Depositional Systems of a Synorogenic 

Continental Deposit The Upper Paleocene and 

Lower Eocene Wasatch Formation of the 

Powder River Basin, Northeast Wyoming

U.S. GEOLOGICAL SURVEY BULLETIN 191 7-H

rWr-^^^m ' '- - '- - ' ' ' - - - . .-.- -: . . TV-.a

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Chapter H

Depositional Systems of a Synorogenic 

Continental Deposit The Upper Paleocene and 

Lower Eocene Wasatch Formation of the 

Powder River Basin, Northeast Wyoming

By DAVID SEELAND

A multidisciplinary approach to research studies of sedimentary 

rocks and their constituents and the evolution of sedimentary basins, 

both ancient and modern

U.S. GEOLOGICAL SURVEY BULLETIN 1917 

EVOLUTION OF SEDIMENTARY BASINS POWDER RIVER BASIN
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

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

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

UNITED STATES GOVERNMENT PRINTING OFFICE: 1992

For sale by

Book and Open-File Report Sales 

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Library of Congress Cataloging-in-Publication Data

Seeland, David A.

Depositional systems of a synorogenic continental deposit; the Upper 

Paleocene and Lower Eocene Wasatch Formation of the Powder River Basin, 

northeast Wyoming/ by David Seeland.

p. cm. (U.S. Geological Survey bulletin ; 1917) 

(Evolution of sedimentary basins Powder River Basin ; ch. H) 

Includes bibliographical references.

Supt. of Docs, no.: I 19.3:1917

1. Sedimentation and deposition Powder River Basin (Wyo. and 

Mont.) 2. Geology, Stratigraphic Paleocene. 3. Geology, 

Stratigraphic Eocene. 4. Wasatch Formation. 5. Coal Powder River Basin 

(Wyo. and Mont.) 6. Uranium ores Powder River Basin (Wyo. and 

Mont.) I. Title. II. Series. III. Series: Evolution of sedimentary 

basins Powder River Basin ; ch. H. 

QE75.B9 no. 1917 H 

[QE571]

557.3 s dc20 91-26305 

[551.7'83'09787] CIP
CONTENTS

Abstract HI

Introduction HI

Geologic setting H2

Grain-size and grain-shape analysis H2

Conglomerate H2

Sandstone H6 

Facies studies H9 

Paleocurrents and paleogeographic synthesis H12

Methods H12

Results H17

A western-basin trunk stream in Wasatch time? H17 

Paleogeographic settings of coal and uranium deposits H17 

Conclusions H19 

References cited H19

FIGURES

1-3. Maps showing:

1. Five proposed locations for the major basin-axis trunk stream of Wasatch 

Formation time or Wasatch and late Fort Union Formation time H3

2. Interpretive drainage in late Paleocene time H4

3. Generalized geologic structures in and near the Powder River Basin H5

4. Chart showing Late Cretaceous through early Tertiary stratigraphic 

nomenclature for the Powder River Basin H6

5. Map showing maximum clast size in the Wasatch Formation at sample 

localities having granule-size or larger clasts H7

6. Histograms of mean sand-grain regularity, elongation, and size for Wasatch

Formation sandstone H8 

7-14. Maps showing:

7. Mean-elongation isopleths of sand grains from Wasatch Formation 

sandstone H9

8. Mean-regularity isopleths of sand grains from Wasatch Formation 

sandstone H10

9. Mean-size isopleths of sand grains from Wasatch Formation 

sandstone Hll

10. Sandstone percentage in the Wasatch Formation H13

11. Vector-mean crossbed-dip directions in the Wasatch Formation H14

12. Moving-average crossbed-dip directions in the Wasatch 

Formation HIS

13. Interpreted streams for Wasatch Formation time H16

14. Relationship between early Eocene drainage patterns of the Bighorn, 

Wind River, Shirley, and Powder River Basins HIS

Contents III

EVOLUTION OF SEDIMENTARY BASINS POWDER RIVER BASIN

Depositional Systems of a Synorogenic 

Continental Deposit The Upper Paleocene and 

Lower Eocene Wasatch Formation of the 

Powder River Basin, Northeast Wyoming

By David Seeland

Abstract

Fluvial sedimentary rocks of the Wasatch Formation of 

the Powder River Basin had major sources in the Laramide 

uplifts that nearly surround the basin on the east, south, and 

west. Paleocurrent study based on crossbedding in sandstone 

of stream-channel origin indicates that basin paleoslope 

directions and the intersecting paleoslopes define two major 

drainages. The first and largest was an extrabasinal stream that 

was the major longitudinal river of the upstream Wind River 

Basin. It flowed across the Casper arch and into the Powder 

River Basin. This longitudinal basin-axis trunk stream of the 

Powder River Basin, termed the Wind River of Eocene time, 

flowed from south to north through the westernmost basin. The 

other major stream flowed from southeast to northwest and 

was the major tributary of the Wind River of Eocene time.

Three major alluvial depositional systems can be defined 

using paleocurrent and facies analysis: (1) a distal mud-rich 

alluvial plain with a source terrane to the east in the Black 

Hills, (2) a proximal sand-rich alluvial plain-alluvial fan with a 

source to the south in the Laramie Mountains, and (3) a 

stream-dominated proximal to distal alluvial fan with a source 

to the west in the Bighorn Mountains.

Grain-shape and grain-size studies supplemented the 

paleocurrent study and corroborated transport directions. An 

area of large tributaries to the Wind River of Eocene time is 

indicated by an area of less-regular sand grains in the western 

basin near Buffalo.

Major coal and uranium deposits are spatially related to 

the depositional systems of the basin. Known Wasatch 

Formation uranium deposits are limited to the proximal 

alluvial plain-distal alluvial fan depositional system of the 

southern basin. The source of the uranium was probably

Manuscript approved for publication July 12, 1991.

granitic detritus of the Wasatch sandstone and uraniferous tuff 

of Oligocene age that overlap permeable Wasatch sandstone 

units in the southernmost basin. The thickest coal bed known 

in the United States originated in a peat swamp that paralleled 

the basin-axis trunk stream. Other coal-forming swamps were 

more abundant in the vicinity of the basin axis than in areas 

remote from the axis.

