CIRC. 1119 

U.S. GEOLOGICAL SURVEY CIRCULAR 1119 

Proceedings of the Workshop 

"Ongoing Paleoclimatic Studies in the 

Northern Great Basin," Reno, Nevada, 

May 1993 

Proceedings of the Workshop 

"Ongoing Paleoclimatic Studies in the 

Northern Great Basin," Reno, Nevada, 

May 1993 

Edited by Larry V. Benson 

U.S. GEOLOGICAL SURVEY CIRCULAR· 1119 
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary 

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director 

The use of firm, trade, and brand names in this report is for identification purposes only and 

does not constitute endorsement by the U.S. Government 

U.S. GOVERNMENT PRINTING OFFICE: 1996 

Free on application to the 

U.S. Geological Survey 

Information Services 

Box 25286 Federal Center 

Denver, CO 80225 

Library of Congress Cataloging-in-Publication Data 

Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin" (1993: Reno, Nev.) Proceedings 

of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993/ 

edited by Larry V. Benson. 

p. em.- (U.S. Geological Survey circular; 1119) 

Includes index. 

1. Paleoclimatology-Great Basin-congresses. 2. Great Basin-climate-Congresses. 

I. Benson, Larry V. II. Title. Ill. Series 

QC884.W67 1993 96-29329 

551.6979-dc20 CIP 
PREFACE 

The workshop "'Ongoing Paleoclimatic Studies in the Northern Great Basin" was jointly sponsored by 

the U.S. Geological Smvey (USGS), the University ofNevada-Reno (UNR), and the Quaternary Sciences Center 

(QSC) of the Desert Research Institute, Reno, Nevada. W. Berry Lyons, chairman of the Hydrology Program 

(UNR), and Dale Ritter, head of the QSC, chaired the presentations. On May 16, Joseph Smoot, of the USGS, 

led a field trip along the Truckee River Canyon downstream from Wadsworth, Nevada. The subject of the 

field trip was the Quaternary-Holocene sedimentary record exposed in the Truckee River Canyon. On May 19, 

Larry Benson of the USGS led a field trip on the origin, order of formation, and age of carbonates deposited in the 

Pyramid Lake area. Joseph Liddicoat of Columbia University, Andrei Sarna-Wojcicki of the USGS, Peter Wigand 

of the QSC, and James Yount of the USGS led discussions in the field. W. Berry Lyons arranged for lunches, 

field-trip transportation, and conference facilities. 

Larry V. Benson, Editor 

CONTENTS 

Preface................................................................................................................................................................................... III 

Meeting highlights................................................................................................................................................................. 1 

Abstracts of presentations...................................................................................................................................................... 5 

Long Quaternary Records from the Northwestern Basin and Range Province, California and Oregon 

hy David P. Adanl ..................................................... .................................... ................... ............................................ 7 

Table 1. General summary of results from core sites in the Upper Klamath Basin and vicinity 

that were sampled during 1991-92 ................................................................................................... 7 

Last 200,000 Years of Glacial History at Bishop Creek, Eastern Sierra Nevada, California 

by Andrew Bach, Ronald Dom, Tanzhuo Liu, F.M. Phillips, Marek Zreda, David Elmore, 

Deborah Elliott-f?isk, ancl Jan1.es Clark......................................................................................................... 9 

Table 1. Estimated ages, rock-varnish microlamination, and solum depth ofmorained sequences, 

Bishop Creek, eastern Sierra Nevada................................................................................................. 10 

Thermoluminescence Tephrochronometry-Principles, Examples, and Potential 

b.v Glenn W. Berger...................................................................................................................................................... 13 

Figure 1. Relation between the thermoluminescence age determined by additive-dose procedure 

and carbon-14 or fission-track-based ages for five tephra samples.................................................... 13 

Geochemical Variations in Sediments and Pore Waters of OL-92, a 323-meter Drill Hole from Owens Lake, 

California, and their Probable Climatic Significance 

by James L. Bischoff. George 1. Smith, Jeffi·ey P. Fitts, Kirsten M Men king, and Hannah M Musler ...................... 17 

Uranium-Series Dating of Sediments from Walker and Pyramid Lake Basins, Nevada 

by Charles A. Bush, Larry V. Benson, and John N Rosholt........................................................................................ 19 

Table 1. Sununary of sample data and calculated ages of sections of core from Walker Lake and 

Pyramid Lake ........................ .......... ............ .................................................. ..... ................................ 20 

Figure 1. Age-depth plot ofcarbon-14, tephrochronology, and uranium-series-dated segments of 

Walker Lake cores WLC84-4, WLC84-5, and WLC84-8 ........... ...................................................... 20 

Application of Magnetic Susceptibility and Grain Size in a Lithostratigraphic Study of Middle to Late Pleistocene 

Lacustrine Sediments Near Sununer Lake, Oregon 

by Daniel B. Erbes and Robert M. Negrini ................................................................................................................. 23 

Paleoclimatic Implications of Late Quaternary Lake-Level Variations in South-Central Oregon 

by Do1vthy E. rl·eidel .................................................................... ........ .... ........ .......................................................... 25 

Paleomagnetism of Owens Lake Sediments-Constraints on the Timing of Climate Fluctuations in the Quaternary 

by Jonathan M. Glen, Robert S. Coe, Shannon S. Baughn, and George 1. Smith ....................................................... 29 

Prehistoric Human Occupation and Changing Lake Levels at Pyramid and Winnemucca Lakes, Nevada 

b.v Eugene M Hattori and Donald R. Tuohy............................................................................................................... 31 

Figure 1. Radioc';U'bon ages of human occupation in the Pyramid and Winnemucca Lake areas.................... 31 

Table 1. Radiocarbon dates tor archaeological materials from Pyramid Lake and Winnemucca Lake.......... 33 

Contents V 
High-Resolution Simulations of Climate ofthe Western United States_at 18,000 Years B.P. 

by Steve W. Hostetle1; F. Giorgi, Gm:v r Bates, and Patrick J. Bartlein.................................................................... 35 

Initial Results from Paleoclimatic and Geophysical Studies of Washoe Lake, Nevada 

by Robert E. Karlin, James r Trexler, and Ronald Petersen...................................................................................... 37 

Detailed Sedimentary Record of Changes in the Level of Lake Lahontan from the Hot Springs Mountains, Nevada 

h.v Nicholas Lancaster................................................................................................................................................. 39 

Changes in Pyramid Lake Sediment Composition in Relation to Fluctuations in Lake Level and Land-Use Practices 

by Martin E. Lebo, John E. Reute1; and Philip A. Meyers.......................................................................................... 41 

Paleomagnetic Dating and Correlation of Pre-Holocene Lake Sequences in the Northern Great Basin 

by Joseph C. Li{/{/icoat ................................................ ........................... .......................... ...................... ..................... 43 

Design of Drive Samplers for Cohesive Sediments 

by Daniel A. Livingstone............................................................................................................................................. 45 

Late Quaternary Stratigraphy of Owens Lake, California 

by Steve P. Lund, Mark S. Newton, Douglas E. Hammond, Owen K. Davis, and J. Platt Bradbw:v.......................... 4 7 

Figure 1. Correlation of four late Quaternary sediment cores collected from the south-central part 

of Owens Lake.................................................................................................................................. 48 

Figure 2. Magnetic-susceptibility profile for core OWL90/2 .......................................................................... 49 

Figure 3. Summary plot of dry-weight percentages of organic material, calcium carbonate, and clastics 

in Units B through D from Owens Lake, California ........................................................................ 50 

Holocene Lake-Level Variations and Eolian Activity in the Oregon Great Basin 

by Patricia F. McDowell an(/ Daniel P. Dugas........................................................................................................... 53 

Sedimentary Analyses from the Owens Lake Core and Their Implications for Climate 01ange 

by Kirsten M Menking, Hannah M Musle1; RobertS. Anderson, James L. Bischoff, and Jeffrey P. Fitts................ 55 

Figure 1. Mean grain size as a function of depth in core OL-92 from Owens Lake, California .............. ....... 55 

Intrabasinal and Extrabasinal Correlations of Nonmarine High-Resolution Paleomagnetic Records ofthe Middle 

to Late Pleistocene from South-Central Oregon 

b.v Robert M Negrini ................. ................ .................... .. .. ............ ............... .................................... ..... ..................... 57 

Paleoclimatic Inferences from Detailed Studies of Lake Bonneville Marl, Utah 

b_v C'harles G. Oviatt................................................................................................................................................... 59 

Marine-Terrestrial Correlation as a Means of Testing Global Climate Change 

b_v Milan J. Pavich...................................................................................................................................................... 61 

Calcium Carbonate Formation in Pyramid Lake, Nevada 

b.v Michael M. Red(~V .............................................................. ............................... ..... ............................... ................. 67 

Climate of the Great Basin 

b.v Kelly Re(/nlon{/ ....... .................................... ........................ .................................... ....... ......................................... 69 

Climatic Control of Late Quaternary Sedimentation on the Leidy Creek Fan in Fish Lake Valley, 

Nevada-Calif(:>rnia-Implications for Geomorphic Processes in Semiarid Climates 

by Marith C. Reheis and Constance K. Throckmorton............................................................................................... 71 

Figure 1. Generalized geologic map of Leidy Creek fan and vicinity in Fish Lake Valley showing 

locations of core holes and exposed age-control sites...................................................................... 72 

VI Contents 
Spatial and Temporal Variation in Nitrogen Fixation in Pyramid Lake, Nevada 

by Catluyn L. Rhodes, John E. Reute1; Martin E. Lebo, and Charles R. Goldman.................................................... 75 

Middle Holocene Decrease in the Surface Level of Lake Tahoe, Nevada and California 

b.v Martin Rose an{/ Susan Lin{/st1vrn . ........................ ............ ............ ............ ................... ................................ ......... 77 

Sediment-Magnetic and Paleomagnetic Records of Middle Pleistocene Sediment from Buck Lake, Southern Oregon 

by Joseph G. Rosenbaum, Richard L. Reynolds, Priscilla Fitzmaurice, David P. Adam, and 

Andrei M Sarna-Wojcicki....................................................................................................................................... 81 

Figure 1. Plots of magnetic properties with depth, Buck Lake core 1 ............................................................. 82 

Tephrochronology in Studies of Middle to Late Quaternary Climate Change, Northern Great Basin 

by Andrei M Sarna- Wojcicki, Charles E. Meye1; and Elmira Wan ............................................................................ 83 

Figure 1. Location of middle to late Quaternary volcanic sources and sites where studies of 

Quarternary climate change are being conducted or have been recently completed....................... 84 

Table 1. Tephra layers useful in correlation of upper Quaternary sediments, northern Great Basin............... 85 

Effect of Holocene Climatic Fluctuations on Alluvial-Fan Deposition, Fish Lake Valley, Nevada-California 

h.v Janet L. Slate.......................................................................................................................................................... 87 

Figure 1. Location map of Fish Lake Valley in Nevada and California .......................................................... 88 

Figure 2. Chronology of Fish Lake Valley depositional pulses compared to proxy paleoclimatic records 

of the White Mountains, Eureka Valley, and Sierra Nevada during the last 7,000 yr B.P................ 89 

Table 1. Geochronologic controls on alluvial-fan-deposit ages...................................................................... 90 

Table 2. Average age ranges of depositional pulses within Holocene surficial units (Q7, Q6, Q5, Q4) 

in Fish Lake Valley, number ofcarbon-14 and tephra samples providing age control, and 

inferred paleoclimate for those times based on records in the nearby White Mountains, 

Eureka Valley, and Sierra Nevada ........ ...................... ..................................................................... 92 

Preliminary Report on the Ostracod Record from Pyramid Lake, Nevada 

h.v Alison J. Smith........................................................................................................................................................ 95 

Figure 1. Fossil ostracod abundance with depth in Pyramid Lake cores......................................................... 95 

Lithologic Variations in Core OL92 from Owens Lake, California, and Their Probable Climatic Significance 

by George I. Smith, James L. Bisclu~ff, and Jonathan Glen........................................................................................ 99 

Sedimentary Record of Climatically Induced Lake-Level Fluctuations, Pyramid Lake, Nevada 

h_yJoseph P. Smoot ...................................................................................................................................................... 101 

Uranium-Series Dating of Tufas from Pyramid Lake, Nevada 

h.v Barne.v J. Szabo and Larr.v V. Benson ......................... ........................................................................................... 1 03 

Changes in the Pyramid Lake, Nevada, Drainage Basin as Indicated by the Organic Content of Recent Sediments 

b.v Gabrielle E. Tenzer and Philip Me.vers .................................................................................................................. 105 

Figure 1. Selected chemical characteristics of shallow- and deep-basin cores in the Pyramid Lake 

drainage basin ................................................................................................................................... 105 

Late Quaternary Vegetation and Stable-Isotope Record from the Lahontan Basin 

b.v Peter E. Wigand...................................................................................................................................................... 109 

Sedimentary Facies, Quaternary History, and Paleoclimatic Implications from Sediments in Mohawk Valley, 

California 

hyJames C. Yount, DavidS. Harwood, John P. Bradbury, Andrei M Sanw-Wojcicki, and Charles E. Meyer ......... 111 

Contents VII 
CONVERSION FACTORS 

Multiply By To obtain 

centimeter (em) 0.394 inch 

cubic centimeter (cm3

) 0.0610 cubic inches 

gram (g) 0.00220 pounds 

kilometer (km) 0.621 miles 

liter (L) 1.06 liquid quart 

meter (m) 3.28 feet 

microgram (Jlg) 2.20x1o-9 pounds 

micrometer (J..tm) 3.94xlo-5 inch 

millimeter (mm) 0.0394 inch 

square kilometer (kin2) 0.386 square mile 

VIII Contents 

Temperature in degrees Celsius CCC) may be converted to degrees Fahrenheit eF) as 

follows: 0 f= 1.8 °C+ 32 

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as 

follows: 
Meeting Highlights 

Larry V. Benson, U.S. Geological Survey 

Introduction 

One of the major pmposes of paleoclimatic and 

paleohydrologic studies is the determination of the 

degree of synchroneity of clin1ate change recorded in 

marine and terrestrial sediments. A meeting was held 

in Reno, Nevada, on May 16-19, 1993, to exchange 

information and discuss the progress of ongoing 

paleoclimatic studies of one terrestrial area, the 

northern Great Basin of the Western United States. 

Several research topics were discussed including: 

n1ethods of age estimation, glacial-lacustrine 

associations, high-frequency variations in lake level, 

and the frequency and duration of drought in the 

Holocene period. 

Primary Methods of Age Estimation 

Pritnary tnethods of age estitnation and their 

application to the sediments (chetnical and detrital) 

were discussed by G.W. Berger, C.A. Bush, and 

B.J. Szabo. G.W. Berger reported that fine-silt-size 

rhyodacitic glass shards in ash beds arc suitable for 

thermolun1inescence (TL) dating, using the additivedose procedure originally developed for fired pottery. 

He also reported excellent results for a suite of 

independently dated tephra using newly developed 

sample-purification procedures. Rhyodacite glasses 

can be accurately dated by TL to 450,000 years before 

present (yr B.P.). Present in this context refers to 1950. 

In a pilot study of five sections of sediment core 

frmn Walker and Pyramid Lakes, Nevada, C.W. Bush 

demonstrated that closed systems (with respect to 

uranium and its daughters) are sometimes maintained 

within some sections of sediment. Uranium-series 

method4ii, therefore, can somctin1es be used to estimate 

the age of lake sedinlent4ii deposited outside the age 

range of the radiocarbon ( 14C) tnethod. 

B.J. Szabo presented results from a study of the 

tufa mounds that border Pyramid Lake indicating that 

uranium-series method4ii can be used to approximate the 

ages of such tufa deposits. In the Pyramid Lake Basin, 

tufas less than 50,000 years old contain large quantities 

of excess thorium, and the error in age estimates made 

using uranium-series methods is not small enough to 

confirm results from 14C determinations. Carbonate 

cements formed between about 400,000 and about 

60,000 yr B.P. at the Marble Bluff locality contain 

small amount~ of excess thorium and seem to yield 

reliable uranium-series ages. The source of the excess 

thorium present in the Pyramid Lake Basin between 

about 60,000 and about 50,000 yr B.P. has not been 

determined. The presence of large quantities of 

uranium and thorimn in tubular structures present at the 

base of tufa mounds indicates that thorium may have 

been transported in ground water to the lake as a 

colloidal suspension. 

Secondary Methods of Age Estimation 

Correlation within and between lake basins 

is highly desirable. Tephrochronologic and 

paleomagnetic methods show great promise in 

providing a means of achieving this goal. 

A.M. Sarna-Wojcicki provided a comprehensive 

overview of the field of tephrochronology. He 

reported that much of the Great Basin is downwind of 

two tnajor volcanic areas that have been sources of 

sporadic, but prolific, explosive volcanic activity 

throughout middle and late Quaternary time. These 

volcanic source areas are the Ca~cade Range of 

Wa~hington, Oregon, and northern California and the 

Long Valley-Mono Craters area of ea4i!t-central 

California. Isotopic and other numerical ages 

determined on widespread ash layers from these source 

area~ provide local and regional age control, whereas 

chemical and petrographic characterization of the 

layers allows unambiguous temporal correlation of 

a~sociated sediments. Tephrochronology is currently 

(1993) being applied to sediments ofFish Lake Valley, 

Fort Rock Basin, Lake Bonneville, Lake Chewaucan, 

Owens Lake, Pyramid Lake, Walker Lake, and Washoe 

Lake. 

MEETING HIGHLIGHTS 1 
Several researchers (D.B. Erbes, J.M. Glen, 

J.C. Liddicoat, S.P. Lund, R.M. Negrini, and 

J.G. Rosenbaum) gave presentations on the 

applicability of paleomagnetic methods to dating and 

correlation of stratigraphic sequences in lake basins. 

As discussed by R.M. Negrini, palemnagnetic secular 

variation (the low-amplitude variation in the intensity 

and direction of the Earth's magnetic field) offers a 

high-resolution tool that can be used for intrabasinal 

and interbasinal correlation. This method could be 

used to correlate nonmarine stratigraphies with the 

marine chronology. 

J.C. Liddicoat discussed polarity reversals and 

other unusual field behaviors that serve as stratigraphic 

markers. Two such 1narkers are a pole path that loops 

through the South Pacific and is recorded in the 

sediment on Paoha Island in the Mono Lake Basin and 

in Long Valley, California. This marker has been 

assigned an age of about 150,000 yr B.P. Another 

marker is the Mono Lake excursion present in 

sediments from the Lahontan and Mono Lake Basins, 

which has been assigned an age of about 27,000 ± 

1,000 yr B.P. 

J.G. Rosenbaum discussed the results of a 

magnetic study ofsediment'i from Buck Lake, Oregon. 

One of the results of this study was the demonstration 

that magnetic susceptibility and pollen zonations 

closely corresponded with relatively warm climates 

corresponding to low-susceptibility intervals. In 

contrast, high-magnetic susceptibility characterized 

times when sagebrush steppe dmninated the landscape. 

Glacial and Lacustrine Records 

In his discussion of marine-terrestrial 

correlation, M.J. Pavich indicated that climate-forcing 

functions of regular periodicity did not account for 

aperiodic terrestrial records that arc climatically 

related. From a review of the literature, Pavich 

reported that there are hints of similar frequencies of 

change in some marine and terrestrial records, but the 

coherency of change ha'i yet to be determined. 

A. Bach, in his discussion of the glacial history 

of the eastern Sierra Nevada, concluded that at least 

seven major episodes of glaciation occurred at Bishop 

Creek during the past 200,000 years. Surface-exposure 

dating of these deposits indicates that the timing of the 

advances may be correlative with intervals of 

maximum ice sheet volume inferred from marine 

oxygen-18 (8 180) records. Bach suggested that the 

relatively small number of Sierran glaciations 

compared to the number of ice-sheet maxima that 

occurred in the past 200,000 years was due to 

obliterative overlap of older moraines by younger 

moraines and by the limited temporal resolution of 

relative dating methods. 

J.L. Bischoff, K.M. Menking, and G.I. Smith 

discussed ongoing studies of sediment core OL-92 

taken from the Owens Lake Basin, California. 

Bischoff reported that total inorganic carbon {TIC) and 

total organic carbon (TOC) indicate down-core 

variation. Both parameters have minima between 

25,000 and 15,000 yr B.P., corresponding to maximum 

glacial conditions. Older minima in TIC and TOC 

indicate older examples of extreme glacial conditions 

ranging back to 760,000 yr B.P. Bischoff concluded 

that during interglacials, Owens Lake was saline, 

alkaline, and highly productive and that, during 

interglacials, the lake was overflowing with fresh water 

and was relatively unproductive. 

G.I. Smith and K.M. Menking, in their 

discussions of the sedimentology and mineralogy of 

core OL-92, indicated that poorly sorted coarsegrained sediments predominate between 195 m and 

the base of the core (323m). They concluded that 

sediments from the lower part of the core (more than 

490,000 years old) may represent shallow lake or 

fluvial conditions. Fine-grained sediments recovered 

in the top 195 m of core OL-92 were interpreted to 

indicate deep-water conditions. The presence of 

quartz, K-feldspar, and plagioclase feldspar in the claysized sediment fraction was interpreted by these 

authors to result from abrasion of Sierra Nevadan 

bedrock during times of glaciation. 

