Evidence for a shallow early or middle Wisconsin-age lake in the Bonneville Basin, Utah

QUATERNARY

RESEARCH

21, 248-262 (1987)

Evidence for a Shallow Early or Middle Wisconsin-Age Lake in the Bonneville Basin, Utah CHARLES G. OVIATT,* WILLIAM D. McCOY,~ ANDRICHARD G. REIDERS *Department Geography,

of Geology, Kansas State University of Massachusetts, University

University, Amherst, of Wyoming,

Manhattan, Kansas 66506; TDepartment Massachusetts 01003; and #Department Laramie, Wyoming 82071

of Geology and of Geography,

Received April 30, 1986 Relatively complete stratigraphic records of the Bonneville cycle and of at least one and probably two earlier lacustrine cycles are exposed along the Bear River below Cutler Dam in northern Utah between altitudes of 1290 and 1365 m. In most exposures the unconformity between the Bonneville Alloformation and the underlying unit, herein named the Cutler Dam Alloformation, is marked by slight erosional relief and by a weakly to moderately developed buried soil, herein named the Fielding Geosol. In truncated profiles, the Fielding Geosol reaches a maximum of stage II carbonate morphology. Wood from near the base of the Cutler Dam Alloformation yielded a i4C date of >36,000 yr BP. (Beta-9845). Alloisoleucineiisoleucine (aIle/Ile) ratios of Sphaerium shells from the Cutler Dam beds average 0.15 2 0.01 in the total hydrolysate, which is significantly greater than the average for Sphaerium shells of Bonneville age elsewhere in the basin. Therefore, the Cutler Dam Alloformation is older than 36,000 yr BP., but much younger than deposits of the Little Valley lake cycle (140,000 yr B.P.?) which bear shells having significantly higher aIle/Ile ratios. The Cutler Dam Alloformation along the Bear River may be broadly correlative with marine oxygen-isotope stages 4 or 3. Fine-grained, fossiliferous, marginal-lacustrine facies of the Cutler Dam Alloformation are exposed at altitudes near 1340 m, and are probably the highest exposures of sediments deposited in the early or middle Wisconsin lake in the Bonneville basin. D 1987 university of Washington

INTRODUCTION

Interpretations of Lake Bonneville history have changed dramatically in recent years (Scott et al., 1983; Currey et al., 1984; Spencer et al., 1984) as new exposures and new approaches to stratigraphic analysis have yielded fresh ideas. Specifically, Lake Bonneville is now interpreted as having undergone only one major transgression and regression during late Wisconsin time.’ The timing of Lake Bonneville and the documentation of oscillations within it have been refined. The Alpine Formation (Hunt et al., 1953; Morrison, i In this paper, the term Lake Bonneville refers specifically to the last major deep lake cycle, which occurred between about 30,000 and 10,000 yr B.P. (Currey et al., 1983, p. 63; Scott et al., 1983; Currey and Oviatt, 1985). Therefore, the term pre-Bonneville refers to lake cycles and deposits older than about 30,000 yr B.P.

1966), which for many years was regarded as the deposit of a deep lake of early to middle Wisconsin age, has been reinterpreted and deposits formerly assigned to the Alpine Formation are now regarded as either Illinoian or late Wisconsin in age (Morrison, 1975; Scott et al., 1983; Oviatt, in press). Scott et al. (1983, Fig. 2) suggested that in the interval from about 130,000 to 25,000 yr BP all lake fluctuations in the Bonneville basin were restricted to altitudes below about 1380 m, but they reported no deposits of lakes known to have existed during this time interval. Above 1380 m, the strongly developed Promontory Geosol* is directly overlain by deposits of Lake Bonneville with no deposits of intermediate-aged lakes in be2 In this paper we regard the Dimple Dell Geosol (Morrison, 1965a) and the Promontory Geosol (Morrison, 1965b) as equivalent (Scott et al., 1983). 248

0033-5894/87 $3.00 Copyright 0 1987 by the University of Washington. All rights of reproduction in any form reserved.

BONNEVILLE

BASIN

tween. In this paper, we report stratigraphic, amino acid, and soils evidencefor a shallow, early or middle Wisconsin lake in the Bonneville basin, and propose some new formal stratigraphic names for use in this area. LATE QUATERNARY STRATIGRAPHY OF THE LOWER BEAR RIVER AREA

Quaternary lacustrine deposits of Lake Bonneville and of at least one, and probably two, pre-Bonneville lake cycles are exposedalong the lower Bear River below Cutler Dam in northern Utah (Fig. 1; Oviatt et al., 1985;Oviatt, 1986a,1986b).In this area, the Bonneville Alloformation, as defined by Currey et al. (1984), and older Quaternary deposits underlie a broad la-

LAKE

HISTORY

249

custrine and alluvial plain, into which the Bear River is entrenched25 to 70 m. Cutbanks, slump scarps, and irrigation-canal cuts provide widely spacedbut numerous exposuresin the Quaternary lacustrine deposits between altitudes of 1290 and 1365m. In the lower Bear River area we have identified deposits of a pre-Bonneville lake cycle and a buried soil that are intermediate in age between the Little Valley lake cycle, as defined by Scott et al. (1983),and Lake Bonneville. We proposein this paper the names Cutler Dam Alloformation and Fielding Geosolfor these newly recognized stratigraphic units.3 The general stratigraphic relationships between all these units are summarizedin Figure 2. Cutler Dam Alloformation

The pre-Bonneville lacustrine deposits that underlie the Bonneville Alloformation in stratigraphic sections 1, 2, 5, 6, and 7 (Fig. 3) are formally named in this paper the Cutler Dam Alloformation (Table 1). The Cutler Dam Alloformation is interpreted as having been deposited during a newly recognized late Pleistocene lake cycle referredto in this paperas the Cutler Dam cycle. In all measuredsections (Fig. 3) the Cutler Dam Alloformation is separated from the overlying Bonneville Alloformation by a buried soil, here named the Fielding Geosol (Table 2). The base of the Cutler Dam Alloformation, where it overlies structurally deformed upper Ter-

FIG. 1. Location map. P = Provo Shoreline and B = Bonneville Shoreline of Lake Bonneville for reference; CD = approximate upper limit of the Cutler Dam lake.

3 The terms alloformation and geosol are defined in the 1983 North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature (NACSN), 1983). An alloformation is the fundamental stratigraphic unit used in allostratigraphic classification (NACSN, 1983, p. 866). “An allostratigraphic unit is a mappable stratiform body of sedimentary rock that is defined and identified on the basis of its bounding discontinuities” (NACSN. 1983, p. 865). A geosol is the fundamental pedostratigraphic unit (NACSN, 1983, p. 864). “A pedostratigraphic unit is a buried, traceable, three-dimensional body of rock that consists of one or more differentiated pedologic horizons” (NACSN, 1983, p. 864).

