttgart, 

788 p. -

--- 1856, Bericht von einer geologisch-palaontologischen 

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p. 794-815. 

Ross, D. C., 1963, New Cambrian, Ordovician, and Silurian 

formations in the Independence quadrangle, In yo County, 

California: Art. 21 in U.S. Geol. Survey, Prof. Paper 475-B, 

p. B74-B85. 

Rozkowska, Maria, 1946, The Silurian rugose corals from 

Podolia: Polskiego Towarzystwa Geologicznego, Rocznik, 

T. 14, p. 139-157, pl. 4-5. 

Safford, J. M., 1860, On the species of Calceola found in Tennessee: Am. Jour. Sci., ser. 2, v. 29, p. 248-249. 

Shearsby, A. J., 1906, Operculate corals from New South Wales: 

Geol. Mag., new ser., Decade 5, v. 3, p. 547-552, pl. 26. 
D158 PALEONTOLOGY 

Sherzer, W. H., 1891, A chart of the rugose corals: Am. Geologist, 

v. 7, p. 273-301. 

Shimer, H. W., and Shrock, R. R., 1944, Index fossils of North 

America: New York, John Wiley and Sons, 837 p. 

Soshkina, E. D., 1937, [Corals of the upper Silurian and lower 

Devonian of the eastern and western slopes of the Urals]: 

USSR, Acad. Sci., Inst. Paleozool., Tr., v. 6, pt. 4, 112 p., 

21 p. 

Spassky, N. Ya., 1960, [The Devonian. rugose corals of the 

southern Altai and adjoining territories]: Leningrad, Gorny 

Inst. Records, v. 37, p. 108-131, pl. 1-10. 

Stauffer, C. R., 1930, The Devonian of California: California 

Univ. Pubs. in Geol. Sci., v. 19, no. 4, p. 81-118, pl. 10-14. 

Troost, Gerard, 1840, Organic remains discovered in the State of 

Tennessee: Fifth Geol. Rept. to the 23rd General Assembly 

of Tennessee, p. 45-75. 

Waite, R. H., 1953, Age of the "Devonian" of the Kearsarge 

area, California [abs.]: Geol. Soc. America Bull., v. 12, 

p. 1521. 

Wang, H. C., 1948, Note on a remarkable Rhizophyllum species 

from the middle Silurian of H ueitze, northern Yunnan: 

Palaeont. Soc. China, Palaeont. N ovitates, no. 2, 4 p. 

--- 1950, A revision of the Zoantharia Rugosa in the light of 

their minute skeletal structures: Royal Soc. London, Philos. 

Trans., ser. B, no. 611, v. 234, p. 175-246, pl. 1-9. 
Article 154 

GLACIAL CHRONOLOGY OF ULLSFJORD, NORTHERN NORWAY 

By G. WILLIAM HOLMES and BJORN G. ANDERSEN, 

Beltsville, Md., and University of Oslo 

Work done in cooperation with the Air Force Cambridge Research Laboratories 

Abstract.-Quaternary features of Ullsfjord record Late Glacial 

fluctuations of the Fennoscandian ice sheet and of local alpine 

glaciers. The earliest known advance left erratics and subdued 

moraines near the coast. The subsequent Breidvika advance 

formed lateral moraines which continue into the sea as sharp 

submarine end moraines. Shortly thereafter the Skardmunken 

ad vance also resulted in moraines with both terrestrial and marine facies. Radiocarbon dates of marine shells place the 

Skardmunken maximum between 11,500 and 10,390 years B.P. 

(late Aller~d and Younger Dryas time). A nearly continuous 

beach level, probably the "main beach level" of northern Norway, 

is cut in bedrock and unconsolidated materials from the outer 

coast to the top of the deltaic sediments of the Skardmunken 

moraine. Shortly after the Skardmunken advance, the Stordal 

ad vance left small moraines and deltas at a level slightly below 

the projection of the "main beach level." Lastly, cirque 

glaciers deposited steep unweathered moraines in historic time. 

Ullsfjord is a deep, narrow trough with a total length 

of 50 kilometers, a maximum width of 5 kilometers, 

and a maximum relief of nearly 1, 700 meters. In 

places the sides are so steep that no surficial deposits 

remain. The fiord was eroded along the contact 

between gabbroic rocks that make up the high, 

spectacular Lyngen Alps, and schistose rocks that form 

the slightly lower alpine peaks to the west. Scores of 

mountain glaciers originated in these mountains during 

the Pleistocene, and many cirques are still filled with 

ice. Narrow structural valleys connect Ullsfjord with 

fiords to the east, west, and south. These troughs 

were access routes for outlet glaciers of the Fennoscandian ice sheet that invaded the fiord in Pleistocene time. 

The bottom of the fiord is very irregular, as a result of 

bedrock relief and glacial deposition. Depths range 

from about 11 meters over submarine moraines, to 268 

meters in the outer fiord. 

Although Ullsfjord lies well above the Arctic Circle, 

its climate is humid temperate, very similar to that of 

southern Alaska (Haurwitz and Austin, 1944). The 

nearest weather station, at TromsSiS, 25 kilometers to 

the west, has a mean annual temperature of 2.3 °C and 

a mean annual precipitation of 940 mm (Hansen, 1960, 

p. 46-47). 

The glacial record in illlsfjord is typical of northern 

Norway. Our studies show that the glacial sequence 

consists of (1) an unnamed early glaciation, (2) the 

Breidvika advance, (3) the Skardmunken advance, (4) 

the Stordal advance, and (5) a Recent advance (see 

accompanying table and fig. 154.1). One important 

ba3is for this chronology is the prominent elevated 

shoreline (informally referred to here as the "main 

beach level") that was formed at the time of the 

Glacial chronology of Ullsfiord 

Glaciation Age Correlation Basis for correlation 

Recent 18th Century. "Little Ice Age." Near or in contact with existing glaciers. 

Slightly younger Possibly Preboreal. Moraines are behind 

Stordal than Skard- and (or) at lower 

munken. levels than Skardmunken ice margins. 

11,500-10,390 years. Equivalent to Radiocarbon dates are Troms¢-Lyngen approximately the 

Skardmunken advance of north- same as the Troms¢- em Norway. Lyngen moraines. 

Moraines graded to "main beach level." 

Slightly older Possibly equivalent Moraine position is a than Skard- to Skarpnes short distance beBreidvika munken. advance of north- yond Skardmunken ern Norway. moraines. Moraines truncated by "main beach level." 

Somewhat older Possibly equivalent Drift occPrs seaward 

than Breidvika. to one or more of Breidvika 

Early older advances in moraines. 

southern Norway. 

ART. 154 IN U.S. GEOL SURVEY PROF. PAPER 475-D, PAGES Dl59-Dl63. J.964. 

D159 
Dl60 

0 2 3 

~ --J 

~ (_J.rollvan n 

<~~ 

""".. . .. 

~M 

~ .· . 

~ /.!) 

..... ~~ -:··. ( 

4 MILES 

0 2 3 4 5KILOMETERS 

19°30' 

GLACIAL GEOLOGY 

rr .. 

. 

(fJ 

z 

\ lJ.J , 

~""' ff 

69° 30' 

._J 

20°00' 

FIGURE 154.1.-Glacial and marine deposits near Ullsfjord, northern Norway. A-A', line of profile shown in figure 154.2, large 

dots in Ullsfjord are projections of points on the shores where the "main beach level" was measured. 
HOLMES AND ANDERSEN D161 

Recent moraine 

Stordal moraine 

Skardmunken 

moraine 

Breidvika 

moraine 

Early moraine 

EXPLANATION 

Alpine moraine, 

undifferentiated 

Glaciofluvial 

deposits 

Main beach level 

Inferred ice margin 

X T-333 

Radiocarbon sample 

locality 

Fwu RE 154.1.-Continued 

Skardmunken glaciation, between 11,500 and 10,390 

years B.P., according to radiocarbon dates. Some 

moraines in the mountains are not clearly related to 

datable features and are designated only as alpine 

moraines, undifferentiated. 

SHORELINES 

Elevated, tilted Pleistocene shorelines in northern 

Norway were first recognized by Bravais in 1838 

(11arthinussen, 1960, p. 416) in Altafjord, about 100 

kilometers east of lTilsfjord. Their discovery created 

a basis for the theory of isostatic recovery of glaciated 

terrain. These shorelines were formed at times when 

sea level was nearly constant, which in late Pleistoc-ene 

time probably corresponded to intervals when the 

sea and the land were rising at the same rate. 

The most distinct shoreline in illlsfjord is informally 

named the "main beach level." It is nearly continuous 

from the outer fiord, where it is about 35 meters above 

sea level, to a few kilometers south of Skardmunken 

where it is about 70 meters above sea level. Th~ "main beach level" is cut in bedrock, older moraines, 

marine till, and gravel deposits. It is about the same 

age as the Skardmunken moraine, for (1) it is graded 

to the top of that moraine at about the level that separates the terrestrial and marine portions; (2) it is graded 

to extensive Skardmunken outwash depm~its west of 

Breidvikq,; and (3) it does not extend far beyond the 

Skardmunken moraine, indicating that ice of this advance filled the inner fiord while the shoreline was being 

cut. 

Shorelines related to other glaciations are limited in 

extent, and are marked primarily by deltas. Sea level 

was probably changing too rapidly during these intervals to create a persistent shoreline. A distinct 

lower shoreline formed after the "main beach level " ' but it apparently is not related to a glacial advance 

and merely represents a second period. of sea-level 

stability. 

GLACIATION 

Early glaciation 

The oldest recorded glaciation left scattered erratics, 

patches of till, a few indistinct moraines, and drainage 

channels in the northern part of the fiord district. The 

most distinct feature is a broad moraine that dams 

Trollvann in the northwestern part of the mS1pped 

area. The ice sheet that deposited this drift probably 

extended north of the present shoreline and covered 

the continental shelf. The age of this glaciation is not 

known, but the drift occupies a position analogous to 

that of the Lista substage, of Oldest Dryas age (more 

than 13,000 years old), or the Spangereid substage 

(dated about 13,000 years B.P.) (Andersen, report in 

preparation). 

Breidvika glaciation 

The oldest glaciation in illlsfjord which left large 

well-preserved moraines is here named informally the 

Breidvika advance, for the cove on the west side of the 

fiord. The largest Fennoscandian outlet glacier moved 

northward and terminated in the sea just south of 

Breidvika, leaving a prominent lateral moraine on the 

east side of the fiord and a small segment on the steeper 

west side. Profiles of the lateral moraine on the east 

side of the fiord (fig. 154.2) show that the ice sloped 

steeply toward its terminus in the fiord. 

Echo soundings show a very sharp double ridge 

(fig. 154.2) on the fiord bottom with a relief of approximately 38 meters. A western arm of this glacier pushed 

westward out of the fiord, turned north, entered a 

parallel valley, and deposited a prominent terrestrial 

end moraine. 

A 

North 

METERS 

600 

0 5 10 15 KILOMETERS 

A' 

South 

FIGURE 154.2.-Profiles of prominent moraines, shorelines, and 

submarine ridges in the main part of Ullsfjord. Large dots are projections of points on the shores where the "main beach 

level" was measured. Location of profile shown in figure 

154.1. 
D162 GLACIAL GEOLOGY 

A second large glacier moved westward from Lyngenfjord (east of the mapped area) and the Lyngen Alps 

down the east arn1 of the fiord, leaving a smaller pair of 

lateral ridges and a submarine ridge with a maximum 

relief of approximately 45 meters (fig. 154.1). The 

echo profile of this ridge shows n1any sinaller ridges on 

the east (upglacier) side, but not a sharp reverse slope 

in that direction. 

The age of the Breidvika glaciation is not known. 

Its moraines appear to be only a little older than the 

succeeding (Skard1nunken) glaciation, and related 

shorelines are only 2 to 4 meters above the "main beach 

level," which is roughly the same age as the Skardmunken glaciation. Also, the Breid vika n1oraines 

occupy positions analogous to the Skarpnes n1oraine 

near Tron1s0 to the west, which is regarded to be 

somewhat older than Younger Dryas (Andersen, report 

in preparation), that is, the age of the Skardmunken 

glaciation. 

Skardmunken gl1aciation 

The best preserved moraine in illlsfjord is here named 

inforn1ally for the settlen1ent on the tenninal section. 

This part of the moraine was deposited in the sea and 

consists of stratified drift displaying foreset bedding 

which was smoothly planed by subsequent wave action. 

The submarine part is a smooth ridge crossing the fiord; 

it is being reworked by strong tidal currents. 

The terminal section merges with a large terrestrial 

lateral moraine on the east side of the fiord. This 

lateral Inoraine, which in places branches into several 

ridges, extends southward for a distance of about 9 

kilmneters. The glacier that formed this n1oraine also 

pushed into the valley joining the fiord on the west. 

However, ice of this glaciation did not leave a clear 

record in the east arrn of the fiord. A terrestrial 

moraine of this glaciation was also deposited in the 

broad trough west of Breid vika by ice which moved 

fron1 adjoining Balsfjord. Glaciofluvial deposits spread 

down the valley fron1 this moraine and merged with the 

"main beach level" along the shores of Ullsfjord. 

A mini1num and probably close radiocarbon date 

of 10,390 years B.P. (T-333, Trondheim Radiological 

Dating Laboratory, 1962) for the Skardmunken moraine was obtained frOln nwllusk shells (~1aconta 

calcarea(?), Saxicava arctica(?), and Afya truncata(?)). 

The shells were collected frmn varved north-dipping 

sandy marine clay on the proximal side of the end 

moraine, lying about 30 to 40 meters above sea level 

and overlying coarse stratified south-dipping drift. 

The date probably corresponds to the beginning of the 

retreat of the Skardn1unken glacier. 

Shells of Portlandia arctica and Macoma calcarea 

(T-110) collected near the top of pebbly glaciomarine 

clay beds which underlie outwash of Skardmunken age 

in the valley west of Breidvika (fig. 154.1) were dated 

at 11,500±400 years B.P. The lithology and date of 

the shell-bearing Inaterial suggest it was deposited in 

a glacial environment i1 nmediately before the maA.imum 

of t,he Skard1nunken advance. 

Marine till on the east side of Ullsfjord opposite 

Breidvika, although not demonstrably related to the 

Skardn1unken moraine, is son1ewhat younger than the 

glaeiomarine clay west of Breidvika. Shells in the 

former (Saxicava arctica, Macoma calcarea, and Mya 

truncata, T-232) have a radiocarbon date of 11,090± 

190 years B.P. On the basis of the first two dates, 

the Skardmunken advance oecurred between about 

11,500 and 10,390 years B.P., or at approximately the 

san1e time as the Tron1s0-Lyngen maxin1un1 in adjoining fiords (Andersen, report in preparation). 

These dates span late Aller0d and Younger Dryas time 

in southern Scandinavia (Flint, 1957, p. 397). 

Stordal glaciation 

Distinct end moraines occur behind Skardmunken 

moraines in several valleys, in son1e places in groups 

of two or nwre; none are associated with present 

glaeiers. These minor readvances are here na1ned 

informally for Stordal, a tributary valley on the west 

side of the inner fiord. Here is a small but distinct 

end moraine, at an elevation of about 70 meters, well 

below the projeeted level of the Skardmunken glacier 

and at about the same level as the oldest elevated 

shoreline in the inner part of the fiord. Similar n1oraines 

oecur behind terrace-dated Skardmunken n1oraines 

in the northeastern corner of the mapped area. The 

outwash delta from the type Stordal moraine, graded 

to the oldest elevated marine terrace in the inner part 

of the fiord, is only about 5 n1eters below the "n1ain 

beaeh level." Thus this advanee oeeurred shortly 

after the Skardmunken glaeiation and is possibly 

Pre-Boreal in age. 

Recent glaciation 

Nearly all the existing glaeiers are fronted by sn1all, 

steep, bouldery, unweathered nwraines. These are 

similar to modern moraines found in most alpine environments throughout the Northern Hemisphere. 

Although it is generally held that Recent moraines are 

not neeessarily of precisely the same age, those in 

northern Seandinavia probably formed in the 18th 

century, as suggested by historieal reeords in Norway 

(Liest0l, 1960, p. 487). 
HOLMES AND ANDERSEN D163 

REFERENCES 

Flint, R. F., 1957, Glacial and Pleistocene geology: New York, 

John Wiley and Sons, 553 p. 

Hansen, S. W., 1960, The Climate, in Vorren, 0., ed., Norway 

north of 65: Oslo, Oslo University Press, 271 p. 

Haurwitz, B., and Austin, J. M., 1944, Climatology: New York, 

McGraw-Hill, 410 p. 

Liest!'Sl, 0., 1960, Glaciers of the present day, in Holtedahl, 0., 

Geology of Norway: Norges Geol. Undersokelse, no. 208, 

540 p. 

Marthinussen, M., 1960, Coast and fjord area of Finnmark, in 

Holtedahl, 0., Geology of Norway: Norges Geol. Undersokelse, no. 208, 540 p. 
Article 155 

EFFLUENT COLLECTOR FOR GAS CHROMATOGRAPHY 

By DONALD F. GOERLITZ and WILLIAM L. LAMAR, 

Menlo Park, Calif. 

Abstract.- The authors have designed a convenient effluent 

collector for gas chromatographic samples. This collector 

eliminates contamination of one component by another as well 

as contamination from other sources. The collector provides 

an individually complete assembly for each component, it pockets 

and magnifies the sample, and it has its own heat sink. Importantly, the sample is collected close to the end of the analytical 

column. 

Gas chromatography is being used increasingly for 

the analysis of volatile organic compounds and of those 

substances that can be made volatile. However, the 

collection of pure fractions of gas chromatographic 

samples from analytical columns presents a problem, 

particularly where several close-boiling components 

are involved. Contamination of one component by 

another can occur readily in the effluent line and at 

the exit port. The effluent line can also serve as a 

condensation chamber in which the column substrate 

may accumulate. 

Although several types of collectors are described in 

the literature (Grasselli and Snavely, 1962; Hajra and 

Radin, 1962; Haslam and others, 1961; and Lesser, 

1959), all the collectors examined used the existing 

effluent line and exit port. Some collectors provided 

excellent trapping, but all were deficient in preventing 

contamination of one component by another. 

To avoid contamination of gas chromatographic 

samples, the samples must be collected at or near the 

the end of the analytical column and not at a common 

exit port supplied by a common effluent line. The 

collector should pocket the sample so that it can be 

readily withdrawn by a hypodermic needle. The 

collector should be relatively inexpensive, easily 

handled, individually cooled, and conveniently sealed 

from atmospheric moisture and coolant-bath vapor 

before and after collection. 

An especially designed collector that embodies these 

principles is shown in figure 155.1. The admission 

FIGURE 155.1.-Effiuent collector. 

tube is 18-gage stainless-steel hypodermic tubing; it 

has a 17 -degree bent point on one end and a square cut 

on the other. The part of the admission tube that 

extends beyond the rubber septum should be just less 

than the length of the common effluent line, so that 

when the tube is inserted, the septum will seal the exit 

port. Before and after use, the end of the admission 

tube can be sealed with an inverted septum if desired. 

ART. 155 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D164-Dl66. 1964. 

Dl64 
GOERLITZ AND LAMAR D165 

The carrier gas is vented through a hypodermic needle 

that is inserted in the discharge arm of the collector. 

The silicone-rubber septums are the standard halfdrilled type that fit 6-n1m ID tubing. The coolantbath holder for each collector consists of a snap-on-cap 

polyethylene container 1~ inches in dian1eter by 2X 

inches high. Two holes and a connecting slit were 

made in each cap. An 0-ring cut from rubber tubing 

positions the collector in the coolant-bath holder. 

The admission tube 1nay be placed in the horizontal 

or vertical ar1n of the collector, depending upon the 

access to the detector vent. In order to reach the 

detector vent with an admission tube, the gas chromatograph must have a sufficiently straight conunon 

effluent line. In some gas chron1atographs the end of 

the column is at the bottmn of the instrmnent and the 

.common effluent line is arranged so that it is not possible 

to reach the detector vent with an admission tube. 

However, these gas ehron1atographs ean be modified 

so that the cornponents can be collected fron1 the bottmn 

of the instrument. 

For example, a Perkin-Elmer Model 154-D gas 

chromatograph was modified by drilling a %-inch hole 

in the bottom of the oven cabinet. The hole was alined 

with the exit "tee" of the detector so that a 4-inch 

length of straight 7~-inch stainless-steel tubing attached 

to the exit "tee" just protruded outside the oven chamber. A 1%-inch length of %-inch copper tubing was 

inserted and crimped to line the hole and keep the 

insulation in place. The exit end of the 7~-inch stainlesssteel tube was fashioned so that the entry was conical, 

to facilitate insertion of the admission tube. The inside 

of the exit tube was polished to a sn10oth finish with 

emery powder on a cotton-swab stiek. The upstream 

end of the tube was swaged to the detector-outlet "tee." 

Access to the new exit port was made by supporting 

the gas chrmnatograph cabinet on a frame. The 

original effluent line was removed. 

EFFLUENT COLLECTION PROCEDURE 

The eollection apparatus is assernbled and a suitable 

coolant is placed into the coolant receptacle. A sample 

is injected into the gas chron1atograph, and just before 

the desired component emerges, the admission tube of 

the collector is started into the exit port of the chromatograph. At the time the recorder indicates the emergence of the component, the admission tube is inserted 

all the way to the rubber septum and held firmly in 

place. The uncontaminated component in the carrier 

gas passes through the individual admission tube 

and is condensed in the poeket of the glass collector. 

During waiting periods, the collectors and bath holders 

may be kept in a flat pan of crushed ice or on a slab of 

dry ice. 

EXPERIMENTAL RESULTS 

Methyl caproate was selected to demonstrate the 

suitability of the apparatus for collecting components 

with comparatively low boiling points, and the 

din1ethyl esters of fumaric and malonic acids were used 

to show the effectiveness of the apparatus for the separate collection of two partially overlapping compounds. 

A 20-microliter sample containing 0.00023 g of 

methyl caproate in absolute methanol was injected 

into the gas chron1atograph. Collection of the sample 

was begun when the recorder pen left the base line and 

ended when the pen returned to the line. The collected 

sample was transferred from the collector to a microcavity cell (0.2-0.3 J.Ll minimum volume) with a total 

of 5 J,tl of carbon disulfide by using a microliter syringe . 

Infrared analysis was made after the solvent was 

evaporated down to about 1 J.Ll under the gentle heat 

of an infrared heat lamp. Evaporation was halted by 

closing the cell with a drop of mercury. Another 

infrared scan was made after replacing the carbon 

disulfide with carbon tetrachloride by dilution and 

evaporation. A X 4 infrared beam condenser was used 

for these analyses. 

A 20-J.tl aliquot of a solution containing 0.0124 g of 

dimethyl malonate and 0.0119 g of dimethyl fumarate 

in 1.00 ml of absolute methanol was injected into the 

gas chromatograph. As shown in figure 155.2 the 

resulting chromatograph is a good example of closely 

eluting, partially overlapping compounds. The collections were timed to eliminate the unseparated part of 

the elution. The overlapping part, comprising 20 

percent of the dimethyl malonate and 40 percent of 

the dimethyl fumarate, was discarded by venting. 

The infrared spectrum of each of these components was 

obtained as described in the preceding paragraph 

except that only carbon tetrachloride was used with 

dimethyl fumarate. In addition, the dimethyl fumarate was collected for infrared analysis by the potassium 

bromide micropellet technique. 

RESULTS AND DISCUSSION 

Each component eluted by the gas chromatograph 

is collected close to the end of the analytical column 

in an individually complete assembly. An excellent 

infrared spectrum for methyl caproate was obtained 

from a single collection of an injection of only 0.00023 g 

of the ester. This demonstrated the application of this 

apparatus for the collection of components with cmnparatively low boiling points. 
D166 ANALYTICAL TECHNIQUES 

L&J 

en 

z 

~ en 

L&J 

0::: 

~ 

TIME 

FIGURE 155.2.-Chromatograph of overlapping compounds. 

A separate collection of closely eluting and partially 

overlapping components was equally successful as 

demonstrated by the injection of a sample containing 

dimethyl malonate and dimethyl_ fumarate. Two 

injections were required because it was necessary to 

vent the overlapping part of the elution. Each of the 

2 injections contained 0.00025 g of dimethyl malonate 

and 0.00024 g of dimethyl fumarate. From these 

injections, each component was collected separately 

and placed in a microca vity cell for infrared analysis. 

No contamination of one of these esters by the other 

could be observed in the infrared spectra. 

To test another handling technique, two collections 

of dimethyl fumarate were pressed in a micropellet 

of potassium bromide. Again, no contamination of 

this ester was observed in the infrared spectrum that 

was obtained with a X 4 beam condenser and X 5 scale 

expansion. 

An important feature of the apparatus described here 

is the completely individual system for the collection 

of each component very near the end of the column. 

Thus, contamination of one component by another as 

well as contamination from condensation of column 

substrate can be eliminated. This collector has several 

other distinct advantages. For example, the condensing surface can be easily washed with a small amount 

of solvent, and the thickened glass section magnifies and 

pockets the collected material. The collector can be 

completely sealed during cool-down or waiting periods, 

thus avoiding contamination by atmospheric moisture 

and cold-bath solvents. The collector is always maintained in its own heat sink that will not warm up before 

the collection is completed. 

This collector also enhances a collection and reinj ection technique developed by the authors. With this 

technique the components are individually collected 

and reinjected into a different gas chromatographic 

column to obtain two characteristic retention volumes 

for each component. This provides a salient advantage 

in the identification and confirmation of the organic 

components in a sample. 

REFERENCES 

Grasselli, J. G., and Snavely, M. K., 1962, Analysis of organic 

reaction products by combined infrared-gas chromatography 

techniques: Appl. Spectroscopy, v. 16, p. 190-194. 

Hajra, A. K., and Radin,. N. S., 1962, Collection of gas-liquid 

chromatographic effluents: Lipid Research Jour., v. 3, 

p. 131-134. 

Haslam, J., Jeffs, A. R., and Willis, H. A., 1961, Applications of 

gas-liquid chromatography: Analyst, v. 86, p. 44-53. 

Lesser, J. M., 1959, Device for isolation of components separated 

by gas chromatography: Anal. Chemistry, v. 31, p. 484. 
Article 156 

USE OF SODIUM-SENSITIVE GLASS ELECTRODES 

FOR SOLUBILITY DETERMINATIONS 

By A. H. TRUESDELL and C. L. CHRIST, Washington, D.C. 

Abstract.-A method applicable to concentrated solutions is 

described for converting activities, measured by cation-sensitive 

glass electrodes, to concentrations. The usual difficulty oi 

assigning accurate values to activity coefficients is avoided by 

the use of a dilution technique. The method is applied to the 

determinations of the solubilities of borax, ulexite, and sodium 

chloride. 

Following the initial discovery by Eisenman and 

others (1957) of practical sodium- and potassiumsensitive glasses, Garrels and others (1962) developed 

glasses specifically sensitive to divalent cations (Ca +z, 

Mg+2, Ba+2, Sr+2). An electrode fashioned from one of 

these glasses offers a convenient and rapid means of 

directly measuring cationic activity (conventionally 

defined), or of indirectly measuring concentration in 

aqueous solution. 

Although only the sodium-sensitive electrode was 

used to measure the solubilities of sodiun1 salts, the 

same procedure could be used for any salt containing 

a cation for which an electrode having the proper 

response is available, for example, potassium or ammonium salts, or the alkaline-earth salts. Similarly, 

the solubility of a given salt in the presence of any 

ionic medium not affording a com1non cation could be 

determined. 