Holocene Warm/Dry Period 

The existence and timing of an especially warm/ 

dry period during the Holocene have been argued for 

many years. Six speakers (E.M. Hattori, R. Karlin, 

P.F. McDowell, M. Rose, G.I. Smith, and P.E. Wigand) 

presented evidence for such an event. G.I. Smith 

suggested that the presence of a 4.2-m-thick oolite bed 

in the top of the Owens Lake core OL-92 indicates that 

the climate of the past 9,000 years was more arid than 

any time in the past 800,000 years. Based on a study of 

tree stumps submerged in the Lake Tahoe area, Rose 

argued that a large-scale change in climate caused 

2 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
simultaneous recessions of lake levels between 6,300 

and 5,000 yr B.P. in the northern Sierra Nevada. 

Winnemucca Basin, which received water when 

Pyramid Lake spilled, seems to have been dry or nearly 

dry between 9,500 and 8,400 yr B.P. and between 

7,800 and 4,000 yr B.P., according to archaeological 

data presented by E.M. Hattori. P.E. Wigand 

reported that the climate was too dry for woodrats to 

flourish on the western edge of the Lahontan Basin 

between 8,000 and 4,000 yr B.P., also supporting 

Hattori's data. Based on a summary of data from 

eastern Oregon, P.F. McDowell concluded that eolian 

sands dating to equal or less than 6,800 yr B.P. cover 

lake deposits in the Fort Rock Basin and that dunes in 

the Harney Lake Basin began to form just after 5,000 

yr B.P. The pollen record from Diamond Pond also 

indicates that dry conditions existed between 6,000 and 

5,400 yr B.P. 

MEETING HIGHLIGHTS 3 

ABSTRACTS OF 

PRESENTATIONS 

Long Quaternary Records from the Northwestern Basin and 

Range Province, California and Oregon 

David P Adam, U.S. Geological Survey 

The Great Basin of the Western United States is 

the result of an extensional tectonic regin1e that has 

profoundly affected the physiography and drainage 

history of the region since Miocene time. Many 

existing and fonner sedilnentary basins preserve longduration records of past events. Plate-tectonic effects 

along the western margin of North America resulted in 

extensive volcanism in the SierraN evada and in the 

Cascade Range, and the passage of the Yellowstone 

Hot Spot eastward has produced more volcanism. This 

extensive eruptive activity produced many identifiable 

tephra layers that can be used to correlate among 

basins. 

The northwestern Great Basin is particularly 

well suited to long-tenn stratigraphic studies because 

of the proximity of the Cascade Range (many tephra) 

and the relatively recent inception of the extensional 

tectonic regime (most sedimentary basins have 

not yet been breached). Ongoing studies by the 

U.S. Geological Survey have recovered numerous 

sediment cores from the Upper Klamath Basin and 

vicinity in northern California and south-central 

Oregon (table 1). These cores span intervals ranging in 

age from more than 50,000 yr (Wocus Marsh, Oregon, 

and Grass Lake, California) to more than 3,000,000 yr 

(TuleLake, California). Vegetation at the sites now 

ranges from fir forests at the crest of the Cascade Range 

(Buck Lake, Oregon) to sagebrush steppe in the rain 

shadow to the east (Summer Lake, Oregon, and Tul~ 

Lake). Basin sizes range from about 1.5 km across 

(Grass Lake) to as much as tens of kilometers. 

Correlations between cores are based primarily on 

tephra and paleomagnetic polarity changes. Not all 

records are continuous. However, when many cores 

Table 1. General summary of results from core sites in the Upper Klamath Basin and vicinity that were sampled 

during 1991-92 

Site name Core length Recovery Description (meters) 

Butte Valley, California 102 Excellent Both perennial and ephemeral lake deposits; numerous 

tephra; carbonate often preserved. 

Grass Lake, California 29 Excellent Basin dammed by lava flow; lake and marsh deposits at 

top of core, changing to volcanic debris flow at base; 

numerous tephra. 

Buck Lake, Oregon 41.3 Excellent Top 30 meters, lacustrine clay containing numerous tephra; 

bottomll meters, volcanic debris flow underlain by 

basalt. 

Round Lake, Oregon 50 Good Top 25 meters, very tight clays that contain no visible 

tephra; probably representing intermittent lake. 

Excellent Bottom 25 meters, open-water lake muds containing several 

tephra. 

Wocus Marsh, Oregon 52 Excellent Interbedded peats, organic muds, inorganic muds (basaltic 

rock flour?), and tephra. Probably includes glacial 

sediment from Mount Mazama. 

Caledonia Marsh, Oregon 15.3 Good Very soupy lacustrine muds containing several tephra. 

Drilling stopped by artesian conditions. Upper 

12 meters sampled with good recovery using manual 

equipment in 1992. 

ABSTRACTS OF PRESENTATION 7 
are available from va:rying depositional environments 

in a relatively small area, hiatuses in one core tnay be 

bridged by the record in another core, and the hiatuses 

may be interpretable. Multiple cores also offer the 

opportunity to distinguish local (for example, tectonic) 

from regional (for example, climatic) changes. 

Ongoing work on these cores includes detailed 

work on magnetic properties, pollen, diatoms, 

ostracods, and geochemistry. Combined pollen and 

magnetic work on the Buck Lake record indicates that 

tnagnetic susceptibility may function as an easily 

accessible proxy record of climate in this region. 

Pollen work combined with tephrochronologic time 

control indicates that the Buck Lake core includes a 

continuous climatic record that extends from the end of 

deep-sea oxygen-isotope Stage 9 or 11 back through 

most or all of Stage 12 or 14. The Butte Valley core 

record extends back more than a tnillion years; the 

Brunhes-Matuyama bounda:ry is present at a depth of 

65 min the 102-m core. Pollen and ostracod studies of 

that core are nearly complete. 

Multiple long core records can only be retrieved 

from regions in which suitable deposits are widely 

distributed. The Basin and Range province, long 

characterized by an extensional tectonic regime, is one 

of the best places in the world to develop this multiplecore approach; suitable basins are present over a wide 

range of latitudes, climates, and ecological settings, 

and climatic changes have caused spectacular 

alterations in the landscapes of the Great Basin through 

time. Several long records are already available; these 

have provided key insights into the climatic evolution 

of the Earth, but such records have generally been 

studied independently of each other. It seems 

appropriate to view further studies in terms of a large 

and integrated study plan. Although such a plan may 

take many decades to complete, it can be accomplished 

by degrees. However, such a plan cannot achieve its 

full potential without a broad initial vision that includes 

both nested studies of multiple cores in small regions 

and transects of regional records across natural 

gradients. The potential of the Great Basin and 

adjacent regions for such studies is outstanding, and the 

studies described in this abstract and in the rest of this 

volume could be the beginning of a promising future. 

8 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Last 200,000 Years of Glacial History at Bishop Creek, 

Eastern Sierra Nevada, California 

Andrew Bach, Ronald Dorn, and Tanzhuo Liu, Geography Department, 

Arizona State University 

F.M. Phillips and Marek Zreda, Geosciences Department, 

New Mexico Institute of Mining and Technology 

David Elmore, Purdue Rare Isotope Measurement Laboratory, Purdue University 

Deborah Elliott-Fisk, Geography Department, University of California 

James Clark, Chemistry Department, Arizona State University 

Difficulties in accurate age determination and 

correlation of Quaternary age and geomorphic surfaces 

have been a long-standing problem in Quaternary 

research (Porter and others, 1983 ). The lack of 

materials appropriate for absolute age determination 

has caused workers to use various relative dating 

techniques to correlate deposits of Quaternary age (for 

example, Burke and Birkeland, 1979). The assumption 

used in relative dating is that lithology, climate, 

topographic position, and vegetation factors remain 

constant among sites so that the weathering of each 

deposit indicates the time that has elapsed since 

deposition (and the initiation of weathering processes). 

However, because lithologic and climatic factors vary 

between canyons of the east-central Sierra Nevada, 

conflicting conclusions by different workers at the 

same canyons and between canyon'i have resulted 

(Fullerton, 1986). 

According to the classical chronology of 

Blackwelder ( 1931 ), the Sierra Nevada undeiWent 

only two major glaciations during the middle and late 

Pleistocene. Blackwelder's chronology was derived 

from the observation that most drainages in the 

eastern Sierra Nevada have only two or three easily 

distinguished sets of moraines. The basis for this 

chronology was examined using cosmogenic 

chlorine-36 e6cl) buildup in rocks, rock varnish 14c, 

varnish cation ratios, and varnish microstratigraphy to 

establish a numerical chronology for the terminalmoraine complex at Bishop Creek, where the number 

of remaining moraines is unusually large. These dating 

method'i indicated that there have been at least seven 

major glacial advances during the past 200,000 yr. 

The timing of these advances seems to correlate 

well with intervals ofmaximmn global ice volume that 

are inferred from marine oxygen-isotope records. 

However, unlike variation in global ice volume, the 

magnitude (equilibrium-line altitude decreases) of the 

various ice advances at Bishop Creek were nearly 

identical. Thus, the apparently small number of 

glaciations in the classical Sierra Nevada chronology is 

probably accounted for by a combination of 

obliterative overlap of older moraines by younger ones 

and by the limited temporal resolution of relative 

dating methods (Gibbons and others, 1984). 

The Bishop Creek study area is in east-central 

California about midway between Reno, Nevada, and 

Los Angeles, California, near the town of Bishop, 

California. Bateman ( 1965, pl. 2) mapped the 

moraines using Blackwelder's ( 1931) classic 

stratigraphic nomenclature identifying Tioga, Tahoe, 

and SheiWin moraines. Additionally, a younger Tioga 

readvance and an older Tahoe moraine were identified. 

Detailed work on the lateral moraines confirmed 

Bateman's mapping and indicated that the older Tahoe 

moraine is a distinct pre-Tahoe deposit, rather than an 

early pha'ie of the Tahoe deposit (Berry, 1991 ). 

Although four lateral moraines are present 

along the course of Bishop Creek, at lea'it 22 distinct 

pre-Tioga moraines can be mapped in the end-moraine 

con1plex. Previous studies have assigned all of these 

moraines to the Tahoe period (Bateman, 1965; Berry, 

1991 ). Preservation of these moraines is probably due 

to the tectonic setting of the piedmont at Bishop Creek. 

Whereas other Pleistocene glacial deposits in the Sierra 

Nevada are cut perpendicularly by range-front faults, 

the lateral moraines are in a region of warping. 

Warping provides the steepest possible hydraulic 

gradient down the piedmont. Therefore, the glacier 

almost always follows the same path. When moraines 

are down-dropped by faulting, subsequent glacial 

ABSTRACTS OF PRESENTATION 9 
advances easily cover older deposits, obliterating 

surface evidence of their existence (Gibbons and 

others, 1984). At Bishop Creek where faulting has not 

occurred on a large scale and the glaciers entered the 

piedmont at approximately a 45-degree angle to the 

piedmont slope, there is no tectonic mechanism to 

continually create a steep gradient. The glaciers 

behaved similarly to streams on an alluvial fan, flowing 

down one channel where material (till) accumulated 

until the flow gradient began to flatten, while 

steepening the gradient perpendicular to the axis of 

deposition. Given access to an alternative flow 

direction by ice overtopping a lateral moraine or some 

other mechanism, the glacier flowed down the steeper 

gradient, creating a topographic unconformity (crosscut of moraines) (Bach and others, 1992). The final 

result of these changes of the course of these glaciers 

is that extensive later glaciations bypa~s moraines 

deposited by smaller earlier glaciation, and a large 

number are preserved. 

A !though these processes can occur in shorter 

time intervals (for example, surging), dating of the 

deposits indicates that they span at lea~t 180,000 yr. 

The moraines have been grouped into seven age 

classifications (youngest to oldest, I to VII) based on 

analysis of rock varnish and the accumulation of 

cosmogenic 36Cl in tnorainal boulders. Although 

analysis is not complete, preliminary age a~signments 

are listed in table 1. 

Deposits I through VI consist of multiple 

moraine crests that can be further subdivided into 

stadial events. Analysis of soil development on these 

moraines distinguishes four age groups (1, II, III-V, VI) 

that may correlate with soils on four lateral moraines 

up canyon (Berry, 1991). Soils formed on moraines in 

age group III-V vary in morphologic features, 

indicating either that the soils were of different ages or 

that the soil-forming factors varied in intensity between 

sites (most notably eolian additions), resulting in 

different soil development. 

Numerical surface-exposure dating supports the 

hypothesis, ba~ed on morphologic mapping, of at least 

seven major glacial episodes at Bishop Creek. This 

finding strongly supports the obliterative overlap 

hypothesis of Gibbons and others (1984). Although 

Pleistocene glacial deposits in other canyons of the 

Sierra Nevada only contain deposits of two or three 

glacial stages, the fortuitou~ changes in glacial course 

at Bishop Creek allowed deposits to be preserved. The 

combination of obliterative overlap and of the limited 

temporal resolution of relative dating methods (Burke 

and Birkeland, 1979) has resulted in the apparently 

small number of glaciations identified in the Sierra 

Nevada. 

Table 1. Estimated ages, rock-varnish microlamination, and solum depth of morained sequences, Bishop Creek, 

eastern Sierra Nevada 

Estimated age 1 Rock-varnish Solum depth Relative age assignment 

Deposit 

(1o3 year) microlaminations (centimeters) [Bateman, 1965; Berry, 1991] 

I 20-25 2 38 Tioga 

n 31-37 4 56 Tioga 

Ill 65-77 6 92 Tahoe 

IV 95-115 8 101 Tahoe 

v 155-170 10 110 Tahoe 

VI 170-180 12-16 138 Pre-Tahoe 

vn >180 Eroded 79 Sherwin 

1 Based on chlorine-36 data and rock-varnish analysis. 

10 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
REFERENCES 

Bach, A.J., Elliott-Fisk, D.L., Dorn, R.I., and Phillips, F.M., 1992, Glacial avulsion in Pleistocene moraine complexes of 

east-central Sierra Nevada, California, in White Mountain Research Station Symposium, Proceedings, v. 3, p. 17-31. 

Bateman, P.C., 1965, Geology and tungsten mineralization ofthe Bishop district, California, with a section on Gravity study 

of Owens Valley, by L.C. Pakiser and M.F. Kane, and a section on Seismic profile, by L.C. Pakiser: Geological Survey 

Professional Paper 4 70, 208 p. 

Berry, M.E., 1991, Soil-geomorphic analysis oflate Quaternary glaciation, eastern escarpment ofthe Central Sierra Nevada, 

California [abs]: Geological Society of America Abstracts with Programs, v. 22, p. A98. 

Blackwelder, Eliot, 1931, Pleistocene glaciation in the Sierra Nevada and Basin Ranges: Geological Society of American 

Bulletin, v. 42, no. 4, p. 865-922. 

Burke, R.M., and Birkeland, P.W., 1979, Reevaluation ofmultiparameter relative dating techniques and their application to 

the glacial sequence along the eastern escarpment of the Sierra Nevada, California: Quaternary Research, v. 11, no. 1, 

p. 21-51. 

Fullerton, D.S., 1986, Chronology and correlation of glacial deposits in the Sierra Nevada, California, in Quaternary 

glaciations in the Northern Hemisphere: Quaternary Science Review, v. 5, p. 161-169. 

Gibbons, A.B., Megeath, J.D., and Pierce, K.L., 1984, Probability ofmoraine survival in a succession of glacial advances: 

-Geology, v. 12, no. 6, p. 327-330. 

Porter, S.C., Pierce, K.L., and Hamilton, T.D., 1983, Late Wisconsin mountain glaciation in the Western United States, 

in Porter, S.C., ed., The late Pleistocene, v. 1 in the collection Late Quaternary environments of the United States: 

Minneapolis, University of Minnesota Press, p. 71-111. 

Thermoluminescence T eph roch ronometryPrinciples, Examples, and Potential 

Glenn W. Berger, Quaternary Sciences Center, Desert Research Institute 

Quaternary tephras are important for several 

reasons (Sarna-Wojcicki and Davis, 1991 ), particularly 

as a time-stratigraphic marker horizon; yet, until 

recently, there have been no means for the direct dating 

of tephra beds in the range 30,000 to 150,000 yr B.P. 

Although isothermal-plateau fission-track dating has 

recently decreased the upper range boundary to 70,000 

to I 00,000 yr B.P. (Chesner and others, 1991 ), there 

remains a considerable age gap for direct-dating 

methods and a need for an additional, widely 

applicable tephrochronometer for dating the middle 

and late Pleistocene. Fine-silt-size rhyodacitic glass 

ENLARGED AREA 

32 

TREGO HOT+ ~ 241- SPRINGS (/) 

c: 

<( 

~ 16 rM 

0 

Sf- •MAZAMA 

1- MSH-Wn 

o• 

0 8 16 24 

(103 YEARS) 

-

-

-

32 

(j) 

a: 

<( 600 UJ 

>-

M 

0 

..... 500 

z 

u.i 

(.9 

<( 400 

w 

u 

z 

w 

u 300 (j) 

UJ 

z 

~ 200 ...J 

0 

:2 ffi 100 

:c 

1-

shards (4 to II J..Ull) in ash beds have been reported to 

be suitable for thermoluminescence {TL) dating 

(Berger, 1985), using the additive-dose procedure 

(Aitken, 1985; Berger, 1988) originally developed for 

fired pottery; however, only recently have sample 

purification and other appropriate procedures been 

applied to a suite of independently dated tephra 

(Berger, 1991, 1992). Although few independently 

well-dated samples were tested, the results (fig. I) 

demonstrate that such glass can be an accurate TL 

clock for tephra to as much as about 450,000 yr. 

ROCKLAND 

tOLD CROW 

0

o 100 200 300 400 500 600 700 

AGE OBTAINED USING RADIOCARBON 

AND FISSION TRACK METHODS, IN 103 YEARS 

Figure 1. Relation between the thermoluminescence age determined by additive-dose procedure and carbon-14 or 

fission-track-based ages for five tephra samples (modified from Berger, 1985, 1991 ). The solid lines represent errors 

(±1 sigma). New, independent age estimates for Trego Hot Springs tephra (Oregon) (Negrini and Davis, 1992) [corrected 

to 24,000 calendar years (Mazaud and others, 1991 )] and for Rockland tephra (California) (Alloway and others, 1992) are 

incorporated. Heavy-liquid separation was not applied to samples MSH-Wn (Washington) and Mazama (British Columbia). 

The natural 4 to 11 ~m fraction of the Mazama sample contained 95 to 98 percent glass shards, but the proportion of glass in 

this fraction of sample MSH-Wn may be lower. 

ABSTRACTS OF PRESENTATION 13 
Principles 

Volcanic glass shards can function as natural 

radiation dosimeters and are capable of storing a part of 

the absorbed energy from low-level environmental 

ionizing radiations (ambient and exogenous alpha-, 

beta-, gamma-, and cosmic-ray radiations). The stored 

energy can be read out as a luminescence signal that is 

proportional to the accumulated absorbed dose since 

last heating. Heating empties all electron traps 

(thermally stable lattice-defect sites). After burial, 

ionizing radiations repopulate emptied traps. In the 

laboratory, traps are again emptied, by heating, when 

electron-hole recombination produces luminescence. 

When the luminescence signal is related to an 

equivalent dose [(DE) determined with the additivedose procedure] by use of calibrated laboratory 

radiation sources, and an effective radiation dose 

rate is measured in separate experiments, then a 

thermoluminescence age equals DE divided by 

effective dose rate. The objective of the additive-dose · 

procedure is to obtain a plateau in DE values that 

represents stable electron traps. Accurate 

measurement of a plateau DE value ha~ been the single 

greatest practical difficulty in the development of this 

new dating tool for tephra. Dose-rate mea~urements 

have been more straightforward. 

The physical nature of gla~s shard~ and their 

inherent TL properties present practical difficulties. 

Shards larger than about 50 J..U11 sometimes contain 

micro lites and crystallites of feldspar minerals (Fisher 

and Schmincke, 1984). TL fron1 such inclusions, 

which has recently been directly observed (Kanemaki 

and others, 1991 ), dominates the TL from glass. TL 

from volcanic feldspars has long been known to be 

very unstable (Wintle, 1973; Aitken, 1985) and needs 

to be avoided. This is the main reason that 4- to 11-f.Ull 

glass shards were originally preferred by Berger and 

Huntley ( 1982). Separation in quantity of minerals in 

the fine-silt-size fraction traditionally has been 

difficult; however, Berger (1984) developed an 

effective heavy-liquid centrifugation procedure, 

employed for tephra for the first time by Berger ( 198 7). 

Presently ( 1993 ), purification of the preferred 4- to 11-

J..Ull grain-size fraction to 95 to 98 percent glass seems 

the best that can be attained with a single repeat 

centrifugation. 

Removal oflaboratory-it1duced unstable TL also 

presents problems. As with unheated sediments, 

failure to minimize such unstable TL would generate 

age underestimates, other factors being equal. Berger 

( 1991) tested different pre-readout heat treatments for 

removal of unstable TL and reported that heating 

sediments above 7 5°C for a few days can produce 

inaccurate DE values, for reasons not yet understood. 