250

CHARLES

G. OVIATT

ET AL.

tion of the exposed section relative to the position of the axis of the paleovalley that was filled by the Cutler Dam deposits. From the available map evidence (Oviatt, 1986a, 1986b), the entrenched paleovalley that existed prior to the deposition of the Cutler Dam Alloformation was very close to the modern entrenched Bear River Valley. Deposits of the Cutler Dam Alloformation are correlated between exposures on the basis of lithologic similarity, similar relative stratigraphic position below the Bonneville Alloformation, degree of develFIG. 2. Schematic diagram showing inferred stratiopment of buried soil profiles, and radiographic relationships of alloformations and geosols in carbon and amino acid analyses. Although the Bonneville basin as interpreted in this paper. P = homotaxial errors are possible from the Promontory Geosol; F = Fielding Geosol; LV = Little Valley Alloformation; CD = Cutler Dam Allomiscorrelation of deposits that occur in formation; B = Bonneville Alloformation; (B) = similar sequences at different locations, Bonneville Shoreline; (GSL) = Great Salt Lake. they are considered unlikely in the context of the currently available evidence. Deposits of the Cutler Dam Alloformatiary basin-fill rocks, is exposed at only a few localities. The Cutler Dam Alloformation are grouped into two general facies, a tion ranges in thickness from several lacustrine facies and a marginal lacustrine meters to over 25 m depending on the loca- facies (Fig. 3). Lithology and fossil content EXPLANATION 1370 t

6

,?

1360

B LV

t

F

-co Id ‘3

F-

Fielding

p -

Promontory

Bonneville Little klloy

X

Geosd

Atlotormation Albkmdit

CDI

Cutler

Dam Atlotormation law&ins lacier

CDm

Cutler

Dam Allotormation marginal locustrine

colluvium

CO

Geosol

la*r

covered

q

lacustrino mud with thin sand intwkds

0

lacustrirw

Q

bartrir*

grad

q

Tertiary

bedrock

sand

and silt

1340 - Cl.2 5 * 3

1330 -

g

amino acid samples

Beta-96L5

radiocarbon

OS

F

.l

AGL-266

1320 -

ostrocode

IT&to

samples

LI

(see text1

samptes Isee and Table 31

text

COI

1290 -

tl approximate

horizontal

scale

Bear River

floodplain

= RotaF 9.483 2 OS IX1

FIG. 3. Measured stratigraphic sections along the Bear River. Refer to Figure 1 for locations. In all sections the Bonneville Alloformation consists of finely bedded calcareous silt and minor sand and gravel. At section 6 the Bonneville Alloformation contains a large proportion of volcanic ash reworked from the Tertiary bedrock.

BONNEVILLE TABLE

BASIN LAKE

HISTORY

251

1. DEFINITION OF THE CUTLER DAM ALLOFORMATION

1. Holostratotype locality: Areal holostratotype includes sections 1, 2, 5, 6, and 7 shown on Figures 1 and 3, name derived from Cutler Dam on the Bear River, 2 km upstream from section 7. Section 1 Slump scarp on left bank of Bear River, 0.1 km north of Utah Highway 102, lat. 41”42’55” N. long. 112’6’28” W, Honeyville, Utah, 7.5’ quadrangle. Section 2 Slump scarp on left bank of Bear River, 0.2 km south of Utah Highway 154, lat. 41”46’54” N, long. 112’6’18” W, Cutler Dam, Utah, 7.5’ quadrangle. Section 5 Exposure in cut of West Side Canal, 0.1 km west of an abandoned canal bridge, lat. 41”48’36” N , long. 112”4’54” W, Cutler Dam, Utah, 7.5’ quadrangle. Section 6 Exposure in excavation for siphon along Hammond Main Canal in 1984, Bear River bluffs on west side of mouth of Willow Creek, lat. 41”48’57” N, long. 112”4’21” W, Cutler Dam, Utah, 7.5’ quadrangle. Section 7 Exposure in cut of West Side Canal, 0.1 km east of canal bridge on north side of Bear River. lat. 41”49’30” N, long. 112”4’36” W, Cutler Dam, Utah, 7.5’ quadrangle. 2. Definition: Lacustrine and marginal-lacustrine mud and sand; unoxidized sediment is light to dark gray; oxidized sediment is yellowish brown (IOYR-7SYR hue); distinguished from Bonneville Alloformation, which overlies it in all exposures, by presence of Fielding Geosol; Bonneville Alloformation also contains more finely bedded carbonate-rich silt and locally volcanic ash reworked from Tertiary deposits. Amino acid ratios of mollusks collected from the Cutler Dam Alloformation are summarized in Table 4. 3. Bounding discontinuities: Lower boundary exposed in sections 5 and 7 consists of angular unconformity with underlying upper Tertiary lacustrine deposits; upper boundary in all exposures marked by Fielding Geosol overlain by Bonneville Alloformation. 4. Age: As discussed in text probably between 80,000 and 40,000 yr B.P. (during the interval represented by early or middle Wisconsin time or marine oxygen-isotope stages 4 or 3).

are the primary criteria used in making the distinction. These facies are discussed below. In sections 1, 2, and 6, the lacustrine facies of the Cutler Dam Alloformation consists in part of finely bedded muds and interbedded fine to medium sand, which grade upward into thicker sand beds interbedded with thin layers of mud, which in turn grade upward into sandy silt or sand at the top of the sequence. Where the groundwater table is high, Cutler Dam lacustrine mud is light gray to dark gray from organic matter and compounds of reduced iron. TABLE

Ripple laminations in the interbedded sand, and small sand lenses (
2. DEFINITION OF FIELDING GEOSOL

~1. Holostratotype locality: Area1 holostratotype includes profiles at sections 1, 2, 5, 6, and 7 (see locations in Table 1); name derived from town of Fielding, Utah. 2. Definition: Traceable buried soil formed in lacustrine and marginal lacustrine deposits of the Cutler Dam Alloformation; profiles are usually truncated, but where most complete, consist of weak to moderate A-Bk horizon development; calcic horizon development reaches a maximum of stage II morphology; see Appendix 1 for a detailed description of a profile of the Fielding Geosol. 3. Boundaries: Lower boundary is the base of the lowest soil horizon developed in the Cutler Dam Alloformation; upper boundary is the disconformity between the Cutler Dam Alloformation or younger colluvial deposits and the overlying Bonneville Alloformation. 4. Age: Developed during interval between about 40,000 yr B.P. (or earlier) and 25,000 yr B.P.; soil formation terminated by transgression of Lake Bonneville.