In general, the conversion of a measured ionic activity 

(at) to a concentration (ct) requires the use of an accurate value of t~e appropriate ionic-activity coefficient 

('Yt), where Ct=ad'Yt· The activity coefficient depends 

upon the total ionic strength of the solution. In 

saturated solutions of many readily soluble salts, such 

as the sodium borates, the concentration, and hence 

the ionic strength (1) is high, and the cation is complexed 

in an unknown way. As a result, there is no way to 

assign accurate values of cation-activity coefficients. 

We have evolved a technique that bypasses this 

difficulty. This technique involves making cationactivity measurements on successive ten-fold dilutions 

of a saturated solution of the salt whose solubility is to 

be measured. When the solution becomes very dilute, 

this fact is revealed by its electrochemical behavior. 

Because the solution is very dilute and any complexing 

will be vanishingly small, the cation-activity coefficient 

can be calculated from the Debye-Hiickel equation. 

The concentration of this dilute solution can be calculated, and because the number of dilutions is known, 

the original concentration can then be established. 

Using a sodium-sensitive electrode we have determined the solubilities of borax (at 25°C and 40°C), 

ulexite (at 25°C, incongruent solution), and sodium 

chloride (at 25°C). The values determined by the 

present method are in excellent agreement with those 

determined by conventional methods, as shown 1n 

table 156.1. 

PROCEDURE AND THEORETICAL BASIS 

The sodium-sensitive electrode used in this work was 

the Electronics Instruments Laboratory model N a 

GNA 23. This electrode was paired with a saturatedKCl calomel reference electrode (wick type), and the 

developed potential was measured with a vibrating 

capacitor high-impedance electrometer, and a potentiometer. Potential measurements were made on solutions maintained at 25°C±0.05°C in a constanttemperature bath and stirred with a magnetic stirrer. 

The voltage measurements were generally accurate to 

±0.1 mV, with an occasional reading doubtful to ±0.2 

m V. Because the electrode is also sensitive to hydrogen 

ions, pH must be maintained ?: 7; at sodium-ion 

concentrations below about 10-4 m (molal), the hydrogen-ion response of the electrode introduces error. The 

usual precautions were maintained with regard to 

adequate electrical shielding in working with the high 

resistance glass electrode (Mattock, 1961). The electrode was conditioned by soaking for several days in 

0.1 m N aCl solution. 

ART. 156 IN U.S. GEOL. SURVEY PROF. PAPER 475--D, PAGES D167-D170. 1964. 

D167 
D168 ANALYTICAL TECHNIQUES 

TABLE 156.1.-Values of solu.bilities of sodium chloride, borax, and 

the sodium-ion concentration resulting from the incongruent 

solution of ulexite, determined by N a-sensitive electrode, compared 

with literature values 1 

This study Literature 

f2 M a I Weight Weight I Reference 

percentage 4 percentage 4 

------ 5. 40 ------ 5. 41 

4. 62 ------ - -

Sodium chloride, 25°C 

26. 4 

26. 4 

27.0 

26. 48 Gillespie (1928, p. 105). 

________ Density=1.1978 g/cma 

( Gillspie, 1928, p. 105). 

4. 53 26.5 

0. 151 -------- 3.04 3. 06 Menzel and Schulz (1940). 

0. 150 -------- 3.03 -------- ------------------------- 0. 152 -------- 3. 05 3. 13 Blasdale and Slansky 

(1939). 

0. 308 -------- 6. 20 6.00 Menzel and Schulz (1940), 

and Blasdale and Siansky. (1939). 

Ulexite (as NaCaB50g), 25°C 

------1 0. 01871 5 0. 491--------l------------------------- ------ 0. 0186 0. 49 -------- -------------------------

1 The accuracy of the experimental results is best judged by internal consistency, and by comparison with the literature values. The limiting precision is determined 

by the ±0.1 mVreproducibility of the voltage measurements; an error ofO.l mV leads to an error of about 0.4 pe.rcent in the solubility determination. 2 Weight dilution method. a Volume dilution method. 4 Grams of solute per 100 g of solution. • Incongruent solution; only sodium-ion concentration measured. 

The potential of the cell, E, is given by a Nernst-type 

equation 

E (volts)=E' +(RTf CJ)ln[Na+I], (1) 

where R, T, and CJ have their usual significance. 

E' is a constant voltage and includes any liquid junction 

potential. E' has the value E at unit activity of 

sodium ion, [N a+1]= 1. At 25°0, equation 1 becomes 

E=E' +0.0592 log [Na+1]. (2) 

In practice, E' is not evaluated, but rather the difference 

in potential of the cell is determined with the unknown 

solution and with a solution whose sodium ion activity 

is known. This procedure minimizes the uncertainty 

due to the liquid-junction potential. From equation 2 

we obtain the following operational equation: 

or 

(4) 

where ;r=unknown and s=standard. Equation 4 is of 

exactly the same form as the one on which the measurement of pH is based (Bates, 1954). 

The N a G N A 23 electrode was checked against a 

series of standard N aOl solutions (1 m to 10-4 m), and 

found to have exactly the theoretical slope predicted 

by equation 4, namely 

dE8/dpN a 8 =0.0592 volts. 

The sodium molality of each standard solution was 

converted to sodium activity by the relation 

(5) 

where the activity coefficient 'YNa+I was obtained by 

the "ineaP-salt" method (Garrels, 1960), in which 

/'Na+l =')'2 ±NaCI/'Y ±KCI 

for ionic strength 1~0.1, and by the Debye-Hiickel 

equation for I<0.1 (Klotz, 1950, p. 329). Values of 

'Y±Kcl and 'Y±Naci were taken from Lewis and Randall 

(rev. ed., 1961, p. 643), and Robinson and Stokes 

(1959, p. 492), respectively. 

The standard solutipn used in a given determination 

was either 0.1 m NaOl, with 'YNa+I=0.79 (mean-salt), 

pNa=l.102; or 0.01 m NaOl with 'YNa+I=0.902 (DebyeHiickel), pN a=2.045, or both. It was found that the 

solubility determinations were completely consistent 

with both of these single-ion activity coefficients, 

which attests to the validity of their value in practical 

problems. 

Saturated solutions of the salts were prepared by 

shaking the solutions in contact with excess solids, 

over a period of about 3 weeks. One method of doing 

this was to impart mechanically a rocking motion to 

a 125-ml rubber-stoppered flask containing solution 

plus solid, in a constant-temperature bath maintained 

at ± 1°0. In a second method the solution plus solids, 

contained in 125-ml Teflon bottles, were immersed in 

a constant-temperature bath held at ±0.1 °0; the bottles were removed twice daily and vigorously shaken 

by hand. In the case of the mechanically shaken system, the grain size of the excess N aCl was sufficiently 

large that the supernatant liquid could be sampled 

directly with a pipet; this was not true with the less 

soluble borax and ulexite. In those experiments in 

which the bottles were shaken by hand all the solids 

remained finely crystalline, and the liquid was drawn 

by suction through a coarse-frit filter in order to remove 

small crystals. 

As previously stated, the voltage measurements were 

all made at 25 °0. For the 25 °0 solubility measurements, the potential of the cell was measured with the 
TRUESDELL AND CHRIST D169 

saturated solution as the test solution. Following this, 

in one set of experiments, a 10-ml portion of the saturated solution was delivered to a calibrated 100-ml 

volumetric flask by means of a calibrated pipet, and 

diluted to 100 ml; the potential of this solution was 

then measured. This procedure was repeated stepwise 

to and including the 1:1,000 dilution. 

The volume-dilution procedure leads to concentrations in units of molarity (M, moles of solute per 1,000 

ml solution). In a second set of experiments a weightdilution technique was employed; this technique leads 

to concentrations in units of formality (j, moles of 

solute per 1,000 solution). Whether volume dilution 

or weight dilution was used in a particular determination 

is indicated in table 156.1. 

There is an internal formal inconsistency in the calculations because the values of the activity coefficients 

employed are based on the molal scale ( m, moles of 

solute per 1,000 g solvent). However, for 'YNa+I values 

from the mean-salt method, and especially for 'YNa+I 

values calculated by the Debye-Huckel method for the 

very dilute range, any changes resulting from a change 

in scale from molal to molar or formal would be outside 

the limits of error of the method. 

As the test solution becomes progressively dilute, 

with fewer sodium ions available to ensure stable equilibrium between the electrode surface and the solution, 

fluctuations in the voltage readings become larger. At 

the same time, the relative activity of hydrogen ions 

increases and the electrode begins to respond to these 

ions. For these reasons a decision must be made concerning the best dilution stage at which to calculate 

the concentration. This stage will depend upon the 

solubility of the salt, and will reveal itself through the 

magnitude of the measured activity. In general, it 

is best to use the highest concentration that shows the 

Nernst-type behavior of equation 2. In this study 

we choose the 1:1,000 dilution (of the saturated solution) of N aCl, the 1: 100 dilution of borax, and the 

1:10 dilution of ulexite. 

The tabulated values given by Klotz (1950, p. 332) 

for the Debye-Huckel equation 

Az2Il 

1+BaJi' -log 'Yi 

for 10&at=4, and for 25°C, were used to construct a plot of 

'YNa+I vs.l; values of 'YNa+I were read from this plot for the 

diluted solutions. The ionic strength, I= l4~mtz~, a 

must be evaluated differently for each substance, 

depending upon the charges of the anions assumed to be 

present to balance the Na+1

• For NaCl, I=mNa+I; for 

borax, in the absence of specific knowledge, it was 

assumed that each N a+1 is balanced by a singly charged 

borate anion (Ingri and others, 1957), so that here also 

I =mNa+I. illexite, N aCaB50 9·8H20, in excess, in 

equilibrium with water at 25°C, yields a Na-rich 

borate solution and inyoite, Ca2B6011 -13H20 (Kurnakova and Nikolaev, 1948). Thus, the measurement 

here yields the sodium-ion concentration in equilibrium 

with excess ulexite and in the presence of inyoite. 

From the data of Kurnakova and Nikolaev (1948) on 

the Ca0-B20 3-H20 system, the solution in equilibrium 

with inyoite at 25°C is 1.32X10-2 M with respect to 

Ca+2• We assume as a rough guess that the presence 

of the common singly charged borate ion depresses 

this value to one-half in the case of the solution in 

equilibrium with both ulexite and inyoite, and calculate 

the ionic strength on this basis. 

In all cases, in calculating I it is first assumed that 

the measured activity is equal to ·the molality, and a 

provisional 'Yt found. This provisional 'Yt is divided 

into the activity to find the next approximation 

to the molality and a new 'Yt is looked up, following which 

a new molality is calculated (see table 156.2); in this 

work, only two stages of iteration were necessary. 

Fortunately, 'Yt changes relatively slowly as a function 

of I over the dilute-solution region, so that no appreciable error results in the calculated concentration 

in those cases where I cannot be evaluated precisely. 

TABLE 156.2.-Determination of solubility of NaCl at 25° C by 

volume-dilution method 

Ex-E8 =0.0592 (pNas-pNax) 

E 8=41.0 mV for 0.1 m NaCl; pNa 8 =1.102 1 

E 3 =-14.9 mV for 0.01 m NaCl; pNa 8 =2.045 1 

Dilution stage 

Sat. sol. 

1:10 

1:100 

1:1,000 

Ex (mV) 

168. 2 

84. 3 

27.0 

-30.0 

pNax (0.1 m std.) 

-1.047 

0. 371 

1. 338 

2. 301 

For the 1:1,000 dilution 

N - - 30.0- 4l.O 1.102= -2.301 

-p ax- 59.2 

pNaz=2.301 1 

or 

-pNax= 305~~ 14 9 -2.045= -2.300 

pNax=2.300 1 

[Na+1]=5.00X10-3 ; 1'1=0.927; C1=(5.00X10-3)/(0.927) =5.39 x 10-3; 1'2=0.925; c2= (5.oox 10-3)/(0.925) =5.40X 10-3; M = 5.40 

1 Third place after the decimal uncertain. 

RESULTS AND SUMMARY 

The final solubility values determined by the electrode method are listed in table 156.1. To show how 

the experimental procedure leads to a solubility value, 
D170 ANALYTICAL TECHNIQUES 

the details of one determination on N aCl are given 

in sumn1ary fonn in table 156.2. 

The investigation reported upon here was an exploratory one only, and had as its sole purpose the 

testing of the principle of the method; no real attempt 

\Vas 1nade to achieve the best possible accuracy. It 

seen1s clear that this dilution technique can be used to 

measure solubilities with a fair degree of confidence, 

even with simple techniques. To 1neasure accurately 

the solubility of a substance at an elevated ten1perature, 

a better technique than that employed by us of separating solids from liquid would be needed. 

REFERENCES 

Bates, R. G., 1954, Electrometric pH determinations: New 

York, John Wiley and Sons, Inc., 331 p. 

Blasdale, W. C., and Slansky, C. M., 1939, The solubility curves 

of boric acid and the borates of sodium: Jour. Am. Chern. 

Soc., v. 61, p. 917-920. 

Eisenman, George, Rudin, D. 0., and Casby, J. U., 1957, 

Glass electrode for measuring sodium ion: Science, v. 126, 

p. 831-834. 

Garrels, R. M., 1960, Mineral equilibria: New York, Harper and 

Brothers, 254 p. 

Garrels, R. M., Sato, M., Thompson, M. E., and Truesdell, 

A. H., 1962, Glass electrodes sensitive to divalent cations: 

Science, v. 135, p. 1045-1048. 

Gillespie, L. J., ed., 1928, Density (specific gravity) and thermal 

expansion (under atmospheric pressure) of aqueous solutions 

of inorganic substance and of strong electrolytes, in Washburn, E. W., and others, eds., International critical tables of 

numerical data, physics, chemistry and technoiogy: New 

York, McGraw-Hill Book Co., Inc., v. 3, p. 51-111. 

Ingri, Nils, Langerstrom, G., Frydman, M., and Sil1en, L. G., 

1957, Equilibrium studies of polyanions. II. Polyborates 

in NaC104 medium: Acta Chern. Scand., v. 11, p. 1034-1058. 

Klotz, I. M., 1950, Chemical thermodynamics: Englewood 

Cliffs, N.J., Prentice-Hall, Inc., 369 p. 

Kurnakova, A. G., and Nikolaev, A. V., 1948, The solubility 

isotherm of the system Na20-CaO-B203-H20 at 25°: Akad. 

Nauk. SSSR Izvestria, Otd. Khim. Nauk, no. 1, p. 377-382. 

[in Russian] 

Lewis, G. N., and Randall, Merle, 1961, Thermodynamics, 

revised by K. S. Pitzer and L. Brewer: New York, McGrawHill Book Co., 723 p. 

Mattock, G., 1961, pH measurement and titration: London, 

Heywood and Co., Ltd., 406 p. 

Menzel, Heinrich, and Schulz, Hans, 1940, Zur Kenntnis der 

BorsatTren und borsauren Alkalisalze. X. Der Kernit 

(Rasorit) Na2B40 7.4H20: Zeitschr. anorg. allg. Chern., v. 

245, p. 157-220. 

Robinson, R. A., and Stokes, R. H., 1959, Electrolyte solutions: 

London, Butterworths Sci. Pubs. 
Article 157 

SEMI MICRO X-RAY FLUORESCENCE ANALYSIS OF TEKTITES 

USING 50-MILLIGRAM SAMPLES 

By HARRY j. ROSE, JR., FRANK CUTTITT A, MAXWELL K. CARRON, and 

ROBENA BROWN, Washington, D.C. 

Abstract.-Semimicro determinations of the major constituents 

(Si02, AbOa, total iron, K20, CaO, Ti02, and MnO) of tektites 

were made by X-ray fluorescence spectroscopy using 50-milligram 

samples. The X-ray analytical data are comparable to determinations obtained by conventional chemical techniques. 

X-ray fluorescence spectroscopy has been applied to 

the determination of the major constituents in relatively large samples of materials of geologic interest 

(Rose and others, 1962, 1963). This technique can also 

be used for the semimicro analysis of rare mineral 

specimens or of materials of astrogeologic interest 

where only very small quantities ( < 100 mg) of material 

are available. The analysis of the light elements in 

tektites has been made possible by advances both in 

instr-umentation and in techniques of sample preparation. It is well known that the intensity of the fluorescent radiation decreases sharply with a decrease in 

the atomic number (Z) of the element being analyzed. 

This decrease can be attributed to many factors such 

as diminishing fluorescence yield and absorption of the 

fluorescent radiation by air, by the sample, by the 

diffracting crystal, and by the window of the detector. 

Additionally, as the radiation becomes softer with decreasing atomic number, the depth from which the 

excited radiation emerges becomes shallower and shallower. Thus the effective radiation involves only 

those atoms at or near the surface of the sample a 

situation that demands precise and reproducible sam~le preparation. 

The elimination of air from the spectrometer by 

either evacuation of the chamber or by flushing the 

chamber with helium provides the first necessary step 

to detecting the radiation. The use of supported thinfilm windows (Balis and others, 1 962) on the detectors 

has resulted in higher intensities by reducing absorption 

by the window and has extended the useful range of 

the technique to wavelengths beyond 10 angstroms. 

Accurate quantitative determination of the light 

elements depeads primarily on sample preparation and 

ultimately on the surface of the specimen submitted 

to the X-ray beam. As mentioned above, the particles 

at or near the surface provide the effective signal for 

analysis. Infinite depth, the point beyond which no 

increase in signal can be observed regardless of increase 

in sample thickness, is reached for CaO in less than 100 

microns and for MgO in less than 50J.t. It is evident, 

therefore, that the surface of the prepared specimen 

must be homogeneous and a true representation of all 

the layers beneath it. 

Fusion of the sample in a mixture of Li2B407 eliminates many of the problems inherent in the X-ray 

fluorescence analysis of powdered samples (Andermann, 

1961; Rose and others, 1962), especially those related 

to particle size and crystal structure. The presence of 

a strongly absorbing element minimizes absorption 

differences among samples resulting from variations in 

matrix, thus obviating the need for absorptio.p. corrections or for standards matching the composition of the 

material under study. La203 was chosen because of its 

high absorption for the light elements. 

The method described initially (Rose and others, 

1962) required a 250-milligram sample. Although this 

amount is considerably less than the quantity used for 

routine chemical analysis, there are instances when 

smaller quantities must be analyzed. The effort here 

was directed toward reducing the sample size to 50 

mg by determining the minimum layer of fused sample 

necessary to maintain the desired signal for the elements 

being analyzed. 

ART. 157 IN U.S. GEOL. SURVEY PROF. PAPER 475-D. PAGES D171-D173. 1964. 

716-626 0-64-12 D171 
D172 ANALYTICAL TECHNIQUES 

X-RAY FLUORE·SCENCE METHOD 

The fusion mixture consists of 50 mg of sample, 50 

mg La203, and 340 mg Li2B407 • The components are 

mixed in a boron carbide mortar, transferred to a 

graphite crucible having a cone-shaped internal base, 

and fused at 1,100°C for 10 minutes. The bead is 

allowed to cool in the graphite crucible. Cooling may 

be accomplished more rapidly by placing the crucible 

on a large copper plate, which dissipates the heat more 

readily. Sufficient boric acid is added to bring the 

weight to 460 mg. The boric acid compensates for 

any losses during ignition and acts as a binder during 

preparation of the pellet. The glass bead is then ground. 

The grinding vial consists of a lucite cylinder provided 

with two caps containing tungsten carbide inserts for 

covering both ends of the cylinder. The bead, which 

must be crushed before grinding, is placed cone side up 

in the grinding vial with one of the caps and inserts in 

place. A %-inch drive pin punch is placed down the 

cylinder on top of the bead and is then tapped with a 

hammer. The weighed boric acid is added to the vial 

along with a .%-inch tungsten carbide ball, and the upper 

cap is placed on the cylinder. The sample is then 

ground on a mixer grinder for 10 minutes, which 

reduces the sample to about 325 mesh. The ground 

powder is then pressed into a pellet 1 inch in diameter. 

For additional strength the pellet is prepared as a 

double layer, using boric acid as backing (Rose and 

Flanagan, 1962). It is essential that the sample layer 

be spread uniformly on the surface of the boric acid 

before final pressure is applied. To obtain maximum 

intensity for Si and AI, pressure in excess of 50,000 

pounds per square inch must be used. The preparation 

of samples must be done consistently with attention to 

all details to insure the best results. 

A single-channel spectrometer was used for this 

study. The types of crystals, wavelengths, and 

detectors are given in table 157.1. Because the 

fluorescent radiation of elements Z ~ 22 is absorbed by 

air, the spectrometer chamber is flushed with helium 

for the determination of these elements. It is generally 

necessary to flush the chamber for about 1 minute 

between sample changes to allow the system to come to 

equilibrium. 

Granite G--1, diabase W-1, and an equal mixture of 

the granite and diabase are used as reference standards. 

N fttional Bureau of Standards standard samples and 

other samples analyzed at the U.S. Geological Survey 

serve as additional reference materials to extend the 

range of the elements being determined. Several 

reference standards may be mi..xed in varying proportions to· provide desired points on the calibration 

curve. 

The method has been used recently to analyze six 

samples of tektites from Java supplied by E. C. T. 

Chao. The results of both chemical and X-ray 

fluorescence determinations are given in table 157.2. 

TABLE 157.1.-Summary of crystals, detectors, and wavelengths 

Element , K (A) Crustal Detector or counter 1 Path 

SL ______ _ 7. 125 Gypsum ____ _ 

AL _ ----- 8. 337 ____ do _____ _ Fe ______ _ 1. 936 LiF 2 ______ _ 

Ca __ --- __ 3. 358 Eddt 3 _____ _ K _______ _ 3. 741 Gypsum ____ _ Mn _____ _ 2. 102 LiF 2 _______ _ 

TL _____ _ 2. 7 48 LiF 2 ______ _ 

ProportionaL____ He ____ do__________ He 

Scintillation______ Air 

ProportionaL____ He ____ do__________ He 

Scintillation_ _ _ _ _ Air _ ___ do__________ He 

1 Pulse-height analysis, channel width 12V, base level 4.5 V. 2 Lithium fluoride. 3 Ethylene · diamine ditartrate substituted for gypsum in 

samples with high ~0 content. 

CHf:M;ICAL ANAlYTICAL METHODS 

Six javanites were carefully selected from a collection 

of about 80 specimens to represent the range of the 

indices of refraction and specific gravities of the Java 

tektite collection. The specin1ens are listed in table 

157.2 in order of increasing index of refraction. The 

tektites were analyzed for Si02, Al203, total iron as 

TABLE 157.2.-Comparison of chemical and X-ray analyses of 6 tektites from Java 

[Index of refraction (N) in sodium light; X-ray determination made on a single pellet] 

JS-JS JS-9 JS-5 JS-6 JS-3 JS-11 

Chem. X-rau Chem. X-rau Chem. X-ray Chem. X-ray Chem. X-ray Chem. X-ray 

Si02 __________________________ 74. 2 74.4 73.4 73.5 73. 8 74. 2 74. 4 72. 7 72. 3 72. 3 72. 5 72. 3 

Ab03--- ----------------------- 11. 1 11. 6 11.4 11. 3 11. 3 11. 5 11. 2 11. 3 11. 3 11. 3 11.4 11. 6 F~Of _________________________ 5. 67 5. 70 5. 63 5. 65 5. 28 5. 35 5. 52 5. 66 6. 14 6. 28 6. 17 6. 22 CaO __________________________ 2. 25 2. 29 2. 70 2. 70 2. 75 2. 65 2. 36 2. 47 2. 91 2. 97 2. 79 2. 87 K2

0 ___________________________ MnO 2. 24 2. 23 2. 28 2. 27 2. 25 2. 25 2. 29 2. 32 2. 22 2. 22 2. 17 2. 15 __________________________ .1.1 . 10 . 10 .11 . 09 . 10 . 10 .11 .11 .10 .11 .11 Ti02 

__________________________ . 67 . 68 . 68 . 68 . 67 . 66 . 69 . 69 . 70 . 70 . 69 . 68 

JV2 ___________________________ 1. 5073 1. 5089 1. 5102 1.5112 1. 5127 1. 5141 

Sp gr. 2 a--- - - - - - - - - - - - - - - - - - - - - 2. 443 2. 464 2. 439 2. 426 2. 469 2. 483 

1 Total Fe as Fe20a. 2 By Janet Marteka and E. C. T. Chao. 3 Third place after the decimal not certain. 
ROSE, CUTTITTA, CARRON, AND BROWN D173 

Fe~0 , CaO, K20, Ti02, and Mn02• The chemical 

results are averages of duplicate determinations by 

the various methods. Using these different techniques, 

the chemical determinations were closely monitored 

by similar de terminations in granite G-1, diabase 

W -1, and selected National Bureau of Standards 

certified sa1nples. 

Silica was determined spectrophotometrically using 

a molybdenum-blue method (Bunting, 1944), gravimetrically by a volatilization-formaldehyde method 

described by Carron and Cuttitta (1962), and also by 

a combined gravimetric and photometric procedure 

(Jeffery and Wilson, 1960). Alumina (Al20 3) was 

determined by measuring the absorbance of the 

calcium aluminum alizarin red-S complex in a weakly 

acidic medium (pH 4.5) at 485 mJL (Parker and Goddard, 1950). Interference from iron was eliminated 

by use of potassium ferricyanide and thioglycolic 

acid as complexing agents. 

Total iron was determined spectrophotometrically 

with o-phenanthroline (Cuttitta, 1952, and Sandell, 

1959) and by a magnetic-susceptibility method developed by Thorpe and others (1963). Calcium 

oxide was determined by flamephotometry (Kran1er, 

1957), and by a semimicro, automatic, photometric 

titration with EDTA in the pH range 12.1-12.3 at 

590 mJL using murexide as the indicator. Potassium 

oxide was determined flamephotometrically at 766 n1JL 

using an instrument with a photomultiplier attachment. The sample was analyzed by bracketing 

between the closest potassium standards (Ray, 1956; 

Willgallis, 1957; Voimovitch and De bras, 1958). 

Titanium was determined spectrophotometrically with 

disodium-1, 2-dihydroxybenzene-3, 5-disulfonate (tiron) 

(Y oe and Armstrong, 194 7). The interference of iron 

was overcome by reduction with ascorbic acid at 

pH 4.7. The purple permanganate color was utilized 

for the spectrophotometric determination of manganese. The oxidation was effected with ammonium 

persulfate (peroxysulfate) at the boiling point in a 

phosphoric-nitric acid medium in the presence of 

silver nitrate. Manganese was also determined by 

Janet D. Fletcher using a quantitative spectrographic 

method similar to that described by Bastron and others 

(1960). 

REFERENCES 

Andermann, George, 1961, Improvements in the X-ray emission 

analysis of cement raw mix: Anal. Chemistry, v. 33, 1689-

1695. 

Balis, E. W., Bronk, L. B., Pfeiffer, H. G., Welborn, W. W., 

Winslow, E. H., and Zemany, P. D., 1962, Improved components for the X-ray emission analysis of the light elements: 

Anal. Chemistry, v. 34, p. 1731-1733. 

Bastron, H., Barnett, P.R., and Murata, K. J., 1960, Method for 

the quantitative spectrochemical analysis of rocks, minerals, 

ores, and other materials by a powder d-e arc technique: 

U.S. Geol. Survey Bull. 1084-B, p. 165-182. 

Bunting, W. E., 1944, The determination of soluble silica in very 

low concentration: Indus. and Eng. Chemistry, Anal. Ed., 

v. 16, p. 612-615. 