Examples 

Several previou~ly undated ash beds from 

Summer Lake, Oregon, provided TL glass ages of 

a~ much as 200,000 yr (Berger and Davis, 

1992), which were useful in determining the 

paleoenvironmental history of the enclosing pluviallake sediments. A TL glass age of approximately 

50,000 yr for a Summer Lake tephra bed 

(ash bed 12) that was correlated to Mount St. Helens 

Set Cy tephra beds helps clarity the history of giant 

paleoflooding in eastern Washington (Berger and 

Busacca, 1991 ). In eastern Washington, another TL 

glass age of about 250,000 yr (Berger, 1991) for a 

previously undated ash bed in loess above a flood-cut 

unconformity clearly establishes that cataclysmic 

flooding in this region also occurred within the middle 

Pleistocene. Other examples of applications are 

described by Berger ( 1991 ). Some results need 

confirming by TL dating of additional material. One 

example is that of the Alaskan Sheep Creek tephra bed, 

whose first TL glass age was younger than expected 

from stratigraphic correlations based on geochemical 

fingetprinting of the tephra beds. This first age 

estimate is being confirmed using re-collected ash from 

more than one site. 

Potential 

The testing and application of TL need to be 

extended to glass of composition different from 

rhyodacite. Extension to a wider range of gla~s 

composition could provide a greater variety of dating 

targets, resulting in benefits for several fields of 

Quaternary geology. Additionally, possible extension 

to deposit'i older than about 500,000 yr needs testing. 

Finally, the encouraging result for the 500-yr MSH-Wn 

sample (fig. 1) indicates that TL tephrochronometry 

could be useful in studies of recent volcanism, such as 

in volcanic-hazards evaluation. 

14 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
REFERENCES 

Aitken, M.J., 1985, Thermoluminescence dating: San Diego, Academic Press, 351 p. 

Alloway, B.V., Westgate, J.A., Sandhu, A.S., and Bright, R.C., 1992, Isothermal plateau fission-track age and revised 

distribution of the widespread mid-Pleistocene Rockland tephra in west-central United States: Geophysical Research 

Letters, v. 19, no. 6, p. 569-572. 

Berger, G.W., 1984, Thermoluminescence dating studies of glacial silts from Ontario: Canadian Journal of Earth Sciences, 

v. 21, p. 1393-1399. 

Berger, G.W., 1985, Thermoluminescence dating of volcanic ash: Journal of Volcanology and Geothermal Research, v. 25, 

p. 333-347. 

Berger, G.W., 1987, Thermoluminescence dating of the Pleistocene Old Crow tephra and adjacent loess, near Fairbanks, 

Alaska: Canadian Journal of Earth Sciences, v. 24, no. 10, p. 1975-1984. 

Berger, G.W., 1988, Dating Quaternary events by luminescence, in Easterbrook, D.J., ed., Dating Quaternary sediments: 

Geological Society of America, Special Paper 227, p. 13-50. 

Berger, G.W., 1991, The use of glass for dating volcanic ash by thermoluminescence: Journal of Geophysical Research, v. 96, 

no. B12, p. 19, 705-720. 

Berger, G.W., 1992, Dating volcanic ash by use of thermoluminescence: Geology, v. 20, p. 11-14. 

Berger, G.W., and Busacca, A.J ., 1991, Thermoluminescence dating of loess from eastern Washington-Implications for the 

timing of Wisconsinan giant floods and ofpaleosol development [abs.]: Geological Society of America Abstracts with 

Programs, v. 23, no. 5, p. A106. 

Berger, G.W., and Davis, J.O., 1992, Dating volcanic ash by thermoluminescence-test and application: Quaternary 

International, v. 13/14, p. 127-130. 

Berger, G.W., and Huntley, D.J ., 1982, Dating volcanic ash by thermoluminescence: European PACT Journal, Journal of 

European Study Group on Physical, Chemical, and Mathematical Techniques Applied to Archaeology, Council of 

Europe, Parliamentary Assembly, Strasbourg, v. 9, part II, p. 581-592. 

Chesner, C. A., Rose, W.I., Deino, Al, Drake, R.E., and Westgate, J.A., 1991, Eruptive history of Earth's largest Quaternary 

caldera (Toba, Indonesia) clarified: Geology, v. 19, no. 3, p. 200-203. 

Fisher, R.V., and Schmincke, H.U., 1984, Pyroclastic rocks: New York, Springer-Verlag, 472 p. 

Kanemaki, Motoko, Ninagawa, Kiyotaka, Yamamoto, Iaso, Nakagawa, Masuo, Wada, Tomonori, Yamashita, Yoshihiko, and 

En do, Kunihiko, 1991, Red thermo I uminescence of volcanic glass fractions from tephras: Nuclear Tracks and Radiation 

Measurements, no. 1-2, v. 18, p. 81-88. 

Mazaud, Alain, Laj, Carlo, Bard, Edward, Arnold, Maurice, and Tric, Emmanual, 1991, Geomagnetic field control of 14C 

production over the last 80 ky-Implications for the radiocarbon time scale: Geophysical Research Letters, v. 18, no. 10, 

p. 1885-1888. 

ABSTRACTS OF PRESENTATIONS 15 
Negrini, R.M., and Davis, J.O., 1992, Dating late Pleistocene pluvial events and tephras by correlating paleomagnetic secular 

variation records from the western Great Basin: Quaternary Research, v. 38, p. 4fr59. 

Sarna-Wojcicki, A.M., and Davis, J.O., 1991, Quaternary tephrochronology, in Morrison, R.B., ed., Quaternary nonglacial 

geology--Coterminous U.S.: Geological Society of America, The Geology of North America, v. K-2, p. 93-116. 

Wintle, A.G., 1973, Anomalous fading ofthermoluminescence in mineral samples: Nature, v. 245, p. 143-144. 

16 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Geochemical Variations in Sediments and Pore Waters of OL-92, 

a 323-meter Drill Hole from Owens Lake, California, 

and Their Probable Climatic Significance 

James L. Bischl?[f. George I. Smith, and Je.ffrey P. Fitts, U.S. Geological Survey 

Kirsten M. Menldng and Hannah M. Musler, University o.fCal(fornia, Santa Cruz 

During extreme dry periods (interglacials), 

Owens Lake was saline, alkaline, and biologically 

highly productive. In contrast, during extreme wet 

periods (glacials ), the lake was flushed, overflowing 

with fresh water, and relatively unproductive. The 

transitions between these pha..{o)es are indicated in 

the sedimentary column by marked variations in a 

number of geochemical parameters. Sediments from 

a 323-m drill hole (OL-92) were analyzed for 

radiocarbon, pore-water content and composition, 

CaC03, organic carbon, and cation-exchange capacity 

to determine these climatic changes and place them in 

a temporal context. 

Point samples (50 cm3) for water content and 

pore-water chemistry were obtained during the drilling 

operations at 2- to 3-m intervals for the entire length of 

the core ( 120 samples). Water content varied 

erratically down the core, generally decreasing from 

about 60 wet-weight (wt) percent at the top to about 

20 wt percent at 240 m, but water content sharply 

increa..{o)ed at levels below 240 m to between 40 and 

60 wt percent, indicating substantial undercompaction 

for the lowermost 100 m of the core. The pore waters 

were alkaline (pH 8-10) and had anionic compositions 

ofHCOrC03>Cl>S04, which were similar to the 

chemistry of the modem lake before diversion of the 

source water. The pore-water salinity ranged from 

0.4 to 5 wt percent dissolved solids. Salinity varied 

with depth in a smooth pattern; the minimum was at 

30 m, gradually increasing to a single broad maximum 

at about 150 m, and sharply declining thereafter to 

steady low values at 210 m and below. The salinitydepth profile wa..{o) drastically smeared by postdepositional diffusion of dissolved salts, indicating that 

the present ( 1993) pore-water composition has little 

relation to pore-water composition from the past 

climate. 

Point samples were obtained from the top 24 m 

for accelerator-mass-spectrometer (AMS) radiocarbon 

analyses of extracted humates (15 samples). These 

results indicate a strong linear relation between age and 

depth (83 cm/1 03 yr). The average mass-accumulation 

rate of the Bishop Ash, as calculated from average 

pore-water content, average solid bulk density, 

and apparent accumulation rate (40.0 cm/103 yr) is 

51.4 (g/cm2)/103 yr. A similar calculation for the top 

24 m, using radiocarbon control, results in 

52.4 (g/cm2)/1 03 yr, which is remarkably close to the 

calculated rate for the entire core. An age-depth curve 

for the entire core was determined using radiocarbon 

control from the top of the core and extrapolating 

to the Bishop Ash (759,000 yr at 309-m depth) after 

correcting for compaction using the pore-water data. 

The curve is based on the apparent constancy of the rate 

of sediment-mass accumulation during the 

extrapolation. 

For determination of sediment composition, 

composite strip samples were obtained to represent 

the entire core (total of 91 samples). About 

3.5-m segments of the core were sampled in a 

continuous strip or channel, each representing about 

7,000 yr of deposition. These samples were 

individually homogenized, flushed of their interstitial 

salts, suspended in an aqueous CsCl solution, rinsed 

U{o)ing distilled water, and dried. The CsCl treatment 

replaced all exchangeable cations (overwhelmingly 

Na) in the clay minerals with Cs. Aliquots were 

analyzed for percent CaC03, percent organic carbon, 

percent Cs, and grain-size distribution (sand/silt/clay). 

The percent CaC03, percent organic carbon, and 

normalized Cs (percent Cs/percent clay) in the aliquots 

indicate cyclic variation down the core. All three 

parameters indicate conspicuous and sharp minima at 

15,000 to 25,000 yr, corresponding to maximum 

glacial conditions. These results indicate that, during 

such conditions, the lake was nonproductive and that 

the clay fraction of the sediment (the major size 

component of the sediment) was dominated by glacial 

rock flour, which lacked cation-exchange capacity. 

Minima in these components individually (and more 

clearly in a normalized and summed composite) locate 

ABSTRACTS OF PRESENTATION 17 
a series of older extreme glacial conditions extending 

back to 759,000 yr. Conversely, maxima locate depths 

of interglacial conditions. Summed composites 

indicate that Termination II occurred at 127,000 ± 

10,000 yr. 

18 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Uranium-Series Dating of Sediments from 

Walker and Pyramid Lake Basins, Nevada 

Charles A. Bush, Larry V Benson, and John N Rosholt, U.S. Geological Survey 

For several years, studies have been made near 

many lakes in the Great Basin in an attempt to 

reconstruct regional paleoclimatic history from 

lacustrine sediments. Radiocarbon and uranium-series 

(U-series) methods have been used to determine ages 

of shoreline carbonates (tufas, oolites, and gastropods) 

to reconstruct the chronology of the rise and faJl of the 

lakes in the Lahontan Basin (Lao and Benson, 1988; 

Benson, 1991 ). Organic and inorganic fractions of 

young lake sediment from the Walker and Pyramid 

Lake Basins in Nevada have been dated by 14C 

methods (Yang, 1989; Benson, 1991 ). Dating by 

14C methods, however, can only be applied to 

sediments younger than approximately 40,000 yr B.P. 

Cored sediments from the Walker Lake and Pyramid 

Lake Ba..~ins extend beyond the range of 14C dating; 

therefore, attempts have been made to apply U-series 

methods of age determination to these older core 

sediments. 

The U-series-dating method, as applied to these 

lacustrine sediments, assumes that when CaC03 and 

organic materials are deposited in a subaqueous 

environment, dissolved uranium is coprecipitated with 

the CaC03 and organics and that the carbonates will 

contain negligible amounts of thorium. If the 

carbonate and organic fractions form a closed system 

for uranium and its daughter products, aii 230Th 

tneasured in the CaC03 and organic fraction is 

produced by radioactive decay of uranium after 

incorporation in the material. 

Because the sediments also incorporate silicatemineral detritus that contains significant 

concentrations of230Th and 232Th, a correction for this 

initial or inherited 230Th needs to be applied. Bischoff 

and Fitzpatrick (1991) have described a method of 

dating impure carbonates using an isochron-mixing 

line correction for inherited detrital 230Th where the 

activity ratio of 230Th!232Th is plotted as a function of 

234u;232Th, and 234u;232Th is plotted as a function of 

238u;232rh. The slopes of the _regression lines 

(Ludwig, 1991) of these plot~ provide the 230rh!234u 

and 234u;238U ratios used to calculate the age of the 

CaC03 and organic components in the sediment. The 

approach used here was to plot the measured ratios 

resulting from the total dissolution of several samples 

collected within a short interval in the sediment 

column. Ifthe ratios of the samples have sufficient 

spread and little scatter about the regression line, slopes 

of the regression may be used to calculate an average 

age. This approach avoids the spurious fractionation of 

uranium and thorium that often occurs during 

preferential leaching of the detrital component 

(Bischoff and Fitzpatrick, 1991 ). 

Two- to three m sections of core from 3 parts of 

Walker Lake core WLC84-4 (Benson, 1991 ), and 

2 sections of less than 1 m from a Pyramid Lake core, 

PLC87-2, were each divided into 10 samples weighing 

2 or 3 g. Each sample was analyzed by isotope-dilution 

alpha-spectrometry to determine activities of 234U, 

238U, 230Th, and 232Th and 234u;238u and 23orh/234u 

ratios were calculated for each segment (table 1 ). 

ABSTRACTS OF PRESENTATION 19 
Table 1. Summary of sample data and calculated ages of sections of core from Walker Lake and Pyramid Lake 

(Isotope-activity ratios with I standard deviation errors. and ages are calculated from those ratios: no age tor the 27.4-meter depth of core PLC87-2 

because errors were greater than the age: --. no data.] 

Depth Activity ratios Age 

(meters) Samples 234u1238u 230Th/234U (1ol yr B.P.) 

Core WLC84-4 

47.2 1-10 l.l70 ± 0.028 

71.6 1-10 1.278 ± .014 

95.5 1-7 1.134 ± .057 

95.5 1--10 1.228 ± .018 

Core PLC87-2 

27.4 1-10 2.100 ± .549 

58.1 1-10 1.338 ± .107 

Analyses of Section 20 of core WLC84-4 

yielded an age of 53,000 ± 7,000 yr (I cr). Analyses of 

Section 28, also from Walker Lake, yielded an age of 

80,000 ± 9,000 yr (lcr). When all 10 samples of 

Section 36 from Walker Lake were used, an age of 

I72,000 + 28,000/-23,000 yr (I cr) was calculated. The 

0.391 ± 0.044 53+7/-7 

.534± .041 80 + 9/-9 

.749± .170 144 + 96/-52 

.825 ± .052 172 +28/-23 

.960± .164 

.726± .093 130 + 34/-27 

10 

uranium concentration and 230Th activity of the bottom 

three samples of Section 36 were substantially higher 

than of the upper seven samples in the section. 

However, the three samples are from radioactive 

growth slopes similar to growth slopes of the top 

seven samples. Regardless, they have been excluded 

from the age calculations because of their vety 

different uranium concentrations. With the exclusion 

of the three samples, the calculated age becomes 

I44,000 yr and the 1-sigma error increases to +96,000/ 

-52,000 yr. Sarna-Wojcicki and others (1991) have 

estimated the age of an a~h bed near the base of core 

WLC84-4 (145m) to be 160,000 ± 25,000 yr. All ages 

estimated by U-series and tephrochronology are in 

correct stratigraphic order and seem to roughly follow 

30 ':..-Tephra-age estimation 

.. 

the trend of sedimentation rate estimated by 14C 

analyses done on sections from higher in the core 

(fig. 1 ). 

Figure 1. Age-depth plot of carbon-14 (not labeled), 

tephrochronology, and uranium-series dated segments of 

Walker Lake cores WLC84-4, WLC84-5, and WLC84-8. 

40 

50 

CJ) 

a: 60 w 

1--

w 

~ 70 

z 

:i 

I80 

~ 90 

0 

100 

120 

130 

1> Tephra-age estimation 

~ranium-series-age estimation 

+ranium-series-age estimation 

Uranium-series-age estimation 

Tephra-age estimation 

-+- 15QL-~---L--~--~--L-~---L--~--~--

o 5 10 15 20 25 

YEARS BEFORE PRESENT x 104 

20 Proceedings of the Workshop "Ongoing Paleoclimatic Studies In the Northern Great Basin," Reno, Nevada, May 1993 
The U-scries-age estimates for lake sediments 

cannot account for any discontinuities; thus, deposition 

rates calculated from the U-serics-age estitnates arc 

minitnum values. Prior to 80,000 yr B.P., the rate of 

deposition wa~ approximately 0.3 to 0.4 m/1 03 yr and 

after 80,000 yr B.P., the rate seems to have increased to 

0.9 m/103 yr(fig. 1). 

Results for the Pyramid Lake core arc mixed. 

Although isochron lines tnay be fitted to the data from 

Section 19A of core PLC87-2, there is little extension 

along the line and much scatter away from the line. A 

calculated U-series age yields errors greater than the 

age itself. Examination of the core indicated the 

presence of a buried soil in the lower one-half of the 

REFERENCES 

section that had a wave-reworked sand in the 

upper one-half, so failure of the method is not 

surprising. However, analytical results for Section 31 E 

of PLC87-2 had good extension and fit to the 

regression line and provided an age of 130,000 + 

34,000/-27,000 yr. This age would indicate a minimum 

deposition rate of 0.45 m/1 03 yr. 

This pilot study of five sections of core from 

Walker and Pyramid Lakes ha~ indicated that closed 

systems for uranium and its daughters are sometimes 

formed within limited sections of sediment. Four of 

these sections provided reasonable U-series dates when 

compared with additional parts of sections within the 

core that were dated by other methods. 

Benson, L.V., 1991, Timing of the last highstand of Lake Lahontan: Journal of Paleolimnology, v. 5, p. 115-126. 

BischotT, .T.L., and Fitzpatrick, J.A., 1991, U-series dating of impure carbonates--An isochron technique using total-sample 

dissolution: Geochemica et Cosmochemica Acta, v. 55, p. 543-554. 

Lao, Yong, and Benson, L. V., 1988, Uranium-series age estimates and paleoclimatic significance of Pleistocene tufas from 

the Lahontan Basin, California and Nevada: Quaternary Research, v. 30, p. 165-176. 

Ludwig, K.R., 1991, ISOPLOT, a plotting and regression program for radiogenic-isotope data; version 2.53: U.S. Geological 

Survey Open-File Report 91-445, 39 p. 

Sarna-Wojcicki, A.M., Lajoie, K.R., Meyer, C.E., Adam, D.P., and Rieck, H.J., 1991, Tephrochronologic correlation of upper 

Neogene sediments along the Pacific margin, conterminous United States, in Morrison, R.B., ed., Quaternary nonglacial 

geology--Conterminous U.S.: Boulder, Colo., Geological Society of America, The Geology of North America, v. K-2, 

p. 117-140. 

Yang, I. C., 1989, Climatic changes inferred from analyses of lake-sediment cores, Walker Lake, Nevada: U.S. Geological 

Survey Water-Resources Investigations Report 89-4006, 15 p. 

ABSTRACTS OF PRESENTATION 21 

Application of Magnetic Susceptibility and Grain Size in a 

Lithostratigraphic Study of Middle to Late Pleistocene Lacustrine 

Sediments Near Summer Lake, Oregon 

Daniel B. Erbes and Robert M. Negrini, Department o.f Physics and Geology, 

California State University, Bakersfield 

Positive results for intrabasinal correlation of 

outcrop and core from a lacustrine sequence of the 

Great Basin sites have been obtained using volume 

magnetic susceptibility and sedimentological data. 

The known sedimentary record from pluvial Lake 

Chewaucan in south-central Oregon contains more 

than 70 laterally continuous and distinct tephra layers, 

which enable high-resolution intrabasinal correlation 

of outcrop and core. This phenomenon has enabled 

testing of the effectiveness of volume magneticsusceptibility data and sedimentological records as 

correlation tools. Preliminary results from this study 

indicate that magnetic-susceptibility records can be 

correlated throughout the entire sampled interval to 

within a few centimeters of stratigraphic depth between 

outcrops separated by 1 km. Similar results have been 

obtained correlating laterally distinct sands, pebble 

lags, and carbonate layers. Grain-size data are being 

collected using standard pipette and sedigraph methods 

to investigate their relation to these correlations. 

ABSTRACTS OF PRESENTATION 23 

Paleoclimatic Implications of Late Quaternary Lake-Level 

Variations in South-Central Oregon 

Dorothy E. Freidel, Department of Geography, University o.f Oregon 

Lake-level chronologies of three paleo lakes in 

south-central Oregon indicated that these lakes reached 

their most recent highstands between 18,000 and 

17,000yr B.P., 3,000 to 4,000 yr earlier than the highest 

levels attained by Lakes Bonneville and Lahontan to 

the south. This study tests several climate scenarios 

that could have caused the lakes to rise to their highest 

levels at 18,000 yr B.P. 

Paleobotanical data indicated that, at 

18,000 yr B.P., conditions in the Pacific Northwest 

were colder and drier than at present (1993) 

(Thompson and others, in press; Barnosky and others, 

1987; Barnosky 1985), while in the northern Great 

Basin, colder and somewhat moister conditions 

prevailed (Thompson and others, in press; Thompson, 

1990). Few data have been collected for the area 

between these two regions where the Oregon lakes 

were located. However, based on estimates from these 

studies, air temperatures in south-central Oregon at 

18,000 yr B.P. were about 7°C lower than at present. 

Lake-ice simulations have indicated that a 

7°C decrease in mean annual air temperature could 

have caused the paleolakes in Nevada to be ice 

covered during the winter months, accompanied by a 

60-percent reduction in evaporation rates during that 

period (Hostetler, 1991 ). Water-balance modeling of 

the Oregon paleo lakes indicates that they respond 

substantially to such a decrease in evaporation. 