INTRODUCTION

The synorogenic fluvial and paludal rocks of the 

upper Paleocene and lower Eocene Wasatch Formation in 

the Powder River Basin contain large deposits of coal and 

uranium. These rocks also record the culmination of Laramide tectonic events marked by subsidence in the basin and 

uplift of the bounding structures. This study establishes the 

early Eocene paleogeography of the basin using a two-part 

approach consisting of (1) sedimentary particle-shape and 

-size analysis, and (2) paleocurrent studies.

Because fluvial depositional systems are the key to 

understanding the origin and localization of large deposits 

of coal and uranium, many investigators have developed 

paleogeographic frameworks for all or part of the basin (fig. 

1) that attempt to explain the origin of these deposits. 

Childers (1970) sketched an early Eocene paleogeographic 

map of Wyoming (which included parts of the Wasatch, 

Wind River, and Battle Spring Formations) based on 

regional facies distributions. Galloway (1979) introduced a 

late Paleocene and early Eocene (Tongue River Member of 

Fort Union Formation and Wasatch Formation) paleogeographic framework based on a 50-log subsurface study 

in the southern basin. Galloway's trunk stream was 

extended northward by Flores and Ethridge (1985) and 

Flores (1986). Warwick and Flores (1987) postulated a

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming H1
north-flowing early Eocene basin-axis trunk stream in the 

central basin. Seeland (1976) suggested westerly to 

northwesterly flowing streams in the eastern and central 

parts of the Wasatch outcrop area (the central part of the 

topographic basin), with the trunk stream located in the 

westernmost basin. Because of these conflicting paleogeographic frameworks showing the "western" trunk stream 

(Seeland, 1976) or the "central" trunk stream (Galloway, 

1979; Flores and Ethridge, 1985; Flores, 1986; Warwick 

and Flores, 1987), the total number of paleocurrent 

localities in the Wasatch Formation for this study were 

increased by about 50 percent over the number used in 

Seeland (1976), with recent supplemental field work 

concentrated in the eastern part of the Wasatch Formation 

outcrop (the central part of the topographic basin).

Comparison of the early Eocene paleogeography of 

the basin (Seeland, 1976) (fig. 1) with the late Paleocene 

(Tongue River Member of the Fort Union Formation) 

paleogeography (Seeland, 1988; Seeland and others, 1988) 

(fig. 2) shows that the two are very different, precluding 

their combination as suggested by Galloway (1979) and as 

followed by most of the other proponents of the eastern 

trunk stream. These differences also preclude making paleogeographic inferences from a sand-percentage map of the 

combined Wasatch Formation and Tongue River Member 

of the Fort Union Formation (Flores and Ethridge, 1985).

GEOLOGIC SETTING

The Powder River topographic basin of northeastern 

Wyoming and southern Montana is defined by the Bighorn 

Mountains on the west, the Black Hills on the east, and the 

Laramie Mountains and the Hartville uplift on the south 

(fig. 1). On the north, the Miles City arch structurally 

separates the Powder River Basin from the Williston basin 

of eastern Montana and North Dakota (fig. 3).

Following the eastward retreat of the Western Interior 

Cretaceous epicontinental sea, thousands of meters of 

mostly fluvial sediments were deposited, including the 

Upper Cretaceous Lance and Hell Creek Formations, the 

Paleocene Fort Union Formation, and the Paleocene (local) 

and lower Eocene Wasatch Formation (fig. 4). The Wasatch 

Formation is overlain by remnants of the Oligocene White 

River Group, which formerly covered most of the basin.

The Wasatch Formation consists of alluvial mudstone 

and sandstone. In most places mudstone of overbank flood 

plain origin predominates and makes up about two-thirds of 

the unit. Crossbedded sandstone that becomes finer grained 

upwards is interpreted as channel deposits of meandering to 

anastomosed streams and makes up much of the remainder 

of the unit. Minor constituents include coarse conglomerate, 

the Moncrief and Kingsbury Members of the Wasatch 

Formation, deposited in alluvial fans along the western 

margin of the basin, and carbonaceous shales and thick coal 

beds deposited in extensive, long-lived, low-lying swamps.

The maximum preserved thickness of the Wasatch is about 

900 m (3,000 ft) along the present structural axis of the 

basin (fig. 3) about 8 km southeast of Buffalo, Wyo.

GRAIN-SIZE AND GRAIN-SHAPE ANALYSIS

Conglomerate

Maximum clast sizes were determined at all field 

localities where conglomeratic sandstone was present. Clast 

shape was not studied. The maximum-clast-size map (fig. 5) 

shows all localities with clasts larger than 3 mm (granules).

Two areas have conglomeratic sandstone: (1) the 

western part of the basin adjoining the Bighorn Mountains, 

and (2) the southern part of the basin where the most 

probable source was the Laramie Mountains, but with the 

Hartville uplift a second, less likely source. Granules at the 

three northernmost localities in the southern part of the 

basin most likely have a southern, rather than a Black Hills, 

source. This conclusion is based on a lack of conglomerate 

along the eastern part of the Wasatch Formation outcrop 

north of these three localities. This eastern nonconglomeratic Wasatch is at least as close to a Black Hills source of 

conglomerate as are the three granule localities. Probable 

conglomerate source terranes are discussed in the section on 

"Paleocurrents and Paleogeographic Synthesis."

The Kingsbury Conglomerate Member and the 

overlying Moncrief Member of the Wasatch Formation crop 

out along and on the Bighorn Mountains uplift. They are 

coarsely conglomeratic and record uplift and progressive 

unroofing of the Bighorn Mountains. Kingsbury clasts are 

predominantly carbonate rocks derived from the Ordovician 

Bighorn Dolomite and the Mississippian Madison 

Limestone (Nelson, 1968), and the Moncrief clasts are 

predominantly crystalline rocks (Hoppin and Jennings, 

1971; Sharp, 1948). Carbonate boulders as large as 1 m 

were found at Kingsbury Ridge, 10 km south-southwest of 

Buffalo. Conglomerate and conglomeratic sandstone are 

interbedded with sandstone and minor amounts of mudstone 

at Kingsbury Ridge.