252

CHARLES

G. OVIATT

ward into slightly oxidized sand (lOYR7.5YR hue). This sequence of coarse-finecoarse sedimentation probably represents the transgressive, open-water, and regressive phases of the Cutler Dam cycle. The upward coarsening of the sediments above the mud layers in sections 1 and 2 is also interpreted as representing the regressive phase of the Cutler Dam cycle. A bounding discontinuity was not exposed at the base of section 6, but the sequence was more completely exposed than in sections 1 and 2. At sections 1 and 2, and at similar sites in this area, the base of the Cutler Dam Alloformation is not exposed probably because of slumping, which is caused by a high rate of ground water discharge from the transgressive-phase sand near the base of the alloformation. Two samples of Cutler Dam lacustrine mud from section 1 contained the smooth form of the ostracode species Limnocythere staplini, which lives in shallow saline-lake waters in the Great Basin where Na+, Mg2+, and SOd2- are the dominant ions (R. M. Forester, written communication, 1984). L. staplini is not present in samples taken from cores of Lake Bonneville sediments deposited while the lake stood at levels above an altitude of about 1370 m (Spencer et al., 1984). The ostracodes from section 1 were collected from TABLE3. Stratigraphic unit

the finely bedded organic-rich mud, and there are no sediments in this exposure of the Cutler Dam Alloformation that based on their lithology could have been deposited in deeper water. Therefore, based on the available ostracode data, the Cutler Dam lake was saline at its deepest stages and attained altitudes probably no higher than about 1370 m. Spruce needles (Picea sp.) and the bones of a large trout (Salmo sp.; Table 3) were also collected from a small sand lens in the lacustrine facies of the Culter Dam Alloformation at section 1. They probably were swept into the saline lake water by streams and were carried to the depositional site by bottom currents. In measured sections 5 and 7 (Figs. 1 and 3), and in other exposures along the West Side Canal in the vicinity of these sections, the Bonneville Alloformation disconformably overlies colluvium and fine-grained sediments interpreted as marginal-lacustrine or marsh facies of the Cutler Dam Alloformation. Here the Cutler Dam Alloformation consists of finely bedded silt, clay, and fine sand filling small buried valleys cut in the Tertiary bedrock. The bedding in these sediments is more irregular than in the lacustrine facies, and rippled sand beds are not present. Some beds contain small amounts of organic matter and abundant

QUATERNARYFOSSILSCOLLECTEDINTHECUTLERDAMAREA~ Ostracodes

Vertebrates

Bonneville Alloformation

Typical “Bonneville” assemblage*

Mammuthus

Cutler Dam Alloformation (lacustrine)

Limnocythere staplini

Salmo

Cutler Dam Alloformation (marginal lacustrine)

ET AL.

Plants

Mollusks

Wood Algae

Sphaerium Lymnaea Amnicola Fluminicola

Wood

Sphaerium Fluminicola

Picea

needles Gila atraria Cygnus buccinator

Large mammal bones

Lymnaea Helisoma Valvata

0 Identified by B. J. Albee, A. J. Feduccia, R. M. Forester, J. H. Madsen, Jr., and G. R. Smith. * See Spencer et al. (1984) for a description of the ostracode fauna of the Bonneville Alloformation.

BONNEVILLE

BASIN LAKE

HISTORY

257

gastropod shells, an association that is probably correlative with deposits of the Little Valley cycle (about 140,000 yr B.P.; common in shallow lacustrine or marsh sediments, and suggests that the gasScott et al., 1983). tropods are not reworked. Vertebrate fossils from these sediments include bones Fielding Geosol of a trumpeter swan (Cygnus buccinator; Truncated soil profiles are present bein all Feduccia and Oviatt, 1986), fragments of neath the Bonneville Alloformation unidentifiable large mammal bones, and measured sections. In most sections, only bones of Utah chub (Gila aft-aria; Table 3). part of a Bk horizon is preserved (ApThe fine texture, the irregular bedding, pendix l), but at section 4 part of an argillic the occurrence of abundant gastropods in (Bt) horizon is also preserved (Appendix organic-rich layers, and the geomorphic 2). The buried soil profiles in sections 1, 2, setting of the depositional sites suggest a 5, 6, and 7 (Fig. 3) are interpreted as exposhallow, quiet, and fresh-water deposisures of a single laterally continuous tional environment for the Cutler Dam Al- geosol, named in this paper the Fielding loformation in sections 5 and 7. As interGeosol (Table 2). The buried soil profile in preted here, the small buried valleys at section 4, however, is considerably better these sites were connected to the main developed, and may be correlative with the river valley and were flooded during the Promontory Geosol of Morrison (1965b; high stand of the Cutler Dam lake. The see footnote 2). main river valley and its small tributary A typical profile of the Fielding Geosol is valleys would have been a fresh- or exposed in section 1 (Fig. 3; Appendix 11, brackish-water estuary at the margin of the and is formed in carbonate-rich sand, silt, saline lake. The presence of in situ gas- and clay of the lacustrine facies of the tropods indicates a direct hydrologic con- Cutler Dam Alloformation. At this locality, nection between the small valleys and the the profile consists of a Bk horizon having fresh river water in the estuary. Although a maximum development of carbonate the Utah chub also lived in fresh water, its morphologic stage II (after Gile et ul., bones could have been transported to the 1966; Machette, 1985). The upper part of depositional site. the profile at section 1 is mottled and If these interpretations are correct, the slightly gleyed possibly due to a fluctuating marginal lacustrine sediments exposed in water table prior to the truncation of the sections 5 and 7 define the upper altitudinal profile and inundation by Lake Bonnelimit of the Cutler Dam lake at about 1340 ville. Reider (1985) has noted similar motm. The Cutler Dam Alloformation has not tling and gleying caused by water-level been found in the many good exposures fluctuations of a modern reservoir in Wyohigher than 1340 m in this area. ming. At section 4, fine-grained sediments of The Fielding Geosol is similar to the the Bonneville Alloformation rest on a post-Bonneville soils in the area. All expoburied soil developed in fine-grained lacus- sures of the Fielding Geosol have Bk hotrine deposits and lacustrine gravel. Fore- rizons with stage I to stage II carbonate set bedding in the gravel, and the litholmorphology which is similar to the postogies of the clasts, which have source areas Bonneville soils. The Fielding Geosol at to the south, indicate longshore transport section 6 consists of a thin discontinuous A of the gravel toward the north and deposihorizon overlying a stage I to stage II calcic tion in a gravel spit. Soil development in (Bk) horizon, and it is possible that the the gravel, as discussed below, suggests Fielding Geosol had A-Bk or A-Bw-Bk that the gravel may be considerably older horizonation at other sites prior to the trunthan the Cutler Dam Alloformation, and is cation of the A horizon. The modern (post-

254

CHARLES

G.