General atmospheric-circulation simulations 

have indicated that the mean position of the jet stream 

over western North America ha~ shifted in response to 

changes in the large-scale controls of climate during 

the past 18,000 yr (Kutzbach and Guetter, 1986). 

Although coarse in resolution, the simulations indicate 

that, at 18,000 yr B.P., the mean winter position of the 

jet-stream core was at about the latitude of southern 

California, and the summer position intercepted the 

West Coast at about mid-Oregon. These atmospheric 

patterns would have brought south-central Oregon 

cold, dry winters; and cool, cloudy summers; and 

some increase in summer precipitation. 

Thompson and others (in press) produced 

estimates of surface temperature, precipitation, and 

effective moisture anomalies for six regions of western 

North America, based on comparison of compiled 

paleoenvironmental data with simulations of a general 

atmospheric circulation model. The boundary between 

the northwestern and western regions of North 

America bisects Oregon, yet the model boundaries 

between climatic regions are too coarse to be 

interpreted precisely. At 18,000 yr B.P., the southcentral Oregon paleo lakes could have been affected by 

the cold, dry, glacial anticyclone prevalent in the 

Northwest in winter, and the cool, moist, westerly 

circulation of the Great Basin (in the western region) in 

summer (Thompson and others, in press). The Oregon 

paleo lakes seem to have been in a transition zone 

between the two atmospheric regimes. 

Several climate scenarios for the Oregon 

paleo lakes were tested using a water-balance model. 

One scenario wa~ based on Hostetler and Benson's 

( 1990) hypothesis that historic precipitation and 

runoff maxima, plus evaporation, when decreased to 

58 percent of present, were sufficient to cause Lake 

Lahontan to rise to its pre-highstand level. This 

scenario, using Oregon maxima ( 1.6 times present 

precipitation, 2.4 times present inflow) and 58 percent 

of present evaporation, caused the Oregon paleo lakes 

to reach and maintain levels approximating their 

highstand shorelines. 

A second set of scenarios based on Cooperative 

Holocene Mapping Program (COHMAP) simulations 

(COHMAP members, 1993; Thompson and others, in 

press) tests whether the Oregon highstands could have 

developed under the cold, dry conditions of the Pacific 

Northwest at 18,000 yr B.P. In these simulations, 

precipitation was decreased by 10 to 20 percent of 

present, evaporation was decreased by 50 percent 

[based on evaporation rates from Hostetler's ( 1991) 

lake ice-cover modeling], and runoff was estimated 

using Mifflin and Wheat's (1979) modifications of 

Langbein and others (1949) and Schumm's (1965) 

runoff curves, which were based on temperature and 

precipitation. One scenario, using 95 percent of 

present precipitation, 50 percent of present 

evaporation, 7°C colder than present temperature, and 

ABSTRACTS OF PRESENTATION 25 
3.35 times present runoff, also comes close to 

simulating highstand levels in the three Oregon basins. 

The runoff curves produced very rough estimates, and 

it is not known how accurately runoff was represented 

by these curves at low temperatures and low levels of 

precipitation. Comparison with maps of modern 

temperature, precipitation, and runoff distributions 

indicated that the combination of conditions 

represented in the second set of scenarios does not 

occur in modern environments. The level of runoff at 

3.35 times present appears to be unrealistically high. 

Of the two scenarios that produce high lake levels, the 

scenario in which precipitation is increased seems 

more realistic. 

In conclusion, paleoenvironmental data and 

climate modeling for the Pacific Northwest and the 

Great Basin and water-balancing modeling of three 

paleolakes in south-central Oregon indicated that, at 

18,000 yr. B.P., cold, slightly moister than present 

climatic conditions caused the lakes to rise to their 

REFERENCES 

most recent highstands. The water-balance model 

scenarios that simulated conditions colder and drier 

than present could not simulate the highstand lake 

levels without using unrealistically high rates ofinflow. 

The scenarios that simulated very cold conditions with 

no change in precipitation relative to present also 

required inflow rates that were quite high but within a 

plausible range. The modeling results are consistent 

with the hypothesis that at 18,000 yr B.P., south-central 

Oregon was within a transition zone between the very 

cold, dry glacial anticyclone to the north and the cold, 

moist, westerly circulation to the south. Cold winters, 

in which precipitation was somewhat lower than or the 

same as the present, and cool, cloudy summers, in 

which precipitation was higher than at present, were 

sufficient to cause the Oregon paleo lakes to rise to their 

highest late Quaternary levels. 

Barnosky, C.W., 1985, Late Quaternary vegetation in the southwestern Columbia Basin, Washington: Quaternary Research, 

v. 23, p. 109-122. 

Barnosky, C.W., Anderson, P.M., and Bartlein, P.J., 1987, The northwestern U.S. during glaciation; vegetational history 

and paleoclimatic implications, in Ruddiman, W.F., and Wright, H.E., Jr., eds., North America and adjacent oceans 

during the last deglaciation: Boulder, Colo., Geological Society of America, The Geology of North America, v. K-3, 

p. 289-321. 

COHMAP [Cooperative Holocene Mapping Project] members, 1993, Global climates since the last Glacial Maximum: 

Minneapolis, University of Minnesota Press, p. 569. 

Hostetler, S. W., 1991, Simulation oflake ice and its effect on the late-Pleistocene evaporation rate of Lake Lahontan: Climate 

Dynamics,v.6,no. 1,p.43-48. 

Hostetler, S.W., and Benson, L.V., 1990, Paleoclimatic implications ofthe highstand of Lake Lahontan derived from models 

of evaporation and lake level: Climate Dynamics, v. 4, no. 3, p. 207-217. 

Kutzbach, J.E., and Guetter, P.J., 1986, The influence of changing orbital parameters and surface boundary conditions on 

climate simulations for the past 18,000 years: Journal ofthe Atmospheric Sciences, v. 43, no. 16, p. 1726-1759. 

Langbein, W.B., and others, 1949, Annual runotf in the United States: U.S. Geological Survey Circular 52, 14 p. 

Mifflin, M.D., and Wheat, M.M., 1979, Pluvial lakes and estimated pluvial climates of Nevada: Nevada Bureau of Mines 

and Geology Bulletin 94, 57 p. 

Schumm, S.A., 1965, Quaternary paleohydrology, in Wright, H.E., Jr., and Grey, D.G., eds., The Quaternary of the 

United States: Princeton, Princeton University Press, p. 783-794. 

26 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Thompson, R.S., 1990, Late Quaternary vegetation and climate in the Great Basin, chap. 10 ofBetancourt, J.L., 

VanDevender, T.R., and Martin, P.S., cds., Packrat middenr-The last 40,000 years of biotic change: Tucson, 

University of Arizona Press, p. 200--239. 

Thompson, R.S., Bartlein, P.J., Whitlock, C., Harrison, S.P., and Spaulding, W.G., in press, Climatic changes in the 

Western United States since 18,000 years B.P., in Wright, H.E., Jr., Kutzbach, J.E., Webb, T., III, Ruddimann, W.E., 

Street-Perrott, F.A., and Bartlein, P.J., eds., Global climates since the last glacial maximum: Minneapolis, University of 

Minnesota Press, 569 p. 

ABSTRACTS OF PRESENTATIONS 27 

Paleomagnetism of Owens Lake SedimentsConstraints on the Timing of Climate Fluctuations 

in the Quaternary 

Jonathan M. Glen, Robert S. Coe, and Shannon S. Baughn, 

Institute of Tectonics and Earth Sciences Department, University o.f Cal(fornia, Santa Cruz 

George I. Smith, U.S. Geological Survey 

Rock and paleomagnetic studies on three cores 

obtained from Owens Lake, California, by the 

U.S. Geological Survey to investigate late Pleistocene 

climate in the Western United States are described. 

Owens Lake, locatedjusteastofthe Sierra Nevada, has 

probably received drainage (and accumulated 

sediments) by way of the Owens River and from 

local runoff from the Sierra Nevada for more than 

3,000,000 yr. 

The three cores, combined as a c01nposite, span 

the top 323 m of lake fill consisting mostly of fine- to 

medium-grained sediments deposited during the past 

800,000 yr. The cores, therefore, have the potential of 

providing excellent records of climate and 

paleomagnetic field changes within the Quaternary. 

Paleomagnetic and rock magnetic studies 

are continuing on a suite of more than 500 discrete 

samples obtained from the cotnposite section to 

provide magnetostratigraphy and to study in detail 

the Matuyama/Brunhes (M/B) transition and withinBrunhes excursions and secular variation (SV). 

Because the cores were rotary drilled, individual 

core segments were rotated, resulting in a loss of 

absolute declinations. Therefore, field behavior was 

primarily interpreted on the basis of inclination, with 

additional aid from natural-remanent-magnetization 

(NRM) intensity and reconstructed declination data. In 

addition to determining the remanence directions, low 

field magnetic-susceptibility (MS) measurements were 

made. 

NRM intensities of the samples varied by three 

orders of magnitude (10-7 to Io-4 emu/cm3), the bulk 

of the range being due to variations in susceptibility, 

with a large fraction of sample NRM's being in the 

mid-10-7 range. Susceptibility (MS) depends on the 

amount and mineralogy of magnetic material present in 

a sample. These factors were potentially controlled 

(through a variety of mechanisms) by climate 

conditions. Therefore, variations in MS may be a 

proxy for climate change. The remanent 

magnetization, however, depends on the intensity of 

the Earth's magnetic field in addition to the 

concentration and types of magnetic grains in the 

sample. A first-order estimate of relative 

paleointensity of the magnetic field was, therefore, 

obtained by normalizing the NRM's to- MS. 

Results from the inclination record indicated the 

presence of several low inclination excursions (or 

possibly short polarity events) within the Brunhes and 

a 3-m section of transitional directions, interpreted as 

the M/B reversal, at the base of the composite core. 

Recent 40 Ar/39 Ar dates yield an age of783,000 yr B.P. 

for the reversal. The depth and age of the reversal yield 

an average sedimentation rate of 40 cm/1,000 yr. 

Shallow inclination anomalies seem to be a 

common feature within the Brunhes polarity 

chronology. These features may indicate global field 

excursions or short or aborted reversals. If so, they 

should correlate with features seen at globally 

distributed sites. With this in mind, the features 

identified in the Owens Lake cores were compared 

with those seen in other records. Because more events 

are contained in the Owens core than are present in the 

other records and because of the range of estimated 

excursion ages, unique correlations are difficult to 

establish. 

A refinement of the correlations currently being 

made will be needed to establish the details (in 

direction and intensity) of the excursions. Even if such 

features are not global, regional records (within 

distances of 3,000 km) should be correlative. For this 

reason, events at sites in the Western United States [for 

example, the Mono Lake (28,000 yr B.P.) and Pringle 

Falls (150,000 yr B.P.) excursions] are of particular 

interest. 

ABSTRACTS OF PRESENTATION 29 

Prehistoric Human Occupation and Changing Lake Levels at 

Pyramid and Winnemucca Lakes, Nevada 

Eugene M. Hattori, Nevada Historic Preservation Qffice and 

The Cal(fornia Academy of Sciences 

Donald R. Tuohy, Nevada State Museum 

Radiocarbon dates from Pyramid Lake and 

Winnemucca Lake archaeological sites in Nevada 

provide evidence for shifts in Holocene lake levels 

(table I, fig. I). Winnemucca Lake is especially 

sensitive to inflow variation because of its broad, 

shallow lakebed and the bedrock-controlled sill for its 

feeder channel, the Mud Lake Slough. In the past, 

Winnemucca Lake received water only when the 

Truckee River or Pyramid Lake rose above the slough's 

I, 177-m sill elevation. Prehistoric occupation or 

activity sites below the I, 177-m threshold elevation at 

Pyramid Lake most likely indicates that Winnemucca 

Lake was receiving no inflow and, in fact, that a playa 

had replaced the easily desiccated, shallow lake. 

(f) 

UJ 

11 

10 

9 

_J 8 0... 

~ 7 (f) 

~ 6 

ffi 5 cc 

:2: 4 ::> 

z 3 

2 

0 

D Pyramid Lake Basin 

I Winnemucca Lake Basin 

0 1 2 3 4 5 6 7 8 9 10 11 

RADIOCARBON AGE, IN 103 YEARS BEFORE PRESENT 

Figure 1. Radiocarbon ages of human occupation in the 

Pyramid and Winnemucca Lake areas. 

Although more than I ,000 archaeological sites 

are located in the Pyramid Lake and Winnemucca Lake 

Basins, human occupation of the principal 

Winnemucca Lake sites are particularly sensitive to 

changing lake levels. The Falcon Hill and the East 

Shore archaeological areas at the northern end of the 

Winnemucca Lake Basin are several kilometers from 

springs and even some distance from the playa surface. 

Use of these sites wa<; dependent on a water body 

existing in the basin. The contents of these sites also 

demonstrated the occupants' dependence on marsh and 

lake resources for sustenance and for raw materials for 

tools. All dates are presented as 14C yr B.P. 

The earliest radiocarbon dated artifact was a 

9,660 ± 170 yr B.P. (laboratory number GX-13744) 

date on fishing line recovered near the Pinnacles at 

Pyramid Lake (table I). At Winnemucca Lake, 

open-twined basketry from a shelter at Shinners 

Site-A (26Wa198) was dated to 9,540 ± 120 yr B.P. 

(UCLA-675). Following these dates, there are no 

cultural dates between 9,500 and 8,400 yr B.P. Then, a 

series of three dates spans the interval between 

8,380 ± 120 (UCLA-672) and 7,830 ± 350 yr B.P. 

(laboratory number L-289) (table 1). During each of 

these dated occupations, Pyramid Lake was most likely 

above the threshold elevation, and Winnemucca Lake 

held water. Artifacts associated with these early 

Holocene dates include an atl-atl; edge-ground, 

stemmed projectile points; barbed bone points; plaintwined basketry; Great Basin crescents; and fish 

netting. 

Between 7,800 and 4,100 yr B.P., there are only 

six dates. Although people inhabited the area during 

this interval, conditions apparently were not conducive 

to intensive site use within the Pyramid and 

Winnemucca Lake Basins. The 1, 153-m elevation for 

the mano dated to 4,600 ± 60 yr B.P. (laboratory 

number LL-CM-26A2l) from Pyramid Lake is 

accepted with caution because the mano is small and 

portable. Between 4,100 and 3,200 yr B.P., 13 dates 

ABSTRACTS OF PRESENTATION 31 
indicate an interval of increased intensity of occupation 

and increased use of the marsh and lacustrine resources 

of Winnemucca Lake. This occupation is marked by 

increased development of Inaterial culture and 

increased contact with prehistoric cultures in coastal 

and central California. Marine shell ornaments, 

decorated plain-twined basketry, Humboldt and 

Gatecliff (Pinto )-type projectile points, western pond 

turtle-shell ornaments, and juniper seed beads are 

characteristic artifacts. In addition to turtles, the 

Winnemucca Lake Basin also supported populations of 

water birds, cutthroat trout, cui-ui, and marmotanimals no longer present in this lake basin. Coiled 

basketry containers also make their first appearance 

during this interval. 

Lowered lake levels probably occurred between 

about 3,300 and 2,600 yr B.P given the limited number 

of archaeological sites that date to this interval 

(table 1 ). A brief interval between 2,600 and 

2,400 yr B.P. yielded six dates; one of these was of 

particular interest. Two burials from a I, 154-m beach 

were dated at 2,480 ± 120 yr B.P. (laboratory number 

GaK-2386) from an associated piece of sagebrush 

(Artemisia tridentata) (table 1 ). This age, associated 

with a very low Pyramid Lake level, is similar to dates 

on basketry from lake-dependent sites at the extreme 

northern end of the Winnemucca Lake Basin. This 

potential discrepancy of a depressed Pyramid Lake 

level and an elevated Winnemucca Lake level may be 

due to the occurrence of a mesic interval that was 

punctuated by a rather severe drought or to diversion 

of the Truckee River solely to the Winnemucca Lake 

Basin. During this interval, between 2,600 and 

2,400 yr B.P., coiled basketry greatly increased in 

frequency; twining, however, still persisted. 

After an interval of some 400 yr between about 

2,400 and 2,000 yr B.P. (with only two dates around 

2,150 yr B.P. ), there is a 900-yr interval between 2,000 

and I, I 00 yr B.P. that had 14 dates from I 0 

Winnemucca Lake and Pyramid Lake archaeological 

sites. A lake, or 1narsh, or both, was present in the 

Winnemucca Lake Basin, and Pyramid Lake seems to 

have been above the 1, 177-m threshold elevation for 

most of this time. During this late Holocene interval, 

Lovelock wickerware plaiting, the hallmark of the 

Lovelock Culture, appeared. The other basketry 

technologies, plain-twining and coiling, still persisted. 

Projectile point styles included the Elko-type points. 

California trade items, especially marine shell 

ornaments, again appeared in large quantities. 

The last I, 100 yr are represented by nine dates 

and by generally depressed lake levels. A cluster of 

four dates between 600 and 400 yr B.P. indicated the 

presence of water in Winnemucca Lake at that time. 

Lovelock wickerware, twining, and coiling persisted. 

At 400 yr B.P., a major change in basketry 

technology appeared. A twill-twined water bottle from 

Pyramid Lake dates to 380 ± 100 yr B.P. (laboratory 

number GaK-2385) (table 1). This basket-weaving 

technique is ethnographically associated with the 

Northern Paiute Indians, the modern inhabitants of the 

area. This find was the first recognized appearance of 

the group in the local archaeological record. Other 

Pyramid Lake dates also associated with the Northern 

Paiutes include a 290 ± 90 yr B.P. (laboratory number 

WSU-1960) date on a house floor (Smithsonian 

number 26Wa1014-l) and, from the same site, a 

240 ± 100 yr B.P. (laboratory number GaK-2389) 

date on an arrowshaft tipped with a desert-sidenotched-type projectile point (table 1). There are no 

post-380 yr B.P. dates from the Winnemucca Lake 

Basin, although historic artifacts and ethnographies 

indicate that the basin continued to be occupied by the 

Northern Paiute, but possibly with reduced intensity. 

When J.C. Fremont entered the region in 1844, 

Winnemucca Lake may have been dry, and Pyramid 

Lake stood at the Mud Lake Slough threshold elevation 

of 1,177 m, which was probably the beginning of the 

historic highstand. By the 1880's, Winnemucca Lake 

reached its maximum depth of 26 m; lacustrine biota 

had recovered enough to support a Chinese fishing 

camp along the western shore of the lake. A lake and 

marsh persisted in the Winnemucca Lake Basin until 

the historic water diversions of the 1900's. 

32 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
'"'~ble 1. Radiocarbon dates for archaeological materials from Pyramid Lake and Winnemucca Lake 

Lake Carbon-14 age Laboratory Site Specimen dated number {Smithsonian number) 

Pyramid 240± 100 

GaK-2389 Marble Bluff Dam (26Wa1014-l) Arrow w/desert-sidenotched point 

Pyramid 290±90 WSU-1960 Marble BlutTDam (26Wal014-l) House floor (Paiute?) 