Although Hoppin and Jennings (1971) and Mapel 

(1959) stated that crystalline-rock fragments are uncommon 

in the Kingsbury, they are present in fairly large amounts at

Figure 1 (facing page). Map showing five proposed locations 

for the major basin-axis trunk stream of Wasatch Formation 

time or Wasatch and late Fort Union Formation time 

combined, Powder River Basin, Wyoming and Montana. A, 

Wasatch time only, Seeland (1976); B, Wasatch time only, 

Warwick and Flores (1987); C, Wasatch and late Fort Union 

time combined, Flores and Ethridge (1985); D, Wasatch and 

late Fort Union time, combined, Flores (1986); E, Wasatch 

time(?) and late Fort Union time combined, Galloway (1979); 

F, Wasatch time only, Childers (1970). Tw, uppermost Paleocene and lower Eocene Wasatch Formation; Twr, lower 

Eocene Wind River Formation.

H2 Evolution of Sedimentary Basins Powder River Basin
O
107° 106° 105° 104°

45°

44°

43°

\ HARTVILLE

\ UPLIFT

9

II

£ 

I!c/5 15

50 KILOMETERS

I____I____I

25 MILES

Figure 2. Interpretive stream map for the late Paleocene based on paleocurrent measurements and distribution of thick coal, 

Powder River Basin, Wyoming and Montana. Paleocurrent measurements from Seeland and others (1988). Coal distribution 

in the Tongue River Member simplified from Ayers and Kaiser (1984). Contours show thickness of single thickest coal; contour 

interval 40 feet. Pattern indicates maximum coal thickness is less than 20 feet, and shaded area indicates maximum coal 

thickness is greater than 100 feet. Tw, uppermost Paleocene and lower Eocene Wasatch Formation.

H4 Evolution of Sedimentary Basins Powder River Basin
110

CANADA 

UNITED STATES

CRAZY

MOUNTAINS

BASIN

NORTH DAKOTA 

"s6TJfH~DAKOTA

MONTANA 

WYOMING

|_ _SOUJH DAKOTA 

""NEBRASKA

GRANITE

MOUNTAINS

UPLIFT

_ WYOMING_ __ _

UTAH" ~"| " COLORADO

44° -

42° -

Figure 3. Generalized geologic structures in and near the Powder River Basin, Wyoming and Montana. 

Structure contours on top of the Precambrian, contour interval 5,000 ft (1,500 m).

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming H5
TERTIARY

CRETACEOUS

OLIGOCENE

EOCENE

PALEOCENE

White River Formation

(West) ^ 

Moncrief ^. 

Member <^ V

Kingsbury <;> Fl 

Conglomerate Member 1^.

Fort Union 

Formation

(East)

Vasatch 

>rmation

Tongue River 

Member

Lebo Member

Tullock Member

Lance Formation 

(Hell Creek Formation in Montana)

Figure 4. Late Cretaceous through early Tertiary stratigraphic 

nomenclature for the Powder River Basin, Wyoming and 

Montana.

Kingsbury Ridge. On the south side of the ridge, an 80-m 

measured section contains as much as 30 percent graniticrock clasts. The granitic-rock clasts are smaller than the 

carbonate clasts and have a maximum diameter of about 100 

mm. The presence of granitic clasts throughout the section 

suggests that the locality represents the distal part of a 

prograding alluvial fan. Increasingly proximal fan 

sediments should contain an increasing proportion of Paleozoic carbonate clasts as was seen in the Kingsbury Member 

northwest of Buffalo, where the clasts are entirely carbonate 

rocks.

Basin-axis subsidence and a concomitant decrease in 

paleoslope have been cited as reasons for restriction of 

conglomerate deposition to the proximal parts of a 

sedimentary basin (Kraus, 1985; Paola, 1988). In the 

western part of the basin, subsidence along the basin axis 

and the development of longitudinal drainage inhibited 

transport across the axis in a basinward (eastward) direction, 

as shown by conglomeratic debris extending only about 30 

km basinward from the Bighorn uplift. In contrast, in the 

southern part of the basin, where transport was northward 

and subparallel to the structural axis of the basin, conglomeratic sandstone is found as far as 100 km north of the 

Laramie Mountains.

SANDSTONE

Wasatch Formation sandstone samples were collected 

from crossbed sets at 46 field localities in the basin (fig. 7). 

The samples were treated with dilute hydrochloric acid to 

remove carbonate cement, washed, and dried. Grain-size 

and grain-shape analyses were performed with an electronic 

image analysis system. Sawyer (1977) described the system,

which consists of a microscope; a video scanner, an 

electronic system that obtains maximum and minimum 

grain-length, grain-perimeter, and grain-area measurements; 

and a small computer that records and stores the data and 

makes statistical calculations. The image analyzer is unique 

in that it can provide quantitative measures of grain shape 

that would otherwise be much too time consuming to 

obtain. The image analyzer requires about 20 minutes per 

sample to obtain the data used for this investigation.

Parameters that were determined include two measures of grain shape (100 grains per sample) and maximum 

grain length (250 grains per sample). Grain elongation is the 

shortest diameter (S) divided by the longest diameter (L), or 

S/L. As S/L decreases, the grains are more elongated, 

indicating that the sample locality was closer to the source 

area. The other shape factor is the area (A) divided by the 

perimeter squared (P2), or A/P2, which is a measure of grain 

regularity. A circle has an A/P2 of 0.08; a daisy would have 

a much lower A/P2. As A/P2 decreases, it indicates 

decreasing regularity of the grain, also suggesting that the 

source of the grains was closer to the locality where the 

sample was collected.

The overall mean S/L of 46 samples (4,600 grains) 

from 46 field localities is 0.746. Figure 6 is a histogram 

showing the variability of mean S/L. An isopleth map of 

these values (fig. 7) shows that three areas of the basin have 

an S/L of less than 0.700 (relatively more elongate); each 

area is close to one of the major local sediment source areas: 

the Black Hills, the Laramie Mountains, and the Bighorn 

Mountains. The areas of relatively less elongate sand grains 

(S/L near 0.740) in the west-central part of the basin may be 

due to deposition of far-traveled, less elongate sand grains, 

whose ultimate source was the uplifts surrounding the Wind 

River Basin.