OVIATT

ET AL.

Bonneville) soils in the area, which are de- be approximately 105,000 yr based on the veloped in similar parent materials, have secondary calcium carbonate content of A-Bw-Bk horizonation. The modem soil the K horizons. The duration of soil formaprofiles lack argillic horizons, and both the tion has not been determined for the profile A and Bw horizons are slightly calcareous. in section 4, but the profile is tenta++ly Calcic soil profiles, which are formed in correlated with the Promontory Ge, ,’ the marginal lacustrine facies of the Cutler based on the carbonate morphology 01 Dam Alloformation in sections 5 and 7, are Bk horizon. If this correlation is car. . truncated and locally overlain by fine- the lacustrine gravel parent material r grained colluvium. The colluvium also this soil is of Little Valley age. If amino bears a weak soil that has an A-Bk profile. acid ratios or other geochronometric data When considered together, the profiles that eventually become available for the gravel, are formed in the marginal lacustrine de- the uncertainty in its age can be narrowed. posits and the colluvium can be regarded as The top of the Little Valley lacustrine a subdivided occurrence (Morrison, 1967) gravels at section 4 (about 1335 m altitude) of the Fielding Geosol. is near the inferred upper altitudinal limit of All exposed buried-soil profiles were the Cutler Dam lake (1340 m altitude). The truncated an unknown amount by waves Cutler Dam lake would not have mainduring the transgressive phase of Lake tained its maximum level for an extended Bonneville. However, it is unlikely that any period of time because it was a closedof the profiles were significantly eroded be- basin lake, and therefore its level fluccause they were located at sites where tuated in response to minor changes in cliwave energies would have been low, either mate. Thus, the lake would have been on very gently sloping surfaces or within shallow at section 4 even at its maximum the narrow entrenched river valley that stages. And if sediment were in short predated Lake Bonneville. Parts of the A supply due to the local geomorphic setting horizons of the buried soils at sections 5, 6, on the crest of the pre-Cutler Dam gravel and 7, for example, are preserved, sug- spit, there may have been insignificant degesting that neither wave nor fluvial ero- position at this site during the Cutler Dam sion at these localities was significant. On cycle. Therefore, some or all of the silty the basis of these arguments, and because clay in the upper 78 cm of this soil profile of a similar degree of soil development (Appendix 2) may be fine-grained lacusamong the profiles at sections 1, 2, 5, 6, trine deposits of the Cutler Dam Alloforand 7, we correlate the buried soils in these mation overlying spit gravel of Little Valley sections and interpret them as the Fielding age. If this is the case, the Fielding and Geosol. Similar amino acid ratios of the Promontory Geosols are combined into a Cutler Dam deposits in sections 5 and 6 composite soil profile at this section. support the correlation of soils in these two GEOCHRONOLOGY sections. The buried soil at section 4 is better deThe age of the Cutler Dam Alloformation veloped than the Fielding Geosol. The Bk is bracketed by several lines of evidence, horizon of the buried soil in section 4 (Ap- including radiocarbon dates, amino acid pendix 2) reaches stage III carbonate mor- analyses, and estimates of soil developphology, and this, plus the overall mor- ment. The evidence indicates that the phology of the profile, is similar to the Cutler Dam Alloformation was probably Promontory Geosol (Morrison, 1965b; deposited during early or middle Wisconsin Scott et al., 1983; see footnote 2). Scott et time and that it is broadly correlative with al. (1983, Table 5) estimate the duration of marine oxygen-isotope stages 4 or 3. soil formation of the Promontory Geosol to Two limiting radiocarbon dates have

BONNEVILLE TABLE

255

HISTORY

4. AMINOACID ANALYSES OFMOLLUSKSFROMMEASURED SECTIONS IN THECUTLERDAM AREAS

Stratigraphic unit B

BASIN LAKE

:idville ..keville heville

“I+Veville C. ler Dam lackstrine facies Cutler Dam marginal lacustrine facies Cutler Dam marginal lacustrine facies Cutler Dam marginal lacustrine facies Cutler Dam marginal lacustrine facies

Measured section

Lab number

6 6 3 3

AGL-298 AGL-297 AGL-271 AGL-272

6

AGL-295

Sphaerium

5

AGL-268

Helisomu

5

AGL-269

Vulvuta

5

AGL-270

Lymnueu

5

AGL-274

Lymnaea

Alloisoleucine/isoleucine

Genus @lb

Free

Amnicolu

(3)

Sphaerium (1) Lymnnea Amnicola

(1) (2)

0.19 0.19 0.10

t

0.01

0.14

Hydrolysate

0.105 t 0.005 0.11 0.06 0.097 2 0.004

0.21 ” 0.03

0.15 i 0.01

0.18 ? 0.02

0.11 i 0.01

0.18 2 0.01

0.14 t 0.01

(2)

0.16 IL 0.03

0.12 i 0.01

? (3)

0.20 2 0.03

0.14 -+ 0.01 -. at the University

(3)

(3)

(3)

a All samples were analyzed by W. D. McCoy at the Amino Acid Geochronology Laboratory of Massachusetts. b Number of separate analyses of independent preparations of subsamples of a single collection.

been obtained on the Cutler Dam Alloformation. A radiocarbon date was obtained for wood from coarse sand near the base of section 6. The date of >36,000 yr B.P. (Beta-9845) accords with the amino acid data from this section and provides a reliable minimum limiting date for the Cutler Dam Alloformation. A sample of organicrich lacustrine mud collected 10.4 m below the top of the Fielding Geosol at section 1 yielded a radiocarbon date of 28,180 t 1120 yr B.P. (Beta-9483). Although reported as a finite date, this sample may have been contaminated with “young” carbon, possibly from undetected decomposed root hairs or from bacteria colonizing the organic-rich mud on the outcrop. The results of amino acid analyses of mollusk shells in the lower Bear River area indicate an age for the Cutler Dam Alloformation that is intermediate between the Bonneville and Little Valley Alloformations (Tables 4 and 5). The mean alloisoleucine/isoleucine (aIle/Ile) ratio in the total hydrolysate of Sphaerium shells from the

Cutler Dam lacustrine facies is significantly greater than the aIle/Ile ratio of Sphaerium from the Bonneville Alloformation at section 6 (Table 4).4 The mean aIle/Ile ratios in both the free fraction and the total hydrolysate of Lymnaea from the Cutler Dam Alloformation are also significantly greater than those of Lymnaea collected from the Bonneville Alloformation at section 3. These observations conform to the stratigraphy as shown in Figure 3. More important in terms of the geochronologic evidence that the amino acid analyses provide is the fact that the aIle/Ile ratios of Lymnaea from the Cutler Dam Alloformation are much lower than those from the Little Valley Alloformation (Table 5). It must be noted that the ratios given in 4 Two Sphaerium shells in sample AGL-297 from measured section 6 had anomalously high aIle/Ile

ratios (0.25 and 0.28 in the free fraction and 0.19 in the total hydrolysate) and are interpreted as being reworked from older deposits. The age of a unit is assumed to be the age of the youngest shells that it contains.