Carron, M. K. and Cuttitta, Frank, 1962, Determination of 

silica in tektites and similar glasses by volatilization: Art. 

30 in U.S. Geol. Survey Prof. Paper 450-B, p. B78-B79. 

Cuttitta, Frank, 1952, The colorimetric determination of total 

iron with o-phenanthroline-A spectropotometric study: 

U.S. Geol. Survey TEIR-223 issued by U.S. Atomic Energy 

Comm. Tech. Info. Service, Oak Ridge, Tenn. 

Jeffery, P. G., and Wilson, A. D., 1960, A combined gravimetric 

and photometric procedure for determining silica in silicate 

rocks and minerals: Analyst, v. 85, p. 478-485. 

Kramer, H., 1957, Flame photometric determination of calcium 

in phosphate, carbonate, and silicate rocks: Anal. Chim. 

Acta, v. 17, p. 521. 

Parker, C. A., and Goddard, A. P., 1950, The reaction of aluminum ions with alizarin-3-sulphonate, with particular reference to the effect of calcium ions: Anal. Chim. Acta, v. 4, 

p. 517-536. 

Ray, Norman, 1956, Flame photometric determination of sodium, 

potassium, calcium, magnesium, and manganese in glass and 

raw materials. Anal. Chemistry, v. 28, p. 34. 

Rose, H. J., Adler, Isidore and Flanagan, F. J., 1962, Use of 

La2 0 3 as a heavy absorber in the X-ray fluorescence analysis 

of silicate rocks: Art. 31 in U.S. Geol. Survey Prof. Paper 

450-B, p. B80-B82. 

--- 1963, X-ray fluorescence analysis of the light elements in 

rocks and minerals: Appl. Spec., v. 17, no. 4, p. 81--85. 

Rose, H. J., and Flanagan, F. J., 1962, X-ray fluorescence 

determination of thallium in manganese ores: Art. 32 in 

U.S. Geol. Survey Prof. Paper 450-B, p. B82-B83. 

Sandell, E. B., 1959, Colorimetric determination of traces of 

metals, 3d ed.: New York, Interscience Publishers, Inc., 

p. 537-542. 

Thorpe, A. N., Senftle, F. E., and Cuttitta, Frank, 1963, Magnetic and chemical investigations of iron in tektites: Nature, 

v. 197, p. 836-840, March 2, 1963. 

Voimovitch, I. A., and Debras, J., 1958, Determination of 

sodium, potassium, and lithium in silicates by flame photometry: Indus. Ceramics, v. 502, p. 321-27. 

Willgallis, A., 1957, Application of flame photometry to alkali 

analysis of minerals: Zeitscht. anal. Chemie, v. 157, p. 

249-257. 

Yoe, J. H., and Armstrong, A. R., 1947, Colorimetric determination of titanium with disodium-1, 2-dihydroxybenzene-3, 

5-disulfonate: Anal. Chemistry, v. 19, p. 10Q-102. 
Article 158 

DETERMINATION OF TOTAL IRON IN HEMATITIC IRON ORES 

BY X-RAY FLUORESCENCE SPECTROMETRY 

By WILLIAM W. NILES, Denver, Colo. 

Abstract.-A suite of hematitic iron-ore samples was analyzed 

by X-ray fluorescence spectrometry. Computations were made 

to derive an empirical· equation from which the amount of iron 

in a sample can be calculated. The changes from true values 

caused by interfering elements are compensated for by simple 

calculation. Comparisons with wet chemical analyses are shown 

A suite of iron-ore samples was analyzed to cheek the 

reliability of a field Inethod (Sheldon, 1 964) for estinlating iron content of hematitic iron ores. X-ray 

fluorescence spectrometry was selected because of its 

relative simplieity, rapidity, reasonable accuracy, and 

the wide range of elements that can be analyzed witl1out 

n1uch additional work on the samples. It was found 

that analyses for iron obtained by X-ray spectrometry 

were e01nparable in aceuracy to the classical volumetric 

methods. 

The X-ray spectrometric analyses were n1ade using a 

N orelco 50 KV -50l\1A X-ray spectrometer with heliunlpath attachn1ent and an FA-60 X-ray tube with molybdenum target. A lithiu1n fluoride analyzing erystal, 

a primary c~llin1ator tube % inch square by 4 inches 

long, and a secondary collimator 4 inches long with 

0.005-inch Soller slits were used exclusively. A flow 

proportional counter using P-10 gas and operated at 

1,550 volts was used as a detector. 

All samples were crushed to ~~-inch fragments or 

smaller in a small jaw crusher and then were ground to 

80-100 mesh with a mechanical grinder fitted with 

ceramic plates. A chart scan of each sample, before 

preparation, was made at the rate of 1° of arc per 

minute in order to estimate roughly the concentration 

of elements that might interfere with the iron determination through absorption effects. These estimates were made by comparison with an appropriate 

standard made up with an Si02 matrix. 

In these iron-ore samples, calcium and silicon were 

the only interfering elements present in appreciable 

quantities. None of the samples ·contained more than 

25 percent calcium. All samples were prepared as 

follows: Enough CaC03 was added to a 0.1500-g 

sample to make the total calcium equal to approximately 25 percent of the sample by weight (0.0375 g 

calcium). Si02 was added to bring the total weight 

of the mixture of sample, CaC03 and SiOz, to 0.3000 g. 

Boric acid as a noninterfering diluent was then added to 

obtain a total weight of 1.500 g. Each sample mixture 

was ground to an impalpable powder in an agate pestle 

and mortar under acetone, allowed to dry while grinding, and then pressed at 30,000 lbs. for 10 seconds into 

a pellet with a base of boric acid. 

Although the presence of silicon reduced the intensity 

of the Fe peak, Si02 was made the predominant matrix 

component in the prepared sample. The Fe standards 

were made up as Fe20 3 in Si02. The effect of the small 

differences between the a1nounts of Si02 in the samples 

and the amount in the standards was negligible because 

of the predominance of SiOz as a matrix component. 

However, one must correct f01 absorption due to calcium 

and silicon. 

Lachances' (written connnunication, 1960) correction 

factors, equations 1 and 2, and his expression for the 

1ron content, equation 3, were modified as follows: 

A-Bca (1) BcaXpercent Ca 

A-Bst (2) Bst X percent Si 

Percent Fe=B' + (BcaXFcaXpereent Ca) 

+ (B' s1XFstXpereent Si), (3) 

where Fca =faetor for absorption due to Ca, 

F81=factor for absorption due to Si, 

A= aetual percentage of Fe in standard, 

ART. 158 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl74-D175. 1964. 

D174 
NILES D175 

B=apparPnt percentage of Fe in same standard 

with matrix added, 

Bca=apparent percentage of Fe in same standard 

with Ca added, 

Bst=apparent percentage of Fe in same standard 

with Si added, 

B' =apparent percentage of Fe m sample, 

effected by matrix, 

B' ca=apparent percentage of Fe 1n sample, 

effected by Ca, and 

B' 81=apparent percentage of Fe 1n sample, 

effected by Si. 

By substituting equations 1 and 2 in 3, there is obtained 

P t F B'+(BcaX[A-Bca]Xpercent Ca) ercen e= BcaXpercent Ca 

+ (B' st X [A-B sd X percent Si) 

BstXpercent Si ' 

and upon simplification this equation becomes 

P t F B'+(B'caX[A-BcaD+(B'stX[A-Bsd ercen e= · Bca Bst 

Since the effect of the matrix is equal to the sum of 

the effects of each component in the matrix, this equation can be rewritten into the following form: 

Percent Fe B'+(B'X[A-B]) 

B 

B' (1+[A-BD. 

B 

The factor A B B is practically constant for all percentages of iron sought, and it is constant regardless of 

instrumental variations caused by normal fluctuations 

of voltage and temperature from day to day. 

Although this suite of iron-ore samples has a comparatively simple matrix composition, the method of 

computation has been used in analyzing samples containing as many as five interfering elements. The 

method has the advantage of allowing use of the same 

set of standards for rock and ores of widely varying 

matrices. 

Tables 158.1 and 158.2 show the accuracy and reproducibility of analytical results obtained by X-ray 

emission spectrometry of hematitic iron ores. The 

accuracy is based on the assumption that the chemical 

results are the absolute values. The chemical analyses 

were made by the standard dichromate volumetric 

o:xidation-reduction method. Only one determination 

was made on each sample by each method. X-ray 

results are given to hundredths of a percent for comparison but should not be considered accurate beyond 

two figures. The reproducibility of results of the 

method was determined by analyzing each of the 10 

samples 3 times. 

TABLE 158.1.-Comparison of results obtained by chemical and 

X-ray spectrographic methods 

(1) (2) (3) (4) 

Sample No. Fe Fe Absolute (percent) (percent) Absolute percentage by X-ray by wet difference variation method chemical 1(1)-(2)1 100 (3)/(2) method 1 

J12-13 _________________ 2. 70 2. 65 0.05 1. 89 J12-8 __________________ 5. 25 5. 27 . 02 . 38 J12-20b _______________ 10.86 10.86 . 00 . 00 J3-30-1 ________________ 15. 74 15. 79 . 05 . 32 J3-30-3 ________________ 18. 15 18. 23 . 08 . 44 J12-28b _______________ 21. 47 21. 65 . 18 . 83 J3-33b ________________ 26.93 26. 80 . 13 . 49 J12-40h _______________ 31. 59 31. 50 . 09 . 29 J3-32f _________________ 34. 93 34. 26 . 67 1. 96 J3-32i _________________ 44.11 44. 78 . 67 1. 50 

Average _____ - - - - - - - - -------- -------- -------- . 81 

1 Analyst: Dwight L. Skinner, chemist, U.S. Geological Survey, Denver, Colo. 

TABLE 158.2.-Reproducibility of analytical results for iron by 

X-ray emmission spectrography 

(1) (2) (3) (4) 

--------- Sample Fe Fe Fe No. (percent) (percent) (percent) Average 1st run 2d run 3d run 

------------- Jl2-13 ________ 2. 70 2.69 2.62 2.67 

Jl2-8_ -------- 5. 25 Fi.44 5.37 5.35 

J12-20b ------ 10.86 10.91 11.02 10.93 J 3-3Q-L ______ 15.74 15.31 15.72 15.59 

J3-30-3_ ------ 18.15 19.07 19.17 18.80 Jl2-28b _______ 21.47 22.78 22.66 22.30 J3-33b ________ 26.93 27.00 27.23 27.05 Jl2-40h _______ 31.59 31.86 32.04 31.83 J3-32L _______ 34.93 35.16 34.35 34.61 

J3-32L _ ------ 44.11 43.49 44.09 43.90 

Average ____ ---------- ---------- ---------- --------

REFERENCE 

(5) 

Absolute mean deviation 

1(4)-(1)1+1(4)-

(2)1+1(4)-(3)1/3 

0.03 

.07 

.06 

.19 

.43 

. 56 

.12 

.16 

.38 

.27 

------------------

(6) 

Absolute 

percent- age variation 

(5)/(4) 

1.1 2 

1 

5 

2 

9 

1 

4 

0 

0 

2 

1.3 

.5 

1.2 

2. 2 

2.5 

.4 

.5 

1.1 

.6 

1.1 7 

Sheldon, H.. P., 1964, Relation between specific gravity and iron 

content of rocks from the Red Mountain Formation, 

Alabama: U.S. Geol. Survey Bull. 1182-D. [In press] 
Article 159 

A GAS JET FOR D-C ARC SPECTROSCOPY 

By A. W. HELZ, Washington, D.C. 

Abstract.-A gas jet adaptable to enclosed arc-spark stands is 

described for use in d-e arc spectrochemical analysis. When 

used with a nitrogen-free gas, the jet is very effective for suppression of cyanogen bands. 

The gas jets for spectrochemical analysis described 

by Annell and Helz (1961) proved to be very effective 

for arc stabilization and cyanogen-band depression. 

However, they were designed for open-type arc stands 

and are difficult to use in spectrographic assemblies 

with conventional enclosed arc-spark stands. For enclosed stands it was considered desirable to use prefabricated electrodes of standard 1.5-inch length. 

Figure 159.1 is a drawing of Ghe jet described herein. 

To minimize the required electrode length, the ceramic 

cap forming the nozzle, A (fig. 159.1 section XX') was 

shortened. To compensate for this loss of control of 

the gas flow and to try to insure lamellar flow, the 

internal construction was redesigned as described below. 

The control gas enters a lower cha·mber (fig. 159.1, 0) 

surrounding the electrode, goes up through a ring of 

small holes (each 0.062 inch in diameter and 0.125 inch 

long) into an upper conically topped chamber (fig 159.1, 

B), and finally escapes through the annular space 

formed by the sample-bearing electrode and the ceramic 

cap. 

The jet was made in the U.S. Geological Survey 

analytical laboratory shop by J. B. Beasley. The main 

body of the jet is a X-inch-thick brass plate supported 

on an electrically insulated post. Self alinement with 

the arc-stand jaws is augmented by freedom of the 

frame to swing on the post and by affixing the post to 

the arc-stand base loosely to pern1it some translational 

motion. The plate is effectively water cooled with a 

U-shaped channel. This jet is for use with standard 

electrodes 1~ inches long and 0.242 inch in diameter. 

Thus, if the bottom hole of the brass plate and the 

central hole in the brass section that separates chambers Band 0 are each 0.250 inch in diameter, the electrode clearance will be 0.004 inch. At least this much 

clearance is advisable for convenience 1n inserting 

electrodes from above. 

The ceramic cap of the jet is a commercially available 

part used in tungsten-inert gas welding. The number 

6 Linde Heliarc cup (Linde Co., division of Union 

Carbide Corp.) is suitable for use with the X-inchdiameter electrodes. The ceramic cup is shortened 

fron1 1.25 inches to 0. 72 inch by cutting off the cylindrical tip at the outside circle where the cylindrical 

and conical parts of the cup meet. This leaves a short 

cylindrical section inside about 0.062 inch high and 

0.37 5 inch in diameter. 

The annular space for the escaping gas is 0.066 inch 

thick. The assembled height of the Jet is 1 inch. In 

use the lower electrode height is frequently adjusted to 

keep the burning rim of the crater a constant distance 

above the rim of the ceramic cup. About 2-n1illimeters 

seems optimum for this distance. 

This jet is much more compact than the earlier 

design of Annell and Helz (1961), but it is just as effective in producing a very steady arc and controlling 

cyanogen band interference. To show the effectiveness 

of the jet, 10 spectra of the cyanogen-band region are 

shown in figure 159.2. In addition to the spectrum of 

the arc in still air, spectra are also shown for the jet 

described herein, the Stallwood jet (Stallwood, 1954), 

and the enclosed Stallwood jet (see Spex Industries, 

Inc., 1962, for a summary status of Stallwood jets) at 

gas flows of 5, 10, and 15 cubic feet per hour. The 

control gas used was a mixture of 80 percent argon and 

20 percent oxygen. For each spectrum shown in figure 

159.2, 10 milligrams of a powdered rock was mixed with 

20 mg of graphite and burned in a 15-ampere d-e arc. 

The spectra were recorded on an SA-l plate using 38-

percent transmission and 1-minute exposures. These 

first-order spectra have a reciprocal linear dispersion of 

approximately 5 Ajmm. 

The difference between the type of gas flow for the 

jet described in this article and the gas flow of the 

Stallwood jet is strikingly illustrated by the spectra 

ART. 159 IN U.S. GEOL. SURVEY J»ROF. PAPER 475-D, PAGES D176-D178. 1964. 

D176 
HELZ D177 

Section X X' 

--+Water 

_, I 

I 

~1---f-1 - Gas 

Jl 

1 _I 1 

X x' 

Top view without cap 

FIGURE 159.1.-Jet design. Overall dimensions of the brass base plate, 3%X 1%X% inch. In section X X' the control 

gas enters compartment C, passes through the ring of small holes to compartment B, and then out through the top 

of the ceramic cap A. D is the supporting post. 
D178 ANALYTICAL TECHNIQUES 

J t:11~111UIIIUIIII :illlllllllllllllill I 1m 111111111111111 111 IIIIIIIIIIWtullllllllll''' Ut::nt 

I i:llli Ulllll~fllj 1

1

11IIHIII!Illllidl !'II lllllllllilllll Ill :11111111.!1111111111! 1/I!J'- Uti:lli 

H! II W i HlllllftiiUI •• IItllll I Iii! II 111,111 111111 n It ~ ! II! 

GIIIIMI:U 'ft:IUIUI ~11111111--111 11111111 

F HI Ulllllf 111: 1111~111 I 1111! 1r Ill IIIII! II I Ulll 

E II ~II:I:UIIIIIIIIII 1:111111.1111 ! 11::1:1~ 1111 ~t 11PIIIi'UIII111lH IIIII' fl 

olllll 1111111111 1-:illlllllllfllili!P 1111 llillllllllllll Iii llllllllllllllllilfillll 

c H ~: Ullllllllll 111111111111111 Ill · :IIH ill 1111111111111

[ Ill 111111111111 IIIII III! II 

s li !I UUIIUIIII :!111111111111 lll:ljij 1 1>11 Jlli 111:111111111 Ill i:lllll II ill I 

A Ullil·--·-··ltll!·---· . 

I 

0 

0'1 

LO 

('t) 

('t) 

co 

co 

('t) 

Ill I Ill 

Ill I IIi I 

I~ I I !I 

illlli!JII 

Ill I Ill I 

II I Ill I i 

Ill I Ill I 

ll I Ill 

I~ I Ill I 

Ill ll ll II II :11 

II I llll II 

IIi I il I II I II I II 

I ill 1111 II 

Ill 'll.ll.llillii•!IJ J I :II II IIIII 

, Ill I I I I' llll II 

:II I II I 1111 II 

:Ill I I J ,1, 1111 Ill 

! II: I. I II I: II II II 

11· Ill Ill hIll 

c.o 

.-t 

N 

-.:t 

FIGURE 159.2.-Spectra of 15-ampere d-e carbon arcs, cyanogen-band region. A, arc in air. B-D, enclosed Stanwood jet, 

5, 10, and 15 cubic feet per hour, respectively, of a mixture of 80 percent argon and 20 percent oxygen. E-G, open Stall wood 

jet, 5, 10, and 15 cubic feet per hour, respectively, of argon and oxygen mixture. H-J, jet described in the report; 5, 10, 

and 15 cubic feet per hour, respectively, of argon and oxygen mixture. 

for different rates of flow. For the jet described herein 

the intensity of the cyanogen bands decreases with 

increasing gas flow (spectra H, I, J). For the Stallwood jet, intensity increases with the gas flow (spectra 

E, F, and G). For the enclosed Stall wood jet, though 

at a much lower level, intensity decreases as the gas 

flow is increased frmn 5 to 15 cfh (spectra B, 0, and D). 

Cyanogen bands are absent in spectra D and J; that is 

the gas flow is 15 cfh with either the enclosed Stallwood 

jet or the jet described in this article. Thus the e:ffective exclusion of cyanogen-band spectra in carbon arcs 

is obtainable without cumbersome enclosures of the arc. 

REFERENCES 

Annell, C. S., and Helz, A. W., 1961, A constant-feed directcurrent arc: U.S. Geol. Survey Bull. 1084-J, p. 231-251. 

Spex Industries, Inc., 1962, Spex Speaker VII, no. 3: Scotch 

Plains, N.J. 

Stallwood, B. J., 1954, Air-cooled electrodes for the spectrochemical analysis of powders: Optical Soc. America Jour., v. 44, 

171 p. 
Article 160 

DOLOMITE SOLUBILITY IN GROUND WATER 

By IV AN BARNES and WILLIAM BACK/ Washington/ D.C. 

Abstract.-The ion-activity product (lAP) d of dolomite has 

been computed for 87 samples of ground water from a variety of 

geologic environments. The upper limit of the (lAP) d for 

samples in or very near equilibrium with calcite agrees with the 

higher equilibrium constants reported in the literature. 

Detailed studies of the composition of ground water 

have been undertaken in an effort to determine the 

thermodynamic state of reactions between minerals 

and water. The approach has been to obtain chemical 

analyses reflecting as closely as possible the composition 

of the water in its native state by detern1ining alkalinity, 

pH, and temperature at the time of sampling (Barnes, 

1964). Ion activities of the chemical constituents can 

be calculated from the laboratory data and the DebyeHtickel equation. From the activities, the ion-activity 

product (lAP) can be calculated for a particular 

reaction, using the law of mass action. Departure from 

equilibrium is determined by comparing the lAP 

calculated from the chemical analyses of water with the 

equilibrium constant, K (Back, 1960). If the lAP is 

greater than the K, the water is supersaturated with 

respect to the mineral of interest. For calcite, 

(1) 

and for dolon1ite, 

(2) 

Figure 160.1 shows values of IAPd and the ratio 

IAP/K for calcite. The pH, temperature, and bicarbonate concentrations for all these san1ples were determined in the field; the ionic strength of all samples 

plotted is less than 0.1 the linrit for the Debye-Htickel 

equation. 

For samples in equilibrium with calcite, that is, those 

with an IAP/Kratio of l.O±about 0.12, the data show 

that the n1axin1um lAP for dolomite is 2.87X 10-17 (see 

shaded area in fig. 160.1). The data indicate that the 

L1J 

1-

u 

1.6 

<i! 1.2 (.) 

Locality 

X Deep Springs, Calif. 1 

0 Puerto Rico 2 I 0 Central Florida3 

t> New Jersey 4 

+Deep Springs, Calif.5 

~ 1.0 ~...,._~~~-=--~.:-.;_...._~-d' 

LL. 

~ a.. 

::!; 

0.6 

0.4 0 

0.2 

10-19 10-18 10-11 

lAP FOR DOLOMITE 

1 Barnes (unpublished analyses, 1962). 2 J. W. Crooks (oral communication, 1962). a Back (1963). 4 Seaber (1962). • Jones (1961). 

FIGURE 160.1.-Graph showing relation ot 10n-activ1ty product 

for dolomite and the lAP/ K ratio for calcite. Shaded area represents samples in equilibrium with calette. 

upper limiting value for the lAP for dolomite in ground 

waters in equilibrium with calcite lies between approximately 1.5 X.10-17 and 3 X 10-17. Owing to the sluggishness of the dolornite precipitation, water supersaturated 

with calcite probably is supersaturated also with 

dolomite. 

These lAP data for dolon1ite may be compared with 

reported equilibrium constants for dolomite, as follows: 

Holland others 1 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 X 10-17 

Kramer (1959) _____________________ 1.5X10-17 

Hsu (1964)_________________________ 2X1o·-l7 

Van Tassel (cited by Halla, 1962) _____ 2.5X10-17 

1 Holland, H. D., Kirsipu, T.V., Huebner, J. 8., and Oxbough, V. M., 1962, _On some aspects of the chemical evoluti:m of cave waters: Princeton Univ., techmcal 

report (duplicated). 

ART. 160 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl79-D180. 1964. 

D179 
D180 GEOCHEMISTRY OF WATER 

Halla and Ritter (cited by Kramer, 

1959) ___________________________ _ 

Robie (cited by Halla, 1 962) ________ _ 

Garrels and others (1960) ___________ _ 

3 X 1Q-17 

6.6 X 10-19 

4.7X10-20 

If the lower solubilities of Garrels and Robie are accepted, all water samples used in this study are supersaturated with dolomite. On the other hand, if we 

postulate that dolomite reacts with aqueous solutions 

and tends toward an equilibrium, the equilibrium constant would appear to be on the order of 2 to 3 X 10-17. 

In any event, the observed characteristics of the ground 

waters sampled are closer to the properties predicted at 

equilibrium with the higher solubilities reported than 

with the lower solubilities. 

REFERENCES 

Back, William, 1960, Calcium carbonate saturation in ground 

water from routine analyses: U.S. Geol. Survey WaterSupply Paper 1535-D, 14 p. 

Back, William, 1963, Preliminary results of a study of the calcium 

carbonate saturation of ground water in central Florida: 

Internat. Assoc. Sci. Hydrology, v. 8, No. 3, p. 43-51. 

Barnes, I van, 1964, Field measurements of alkalinity and pH: 

U.S. Geol. Survey Water-Supply Paper 1535-H. [In press] 

Garrels, R. M., Thompson, M. E., and Siever, Raymond, 1960, 

Stability of some carbonates at 25°C and one atmosphere 

total pressure: Am. Jour. Sci., v. 258, p. 402. 

Halla, Franz, 1962, The free energy of the formation of dolomite 

from its carbonate components: Sedimentology, v. 1, p. 191. 

Hsu, K . . J., 1964, Solubility of dolomite estimated on the basis of 

the chemical composition of Florida ground-waters, in 

Abstracts for 1963: Geol. Soc. America Spec. Paper. 

[In press] 

Jones, B. F., 1961, Zoning of saline minerals at Deep Spring Lake, 

California: Art. 83 in U.S. Geol. Survey Prof. Paper 424-B, 

p. B199-B202. 

Kramer, J. R., 1959, Correction of some earlier data on calcite 

and dolomite in sea water: Jour. Sed. Petrology, v. 29, 

p. 46.5. 

Seaber, P. R., 1962, Cation hydrochemical facies of ground water 

in the Englishtown formation, New Jersey: Art. 51 in U.S. 

Geol. Survey Prof. Paper 45Q-B, p. B124-B126. 
Article 161 

EFFECT OF TREE LEAVES ON WATER QUALITY 

IN THE CACAPON RIVER, WEST VIRGINIA 

By KEITH V. SLACK, Washington, D.C. 

Abstract.-Accumulation of leaf litter in pools at low flow increase~;~ water color and results in marked changes in water composition. Temperature decreases rapidly from surface to bottom 

in the shallow pools. Dissolved-oxygen concentration decreases, 

but concentrations of many other solutes increase directly with 

water color. A film, believed to be ferric hydroxide, occurs on 

the surface of pools in which decomposition of litter is especially 

intense. Flushing of the pools by a rise in stream stage reduces 

the color and improves water quality. 

Changes in water composition resulting from natural 

additions of organic matter were investigated as part of 

a study of biological influences on water quality of 

streams. Previous work in Indiana indicated that the 

autumnal accumulation of tree leaves in streams coincident with the annual low-flow period occurs widely 

and is important in cycling of elements in nature. This 

accumulation is unusual in that it represents a natural 

environment in which decomposition greatly exceeds 

production of new organic matter. The environment is 

marked by low dissolved-oxygen concentration and considerable water color, which presumably is due to decomposition of plant material. Although of short 

duration, the condition seriously degrades water quality 

and can result in the death of aquatic organisn1s. 

The literature contains many references to the effects 

of leaf litter on the chemical quality of streams; for 

example, Schneller (1955) and Slack (1955) reported 

that the decay of leaves in pools generally resulted in 

greater water color and in the formation of free C02 and 

lower dissolved-oxygen concentrations. Sylvester (1959) 

reported that replacement of native coniferous forests 

with deciduous trees in the vVenatchee River basin ' ~~ ashington, resulted in increased water color. Hynes 

(1960) described Huet's (1951) work, which indicated 

that a substance toxic to fish was derived from needles 

of spruce and red cedar. Chase and Ferullo (1958) 

showed that leaves deplete dissolved oxygen under 

aerobic conditions in the laboratory; after 386 days, 

maple leaves had consumed a weight of oxygen equivalent to 75 percent of their initial dry weight. In the 

same length of time, oak leaves and pine needles exerted 

oxygen demands of about 50 percent of their dry weight. 