A downstream increase in roundness (less elongation) 

as postulated here is a consequence of selective transport 

rather than of abrasion during transport. Rounding by 

abrasion during transport is very slow. Kuenen (1959) found 

that 20,000 km of simulated transport caused angular, 

medium-grained sand to lose less than one percent of its 

weight to abrasion and solution. The rate of rounding must 

also decrease as the grains become less angular. Only 

selective transport or source differences can account for the 

observed abrupt shape changes.

The overall mean sand-grain regularity (A/P2) of 46 

samples is 0.059. The sand-grain regularity map (fig. 8) 

shows increasing regularity in downstream directions as 

defined by the paleocurrent analysis. The least regular 

samples are found in the southern part of the basin. Both the 

A/P2 isopleth map (fig. 8) and the paleocurrent maps (figs. 

11 and 12) indicate northerly transport in this area; the 

source of most of these irregular grains must have been the 

Laramie Mountains, although the Hartville uplift may have 

been an auxiliary source. The A/P2 isopleth map also shows 

a wide area of westward-decreasing regularity in the eastern

H6 Evolution of Sedimentary Basins Powder River Basin
43° -

50 KILOMETERS

0 25 MILES

EXPLANATION 

Sample locality showing maximum clast-size interval

 Less than 3 mm

O 3-16 mm

O 16-32 mm

32-64 mm

64-128 mm

Figure 5. Maximum clast size in the Wasatch Formation at all sample localities having granule-size (3 mm) or larger clasts, 

Powder River Basin, Wyoming and Montana. Tw, uppermost Paleocene and lower Eocene Wasatch Formation.

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming H7
part of the basin, indicating, as do the paleocurrents, a 

westward-sloping alluvial plain whose streams carried 

sediment westward from the Black Hills. The westward 

decrease in regularity is mostly due to selective transport.

Major basinward inflections of the A/P2 isopleths 

allow major tributary streams to be inferred (Seeland, 

1978b). Multiple major tributaries entered the Powder River 

Basin from the Bighorn Mountains in the area near Buffalo 

as indicated by a strong basinward inflection in the A/P2 

isopleths (fig. 8), which reflects a source of irregular sand 

grains. This conclusion is supported by the presence of a 

broad area of coarse lower Eocene conglomerate along the 

mountain front, the presence of a paleovalley, and the 

present topography and geology of the Bighorn Mountains. 

The areal extent of the Kingsbury Conglomerate Member is 

centered on the basinward A/P2 inflection near Buffalo (fig. 

8). Evidence for an ancestral Clear Creek just west of 

Buffalo was found by Nelson (1968). He discovered the 

floor and remnants of the sides of a wide valley filled with 

Moncrief Member approximately along the present course 

of Clear Creek and its North Fork.

The north-central part of the Bighorn Mountains is 

presently the highest part of the range and probably was also 

the highest part of the range in Eocene time. The range 

should have received much orographic precipitation during 

the Eocene. Eocene drainages of the Wind River Range 

have survived to the present (Seeland, 1978b), indicating 

that the long-term survival of early Tertiary topography is 

possible. Thus, present topography suggests that major early 

Eocene streams flowed out of the north-central Bighorn 

Mountains. The coarse conglomerates of the Kingsbury 

Conglomerate and Moncrief Members adjacent to the northcentral Bighorn Mountains are additional evidence that the 

topographic relief was at a maximum in the north-central 

part of the range in the early Eocene, as it is today.

The grand-mean grain size of 46 sandstone samples is 

2.29 phi units (fine sand), based on the measurement of the 

maximum length of 11,500 grains. A mean-sand-size isopleth map (fig. 9) shows grain-size increases toward the 

eastern (Black Hills) and southern (Laramie Mountains) 

margins of the Wasatch Formation outcrop area, reflecting 

probable sources in or near the Black Hills and Laramie 

Mountains. The map does not show the Bighorn Mountains 

source that is obvious from the maximum clast size, 

elongation, and regularity maps (figs. 5, 7, 8) as well as the 

paleocurrent maps (figs. 11 and 12) presented in the next 

section of this report. Low stream gradients and competency 

along the basin axis may account for this anomaly.

Figure 6 (facing column). Histograms of mean sand-grain 

regularity, elongation, and size for the Wasatch Formation 

sandstone at 46 localities, Powder River Basin, Wyoming and 

Montana.

MEAN GRAIN ELONGATION (S/L)

1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 

MEAN GRAIN SIZE (PHI)

>- 20 

O

n

8 &

MEAN GRAIN REGULARITY (A/P2)

H8 Evolution of Sedimentary Basins Powder River Basin
108° 107° 106° 105° 104°

0 50 KILOMETERS 

I________ FTII 

0 25 MILES

Figure 7. Isopleth map of mean elongation (S/L) of sand grains from Wasatch Formation sandstone, Powder River Basin, 

Wyoming and Montana. Contour interval is 0.020. Dots are sample localities. Tw, uppermost Paleocene and lower Eocene 

Wasatch Formation.

FACIES STUDIES deposits, interbedded sand and fine-grained deposits,

medium- to coarse-sand deposits, and conglomerate

Sharp and Gibbons (1964) separated the facies seen at deposits. The sandier areas as mapped by Sharp and 

the outcrop of the Wasatch Formation into fine-grained Gibbons (1964) are in the southern and eastern parts of the

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming H9
108° 107

43° -

50 KILOMETERS

i i i r

25 MILES

Figure 8. Isopleth map of mean regularity (A/P2) of sand grains from Wasatch Formation sandstone, Powder River Basin, 

Wyoming and Montana. Contour interval is 0.002. Dots are sample localities. Tw, uppermost Paleocene and lower Eocene 

Wasatch Formation.

Wasatch outcrop area. Those areas have the Laramie 

Mountains-Hartville uplift and the Black Hills, respectively, 

as sources, on the basis of transport directions (fig. 11). The 

coarser sands of the southern area most likely have a

granitic source, and the eastern sand and fine-grained 

deposits have a source composed of a combination of older 

sedimentary rock, schist, and minor granite. This conclusion 

is partly based on the mean sand-grain regularity map (fig.

H10 Evolution of Sedimentary Basins Powder River Basin
108° 107 106°

43° -

50 KILOMETERS

\ i r

25 MILES

Figure 9. Isopleth map of mean size (phi) of sand grains from Wasatch Formation sandstone, Powder River Basin, Wyoming 

and Montana. Contour interval is 0.2. Dots are sample localities. Tw, uppermost Paleocene and lower Eocene Wasatch 

Formation.