256 TABLE

CHARLES 5. SUMMARY

TABLE

(marginal

Little Valley Alloformation

(averagep

McCoy

0.11 Dam

area)

(1981)

0.12

0.06

lacustrine)

I

0.01

0.11

-

and this

HYDROLYSATE

Sphuerium

2 0.03

(lacustrine)

Cutler Dam Alloformation

a From

Lymnaea

(average)” (Cutler

ET AL.

OF AVERAGE aIle/lle RATIOS IN THE TOTAL DEPOSITS IN THE BONNEVILLE BASIN

Stratigraphic unit Bonneville Alloformation Bonneville Alloformation Cutler Dam Alloformation

G, OVIATT

0.15

OF SHELLS

FROM

Amnicola

0.15

”

0.03

0.10

f

0.005

+ 0.01

-

0.13

*

0.01

-

0.21

2 0.03

-

0.32

-+ 0.03

paper.

Table 4 are not directly comparable with the ratios for the Bonneville and Little Valley Alloformations given in Table 5. There have been small, but significant differences in the preparation procedure for these shell samples. The new procedure by which the samples from the Cutler Dam area were prepared produces more consistent aIle/Ile ratios. The old procedure produced Bonneville-age aIle/Ile ratios in the total hydrolysate that were up to 50% higher and Little Valley age ratios that were up to 25% higher than samples prepared under the new procedure (McCoy, 1987; Miller et al. (1982) provide an explanation of the effects of preparation differences). Despite these uncertainties, it can be seen that the aIle/Ile ratios of the Lymnaea from the Cutler Dam Alloformation clearly indicate an age for those deposits that is significantly younger than that of the Little Valley Alloformation. The buried soil in the Cutler Dam Alloformation provides an additional, though less precise, means of estimating the age of the parent materials. The Fielding Geosol, with stage I to stage II carbonate morphology, is similar in degree of development to the post-Bonneville soils in this area. Therefore, it may have formed in less than 15,000 + 5000 yr, assuming the geosol is not significantly truncated. Lake Bonneville had transgressed to an altitude of 1340

m by about 25,000 yr B.P. (Scott et al., 1983; Currey and Oviatt, 1985), and formation of the Fielding Geosol would have ceased by that time because it was submerged below the lake. Therefore, the Cutler Dam lacustrine and marginal lacustrine deposits, in which the Fielding Geosol formed, could be as young as 40,000 yr BP If, despite the reasoning outlined above, the Fielding Geosol was significantly eroded, the Cutler Dam Alloformation could be older. McCalpin (1986) has identified lacustrine deposits in Hansel Valley, about 50 km west of the lower Bear River Valley, which are intermediate in age between the Bonneville Alloformation and the Little Valley Alloformation. The deposits are exposed in a gully at an altitude close to 1340 m. Two thermoluminescence (TL) dates of the Hansel Valley deposits are approximately 76,000 and 82,000 yr B.P. (McCalpin, 1986; McCalpin et al., in press). If the Hansel Valley deposits are equivalent to the Cutler Dam Alloformation, and if the TL dates are accurate, the Cutler Dam Alloformation may be older than 60,000 yr B.P. However, the accuracy of TL dates on lacustrine sediments is not yet well established, and it is difficult to correlate deposits in exposures 50 km apart in different valleys. TL dates for the Cutler Dam Alloformation in its type area, or

BONNEVILLE

BASIN

amino acid data from Hansel Valley, would be helpful in correlations, but these have not yet been obtained. Until other data become available, we prefer a possible stratigraphic correlation between the Hansel Valley deposits and the Cutler Dam Alloformation, but we avoid stating with certainty that they are the same unit. In conclusion, our estimate of the age of the Cutler Dam Alloformation is as follows. The >36,000 yr B.P. 14C date and soil development indicate that the Cutler Dam Alloformation is at least 40,000 yr old, and amino acid data suggest that it is significantly younger than the Little Valley Alloformation (Illinoian; 140,000? yr B .P. ; Scott et al., 1983). Therefore, the Cutler Dam Alloformation is most likely early or middle Wisconsin in age. The TL dates from Hansel Valley (McCalpin, 1986) suggest an early Wisconsin age. DISCUSSION This paper reports evidence for two new stratigraphic units in the Bonneville basin,

6

LAKE

251

HISTORY

the Cutler Dam Alloformation and the Fielding Geosol, which occur between the deep-lake deposits of the Bonneville and Little Valley Alloformations. With a probable age between 40,000 and 80,000 yr B.P.. the Cutler Dam Alloformation was deposited in a lake of early or middle Wisconsin age, or broadly correlative with marine oxygen-isotope stages 4 or 3 (Fig. 4). As pointed out by Scott et al. (1983, pp. 280-281), the Bonneville cycle occurred during the later part of oxygen-isotope stage 2. They used that relationship, in addition to other data, to suggest that the Little Valley cycle, for which precise dating control is not available, similarly occurred during the later part of oxygen-isotope stage 6 (Fig. 4). If similar reasoning is applied to the Cutler Dam cycle, its age could be inferred as approximately 65,000 yr B.P., i.e., during the later part of oxygenisotope stage 4 (Fig. 4). This inference is reasonable in the context of paleohydrologic and paleoclimatic considerations presented below.

5

-1.0

-1.5

-\ ,-2.0

100

50

0

lo3 yr BP. FIG. 4. Diagram showing possible correlations between the Bonneville, Cutler Dam, and Little Valley lake cycles and the marine oxygen-isotope record. Oxygen-isotope data from core V28-238 (Shackleton and Opdyke, 1973) as plotted by Imbrie and Imbrie (1980, Fig. 7); age of Little Valley lake from Scott et al. (1983); lake surface areas derived from area-altitude relationship for Lake Bonneville (Currey and Oviatt, 1985, Fig. 3). B = Lake Bonneville; CD = Cutler Dam lake; LV = Little Valley lake; o indicates overflow at the Bonneville and Provo levels of Lake Bonneville.