Myers (1961) suggested that manganese in San Clemente Reservoir, Calif., was leached from oak trees in 

the watershed. Robinson and others (1958) showed 

that leaves of hickory trees concentrated rare-earth elements to a remarkable degree. Thus, various species of 

trees may n1ake widely differing chemical contributions 

to streams through leaf litter. 

Discolored water is neither a perennial phenomenon 

nor does it occur in all streams. Frequent rains during 

the peak leaf-fall period may flush the organic load 

downstream and dilute substances leached from the 

fresh leaves. The most favorable conditions for 

development of discolored water are a pooled stream 

with little or no surface flow and with stands of deciduous trees near the channel. 

Discoloring of water begins when tree leaves begin to 

drop, usually in Septen1ber. The freshly shed leaves 

accumulate at the downstream end of pools, where they 

float on the surface at first but gradually sink to form 

a blanket over the streambed; later arrivals replenish 

the surface layer. Eventually the lower ends of pools 

become filled with a waterlogged mass of leaves that 

may inhibit flow over riffles. Unless there is a rise in 

stage and a flushing and exchange of water in the pool, 

a critieal period is established. 

As the waterlogged leaves decompose by bacterial 

action, the supply of dissolved oxygen in the pool is 

depleted. Although decomposition of the leaves causes 

an increase in the mineral content of the water, the 

amount of the increase attributable to factors such as 

leaching of soluble substances from leaves, concentration by evaporation, mineral-matter release from sediART. 161 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl81-Dl85. 1'964. 

Dl81 
D182 GEOCHEMISTRY OF WATER 

n1ents by organic cmnplcxing and chemical reduction, 

and bacterial breakdown of leaf tissue is not known. 

The literature indicates that all these processes n1ust be 

considered. In early stages of decon1position the 

color of the pool water closely resernbles that of bog 

water. Under extreme conditions, the water acquires 

an inky appearance, which gives rise to the name'"black 

water" in parts of the Midwest where discoloration is 

common. 

STUDY OF THE CACAPON RIVE'R, W. VA. 

A reach of the Cacapon River, Morgan County, 

W. Va., about 14 strearn rniles above the mouth 

where a series of elongate wooded islands extend parallel to the river bank, was selected for detailed study. 

At times of low flow, the channel whieh normally separates these islands from the right bank of the river 

becomes dry or is redueed to a few pools. Diseolored 

water was general in the pools and in partly isolated 

rnarginal waters along this reaeh in October 1961. 

Three different environments, shown on figure 161.1, 

were sampled: (a) a riffle of the Caeapon River about 

18 centimeters deep; (b) a slightly eolored pool or 

baekwater ehannel, whieh was eonnected with the 

river and in which the intensity of color increased with 

distanee from the river, sampled at the upper end, 

about 5 1neters from its junction with the main stream; 

and (c) an isolated highly eolored pool about 6~6X3 

m in area, at the base of a steep bank. In addition, 

FIG"f!RE 161.1-Sketch showing sampling sites on the Cacapon 

R.tver, Morgan County, W. Va. A, riffle on the river; B, 

slightly colored pool; C, highly colored pool; and D, moderately colored pool. 

a moderately colored pool (d) was sampled as part of 

a temperature study on October 30, 1961 (table 161.3). 

The reaeh of river studied was shaded by a hardwood 

forest eonsisting of the following kinds of trees: maple, 

cottonwood, tulip tree, blue bee~eh, syeamore, elm, 

dogwood, aspen, and oak. Many kinds of deciduous 

leaves were visible in the water on October 22 1961 ' ' the date of the initial sampling, and most had sunk to 

the bottom. 

Chemical composition 

The chemieal composition of the water of the river 

and the pools is shown in tables 161.1 and 161.2, 

whieh permit comparison between sampling sites on a 

single date and on different dates. The tables show 

that coneentrations of many substances tend to inerease as water color inereases, although calcium, 

biearbonate alkalinity, dissolved solids, and specific 

conductanee, all were higher in the slightly colored 

pool (B) than in the highly colored pool (C). The 

appearance of the ground on October 22 and 29 suggested that water from the main ehannel had recently 

flowed into the highly colored pool (C), although the 

eomposition of water of the ehannel and the pool 

differed greatly. Pool C was separated from the river 

by a low mound of wet leaves and roeks about 1 m in 

width. Wet masses of a green alga (Oedogonium) 

eovered mueh of this barrier; however, the fresh appearance of the algae must have resulted from a light rain 

reeorded on Octo her 21, because streamflow records 

show no significant rise of the river during October. 

The low caleimn and carbonate eoncentrations of the 

highly colored pool (C) could be explained in various 

ways; for example, mueh of its water could have been 

derived from local runoff or dilute ground water containing alkalies leached from the leaves. Another possibility is that ion-exchange reactions between the leaf 

material aHd the pool water produced water enriched 

in alkalies but depleted in calcium and bicarbonate 

(Hutchinson, 1957, p. 573). Still another explanation 

is that snails ( Gyraulus) inhabiting this isolated pool 

extracted caleium carbonate from solution for shell 

formation, thus causing a lower calcium concentration. 

The volume of the highly colored pool was roughly 

2,000 liters, indieating a deficit of 18.5 milligrams of 

calcium per liter compared with the calcium content 

of the other waters sampled, or a total loss of 37 grams. 

If this quantity were spread among an estimated population of 100 snails, the necessary uptake of 0.37 g 

calcium or 0.92 g calcium carbonate per animal would 

seem excessive for this thin-shelled form. However, 

without better population data the possibility of biological utilization cannot be excluded as a factor causing 

depletion of calcium carbonate in the highly colored 
SLACK D183 

TABLE 161.1.-Water properties at three sampling sites, Cacapon River, W. Va., during autumn 1961 1 

[Analyses by H. R. Feltz, Washington, D.C.] 

Main 

stream 

(A) 

October 22 

Slightly 

colored 

pool (B) 

Highly 

colored 

pool (C) 

Main 

stream 

(A) 

October 29 

Slightly 

colored 

pool (B) 

Highly 

colored 

pool (C) 

Main 

stream 

(A) 

November 19 

Slightly Highly colored colored 

pool (B) pool (C) 

-------------------------------1----1-----1----1---------------------

Color (platinum-cobalt scale units)_________ 7 20 

Chemical constituents (ppm) : Silica________________________________ 2. 0 

Iron_________________________________ . 08 

7. 3 

1. 1 

Manganese_____________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . 00 . 93 

Calcium____________________________ 28 

Magnesium_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5. 8 

Sodium______________________________ 1. 7 

Potassium _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1. 5 

Bicarbonate _________________________ 106 

SuJfate_ _ __ __ ____ ________ ______ ____ _ 10 

Chloride______________________________ 1. 5 

Fluoride____________________________ 1 

Nitrate_____________________________ 1 

28 

7. 1 

5. 6 

7. 5 

134 

4. 4 

3. 0 

.2 

.4 

Phosphate__________________________ 16 . 08 

143 

100 

Dissolved solids (ppm) (residue at 180°C) ___ 107 

Hardness (ppm) _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ 95 

Free carbon dioxide (ppm)_________________ 4. 2 34 

Specific conductance (micromhos at 25°C) _ _ 197 233 

pH_____________________________________ 7. 6 

Ignition loss (ppm) _____________________________ _ 6. 8 

15 

1 Sample locations shown on figure 161.1. 

TAB~E 161.2.-Spec~rographic analyses of minor-element content, in 

mterograms per hter, of three types of water, Cacapon River, 

W. Va., dunng autumn 1961 1 

[Analyses by W. D. Silvey, Sacramento, Calif.] 

October 22 October 29 

Main Slightly Highly Main Slightly Highly stream colored colored stream colored colored 

(A) pool(B) pool (C) (A) pool(B) pool(C) 

------------ Aluminum _______ 12 32 93 15 14 82 Cobalt ___________ ~3.3 ~3.3 ~3.3 <3.3 ~3.3 ~3.3 Copper ___________ 7. 3 <3.3 <3.3 <3.3 <3.3 <3.3 Iron ___ ----------- 35 >100 >100 28 >IOO >IOO Manganese _______ 11 >200 >200 31 >200 >200 Molybdenum ____ <.67 <.67 <.67 <.67 ~.67 ~6. 7 NickeL __________ ~.67 3. 6 7. 0 <.67 4. 5 6. 7 Lead _____________ 88 27 80 20 <3.3 32 Titanium ________ <1.3 3. 4 ~1.3 <1.3 ~1.3 ~1.3 Vanadium _______ <.67 <.67 ~.67 <.67 <.67 ~.67 

I Sample locations shown on figure 161.1. 

November 19 

Main 

stream 

(A) 

--

22 

~3.3 

<3.3 47 

9. 3 

<.67 

. 87 

13 

<1.3 

<.67 

Highl 

colore y 

d pool(C) 

--

1 

~3. 

<3.3 

>100 33 

<.6 

1.5 

8.0 

<1.3 

<.67 

pool. Both Slack (1955) and Schneller (1955) found 

that alkalinity increased with color in all their samples 

of leaf-colored waters in Indiana. 

Some d~fferences between the highly colored pool (G) 

and the slightly colored pool (B), as noted in the October 

22 and 29 san1ples, 1nay have resulted from differences 

in redox potentials, which could explain the greater 

concentrations of iron, n1anganese, and free C02 in 

the more nearly anaerobic, highly colored pool (C). 

Just the opposite was observed for magnesium, sodium, 

and potassium, which were more concentrated in the 

slightly colored pool (B). In both colored waters (B, G), 

sulfate values were lower than in the river water (A). 

This may have resulted from reduction of sulfate to 

sulfide. Although one might expect the sulfate con120 

6. 2 

1.9 

2. 8 

9. 5 

3. 0 

3. 1 

6. 8 

44 

8. 2 

3. 0 

.2 

1.2 

. 12 

78 

36 

56 

106 

6. 1 

18 

4 

2. 6 

1 

. 00 

31 

5. 2 

1. 7 

1.6 

110 

11 

1.5 

1 

1 

. 06 

115 

99 

4. 4 

20.5 

7. 6 

60 

8. 3 

1. 1 

. 40 

30 

7. 8 

4. 8 

8. 2 

142 

4. 4 

3. 5 

.2 

.6 

. 05 

155 

108 

28 

244 

6. 9 

22 

90 

7. 9 

2. 2 

3. 0 

9. 5 

4. 5 

3. 1 

6. 8 

55 

6. 0 

3. 0 

1 

.8 

. 12 

80 

42 

55 

117 

6. 2 

12 

2 

4. 1 

30 

. 02 

. 02 

4. 0 

1.9 

1.8 

99 

11 

2. 5 

.0 

. 1 

. 01 

103 

90 

4. 0 

190 

7. 6 

3 

6. 1 

27 

. 02 

. 08 

4. 3 

2. 5 

2. 5 

97 

9. 8 

3. 0 

1 

1 

. 01 

105 

85 

12 

184 

7. 1 

3 

7. 8 

18 

. 02 

. 01 

3. 9 

2. 2 

2. 2 

69 

8. 0 

3. 0 

1 

.2 

. 01 

77 

62 

14 

138 

6. 9 

centration to be lowest in the highly colored pool (G), 

n1inimum values were found in the slightly colored 

pool (B). 

Concentrations of aluminum and nickel increased as 

water color increased (table 161.2). Similarly, iron and 

manganese concentrations were higher in the colored 

waters than in the main stream. The distribution of 

lead in the different environments resembled that of 

sulfate in that the slightly colored water (B) contained 

lower concentrations than either the main stream or the 

highly colored water (G). Data for other minor 

elements are inconclusive. 

It is tentatively concluded that the compositional 

differences observed between the river and the colored 

waters resulted from leaching and decomposition of 

leaf litter in isolated environments. Differences between the highly colored and slightly colored pools 

probably reflect differences in source of the water. 

Between October 22 and 29 the solute concentration 

in the highly colored water (G) increased somewhat, 

possibly due to evaporation. Although the pool was 

still isolated on November 19, its color had disappeared; 

the pool probably had been flooded and flushed by a 

rise in river stage on November 7 and 8. Discharge at 

the gaging station about 7 miles downstream from the 

san1pling sites increased from 59 cubic feet per second 

on October 29 to 240 cfs on November 8, but decreased 

to 82 cfs on November 19. 

On October 22, sn1all patches of a thin inflexible 

surface film were present on the highly colored pool. 
D184 GEOCHEMISTRY OF WATER 

A week later the entire surface was covered with a film 

in which there were only a few breaks or tears. The 

film probably was composed of ferric hydroxide, which 

formed where air oxidized ferrous iron in the water. 

Pearsall and Mortimer (1939) described such a condition on stagnant pools in bogs. The contribution of 

other metallic ions, for example manganese, to a 

surface film is unknown. In the colored pools under 

discussion, the films tended to remain in the center of 

an open space. Reducing conditions may have been 

so intense near the n1argins of pools that formation of 

the oxidized film was impossible. The effect of a 

surface film on reactions at the air-water interface may 

be important. For example, evaporation and reaeration probably are inhibited. 

Colored water resulting from leaf decay generally is 

accompanied by low concentrations of dissolved oxygen. 

Analysis, by the Alsterberg (azide) modification of the 

Winkler method, of two samples of highly colored pool 

water gave an average of 0.09 parts per rnillion dissolved 

oxygen or about 0.8 percent of saturation on October 30. 

This method is not recommended for samples containing 

1 mg or more of ferrous iron per liter or appreciable 

quantities of sulfite (Rainwater and Thatcher, 1960, 

p. 233). Because of the effects of interfering substances, the dissolved-oxygen values reported here may 

be too low, but they indicate very low concentrations. 

A few measurements made with a polarographic oxygen 

electrode (Kanwisher, 1959), on October 23, supported 

this conclusion. Readings in the highly colored pool 

(C) were 2 percent of saturation at the bottom (24.5 

em), and a maximum of 6 percent at other places. 

On October 30, the slightly colored pool (B) had a 

dissolved-oxygen concentration of 1.9 ppm (18 percent 

of saturation) and the main stream of the river (A) had 

10.3 ppm (99 percent of saturation). As with most 

other quality factors, water color correlated well with 

dissolved-oxygen content. The lowest oxygen concentration, 0.06 ppm, was measured near the upstrearn end 

of the highly colored pool (C), where decomposition of 

litter seemed to be especially far advanced. 

A further indication of low-dissolved oxygen content 

was the presence of many snails (Gyraulus) on leaves 

at the water surface along the margins of the highly 

colored pool (C). These snails are able to withstand 

unfavorable enrivonments better than most mollusks, 

owing to their ability to breathe air at the surface. 

Similar groups of snails were not observed in the slightly 

colored pool (B), which retained a connection with the 

oxygenated river water. 

Water temperature 

Temperature measurements made on two dates 

(table 161.3) indicated marked thermal stratification during 

the study period. On October 23, the temperature of 

the highly colored pool (C) increased from 6.6 °C at a 

depth of 2.5 em to 10°C at a depth of 11.5 em. Below 

11.5 em the water was isothern1al, although the thermonleter used dia not permit determination of the 

exact inflection points on the temperature-depth curve. 

On October 30, the water temperature of all colored pools 

decreased with increasing depth (table 161.3). The 

steepness of the thermal gradients in the three pools 

tested varied directly with intensity of water color. 

This relationship suggests that the mechanism involved 

was the rapid absorption of solar radiation near the 

surface by the colored water. No differences in temperature were noted in the rnain stream at comparable 

depths. The river-water temperature was highest and 

the tern perature of the highly colored pool (C) was lowest on 4 of 5 days for which bottom-water temperatures 

were measured. Bottom-water temperature of the 

slightly colored pool (B) was always higher than that 

of the highly colored pool (C). This could have resulted 

from slow mixing with warmer river water from the 

downstream end of the slightly colored pool. It could 

also have resulted from a flow of cool ground water 

from the highly colored pool ( 0) through the moderately 

colored pool (D) into the slightly colored pool (B). 

The October 30 series of bottom temperatures seems to 

support this possibility. 

In summary, the effect of leaves on stream-water 

quality and temperature is a localized interaction beTABLE 161.3.-Water temperature, in degrees centigrade, at 

three sampling sites, Cacapon River, W. Va., during autumn 

1961 

Depth (em) 

October 23 

Highly 

colored 

pool(C) 

Main stream (A) 

October 30 

Slightly 

colored 

pool (B) 

Moderately 

colored 

pool (D) 

Highly 

colored 

pool (C) 

2.5 ____________ 6.6 13.2 14.9 14.1 14.1 

11.5 ___________ 10.0 -------- -------- -------- -------- 16.5 ___________ -------- -------- -------- 10.2 

18 .. 1) ___________ -------- -------- 10.8 

19.0 ___________ -------- 13.2 

(bottom) 

(bottom) 

(bottom) 

20.0 _______ ---- -------- -------- -------- -------- 8.5 

24.5 ___________ 9.8 

Average thermal gradient, 

(degrees 

centigrade 

(bottom) 

per em) _____ 0.14 o.oo 0.26 0.28 

(bottom) 

0.32 
SLACK D185 

tween the marginal vegetation and the water in lowflow pools, in backwater, or flood-plain pools. Leaf 

litter from other parts of the drainage area contributes 

also to the particulate and dissolved load of the stream. 

Probably this effect is delayed until heavy rains produce 

sufficient runoff to transport these materials downstream and out of the basin or into larger water bodies 

where their effects are less noticeable. 

REFERENCES 

Chase, E. S., and Ferullo, A. F., 1958, Oxygen demand of leaves 

in water: Water and Sewage Works, v. 105, no. 5, p. 204-

205. 

Huet, M., 1951, Nocivite des boisements en Epiceas (Picea 

excelsa Link.) pour certains cours d'eaux de 1' Ardenne 

Belge: Verh. int. Ver. Limnol., v. 11, p. 189-200. 

Hutchinson, G. E., 1957, Geography, physics, and chemistry, 

v. 1 of A treatise on limnology: New York, John Wiley and 

Sons, Inc., 1015 p. 

Hynes, H. B. N., 1960, The biology of polluted waters: Liverpool, 

England, Liverpool Univ. Press, 202 p. 

Kanwisher, John, 1959, Polarographic oxygen electrode: Limnology and Oceanography, v. 4, no. 2, p. 210-217. 

Myers, H. C., 1961, Manganese deposits in western reservoirs 

and distribution systems: Am. Water Works Assoc. Jour., 

v. 53, no. 5, p. 579-588. 

Pearsall, W. H., and Mortimer, C. H., 1939, Oxidation-reduction 

potentials in waterlogged soils, natural waters and muds: 

Jour. Ecology, v. 27, p. 483-501. 

Rainwater, F. H., and Thatcher, L. L., 1960, Methods for 

collection and analysis of water samples: U.S. Geol. Survey 

Water-Supply Paper 1454, 301 p. 

Robinson, W. 0., Bastron, Harry, and Murata, K. J., 1958, 

Biogeochemistry of the rare-earth elements with particular 

reference to hickory trees: Geochim. et Cosmochim. Acta, 

v. 14, p. 55-67, 2 figs. 

Schneller, M. V., 1955, Oxygen depletion in Salt Creek, Indiana, 

in v. 4 of Investigations of Indiana Lakes and Streams: 

Indiana Univ. Dept. Zoology, p. 163-175. 

Slack, K. V ., 1955, A study of the factors affecting stream 

productivity by the comparative method, in v. 4 of Investigations of Indiana Lakes and Streams: Indiana Univ. Dept. 

Zoology, p. 3-47. 

Sylvester, R. 0., 1959, Water quality study of Wenatchee and 

Middle Columbia Rivers before dam construction: U.S. 

Fish and Wildlife Service, Spec. Sci. Rept.-Fisheries, no. 

290. 
Article 162 

RELATION. OF PERCENT SODIUM TO SOURCE AND MOVEMENT OF GROUND WATER, 

NATIONAL REACTOR TESTING STATION, IDAHO 

By F. H. OLMSTED, Yuma, Ariz. 

Work done on behalf of the U.S. Atomic Energy Commission 

Abstract.-Most of the ground water in the National Reactor 

Testing Station is of the calcium magnesium bicarbonate type. 

The percent sodium decreases northwestward, where the source 

of recharge is a limestone and dolomite terrane, and increases 

southeastward, where the source is in silicic volcanic rocks and 

lacustrine deposits. 

The National Reactor Testing Station occupies an 

area of about 900 square miles in the norGh-central part 

of the eastern Snake River Plain in Idaho. Ground 

water occurs in a regional zone of saturation in flatlying basalt flows and subordinate interbedded sediments of Quaternary age. The most important waterbearing openings are voids in the basalt adjacent to 

interflow contacts, openings in cinders, scoria, and 

blocky zones; and interstitial pores in the sedimentary 

deposits. The upper part of the regional ground-water 

body is unconfined in most places, but quasi-artesian 

conditions are common at depths of more than a few 

tens of feet below the water table. Depths to the water 

table within the station range from about 200 feet to 

more than 700 feet. Regional ground-water movement 

is south to southwest (fig. 162.1), although locally the 

water moves in other directions for short distances. 

A study of the chemical character of ground water 

in the station was based on analyses of 148 san1ples 

collected from 92 wells during the period 1949-61. 

Most of the water is of the calcium magnesium bicarbonate type, with calcium plus magnesium constituting 

more than 70 percent of the total cations, in equivalents 

per million, and bicarbonate more than 70 percent of 

the total anions. Other chemical types, chiefly chloride 

waters, are present in son1e areas as the result of 

contamination by liquid waste from the operation of 

atomic facilities, by return flow from irrigation in the 

Mud Lake area northeast of the station, and probably 

by natural sources as yet not identified. A small 

body of ground water with a high sulfate content has 

been formed by seepage from a waste-disposal pond 

at one of the atomic facilities. As of 1961, none of 

this water, which is perched above a layer of basalt, 

had reached the regional gTound-water body. 

Except for small bodies of water that are high in 

chloride or sulfate content and contain as much as 

1,000 parts per million of dissolved solids, the range in 

chemical characteristics of the water is not large. In 

most of the bicarbonate water the concentration of 

dissolved solids ranges from about 180 to 240 ppm. 

The generally low mineralization of the ground water 

reflects the low solubility of the rocks with which the 

water has been in contact and the moderate to abundant 

precipitation in the mountainous areas that furnish the 

principal recharge. Recharge from precipitation on 

the Snake River Plain is believed to be minor. 

The chemical characteristics of the ground water do 

not appear to vary greatly with depth except near 

waste-discharge facilities and where deep wells penetrate 

thick extensive lacustrine deposits. Percent sodium 

as high as 80 in water from these wells probably results 

from cation exchange with the lacustrine clays. 

Areal differences in ionic ratios in the ground water 

beneath the station help to identify the sources of the 

water and to corroborate the inferred paths of water 

movement. In this respect, the variation in sodium 

plus potassium (chiefly sodium) in terms of percent of 

total cations (in equivalents per million) is particularly 

revealing. 

The available information indicates that at most 

places the chen1ical character of the ground water is 

fairly uniform to depths as great as 200 feet below the 

water table-that is, in the upper 200 feet of the 

ART. 162 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES Dl86-Dl88. L964. 

Dl86 
43° 

30' 

" ' \ 

\ 

\ 

\ 

\ 

I 

\ 

\ 

l 

113 ooo' 

I 

I 

0 

0 

I 

I 

OLMSTED 

I 

I 

t 

0 

I 

\ 

~ 

0' 

) 

/ 

/ C) 

C\1 

0 

112° 30' 

I 

I 

L. ....__, ·--. 

I 

J" 

L ___ ---,_ 

\ " \ I 

t I 2~ ""j 

rf 

~i I · t~ I 

I (PI i 

I . 

I I 

J 

I 

I , ..r 

_j 

___ r------' 

rI o I 

I ~ I i 

cv J ~~ C\1 j ! _7:-... --;Y---J-_r'l_o__ _______ j 

,q, 

General direction of ground-water 

movement, August 1961 

1 0 5 10 MILES 

EXPLANATION 

---24-

lsogram of sodium plus potassium, 

in percent of total cations 

lsogram interval 4 percent 

0 

Water well 

IDAHO 

Dl87 

C? 

FIGURE 162.1..-Map of the National Reactor Testing Station, Idaho, showing percent sodium plus potassium in ground water in the 

upper 200 feet of the ground-water body_ 

716-626 0-64--13 
D188 GEOCHEMISTRY OF WATER 

regional ground-water body. The chemical character 

of the water below that zone is not well known; 

accordingly, only analyses of ground water in the zone 

from the water table to 200 feet below the water table 

were used in the present study (fig. 162.1). 

In general, the percent sodium plus potassium 

increases gradually from about 8 percent along the 

northwest boundary of the station to more than 24 

percent in the southeast. Exceptions to this general 

pattern are the two southernmost bodies of water high 

in percent sodium, which consist of contaminated water 

also high in chloride, and two small bodies of highsodiunl water farther northeast, which are believed to 

be affected by upward flow in wells of sodium bicarbonate water from depths greater than 200 feet below 

the water table. 

The isograms in figure 162.1 have a general southsouthwesterly trend-parallel to the regional groundwater flow lines inferred from water-level contour maps. 

The lower percent sodiun1 plus potassium in the water 

beneath the northwestern part of the station reflects 

the extensively exposed limestone and dolomite in the 

Lost River and Lemhi Ranges to the northwest, and 

the higher percent sodium plus potassium in the water 

beneath the southeastern part of the station reflects the 

abundance of silicic volcanic rocks in the region to the 

north and northeast. Some of the water from the 

north and northeast also has moved through a considerable volu1ne of fine-grained lacustrine depos1ts in the 

Mud Lake region and, therefore, may have been 

affected by cation exchange. The basalt, which forms 

the main aquifer system, appears to have little effect 

on the chemical character of the water moving through 

it. 

The gradual, rather than abrupt, southeastward 

increase in percent sodium plus potassium in the upper 

200 feet of the ground-water body is believed to indicate a progressive decrease in the proportion of lowsodium water derived from the northwest and a progressive increase in the proportion of water higher in 

sodium content derived from the north and northeast. 

Variations in the rate of replenishment from these 

sources are indicated by substantial changes with time 

in the direction of ground-water flow, which are inferred 

from observed changes in the configuration of the 

water table in the northern part of the station. 
Artic'le 163 

RELATION OF FLUORIDE CONTENT TO RECHARGE 

AND MOVEMENT OF GROUND WATER IN OASIS VALLEY, 

SOUTHERN NEVADA 

By GLENN T. MALMBERG and T. E. EAKIN, Carson City, Nev. 

Work done in cooperation with the Nevada Department of Conservation and Natural Resources 

Abstract.-Although most of the ground water contains excessive fluoride, a local supply that meets Federal standards for 

public water supplies was located by means of a hydrogeochemical reconnaissance. Elsewhere in the Great Basin where waterquality problems exist, similar studies could be applied in 

locating usable ground water. 

An unusually high content of certain minor eonstituents, such as boron or fluoride, or of total dissolved 

solids renders ground water unfit for various uses in 

many valleys in the Great Basin. In Oasis Valley, 

Nev., about 100 miles northwest of Las Vegas, nearly 

all the ground water has a fluoride content higher than 

permissible limits established by the U.S. Public Health 

Service (1962) for public supply. A hydrogeocnemical 

reconnaissance by the authors (1962) indicated favorable possibilities for developing ground-water supplies 

of low fluoride content. Subsequent test drilling has 

confirmed the predictions. 

Oasis Valley is about 430 square miles in extent and 

is drained by the Amargosa River (fig: 163.1). The 

Amargosa is an intermittent stream which rises in a 

group of springs in Oasis Valley and drains southward 

toward the Amargosa DP-sert. The discharge from 

six springs in the alluvial fill adjacent to the flood plain 

of the river, about a mile northeast of Beatty, has long 

been the wa.ter supply for that town (population 500). 