8), which shows that the most irregular grains are in the 

southern part of the basin, and substantially more regular 

grains are in the Gillette area. The finer and more regular 

grains are thought to be derived from Paleozoic and

Mesozoic sandstone and the predominantly schistose Precambrian rocks of the Black Hills. The less regular sand 

grains in the southern part of the basin were produced by 

weathering and erosion of the Precambrian granitic rocks of

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming H11
the Laramie Mountains and, to a lesser extent, the granitic 

rocks of the Hartville uplift.

Bendix Field Engineering Corporation, Geology 

Division Staff (1976) made sandstone-shale ratio maps for 

each of seven 150-m (500-ft) thick slices of the Wasatch 

Formation beginning at the base. An overall sandpercentage map of the Wasatch should provide a reliable 

representation of sand distribution, because stability over 

time of lithofacies composition and paleostream directions 

is indicated by the work of Santos (1981), and stability over 

time of lithofacies is evident in the slice maps of Bendix 

Field Engineering Corporation, Geology Division Staff 

(1976). The sand-percentage map (fig. 10) was prepared 

from the seven interval maps of Bendix Field Engineering 

Corporation, Geology Division Staff (1976) for the northern 

half of the basin. A 16-km (10-mi) grid was superimposed 

on each slice map, and an interpolated value was recorded 

for each applicable intersection for each slice. The mean 

ratio for the entire stack of slices was determined at each 

grid intersection and the results were contoured (fig. 10).

The overall sand percentage map for the northern half 

of the Wasatch Formation outcrop area shows two areas 

with greater than 50 percent sand. The southern of the two 

areas seems to be the northern extension of the north-south 

sand trend mapped by Raines and Santos (1980) in the 

southern Wasatch outcrop area (fig. 10). The northern of the 

two areas with more than 50 percent sand is centered about 

12 km northeast of Buffalo. Although its western part may 

be related to the early Eocene basin-margin conglomerates 

and the central part overlies the inferred course of the Wind 

River of Eocene time, its northeastern extension, lying in 

the distal part of the area of the basin having a Black Hills 

source area, is unexplained.

Santos (1981) made a detailed facies study of the 

Wasatch Formation based on study of 1,050 uraniumexploration geophysical logs in the southern Powder River 

Basin. He made five separate facies maps for 93-m (300 ft) 

slices beginning 186 m (600 ft) below the base of the School 

House coal about at the Wasatch-Fort Union contact and 

extending 450 m (1,500 ft) upward. He found that the 

distribution of the sandy facies in all five slices indicates 

northerly trending paleostreams. The sand trends from 

Santos' (1981) facies study corroborates the paleostream 

directions inferred from crossbedding dip directions 

described later in this report. Furthermore, the relative 

stability of paleoflow directions through 450 m (1,500 feet) 

of Wasatch, about 50 percent of the maximum preserved 

thickness in the basin, supports the validity of this study, 

which integrates paleocurrent data collected throughout the 

entire stratigraphic range of the Wasatch Formation.

Raines and others (1978) and Raines and Santos 

(1980) published lithofacies maps for depths of 0-92 m and 

92-183 m below the present land surface for the southern 

half of the Wasatch outcrop area. Their 0-92-m map was 

generalized on figure 10. The 0.5 sandstone-mudstone ratio

(30 percent sandstone) on both lithofacies maps seems to 

separate the Black Hills and Laramie Mountains source 

areas as determined from the following paleocurrent study.

PALEOCURRENTS AND 

PALEOGEOGRAPHIC SYNTHESIS

Methods

Orientations of 953 crossbeds were determined at 74 

localities in the upper Paleocene and lower Eocene Wasatch 

Formation as mapped on the "Geologic Map of Wyoming" 

(Love and Christiansen, 1985). At most outcrops the 

orientation of all exposed and accessible crossbed sets was 

determined to decrease measurement bias. A compass and 

levels crossbed-measuring device was used to determine 

orientations. This device made more crossbeds measureable, regardless of the relationship between orientation and 

the rock surface, thus decreasing measurement bias 

introduced by outcrop orientation. The friable nature of 

many outcrops permitted three-dimensional exposure of 

almost all crossbeds by grooving the outcrop surface, if 

corners or natural recesses did not allow determination of 

crossbed orientation. Orientations of trough-crossbed axes 

were determined wherever possible. A programmable 

calculator was used to calculate locality vector mean, 

crossbedding dip direction, and vector strength at each 

outcrop following the procedures of Reiche (1938). Each 

crossbed dip direction at a locality was assigned a unit 

length, and these vectors were trigonometrically added head 

to tail. The resultant is the vector mean, and the length of the 

resultant divided by the number of measurements is the 

vector strength, a measure of the spread of the dip 

directions. If all the crossbed dip directions at a locality 

have the same orientation, the vector strength is one; if the 

crossbed dip directions have a random orientation, then the 

vector strength is zero.

Fluvial-transport directions are implied by the vectormean crossbed dip directions. The vector-mean map (fig. 

11) is thus a fluvial-transport-direction (or paleocurrent) 

map. The vector-mean map was smoothed using the moving 

average technique (Pelletier, 1958; Potter and Pettijohn, 

1977) with an 8-m grid size (fig. 12). The technique may 

repeat a single divergent vector-mean direction as many as 

four times, most likely in marginal areas of the map but also 

in more centrally located areas of sparse data. In order to 

minimize this problem, the two vector-mean directions 

outside, but closest to the center, of the block of four 

squares were used to perform a three-component vector 

summation. If a four-square block contained two vectormean localities, then one locality outside but closest to the 

center of the group was used to perform a three-component 

vector summation.

H12 Evolution of Sedimentary Basins Powder River Basin
108° 107° 106° 105° 104°

45°

44C

43°

0 50 KILOMETERS

i j__i

T I I I

0 25 MILES

Figure 10. Sandstone-percentage map of the Wasatch Formation, Powder River Basin, Wyoming and Montana. Patterned area 

has more than 30 percent sandstone from the ground surface to 92-m depth; data modified from Raines and Santos (1980). 