-ds 0 (1D &

258

CHARLES

G. OVIATT

ET AL.

The Little Valley, Cutler Dam, and Bonneville lakes can be compared hydrologically using their maximum surface area, which serves as a proxy for evaporative output from the lakes. At its maximum (overflowing) stage, Lake Bonneville had a surface area of 5 1,000 km*, and received water from a number of major streams, including the Bear River. Using a surface area-altitude curve for Lake Bonneville (Currey and Oviatt, 1985, Fig. 3), and assuming that the shape of the curve has not changed significantly during the last 150,000 yr, the Little Valley lake and the Cutler Dam lake had surface areas of approximately 44,000 and 22,000 km*, respectively (Fig. 4). Because the Bear River was not permanently diverted into the Bonneville basin until late Pleistocene time, probably about 30,000 yr B.P. (Bright, 1963; McCoy, 1981), possibly neither the Little Valley nor the Cutler Dam lake received input from this source. Modern Bear River discharge near the late Pleistocene diversion point (Oneida, Idaho) is about 20% of the total inflow to Great Salt Lake (Table 6). The Bear River supplied less than 20%, but still a significant proportion of the total inflow to Lake Bonneville allowing it to attain the greatest surface area, and highest level, of any Pleisto-

cene lake in this basin (Currey et uf., 1983, p, 63). Lake Bonneville is the only late Pleistocene lake known to have overflowed. Although glaciers and lakes are not strictly comparable hydrologic systems, there is some suggestion that late Pleistocene glacier fluctuations and lake cycles in the Bonneville basin were similar in magnitude, if the effects of the Bear River diversion are considered (Fig. 4). In making this comparison we assume that the variation in al80 in carbonate deep-sea sediments provides a global record of the changes in volume of glacier ice during the late Pleistocene (Shackleton and Opdyke, 1973). Lake Bonneville was associated with a major glaciation (late Wisconsin; stage 2) and had the added input of the Bear River. The Little Valley lake was associated with more extensive glaciation (Illinoian; stage 6), but lacked the significant input of Bear River water. Early to middle Wisconsin (stages 4 and 3) glaciation was less extensive than either the Illinoian or the late Wisconsin (Fig. 4), and the Cutler Dam lake probably lacked input from the Bear River. The Cutler Dam lake was, therefore, correspondingly small. This conclusion is consistent with what is presently known about the extent of early Wisconsin glaciers relative to Illinoian and late Wisconsin glaciers in the TABLE 6. MODERN MEAN ANNUAL BEAR RIVER DISCHARGE AND GREAT SALT LAKE INFLOW DATA~ Rocky Mountains (Pierce et al., 1976) and in midwestern and eastern North America Bear River discharge at Oneidab.. . . . . . 700 million m3 Bear River discharge at Corinnec.. . . . .I400 million m3 (Clark and Lea, 1986). In both regions Surface inflow to Great Salt Lake.. . . . .23OO million m3 early Wisconsin glaciers were less extenTotal inflow to Great Salt Lake . . . . . . . . 3600 million m3 sive than either Illinoian or late Wisconsin glaciers. Bear River discharge at Oneida is: 50% of total discharge at Corinne 30% of surface inflow to Great Salt Lake 20% of total inflow to Great Salt Lake 0 Data from USGS Water-Supply Paper 2127 (1974) and Amow (1984). b Oneida, Idaho, gaging station is close to the late Pleistocene diversion point of the Bear River (Bright, 1963). c Corinne, Utah, is close to the mouth of the Bear River. Discharge at this point includes water from streams in Cache Valley and the Malad River.

APPENDIX

1

Description of Fielding Geosol at Section 1 (See Table Al)

Location: Section 1 Parent material: Sand and silt of the Cutler Dam Alloformation Additional notes: Soil buried by about 6 m of silt, sand, and gravel of the

BONNEVILLE TABLE

Al.

BASIN

LAKE

LABORATORY DATA FOR FIELDING GEOSOL AT SECTION 1’ Size fraction

Thickness

259

HISTORY

Horizon

(cm)

% Sand (2-0.05 mm)

Bkbl Bkb2 Bkb3 Bkb4 Bkb5 Bkb6 Bkb7

o-15 15-33 33-58 58-78 78-113 113-135 135+

21.0 37.2 47.1 20.8 36.7 51.5 10.4

.-

% Silt (0.05-0.002 mm)

% Clay (co.002 mm)

pH (1:l)

(%) Calcium carbonate

m Organic matter

(%) Organic carbon

42.5 32.4 20.3 52.8 26.5 34.3 59.0

36.5 30.4 32.6 26.4 36.8 14.2 30.6

8.2 8.3 8.3 8.5 8.2 8.3 8.1

36.0 36.5 32.5 22.0 22.0 15.0 18.5

0.238 0.294 0.350 0.266 0.252 0.168 0.238

0.138 0.171 0.203 0.154 0.146 0.097 0.138

D Field descriptions follow Soil Survey Staff (1951) and Guthrie and Witty (1982).

Bkbl

Bkb2

Bkb3

Bonneville Alloformation and Bear River alluvium of post-Lake Bonneville age. Field conditions moist. Diagnostic horizon is calcic; original surface horizons have been truncated. O-15 cm, light gray (2.5Y 7/2) to white 2.5Y 8/2) clay loam; medium to coarse strong prismatic; firm; violent effervescence with HCl on segregated carbonates l-3 mm thick and on disseminated carbonates; common fine, irregular to rounded mottling from Lake Bonneville waterlogging following soil formation; gradual smooth boundary. Stage II carbonate morphology. 15-33 cm, light grayish brown (2SY 612) to white (2.5Y 8/2) clay loam; medium to coarse strong prismatic; firm; violent effervescence on carbonates segregated in seams and filaments l-3 mm thick and disseminated; few fine irregular to rounded mottles from Lake Bonneville waterlogging as above; gradual smooth boundary. Stage II carbonate morphology. 33-58 cm, light grayish brown (2.5Y 612) to white (2.5Y 8/2) sandy clay loam; medium to coarse strong prismatic; firm; violent reaction on carbonates segregated in seams and filaments l-3 mm thick and disseminated; no mottling; gradual smooth