Pyramid 380± 100 GaK-2385 Water Bottle Cave (26Wa372c) Twill-twined basketry 

Winnemucca 390± 80 UCLA-982 Shinners Site-1 (26Wa205) Grass w /burial 

Winnemucca 400± 80 UCLA-985 Shinners Site-1 (26Wa205) Basketry 

Winnemucca 580± 100 UCLA-677 Shinners Site-F (26Wa202) Basketry 

Winnemucca 595 ± 80 UCLA-986 Shinners Site-A (26Wa198) Matting 

Pyramid 620± 80 GaK-2810 Warrior Pt. Cave (26Wa729T) Basketry 

Pyramid 860± 90 SI-3430 Firepit III (26Wa1 020) Carbon 

Winnemucca 1,150 ± 100 UCLA-668 Shinners Site-1 (26Wa205) Basketry 

Winnemucca 1,190 ± 80 UCLA-673 Shinners Site-A (26Wa198) Basketry 

Winnemucca 1,240± 80 UCLA-906 Shinners Site-C (26Wa200) Basketry 

Pyramid 1,275 ± 160 La-73-113 Mixon Cave (26Wa528) Digging stick 

Pyramid 1,340± 100 GaK-2809 Mule Ears Cave (26Wa528) Basketry 

Winnemucca 1.400 ± 150 WSU-269 Empire Cave (26Wa 197) Basketry 

Winnemucca 1.480 ± 155 WSU-268 Empire Cave (26Wa 197) Basketry 

Winnemucca 1.510±200 M-346 Crypt Cave (26Pe3a) Fur robe 

Winnemucca 1,610 ± 80 UCLA-671 Empire Cave (26Wa 197) Basketry 

Pyramid 1,660 ± 60 LL-289B9 Pinnacles Beach (26Wa218B) Tufa on percussor ( 1 , 1 79 m) 

Winnemucca 1,725 ± 120 UCLA-933 Shinners Site-A (26Wa198) Basketry 

Pyramid 1,820 ± 180 1-2846 Marble Bluff Dam (26Wa1016) Bone collagen 

Winnemucca 1,860± 70 UCLA-124 Shinners Site-C (26Wa200) Basketry 

Pyramid 1,950± 100 GaK-2804 Desiccation Cave (26Wa291) Matting 

Pyramid 2,140 ± 110 GaK-2390 Mogoose Cave (26Wa275) Basketry 

Winnemucca 2,175 ± 80 UCLA-904 Shinners Site-A (26Wa198) Basketry 

Winnemucca 2.400± 200 L-289 II Crypt Cave (26Pe3a) Basketry 

Pyramid 2.410 ± 90 GaK-3361 Blazing Star Cave (26Wa275) Basketry 

Pyramid 2.430 ± 100 GaK-2388 Mogoose Cave (26Wa275) Basketry 

Winnemucca 2,440± 100 UCLA-674 Shinners Site-C(26Wa200) Basketry 

Pyramid 2.480 ± 120 GaK-2386 Burial site (26Wa404) Sagebrush 

Winnemucca 2,590± 80 UCLA-692 Chimney Cave (26Pe3b) Juniper bark mat 

Pyramid 3,040 ± 115 SI-3429 Pit House & Burials (26Wa1016) Carbon 

Pyramid 3,270± 180 GaK-2805 Coiled Jug Cave (26Wa315) Basketry 

Winnemucca 3,325± 90 UCLA-931 Shinners Site-F (26Wa202) Basketry 

Winnemucca 3,620± 80 UCLA-976 Kramer Cave (26Wa196) Basketry 

ABSTRACTS OF PRESENTATIONS 33 
Table 1. Pyramid Lake and Winnemucca Lake, radiocarbon dates from archaeological materials-Continued 

Lake Carbon-14 age Laboratory Site Specimen dated number (Smithsonian number) 

Winnemucca 3,660± 80 UCLA-905 Kramer Cave (26Wa196) Basketry 

Winnemucca 3,660± 100 UCLA-979 Kramer Cave (26Wa 196) Basketry 

Winnemucca 3,700± 80 UCLA-984 Kramer Cave (26Wa196) Basketry 

Winnemucca 3,720 ± 100 UCLA-122 Kramer Cave (26Wa196) Dart foreshaft 

Winnemucca 3,745 ±90 UCLA-932 Kramer Cave (26Wa196) Basketry 

Winnemucca 3,760± 80 UCLA-980 Kramer Cave (26Wa196) Basketry 

Winnemucca 3,830± 110 GaK-2387 Kramer Cave (26Wa196) Dart foreshaft 

Winnemucca 3,850± 100 UCLA-983 Kramer Cave (26Wa 196) Matting 

Winnemucca 3,900± 100 UCLA-670 Kramer Cave (26Wa196) Basketry 

Winnemucca 4,030± 85 UCLA-978 Shinners Site-C (26Wa200) Cordage 

Pyramid 4.470 ±I 10 GaK-2808 Blazing Star Cave (26Wa525) Digging sticks 

Pyramid 4,600± 60 LL-CM-26A21 Wizard's Beach Tura·on mano (elev 1,153 m) 

Winnemucca 5,100± 150 WSU-270 Shinners Site-D (26Wa20 1) Matting 

Winnemucca 5,670± 150 L-289 FF Cowbone Cave (26Pe3c) Juniper bark mat 

Winnemucca 6,500 ± 150 L-596 Guano Cave (26Pe3d) Occupation floor detritis 

Winnemucca 6,730± 90 UCLA-981 Shinners Site-1 (26Wa205) Grass in cache pit 

Winnemucca 7,830 ± 350 L-289 Fish bone Cave (26Pe3e) Fish netting 

Winnemucca 7,980 ± 610 1-6873 Nicolarsen Site (NV-Wa-197) Basketry 

Winnemucca 8,380± 120 UCLA-672 Shinners Site-A (26Wa198) Matting 

Winnemucca 9,540± 120 UCLA-675 Shinners Site-A (26Wa198) Basketry 

Pyramid 9,660± 170 GX-13744 Pinnacles Area (26Wa217A) Fishing line 

34 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
High-Resolution Simulations of Climate of the 

Western United States at 18,000 Years B.P. 

Steve W Hostetler, U.S. Geological Survey, 

F Giorgi and Gary T. Bates, National Center.for Atmospheric Research, and 

Patrick J. Bartlein, Department o.f Geography, University o.f Oregon 

Simulations of perpetual January and July 

climate at 18,000 yr B.P. over the Western United 

States have been conducted using a high-resolution 

(mesoscale) atmospheric model (RegCM). The 

RegCM, the climate version of theN CARJPsumesoscale model MM4, was run using a grid spacing 

of 60 km, a resolution that captures regional 

atmospheric circulations and terrestrial features (such 

as coastlines, mountains, and lakes) that exert strong 

forcings on the climate of the West. The model 

includes a surface-physics package (Biosphere 

Atmosphere Transfer Scheme) that couples the 

biosphere with the atmosphere and includes a fully 

interactive lake model to simulate lake-atmosphere 

feedbacks associated with Lakes Bonneville and 

Lahontan. 

A series of 90-day, 18,000-yr- and 0-yr-B.P. 

simulations were conducted to make estimates of the 

general climate and of the effect of feedbacks between 

the lakes and the atmosphere. Initial and lateral 

boundary conditions (sea surface temperatures and 

vertical profiles of temperature, humidity, and wind 

velocity) for the simulations were obtained from output 

from the paleosimulations of Kutzbach and Guetter 

REFERENCE 

( 1986). The surface of RegCM included estimated 

distributions of vegetation, montane glaciers, the 

continental ice sheet, and the areas and depths of 

Lakes Bonneville and Lahontan at 18,000 yr B.P. 

Results indicate that throughout the West, 

January air temperatures at 18,000 yr B.P. were about 

2°C colder than the 0-yr-B.P. control, whereas July 

temperatures were more than 5°C colder than the 

0-yr-B.P. July control run. January precipitation 

throughout the region was substantially greater at 

18,000 yr B.P. However, July precipitation at 

18,000 yr B.P. was not much different than that at 

0 yr B.P., except around Lakes Bonneville and 

Lahontan. 

Analyses indicate that the hydrologic signal 

associated with the position and strength of the jet 

stream at 18,000 yr B.P. dominates the hydrologic 

budgets of the Bonneville and Lahontan Basins. 

Over the Bonneville Basin, lake-effect precipitation 

was a substantial component of the hydrologic budget 

in January and July of 18,000 yr B.P. However, such 

feedbacks were minor components of the hydrologic 

budget of Lake Lahontan. 

Kutzbach, J.E., and Guetter, P.J., 1986, The influence of changing orbital parameters and surface boundary conditions on 

climate simulations for the past 18,000 years: Journal of Atmospheric Science, v. 43, p. 1726-1790. 

ABSTRACTS OF PRESENTATION 35 

Initial Results from Paleoclimatic and Geophysical Studies of 

Washoe Lake, Nevada 

Robert E. Karlin, James T Trexler, and Ronald Petersen, 

Department of Geological Sciences, Mackay School o.f Mines, University o.f Nevada-Reno 

A lacustrine sediment sequence from Washoe 

Lake in western Nevada was cored in 1992 for 

paleoclimatic and paleohydrologic studies. In late 

June 1991, the lake desiccated for the first time since 

1933-34 and for only the second time in recorded 

history, offering a rare opportunity to obtain long 

continuous sections from a quasi-permanent lake in a 

climatically sensitive region. 

Washoe Lake, located between Carson City and 

Reno, Nevada, is in the high-Sierran semiarid desert 

environment near the present boundary between the 

pinyon pine/mountain mahogany and the sagebrush 

ecotomes. In late spring 1993, the lake was 

approximately 31 km2 in area and averaged 3 to 4 m in 

depth. During the Pleistocene, the water depth was 

about 13 to 17 m, and the lake occupied a much more 

extensive area, as evidenced by strand lines above the 

lake margins. Geologic studies of the basin sides 

indicated that lacustrine sediments have been deposited 

for at least the last 2,500,000 yr. 

Gravity, magnetic, and electrical surveys were 

conducted to characterize the geometry and subsurface 

structure of the ba.'iin. The lake is in an asymmetric 

fault-bounded half graben surrounded by the Carson 

and Virginia Ranges, the Truckee Meadows, and the 

Carson Basin. Gravity modeling of the basin indicates 

that the lake is underlain by sediment thicknesses of 

almost 600 m; maximum· accumulations are in the 

western end. A major change in sedimentary facies 

from coarse alluvial sands in the west to fine-grained 

lacustrine sediments in the east coincides with a deep 

basement offset identified from magnetic anomaly 

modeling. The deepest part of the present ( 1993) lake 

also is east of the zone of thickest sediment 

accumulation. These relations indicate that ancient and 

modern sedimentation patterns in the lake were and are 

tectonically controlled. 

Two sites on the dry lake bed were cored to 

25 m, and undisturbed sediments were obtained, 

resulting in 85-percent recovery. Two other sites 

yielded about 13 m of section until penetration was 

terminated because of fluidized sands. In addition, 

two 4-m trenches were sampled to obtain recent 

sedimentation history. The drill holes were 

geophysically logged to allow the sections to be 

reoriented in situ. Magnetic-susceptibility profiles of 

all sections were measured to characterize the 

stratigraphy of the lake. To date, sediment chemistry, 

textural analyses, and X-ray diffraction have been 

performed on sediments from the core site and on 

sediments from one trench. 

Near the depositional center of the lake basin, 

the top 12m of sediment consists of alternating 

intervals of lake sediments, peaty-bog deposits, and 

soils. The lower part of the drill core contains mostly 

lake sediments probably deposited within the last 

60,000 yr. The lake sediments are characterized by 

elevated CaC03 concentrations, low susceptibilities, 

and relatively low abundances of terrigenous elements, 

such as AI, K, and Na, which are usually associated 

with detrital aluminosilicates. The carbonate minerals 

are calcite and aragonite that were authigenically 

precipitated during alkaline and probably saline lake 

stages. The soils show an inverse relation ofCaC03 to 

terrigenous elemental abundances. Peaty intervals 

show relatively high organic carbon, low CaC03, and 

intermediate Al20 3 concentrations. 

Magnetic-susceptibility profiles provided a 

sensitive, continuous record of lithologic change. 

Susceptibility maxima mostly indicated intermittent 

sand layers that were deposited in different 

environments. Textural variations were used to map 

transport pathways and depositional environments. 

Sands present in different depth intervals were derived 

from turbidites and subaerial sheet-flow deposits that 

formed during lake stages. Discontinuous channelized 

fluvial sands were deposited during the peaty-bog 

stages, and deflationary lag deposits formed during 

arid-soil stages. 

The sediment record indicated that climate 

varied substantially during the Holocene. The top 3m 

of sediment contained several silt/clay layers, some of 

ABSTRACTS OF PRESENTATION 37 
which contained clam zones and peaty zones and soils, 

indicating that the lake had partially desiccated several 

times during the Holocene. Radiocarbon dating of 

three clam layers in the top I m and the presence of the 

Mount Mazama ash allowed calculation of 

sedimentation rates of23 cm/103 yr fr01n 2,600 to 

0 yr B.P. and 11 cm/1 02 yr from 6,850 to 2,600 yr B.P. 

In the last 2,600 yr, the climate in the study area has 

been relatively wet, and Washoe Lake has been fully 

developed, except for three brief desiccation episodes. 

Earlier in the Holocene, the climate was generally drier 

and more variable, causing deposition of soils and 

marshy peat horizons. The results from Washoe Lake 

are consistent with a warm period from about 6,000 to 

4,000 yr ago that apparently dropped the level of Lake 

Tahoe I 0 to 20 m (Rose and Lindstrom, this volume). 

Further radiocarbon dating of lake, peat, and soil zones 

would enable determination of the timing, frequency, 

and duration of previous episodes of drought. 

38 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Detailed Sedimentary Record of Changes in the Level of 

Lake Lahontan from the Hot Springs Mountains, Nevada 

Nicholas Lancaster, Quaternary Sciences Center, Desert Research Institute 

Understanding the nature of late Pleistocene 

lake-level fluctuations requires detailed stratigraphic 

and sedimentological studies of cores and of exposed 

sections of lacustrine sediments. Initial results from 

investigations of nearshore lacustrine and eolian 

sediments from the Hot Springs Mountains, Nevada, 

are described in this abstract. 

A series of sand ramps (coalesced climbing 

dunes) of late Holocene age cover the western flanks of 

the Hot Springs Mountains, located about 20 km east of 

Fernley, Nevada. In places, the eolian deposits have 

been trenched by ephemeral streams to expose the 

underlying beach, lacustrine, colluvial, and eolian 

deposits that were laid down at or near the shoreline of 

Lake Lahontan. These deposits could provide a 

detailed record of lake-level changes and associated 

depositional environments. 

Investigations of the best exposure indicated the 

following sequence of deposits. Unit I forms the base 

of the exposed section and consists of rounded beach 

gravels, cobbles, and boulders that fine upward to fine 

gravels and shelly sands. Unit I thickens shoreward 

from 2.5 to about 9 m and is capped by a 20- to 50-cm 

boulder colluvium that has thick desert varnish on the 

clasts. Unit II, which is as much as 20m thick, is a 

series of horizontally bedded, very fine sands to silty 

sands and occasional thin silt layers. In the lower 10 m 

of the unit, there are two thin fluvial subunits 

containing reworked tufa and beach gravels. Unit III 

overlies Unit II at an erosional contact and consists of 

a set of large-scale eolian cross beds. 

A preliminary interpretation of the sequence of 

deposits is that Unit I represents a high-energy beach 

deposited in a transgression of Lake Lahontan to an 

elevation of 1,277 m. The lake then fell to less than 

1,260 m, allowing colluvium to extend over the eroded 

surface of the beach deposits. A renewed transgression 

to an elevation of at least 1,293 m deposited Unit II as 

a series of nearshore sands. Following deposition of 

Unit II, the lake fell again to some lower elevation, 

causing a brief hiatus in sediment deposition around 

1,272 m. There was extensive subaerial erosion and 

gullying of the lacustrine deposits prior to deposition of 

the eolian sands of Unit III. 

Age control of the deposits is currently ( 1993) 

poor. Unit I and the lower part of Unit II contain 

abundant small gastropod shells. Samples 

submitted for radiocarbon dating provided an age of 

12,660 ± 80 yr B.P. for Unit I and an age range between 

11,920 ± 110 to 12,780 ± 90 yr B.P. for Unit II. The 

dates for Unit II are not in stratigraphic order and seem 

to be inconsistent with other data from the Lahontan 

Basin, which indicated that lake levels were below 

1,250 m around 11,000 yr B.P. Contamination of the 

shell material is, therefore, suspected. A speculative 

correlation with other areas indicated that the 

horizontally bedded lacustrine deposits represented the 

latest Schoo transgression, dated elsewhere to be 

around 13,000 yr B.P. 

The Hot Springs Mountains also have an 

extensive series of wave-cut benches and other 

shoreline features. Eight shorelines at elevations 

between 1,277 and 1,328 m have been identified 

adjacent to the main section described above. 

Elsewhere in the area, 11 shorelines have been 

recognized at elevations that range from 1,279 to 

1,332 m. 

To further refine age control of the deposits and 

shorelines in the Hot Springs Mountains area, detailed 

mapping and sedimentological studies are needed. 

These studies are now in progress. 

ABSTRACTS OF PRESENTATION 39 

Changes in Pyramid Lake Sediment Composition in Relation to 

Fluctuations in Lake Level and Land-Use Practices 

Martin E. Lebo and John E. Reuter, Division of Environmental Studies, 

University of Cal(fornia, Davis 

Phillip A. Meyers, Department of Geological Sciences, University of Michigan 

Sediment cores were collected from the shallow 

and deep basins of Pyramid Lake, Nevada, to analyze 

changes in the elemental composition of sedimentacy 

material during the past 600 to 1,000 yr. Changes in 

carbon (C), nitrogen (N), and phosphorus (P) content 

of particles and pore-water nutrient concentrations are 

associated with variations in lake volume, water 

supply, and overall productivity of the lake. General 

relations of human activities in the Truckee River 

Basin to changes in sediment composition were 

determined for the historical record, and then those 

relations were used to analyze deeper parts of the cores. 

Several relations of human activities or climate 

variations to sediment composition were identified. 

First, the CaC03 and particulate C content of sediment 

in the shallow basin decreased when river inflow to the 

lake was large. Conversely, CaC03 content of 

sediments throughout the lake decreased when river 

loading of calcium (Ca) was low during decreased 

inflow. Finally, total P content of sediments increased 

with decreasing lake volume. This unexpected relation 

was due to higher inorganic P content of particles as 

lake level decreased and may have been part of a 

mechanism maintaining constant P concentration in 

Pyramid Lake despite fluctuations in lake volume and 

P loading over time. 

REFERENCE 

The observed changes in the composition of 

sediments during the past 600 to 1,000 yr indicated the 

productivity of Pyramid Lake may have increased to 

the current mesotrophic conditions in two stages. P.A. 

Meyers and others ( 1980), in an earlier study of 

Pyramid Lake sediments, suggested that productivity 

increased from oligotrophic to mesotrophic conditions 

at around A.D. 1300 to 1400. The compositional data 

did not provide strong support for an increase in 

productivity at that time. Changes in elemental 

composition of sediments provided much stronger 

evidence for higher productivity in Pyramid Lake 

beginning in A.D. 1600. In sediments of the deep 

basin, organic P (PP org) content of sediments increased 

abruptly from A.D. 1600 to 1700 and from A.D. 1850 

to 1935. Increase in productivity in the latter period 

also was supported by an increase in particulate N (PN) 

content of sediment. A comparison of phosphate and 

ammonium concentrations in pore waters indicated 

that the remineralization of organic matter over time 

could not account for the magnitude of observed 

increases in PP org and PN content for these two 

periods. The observed increases, therefore, could be 

interpreted as increases in lake productivity. 

Meyers, P.A., Maring, H.B., and Bourbonniere, R.A., 1980, Alkane and alkanoic acid variations with depth in modern 

sediments of Pyramid Lake, in Proceedings of Ninth International Meeting on Organic Geochemistry. 

ABSTRACTS OF PRESENTATION 41 

Paleomagnetic Dating and Correlation of Pre-Holocene Lake 

Sequences in the Northern Great Basin 

Joseph C. Liddicoat, Department of Environmental Science, 

Barnard College, Columbia University 

The paleomagnetic field behavior recorded in 

sediment deposited in Pleistocene lakes in the northern 

Great Basin has been studied in sufficient detail that 

dating and correlation of stratigraphic sequences may 

be possible within and between basins that contained 

some of the larger lakes (Lahontan, Bonneville, 

Russell). For the most part, however, dating and 

correlation are not possible unless a sequence contains 

a reversal of polarity or indicates unusual field 

behavior that functions as a stratigraphic marker. Two 

such markers are ( 1) a path of the Virtual Geomagnetic 

Poles that loops through the southern Pacific Ocean 

that is recorded in sediment on Paoha Island in the 

Mono Basin (California) and in Long Valley 

(California) and is assigned an age of about 150,000 yr, 

and (2) the Mono Excursion that is present in the Mono 

and Lahontan Basins in sediment dated by 14C and 

tephrochronology to be between 28,000 and 26,000 yr 

old. Short- and long-term fluctuations in the 

declination and inclination recorded in the Sehoo and 

Eetza Formations in the Truckee River Canyon 

between Wadsworth and Nixon, Nevada, currently 

( 1993) are being compared to time-equivalent(?) 

records for the Bonneville and Alpine Formations in 

the Bonneville Basin near Delta, Utah, to help 

determine the effectiveness of dating and correlation of 

spatially separated lake sequences. 

ABSTRACTS OF PRESENTATION 43 

Design of Drive Samplers for Cohesive Sediments 

Daniel A. Livingstone, Departments l?{ Zoology and Geology, Duke University 

Most drive samples for cohesive sediments are 

crude and only suitable for taking cores a meter or less 

in length. Adherence to several design criteria would 

increase the length of core that could be taken in a 

single drive beyond the 30 m sometimes achieved at 

sea. In particular, it is important to minimize the force 

needed to drive the sampler and maximize the length of 

core barrel that can be driven without buckling. 

All other things being equal, the force required to 

core cohesive sediment increases with the kerf ratio 

(that is, the ratio of wall area to sample area) of the 

sample tube: 

kerf ratio= 

(outside diameter) 2 (inside diameter) 2 

(inside diameter) 2 

{1) 

Apart from the Shelby tube and some rod-driven 

piston samplers, all common core samplers used by 

limnologists and oceanographers have a very high kerf 

ratio. This high kerf ratio limits the length of sample 

that can be taken in a single drive in deep water. The 

high kerf ratio increases the weight and cost of the 

driving apparatus in any depth of water, and it increases 

the bow wave, tending to blow away soft sediment at 

the mud-water interface. 

In addition to needing a low kerf ratio, an 

effective sampler needs a sharp cutting shoe that has a 

fine taper on the outside. The length of a single drive 

must not exceed a safe sampling distance, which 

depends on the ambient hydrostatic plus atmospheric 

pressure. The feedback loop between normal pressure 

and frictional resistance that develops as a sample tube 

is driven into the sediment needs to be controlled in 

some way. On the inside wall of the tube, feedback is 

decreased by a tight-fitting piston or by foils paid out 

from the cutting shoe. Inside feedback also can be 

decreased by foils on the outside, but there is no way of 

accommodating so much foil in a thin-walled shoe. 

Outside feedback also can be decreased by using a 

cutting shoe and couplings of an outside diameter 

slightly greater than that of the sample tube or by using 

a tube so short-for example, a Shelby tube-that the 

frictional forces do not exceed manageable levels. 