Contours show percentage of sand in the Wasatch Formation, derived from data of Bendix Field Engineering Corporation, 

Geology Division Staff (1976); contour interval is 10 percent; contours are dashed where extrapolated outside of the present 

outcrop of the Wasatch Formation (Tw).

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming HI 3
108° 107° 106° 105° 104°

45C

44C

43°

50 KILOMETERS 

J

0 25 MILES

Vector 

Strength EXPLANATION 

1.0 0.5 0 , jj 

U i 4 Arrow is vector-mean crossbedding

dip direction and vector strength 

is proportional to length of arrow

Figure 11. Vector-mean crossbed-dip directions in the Wasatch Formation, Powder River Basin, Wyoming and Montana. Tw, 

uppermost Paleocene and lower Eocene Wasatch Formation.

H14 Evolution of Sedimentary Basins Powder River Basin
43° -

50 KILOMETERS

0 25 MILES

Figure 12. Moving-average crossbed-dip directions in the Wasatch Formation, Powder River Basin, Wyoming and Montana. 

Grid size is 8 km. Arrows are centered on grid intersections, as explained in text. Tw, uppermost Paleocene and lower Eocene 

Wasatch Formation.

The interpretive map (fig. 13) was constructed using 

information from both the vector-mean and moving-average 

maps. In areas of contradictions between the two maps,

stream-flow directions from the vector-mean paleocurrent 

map were given precedence in the construction of the 

interpretive paleogeographic map.

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming H15
108° 107° 106° 105° 104°

45C

44C

43°

50 KILOMETERS

i i i

25 MILES

Figure 13. Interpretive paleogeographic stream map for the latest Paleocene and early Eocene (Wasatch) Formation time, 

Powder River Basin, Wyoming and Montana. Relative size of streams is proportional to line width. Meandering or 

anastomosed nature of streams not shown. Tw, uppermost Paleocene and lower Eocene Wasatch Formation; Twr, lower 

Eocene Wind River Formation.

H16 Evolution of Sedimentary Basins Powder River Basin
Results

In the broadest sense, drainage was northward out of 

the Powder River Basin. The latest Paleocene and early 

Eocene depositional systems of the Powder River Basin are 

defined by two trunk streams: (1) the south-to-north Wind 

River of early Eocene time, an extrabasinal stream that 

followed the primary depositional and structural axis of the 

basin, and (2) a northwest-flowing intrabasinal stream 

following a secondary basin axis (fig. 13). These framework 

streams carried bed loads to mixed loads, and the streams 

probably meandered, as evidenced by sandy channel 

deposits that become finer upwards enclosed within 

extensive fine-grained overbank deposits.

The two streams define three alluvial depositional 

systems: (1) a distal mud-rich alluvial plain with westwardflowing streams and a Black Hills source area, (2) a 

proximal sand-rich alluvial plain-distal alluvial fan with 

northward-flowing streams and a Laramie Mountains 

source area, and (3) a stream-dominated proximal to distal 

alluvial fan with eastward-flowing streams and a Bighorn 

Mountains source area (fig. 13).

The Black Hills provenance area had been much 

reduced in size by post-Eocene (probably Pliocene to 

recent) basin excavation. Because of early Eocene basin 

asymmetry, it is the largest of the three depositional 

systems. Stream directions in the Black Hills area were 

relatively constant. The Laramie and Bighorn Mountains 

depositional systems were smaller, were closer to their 

respective source terranes, and had more variable stream 

directions.

Swamps were associated with all three depositional 

systems. Precipitation was adequate to allow the 

development of raised swamps anywhere in the basin 

(Ethridge and others, 1981; Flores, 1981; Warwick, 1985; 

Pocknall and Flores, 1987). Low-lying swamps were 

formed mostly in the western part of the basin where coals 

as much as 80 m thick (Obernyer, 1978) attest to paleogeographic stability and continuous subsidence.

Understanding the regional paleogeography requires 

an examination of the relationship of the outlet drainage of 

the Wind River basin to the inlet drainage of the Powder 

River Basin. Seeland (1978a) postulated that the Wind 

River of Eocene time, the master stream of the Wind River 

basin, left the northeastern basin and flowed eastward across 

the Casper arch into the Powder River Basin (fig. 14). In a 

preliminary version of this paper, Seeland (1976) 

concluded, based on the paleocurrents of the Powder River 

Basin and on the similarity between the textural 

characteristics of the sandstone of the lower Eocene Wind 

River Formation in the eastern Wind River basin and the 

western Powder River Basin, that the Eocene Wind River 

entered the southwestern Powder River Basin and continued 

northward along the west side of the basin near the present 

structural axis (fig. 14). This conclusion is supported by

lithofacies interpretations near the present structural axis 

(Toomey, 1977) and results of paleocurrent studies 

(Obernyer, 1980).

A Western-Basin Trunk Stream in 

Wasatch Time?

Paleoslope and stream patterns of the uppermost 

Paleocene and lower Eocene Wasatch Formation (fig. 14 

and Seeland, 1976) and the upper Paleocene Tongue River 

Member of the Fort Union Formation (Seeland, 1988; 

Seeland and others, 1988) are similar in the southernmost 

Powder River Basin but are significantly different to the 

north. Flores (1986) extended Galloway's (1979) drainage 

axis for the combined Tongue River and Wasatch northward 

about to the Montana State line, continuing the assumption 

that the paleogeography for these two units is the same.

Warwick and Flores (1987) measured 84 crossbed 

orientations at an unstated number of localities and 

suggested a north-northwest stream flow in an area of the 

Wasatch west of Gillette. Their studies locate the northflowing basin-axis master stream about 50 km east of the 

position suggested herein and by Seeland (1976) (figs. 1, 

13). Positioning the master stream this far east implicitly 

denies west-flowing drainage in a large area of the basin, as 

documented in this paper.

In summary, the expanded paleocurrent evidence of 

this study continues to support a depositional basin axis and 

associated trunk stream in the westernmost part of the 

Powder River Basin during latest Paleocene and early 

Eocene (Wasatch) time (fig. 13). The proponents of a trunk 

stream in the approximate center of the Wasatch outcrop 

area (fig. 1) commonly have made regional inferences from 

local studies and have based Wasatch Formation paleogeography on the assumption that it was nearly identical to 

the paleogeography of Tongue River Member time (fig. 2). 