Bkb4

Bkb5

Bkb6

Bkb7

boundary. Stage II carbonate morphology. 58-78 cm, very pale brown (IOYR 7/3) silt loam; medium to coarse strong prismatic; firm; violent effervescence on carbonates segregated in seams and filaments l-3 mm thick and disseminated: no mottling; clear smooth boundary. Stage II carbonate morphology. 78-113 cm, very pale brown (10YR 7/3) clay loam; medium to coarse strong angular blocky; firm; violent effervescence on carbonates segregated in seams and filaments 1-3 mm thick and disseminated; few to common, fine to medium, irregular mottles from pre-Bonneville pedogenesis; abrupt smooth boundary. Stage II carbonate morphology. 113-135 cm, pale brown (10YR 613) loam; medium to coarse strong angular blocky; very friable; weak effervescence on carbonates segregated in seams and filaments l-3 mm thick and disseminated; few fine rounded mottles from pre-Bonneville pedogenesis; abrupt smooth boundary. Stage I carbonate morphology. 135 cm + , pale brown (ZOYR 6/3) silty clay loam; medium to coarse strong angular blocky; very friable; strong effervescence on carbonates in segregated seams and filaments

260

CHARLES

G. OVIATT

l-3 mm thick and disseminated; few common fine to medium irregular mottles from pre-Bonneville pedogenesis, Stage I carbonate morphology.

Location: Section 4 Parent material: Cutler Dam Alloformation ? and Little Valley Alloformation ? (see text) Additional notes: Buried by 4 m of silt and sand of the Bonneville Alloformation; mottling-gleying in upper B horizon possibly due to fluctuating water table prior to truncation and inundation by Lake Bonneville. Mottling seems to follow old root zones, which penetrate the Bt horizon. Diagnostic horizons are argillic over calcic; original surface horizons are missing. Field conditions are moist (m) and dry (d). Btbl O-23 cm, very pale brown (10YR 7/3, d) clay; medium to coarse strong angular blocky to prismatic; firm (m); no effervescence; many fine distinct mottles in thread form; abrupt smooth boundary; stone line of transgressive beach gravels lies at top of this horizon on unconformity.

Btgbl Btgbt Btb3 Btkb4 Bkmb 1 Bkmb2 Bkmb3 a Field

LABORATORY

DATA

FOR BURIED

SOIL

PROFILE

AT SECTION

% Sand (2-0.05 mm)

% Silt (0.05-0.002 mm)

% Clay (<0.002 mm)

O-23 23-38 38-60 60-78 78-110 1 lo-130 130- 180+

1.89 1.85 11.80 8.98 54.50 60.90 88.30

19.3 13.5 15.2 29.6 31.9 40.5 61.4

33.1 39.2 37.2 27.0 26.8 24.6 10.2

47.6 47.3 47.6 43.4 41.3 34.9 28.4

7.5 7.8 8.1 8.3 7.9 7.8 7.6

descriptions

follow

and Witty

(1982).

(cm)

40

Size fraction

%> 2 mm dia.

Thickness Horizon

A2.

’ r

AL.

Btb2 23-38 cm, very pale brown (IOYR 7/3, d) clay; medium to coarse strong angular blocky to prismatic; firm (m); no effervescence except on limestone particles; common fine distinct mottles in thread form; clear smooth boundary. Btb3 38-60 cm, pale brown (10YR 6/3, d) clay; medium to coarse strong angular blocky to prismatic; firm (m); no effervescence except on limestone particles; few fine faint mottles in thread form; clear smooth boundary. Btkb4 60-78 cm, very pale brown (IOYR 8/3, d) clay; fine to medium moderate subangular blocky; firm (m); weak effervescence on disseminated carbonates; clear smooth boundary; stage II carbonate morphology. Bkmbl 78- 110 cm, very pale brown (IOYR 7/3, 8/3, d) very gravelly clay; fine to medium moderate subangular blocky; firm (m); violent effervescence on carbonates segregated in seams and filaments; clear smooth boundary; stage II carbonate morphology. Bkmb2 1 lo- 130 cm, white (5YR 8/l, d) very gravelly clay loam; fine strong platy; friable (m); violent effervescence on carbonates segregated in seams and filaments;

APPENDIX 2 Description of Buried Soil Profile at Section 4 (See Table A2)

TABLE

ET

Soil Survey

Staff

(1951)

and Guthrie

(%I pH Calcium (1: 1) carbonate 1.0 1.5 6.0 6.0 27.0 39.0 33.0

(%o) Organic matter

(%o) Organic carbon

0.25 0.30 0.25 0.25 0.46 0.59 0.68

0.15 0.18 0.15 0.15 0.27 0.31 0.39

BONNEVILLE

BAS IN LAKE

gradual smooth boundary; stage III carbonate morphology. Bkmb2 130- 180 cm + , white (5YR 8/l, d) very gravelly sandy clay loam; friable (m); violent effervescence on carbonates segregated in seams and filaments; stage III carbonate morphology. ACKNOWLEDGMENTS We thank B. J. Albee, A. J. Feduccia, R. M. Forester, J. H. Madsen, Jr., and G. R. Smith for the identification and interpretation of fossils, and D. R. Currey for helpful discussions in the field. G. Huckleberry analyzed soil samples. This work was partially supported by the Utah Geological and Mineral Survey as part of a geologic quadrangle mapping program (Oviatt, 1986a, 1986b), and by NSF Grants EAR-7913793 and ATM-8205341 to McCoy. D. R. Currey and W. E. Scott reviewed the manuscript and offered valuable suggestions for its improvement.

REFERENCES Arnow, T. (1984). “Water-Level and Water-Quality Changes in Great Salt Lake, Utah, 1847-1983.” U.S. Geological Survey Circular 913. Bright, R. C. (1963). “Pleistocene Lakes Thatcher and Bonneville, Southeastern Idaho.” Ph.D. thesis, University of Minnesota, Minneapolis. Clark, C. U., and Lea, P. D. (1986). Reappraisal of early Wisconsin glaciation in North America. Geological Society of America Abstracts with Programs 18, 565. Currey, D. R.. and Oviatt, C. G. (1985). Durations, average rates, and probable causes of Lake Bonneville expansions, stillstands, and contractions during the last deep-lake cycle, 32,000 to 10,000 years ago. In “Problems of and Prospects for Predicting Great Salt Lake Levels: Papers From a Conference Held in Salt Lake City, March 26-28, 1985” (P. A. Kay and H. F. Diaz, Eds.), pp. 9-24. Center for Public Affairs and Administration, University of Utah. Currey, D. R., Oviatt, C. G., and Czarnomski, J. E. (1984). “Late Quatemary geology of Lake Bonneville and Lake Waring,” pp. 227-237. Utah Geological Association Publication 13. Currey, D. R., Oviatt, C. G., and Plyler, G. B. (1983). “Lake Bonneville stratigraphy, geomorphology, and isostatic deformation in west-central Utah,” pp. 63-82. Utah Geological and Mineral Survey Special Studies 62. Feduccia, A., and Oviatt, C. G. (1986). A trumpeter swan (Cygnus buccinator) from the Pleistocene of Utah. Great Basin Naturalist 46, 547-548. Gile, L. H., Peterson, F. F,, and Grossman, R. B.