As the fluoride content of this water is about 4.5 parts 

per million, 1nost of the children, the native Indian 

population, and some adults who have resided in the 

commumty since childhood suffer from dental fluorosis. 

Water from wells and other springs along the Amargosa 

River also has high concentrations of fluoride.· 

Most of the Oasis Valley drainage area is underlain 

by Tertiary and QuaGernary volcanic rocks consisting 

of tuff and other pyroclastic rocks, welded tuff, and 

flows (fig. 163.1). Minor amounts of Paleozoic limestone, dolomite, shale, and sandstone make up the rest 

of the bedrock. Quaternary alluvial fill underlies 

about 65 square miles of the valley floor. The alluvial 

fill is saturated with ground water to within a foot or 

two of the land surface and forms the principal groundwater reservoir. 

Virtually all recharge to the alluvial fill is derived 

from precipitation in the drainage basin north and east 

of the Amargosa River and from ground-water underflow through bedrock from beyond the surficial drainage 

area to the north and northeast (Malmberg and Eakin, 

1962). Only a minor amount of recharge is derived 

from infiltration of precipitation on the Bullfrog Hills, 

and virtually no recharge occurs from infiltration of 

precipitation on the valley floor and the low rolling 

hills adjacent to the valley floor. 

Analysis for fluoride and other mineral constituents 

of water samples throughout Oasis Valley indicated 

that ground water beneath the floor of the valley contained up to 5 ppm of fluoPide and that throughout 

most of the drainage area, fluoride concentrations 

exceeded ~ .6 ppm, the safe limit for public water supplies 

that would apply in the Beatty area (U.S. Public 

Health Service, 1962). Moreover, ground-water underflow toward the Amargosa River from the principal 

area of recharge north and east of the river contained 

higher concentrations of fluoride than ground-water 

underflow fl'om the Bullfrog Hills. 

Fluoride in the ground water in Oasis Valley probably 

is derived from weathering of fluorite and fluoridebearing minerals which commonly occur as sublimation 

products associated with volcanic rocks. Chemical 

ART. 136 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D189-Dl91. ,1964. 

D189 
D190 GEOCHEMISTRY OF WATER 

NEVADA 

Area of 

report 

N 

1 1~ ~-~., 

T. 

ll 

S. • 

T. 

12 

S. 

R. 46 E. 

T. 

9 

S. 

R. 47 E. 

R. 48 E. 

R. 49 E 

EXPLANATION 

Quaternary alluvium 

Tertiary and Quaternary 

consolidated rocks of volcanic origin 

Composed pri?IC'ipally ofttiffs 

Paleozoic sedimentary rocks 

Composed pri?IC'ipally of limestone, dolomite, and sandstone 

Fluoride content in ground 

water, in parts per million 

~ 0-1.5 

ct 1.6-3.0 

a 3.1-4.5 

• 4.6-6 

0 

Well 

p 

Spring 

0 2 3 4 5 MILES 

UlUU __ -L--~--L-~-~ 

FIGURE 163.1.-Generalized geologic map of Oasis Valley, Nye County, Nev. Dashed outline enclosing patterned 

area is boundary of that part of the Amargosa River basin in the report area. 

decomposition and subsequent leaching of fluoridebearing minerals disseminated throughout the volcanic 

rocks probably are the major causes of fluoride in the 

ground water in the area. 

The high concentration of fluoride in the water 

samples fron1 the Hot Springs and other thermal springs 

in Oasis Valley suggests that additional fluoride may be 

derived from hydrothermal solutions emanating from 

underlying n1agmatic rocks. All the large springs 

along the flood plain of the Amargosa River issue from 

volcanic rocks or fro;m alluvial fill adjacent to volcanic 

rocks and yield thermal waters of high fluoride content. 

Leaching of lenses and veins of fluorite in carbonate 

rocks exposed in Fluorspar Canyon southeast of Beatty 

undoubtedly accounts for high concentrations of fluoride 

in the ground water downstream from that area. 

Chemical analyses of water fron1 several small 

springs in the unnamed canyon about· a n1ile north of 

Beatty and in Sober-Up Gulch, 4 1niles north of Beatty 

indicated fluoride concentrations of less than 1.5 ppm 

(fig. 163.1). Analyses of water from a few wells in 

Oasis Valley suggested that fluoride concentrations in 

ground water near the base of the Bullfrog Hills is 

generally lower than in other parts of the valley but 
MALMBERG AND EAKIN D191 

increases progressively toward the Amargosa River. 

This led to specific consideration of areas near the 

Bullfrog Hills for a possible supply of low-fluoride 

water. Because ground water in the volcanic rocks 

presumably would have a high fluoride content, only 

areas underlain by alluvium were considered. Accordingly, the alluvial fan at the mouth of the unnamed 

canyon north of Beatty and at the mouth of Sober-Up 

Gulch were considered the n1ost likely places where 

ground-water supplies of relatively low fluoride content 

could be developed. 

The average annual recharge from precipitation in 

the catchment area of each of these basins was estimated to be about 20 acre-feet per year. Although 

there has been some hydrothermal alteration and 

mineral enrichment of the rocks in the Bullfrog Hills, 

underflow in the alluviu1n of these small tributary basins 

is in contact with the volcanic rock for a relatively short 

distance and short time and, consequently, has a minimum opportunity to dissolve fluoride. Furthermore, 

because the ground water in and near the areas of 

recharge is higher than that beneath the valley floor, 

there is little opportunity for deep circulation through 

the consolidated rock and mixing with ground water 

of high fluoride content. Thus, the chemical, geologic, 

and hydrologic data suggest that the alluvial fans at 

the mouth of these two canyons would be the most 

favorable location for developing ground water with a 

low fluoride content. 

Large withdrawals in either of the areas described 

above undoubtedly would cause ground-water levels to 

decline below the water level beneath the floor of Oasis 

Valley, and the resulting reversal of the hydraulic 

gradient would cause movement of water of high fluoride 

content from beneath the valley floor to the area of 

ground-water development. Withdrawals sufficient to 

meet the entire 1nunicipal demand could not be supplied 

entirely from this source on a perennial basis without 

depleting the low-fluoride water in storage and inducing 

inflow of high-fluoride water. I-Iowever, if withdrawals 

in these areas were limited to the drinking-water requirements of the town of Beatty and if pumping was 

carefully managed to minimize drawdown, the low 

fluoride content might be maintained indefinitely. 

Since the publication of the report by l\falmberg and 

Eakin (1962), a test well was drilled in the lower part of 

the alluvial fan at the mouth of the unnamed canyon 

north of Beatty (fig. 163.1). The well produced about 

60 gallons per minute and the fluoride content of the 

water from the test well was 0.04 ppm after 36 hours of 

pumping (W. W. White, Director, Nevada Department 

of Environmental Health, oral communication, 1963). 

The success of the test drilling in locating lowfluoride ground water in this area is a good exam'ple of 

the value of the reconnaissance techniques used in this 

investigation. 

REFERENCES 

Malmberg, G. T., and Eakin, T. E., 1962, Ground-water appraisal 

of Sarcobatus Flat and Oasis Valley, N ye and Esmeralda 

Counties, Nev.: Nevada Dept. Conserv. and Nat. Resources, Ground-Water Resources Reconn. Ser. Rept. 10, 

39 p. 

U .8. Public Health Service, 1962, Drinking water standards: 

Federal Register, March 6, p. 2152-2155. 

Webb, Barbara, and Wilson, Roland, 1962, Progress geologic map 

of Nevada: Nevada Bur. Mines Map 16. 
Article 165 

ENVIRONMENTAL FACTORS AFFECTING ATTACHED MACRO-ORGANISMS, 

PATUXENT RIVER ESTUARY, MARYLAND 

Bv ROBERT L. CORY, Washington, D.C. 

Abstract.-Periodic measurements of water temperature, salinity, and dissolved oxygen content were made at various depths 

during the period October through December 1962. Temperature was found to be the most significant variable affecting the 

growth of the organisms. Four principal organisms attached 

during October and November; growth was rapid in October but 

slight during the other months. 

An algal-tubeworm association, in which a yellow-green alga 

thrived on the waste from tubeworms, was noted and may proye 

useful as an indicatOI of organic pollution. 

A large steam-generating plant at Chalk Point, Md., 

on the Patuxent River, will begin operation in the 

spring of 1964. The plant is expected to discharge 

large amounts of heated water into the estuary which 

at times may be equal to or greater than the total freshwater inflow. To establish a basis for the future understanding of the effect of the heated water on the biota 

the State of Maryland has initiated a comprehensiv~ study of the entire river. Presently over 40 investigators representing State, Federal, and private organizations are studying a wide variety of problems. 

Although the estuary is close to a highly urbanized 

area, there has been little urban develop1nent along its 

shores. The value of oysters, fish, and crabs taken 

from the estuary annually is about half a million dollars, 

and the estuary is known as one of the best oystergrowing areas of the Chesapeake Bay. 

It is believed that any changes occuring in the estuary 

due to the heated water will be reflected in attached 

macro-organisms (chiefly barnacles, bryozoans, tubebuilding amphipods, and tubeworms) and marine borers 

(none were observed during the period reported on here). 

Study of these two types of organisms offers certain 

advantages because a dozen or more species representing 

at least eight phyla can be studied qualitatively and 

quantitatively at one time. Most of the n1ature 

organisms are fixed or only slightly mobile, so they are 

at the mercy of their in1mediate environment. They 

ean be collected from uniform substrates, measured 

areas, and over known lengths of time, thus ruling out 

some of the questionable factors inherent in other 

quantitative biological studies. Preliminary results of 

the Geological Survey investigation, based on observations from October 1962 through March 1963, are 

reported here. 

Two types of test panels, wood, for n1arine borers, and 

asbestos-cement are. to be exposed for periods of 1 

month, 3 months, 1 year, and for the duration of the 

study before and after plant operation begins. The 

wood panels are 260 sq em in area and the asbestoscenlent panels are 290 sq em. At each point of observation one of each type is exposed for the periods indicated. 

The panels are collected and preserved in alcohol, then 

analyzed in the laboratory. 

Monthly and quarterly panels have been set out and 

collected from the surface, middepth, and bottom (7 

meters) at the center of Benedict Bridge; from middepth (2 meters) at the west end of Benedict Bridge; 

and frmn 1niddepth (I meter) at the end of the pier of 

the Chesapeake Biological Laboratory at Solomons 

Island, Md. (fig. 165.1). The Benedict Bridge sampling 

site is in the region of expected high temperatures. The 

Solomons Island site was chosen as a control because it 

will be beyond the effect of unnatural heating. 

Accumulations of marine macro-organisms on the 

monthly panels for Oc.tober and N oven1ber and on the 

quarterly panels for October through December 1962 

were measured and are reported in table 165.3. No 

attachment occurred during the cold months of 

December, January, and February, hence no accumulations are reported. 

ENVIRONMENTAL CHARACTERISTICS 

Water-quality data collected once a n1onth at the 

Benedict Bridge site 1 indicate that ten1perature was 

I Data furnished by the State of Maryland Water Pollution Control Commission. 

Samples were taken at the center of the bridge. 

ART. 165 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D194-D197. 1964. 

D194 
5 

VARIABILITY INDEX 

2-percent chance of deficiency 

VARIAB ILITY INDEX 

! -percent chance of deficiency 

FIGURE 164.1.-Diagrams showing carryover storage requirements for log-normal distributions of 

annual discharge. Variability index is the logarithmic standard deviation of annual discharge. 

Parameter is constant-draft rate in percentage of mean flow. Percentage chance of deficiency 

is the percentage of yea;rs that the indicated reservoir capacity would be insufficient. 

probability routing of t.he actual distribution would be 

required. 

REFERENCES 

Hardison, C. H., and Furness, L. W., 1963, Discussion of "Reservoir Mass Analysis by a Low-Flow Series", by J. B. Stall: 

Am. Soc. Civil Engineers Proc., v. 89, Sanitary Engineering 

Div., Jour.no. SA2, pt. 1, p. 119-122. 

·' 

Lane, E. W., and Lei, Kai, 1950, Stream flow variability: Am. 

Soc. Civil Engineers Trans., v. 115, p. 1084-1134. 

Langbein, W. B., 1958, Queuing theory and water storage: Am. 

Soc. Civil Engineers Proc., v. 84, Hydraulics Div. Jour., 

no. HY 5, pt. 1. 

- -- 1961, Reservoir storage--general solution of a queue 

model: Art. 298 in U.S. Geol. Survey Prof. Paper 424-D, 

p. D13-Dl7. 
Article 165 

ENVIRONMENTAL FACTORS AFFECTING ATTACHED MACRO-ORGANISMS, 

PATUXENT RIVER ESTUARY, MARYLAND 

By ROBERT L. CORY, Washington, D.C. 

Abstract.-Periodic measurements of water temperature, salinity, and dissolved oxygen content were made at various depths 

during the period October through December 1962. Temperature was found to be the most significant variable affecting the 

growth of the organisms. Four principal organisms attached 

during October and November; growth was rapid in October but 

slight during the other months. 

An algal-tubeworm association, in which a yellow-green alga 

thrived on the waste from tubeworms, was noted and may proye 

useful as an indicator of organic pollution. 

A large steam-generating plant at Chalk Point, Md., 

on the Patuxent River, will begin operation in the 

spring of 1964. The plant is expected to discharge 

large amounts of heated water into the estuary which 

at times may be equal to or greater than the total freshwater inflow. To establish a basis for the future understanding of the effect of the heated water on the biota 

the State of Maryland has initiated a comprehensiv~ 

study of the entire river. Presently over 40 investigators representing State, Federal, and private organizations are studying a wide variety of problems. 

Although the estuary is close to a highly urbanized 

area, there has been little urban development along its 

shores. The value of oysters, fish, and crabs taken 

from the estuary annually is about half a million dollars, 

and the estuary is known as one of the best oystergrowing areas of the Chesapeake Bay. 

It is believed that any changes occuring in the estuary 

due to the heated water will be reflected in attached 

macro-organisms (chiefly barnacles, bryozoans, tubebuilding amphipods, and tubeworms) and marine borers 

(none were observed during the period reported on here). 

Study of these two types of organisms offers certain 

advantages because a dozen or more species representing 

at least eight phyla can be studied qualitatively and 

quantitatively at one time. Most of the mature 

organisms are fixed or only slightly mobile, so they are 

at the mercy of their immediate environment. They 

can be collected from uniform substrates, measured 

areas, and over known lengths of time, thus ruling out 

some of the questionable factors inherent in other 

quantitative biological studies. Preliminary results of 

the Geological Survey investigation, based on observations from October 1962 through March 1963, are 

reported here. 

Two types of test panels, wood, for marine borers, and 

asbestos-cement are , to be exposed for periods of 1 

month, 3 months, 1 year, and for the duration of the 

study before and after plant operation begins. The 

wood panels are 260 sq em in area and the asbestoscement panels are 290 sq em. At each point of observation one of each type is exposed for the periods indicated. 

The panels are collected and preserved in alcohol, then 

analyzed in the laboratory. 

Monthly and quarterly panels have been set out and 

collected from the surface, middepth, and bottom (7 

meters) at the center of Benedict Bridge; from middepth (2 meters) at the west end of Benedict Bridge; 

and from middepth (1 meter) at the end of the pier of 

the Chesapeake Biological Laboratory at Solomons 

Island, Md. (fig. 165.1). The Benedict Bridge sampling 

site is in the region of expected high temperatures. The 

Solomons Island site was chosen as a control because it 

will be beyond the effect of unnatural heating. 

Accumulations of marine macro-organisms on the 

monthly panels for October and November and on the 

quarterly panels for October through December 1962 

were measured and are reported in table 165.3. No 

attachment occurred during the cold months of 

December, January, and February, hence no accumulations are reported. 

ENVIRONMENTAL CHARACTERISTICS 

Water-quality data collected once a month at the 

Benedict Bridge site 1 indicate that temperature was 

'Data furnished by the State of Maryland Water Pollution Control Commission. 

Samples were taken at the center of the bridge. 

ART. 165 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D194-D197. 1964. 

D194 
CORY D195 

38° 

30' 

38 ° 

20' 

"<; ~ 

0 5 MILES 

~~ Solomons Island L__ _ __ ______J 

FIGURE 165.1.-Index map of Patuxent River estuary. 

the most significant variable during the period of observations (October 1962 through February 1963). Temperatures decreased from a high of about 21.5 °C in 

October 1962 (fig. 165.2) to a low of 0°C in January 

1963. Salinity at the bridge was generally between 12 

and 17 parts per thousand, and vertical variations were 

slight. However, the sampling program does not take 

into account the short-term variations caused by local 

weather changes and daily tidal fluctuations. Dissolved 

oxygen gradually increased as the temperature decreased and was high enough to support aquatic life 

throughout the period. 

Continuous recordings of temperature and daily 

salinity readings have been taken since 1938 at the 

laboratory pier at Solomons Island. 2 During the study 

reported here, the mean daily surface temperatures 

gradually decreased from a high of 21 oc in October 

1962 to a low of 0.5°0 when the quarterly panels were 

collected. Salinity ranged from 14.8 to 17.3 ppt duri ng 

the same period. 

DISTRIBUTION O·F ORGANISMS 

The density of the principal attached macroorganisms is shown in figure 165.3. Note, however, 

that the number of bryozoan colonies, rather than 

individuals, is shown, and that the number of oro·a- • b 

msms does not indicate the total mass contributed by 

each group. Microscopic organisms also covered 

much of the surface of the panels. These forms added 

2 Data furnished by the Chesapeake Biological Laboratory, Solomons Island, Md . 

Benedict Bridge Solomons Island 

"' "' "' "' "' llD llD llD llD llD "' llD 

"' "' e "' "' "' 0; 0; "' 0; 0; 0; > > > > > > .<:: .<:: :S "' "' "' "' "' "' "' a. "' a. "' ::::: ~ ::::: ~ 

::::: ;;; u E E 0. E "' "' "' u "' u "' :S :S "' :S "' "' 'C 0 -t 'C 0 "' 'C § "' ,., ,., 't: 'C :1: ~ 't: c ,., c c ~ ~ ' I I ::J 0 ::J ::J 0 0 ,., 0 ,., 0 "' (/) :2 co (/) :2 co (/) :2 a:l :2 N :2 N :2 N 

TEMPERATURE 

30r---~---,----,----,---,-----, 

0::0 

~ ~ 20 (/)(/) 

>--"' 

~ ~ 10 0..1--

SALINITY 

I J 

DISSOLVED OXYGEN 

FIG URE 165.2.- Monthly temperature, salinity, and dissolved 

oxygen content of water of Patuxent River estuary at Solomons Island and Benedict Bridge, October- December, 1962. *Data 

questionable. 

little to the total mass but arR important in forming 

microscopic substrates, which often precede attachment of the larger forms. 

Attachment by marine macro-organisms occurred 

only during October and November-no macro-organisms attached to monthly test panels during December, 

January, or February. During October, barna~les, 

tubeworms, tube-building amphipods, and colonial 

bryozoans dominated the complex. At Benedict 

Bridge, barnacles were the dominant form during 

October and increased during November (fig. 165.3). 

At Solomons Island mud tubeworms were dominant 

in October and bryozoans in November. At Benedict 

Bridge, where test panels were placed at three depths, 

the populations varied with depth (fig. 165.3). 

The quarterly panels (October-December) for Benedict Bridge showed about the same organisms as the 

October panels, but those at Solomons Island did not 

have tubeworms and arnphipods, which were attached 

to the October panels. Bryozoans were prominent and 

covered large areas of the panels, although the number 

of colonies was small. They were the dominant form 
DI96 MARINE HYDROLOGY 

Benedict Bridge Solomons Island 

Center I West 

end 

.c .s .s .c .c .s .c ., a. .. .. a. E ., Cl E Cl E Cl Cl Cl u ., u . ., ., ., ., ., ., ~ " 0 ~ " 0 " 0 

~ " " " " :: ~ :: ~ :> 0 :> 0 :: 

0 ~ ~ ~ ~ (/) ::!: !D (/) ::!: !D ::!: !D ~ ~ ~ ~ 

30,------,------,---.---~----,---,--------, 

20 

None 

ENCRUSTING BRYOZOAN COLONIES 

AMPHIPOD TUBES 

a:: 

LLJ 

~ 

LLJ 200 ~ 

u 

LLJ 

0 150 

LLJ 

a:: None None None 4( 100 :::> 

0 

(/) 

a:: 50 LLJ 

ll. 

a:: 0 LLJ 

!D TUBEWORMS 

~ 800 :::> 

z 

700 

600 

500 

400 

300 

200 

100 

0 I~ I J i 

' : ~ 

11!11 ... BARNACLES 

FIGURE 165.3.-Density of principal attachment organisms 

collected on test panels at Benedict Bridge and Solomons 

Island, October- December, 1962. 

· at Solomons Island, where a single colony covered an 

area :>f 961 square millimeters. Many young barnacles 

were overgrown and killed by these bryozoan encrustations . 

GROWTH 

Even though attachment of new individuals ceased 

after November, the quarterly panels indicate 

that total accumulations of the organisms continued. 

Gravid tubeworms and their eggs were present, amphipods were active on freshly collected panels, and 

new growth by the bryozoan colonies could be observed--evidence that all of these forms were still quite 

active when the panels were collected. 

Measurements of barnacle basal areas on the monthly 

panels show that growth of individuals was vigorous 

during October, diminished greatly in November, and 

was negligible the remainder of the winter. The 

growth varied both with depth and location. (See 

table 165.1.) Maximum sizes were attained at Solomons Island. 

The mean basal-area data are somewhat misleading. 

For example, although the October value for the bottom 

at Benediet Bridge is less tha.1 at middepth and surface, this panel not only had a great many more barnacles than those at the other two depths, but many 

appeared to have attached a day or two before collection. This difficult.y is inherent in a monthly datacollecting program and can only be resolved by more 

frequent observations. Also, the high mean basal 

area for the Solomons Island quarterly panel was 

based on measurement of only 10 individuals, the total 

number on the panel. Note the large differences 

betwee11 mean and maximum basal areas for the quarterly and monthly panels. A probable explanation for 

this is that. t.he organisms that attach the earliest have 

the advantage in gathering food and utilizing space. 

By the end of October all available space was occupied ; 

TABLE 165.1.-Basal area of barnacles 

[Rostrocarlnal-lateral measurements] 

Sampling site 

Mean basal area (square millimeters) 

Maximum basal area (square millimeters) 

Oct. Nov. Oct.- Oct. Nov. Oct.- Dec. Dec . 

---------1------------------

(1) 5. 28 0.38 (1) 

4.92 13.81 . 49 16. 49 

5.18 10.11 . 69 42.88 

Benedict Bridge, center: Surface. .......... ......... . 1. 25 0. 22 

Middepth.......... ........ 1. 52 . 31 

Bottom (7 meters).......... . 88 . 44 

5. 54 -------- -------- 28.59 

20.04 11. 31 .94 45.43 

Benedict Bridge, west side (2 

meters) ...... --------······--- -·----·· -······· Solomons Island (1 meter).... . . 1. 66 . 43 

1 Panel scoured by ice. 
CORY D197 

therefore, the size measurements are representative of 

individuals that attached during that month. Barnacle growth was slight in November and December. 

The mean basal area of barnacles on a special panel 

exposed for growth studies at middepth at Benedict 

Bridge from November 8 to March 8 was only 0.65 

square millimeters as compared to a mean basal area 

of 4.92 square mm for barnacles on the panel exposed 

from October through December (table 165.1) 

Attachment and growth of the colonial bryozoans 

also varied with depth and location. Unlike barnacles, 

_they grew actively in the colder winter water, and newly 

formed zooecia were observed on the colonies when the 

quarterly panels were collected. Mean and maximum 

areas of bryozoan colonies were considerably less at 

Benedict Bridge than at Solomons Island on both the 

monthly and quarterly panels (table 165.2). For some 

unknown reason, attachment and growth were less 

at middepth at the center of the bridge than at the 

surface or bottom. 

TABLE 165.2.-Area of bryozoan colonies, autum and winter, 1.962 

Sampling site 

Mean area (square millimeters) Maximum area (square millimeters) 

Oct. Nov. Oct.- Oct. Nov. Oct.- Dec. Dec. 

---------1------------------

Benedict Bridge, center: Surface_---------------_____ 6. DO 

Middepth__________________ 3. 92 Bottom (7 meters)__ ________ 6.80 

Benedict Bridge, west side (2 meters) ____________ _________ __ -------- -------- Solomons Island (1 meter)______ 40.5 _______ _ 

181.8 

98.96 

182.4 

120.6 

297. 1 

31.4 -------- 4.1 -------- 21.2 -- ------

380.2 9. 4 

WEIGHT OF ORGANIC MATERIAL 

282.8 

201.0 

282.8 

320.5 

961.1 

The weight of organic carbon (dry, minus ash weight) 

produced by the attachment organisms varied with 

time, depth, and location (table 165.3). In order to 

obtain a figure to compare the standing crop at each 

location regardless of species, whether shelled or nonshelled, the material was scraped from the wooden 

panels, oven dried, weighed, ashed at 500°0, and 

reweighed. The weight was slight in November, 

compared to October, and negligible from December 

through February. Organic weight on the quarterly 

panels was highest at the bottom at Benedict Bridge 

and lowest at Solomons Island. Variations in organic 

weight undoubtedly reflect the relative abundance of 

the various species involved; however, measurements 

of single groups were not made. 

TABLE 165.3.-Comparison of dry and organic weights, autumn 

and winter, 1962 

Total Organic 

dry Ash matter Expoweight sure of 

Sampling site panel 

I I 

(days) 

gfm2 g/m' Per- g/m2 Per- cent cent 

October 

Benedict Bridge, center: Surface___________________ __ 9. 3 7. 08 76.1 2. 22 23.9 30 

Middepth_ _________________ 19.7 15.22 77.4 4. 48 22.6 30 Bottom (7meters) __ _____ ___ 25.05 15.34 61.1 9. 7 38.9 30 

Solomons Island (1 meter)______ 4. 72 3.17 67.1 1. 55 32.9 30 

November 

Benedict Bridge, center: Surface. ______________ -_---_ 2. 99 2.13 71.2 0. 86 28.8 30 

Middepth _________ __ _____ __ 2. 46 1. 67 68.0 . 79 32.0 30 Bottom (7 meters) ____ ___ ___ 1. 98 1. 45 73.4 . 53 26.6 30 

Solomons Island (1 meter) ______ (1J (1) (1J (') (1) 30 

October-December 

Benedict Bridge, center: Surface. _____________ ------- (2) (2) (2) (2) (') 88· 

M!ddepth ________________ __ 117.36 91.56 78.0 25.80 22.0 88 Bottom (7 meters) __________ 248.78 170.35 68.5 78.43 31.5 88 

Benedict Bndge, west side (2 meters) 93 ____________ __ _________ 114.67 73.45 64.1 41.22 35.9 

Solomons Island (1 meter) ______ 49. 92 31.09 62. 4 18.83 37.6 88 

1 Weight negligible. ' Panel scoured by Ice. 

ALGAE AND TUBEWORM ASSOCIATION 

The quarterly panel from the west side of Benedict 

Bridge showed an interesting association between the 

tubeworms and a yellow-green alga. Prominent tufts 

of the alga, 8-12 mm long, were scattered over the 

panel. Close examination revealed that these tufts 

were located at the anal end of the worm tubes. The 

algae appeared to profit from the organic enrichment 

of the water at this location. This relationship suggests that algae of this type may prove to be a useful 

indicator of other types of organic pollution. 
Article 166 

ANOMALOUS STREAMFLOW-GROUND-WATER REGIMEN 

IN THE MAD RIVER BASIN, NEAR SPRINGFIELD, OHIO 

By WILLIAM P. CROSS and ALVIN J. FEULNER, 

Columbus, Ohio, and Anchorage, Alaska 

Work done in cooperation with the Ohio Department of Natural Resources, Division of Water 

Abstract.-Streamflow measurements of the Mad River downstream from Springfield to the mouth of Mud Run indicated a 

loss in flow in this reach . Precise measurements of ground-water 

levels showed that ground-water flow had been diverted by 

drainage ditches, thereby reversing the normal ground-water 

gradient. 