This paper demonstrates that the assumption is untenable on 

the basis of regionally comprehensive evidence and that the 

Wasatch-time basin axis was about 75 km west of the 

Tongue River-time axis.

PALEOGEOGRAPHIC SETTINGS OF 

COAL AND URANIUM DEPOSITS

Economic deposits of coal and uranium are common 

in the basin. Most of the uranium deposits are in the 

Wasatch Formation, and most of the coal deposits are in the 

Fort Union Formation. The location of the coal and uranium 

deposits of the Wasatch are directly related to the 

depositional systems of the Wasatch.

Low-lying peat swamps that formed economic coal 

beds were most likely to form in the wettest and leastsloping parts of the basin near major streams (Ethridge and

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming H17
111 104°

BEARTOOTH 

MOUNTAI

WIND RIVER OF EARLY 

EOCENE TIME

0 50 KILOMETERS

i _____I I I I I

0 25 MILES

Figure 14. Relationship between early Eocene drainage patterns of the Bighorn, Wind River, Shirley, and Powder River Basins, 

Wyoming and Montana. Tw, uppermost Paleocene and lower Eocene Wasatch Formation.

others, 1981). As could be predicted from this hypothesis, 

coal deposits of the Wasatch are thicker and more persistent 

in the western and central basin (Glass, 1980). The DeSmet 

(Healy) coal bed locally exceeds 80 m (250 ft) in thickness 

(Mapel, 1959) and is the thickest known coal in the United 

States (Glass, 1980). The peat swamp from which it 

originated was narrow and elongate, and lay just west of and 

parallel to the basin-axis trunk stream near Buffalo, Wyo. 

(Obernyer, 1980). It was bordered on the west by coalescing 

alluvial fans originating in the rapidly rising Bighorn uplift 

(fig. 3).

The distribution of the uranium deposits of the 

southern part of the basin is related to the distribution of the 

sandy facies of the Wasatch Formation, because it acted as 

a conduit for oxygenated uranium-bearing ground water 

(Santos, 1981). Seeland (1976) noted that almost all the 

uranium mines in the basin are in an area shown to have a

sediment source in the granite of the Laramie Mountains. 

Because Wasatch coal beds do not have anomalous 

uranium, and Szalay (1958) has pointed out that peat 

adsorbs uranium, Santos (1981) suggested that there was no 

early influx of uranium in solution or in detrital minerals. 

J.S. Leventhal (oral commun., 1989) pointed out that the 

peat-swamp environment has low pH, which would inhibit 

uranium adsorption even if uranium were present in the 

water. Galloway (1979) emphasized the importance of the 

uranium-rich tuff of the White River Group as a uranium 

source. These tuff units unconformably overlie the coarsegrained sandstone whose sand had a Laramie Mountains 

source south of the basin. Water percolating downward 

through the tuffs could have picked up uranium from 

devitrifying glass shards and carried it northward, forming 

uranium deposits in the sandy facies of the Wasatch of the 

southern part of the basin.

H18 Evolution of Sedimentary Basins Powder River Basin
CONCLUSIONS

Paleocurrent study defines two major streams in the 

fluvial rocks of late Paleocene and early Eocene Wasatch 

Formation in the Powder River Basin. The larger was a 

north-flowing basin-axis stream in the westernmost Powder 

River Basin that was also the major longitudinal river of the 

upstream Wind River basin. The other major stream flowed 

northwest from the southeastern Powder River Basin.

Three alluvial depositional systems are defined: (1) a 

distal mud-rich alluvial plain with a source terrane to the 

east in the Black Hills, (2) a proximal sand-rich alluvial 

plain-alluvial fan with a source to the south in the Laramie 

Mountains, and (3) a stream-dominated proximal to distal 

alluvial fan complex with a source to the west in the 

Bighorn Mountains.

Grain-shape and grain-size studies corroborate 

transport directions obtained by the paleocurrent study. In 

the western part of the basin, an area of large tributaries 

flowing into the major basin-axis stream from the Bighorn 

Mountains is indicated by an area of less-regular sand grains 

near Buffalo.

Major coal and uranium deposits are spatially related 

to the Wasatch-time depositional systems of the basin. 

Coal-forming swamps were more abundant in the vicinity of 

the major basin-axis stream. Uranium deposits in the 

Wasatch Formation are found only in the proximal alluvialplain distal-alluvial-fan depositional system of the southern 

basin.

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eds., Recent and ancient nonmarine depositional environments Models for exploration: Society of Economic 

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p. 169-190.

____ 1986, Styles of coal deposition in Tertiary alluvial 

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Flores, R.M., and Ethridge, F.G., 1985, Evolution of intermontane 

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Paleogeography Symposium 3, 1985, p. 107-126.

Galloway, W.E., 1979, Early Tertiary Wyoming intermontane 

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J.H., eds., Depositional and groundwater flow systems in 

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Bureau of Economic Geology, A Research Colloquium, 

p. ix-l-ix-17.

Glass, G.B., 1980, Coal resources of the Powder River coal basin, 

in Glass, G.B., ed., Guidebook to the coal geology of the 

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Wyoming, Public Information Circular 14, p. 97-131.

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elements, Bighorn Mountain region, Wyoming-Montana, in 

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their economic significance: Wyoming Geological 

Association, 23rd Annual Field Conference Guidebook, 

1971, p. 39-47.

Kraus, M.J., 1985, Early Tertiary quartzite conglomerates of the 

Bighorn Basin and their significance for paleogeographic 

reconstruction of northwest Wyoming, in Flores, R.M., and 

Kaplan, S.S., eds., Cenozoic paleogeography of the westcentral United States: Denver, Colo., Society of Economic 

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1985, p. 71-91.

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on sand: American Journal of Science, v. 257, p. 172-190.

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Office, scale 1:500,000, 3 sheets.

Mapel, W.J., 1959, Geology and coal resources of the BuffaloLake DeSmet area, Johnson and Sheridan Counties, 

Wyoming: U.S. Geological Survey Bulletin 1078, 146 p.