In most samplers, the kerf ratio is high because 

of excessive outside clearance or a thick plastic liner, or 

both. In free-fall samplers, for use in deep water, there 

has been a tendency to increase the stiffness of the core 

barrel by increasing the wall thickness, but increasing 

the wall thickness is not effective because the heavy 

wall increases proportionately the load that needs to be 

imposed on the core barrel to drive it. A more effective 

method is to increa.."ie core length by using a thin-walled 

core barrel of large diameter that has a fine cutting 

shoe, a small outside clearance (2-3 percent), and no 

liner. Mooring the vessel from which the sampler is 

operated will eliminate the bending movement due to 

lateral motion of the vessel and the samples. Mooring 

will change the core barrel from something close to an 

Eulerian slender column with one fixed end and one 

free end to something much closer to a column with 

two fixed ends. This increases the amount of force that 

can be used to drive the core barrel by a factor 

approaching 16 and the length of core barrel that can be 

driven without buckling by a factor approaching 4. 

If the free-fall sampler is used for minimally 

disturbed sampling of the mud-water interface instead 

of maximal depth of penetration, speed of penetration 

needs to be controlled with a hydraulic choke. 

ABSTRACTS OF PRESENTATION 45 

Late Quaternary Stratigraphy of Owens Lake, California 

Steve P. Lund, MarkS. Newton, and Douglas E. Hammond, Department o.f Earth Sciences, 

University l~{ Southern Cal(fornia 

Owen K. Davis, Department o.f Geosciences, University o.f Arizona 

J. Platt Bradbury, U.S. Geological Survey 

Introduction 

Owens Lake (36°30'N., ll8°W.) is a large 

closed-basin lake located on the western margin of the 

Basin and Range province in east-central California. 

The lake is fed primarily by the southward-flowing 

Owens River. Owens Lake and Owens River are in a 

north-south-trending graben called the Owens Valley, 

which is bounded by the Sierra Nevada on the west and 

the Inyo Range on the east. Owens Lake is in the rainshadow of the Sierra Nevada and currently (1993) 

receives less than 13 em of rainfall per year, mostly 

from strong winter storms generated in the northeast 

Pacific Ocean. The drainage basin of the lake covers 

more than 6,500 km2, including 180 km2 ofthe 

Pleistocene-glaciated eastern Sierra Nevada margin. 

Prior to diversion of Owens River water for irrigation 

( 1873), Owens Lake was a shallow (less than 1O-mdeep) hypersaline lake that had a surface area of 

290 km2 (Gale, 1914). The site of the former lake is 

currently a salt-encrusted playa, 186 km2 in area at an 

elevation of 1,081 m. 

During the Pleistocene, Owens Lake 

intermittently overflowed its southern margin (sill 

elevation of 1, 146 m) into a continuation of the Owens 

River that, in tum, fed China and Searles Lakes to the 

south (Gale, 1914; Smith, 1978). Attimes of overflow, 

the lake was as much as 7 5-m deep and had a surface 

area of694 km2 (Smith, 1978). A great deal of 

scientific study has been done at Searles Lake (Gale, 

1914; Flint and Gale, 1958; Smith, 1962, 1978, 1979) 

and at Mono Lake (Russell, 1889; Lajoie, 1968; 

Newton, 1991 ), but little is known of the history of 

Owens Lake, except by inference from the history of 

Searles Lake (Smith, 1978). Matthes ( 1940) used early 

sediment core logs from Owens Lake to assess the 

timing of Pleistocene glaciation, and Smith and Pratt 

( 1957) reported that Owens Lake contains more than 

280 m of predominantly lacustrine sediments. The 

purpose of the current study is to better characterize the 

late Pleistocene and Holocene history of Owens Lake 

sediments. 

Field and Laboratory Studies 

Sediment cores were collected from the southcentral part of Owens Lake on three occasions. In 1984 

and 1987, a modified Livingston-type piston corer was 

used to collect one 12-m core (OWL84B in 1984) and 

six 4- to 5-m cores (OWL87 A-Fin 1987). In 1990, two 

30-m cores (OWL90/l-2) were collected using a truckmounted split-spoon corer. Core OWL84B was 

obtained closest to the center of the lake basin; all of 

the other cores were obtained about 2 to 3 km 

southwest of OWL84B and within 1.5 km of each 

other. Access to the lake playa for the coring 

operations was kindly provided by William McClung 

of Lake Minerals Corporation (Lone Pine, California). 

All of the cores were stored in a refrigerated 

core-storage facility during subsequent laboratory 

analysis. All the cores were described physically and 

slabbed. Representative cores were X -rayed, and 

selected measurements of the organic/carbonate 

fraction (loss on ignition), grain size (Coulter counter), 

mineralogy (X -ray diffraction), and microfossils 

(diatoms and pollen) were made. Extensive rockmagnetic measurements (for example, magnetic 

susceptibility) also were made on these cores to help 

correlate them. All of these measurements form the 

basis for the core correlations and composite lake 

stratigraphy described in the next section. Five 

radiocarbon dates were obtained, and paleomagnetic 

secular-variation studies (Brandsma and others, 1989) 

were performed on selected cores to help determine a 

timeframe for the stratigraphy. 

Lake Stratigraphy 

All of the cores have a common stratigraphy, 

which broadly consists of four lithologic units (fig. 1 ). 

The units are, with increasing depth: Unit A - salt, 

Unit B -brown oolitic sand and silt, Unit C- brown 

muddy silt, and Unit D- black muddy silt. Below 

Unit D, the sediment sequence cycles between 

lithologies resembling Units C and D to a composite 

depth of 34m below the surface (fig. 2) without 

reappearance of lithologies resembling Units A or B. 

ABSTRACTS OF PRESENTATION 47 
0 

2 

~ 3 <( 

U) 

:s: 4 0 

...J 

~ 5 

U) 

ffi 6 1-

UJ 

::2: 7 

15,800 __ ±610 

0 10 100 500 

10-6 Sl UNITS 

0 

EXPLANATION 

::C 8 

h:: 

SEDIMENTARY UNITS 

~ 9 [@ Salt (Unit A) 

10 [~~::::_o;j Oolitic sand and silt (Unit B) 

~ Brown muddy silt (Unit C) 

11 t-::-=-::-=3 Black muddy Silt (Unit D) 

0 10 100 500 

12 

0 10 100 500 

i2~~o • RADIOCARBON AGE, IN YEARS BEFORE PRESENT 10-6 Sl UNITS 

1o-6 Sl UNITS 

Figure 1. Correlation of four late Quaternary sediment cores collected from the south-central part of Owens Lake. Four 

lithologic units (A-0) have been described and correlated in all of the cores. Five radiocarbon age estimates (bulk organic 

fraction) have been recovered for initial age control. Magnetic-susceptibility profiles for the four cores are shown to the right 

of each lithostratigraphic column. 

The uppermost lithologic unit (A - salt) is a 

crystalline layer of intergrown halite (N aCI), trona 

[(Na3(C03)(HC03)·2H20)], and gaylussite 

[(Na2Ca(C03h·5H20)] that contains smaller 

proportions of other common alkali carbonates (Smith 

and others, 1987). Unit A is generally I to 2 m thick in 

the area of the cores. The salt was deposited when 

Owens Lake desiccated after diversion of all Owens 

River water to the Los Angeles Aqueduct in 1913 

(Gale, 1914). 

Unit B (brown oolitic sand and silt) is 

characterized by alternating layers of coarse-grained 

(as much as 3-mm-thick) oolitic buff-tan sand; coarseto medium-grained, well-sorted micaceous sand that 

contains tiny (0.5-mm) ooids; and dark-brown 

micaceous muddy silt. The large ooids have a dark 

amber core of aragonite and an outer white rind of 

high-Mg calcite (Newton, 1991). Unit B is generally 

less than or equal to 1 m thick in the cores, but is 5 m 

thick in core OWL84B, which is closest to the center of 

the lake basin. In core OWL84B, Unit B coarsens 

downward to a depth of 1.5 m below the salt; below this 

level, Unit B fines downward and contains intermittent 

fine-scale (millimeters) lamination and rare ostracods. 

Cross bedding is present, but is not an outstanding 

feature of this unit. 

Unit C (brown muddy silt) is an olive-brown 

muddy silt (average grain size of20 Jlm), which is rich 

in quartz and poor in clay minerals. Micritic calcite 

(CaC03) is detectable in thin section, and X-ray 

patterns indicate the presence of high-Mg calcite 

(Newton, 1991). The calcium carbonate consists of 

about 15 dry-weight percent of the sediment (fig. 3). 

Ostracods are rare in this unit and diatom variety is 

poor, except for numerous specimens of the diatom 

Stephanodiscus niagarae. Unit C generally is about 

1.5 m thick in the cores, but is about 3 m thick in core 

OWL84B. The boundary between Units B and C 

seems to be gradational; grain size coarsens slightly at 

the top of Unit C. However, the boundary between 

Units C and Dis quite different. 

The base of Unit C in the cores is a sharp 

discontinuity characterized by five distinctive features: 

(I) A strong downward increase in magnetic 

susceptibility (figs. 1, 2); (2) an erosional(?) 

discontinuity that has as much as 1 em of topography; 

(3) a 1- to 3-mm-thick lag deposit of coarse micaceous 

sand, containing purplish frosted quartz grains; 

48 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
4 

5 

7 

8 

9 

10 

11 

L.U 12 

u 

<( 13 1.1.. 

a: 14 ::::::> 

(f) 

0 

z 16 

<( 

....J 17 

~ 18 

0 

....J 19 w 

al 20 

(f) 

a: 21 

w 

1- 22 w 

~ 23 

~ 24 

:i 25 

1-

0... 26 w 

0 27 

28 

29 

30 

31 

32 

33 

34 

35 

Unit D 

Unit C 

-----------

Unit D 

------------

1 10 100 

MAGNETIC SUSCEPTIBILITY, IN 10-6 Sl 

(4) evidence of mud cracks and rusty weathering 

penetrating downward into Unit D; and (5) 

substantially coarser average grain size in Unit C than 

in Unit D. This boundary is interpreted to be a hiatus 

caused by complete desiccation of Owens Lake. The 

duration of the event is not well known, but correlation 

of magnetic-susceptibility profiles and secularvariation records from all cores, indicated that the 

existing top of Unit Dis essentially an isochron. Thus, 

any deflation associated with the desiccation most 

likely stripped away almost exactly the same amount of 

material from the lake surface for several square 

kilometers around the core sites. Alternatively, the 

isochronous top ofUnit D, the thin lag deposits, and the 

minor evidence of erosion might indicate that the 

desiccation was relatively short-lived. 

Unit D, the black muddy silt (pitch black on 

original core recovery with an H2S odor), is a highly 

reduced, structure less muddy silt (average grain size of 

10 J..Lm) that quickly oxidized to light gray and 

contained orange speckles. The orange speckles are 

probably goethite (FeOOH), which replaced iron 

sulfide concretions when the silt was exposed to 

oxygen. The presence of greigite (FeS) in Unit D has 

been inferred from paleomagnetic studies, in which a 

strong magnetic overprint represented by a chemically 

unstable phase was observed. The mud fraction in 

Unit D contain~ some clay minerals but is dominated 

by quartz and is presumably rock flour derived from 

nearby Sierra Nevada glaciers, which fed the lake. 

Low-mg-calcite (Newton, 1991) averages about 7 dryweight percent in the sediments. Unit D contains 

ostracods and a great abundance and diversity of 

diatoms typical of freshwater oligotrophic lakes. 

Pollen profiles in Unit Dare notable for the presence of 

Sequoiadendron sp. pollen derived from Giant 

Redwood trees that now grow only west of the Sierra 

Nevada crest. 

Below Unit Din cores OWL90/1 and OWL90/2, 

an oscillation between lithologies resembling Units C 

and D was reported to a depth of34 m (fig. 2). Sharp 

boundaries in magnetic susceptibility below 20 m may 

indicate earlier desiccation events, but these intervals 

have not been studied well enough to assess this 

Figure 2. Magnetic-susceptibility profile for core OWL90/2. High values of magnetic susceptibility can be associated with 

Unit D type lithology, whereas low values can be associated with Unit C type lithology. Preliminary age estimates, in years 

B.P., for the core are based on radiocarbon dating and paleomagnetic secular-variation studies. 

ABSTRACTS OF PRESENTATION 49 
5 10 15 20 25 0 10 20 30 40 50 60 100 

Organic Material Calcium Carbonate Clastics 

DRY WE I G H T, IN PERCENT 

Figure 3. Summary plot of dry-weight percentages of organic material, calcium carbonate, and clastics in Units 8 through 

D from Owens Lake, California. 

possibility. No evidence of lithologies resembling 

Units A orB below Unit D was observed in either of 

these cores. 

Chronology 

Five radiocarbon dates were recovered from bulk 

organic material in these cores (fig. 1 ). Two age 

determinations were originally made by Beta 

Laboratories, which returned almost identical ages for 

the top of Unit Din two different cores (15,460 yr B.P. 

for OWL84B; 15,800 yr B.P. for OWL87F). Three age 

determinations also were made on core OWL87D by 

the University of Arizona Radiocarbon Laboratory. 

However, their basal-date within Unit D was 13,400 yr 

B.P., which is less than other Unit D age esthnates. 

Two dates in Unit C were 10,500 yr B.P. near the 

Unit C/B boundary and 12,400 yr B.P. near the base of 

Unit C. 

Limited paleomagnetic secular-variation (PSV) 

studies were done on Unit D, and the PSV records were 

correlated to other well-dated records from the Western 

United States (Brandsma and others, 1989; Lund and 

others, 1988). As discussed previously, the PSV 

records seemed to indicate that the top of Unit D is an 

isochron to within 100 to 200 yr everywhere in the 

study area. The age of this horizon is a bit ambiguous 

in that the PSV in this region broadly repeated its 

pattern every few thousand years (Lund and others, 

1988). The PSV pattern at the top of Unit D could 

correlate with features dated elsewhere as either 

approximately 12,500 yr B.P. or approximately 

15,000 yr B.P. Currently, the preferred PSV 

correlation indicated that the top of Unit Dis 

approximately 15,000 yr B.P., and the base of Unit D 

in core OWL90/2 is approximately 19,500 yr B.P. The 

lower parts of the cores obtained in 1990 have not yet 

been studied. 

Limited PSV studies on Unit C in core OWL84B 

were done. The preliminary results are consistent with 

the top of Unit C in this core being about 7,000 yr old. 

This age is substantially younger than the radiocarbon 

date in core OWL87D and could indicate some erosion 

near the top of Unit C (and in Unit B) in the 1987 and 

1990 cores (which were obtained closer to the 

paleoshoreline). 

Lake History 

The presence of freshwater diatoms and the low 

concentration of CaC03 indicates that Unit D may 

have been deposited in a through-flowing permanent 

lake during late Pleistocene time (about 20,000 to 

15,000 yr B.P.) that was associated with either steady50 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
state glacial-maximum conditions or early retreat from 

glacial-maximum conditions. Sedimentation rate in 

the lake was quite high during this time intetval (about 

2 m/103 yr) due to the heavy flux of glacial outwash 

(rock flour) from the neighboring Sierra Nevada 

glaciers. The lake could have been holomictic because 

there is ample X-ray evidence of bioturbation in the 

bottom sediments even though the sediments were 

reduced below the sediment/water interface. This 

intetval is broadly correlative to the Parting Mud 

intetval in Searles Lake (Flint and Gale, 1958; Smith, 

1962). 

The shift to a desiccation surface at the top of 

Unit Dis quite abrupt. However, the uppermost meter 

of Unit D does contain some evidence for a coarsening 

in average grain size and an increase in silt fraction, 

which might portend the desiccation. Unless there has 

been some uniform deflation of Unit D sediments, this 

desiccation may have occurred about 15,000 yr B.P. 

(The alternative, that the desiccation occurred about 

12,500 yr B.P., requires that the replicate radiocarbon 

dates be incorrect.) This desiccation could be 

correlated to a substantial change in the Parting Mud 

sediments at Searles Lake at about 15,000 yr B.P. 

(Smith and Street-Perrott, 1983; Benson and others, 

1990). 

Unit C indicates the return of a mostly permanent 

lake after the desiccation and after recession of the 

main Sierra Nevada glaciers. The much coarser 

sediment, higher CaC03, lower sedimentation rates 

{?), and oxic sediment indicated that Owens Lake was 

a closed-basin lake that only intermittently rose to its 

sill and overflowed to the south. The radiocarbon dates 

indicated that this lake was present during the 

Pleistocene/Holocene transition (approximately 

12,000 to 10,000 yr B.P.) and was correlative with the 

uppermost Parting Mud at Searles Lake. There is some 

evidence in core OWL84B that this lake persisted into 

early Holocene time (to about 7,000 yr B.P.?), which 

would be consistent with recent evidence from Mono 

Lake that a permanent, relatively deep lake existed at 

Owens Lake from 9,000 to 6,500 yr B.P. 

Unit 8 represent'i the middle to late Holocene 

intetval in Owens Lake history. The carbonate ooids, 

coarse-grained sediments, and intermittent cross 

stratification indicated that the lake was still a closedbasin lake, but its average lake level was probably 

much lower, and frequent desiccations (a true playa 

lake) occurred. The lake may have become saturated 

with various alkali minerals that were likely 

precipitated out during each desiccation and 

redissolved during the next wetting, until the alkali 

minerals were finally precipitated as Unit A in 1913. 

The alternating pattern of Unit C and D type 

sedimentation below Unit D in the 1990 OWL cores 

(described previously) probably represented an 

alternation in the persistence of water flow in the 

Owens Lake drainage basin. This alternation could be 

related to temperature, precipitation variation, or the 

ebb and flow of continental glaciation. The study of 

these sediment'i is in the initial stages. If the sediment 

history at Owens Lake is similar to Searles Lake 

(Smith, 1962), Unit D sediments below 25 m in core 

OWL90/2 might correlate with mud stringers in the 

Lower Salt at Searles Lake. If the sediments do 

correlate, then the base of core OWL90/2 is probably 

about 34,000 yr old. 

ABSTRACTS OF PRESENTATION 51 
REFERENCES 

Benson, L.V., Currey, D.R., Dorn, R.I., Lajoie, K.R., Oviatt, C.G., Robinson, S.W., Smith, G.I., and Stine, S., 1990, 

Chronology of expansion and contraction of flmr Great Basin lake systems during the past 35,000 years: Paleoocean., 

Paleoclimat., Paleoeceol., 78, 241-286. 

Brandsma, D., Lund, S.P., and Henyey, T.L., 1989, Paleomagnetism oflate Quaternary marine sediments from Santa Catalina 

basin, Calill1rnia, continental borderland: Journal of Geophysical Research, v. 94, p. 547-564. 

Flint, R.F., and Gale, W.A., 1958, Stratigraphy and radiocarbon dates at Searles Lake, California: American Journal of 

Science, v. 256, no. 10, p. 689-714. 

Gale, H.S., 1914, Notes on the Quaternary lakes of the Great Basin, with special reference to the deposition of potash and 

other salines, in chap. N, Salines, in Contributions to economic geology, 1912-Part I, Metals and nonmetals except 

fuels: U.S. Geological Survey Bulletin 540-N, p. 399-406. 

Lajoie, K.R., 1968, Late Quaternary stratigraphy and geologic history of Mono Basin, California: Berkeley, University of 

California, Ph.D. dissertation, 271 p. 

Lund, S.P., Liddicoat, J.C., Lajoie, K.L., Henyey, T.L., and Robinson, S.W., 1988, Paleomagnetic evidence for long-term (1 04 

year) memory and periodic behavior in the Earth's core dynamo process: Geophysical Research Letters, 15, 

p. 1101-1104. 

Matthes, F. E., 1940, Report of the Committee on Glaciers: American Geophysical Union Transactions, p. 518-523. 

Newton, M.S., 1991, Holocene stratigraphy and magnetostratiography of Owens and Mono Lakes, eastern California: 

University of Southern Calitl1rnia, Los Angeles, Ph.D. dissertation, 330 p. 

Russell, I.C., 1889, Quaternary history of Mono Valley, California: U.S. Geological Survey 8th Annual Report, 394 p. 

Smith, G.I., 1962, Subsurface stratigraphy oflate Quaternary deposits, Searles Lake, California-A summary [article 82], 

in Short papers in geology and hydrology, articles 60-119, Geological Survey research 1962: U.S. Geological Survey 

Professional Paper 450-C. p. C65-C69. 

__ 1978, Pleistocene geology, Searles Valley, California, in Guidebook tor tfiends of the Pleistocene Pacific Coast section, 

November 10-12, 1978: Menlo Park, Calif., Friends of the Pleistocene, Pacific Coast Section. 

__ 1979, Subsurface stratigraphy and geochemistry oflate Quaternary evaporites, Searles Lake, California, U.S. Geological 

Survey Professional Paper 1043, 130 p. 

Smith, G.I., Friedman, Irving, and McLaughlin, R.J., 1987, Studies of Quaternary saline lakes-III, Mineral, chemical, and 

isotopic evidence of salt solution and crystallization processes in Owens Lake, California, 1969-1971: Geochemica et 

Cosmochimica Acta, v. 51, no. 4, p. 811-827. 

Smith, G.I., and Pratt, W.P., 1957, Core logs from Owens, China, Searles, and Panamint basins, California, U.S. Geological 

Survey Bulletin l 045-A, 31 p. 

Smith, G.I., and Street-Perrott, F.A., 1983, Pluvial lakes ofthe Western United States, in S.C. Porter, ed., The late Pleistocene 

(late Quaternary Environments of the United States, 1 ): Minneapolis, University of Minnesota Press, p. 190--212. 