The Mad River, in west-central Ohio, has the best 

sustained dry-weather flow of any major stream in the 

State, a situation indicative of large potential groundwater supplies in the basin. Because widespread and 

thick permeable gravels underlie most of the Mad 

River valley the river is an effluent, or gaining, stream 

throughout most of its length. However, spot measurements of streamflow indicated that, at least at some 

times under dry-weather conditions, there was a loss in 

flow downstream from Springfield. This anomaly suggested that for some reason the yield of aquifers in that 

reach was lower than would be expected from the 

known hydrogeology. As ground-water withdrawals, 

recharged by infiltration from the river, were being increased in both the Springfield and Dayton areas, an 

investigation was made during 1959 and 1960 with the 

purpose of accounting for the loss in streamflow. 

The Mad River rises on the eastern side of the Bellefontaine outlier, a bedrock high in Logan County, the 

highest terrain in the State. The river flows southward 

across Champaign and northern Clark Counties over a 

gravel-filled buried valley as much as 3 miles wide. At 

Springfield the valley fill is constricted by a bedrock 

gorge approximately }~ mile wide. The drainage area 

above the stream-gaging station west of Springfield, at 

the lower end of the gorge, is 485 square miles. Downstream from Springfield the river flows west-southwest 

across a gravel-filled valley as much as 2 miles wide in 

Clark County and the northwestern corner of Greene 

County. Near the boundary between Greene and 

Montgomery Counties the river enters a second constriction, a bedrock gorge at Huffman Dam, one of five 

flood-control dams of the Miami Conservancy District. 

The dam forms a dry detention-type reservoir, and does 

not affect low and medium stages of flow. Between 

Huffman Dam and the mouth of the river at Dayton, 

the Mad River again flows over a gravel-filled valley. 

The drainage area above the gage just downstream from 

Huffman Dam is 632 square miles. Figure 166.1 shows 

the main features of the drainage basin and the inferred 

direction of ground-water movement. 

Except at the two gorge sections, the Mad River 

valley is underlain by large volumes of highly permeable gravels. Some of this highly permeable material 

is hydraulically connected to the stream, and as the 

hydraulic gradient is toward the stream, large inflows 

are contributed to the river. A series of fiow measurements along such a stream, called a seepage investigation or seepage run, reveals the zones of ground-water 

contribution by showing large increases in flow between 

measuring points. Lack of gains indicated by the 

meMurements does not eliminate the possibility that 

permeable water-bearing deposits are separated from 

the stream by relatively impermeable material or that 

the hydraulic gradient is not toward the stream. It 

was such a lack of gains in a seepage investigation in 

September 1948 that focused attention on the reach 

downstream from Springfield. 

The glacial features of the Mad River valley in 

Clark County have been described by Goldthwait 

ART. 166 IN U.S. GEOL. SURVEY PROF. PAPER 475-0, PAGES 0198-0201. 1964. 

Dl98 
CROSS AND FEULNER D199 

N 

0 10 MILES 

FIGURE 166.1.-Mad River drainage basin and inferred direction 

of ground-water movement (arrows) in the basin. 

(Norris and others, 1952, p. 44-51), and those of 

Greene County by Norris and others (1950, p. 13-19). 

In its upper reaches the Mad River flows over a buried valley filled with sediments deposited in an interlobate zone between the Scioto (east) and the Miami 

(west) lobes of the Wisconsin glacier. This valley fill 

consists largely of permeable sand and gravel lain down 

as kames, kame terraces, high-level outwash, and valley-train deposits. The gorge through which the stream 

passes at Springfield is cut in limestone. This gorge, 

as well as the one which cuts through limestone and 

shale at Huffman Dam, has relatively impermeable 

bedrock walls. Downstream from each of the gorges 

the buried valley again widens, and is filled with highly 

permeable glaciofluvial deposits. 

Estimates of the permeability of the gravel deposits 

both upstrea1n and downstream from the Springfield 

gaging station have been made at various times. An 

average for the pern1eability of all gravel deposits in 

the Mad River valley is between 2,500 and 4,000 gallons per day per square foot. This high value is in 

marked contrast to that of the relatively imper1neable 

limestone and shale that form the valley walls in the 

two gorge sections. Walton and Scudder (1960, p. 38) 

estimate that the anwunt of water passing through 

the bedrock constriction as underflow beneath Huffman Dam is about 0.6 million gallons per day. The 

ungaged underflow at the gage near Springfield probably 

is less than this figure. 

On the basis of extensive stream gaging at many 

selected locations during a period of low flow in September 1948, it is estimated that additions of ground 

water to the Mad River in Champaign County exceed 

1 mgd per day per mile of stream. Farther south, in 

Clark County, more than 2 mgd per mile of stream was 

added during this low-flow period. Cross (1949, p. 563) 

estimated the amount of water stored in the gravel deposits contributing to streamflow north of t:h~ Sprin?-

field gaging station to be ·as much as 2 to 3 bllhon cubw 

feet (15 to 22 billion gallons). 

The following low-flow measurements were made on 

September 15, 1948, west of Springfield: 204 cubic feet 

per second at the gage near Springfield, 191 cfs at 

Spangler Road (B-B', figs. 166.1 and 166.2), and 201 

cfs at the gage downstream from Huffman Dam (Mad 

River near Dayton) (Norris, and others, 1952, p. 29). 

Because of the limitations in the accuracy of currentmeter measurements, the flow loss in this reach cannot 

be reliably determined, but there undoubtedly was some 

loss. Flow-duration curves for the two stations indicate that on the average there are no losses, even at 

extreme low flows (Norris and others, 1952, p. 26). 

Increases in flow between Springfield and Dayton are 

less than the contributions north of Springfield, but generally they are substantial. The low flow at Midway 

(Spangler Road) suggested that the river was losing 

water within this area, and to study this condition the 

U.S. Geological Survey and the Division of Water, Ohio 

Department of Nat ural Resources, cooperated in constructinO' 18 observation wells, leveling to the wells, b •• 

making observations of water levels, and obta1n1ng 

streamflow measurements. All the observation wells 

except four, which are near the Springfield gaging station are shown on figure 166.2. The wells averaged 

abo~t 18 feet in depth, and the screened portion of the 

casing was placed in gravel deposits below the normal 

water level in the area. The holes were drilled along 

two cross-section lines, extending to both sides of the 

Mad River. Elevations of ground surface and measuring points were determined by a level traverse, including elevations of measuring points at four stream crossings. Twelve sets of well observations and four sets 

of strean1flow measurements were made during 1959 

and 1960. Two of the sets of observations are illustrated in the cross sections of figure 166.3. '1'hese are 

for May 21, 1959, when the flow in the river was about 

the mean, and for .August 25, 1959, when the water 

levels were at the lowest point during the period of 

observation. The other 10 sets of observations are 
D200 SURFACE WATER 

MAD RIVER NEAR SPRINGFIELD GAG£. 2.5 MILES 

SPANGLER ROAD 

ENON ROAD A' 

SECTION 

--~~~OUNTY GREENE COUNTy 7 

0 1 MILE 

FIGURE 166.2.-Map of the Mad River basin south of Springfield, 

showing observation-well locations. 

LLI 

> 

~ 850 

<( 

ILL! 

LLI 

u.. 

z 

0 

i= 

<( 

> LLI 

~ 830 

B 

Mud 

Run 

I 

Warden 

Ditch 

I 

ENON ROAD SECTION 

R~vc:! B' 

I Grourt surface 

Water level in wells May 21, 195 

\Water level in wells Aug. 25, 1959 

Stream level and water level in 

wells approximately equal 

SPANGLER ROAD SECTION 

DISTANCE, IN MILES, FROM MAD RIVER 

FIGURE 166.3.-Cross sections of the Mad River valley southwest of Springfield, showing water levels on May 21 and 

August 25, 1959. 

intermediate between the two extremes shown, but have 

the same general shape in cross section. 

The reason for the losses in the reach of the Mad 

River from Springfield to Huffman Dam is apparent 

from figure 166.3. The low area south of the river 

must have been very swampy in earlier times as the 

topographic map surveyed in 1904 shows an extensive 

system of drainage ditches. The map surveyed in 1955 

shows that the channel now called Warden Ditch had 

been deepened and its drainage area more than doubled 

by capture of the upstream ends of other ditches between 1904 and 1955. As the ditches are lower than 

the river bottom, and the gravels of the valley fill are 

highly permeable, the direction of ground-water flow is 

from north to south, under the river, to Warden Ditch, 

which flows into the river above Huffman Dam. There 

is no indication of ground-water flow out of the drainage 

basin to the Little Miami River tributaries to the south. 

The accompanying table confirms these conclusions by 

indicating a loss (a slight gain occurred on August 30, 

1960) between the Springfield gage and Spangler Road 

which is recovered at the Huffman Dam gage (Mad 

River near Dayton). Thus the Mad River is an 

influent or losing stream for all stages up to the mean, 

in the reach between Springfield and the mouth of 

Warden Ditch. 

Streamflow measurements for the Mad River between Springfield 

and Dayton, Ohio, 1959 and 1960 

Discharge (cfs) 

Drainage Location on Mad River area 1959 1960 

(sq mi) 

May21 Aug. 25 Aug. 30 Oct. 6 

------------

Near Springfield (gage) ____ 485 462 216 166 166 

Enon Road ______________ 492 ------ 217 ------ ------ Spangler Road ___________ 539 ------ 214 171 157 

Near Dayton (gage) ______ 632 670 263 195 184 

The investigation illustrates the one-sided nature of 

a seepage run as a reconnaissance tool for locating 

potential ground-water supplies. Analogous to the 

null hypothesis of statistics, the hypothesis of potential 

ground-water supplies may be accepted if there is gain 

in the seepage run. On the other hand, in the event of 

a lack of gain, additional information is needed before a 

decision can be made. In this specific situation, the 

potential ground-water yield was there, but gains were 

not measured in the reach because the hydraulic 

gradient had been reversed locally, perhaps inadvertently, by drainage ditches. 

REFERENCES 

Cross, W. P., 1949, The relation of geology to dry-weather streamflow in Ohio: Trans. Am. Geophysical Union, v. 30, p. 563-

566. 

Kaser, Paul, 1962, Ground-water levels in the vicinity of Eagle 

City, Clark County, Ohio: Ohio Dept. Nat. Resources, Div. 

Water, Report to Ohio Water Commission, p. 1-82. 

Norris, S. E., Cross, W. P., and Goldthwait, R. P., 1950, The 

Water Resources of Greene County, Ohio: Ohio Dept. Nat. 

Resources, Div. Water Bull. 19, p. 1-52. 
CROSS AND FEULNER D201 

Norris, S. E. and others, 1952, The Water Resources of Clark 

County, Ohio: Ohio Dept. Nat. Resources, Div. Water 

Bull. 22, p. 1-82. 

Walton, W. C., and Scudder, G. D., 1960, Ground-water resources 

of the valley-train deposits in the Fairborn area, Ohio: Ohio 

Dept. Nat. Resources, Div. Water Tech. Rept. 3, p. 1-51. 
Article 167 

HEIGHT-FREQUENCY RELATIONS FOR NEW JERSEY FLOODS 

Bv D. M. THOMAS, Trenton, N.j. 

Abstract.-Regional relations among height, discharge, and 

frequency are defined for New Jersey floods having annual 

recurrence intervals of 1.5 to 50 years. Separate relations are 

shown for Coastal Plain and non-Coastal Plain streams, and they 

can be used to predict flood heights at sites where mean annual 

flood discharge is known or can be estimated. 

Regional relations among height, discharge, and frequency have been defined for New Jersey floods. These 

relations, which were developed from a study of streamgaging station records, can be used to predict flood 

heights at sites where mean annual flood discharge is 

known or can be estimated. The relations are similar 

to the depth-discharge-frequency relations found by 

Leopold and Maddock (1953). 

Leopold and Maddock (1953) determined for less 

than bankfull streamflow that a basin-wide relation 

exists between stream depth and discharge when discharge is of equal frequency of occurrence at all sites. 

They showed this relation as a simple power function 

of the form d=c Q', where d is average cross-section 

depth, Q is discharge of a given frequency at the section, 

and c andj are constants for a given frequency. 

The simple power function also proved satisfactory 

for defining the New Jersey flood relations. However, 

for ease of field application, different measures of the 

two variables were used. Flood height (h) was used 

rather than average cross-section depth (d) because it is 

simply measured as a vertical distance. Flood height 

is defined as height of the water surface above the 

average channel bottom detern1ined at time of median 

(50-percent duration) discharge. Mean annual flood 

discharge ( Q2.33) was found to be a satisfactory index of 

flood sizes for the desired flood-frequency range, and it 

was used for all frequencies rather than actual discharge (Q). With these variables the equation of the 

New Jersey flood height-frequency relations is h=cQr2.33. 

Records of 46 stream-gaging stations were used to 

define the flood-height-frequency relations by evaluating the c and f constants for annual flood recurrence 

intervals of 1.5 to 50 years. These gaging stations, 

which have mean annual flood discharges ranging from 

117 to 140,000 cubic feet per second, are located at sites 

where natural flood flows and flood heights could be 

determined. Thirteen of the gaging stations are in the 

Coastal Plain physiographic province of southern New 

Jersey. Different c values were determined for these 

gaging stations than for the gaging stations outside the 

Coastal Plain. For the Coastal Plain, c ranged from 

0.49 for a 1.5-year flood to 1.35 for a 50-year flood, while 

for the non-Coastal Plain sites c ranged from 0.33 for a 

1.5-year flood to 0.90 for a 50-year flood. Thef values 

for both Coastal Plain and non-Coastal Plain sites 

ranged from 0.360 for a 1.5-year flood to 0.314 for a 

50-year flood. Figures 167.1 and 167.2 show graphically the defined relations. 

Accuracy of the defined relations was checked by 

using them to estimate flood heights at the 46 gaging 

stations and comparing the estimated and measured 

values. As a check on the accuracies expected at 

ungaged sites, the flood heights were estimated using 

mean annual flood discharges computed from drainagebasin characteristics by preliminary methods developed 

in another study. Two out of three estimates at 

gaging stations agreed with measured flood heights 

within ±23 percent for a 2.33-year flood, within 

± 16 percent for both a 10-year and a 25-year flood, 

and within ±21 percent for a 50-year flood. Maximum errors for a 2.33-year flood were +54 percent and 

-47 percent, a~d maxirnum errors for a 50-year flood 

were +36 percent and -49 percent. No significant 

accuracy differences appeared between estimates for 

Coastal Plain and non-Coastal Plain streams. 

ART. 167 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D202-D203. 1964. 

D202 
1-

LI..I 

LI.J 

~ 

II 

(.!) 

iii 

I 

0 

0 

0 

...J 

~ 

1-

LI..I 

LI.J 

~ 

~ 

II 

THOMAS D203 

(.!) 10 f-----------~----- ~ 

iii 

I 

0 

0 

0 

...J 

~ 

RECURRENCE 

INTERVAL, IN 

YEARS 

2L--~ _ _L_~~_LJ_~-----L--~-_L_L_~~~LJ ____ _L __ ~-~~-L-L-~-L-------

200 1000 10,000 100,000 200,000 

MEAN ANNUAL FLOOD DISCHARGE, IN CUBIC FEET PER SECOND 

FIGURE 167.1.-Flood height-discharge-frequency relations for non-Coastal Plain streams in New Jersey. 

RECURRENCE 

Although flood heights estimated by the areal relations are considered less reliable than those obtained 

from field surveys and hydraulic computations, the 

ease and simplicity of their determination are expected 

to make them useful for many purposes. 

REFERENCE 

Leopold, Luna B., and Maddock, Thomas, Jr., 1953, The 

hydraulic geometry of stream channels and some physiographic implications: U.S. Geol. Survey Prof. Paper 252. 

2L-___ _L __ ~_L__L~~_L_L~---~--~ 

100 1000 3000 

MEAN ANNUAL FLOOD DISCHARGE, IN CUBIC FEET PER SECOND 

FIGURE 167.2.-Flood height-discharge-frequency relations for 

Coastal Plain streams in New Jersey. 

716-626 0~64--14 
Article ·168 

SEASONAL TEMPERATURE FLUCTUATIONS IN SURFICIAL SAND 

NEAR ALBANY, NEW YORK 

By RALPH C. HEATH, Albany, N.Y. 

Work done in cooperation with the 

New York Water Resources Commission 

Abstract.-Subsurface temperature fluctuations are due to 

thermal waves that originate at the land surface in response to 

changes in air temperature. The annual average temperature 

of the zone of saturation, 6 to 18 feet below land surface, is about 

3°F higher than the annual average air temperature. 

The temperature of ground water at the top of the 

zone of saturation in most places corresponds closely 

to the mean annual air temperature. Collins (1925) 

pointed out that the temperature of ground water between depths of 30 and 60 feet is generally 2 °F to 3 °F 

above the mean annual aJr temperature. The temperature of shallow ground water under natural conditions 

is affected by (1) air temperature, (2) character of the 

land surface and ground cover (Pluhowski and Kantrowitz, 1963), (3) thermal conductivity of the zone of 

aeration, (4) temperature of recharge reaching the zone 

of saturation, and (5) heat from the earth's interior. 

Of these, the first three are the most important. The 

tern p·erature of recharge generally has a significant effect 

only where the water table is relatively close to the 

land surface or where the zone of aeration is composed 

of highly permeable material. Heat from the earth's 

interior increases the temperature of ground water approximately 1 °F for each 65 feet of increase in depth 

in northern New York. The effect of the earth's heat 

on the temperature of shallow ground water cannot be 

determined until the direct and indirect effects of the 

other factors are better known. 

A study of the seasonal fluctuation of soil and groundwater temperatures was started in July 1959 in a residential area in the unincorporated village of McKnownville, N.Y., a suburb just west of Albany. The land 

surface is a gently rolling plain covered principally by 

grass and scattered trees. The surficial deposit, about 

20 feet thick, consists of fine to medium sand and 

mantles a series of interbedded silts and clays approximately 100 feet thick. The sand layer contains water 

under unconfined conditions. Because the sand is 

stratified, its horizontal permeability is substantially 

greater than its vertical permeability. 

Temperatures were measured at 5 levels within the 

surficial sand: 2 in the zone of aeration, and 3 in the 

zone of saturation. Temperature measurements were 

made in the zone of aeration with indoor-outdoor 

thermometers having steel-encased fluid· reservoirs 

buried at 1.5 and 3 feet. The temperature within the 

zone of saturation was measured at depths of 6.4, 11.1, 

and 17.7 feet below land surface in 3 wells driven to 

depths of 8, 13, and 20 feet, respectively. The bulbs 

of the thermometers were imbedded in sand in the 

lower part of small open glass bottles that were left 

submerged between temperature readings. 

Two homes are located about 50 feet downgradient 

from the temperature-measurement site, and several 

others are within a few hundred feet downgradient. 

Other homes are located 100 to 200 feet upgrttdient. 

All domestic wastes from these homes, except those 

originating in the bathrooms, are disposed of through 

sewers. Bathroom wastes are disposed of through 

septic tanks, the nearest of which is 32 feet downgradient from the site. 

The data collected during 1960 at the temperaturemeasurement site are sumn1arized in the accompanying 

table. Also summarized in the table are the air temperatures measured by the U.S. Weather Bureau station 

at the Albany, N.Y., airport, 5 miles to the northeast. 

As the snow cover during the winter of 1959-60 was 

,ART. 168 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D204,..D208. 1964. 

D204 
HEATH D205 

Summary of monthly air and subsurface temperatures, 1960, in 

degrees Fahrenheit 

Monthly average Monthly average maximum tempera- minimum tempera- Range in ture ture monthly Annual 

Measuring point l-----,---l------,,.----l average average tempera- temper- Tern- Tern- tures ature Month pera- Month pera- ture ture 

------·1-----1---1----11----------

Air, at a height of July--------- 1 80.6 January___ 1 14.9 5 feet. 

Subsurface, at indicated depth (feet): 1.5______________ August__ ___ _ 3.0 ___________________ do ______ _ 

6.4______________ September __ ll.L____________ October_ ___ _ 

17.7------------- November __ 

2 70 ___ do _______ 

2 69 March ____ 

59.5 ___ do _______ 

55.9 ApriL ____ 

53.1 May ______ 

1 U.S. Weather Bureau station at Albany, N.Y., airport. 2 Record incomplete. 3 November 1959 to October 1960. 

27 

35 

43.2 

46.4 

49.5 

46.8 48.6 

43 48 34 52 16.3 51.5 3 9. 5 3 51.3 

3.6 51.3 

thin, and so did not have a detectable effect on subsurface temperatures, no data on it are included in the 

table. 

0 

80 

Each measurement of subsurface temperature made 

during the period July 1, 1959, to December 31, 1960, 

is plotted in the upper graph on figure 168.1. Also 

plotted in the upper graph are the monthly average 

maximum air temperatures and the monthly average 

minimum air temperatures. Measurements of the 

depth to water in the well used for making temperature 

measurements at a depth of 11.1 feet are plotted in the 

lower graph in figure 168.1. 

Subsurface temperatures respond principally to 

temperature waves originating at the land surface in 

response to changes in air temperature. There are at 

least three waves of different period and amplitude. 

The depth of penetration of the waves is proportional 

to their period, and the magnitude of the subsurface 

temperature fluctuations is proportional to both the 

amplitude and the period of the waves and to the 

thermal diffusivity of the subsurface materials. The 

shortest waves are generated by diurnal changes in air 

0 0 

0 Monthly maximum air temperature _-0 

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Water temperature at 6.4 ft 0 

50 

Water temperature at 17.7 f~ {'\\. ';· ·b 

;! i~ .\ ._. 

. . . ·.:-: . ~ · · .,.......-So1l temperature at 3.0 ft . ;I 

Soil temperature at 1.5 ft .!'\ . . .· .: I• 

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·,\ -- .i o . tA '"'-· (\ ... \i .. ;·-!-.'\ .. :· -.\ .i-· . \ . . 

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30 • 

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3.0 r4.0 fr5.0 r-

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Water level in well 13 ft deep 

6.0 r- ····,· ....... 

f7.0 r-

·-, .,..., ....... . 

I I ;·"·""-··/1 

July Aug. Sept. Oct. Nov. 

1959 

• 

I I I I I 

.·-- ~ ..... _,."'* .... ·- ........... ~-

/ 

I I I l I I I 

Dec. j Jan. Feb. Mar. Apr. May June July 

1960 

0 

• 

• 

• 

-

-

-

-

-

I I 

Aug. Sept. Oct. Nov. Dec. 

FIGURE 168.1.-Air and subsurface temperatures and hydrograph of water-table fluctuations at the temperature-measurement site 

in McKnownville, N.Y. 
D206 GROUND WATER 

temperature and thus have a period of 1 day. Because 

of their short period, their effect can be detected only 

1 to 2 feet below land surface. The next longest waves 

are those generated by the passage of frontal weather 

systems. The period of these waves is variable, 

ranging from a few days to a week or two. Their effect 

on the temperature of the soil is detectable to depths 

of a few feet. The longest waves are those generated 

by seasonal changes in air temperature and thus have 

a period of 1 year. Depending on geologic and hydrologic conditions, these waves penetrate to depths of as 

much as 60 feet. 

The fluctuations of subsurface temperature in 

response to frontal weather systems and seasonal 

changes in air temperature are readily apparent at 

depths of 1.5 and 3.0 feet below land surface (fig. 168.1). 

During the passage of frontal weather systems, the 

daily average air temperature over a period of several 

days may change as much as 30°F. The irregular, 

short-period fluctuations of soil temperature, which at a 

depth of 1.5 feet range from about 2°F or 3°F to as 

much as 10°F, show the fluctuations caused by these 

changes in air temperature. The fluctuations of soil 

temperature at a depth of 3.0 feet in response to frontal 

weather systems is much less than at the shallower 

depth. 

As may be seen from its consistent position about 

midway between the average maximum and average 

minimum air temperature for each month, the soil 

ten1perature at a depth of 1.5 feet closely approximates 

the annual average air temperature throughout the 

year. In 1960, the average air temperature was 

48.6 °F and the average temperature at a depth of 1.5 

feet was 48°F. From April to early September, when 

the flow of heat is downward from the land surface, 

the temperature at 1.5 feet generally was a degree or 

two above the ten1perature at 3.0 feet. During the fall, 

when the average air temperature declined rapidly, 

the temperature at a depth of 1.5 feet dropped progressively lower than the temperature at 3.0 feet. 

The divergence was greatest in December when the 

temperature at 1.5 feet averaged about 8 degrees 

lower than that at 3.0 feet. The difference remained 

relatively constant until the spring thaw at the end of 

March and then was completely eliminated within a 

few days. The average ten1perature at 3.0 feet was 

52°F, or 4 degrees higher than the average ten1perature 

at 1.5 feet and about the same as the average temperature of the ground water (see table). 

The ground-water temperature at three levels within 

the saturated zone is shown in figure 168.1. In 1960 

the tmnperature at the uppermost level, 6.4 feet below 

land surface, fluctuated through a range of J6.3°F, 

whereas that at the lowest level, 17.7 feet below land 

surface, fluetuated only 3.6°F. The average groundwater temperature at all 3 levels was about 51.4 °F, 

or 2.8 °F above the annual average air temperature (see 

table). The graph of maximum and minimum temperatures in figure 168.2 suggests that there would be 

w 

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0 Air temperature \ J 

~ Subsurface temperature \/ 

I 

TEMPERATURE, IN DEGREES FAHRENHEIT 

FIGURE 168.2.-Maximum and minimum air and subsurface 

temperatures in 1960. Air temperatures are monthly average 

minimum temperatures in December 1959 and monthly 

average maximum temperatures in July 1960. 

no appreciable seasonal fluctuation below a depth of 

about 23 feet. This depth closely coincides with the 

base of the surficial sand, which the available data 

indicate is at a depth of about 20 to 21 feet. The 

relative lack of ground-water circulation in the silt and 

clay underlying the sand doubtless affects the depth of 

penetration of detectable seasonal temperature fluctuations in this area. 

The temperature of recharge reaching the zone of 

saturation had only a small effect on the ground-water 

temperature. The temperature at 6.4 feet declined 

about 1.5 °F in February 1960 in response to recharge 

with cold water during a brief thaw (fig. 168.1). The 

cooling effect at the water table, which at the time was 

about 2 feet aboYe the thermometer, doubtless was 

much greater. 
HEATH D207 

0 

2 

4 IJ.J 

(.) 

c( 

LL. 

0:: 

::::> 

en 

0 

z 

c( 8 ..J 

!: 

0 

..J 10 IJ.J 

(]) 54 5.2 50 4~ . . . 48 5.0 5JI- "s IJ.J 

IJ.J 12 LL. s ~ 

:i 

Ia.. \ IJ.J ~ 0 

52 5.3 5_2 ~50 49.5 50 

·~· . 