HISTORY

261

(1966). Morphological and genetic sequences of carbonate accumulation in desert soils. Soil Science 101, 347-360. Guthrie, R. L., and Witty, J. E. (1982). New designations for soil horizons and layers in the new Soil Survey Manual. Soil Science Society qf America Journal 46, 443-444. Hunt, C. B., Varnes, H. D., and Thomas. H. E. (1953). “Lake Bonneville: Geology of northern Utah Valley, Utah,” pp. l-99. U.S. Geological Survey Professional Paper 257-A. Imbrie, J., and Imbrie, J. Z. (1980). Modeling the chmatic response to orbital variations. Science 207, 943-951. Machette, M. N. (1985). Calcic soils of the south western United States. In “Soils and Quatemary Geology of the Southwestern United States” (D. 1,. Weide, Ed.), pp. 1-21. Geological Society of America Special Paper 203. McCalpin, J. (1986). Thermoluminescence (TL) dating in seismic hazard evaluations: An example from the Bonneville basin, Utah. In “Proceedings of the 22nd Symposium on Engineering Geology and Soils Engineering,” Boise, Idaho, February 24-26, 1986, pp. 156- 176. McCalpin, J., Robison, R. M., and Garr, J. D. (in press). Neotectonics of the Hansel Valley-Pocatello Valley corridor, northern Utah and southern Idaho. In “Evaluation of Urban and Regional Earthquake Hazards and Risk in Utah” (W. W. Hays and P. L. Gori, Eds.). U.S. Geological Survey Professional Paper. McCoy, W. D. (1981). “Quaternary Aminostratigraphy of the Bonneville and Lahontan basins, Western U.S., with Paleoclimatic Implications.” Ph.D. dissertation, University of Colorado. Boulder. McCoy, W. D. (1987). Quatemary aminostratigraphy of the Bonneville basin, western United States. Geological Society of America Bulletin 98, 99- 112. Miller, G. H., Brigham, J. K., and Clark, P. U. (1982). Alteration of the total aIle/Ile by different methods of sample preparation. In “Amino Acid Geochronology Laboratory Report of Current Activities” (G. H. Miller, Ed.), pp. 9-20. Institute of Arctic and Alpine Research, University of Colorado, Boulder. Morrison, R. B. (1965a). “Lake Bonneville: Quaternary Stratigraphy of Eastern Jordan Valley. South of Salt Lake City, Utah.” U.S. Geological Survey Professional Paper 477. Morrison, R. B. (1965b). “New Evidence on Lake Bonneville Stratigraphy and History from Southern Promontory Point, Utah,” pp. CllO-C119. U.S. Geological Survey Professional Paper 525-C. Morrison, R. B. (1966). Predecessors of Great Salt Lake. In “The Great Salt Lake” (W. L. Stokes, Ed.), pp. 77-104. Utah Geological Society Guidebook to the Geology of Utah 20.

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Morrison, R. B. (1967). Principles of soil stratigraphy. In “Quaternary Soils” (R. B. Morrison and H. E. Wright, Eds.), INQUA Proceedings Vol. 9, pp. l-69. VII Congress, Center for Water Resources Research, University of Nevada. Morrison, R. B. (1975). Predecessors of Great Salt Lake. Geological Society of America Abstracts with Programs 7, 1206. North American Commission on Stratigraphic Nomenclature (NACSN) (1983). North American Stratigraphic Code. American Association of Petroleum Geologists Bulletin 20, 841-875. Oviatt, C. G. (in press). Lake Bonneville stratigraphy at the Old River Bed, Utah. American Journal ofScience. Oviatt, C. G. (1986a). “Geologic Map of the Cutler Dam Quadrangle, Box Elder and Cache Counties, Utah.” Utah Geological and Mineral Survey Map 91. Oviatt, C. G. (1986b). “Geologic Map of the Honeyville Quadrangle, Box Elder and Cache Counties, Utah.” Utah Geological and Mineral Survey Map 89. Oviatt, C. G., McCoy, W. D., and Reider, R. G. (1985). Quaternary lacustrine stratigraphy along the lower Bear River, Utah: Evidence for a shallow early Wisconsin lake in the Bonneville basin. Geological Society ofAmerica Abstracts with Programs 17, 260. Pierce, K. L., Obradovich, J. D., and Friedman, I. (1976). Obsidian hydration dating and correlation of Bull Lake and Pinedale Glaciations near West Yel-

ET AL.

lowstone, Montana. Geological Society of Americrr Bulletin 87, 703-710. Reider, R. G. (1985). Soil formation at the McKean archaeological site, northwestern Wyoming. In “McKeaniMiddle Plains Archaic: Current Research” (M. Kornfeld and L. C. Todd, Eds.), pp. 51-61. Occasional Papers on Wyoming Archeology, Number 4, Wyoming Recreation Commission. Cheyenne. Scott, W. E., McCoy, W. D., Shroba, R. R.. and Rubin, M. (1983). Reinterpretation of the exposed record of the last two cycles of Lake Bonneville, western United States. Quaternary Research 20, 261-285. Shackleton, N. J., and Opdyke, N. D. (1973). Oxygen-isotope and paleomagnetic stratigraphy of equatorial Pacific core V28-238: Oxygen-isotope temperatures and ice volumes on a lo5 year and lo6 year scale. Quaternaty Research 3, 39-55. Soil Survey Staff (1951). “Soil Survey Manual.” U.S. Department of Agriculture Handbook No. 18. Spencer, R. J., Baedecker, M. J.. Eugster, H. P., Forester, R. M., Goldhaber, M. B., Jones, B. F., Kelts, K., McKenzie, J., Madsen, D. B., Rettig, S. L., Rubin, M., and Bowser, C. J. (1984). Great Salt Lake, and precursors, Utah: The last 30,000 years. Contributions to Mineralogy and Petrology 86, 321-334. U.S. Geological Survey (1974). “Surface Water Supply of the United States, 1966-70,” Part 10, “The Great Basin.” Water-Supply Paper 2127.