52 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Holocene Lake-Level Variations and Eolian Activity 

in the Oregon Great Basin 

Patricia F McDowell, Department o.f Geography, University of Oregon 

Daniel P Dugas, Intermountain Research, Silver City, Nevada 

A preliminacy chronology of lake-level 

variation was compiled, using the data available from 

the Fort Rock, Chewaucan, Alkali, and Harney Basins, 

Oregon. Dcying of the large paleo lakes that occupied 

the basins between approximately 20,000 and 13,000 

yr B.P. (isotope stage 2) set the stage for Holocene 

event~. The youngest lacustrine radiocarbon date for 

the Fort Rock Basin is 11,500 yr B.P. (McDowell and 

Benjamin, 1991 ). A radiocarbon date for came lid bone 

from the same area indicates that the Fort Rock Basin 

was dty or almost dty by 10,300 yr B.P. There are no 

direct dates on the dcying of the large paleo lakes in 

Alkali, Chewaucan, or Harney Basins. Archaeological 

evidence indicates that Alkali Basin was dty or almost 

dty by about 11,000 yr B.P. (Willig, 1988a). 

There is no firm evidence from Oregon for a 

lake-level rise during the Younger Dcyas ( 11,500 to 

10,000 yr B.P.) determined for the Lahontan Basin, 

Nevada, and the Bonneville Basin, Utah (Currey, 

1988). The Alkali, Chewaucan, and Harney Basins had 

moderate to high lake-level rises during the early 

Holocene. Dates from the Harney Basin indicate that, 

at 9,600 yr B.P., Harney and Malheur Lakes coalesced 

and stood at approximately 3 m below their highest 

shoreline. and at 8,900 yr B.P .. the combined lake stood 

at its highest shoreline and overflowed (Gehr and 

Newman, 1978; Gehr, 1980). Dugas (1993) recently 

obtained dates indicating- a moderate lake rise in the 

Harney Basin at about 9,500 to 9,300 yr B.P. In Alkali 

Basin, a date of9,800 yr B.P. wa~ obtained on ostracod 

shells. In addition, S. W. Robinson obtained a 

radiocarbon date of 9,400 yr B.P. from Htufa-like 

carbonates on beach gravels" that may represent a 

moderately low lake level in the Lake Abert subbasin 

of the Chewaucan Basin (cited in Gehr, 1980, 

p. 74-75). There is additional undated stratigraphic 

evidence indicating the presence of early Holocene 

lakes or marshes in Alkali and Chewaucan Basins. 

Based on archaeological evidence, Willig ( 1988a) 

proposed that shallow water bodies developed in Alkali 

Basin three times after 10,000 yr B.P. These lake rises 

are not radiometrically dated, but Willig (1988b) 

proposed that the first two rises occurred between 

10,800 and 7,000 yr B.P. After the isotope stage 21ake 

in the Chewaucan Basin declined to a low level, an 

extensive lake, called the ZX Lake, reformed (Allison, 

1982). The ZX lake stand is not radiometrically dated, 

but its relation to archaeological sites (Oetting, 1989) 

indicates that it probably formed and then desiccated 

before 11,000 to 8,000 yr B.P. 

The middle Holocene record indicates that 

dryness and eolian activity dominated. In the Fort 

Rock Basin, eolian sands overlying paleo lake deposits 

dated from 6,800 yr B.P. and younger (McDowell and 

Benjamin, 1991 ). Dunes in the Harney Basin were 

actively building just after 5,000 yr B.P. (Dugas, 1993), 

and intermittently during the late Holocene. Sand 

dunes elsewhere in the basins generally had very weak 

soil development and appear to be no older than middle 

to late Holocene age. Evidence from archaeological 

sites supports a moister period in the late Holocene, 

called the nco-pluvial period by Allison ( 1979). 

Pettigrew (1985), Oetting (1988), and Willig (1988b) 

reported evidence in several sites on the east shore of 

Lake Abert of a lake rise to about 6 m above the 

modem average lake level. Allison (1979, 1982) 

reported low undated beach lines in several places 

around the Chewaucan and Fort Rock Basins that he 

attributed to the nco-pluvial period. 

The evidence for a dry landscape and for eolian 

activity in the tniddle Holocene, and possibly wetter 

conditions in the late Holocene, is consistent with other 

Holocene records from this region. The pollen record 

from Diamond Pond indicates dry conditions from 

6,000 to 5,400 yr B.P., moistest conditions at 4,000 to 

2,000 yr B.P., and somewhat drier conditions with 

short-term fluctuations after 2,000 yr B.P. (Wigand, 

1987). Sand dunes were active in the Catlow Basin in 

the middle Holocene, and several alternating episodes 

of eolian activity and soil development occurred during 

the last 3,400 yr B.P. (Mehringer and Wigand, 1986). 

ABSTRACTS OF PRESENTATION 53 
REFERENCES 

Allison, I.S., 1979, Pluvial Fort Rock Lake, Lake County, Oregon: Oregon State Department of Geology and Mineral 

Industries Special Paper 7, 72 p. 

__ 1982, Geology of pluvial Lake Chewaucan, Lake County, Oregon: Corvallis, Oregon State University Press, Studies in 

Geology 11, 79 p. 

Currey, D.R., 1988, Isochronism affinal Pleistocene shallow lakes in the Great Salt Lake and Carson Desert regions of the 

Great Basin [abs]: Amherst, University of Massachusetts, American Quaternary Association Program and Abstracts 9f 

the 1Oth Biennial Meeting, p. 11 7. 

Dugas, D.P., 1993, Formation processes and chronology of dune islands at Malheur National Wildlife Refuge, Harney County, 

Oregon: Eugene, University of Oregon, Ph.D. dissertation, 220 p. 

Gehr, K.D., 1980, Late Pleistocene and recent archaeology and geomorphology ofthe south shore of Harney Lake: Portland, 

Ore., Portland State University, Master's thesis, 170 p. 

Gehr, K.D., and Newman, T.M., 1978, Preliminary note on the late Pleistocene geomorphology and archaeology of Harney 

Basin, Oregon: Ore Bin, v. 40, no. 10, p. 165-170. 

McDowell, P.F., and Benjamin, J.E., 1991, Report on CONUS OTH-B Archaeological Project to Heritage Research 

Associates, Eugene, Ore., (unpub. data). 

Mehringer, P.J., Jr., and Wigand, P.E., 1986, Holocene history of Skull Creek dunes, Catlow Valley, southeastern Oregon, 

U.S.A.: Journal of Arid Environments, v. 11, no. 2, p. 117-138. 

Oetting, A.C., 1988, Archaeological investigations on the east shore of Lake Abert, Oregon, v. 2: Oregon State Museum of 

Anthropology OSMA Report 88-6, 334 p. 

Oetting, A.C., 1989, Villages and wetlands adaptations in the northern Great Basin-Chronology and land use in the Lake 

Abert -Chewaucan Marsh Basin, Lake County, Oregon: Eugene, University of Oregon, Ph.D. dissertation, 4 73 p. 

Pettigrew, R.M., 1985, Archaeological investigations on the east shore of Lake Abert, Lake County, Oregon, v. 1: Eugene, 

University of Oregon Anthropological Paper 32, 229 p. 

Wigand, P.E., 1987, Diamond Pond, Harney County, Oregon-Vegetation history and water table in the eastern Oregon 

Desert: Great Basin Naturalist, v. 47, no. 3, p. 427-458. 

Willig, J.A., 1988a, Paleo-archaic adaptations and lakeside settlement patterns in the northern Alkali Basin, in Willig, J.A., 

Aikens, C.M., and Fagan, J.L., eds., Early human occupation in far western North America--The Clovis-Archaic 

interface: Nevada State Museum Anthropological Paper 21, p. 417-482. 

Willig, J.A., 1988b, Lake Abert sediment analysis--Phase III, in Oetting, A.C., Archaeological investigations on the east 

shore of Lake Abert, Oregon, v. 2: Oregon State Museum of Anthropology OSMA Report 88-6, p. 334. 

54 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Sedimentary Analyses from the Owens Lake Core and 

Their Implications for Climate Change 

Kirsten M. Menking, Hannah M. Musler, and RobertS. Anderson, University o.f Cal(fornia 

James L. Bischoff and Jeffrey P. Fitts, US. Geological Survey 

Sedimentary analyses of a 323-m core from 

Owens Lake, in eastern California, indicated lithologic 

variations on many different time scales. Grain-size 

analysis, organic carbon content, CaC03 content, and 

water content were determined from point samples 

taken at 2- to 3-m intervals down the core. In addition, 

sand, silt, and clay percentages were measured on 

3.5-m-long channel samples to supplement pointsample grain-size data. Clay mineralogy of these 

channel samples also was determined. 

Grain-size analysis of point samples defined two 

distinctive depositional regimes (fig. 1 ). Except for a 

few thinly bedded coarse-grained layers at the top of 

CfJ 

a: 

50 

100 

~ 150 w 

2: 

~ 

::r:' b: 200 

w -------------- 0 

250 

300 

0.05 0.10 0.15 0.20 

MEAN GRAIN SIZE, IN MILLIMETERS 

0.25 

Figure 1. Mean grain size as a function of depth in core 

OL-92 from Owens Lake, California. 

the core, mean grain size fluctuated between 0.005 and 

0.015 mm (clay- to silt-sized material) between 7 and 

19 5 m in depth. In contrast, between 19 5 m and the 

base of the core at 323 m, mean grain size generally 

fluctuated between 0.01 mm (medium fine silt) and 

0.05 to 0.1 mm (coarse silt to fine sand). Coarsegrained sediments tend to be poorly sorted, whereas 

silts and clays are usually much better sorted. Sand 

plus gravel, silt, and clay contents (measured as 

dry-weight percents) of 3.5-m-long channel samples 

broadly mimicked the point-sample trends; coarsegrained material was present in larger percentages 

between 190 and 323 m, whereas fine silts and clays 

predominated from the top of the core to 190 m. 

X -ray diffraction determinations of the clay 

mineralogy of channel samples indicated that illite, 

smectite, and chlorite were the primary clay minerals; 

some samples contained abundant clay-sized quartz, 

plagioclase, and potassium (K) feldspar. Peak areas of 

illite, smectite, chlorite, quartz, plagioclase, and 

K-feldspar were measured, and ratios between the 

minerals were determined for each channel sample. 

Ratios then were compared among samples. Smectite/ 

quartz and plagioclase/K-feldspar varied inversely; 

smectite/quartz had a low value during the last full 

glacial maximum (20,000 yr B.P.), whereas 

plagioclase/K-feldspar was high. Smectite/quartz, 

illite/quartz, and chlorite/quartz ratios were similar; all 

ratios had high values at the same depths. Likewise, 

K-feldspar/quartz and plagioclase/quartz ratios varied 

similarly. 

Carbonate content of point samples varied 

cyclically between 0 and 56 dry-weight percent and 

averaged 14 dry-weight percent between 0 and 

225m. From 225 to 275 m, percent carbonate 

remained at zero, whereas from 275m to the base of the 

core, carbonate content again showed cyclic variations. 

Organic carbon content had very similar oscillations 

between 0 and 220 m; the organic carbon varied 

between 0 and 3 dry-weight percent. Between 220 and 

260 m, organic carbon content was essentially 

0 percent, and from 260 m to the base of the core, it 

ABSTRACTS OF PRESENTATION 55 
oscillated between 6 and nearly 0 percent with an 

average value of 1 percent. 

Five- to ten-gram subsamples of the grain-size 

point samples were weighed and then heated to drive 

off pore fluids. The dried samples were reweighed, and 

the water contents were calculated. With the exception 

of the top 1 0 m of the core, water content decreased 

from almost 65 percent at the top of the core to about 

13 percent at 240 m. Water content increased to a high 

of 54 percent at 290m and then decreased to I 0 percent 

at the base of the core. 

The various data sets bring up a number of 

questions. The change from interbedded sands and 

silts in the lower one-third of the core to sediments 

consisting primarily of silt and clay in the upper twothirds of the core occurred at the 195-m depth. Given 

an average sedimentation rate of0.4 mm/yr, this depth 

corresponds to an age of 488,000 yr. In comparison, 

Smith ( 1984) reported a major shift in paleohydrologic 

regime in Searles Lake from dry to intermediate shortly 

after 600,000 yr B.P. Although these two dates are 

quite different, the Owens Lake core currently ( 1993) 

has poor age control, making it difficult to determine 

whether the two lakes had fluctuations on the same 

time scales. If the shifts in paleohydrologic regime (in 

Searles Lake) and in grain size (in Owens Lake) were 

synchronous, the lower, sandy section of the Owens 

Lake core may represent a shallow lake or a fluvial 

REFERENCES 

environment that existed in a drier climate. However, 

the change in depositional style at 195m also may have 

occurred as the result of tectonic factors, namely valley 

deepening or uplift of the spillover sill with respect to 

the top of the lake, causing Owens Lake to be 

volumetrically much larger before spillover after about 

500,000 yr B.P. If not the result of ground-waterdiffusive processes, the presence of the zero carbonate 

and organic carbon zones between 220 and 275 m may 

help to constrain which scenario was more likely. The 

lack of carbonate and organic carbon may indicate a 

very fresh, nutrient poor, unproductive lake, which 

implies that Owens Lake was spilling over into the 

China and Searles Lake Basins. 

As does Newton ( 1991 }, we interpret the 

presence of nonclay minerals (quartz, plagioclase, and 

K-feldspar) in the clay-sized fraction to be the result of 

glacial abrasion in the Sierra Nevada. Of the true clay 

minerals, illite and chlorite may be recycled from 

metasedimentary roof pendants, but smectite is more 

likely produced from the weathering of feldspars 

during soil formation and may, therefore, be more 

indicative of climates conducive to chemical 

weathering. Smectite also is a common weathering 

product of volcanic ash, so care needs to be taken to 

distinguish between true climatic variations and 

volcanic events. 

Newton, M.S., 1991, Holocene stratigraphy and magnetostratigraphy of Owens and Mono Lakes, eastern California: 

Los Angeles, University of Southern California, Ph.D. dissertation, 330 p. 

Smith, G.I., 1984, Paleohydrologic regimes in the southwestern Great Basin, 0-3.2 my ago, compared with other long records 

of"global" climate: Quaternary Research, v. 22, no. 1, p. 1-17. 

56 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
lntrabasinal and Extrabasinal Correlations of Nonmarine 

High-Resolution Paleomagnetic Records of the Middle to 

Late Pleistocene from South-Central Oregon 

Robert M. Negrini, Department a_{ Physics and Geology, 

Cal(fornia State University, Bakersfield 

High-resolution age control is a serious 

problem for those studying climate records associated 

with middle to late Pleistocene lake sediments. One 

possible solution is provided by paleomagnetic secular 

variation (PSV), the low-amplitude variation in the 

direction and intensity of the magnetic field of the 

Earth. If recorded accurately at or near the time of 

deposition of a sediment, PSV is a high-resolution 

correlation tool that can be used for intrabasinal 

and extrabasinal correlations, especially when 

complemented with independent methods of 

correlation (for example, tephrochronology). 

Theoretically, PSV could enable nonmarine 

stratigraphy to be correlated to the well-dated 

chronology common to marine sediment records. 

Examples of correlations based on this technique are 

described for ongoing paleomagnetic and 

lithostratigraphic studies of the sediments of 

Pleistocene Lakes Chewaucan and Lahontan and on 

previously published paleomagnetic records from 

Pleistocene Lake Russell, two unnamed Pleistocene 

lakes, and the Gulf of California. 

Intrabasinal correlations in Lake Chewaucan 

support the theory that secular variation can be used 

to correlate outcrop exposures (three samples per 

horizon) on a depth scale of several centimeters, which 

probably corresponds to a temporal resolution of a few 

hundred years or less. Correlations between outcrop 

and core can still be made, but the resolution is 

somewhat lower. Extrabasinal nonmarine correlations 

are consistent with ( 1) low surface levels in Lakes 

Chewaucan and Lahontan between 27,000 and 

24,000 yr B.P., (2) an age for the last Lahontan 

highstand of less than or equal to 15,500 yr B.P., and 

(3) the existence of three Great Basin lakes that are 

100,000 to 200,000 yr old and that are separated by 

hundreds of kilometers. Preliminary high-resolution 

correlations with the marine record based on 

directional variations were developed for a period from 

approximately 50,000 to 20,000 yr B.P. Preliminary 

correlations with the marine record of lower resolution 

based on paleointensity variations were developed for 

a period from 100,000 to 50,000 yr B.P. 

ABSTRACTS OF PRESENTATION 57 

Paleoclimatic Inferences from Detailed Studies of 

Lake Bonneville Marl, Utah 

Charles G. Oviatt, Department of Geology, Kansas State University 

Marl was the littoral-to-pelagic facies deposited 

in Lake Bonneville at sites distant from sources of 

clastic input. Gilbert ( 1890) referred to the marl as the 

white marl and reported its presence throughout the 

lake basin as a thin blanket deposit. Certain features of 

the white marl are traceable throughout wide areas of 

the basin and provide a means of correlation and 

chronologie control. The base of the white marl is 

time-transgressive with elevation, and its age can be 

inferred accurately from the many radiocarbon ages 

that date the transgression of the lake in the basin 

(Oviatt and others, 1992). The age of the top of the 

marl can be inferred in a similar way, although the top 

is truncated to some extent in most sections. Within the 

white marl, a prominent stratigraphic marker bed that 

is characterized by an abrupt change from massive gray 

marl below to laminated sandy marl above is present in 

most exposed sections. This bed was interpreted as 

representing the drastic change in water depth caused 

by the Bonneville Flood, during which the lake 

dropped approximately 100 m in a few months and 

exposed thousands of square kilometers of former lake 

bottom to subaerial erosion and resedimentation in the 

lake. The flood is dated at about 14,500 yr B.P., and the 

flood bed, therefore, is essentially an isochronous 

stratigraphic unit that can be correlated basinwide. 

Ostracod biostratigraphy provided another means of 

correlating isolated marl outcrops; the ostracod zones 

are traceable basinwide and have been dated in a core 

from the bottom of Great Salt Lake (Thompson and 

others, 1990). 

Basaltic volcanic ashes provided additional 

correlation and chronologie control. In the Sevier 

arm of Lake Bonneville, the Tabernacle Hill ash 

(14,300 yr B.P.) was erupted while the lake was 

overflowing at the Provo shoreline, and the Pahvant 

Butte ash (15,500 yr B.P.) marks a point in the lake 

history when the lake wali within 15 m of the 

Bonneville shoreline (Oviatt and Na~ih, 1989). In the 

northern Bonneville Basin, the Thiokol basaltic ash, 

which was erupted from an unidentified source about 

26,000 yr B.P., is widespread and is a valuable marker 

in the lower part of the marl. 

The marl ranges in thickness from 2 to 3 m, 

depending on elevation and local controls on clastic 

input. Estimated average marl sedimentation rates 

during the transgressive phase of the lake ranged 

between 15 and 20 cm/1 03 yr. During the deepest 

water phase, deposition was as low as 1 to 2 cm/103 yr. 

Measurements of the ratio of aragonite to calcite, 

total percent calcium carbonate, 8180, and 813C in 

cores of the marl can be interpreted as records of lakelevel change in the Bonneville Basin. These four 

variables covaried and responded in a similar way to 

changes in the ratio of evaporation to inflow in the lake. 

Collectively, they provided a record of water chemistry 

and, hence, of water-volume or lake-level change 

through time. A core of marl from the Old River Bed 

area, at the north end of the strait that connected the 

Sevier arm with the main body of Lake Bonneville, 

has yielded a detailed record of changes for about 

5,000 yr of the transgressive phase of the lake (about 

20,000 to 15,000 yr B.P.). Lake-level fluctuations that 

had probable amplitudes on the order of tens of meters 

are inferred from the carbonate record and are 

superimposed on the generally rising trend of the 

transgressive phase of the lake. Because 8180 and 

813C are highly correlated(~= 0.97), there may not 

have been a major shift in isotopic composition of the 

lake water during this part of the transgressive phase of 

the lake. However, comparison with the isotopic data 

from carbonates of Holocene Great Salt Lake (Spencer 

and others, 1984; McKenzie, 1985) indicated a 

possible change in moisture source between the 

Pleistocene and Holocene. 

ABSTRACTS OF PRESENTATION 59 
REFERENCES 

Gilbert, G.K., 1890, Lake Bonneville: U.S. Geological Survey Monograph 1, 438 p. 

McKenzie, J.A., 1985, Carbon isotopes and productivity in the lacustrine and marine environment, in Stumm, Werner, ed., 

Chemical processes in lakes: New York, Wiley, p. 99--118. 

Oviatt, C.G., Currey, D.R., and Sack, Dorothy, 1992, Radiocarbon chronology ofLake Bonneville, eastern Great Basin, USA: 

Palaeogeography, Palaeoclimatology, Palaeoecology, v. 99, p. 225--241. 

Oviatt, C.G., and Nash, W.P., 1989, Late Pleistocene basaltic ash and volcanic eruptions in the Bonneville Basin, Utah: 

Geological Society of America Bulletin, v. 101, p. 292-303. 

Spencer, R.J., Baedecker, M.J., Eugster, H.P., Forester, R.M., Goldhaber, M.B., Jones, B.F., Kelts, Kerry, McKenzie, Judith, 

Madsen, D.B., Rettig, S.L., Rubin, Meyer, and Bowser, C.J., 1984, Great Salt Lake and precursors, Utah-The last 

30,000 years: Contributions to Mineralogy and Petrology, v. 86, p. 321-334. 