Nelson, R.S., 1968, Tertiary deposits and morphology, east flank 

Bighorn Mountains, Wyoming: Earth Science Bulletin, v. 1, 

no. 4, p. 19-24.

Depositional Systems, Wasatch Formation, Powder River Basin, Wyoming H19
Obernyer, S.L., 1978, Basin margin depositional environments of 

the Wasatch Formation in the Buffalo-Lake DeSmet area, 

Johnson County, Wyoming, in Hodgson, H.E., ed., 

Proceedings of the second symposium on the geology of 

Rocky Mountain coal 1977: Colorado Geological Survey, 

Resource Series 4, p. 49-65.

____ 1980, The Lake DeSmet coal seam The product of active 

basin-margin sedimentation and tectonics in the Lake DeSmet area, Johnson County, Wyoming, during Eocene 

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geology of the Powder River Basin, Wyoming: Geological 

Survey of Wyoming, Public Information Circular 14, 

p. 31-70.

Paola, Chris, 1988, Subsidence and gravel transport in alluvial 

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perspectives in basin analysis: New York, Springer-Verlag, 

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Pelletier, B.R., 1958, Pocono paleocurrents in Pennsylvania and 

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Potter, P.E., and Pettijohn, F.J., 1977, Paleocurrents and basin 

analysis [2nd ed.]: Berlin, Springer-Verlag, 425 p.

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Raines, G.L., and Santos, E.S., 1980 [1981], Maps showing 

lithofacies and limonite distribution of the Wasatch 

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Geological Survey Miscellaneous Investigations Series Map 

1-1246, scale 1:250,000, 2 sheets.

Reiche, Parry, 1938, An analysis of cross-lamination the 

Coconino Sandstone: Journal of Geology, v. 46, no. 7, 

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Santos, E.S., 1981, Facies distribution in uranium host rocks of the 

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Survey Open-File Report 81-741, 15 p.

Sawyer, M.B., 1977, Image analysis as a method for determining 

grain-size distributions in sandstones: U.S. Geological 

Survey Open-File Report 77-280, 13 p.

Seeland, D.A., 1976, Relationships between early Tertiary 

sedimentation patterns and uranium mineralization in the 

Powder River Basin: Wyoming Geological Association, 

28th Annual Field Conference Guidebook, p. 221-230.

____ 1978a, Eocene fluvial drainage patterns and their 

implications for uranium and hydrocarbon exploration in 

the Wind River basin, Wyoming: U.S. Geological Survey 

Bulletin 1446, 21 p.

____ 1978b, Sedimentology and stratigraphy of the Lower 

Eocene Wind River Formation, central Wyoming: 

Wyoming Geological Association, 30th Annual Field 

Conference Guidebook, p. 53-64.

____ 1988, Laramide paleogeographic evolution of the eastern 

Powder River Basin, Wyoming and Montana: Wyoming 

Geological Association, 39th Annual Field Conference 

Guidebook, p. 29-34.

Seeland, D.A., Flores, R.M., Johnson, E.A., and Pierce, F.W., 

1988, Some paleogeographic inferences from the paleocurrents of the Tongue River Member, Fort Union 

Formation, Powder River, Bull Mountains, and 

southwestern Williston basins, Montana, in Flores, R.M., 

ed., An integrated view of the depositional systems of the 

Paleocene coal-bearing rocks in the Powder River Basin, 

Wyoming and Montana: Colorado School of Mines, 

Professional Contributions 12, p. 191-194.

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Mountains, Wyoming: Journal of Geology, v. 56, p. 1-15.

Sharp, W.N., and Gibbons, A.B., 1964, Geology and uranium 

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Wyoming: U.S. Geological Survey Bulletin 1147-D, 60 p.

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enrichment of uranium: Second United Nations 

International Conference on the Peaceful Uses of Atomic 

Energy, v. 2, p. 182-186.

Toomey, W.J., 1977, a stratigraphic analysis of the Wasatch 

Formation, western Powder River Basin, Wyoming: 

Dayton, Ohio, Wright State University, unpub. M.S. thesis, 

56 p.

Warwick, P.D., 1985, Depositional environments and petrology of 

the Felix coal interval (Eocene), Powder River Basin, 

Wyoming: Lexington, University of Kentucky, Ph.D. 

dissertation, 333 p.

Warwick, P.D., and Flores, R.M., 1987, Evolution of fluvial styles 

in the Eocene Wasatch Formation, Powder River Basin, 

Wyoming, in Ethridge, F.G., Flores, R.M., and Harvey, 

M.D., eds., Recent developments in fluvial sedimentology: 

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Special Publication 39, p. 303-310.

H20 Evolution of Sedimentary Basins Powder River Basin

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Oil and Gas Investigations Charts show stratigraphic information for certain oil and gas fields and other areas having petroleum potential.

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology in relation to specific mining or mineral-deposit problems; post-1971 maps 

are primarily black-and-white maps on various subjects such as environmental studies or wilderness mineral investigations.

Hydrologic Investigations Atlases are multicolored or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; the principal 

scale is 1:24,000, and regional studies are at 1:250,000 scale or smaller.

Catalogs

Permanent catalogs, as well as some others, giving comprehensive 

listings of U.S. Geological Survey publications are available under the 

conditions indicated below from the U.S. Geological Survey, Books and 

Open-File Reports Sales, Box 25286, Denver, CO 80225. (See latest 

Price and Availability List.)

"Publications of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a set 

microfiche.

"Publications of the Geological Survey, 1962-1970** may be purchased by mail and over the counter in paperback book form and as a set 

of microfiche.

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

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

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

Supplements for 1982, 1983, 1984, 1985, 1986, and for subsequent years since the last permanent catalog may be purchased by mail 

and over the counter in paperback book form.

State catalogs, "List of U.S. Geological Survey Geologic and Water-Supply Reports and Maps For (State)," may be purchased by mail and 

over the counter in paperback booklet form only.

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

form only.

Selected copies of a monthly catalog "New Publications of the 

U.S. Geological Survey" is available free of charge by mail or may be 

obtained over the counter in paperback booklet form only. Those wishing 

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

Geological Survey" should write to the U.S. Geological Survey, 582 National Center, Reston, VA 22092.

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

announcements, and publications may be incorrect Therefore, the prices 

charged may differ from the prices in catalogs, announcements, and publications.