20 

July Aug. Sept. Oct. Nov. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 

1959 1960 

FIGURE 168.3.-lsotherms of subsurface temperatures, in degrees Fahrenheit. (Interval) 5°F. 

The differences in the temperature gradient of soil 

between the depths of 1.5 and 3.0 feet in summer and 

winter is one of the most striking features of the graphs 

shown in figure 168.1. The downward gradient during 

the spring and summer was only about one-eighth the 

upward gradient during the fall and winter. However, 

the temperature gradient of water in the zone of saturation, as shown by the temperatures at depths of 6.4, 

11.1, and 17.7 feet, was not significantly different in 

summer and winter. The explanation for the steeper 

thermal gradient across the zone of aeration during 

the fall and winter is not readily apparent. It suggests 

either a marked decrease in thermal diffusivity or the 

disturbing influence of septic-tank discharge. 

Figure 168.3 shows the differences in temperature 

with respect to time of year and depth. The diffusivity can be computed from the relationship of the 

lag in time of either the maximum or the minimum 

temperature with depth (Singer and Brown, 1956, p. 

747). Sloping straight lines representing the lag in 

temperature with depth are shown in the figure. Note 

that the slopes of the lines through the maxin1um 

isotherms and the slope of the line through the minimum 

isotherms in the zone of saturation (from 5 to 20 feet) 

are virtually the same. The diffusivity as determined 

from the maximum isotherms in the fall of 1960 is 0.007 

cm2 per second. The slope of the line through the 

minimum isotherms in the zone of aeration is difficult 

to determine, but the line drawn in figure 168.3 seems 

to fit the data fairly well. The diffusivity based on this 

line is 0.005 cm2 per second. 

Because of the higher moisture content of the soil 

during the winter, as indicated by the intermittent 

rises in the water table starting in late October 1959 

(fig. 168.1), and the presence of ice in the soil to a 

depth of 2 to 3 feet, the diffusivity during the winter 

should be substantially higher than during the summer. 

Therefore, the diffusivity of 0.005 cm2 per second computed for the zone of aeration during the winter 

probably is considerably less than the actual value. 

Although this anomaly cannot be definitely explained, 

it probably reflects the influence of septic-tank discharge. As noted above, a septic tank is located about 

32 feet from the temperature-measurement site. However, the position of the septic-tank drain field with 

respect to the site is not known. Even if the position 

of the drain field were known, it would be difficult if not 

impossible to determine the effect of stratification of the 

soil zone on the movement of the septic-tank effluent. 

If the septic-tank effluent does affect the temperatures 

in the zone of aeration, the anomalous changes in 

gradient might be explained by assuming that the 

effluent acts as a weak heat source in the spring and 

summer and as a strong heat source in the fall and 

winter. 
D208 GROUND WATER. 

The writer wishes to acknowledge the assistance of 

Charles O'Donnell, U.S. Geological ~urvey, in the 

computation of diffusivities. 

REFERENCES 

Collins, W. D., 1925, Temperature of water available for industrial use in the United States: U.S. Geol. Survey WaterSupply Paper 520, p. 97-104. 

Pluhowski, E. J., and Kantrowitz, I. H., 1963, Influence of landsurface conditions on ground-water temperatures in southwestern Suffolk County, Long Island, New York: Art. 51 in 

U.S. Geol. Survey Prof. Paper 475-B, p. B186-Bl88. 

Singer, I. A., and Brown, R. M., 1956, The annual variation of 

sub-soil temperatures about a 600-foot circle: Am. Geophys. 

Union Trans., v. 37, no. 6, p. 743-748. 
Article 169 

HYDROGEOLOGY OF THE SANTIAGO AREA, CHILE 

By WILLIAM W. DOYEL, ROBERT J. DINGMAN, and OCTAVIO CASTILLO U./ 

Washington, D.C., Lawrence, Kans., and Santiago, Chile 

Work done in cooperation with the Instituto de Investigaci6nes Geol6gicas de Chile 

under the auspices of the Agency for International Development, U.S. Department of State 

Abstract.-Wells tapping unconsolidated valley fill in the 

Vaile Central supply a large part of the water needs of Santiago. 

The east side of the valley is underlain by unconfined deposits 

that yield hard water whose mineral content increases westward 

in the direction of ground-water flow. Flowing wells on the 

west side of the valley tap a confined aquifer that yields bicarbonate water of lower mineral content and hardness. 

. The Santiago area is a part of the Cuenca de Santiago 

(Santiago basin), the northernmost portion of the great 

Valle Central (Central Valley) of Chile. The Valle 

Central lies between the snow-capped Cordillera de los 

Andes and the lower Cordillera de la Costa (Coastal 

Range) and extends from the Cuesta de Chacabuco 

southward to Puerto Montt (fig. 169.1). The many 

streams that discharge into the Valle Central from the 

Cordillera de los Andes are used extensively for irrigation and, in the Santiago area, for a part of the water 

supply of the city. Santiago, with a population of 

2,093,000 in 1961, uses approximately 8.0 cubic meters 

per second of water, 40 percent (3.2 m3/sec) of which is 

ground water. Approximately one-fourth of the ground 

water is obtained from a system of collection galleries 

in the Vitacura area (fig. 169.2); the remainder is 

obtained from 339 privately and publicly owned wells 

that range in depth from 12.6 to 236 m (Castillo and 

others 1963). The ground water is used for public 

water supply (74 percent), industry (23 percent), and 

irrigation (3 percent). 

The Valle Central is the topographic expression of a 

great north-trending graben that separates the Cordillera de los Andes from the geologically older Cordillera 

de la Costa (W. D. Carter, written communication, 

1 Geologist, Instituto de Investigaciones Geologicas de Chile. 

1962). Although the geologic age of ash-flow deposits 

in similar structural valleys in northern Chile indicates 

that downwarping in those valleys occurred in the early 

or middle Tertiary (Dingman, 1963), the major downward movement in the Valle Central probably occurred 

near the end of the Tertiary. The total thickness of 

unconsolidated sediments in the Cuenca de Santiago is 

not known because the few wells that completely penetrate the fill are located near rock outcrops. As the 

bedrock was subjected to erosion and tectonism after 

formation of the graben, its surface is characterized by 

high relief; Cerro Santa Lucia and Cerro Renca are the 

t.ops of. bedrock hills whose lower slopes have been buried 

beneath valley fill. A gravity survey made by Edgar 

Kausel (written communication, 1960) showed the maximum depth to bedrock to be between 300 and 500 m, 

but until proved by test drilling these depths must be 

considered only approximate. In 1962, the first .of a 

series of deep wells was being drilled in Santiago to explore for deeper aquifers and to determine the thickness 

of the fill. 

The surficial deposits in the basin are colluvial, 

fluvial, and f:luvioglacial materials of Quaternary 

age. Some unconsolidated deposits in the vicinity of 

Santiago, which were described as glacial moraines by 

Bruggen (1950), Karzulovic (1958), and others, have 

since been examined by R. F. Flint, R. W. Lemke, 

Ernest Dobrovolny, Kenneth Segerstrom (Art. 152), 

and the authors, all of whom agree that the deposits 

were laid down by mudflows as a relatively thin slurry. 

At present, ground-water supplies are obtained from 

fluvial material8, possibly valley-train deposits, consisting of interconnected lenses of highly permeable 

sand and gravel interbedded with thick layers of clayrich mudflows of low permeability. Most of the drilled 

ART. 169 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D209-D212. 1964. 

D209 
D210 GROUND WATER 

10 20 KILOMETERS 

FIGURE 169.1-Map of the Santiago area, Chile. 

wells in the Santiago area produce ground water from 

depths of 50 to 100m. 

The character of the deeper unconsolidated sediments in the valley is not known; trrey probably are 

of continental origin and consist of detrital material 

derived chiefly from erosion of the Cordillera de los 

Andes and, to a lesser exte~ t, from erosion of the 

Cordillera de la Costa. The deeper deposits may 

be largely of lacustrine origin. Approximately 50 

kilometers north of Santiago, the Valle Central is 

terminated by bedrock hills that rise 200 m or more 

above the present valley floor. About 50 km south of 

Santiago is a bedrock ·hill that does not completely 

close the present valley but marks the southern end 

of Cuenca de Santiago and may have formed a barrier 

behind which a lake may have formed during Pleistocene time. 

Flowing wells with yields of up to 200 liters per 

second have been obtained from deltaic sediments 

that were deposited in a large glacial lake formed by 

glacial damming in the San Carlos area of the Vaile 

Central, 300 km south of Santiago. It is conceivable 

that, during one of the Pleistocene glacial stages, similar 

ice tongues may have extended into the Cuenca de 

Santiago, blocking the drainage and forming a glacial 

lake. Sediments dep.osited in such a lake may have 

formed an areally extensive aquifer, which would be 

in contrast to the lenticular, fluvial deposits which 

now are the source of ground water for- Santiago. 

At present almost all the sediments being deposited 

in the Valle Central are derived from the Cordillera 

de los Andes, where heavy precipitation and steep 

gradients combine to produce rapid erosion. The 

Cordillera de la Costa has a much slower rate of 

erosion because the rainfall is less and the gradients 

are gentler. Colluvium and some alluvial sediments 

derived from the Cordillera de la Costa are present, 

however, along the western side of the valley. 

Ground water presently used in and near Santiago 

is obtained from an unconfined aquifer in which the 

water table slopes generally southwestward. The 

average hydraulic gradient is about 10 mfkm in the· 

eastern part of Santiago but decreases to about 3 m/km 

in the southwestern part of the city. Although 

infiltrating rainfall and irrigation water are sources 

of some recharge in the central part of the basin, the 

principal source of recharge is runoff from the west 

slope of the Cordillera de los Andes. The Rio Colina 

and Rio Lampa in the northern part of the basin, the 

Rio Mapocho, which flows through Santiago, and the 

Rio Maipo, approximately 25 km south of Santiago, 

contribute a large percentage of the recharge along the 

eastern side, as shown by the slope of the water table 

away from those rivers (Castillo and others, 1963). 

The remainder of the recharge infiltrates through the 

alluvial and colluvial sediments that lap up onto the 

flanks of the Andean foothills. 

Because the more permeable water-bearing materials 

are lenticular or narrowly enlongate, nearby wells 

may penetrate different bodies of water-bearing material; however, comparable water levels and similar 

responses to ground-water withdrawals demonstrate 

that the principal aquifer is hydraulically continuous 

throughout the central and eastern parts of the area. 

Perched bodies of ground water are found near the 

Rio Mapocho as a result of the lenticularity of the 

sediments and the relative impermeability of the underlying beds. 

Available information is insufficient to determine the 

area or areas of ground-water discharge. The relation of the streams in the central part of the Santiago 
DOYEL, DINGMAN, AND CASTILLO U. D211 

EXPLANATION 

~ 500-700 900-1100 Edge 

-

of valley 0 10 KILOMETERS 

fill 

700-900 >1100 

0 04-8 

Well 

FIGURE 169.2.-Map showing dissolved-solids content in ground water of the Santiago area, Chile. Analyses made in the laboratory of the Instituto de Investigaciones Geol6gicas de Chile in 1960-61. 

area to the water table has not been studied, nor are 

data available regarding the movement of ground 

water south of the report area. The Rio Mapocho, 

however, probably serves as a ground-water drain in 

the western part of the basin. 

The relatively few wells drilled along the western 

side of the Cuenca de Santiago are flowing artesian 

wells. Although evidence of a geological separation, 

such as might result from faulting, is lacking, the difference in the chemical quality and temperature 

between the water from the flowing wells in the western 

part and from the water-table wells in the central and 

eastern part of the area indicates the existence of 

some sort of barrier, either geologic or hydraulic, the 

nature of which is not yet understood. 

Figure 169.2 shows the distribution of dissolved 

solids in the Santiago area, based on analyses reported by Castillo and others (1963). The ground 

water has a low dissolved-solids content, 200-300 

milligram$ per liter, near the Rio Mapocho in the eastern part of the area. The dissolved-solids content 

increases in the direction of ground-water movement 

to as much as 700 mg/l in the central part of the area 

and to more than 1,000 mg/1 to the southwest. The 

dissolved-solids content of water from flowing wells 

along the western side of the basin, however, is less 

than 300 mg/l. As shown in figures 169.2 and 169.3, 

the change is rather abrupt from the more highly 

mineralized water yielded by wells tapping the unconfined aquifer to the east. 

The hardness of the water presents the same general 

picture as the dissolved-solids content. Close to the 

Rio Mapocho in the eastern section of Santiago the 

hardness is relatively low, less than 400 mg/l (computed 

as CaC03), but it increases to nearly 800 mg/l southwestward. However, the water from flowing wells on 

the western side of the basin has a hardness of less than 

200 mg/l. Moreover, the water from flowing wells on 

the west side of the basin is characterized by a higher 

proportion of sodium and a lower proportion of sulfate 
D212 

1200 

1000 

0:: 

LLI 800 

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a_ 

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~ 

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= 400 ~ 

200 

A 

...... 

I 

LO 

II) 

Temperature 

Dissolved 

L solids 

N 

I 

LO 

(.) 

--·· ···--Hardness 

3 CIO I I 

LO 'o:t 

Cl Cl 

----

GROUND WATER 

0 

N 3 N I I I ('I') ('I') ('I') 

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LLI 

0:: 

(.!) 

LI.J 

10 Cl 

5 

0 0 

FIGURE 169.3.-Changes in dissolved-solids content, hardness, and temperature of ground water along line A-A' (fig. 169.2). 

and chloride as compared to the water from wells east 

of the Ri6 Mapocho. The low proportion of sulfate 

and chloride is reflected in the noncarbonate hardness, 

which commonly is very low in the well water of the 

west side of the basin. These differences in chemical 

quality suggest that there is little or no interconnection 

between the unconfined aquifers of the east and central 

parts of the area and the confined aquifers tapped in 

the western part. 

The problem of the marked differences in water 

quality cannot be resolved on the basis of geologic 

information now available. The differences may be 

due to geologic barriers such as faults or facies changes. 

On the other hand, the artesian water of the west side 

may be characteristic of a confined aquifer that passes 

beneath the unconfined aquifers to the east. Should 

such a deeper aquifer be present it would be of considerable economic importance to the area. 

Additional geological and hydrological data are 

necessary to define the control mechanism of the groundwater system in the Cuenca de Santiago, particularly 

the separation between the artesian and nonartesian 

waters. The test-drilling program now in progress 

(1963), as 'well as the continuing investigations by the 

Instituto de Investigaciones Geol6gicas de Chile, should 

provide sufficient information for a better understanding 

of ground-water conditions and for a better utilization 

of ground-water resources. 

REFERENCES 

Briiggen, Juan, 1950, Fundamentos de la geologia de Chile: 

Instituto Geogra;fico Militar, Santiago, 374 p. 

Castillo, Octavio, Falc6n, Eduardo, Doyel, W. W., and Valenzuela, Manuel, 1963, · El agua subterranea de Santiago, 

segundo informe 1958-1962: Instituto de Investigaci6nes 

Geol6gicas de Chile. [In press] 

Dingman, R. J., 1963, Geologyofthe Tulor quadrangle: Instituto 

de Investigaci6nes Geol6gicas de Chile. [In press] 

Karzulovic, Juan, 1958, Sediments cuaternarios de aguas subterraneas en la Cuenca de Santiago: Universidad de Chile, 

Instituto de Geologia, Pub. 10, 120 p. 
Article 170 

GROUND WATER IN THE ARICA AREA, CHILE 

By WILLIAM W. DOYEL, Washington, D.C. 

Work done in cooperation with the Instituto de Investigaciones Geol6gicas 

de Chile and the Corporacion de F omento de la Produccion under the auspices 

of the Agency for International Development, U.S. Department of State 

Abstract.-The water supply for the city of Arica presently 

is obtained from a water-table aquifer in the lower Valle de 

Azapa. Water levels are declining owing to overdevelopment; 

an additional supply is needed to meet present demands. An 

artesian aquifer underlying the Pleistocene coastal terrace north 

of Arica apparently is the only other source of large supplies of 

usable water in the area. 

The present (1962) water supply for Arica~ the northernmost coastal city in Chile, is obtained from wells 

tapping a water-table aquifer in the lower Valle de 

Azapa 1 (fig. 170.1). In 1960 an estimated 400 liters 

per second was being withdrawn for the' public supply 

and for irrigation in the part of the valley extending 40 

kilometers inland from Arica (Kleim.an and Torres, 

1960). Water use both for the city· and for irrigation 

has increased, and withdrawals have exceeded the 

capacity of the aquifer to yield water. The resulting 

rapid decline of the water table is forcing the city to 

search elsewhere for additional water supplies. 

Rainfall west of the foothills (Pre-Cordillera) of the 

Cordillera de los Andes is negligible; only traces of 

rainfall have been recorded in Arica at intervals of 

several years. One perennial stream, the Rio Lluta, 

flows through the area, but the water is too highly 

mineralized for other than limited agricultural or 

industrial use. The Rio San Jose, which flows through 

the Valle de Azapa, is perennial in its upper reaches 

and intermittent in the lower part of the valley. The 

river discharges into the ocean only every 4 or 5 years 

when it is in flood stage, which may last a few days or 

a few weeks. A small amount of the floodwater is 

used for irrigation, but most of it is lost into the Pacific 

Ocean. 

t Spanish terminology is used for geographic names; for example, Valle for valley, 

and Quebrada for valley containing dry or intermittent stream. 

Water from the Rio Lauca, on the Altiplano approximately 100 km east of Arica, has been diverted by 

means of canals and a tunnel into the Valle de Azapa 

and will help alleviate the water shortage in the area. 

Arica lies at the northern end of the Cordillera de la 

Costa (Coast Range), at the mouth of the Rio San 

Jose. Extending northward from Arica into Peru is 

La Concordia, a plain bounded on its eastern side by a 

north-south scarp and on its western side by the 

Pacific Ocean. The plain, which slopes gently westward to the ocean, widens northward and is approximately 8 km wide at the Peruvian border. 

The scarp marks the westernmost extent of a thick 

section of conglomerate, sand, and pyroclastic deposits 

of late Tertiary and early Pleistocene age, the upper 

surface of which forml3 a westward-sloping plain extending seaward from the Pre-Cordillera. The Rios 

San Jose and Lluta, which issue onto La Concordia 

from steep-walled valleys, as well as the stream that 

formed the Quebrada Gallinazos and now is intermittent and flows only at widely spaced intervals, have 

dissected the highland in the Chilean territory. 

La Concordia was formed as a depositional terrace 

during the Pleistocene and is underlain by interbedded 

marine and continental sediments with a thickness of 

at least 200 meters. The surface is composed of at 

least three erosional terraces, each marking a stage in 

the recession of the sea. The Rios Gallinazos (Quebrada Gallinazos) and San Jose have incised steepwalled channels into the surface of the plain, and the 

Rio Lluta has cut a valley containing a series of terraces 

that can be correlated with successive stages in the 

lowering of the base level of the river. The Rios 

Lluta and Gallinazos have built alluvial fans onto the 

most recent erosional terrace along the present shoreline, and the Rio San Jose is building a delta. 

ART. 170 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D213-D215. 1964. 

D213 
D214 GROUND WATER 

70° 15' 70°00' 69°45' 18°00' 

/ / 

( 

/ 

5 0 20 KILOMETERS 

L----L----~--~-----L--~ _/ 

FIGURE 170.1.-Map of the Arica area, Chile. 

Recent sediments are present in the form of colluvium, as alluvial deposits of the rivers, and as windblown sand covering much of the area. The face of 

the scarp that forms the eastern border of La Concordia 

and the surface of the high plain are covered in the 

Arica area with a concretelike layer of salt-cen1ented 

sandy or tuffaceous n1aterial. 

The only possibilities for developing substantial 

additional ground-water supplies in the Arica area are 

in the Valle de Azapa, which is presently overdeveloped, 

the Valle Lluta, and on La Concordia; that is, fron1 the 

Pleistocene and Recent sediments. S01ne of the older 

sediments probably contain and could transn1it water, 

but lack of recharge and the effects of diastrophism 

preclude the possibility of developing substantial water 

supplies fron1 the pre-Pleistocene sediments. 

Ground water in the Vaile de Azapa occurs in an 

unconfined aquifer in the alluvial deposits, which are 

less than 100 m thick. The aquifer has been exploited 

for several centuries, at least as far back as Inca times, 

but since the advent of drilled wells and large-capacity 

purnps it has been overdeveloped. As predicted by 

Taylor (1949), overdevelopment has resulted in a declining water table, which, in turn, has led to the 

abandonment of many hand-dug wells in the Arica 

area. In addition, all the springs have ceased to flow. 

Recharge to the aquifer con1es from seepage and underflow fr01n the upstream portion of the Rio San Jose 

and also from floods and irrigation water. The water 

table slopes toward the Pacific Ocean, and fresh 

ground water probably is being discharged by evaporation and as seeps along the present shoreline near 
DOYEL D215 

Arica. Salt-water intrusion may be taking place but 

definitive data are not available. 

Test wells drilled in the Valle Lluta have shown that 

the valley fill will yield little ground water. 

About 10 years ago several successful water wells 

were drilled on La Concordia Peruana (the part of La 

Concordia in Peru), 7 km north of the Chile-Peru 

border. La Concordia Chilena (the part of La Concordia in Chile) is geographically and geologically 

similar to La Concordia Peruana, and 4 exploratory 

wells were drilled on it between the Quebrada Escritos 

and the border to deterrnine whether the productive 

aquifer extended into Chile. All4 wells struck artesian 

water that rose to within 15 m of the surface. The 

water occurs in sand and gravel strata between 75 and 

130 m below the surface. Well 2 (fig. 170.1) was 

pumped at 150 liters per second (approximately 2,400 

gallons/minute) for 120 hours, and as the maximum 

drawdown was 8.5 m, the specific capacity of the well 

was 17.6 liters per second per rneter of drawdown. At 

the end of the test the water contained 835 milligrams 

per liter of total dissolved solids, 247 mg/l of chloride, 

172 mg/1 of sulfate, and 368 rng/1 of total hardness. 

The artesian head, the slope of the piezometric 

surface, and the water quality indicate that there is 

recharge to the artesian aquifer, although they give no 

information regarding the quantity. Test drilling has 

shown that there is no recharge reaching the aquifer 

from either the Valle Lluta or Valle de Azapa, and that 

recharge is probably coming from the northeast, from 

Peru. Ground water on La Concordia should not be 

developed without consideration of the possibility of 

intrusion of sea water, or possibly of inflow of salty 

marine connate water from unflushed parts of the 

aquifer as the artesian pressure declines. 

A shallow water-table aquifer, penetrated in wells 1, 

2, and 3, about 18 km north-northwest of Arica (fig. 

170.1), probably is recharged from the infrequent rains 

in the area and could not support large-scale sustained 

withdrawals. 

The artesian aquifer underlying La Concordia 

presents the best possibility for developing large additional water supplies in the Arica area. The diversion 

of water from the Rio Lauca is increasing the ground 

water available in the Valle de Azapa, both by furnishing additional recharge and by replacing water 

supplies formerly withdrawn from the water-table 

aquifer. Artificial recharge by means of check dams 

and off-strean1 ponds also would increase the amount of 

recharge during periods of flood flow in the valley. 

Improvements in methods of irrigation could reduce the 

amount of water required per hectare, which would 

make additional water available in the Arica area. 

However, if the Arica area continues to develop, the 

Valle de Azapa, even with the Rio Lauca diversions, cannot furnish sufficient water for irrigation, public supply, 

and industrial use. 

The artesian aquifer beneath La Concordia has been 

supplying water for irrigation on La Concordia Peruana 

for 10 years without any significant lowering of water 

levels. This fact, together with the information now 

available (1962) as a result of the test-drilling program, 

indicates that the artesian aquifer beneath La Concordia Chilena could be exploited to supply additional 

water to the Arica area. Even if the water could not 

be used for irrigation on La Concordia, owing to the 

salinity of the soil, it could be used for public and 

industrial supplies, thus releasing ground water in the 

Valle de Azapa for irrigation. 

Additional investigations, including drilling of test 

wells spaced throughout La Concordia Chilena, are 

being carried out by the Instituto de Investigaciones 

Geol6gicas de Chile and the Corporaci6n de Fornento de 

la Producci6n de Chile to determine the ground-water 

potential of the artesian aquifer beneath La Concordia, 

as well as the maximum amount of water that can be 

withdrawn from the water-table aquifer in the Valle de 

Azapa without causing progressive water-level declines. 

REFERENCES 

Kleiman, Pablo, and Torres, Juan, 1960, El agua subterranea en 

el Valle de Azapa: Ministerio de Obras Publicas, Direcci6n 

de Riego, mimeo. rept., 47 p. 

Taylor, G. C., Jr., 1949, Geology and ground water of the Azapa 

Valley, Province of Tarapaca, Chile: Econ. Geology, v. 44, 

no. 1, p. 4D-62. 
Article 171 

"LAZY" THERMOMETERS AND THEIR USE IN MEASURING GROUND-WATER 

TEMPERATURES 

By RALPH C. HEATH, Albany, N.Y. 

Work done in cooperation with the New York Water Resources Commission 

Abstract.-The temperature of ground water at selected depths 

in unpumped, nonfiowing wells can be measured in place with 

high-lag "lazy" thermometers. These thermometers are constructed by enclosing the bulb of liquid-in-glass thermometers 

with material of high specific heat, a layer of insulation, and a 

protective case. 

Data on ground-water temperatures have been applied successfully in recent years to a variety of pro blems, and such data promise to become one of the 

most useful tools in ground-water hydrology. In most 

ground-water investigations, temperature measurements are obtained only for water being discharged 

from flowing or pumped wells. Such measurements 

are of limited usefulness because they represent a 

weighted average of the temperature of the producing 

zone open to the well, which in some places may be 

more than 100 feet thick. 

Measurements of water temperature in wells have 

been made with thermometers inserted in bottles and 

lowered down the wells. There are drawbacks to this 

method and, unless special precautions are taken, the 

measurements may be in error by several degrees. 

The most precise way to measure the temperature of 

water in place in wells is with an electrical thermometer. Such thermometers, accurate to 0.1 °F, are available from several manufacturers. However, because 

electrical thermometers are fairly expensive, and somewhat delicate, they are not practical for many field 

investigations. 

Where it is desirable to measure the temperature at 

the same aepth in the same well periodically, satistory data can be obtained with so-called "lazy" thermometers. These thermometers are made by enclosing 

the bulb of an ordinary liquid-in-glass thernwmeter in 

such a manner that its response to change in temperature is delayed. Figure 171.1 shows the features of 

a lazy thermometer recently built by the author. It 

consists of four parts: 

1. Standard liquid-in-glass thermometer in a metal 

case 

2. Layer of material of high specific heat 

3. Layer of insulation 

4. Outer protective metal case. 

Standard field 

__.---thermometer in 

metal case 

Thermometer in 

metal case 

11/4-inch-diameter 

aluminum tubing 

Figure 171. 1-Detail of a "lazy" thermometer. 

ART. 171 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D216-D218. 1964. 

D216 
HEATH D217 

Many materials are probably suitable for use in constructing lazy thermometers. The author uses aluminum tubing for the outer case. A layer of cork about 

0.15 inch thick is used for insulation, and a layer of 

brass "B-B" shot is inserted between the thermometer 

case and the insulation. The top and bottom are sealed 

with plastic aluminum. However, because the annular 

space between the thermometer and its metal case is 

difficult to seal at the top, water displaces the air in 

the pores between the brass shot when the thermometer is submerged. This is, in fact, desirable because of 

the high specific heat of water. 

In order to determine whether a lazy thermometer 

is suitable for the use intended, its inertial characteristics must be determined. This is done by immersing 

the thermometer in water of a constant temperature, 

either above or below the air ten1perature. After the 

thermometer reaches the same temperature as the 

water, the thermometer is removed and a record is 

made of the change in temperature with time as the 

thermometer approaches the air temperature. The 

time is recorded to the nearest second and the temperature estimated to the nearest 0.1 degree. A graph is 

plotted of log of the time, in seconds, versus log of the 

change in temperature, in degrees Fahrenheit, divided 

by the difference between water and air temperatures. 

The time, in seconds, during which different percentage 

changes of temperature occur may be determined directly from the graph. 

The next step depends on the accuracy desired in the 

temperature measurements for which the lazy thermometers are to be used. Many field investigators 

read thermometers only to the nearest degree or nearest 

half degree. With care, however, the thermometer in 

common field use in the Water Resources Division of 

the U.S. Geological Survey can be read to 0.1 degree 

with an error of ±0.1 degree. (It is recognized, of 

course, that many field thermometers are not accurate 

to 0.1 degree. A part of this difficulty can be resolved 

by calibrating the field thermometer to a laboratorytested master). Therefore, if it is desired to read the 

lazy thermometer to the nearest 0.1 degree, the problmn 

is to determine the length of time required for a change 

of 0.1 degree at the maximum expecte9- difference between water and air temperature at the locality in 

which the thermometer is to be used. Figure 171.2 

shows the time required for a change of 0.1 °F in one 

of several lazy thermometers built by the author. 

For comparison, the inset in the upper right-hand 

corner of figure 171.2 shows the time required for the 

standard field thermometer in its metal case to change 

1.0°F. It may be seen that its lag is one-fortieth that 

of the lazy thermometer. 

ci 

UJ 

fIJ.J 

:2 

0 

:2 

0::: 

IJ.J 

I 

f-

>-

~ ~ : z 

~ 8 

IJ.J IJ.J (f) 

~ 

z z 

<( -

I 

(.) 

!;'-

...... 

0 

0::: 

0 

u.. 

IJ.J 

:2 

f= 

1QQ.---------,---r------.---.---, 

10 20 30 40 

DIFFERENCE IN TEMPERATURE BETWEEN AIR 

AND WATER, IN DEGREES F 

50 0::: 

IJ.J 

fIJ.J 

:2 

0 (f) 

40 :2 0 0::: z IJ.J 0 I(.) 

f- IJ.J 

(/) 

z 30 - z 

IJ.J 

~ w z (f) 

<( <( 

20 I (.) 

(.) ....1 

u.. <( 0 f- 0 IJ.J 

...; :2 

10 0::: z 0-

u.. 

IJ.J 

0 :2 

20 f= 

70 

FIGURE 171.2.-Inertial characteristics of a "lazy" thermometer. 

Whether a specific lazy thermometer can be used in a 

given well depends on (1) the inertial characteristics of 

the thermometer, (2) the depth at which temperatures 

are to be measured, and (3) the ~aximum expected difference in temperature between the water and the air. 

In normal practice the thermometer is left subD?-erged 

at the desired depth between readings. (Parachute 

cord has been found to be highly satisfactory for holding 

the thermometers). Therefore, the time required to 

withdraw the thermometer from the well and read the 

temperature is the limiting factor in precision. 

Thermometers can be withdrawn from wells at a rate 

of about 3 feet per second and can be read in 5 to 10 

seconds, depending on the skill of the observer. To 

determine the maximum depth at which a particular 

lazy thermometer can be used, it is necessary to determine the lag, in seconds, at the expected maximum 

difference between water and air temperature, subtract 

10 seconds, and multiply the remainder by 3. For 

example, the expected maximum difference between 

water and air temperature at Albany, N.Y., is about 

60 °. The "lazy" thermometer for which data are 

plotted in figure 171.2 has a lag of 31 seconds at this 

difference. Therefore, by subtracting 10 seconds and 

multiplying by 3, it is found that this thermometer 

can be used at any depth down to about 60 feet. If 

measurements accurate to 0.2 degree were acceptable 

or if the expected maximum difference between water 

and air temperature was only 30°, the thermometer 

could be used to a depth of about 90 feet. As seasonal 

fluctuations of ground-water temperature, regardless 
D218 HYDROLOGIC INSTRUMENTAT'ION 

of whether they are caused by stream infiltration or 

changes in air temperature, occur at depths greater 

than about 60 feet only under unusual conditions, it 

is obvious that lazy thermometers are an economical 

and practical tool for monitoring fluctuations in groundwater temperatures. 
Article 172 

TELEVISION APPARATUS FOR BOREHOLE EXPLORATION 

By j. E. EDDY, Washington, D.C. 

Abstract.-A closed-circuit television system has been developed which operates in 8-inch-diameter and larger holes to 

depths of approximately 1,000 feet in either dry or water-filled 

holes. 

A closed-circuit television system for use in water 

wells has been developed that can be operated in boreholes 8 inches in diameter and larger. The equipment 

is well adapted for locating and examining fractures 

and solution openings, and for identifying changes in 

lithology in uncased holes drilled in consolidated rock. 

It is useful also for examining the position and condition of screens, casing, and obstructions in cased holes. 

The equipment was designed to be as simple as possible 

and to operate at a maximum hydrostatic pressure 

of 1,000 feet of water. 

The system uses a high-resolution Kin Tel camera 

and monitor modified for use in boreholes. The 

monitor and camera provide a full 500-line resolution 

which is about twice that of home television receivers: 

A 14-inch aluminized picture tube with a Polaroid filter 

mounted in front provides a bright clear picture even 

in high ambient light. 

The control unit was designed to provide a high 

degree of flexibility for both camera and monitor. The 

unit includes a video amplifier of 8-megacycle bandwidth to furnish the 500-line resolution. Remote 

camera controls including horizontal and vertical centering controls may be used to shift the field of vision 

electronically. Fully automatic electronic target control provides self adjustment of the image intensity 

over a range of 4,000 to 1. Service and operation 

of the unit have been simplified by placing all the 

control adjustments on the front panel and building 

the chassis so that it may be removed readily from the 

front of the mount. 

Two cameras were used in the development of the 

present equipment. The first was a Kin Tel model 

1990 enclosed in a metal tube 17% inches long by 6 inches 

in diameter. This camera was fitted with a lens with 

motor-driven focus and iris adjustments, and a mirror 

attached to the front of the case for viewing the side 

of the borehole. Several combinations of lenses and 

closeup attachments were used, but the results were 

generally unsatisfactory. 

The second camera was built from a Kin Tel model 

1986-C studio camera, modified to fit into an aluminum 

tube 36 inches long with a 4Yz-inch outside and a 3Yz-inch 

inside diameter. The lower end is fitted with a quartzglass plate a quarter of an inch thick, specially cut from 

glass having a tensile strength of 2,000 psi. Both the 

viewing end and the upper end of the camera case are 

fitted with 0-rings and sealed with silastic rubber. A 

high-pressure coupling with neoprene sleeves joins the 

conductor cable to the camera. The camera (with 

attached cable) has been tested successfully in a pressure 

chamber to simulated depths of 950 feet of water. 

The camera assembly uses a very wide angle fixedfocus lens-a French-made Kinoptick "fish eye" lens 

with a focal length of 5.7 mm, a field of view of 117°, 

and an overall diameter of 3Yz inches. This lens has a 

depth of field of from 4 inches to infinity, thus making 

it possible to see the lighted area of the well bore very 

close to the camera and eliminating the problems involved in the motor-driven iris and focus controls. 

The camera is shown in figure 172.1. 

The most difficult problem of design has been adequate illumination in the viewed area when the camera 

is below water level in a well. Absorption and dispersion of the light in water reduce greatly both the contrast and intensity of the image received. The problem 

of lighting becomes increasingly difficult in designing 

lights for relatively small diameter holes. The most 

satisfactory lights used were 3-inch quartz iodide lamps 

rated at 600 watts each, wired in parallel. In larger 

holes, 3lamps directed ahead at a 45° angle were placed 

8 to 10 inches to the side of the camera. 

In small holes the best results were obtained with 3 

lights positioned 120° apart and mounted on the lower 

ART. 172 IN U.S. GEOL. SURVEY PROF. PAPER 475-D, PAGES D219-D220. 1964. 

71~6 o-64-15 D219 
D220 HYDROLOGIC INSTRUMENTATION 

FI~WRE 172.1.-Camera with attached lights. A reel, wound 

With 1,300 feet of 24-conductor cable, is mounted in the truck. 

end of the camera case (fig. 172.1). With the lamps in 

this position, light is directed both outward and downward on the sidewall of the hole. In an 8-inch hole the 

lighted area of view extends from approximately 4 

inches to 30 inches in front of the camera. Because 

of the heat generated, the quartz iodide lamp can be 

used for prolonged periods only when immersed in 

water. At present the lighting is only adequate; it is 

expected that future experimentation will improve this 

important part of the system. 

A municipal well at Hampstead, Md., was used for 

experimental tests of the equipment. The well, which 

is 8 inches in diameter and was drilled by the cable-tool 

method, penetrates fractured gneiss and schist of the 

Piedmont physiographic province. It is 400 feet deep 

and is cased to a depth of 60 feet. Tests were limited, 

however, to depths of about 200 feet because the reel 

assembly was not equipped with a motor. 

In the piedmont, ground water is produced largely 

from joints and fractures in the rock. Fractures, 

irregularities of the hole, changes from lighter to darker 

rock, and quartz veins were clearly distinguishable on 

the TV monitor. Figure 172.2 is a typical closeup 

photograph of the monitor showing some of the features 

observed in the uncased part of the borehole. Like 

home TV, the picture is sharper when viewed directly 

rather than from a photograph of the image. 

FIGURE 172.2.-Joints enlarged by drilling, in well at Hampstead. 

The experiments indicate the usefulness of the TV 

apparatus, particularly where ground water occurs in 

joints or solution openings. Although the present 

equipment is fully operational, additional improvements are being designed; for example, except for the 

vidicon tube, the camera circuit can be completely 

transistorized. This will make it feasible to provide a 

part of the camera power through self-contained batteries, and will reduce the number of conductors required from 24 to perhaps 12-permitting a sizable 

reduction in cable weight and cable-spool size. 

Transistorizing the camera also makes it feasible to 

reduce the diameter of the metal case containing the 

camera and accompanying circuit. It is expected that 

a modified camera assembly, without the light assembly, 

can be built with a 3Yz-inch outside diameter. Depending upon the lighting arrangement, this may make it 

possible to operate the equipment in 6-inch diameter 

holes. 

A number of lighting changes are under consideration, but most of these improvements will be based on 

experiments in boreholes. Proper lighting appears to be 

a question of correctly positioning and directing the 

lights. Commonly, if the lights are improperly positioned, a "hot spot" or intensely lighted area saturates 

the picture tube. Possibly, monochromatic light with 

a wavelength selected to coincide with the most sensitive range of the vidicon tube may reduce light dispersion and absorption. Experiments are planned to test 

the feasibility of using such a lighting system. 
SUBJECT INDEX 

[For major subject headings such as "Economic geology," "Geophysics," "Sedimentation," see under State names or refer to table of contents.] 

A 

Age determinations. See Potassium-argon, 

Radiocarbon, and Rubidiumstrontium age determinations. 

Page 

Alaska, oil shale, Brooks Range foothills ______ D131 

Andrew Formation, Mississippi, definition___ 46 

B 

Bachelor Mountain Rhyolite, Colorado, definition ___ ------------------------- 57 

Barstow Formation, California, paleontology_ 18 

Boreholes, exploration by television__________ 219 

c 

Cadmium, in the Pierre Shale________________ 73 

California, geochronology, Sonoma County___ 105 

paleontolOgy, Mojave Desert_____________ 18 

stratigraphy, Mojave Desert______________ 18 

San Joaquin Valley___________________ 14 

structural geology, northern Coast Ranges_ 7 

Canadian Shield, geochronology______________ 100 

Carboniferous. See Mississippian, Pennsylvanian. 

Cation exchange, effect on thermal behavior of 

clinoptilolite and heulandite______ 89 

Caves, :fluvial sedimentation__________________ 141 

Chile, geomorphology, Santiago______________ 144 

ground water, northern pa:rt______________ 213 

Santiago ____ -------------_____________ 209 

stratigraphy, Santiago____________________ 144 

Clay deposits, residual, thorium and uranium 

content ___ -------_________________ 128 

Clinoptilolite, effect of cation exchange on 

thermal behavior_________________ 89 

Colorado, petrology, Leadville area___________ 28 

petrology, San Juan Mountains__________ 49 

stratigraphy, San Juan Mountains_______ 54 

San Miguel County __ ---------------- 33 

structural geology, San Juan Mountains__ 123 

San Mignel County_----------------- 33 

Copper, in alluvium, geochemical prospecting_ 79,98 

Corals, Silurian and Devonian, North America_ 149 

Creede Formation, Colorado, redefinition_____ 62 

Cretaceous, California, geochronology________ 101i 

California, structural geology_____________ 7 

Great Plains, cadmium in Pierre Shale___ 73 

Massachusetts, stratigraphy______________ 118 

Mississippi, stratigraphy_________________ 43 

Crustal studies, Nevada, Las Vegas area_____ 108 

Cyanogen bands, suppression_________________ 176 

D 

Dantzler Formation, Mississippi, redefinition_ 46 

Devonian, North America, paleontology______ 149 

Diatons, California, San Joaquin Valley______ 14 

Differentiation, magmatic, in volcanic rocks__ 49 

Dilution technique, for solubility determination____________________________ 167 

Dolomite, solubility in ground water_________ 179 

E 

Eddies, as :flow indicators in rhyolite_________ 70 

Electrodes, cation-sensitive glass, for solubility 

determinations_------------------ 167 

Page 

Eocene, Mississippi, stratigraphy_____________ D43 

Estuaries, factors affecting attached organisms_____________________________ 194 

F 

Farmers Creek Rhyolite, Colorado, definition_ 58 

Fisher Quartz Latite, Colorado, redefinition__ 61 

Floods, height-frequency relations____________ 202 

Flow direction, determination in rhyolite_____ 70 

Fluoride, in ground water____________________ 189 

Franciscan rocks, California, geochronology__ 105 

California, structural geology_____________ 7 

Friction carpet, at base of thrust sheets_______ 9 

G 

Gas chromatography, effluent collector_______ 164 

Gas jet, d-e arc spectroscopy_________________ 176 

Geochemical prospecting, copper in alluvium ___________________________________ 79,98 

molybdenum in alluvium________________ 98 

sampling-error effects_____________________ 84 

time variations in mineral abundance_____ 98 

Glaucophane, in schist, isotopic age determination _________ -----------------__ 105 

Gravity studies, Nevada, Las Vegas area_____ 108 

Ground water, effect of diversion by drainage 

ditches_-------------------------- 198 

modified thermometer for temperature 

studies __ ------------------------- 216 

reaction with dolomite____________________ 179 

temperature variations __ ----------------- 204 

Gypsum Valley salt anticline, Colorado, late 

growth __ ------------------------- 33 

H 

Hawaii, geophysics, island of HawaiL _ ------- 112 

Hematite, determination of iron content______ 174 

Heulandite, effect of cation exchange on thermal behavior_____________________ 89 

Huerto Formation, Colorado, redefinition____ 59 

Idaho, ground water, National Reactor 

Testing Station___________________ 186 

quality of water, National Reactor Testing 

Station __ -------------___________ 186 

stratigraphy, south-central part___________ 1 

structural geology, south-central part_____ 1 

Ion-activity product, dolomite________________ 179 

Ion-exchange capacity, improved determination ___ --------------------------- 93 

Iron, determination in hematitic iron ore_____ 174 

J 

Jurassic, Alaska, oil shale_____________________ 131 

California, geochronology_________________ 105 

structural geology ____________________ _ 

Mississippi, stratigraphy_---------------- 43 

K 

Kentucky, sedimentation, Mammoth Cave___ 141 

L Page 

La Garita Quartz Latite, Colorado, definition_ D57 

M 

Mackinawite, new mineral, properties________ 64 

Maine, geochemical prospecting, Aroostook 

County--------------------------- 96 

Mammoth Mountain Rhyolite, Colorado, 

redefinition ___ -------------------- 59 

Marine organisms, effect of temperature on___ 194 

Maryland, oceanography, Patuxent River 

estuary--------------------------- 194 

Massachusetts, geophysics, Cape Cod________ 118 

stratigraphy, Cape- Cod ___ --------------- 118 

Mineral solubility, in ground water___________ 179 

Miocene, California, paleontology____________ 18 

Mississippi, stratigraphy_---------------- 43 

Mississippi, stratigraphy, southeastern part__ 43 

Mississippian, Idaho, stratigraphy ___________ _ 

Idaho, structural geology_---------------- Nevada, stratigraphy ____________________ _ 

structural geology ___ -----------------

Molybdenum, in aluvium, geochemical 

prospecting ___ -----------------___ 98 

Monazite, thorium and uranium content_____ 128 

Montana, geochemistry, eastern part_________ 73 

Mud:flow deposits, Quaternary, in Chile______ 144 

N 

Nebraska, geochemistry, northwestern part___ 73 

Nelson Mountain Quartz Latite, Colorado, 

redefi.aition__ _ ______ _______ ______ _ 61 

Nevada, geochemistry, Nevada Test Site_____ 93 

geophysics, Las Vegas area. __ ------------ 108 

ground water, Oasis Valley_______________ 189 

quality of water, Oasis Valley____________ 189 

stratigraphy, Esmeralda and Nye Counties_______________________________ 2 4 

northern part_ _______________________ _ 

structural geology, northern part ________ _ 

New Jersey, :floods---------------------------- 202 

New Mexico, sedimentation, Rio Grande_____ 138 

New York, ground water, Albany area_______ 204 

North Carolina, stratigraphy, Burke County_ 38 

North Dakota, geochronology, Williston 

basin ________________ --------_____ 100 

Norway, glacial chronology, Ullsfjord_________ 159 

0 

Ohio, ground water, Springfield area__________ 198 

surface water, Springfield area____________ 198 

Oil shale, Alaska, Jurassic____________________ 131 

Oligocene, Mississippi, stratigraphy_--------- 43 

p 

Paleocene, Mississippi, stratigraphy__________ 43 

Pennsylvanian, Idaho, stratigraphy----------

Idaho, structural geology-----------------

Mississippi, stratigraphy ____ ------------- 43 

Nevada, stratigraphy---------------------

structural geology_-------------------

D221 
D222 

Permian, Idaho, stratigraphy ________________ _ 

Idaho, structural geology_----------------

Mississippi, stratigraphy_---------------- Nevada, stratigraphy ____________________ _ 

structural geology_-------------------

Pierre Shale, Great Plains, cadmium content_ 

Pleistocene, North Carolina, interglacial episode __________________________ _ 

Pliocene, California, paleontology ___________ _ 

California, stratigraphy __________________ _ 

Mississippi, stratigraphy __ --------------- Nevada, stratigraphy ____________________ _ 

Potassium-argon age determinations, California ______________ ----__________ _ 

Canadian Shield area-----------------· __ _ Precambrian, Colorado, petrology ___________ _ 

North Dakota, geochronology ___________ _ 

Q 

Quality of water, effect of tree leaves on _____ _ 

Quaternary, Chile, geomorphology __________ _ 

Massachusetts, stratigraphy _____________ _ 

Mississippi, stratigraphy __ --------------- Norway, glacial chronology ______________ _ 

See also Pleistocene. 

R 

Radiocarbon age determinations, Norway ___ _ 

Rat Creek Quartz Latite, Colorado, redefinition ___ --------------------------- Reservoirs, storage-draft curves ______________ _ 

Rhizophyllum, Silurian and Devonian, North 

America _____________________ ----_ 

Rhyolite flows, determination of flow direction ___ --------------------------- Rubidium-strontium age determinations, 

California ___ ---------------- ____ _ Canadian Shield area ____________________ _ 

Page 

D1 

1 

43 

1 

1 

73 

38 

14 

14 

43 

24 

105 

100 

'28 

100 

181 

144 

118 

43 

159 

159 

60 

192 

149 

70 

105 

100 

SUBJECT INDEX 

5 

St. Kev·in Granite, Colorado, definition ______ _ 

Salt anticlines, Colorado, interpretation of 

growth __________________________ _ 

Sampling error, effects in geochemical prospecting ___________________ ----- __ _ 

Saprolite, thorium and uranium in monazite __ 

Sediment concentrations, spatial and velocityweighted _____________ ------------

Sedimentation, storage of fine sediment in 

islands and point bars ___________ _ 

Seismic studies, island of HawaiL ------------ Nevada, Las Vegas area _________________ _ 

Shallow Creek Quartz Latite, Colorado, definition __ -------------------------- Silurian, North America, paleontology _______ _ 

Showsboe Mountain Quartz Latite, Colorado, definition ________________________ _ 

Solubility determination, in concentrated 

solutions _________________________ _ 

South Dakota, geochemistry, Black Hills 

area __ ---------------------------- Spectrochemical analysis, d-e arc, gas jet _____ _ 

Spectrometry, X-ray fluorescence, in iron 

determination ___ -----------------

Streamflow, regulation by storage ____ --------

relation to ground-water movement ______ _ 

T 

Tatum Limestone Member, Catahoula Sandstone, Mississippi, definition ____ _ 

Tektites, semimicro X-ray fluorescence analysis ____________ -------------------

Television, use in borehole exploration _______ _ 

Temperature studies, ground water, New 

York_----------------------------

modified thermometer for ground water __ 

river water_------------------------------

Page 

D28 

33 

84 

128 

134 

138 

112 

108 

58 

149 

61 

167 

73 

176 

174 

192 

198 

44 

171 

219 

204 

216 

184 

Page 

Tertiary, Colorado, stratigraphy______________ D54 

Colorado, structural geology -------------r 123 

Massachusetts, stratigraphy______________ 118 

See also Eocene, Miocene, Oligocene, 

Paleocene, Pliocene. 

Texas, sedimentation, Rio Grande____________ 138 

Thermometer, "lazy," for ground-water 

studies __ ------------------------- 216 

Thirsty Canyon Tuff, Nevada, definition____ 24 

Thorium, in monazite from saprolite__________ 128 

Tree leaves, effect on water quality___________ 181 

Tuff, zeolitic, ion-exchange capacity_--------- 93 

u 

Uranium, in monazite from saprolite ____ ----- 128 

Utah, geochemical prospecting, Rocky Range_ 79 

v 

Valleriite, from Washington, properties_______ 64 

Vertebrate fossils, Miocene, California________ 18 

Volcanism, Colorado, San Juan Mountains___ 49 

w 

Washington, mineralogy, Snohomish County- 64 

mineralogy, Spokane County_____________ 128 

Wason Park Rhyolite, Colorado, definition___ 59 

West Virginia, quality of water, Cacapon 

River _____ ------------------------ 181 

Wyoming, geochemistry, Black Hills area____ 73 

XYZ 

X-ray fluorescence analysis, small samples____ 171, 
A Page 

Adler, Isidore_------------------------------- D64 

Andersen, B. G __ ---------------------------- 159 

Anderson, R. E. __ --------------------------- 24 

B 

Back, William________________________________ 179 

Barnes, Ivan._------------------------------- 179 

Berner, R. A_________________________________ 64 

Beverage, J. P -------------------------------- 138 

Brown, R. D., Jr_____________________________ 7 

Brown, Robena. __ --------------------------- 171 

Bryant, Bruce________________________________ 38 

c 

Canney, F. C-------------------------------- 96 

Carron, M. K________________________________ 171 

Castillo U., Dctavio ________________________ 144,209 

Cater, F. W ---------------------------------- 33 

Chao, E. C. T-------------------------------- 64 

Christ, C. L---------------------------------- 167 

Coleman, R. G_______________________________ 105 

Collier, C. R __ ------------------------------- 141 

Connor, J. J ---------------------------------- 79, 84 

Cory, R. L.---------------------------------- 194 

Cross, W. P ---------------------------------- 198 

Cummings, David ___ ---------------------___ 70 

Outtitta, Frank______________________________ 171 

D 

Dingman, R. !_______________________________ 209 

Doyel, W. W _______________________________ 209,213 

E 

Eakin, T. E---------------------------------- 189 

Eargle, D. H_ -------------------------------- 43 

Eddy, J. E----------------------------------- 219 

Ekren, E. B---------------------------------- 24 

Evans, H. T., Jr. __ -------------------------- 64 

F 

Falc6n M., Eduardo ___ ---------------------- 144 

Feulner, A. J --------------------------------- 198 

AUTHOR INDEX 

Page 

Flint, R. F ----------------------------------- D141 

G 

Goerlitz, D. F________________________________ 164 

Guy, H. P _ ---------------------------------- 134 

H 

Hardison, C. H_______________________________ 192 

Heath, R. C ________________________________ 204,216 

Hedge, C. E__________________________________ 100 

Helz, A. W___________________________________ 176 

Holmes, G. W________________________________ 159 

Hosterman, J. W_____________________________ 128 

Huffman, Claude, Jr_________________________ 73 

Ingram, Blanche_____________________________ 64 

K 

Klausing, R. L_______________________________ 14 

Koyanagi, R. y______________________________ 112 

L 

Lamar, W. L_________________________________ 164 

Lee, D. E------------------------------------ 105 

Leopold, E. B.------------------------------- 38 

Lewis, G. E---------------------------------- 18 

Lohman, K. E------------------------------- 14 

M 

Malmberg, G. T _ ---------------------------- 189 

Marvin, R. F-------------------------------- 105 

Mead, Cynthia_______________________________ 64 

Miesch, A. T --------------------------------- 79,84 

Milton, Charles______________________________ 64 

N 

Niles, W. W---------------------------------- 174 

Noble, D. C---------------------------------- 24 

Nordin, C. F., Jr_____________________________ 138 

0 Page 

O'Connor, J. T ______________________________ D24 

Oldale, R. N __ ------------------------------- 118 

Oliver, W. A., Jr_____________________________ 149 

Olmsted, F. H_ ------------------------------ 186 

Overstreet, W. C----------------------------- 128 

p 

Pavlides, Louis_______________________________ 96 

Pearson, R. C-------------------------------- 28 

Peterman, Z. E------------------------------- 100 

R 

Rader, L. F ---------------------------------- 73 

Rattli, J. C----------------------------------- 49,54 

Reed, J. C., Jr ___ ---------------------------- 38 

Roberts, R. L-------------------------------- 1 

Roller, J. C---------------------------------- 108 

Rose, H. J ., Jr _ ------------------------------ 171 

s 

Segerstrom, Kenneth_________________________ 144 

Shepard, A. 0-------------------------------- 89 

Simons, D. B-------------------------------- 134 

Slack, K. V _ --------------------------------- 181 

Starkey, H. C-------------------------------- 89,93 

Steven, T. A __ --------------------------- 49, 54, 123 

T 

Tailleur, I. L--------------------------------- 131 

Thomas, D. M_______________________________ 202 

Thomas, H. H_ ------------------------------ 105 

Thomasson, M. R---------------------------- 1 

Tourtelot, H. A______________________________ 73 

Truesdell, A. H______________________________ 167 

Tuttle, C. R_ -------------------------------- 118 

Tweto, Ogden________________________________ 28 

w 

Warr, J. J., Jr________________________________ 128 

Weiler, Louise________________________________ 38 

D223 

U. S. GOVERNMENT PRINTING OFFICE : 1964 0 - 716-626