Thompson, R.S., Toolin, L.J., Forester, R.M., and Spencer, R.J., 1990, Accelerator-mass spectrometer (AMS) radiocarbon 

dating of Pleistocene lake sediments in the Great Basin: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 78, 

p. 301-313. 

60 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Marine-Terrestrial Correlation as a Means of 

Testing Global Climate Change 

Milan J. Pavich, U.S. Geological Survey 

Introduction-The Correlation Problem 

Correlation is used as a fundamental approach to 

understanding the timing and magnitude of geologic 

change. Correlations, however, are often not 

rigorously tested, nor are they tied to an understanding 

of processes. One of the fundamental working 

hypotheses about climate change, the Milankovitch 

(1930) orbital-forcing model, relies on correlation of 

marine oxygen isotope records as a principal test. In 

general, the present ( 1993) state of testing l!Sed in 

marine geology is considered sufficient support for the 

Milankovitch model. However, questions arise as to 

the sufficiency of the marine-record correlations 

because few well-dated terrestrial records are 

available. As a result, it is argued that any model of 

global climate needs to be tested against the terrestrial 

record of climate change as well as the marine record. 

The correlation of marine and terrestrial records and 

the independent dating of terrestrial records cause 

doubt about the acceptance of orbital forcing as the 

fundamental cause of climate change. This study 

reviews some of the recent contributions to that doubt. 

The interpretation of rates and magnitudes of 

future global changes needs to be put in the context of 

the geologic record. There are many possible records 

for different time scales to choose as the frame of 

reference. The widely accepted Milankovitch model of 

climatic cycles is based on orbital-forced variations in 

solar insolation. Change in the orbital geometry of the 

Earth is considered the fundamental forcing that is 

amplified by the subsequent changes in the albedo of 

the surface of the Earth and by changes in the 

concentration of greenhouse gases to produce climate 

variations (Berger and Loutre, 1992). However, as 

indicated recently by the Devils Hole 8180 record 

(Winograd and others, 1992), serious problems result 

when independently dated terrestrial records are 

compared with marine records to test the astronomicaV 

insolation models. Winograd and others ( 1992) also 

indicated that models that related isotopic variations in 

marine deposits to climatic forcing functions of regular 

periodicity, such as insolation, failed to account for 

other types of aperiodic, climatically related deposits. 

Thus, models and predictions using models need to be 

rigorously tested against observations of various types 

of stratigraphic systems. 

The accuracy and precision of model predictions 

needed to satisfy policy questions related to the 

greenhouse gas/warming issue are not improved by 

assumed or forced correlations. The precision of 

predictions can be no better than the precision of 

measurement of paleo-parameters used to validate 

models. Presently, vecy few reliable, independently 

dated, high-resolution records of climate change are 

available. Without such records, the assumed 

correlations are of little objective value. 

In the Western United States, marine and 

terrestrial Quatemacy deposits that are in close 

proximity can be compared. Theoretically, careful 

stratigraphic analysis (discussed in numerous 

contributions in this volume) should yield records that 

allow for assessment of specific climate changes and 

climatic forcing functions. In practice, however, 

fundamental differences in the response of the marine 

and terrestrial systems to climate change create 

complications in the comparison of records. 

Low-Resolution Marine Records 

Marine sediments provide a repositocy of 

climate-related records. In areas of slow sedimentation 

and anoxic conditions, such as in deeper, isolated 

basins, rhythmites or varved sediments are preserved. 

The layering of these sediments indicates passive 

settling of both calcareous and siliceous components. 

The isotopic records in these sediments contain time 

series of climate change. 

Many marine records seem to correlate, but lack, 

independent dating controls. The methods used by 

Imbrie and others (1984) and Shackelton and others 

( 1990) relied on comparing various stacked records as 

a means of correlation and validation of the orbitalforcing hypothesis. If the same sequence was seen 

repeatedly, then the original hypothesis was accepted 

to be correct; see, for example, Shackelton and others 

( 1990) who argued that the matching of stacked marine 

ABSTRACTS OF PRESENTATION 61 
records, especially the discrete sub~tages of Stage 5, 

verified the orbital forcing of variations of global ice 

volume. Shackelton and others (1990) further 

concluded that the marine record verified the 

hypothesis of orbital forcing of climate change 

described by Milankovitch ( 1930). 

The ODP site 677 in the Pacific Ocean contains 

one of the few continuous, low-latitude records of 

climate change. Shackleton and others ( 1990) 

observed in the interval of800,000 to 620,000 yr B.P. a 

transition during which the climate system changed 

from a predominant 41 ,000-yr periodicity attributed to 

obliquity forcing (Ruddiman and others, 1986) to a 

predominant I 00,000-yr periodicity associated with 

the eccentricity cycle (Imbrie and others, 1984). 

Shackelton and others ( 1990) also developed a time 

scale back to 2,600,000 yr based on the a..~sumption of 

a consistent phase relation between astronomical 

forcing and climatic (that is, ice volume) response. 

Shackelton and others ( 1990) and Hilgen ( 1991) 

concluded that time scales calculated from precession 

and eccentricity parameters provided improved dates 

of paleomagnetic time markers. For example, Imbrie 

and others (1984) had predicted the BrunhesMatuyama boundary at about 730,000 yr B.P.; 

however, the revised calculations of Shackelton and 

others ( 1990) predicted the boundary to be closer to 

780,000 yr B.P. Recent K/Ar dating of some 

paleomagnetic reversals (Baksi and others, 1992; Izett 

and Obradovich, 1992) supported the revised time 

scale derived using calculations from Shackleton and 

others ( 1990). 

The apparent synchroneity of low-resolution, 

marine-sediment records with orbital cycles is strong 

evidence that such global-scale hydrodynamic and 

isotopic responses to solar insolation variation are real. 

The question remains, however, whether tnaj or climate 

shift"i, such as glaciations, are initiated and driven by 

orbital variations. The Milankovitch theory presumes 

primary forcing by a low-magnitude variation of solar 

insolation. If correct, the climatic processes that 

respond to solar insolation variation (such as icevolume change) seem to operate through various 

amplifying feedbacks after initially responding to a 

low-amplitude (or energy) forcing. In responding to 

low-amplitude forcing, the various subsystems that 

comprise the climatic system have minimal inertia 

across gradients of heat transport (from the sun to the 

atmosphere, from the atmosphere to the ocean, and 

from low to high latitude area.~) that are all relatively 

simple in fluid media. This minimal inertia contra.."its 

markedly with the various negative feedbacks that 

apparently operated in the atmosphere, hydrosphere, 

and biosphere to keep the pre-Quaternary climate of 

the Earth fairly constant during long periods (greater 

than 108 yr) of geologic time. 

High-Resolution Marine Records 

Results from marine-terrestrial comparisons 

also produced questions about the Milankovitch model. 

A simple determinative model would predict 

synchronous changes across climatic boundaries. 

Analysis of higher resolution records casts doubt, 

however, on the existence of such synchroneity. 

Analysis of higher resolution, marine-terrestrial 

records indicated problems inherent in comparing 

tnarine-terrestrial responses to climate change. 

Gardner and others ( 1988) compared a nearshore 

continental slope record with the pollen record of Clear 

Lake, California. Comparison of these records 

indicated only a rough similarity in climate change 

during the pa.."it 20,000 yr. Correlation between the 

marine and terrestrial records required discarding 9 of 

10 14 C dates from the Clear Lake record. Attempts to 

force a correlation between the two records did not 

prove entirely satisfactory. Pollen data from the two 

cores indicated synchroneity between presumably 

coeval peaks; for example, a discrepancy of about 

2,000 yr in the ages of initial increases in Quercus and 

decreases in Pinus. Despite marine diatom and organic 

carbon evidence for upwelling of cold coastal waters 

at 15,000 yr B.P., the terrestrial stratigraphy indicated 

no increase in Sequoia, a fog-dependent tree, until 

12,000 yr B.P. At 12,000 yr B.P., there was an 

anomalous contrast of decreasing upwelling and 

increase in Sequoia. These unexplained phenomena 

indicate the problems of correlating even short 

distances of datable, high-resolution climate records. 

The same problem is well represented in comparisons 

of terrestrial records. 

Terrestrial Records 

Lacustrine 

Terrestrial lacustrine sediments, by contrast with 

marine sediments, do not often continuously record 

changes in clitnate. There may be no single lacustrine 

62 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
record that matches continuous marine records. 

Therefore, records from several basins are needed to 

compile a quasi-continuous record of sedimentation 

that allows for paleoclimatic interpretation. 

Bradbury ( 1992) published a climatic 

interpretation for the northern Great Basin (Tule Lake, 

California). He reported that the lower 100m of the 

TuleLake core (which was deposited between 

3,000,000 and 2,500,000 yr B.P.) contained diatom 

concentrations that indicated a 41 ,000-yr cycle of 

diatom productivity. He also reported a 400,000-yr 

cyclicity, similar to the eccentricity cycle, between 

2,900,000 and 1,400,000 yr B.P. During the past 

106 yr, six major peaks of diatom concentration 

occurred that were indicative of 1 00,000-yr cycles. 

Bradbury ( 1992) reported, however, that correlation 

with the marine record was untested due to the lack of 

age control in both records. 

Paleomagnetic measurements can provide an 

objective technique of testing correlations. 

Paleomagnetic measurements in the Tecopa Basin by 

E.E. Larson and others (University of Colorado, 

written commun., 1993) yielded evidence of regular 

cycles in lacustrine sediments. Larson and others 

observed a rhythmically spiked magneticsusceptibility signal (dominated by nine 41,000-yr 

periodicities) for the Olduvai Subchron {1, 700,000 to 

1,860,000 yr B.P.) that is very similar in character to the 

jagged variations in marine oxygen-isotope values. 

Above the Olduvai Subchron, E. E. Larson and 

others (written commun., 1993) found evidence for a 

strong 1 00,000-yr periodicity and lesser periods of 

40,000, 22,000, 15,000 to 16,000, 12,000, 9,000, and 

8,000 yr. Larson and others conclude that these 

periodicities are climatic and synchronous with 

astronomically forced processes. In addition, Larson 

and others compared the Tecopa Basin record with the 

record from Searles Lake (Smith, 1979, 1984; Jannik 

and others, 1991 ), stating that there was a strong 

similarity in the long-term trends in both basins. 

However, Larson and others also reported that, in these 

closely spaced basins, extended dry periods were not 

coeval; for example, Tecopa Basin was relatively dry 

from 1,600,000 to 1,000,000 yr B.P., but Searles Lake 

wa'i dry from 2,000,000 to ~ ,300,000 yr B.P. 

Jannik and others ( 1991) found some evidence of 

1 00,000-yr cyclicity in Searles Lake sediments, but 

they also found evidence for lower frequency 

variations. They reported a regular alternation of 

evaporites and muds prior to about 700,000 yr B.P., 

during which the period of lake-level fluctuations was 

approximately 50,000 yr. During the shift from 

dominance by obliquity frequency to eccentricity 

frequency reported by Shackelton and others ( 1990), 

Searles Lake fluctuations changed from approximately 

50,000 yr to a longer period. Jannik and others ( 1991) 

suggested that these fluctuations may correspond to the 

marine record, but there was not a one-to-one match 

between the Searles stratigraphy and the marine 180 

record. Moreover, Smith (1984) described a 400,000-

yr period in the major hydrologic regimes of Searles 

Lake that was not strongly expressed in the marine 

record. 

Devils Hole 

Winograd and others ( 1992) discussed the results 

from a core (DH-11) of vein calcite from Devils Hole, 

Nevada. The 500,000-yr record of paleotemperature 

contained in that well-dated core indicated that major 

deglaciations, also recorded in marine sediments and 

ice cores, do not correlate, as previously hypothesized, 

with solar insolation peaks. Specifically, Winograd and 

others ( 1992) cited convincing evidence that the major 

insolation maximum at 128,000 yr B.P. did not trigger 

a major deglaciation. Furthermore, they argued that the 

DH-11 record indicated increasing durations of glacial 

periods since 500,000 yr B.P. They stated that the 

increase in the duration of glacial periods from about 

130,000 to 80,000 yr (since the middle to late 

Pleistocene) indicated aperiodic climate shifts. The 

overall conclusion from their study was that, because 

the Milankovitch model failed to account for major 

terminations and the aperiodic duration of glacial 

periods, astronomical forcing has been overinterpreted as a control of climate change. 

Future Research Needs 

At present, the need for independent dating of 

high-resolution marine and terrestrial records cannot 

be overstressed. Process-based studies of lacustrine 

response to climate change at the scale of single 

drainage systems, such as the Owens River drainage 

studied by Jannik and others (1991), also are of high 

priority. Until basin response to climate change is 

understood, a broad picture of the various forces and 

feedbacks involved in regional- and global-scale 

clilnate cycles cannot be synthesized. The comparison 

ABSTRACTS OF PRESENTATION 63 
of records will probably continue to indicate that the 

records are different in detail. Simplistically, these 

differences indicate that global-scale changes were not 

uniformly encoded in the geologic record and that 

establishing global records from lacustrine sequences 

will be limited. However, the differences in system 

responses will be most significant in understanding the 

processes that cause change in different systems and in 

different regions of the globe. 

A promising new area of research that may 

provide more data about global geophysical process 

uses magnetic susceptibility and paleomagnetic field 

strength a~ a 1neans of correlation. Mankinen and 

Champion ( 1993) described low-dipole field strength 

for volcanic rocks from Hawaii from 40,000 to 

18,000 yr B.P., which was followed by a rapid 

rise to present strength values. Meynadier and others 

( 1992) studied the intensity variations for the past 

140,000 yr in the Somali Ba~in, where low intensities 

are recorded for long periods around 40,000 and 

115,000 yr B.P., both of which were cold periods. Tric 

and others (1992) described a halving of average field 

intensity, relative to the present, between 142,000 and 

80,000 yr B.P.--a period that contained a major cold 

(140,000 yr B.P.) period and a major warm (135,000-

120,000 yr B.P.) period. Tric and others ( 1992) also 

noted a possibly stronger field intensity at 166,000 yr 

B.P., which was another cold period. Present data are 

not sufficient to determine whether the paleointensity 

records varied in phase with climate cycles. The 

present evidence does indicate, however, that even if 

the periodicities of variation are siinilar, the directions 

of change are not consistent. 

Another intriguing, but enigmatic, observation 

from recently published paleomagnetic intensity 

measurements (Tric and others, 1992) indicates a 

qua~i-24,000-yr cyclicity. This cyclicity cannot be 

directly attributed to solar insolation and may indicate 

some other geophysical effect, such as precessional 

torque that produced cycles that miinicked solar 

insolation cycles. If further study of the paleointensity 

record does reveal a quasi-24,000-yr cyclicity, it may 

indicate that there are nonclimatic geophysical 

parameters related to orbital precession that are 

covariant with climate cycles. If so, then the solar 

insolation cycles also may be noncausally covariant 

with climate. 

Available information is insufficient to resolve 

the conflict between marine and terrestrial stratigraphy. 

Even if the marine stratigraphy were sufficient 

verification of the Milankovitch model, regional 

climatic models for land areas siinply cannot be 

generated using present understanding. Many 

independently dated terrestrial records need to be 

studied to gain a better understanding of the processes 

that alter climate-related sediment characteristics. An 

example of the simplicity of misinterpretation is the 

early interpretations of the correlation between 

paleomagnetic intensity of sediment'i and isotopic 

con1position of sediment'i (Oldfield and Robinson, 

1985). Without more detailed analysis, researchers 

would have been satisfied with the conclusion that 

variations of magnetic field intensity were a cause of 

paleoclhnate variability. When numerous parameters 

correlate, noncorrelative systems are needed to test the 

models and to test ideas about causality in complex 

feedback systems. The sometimes tedious process of 

recovering and analyzing numerous terrestrial records 

can provide critical tests of climate models. 

64 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
REFERENCES 

Baksi, A.K., Hsu, V., McWilliams, M.O., and Farrar, E., 1992, 40Ar/39 Ar dating ofthe Brunhes-Matuyama geomagnetic field 

reversal: Science, v. 256, no. 5055, p. 356--357. 

Berger, A., and Loutrc, M.F., 1992, Astronomical solutions for paleoclimate studies over the last 3 million years: Earth and 

Planetary Science Letters, v. 111, p. 369-382. 

Bradbury, J.P., 1992, Late Cenozoic lacustrine and climatic environments at TuleLake, northern Great Basin, USA: Climate 

Dynamics, v. 6, p. 275-285. 

Gardner, .T.V., Heusser, L.E., Quintemo, R..T., Stone, S.M., Barron, .J.A., and Poore, R.Z., 1988, Clear Lake record vs. the 

adjacent marine record; a correlation of their past 20,000 years of paleoclimatic and paleooceanographic responses, in 

Sims, J.D., ed., Late Quaternary climate, tectonism, and sedimentation in Clear Lake, northern California Coast Ranges: 

Geological Society or America Special Paper 214, p. 171-182. 

Hilgen, F.J., 1991, Astronomical calibration of gneiss to Matuyama sapropels in the Mediterranean and implication for the 

geomagnetic polarity time scale: Earth and Planetary Science Letters, v. 104, p. 228--244. 

Imbrie, John, Hays, J.D., Martinsm, D.G., Mcintyre, Andrew, Mix, A.C., Morley, .T..J., Pisias, N.G., Prell, W.L., and 

Shackelton, N.J., 1984, The orbital theory orPleistocene climate--Support from a revised chronology ofthe marine 8180 

record, in Berger, A., Imbrie, John, Hays, J.D., Kukla, G., and Saltzman, B., eds, Milankovitch and climate: Norwell, 

Mass., D. Reidel, p. 269-305. 

lzett, G.A., and Obradovich, J.D., 1992, 40Ar-39 Ar dating of the Jaramillo nonnal subchron and the Matuyama and Brunhes 

geomagnetic boundary: U.S. Geological Survey Open-File Report 92-699, 22 p . 

.Tannik, N.O., Phillips, F.M., Smith, G.I., and Elmore, D., 1991, A 36Cl chronology of lacustrine sedimentation in the 

Pleistocene Owens River system: Geological Society of America Bulletin, v. 103, no. 9, p. 1146--1159. 

Mankinen, E.A., and Champion, D.E., 1993, Latest Pleistocene and Holocene geomagnetic paleointensity on Hawaii; 

comparison with the global record: Science, v. 262, p. 412-416. 

Meynadier, L., and others, 1992, Relative geomagnetic intensity of the field during the last 140 Ka: Earth and Planetary 

Science Letters, v. 114, p. 39-57. 

Milankovitch, M., 1930, Mathematische Klimalchre and astronomische theorie der Klimaschwan Kungen, in Handbuch der 

klimatologic: Berlin, Bd 1, Teil A, 1765 p. 

Oldfield, Frank, and Robinson, S.G., 1985, Geomagnetism and paleoclimate, in Tobey, M . .T., and Sheai1, S.M., eds., The 

climate scene: Boston, Allen, and Unwin, p. 185-205. 

Ruddiman, W.F., Mcintyre, Andrew, and Raymo, M.E., 1986, Matuyama 41 ,000-year cycles-North Atlantic Ocean and 

northern hemisphere icc sheets: Earth and Planetary Science Letters, v. 80, p. 117-129. 

Shackelton, N.J., Berger, A., and Peltier, W.R., 1990, An alternative astronomical calibration of the lower Pleistocene 

time scale based on ODP Site 677: Transactions of the Royal Society of Edinburgh, Earth Sciences, v. 81, p. 251-261. 

Smith, G.I., 1979, Subsurface stratigraphy and geochemistry of late Quaternary evaporites, Searles Lake, California, with a 

section on Radiocarbon ages of stratigraphic units, by Minze Stuiver, and G.I. Smith: U.S. Geological Survey 

Professional Paper 1043, 130 p. 

ABSTRACTS OF PRESENTATIONS 65 
__ 1984, Paleohydrologic regimes in the southwestern Great Basin, 0--3.2 my ago, compared with other long records of 

"global" climates: Quaternary Research, v. 22, no. 1, p. 1-17. 

Tric, E., and others, 1992, Paleointensity of the geomagnetic field during the last 80,000 years: Journal of Geophysical 

Research, v. 97, p. 9337-9351. 

Winograd, I.J., Coplen, T.B., Landwehr, J.M., Riggs, A.C., Ludwig, K.R., Szabo, B.J., Kosesau, P.T., and Revesz, K.M., 1992, 

Continuous 500,000-year climate record from vein calcite in Devils Hole, Nevada: Science, v. 258, no. 5080, p. 255-260. 

66 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Calcium Carbonate Formation in Pyramid Lake, Nevada 

Michael M. Reddy, U.S. Geological Survey 

Calcium carbonate (CaC03) mineral formation 

occurs in numerous, temperate hardwater lakes of the 

United States. Carbonate minerals may serve as 

paleoclimate records if, a'i the minerals form, trace 

elements and certain isotopes are incorporated in 

amount'i reflecting environmental conditions of the 

surrounding lake water. Well-studied lakes having this 

phenomenon include Fayetteville Green Lake and 

Onondaga Lake, both located near Syracuse, New 

York. Pyramid Lake in Nevada, in contralit, has unique 

physical and chemical characteristics that modify inlake calcium carbonate formation processes from those 

observed in the lakes in New York (Galat and others, 

1981; Benson and others, 1990; Benson, 1993 ). Some 

of these modifications include: ( 1) The occurrence of 

large carbonate mounds in the nearshore region of 

Pyramid Lake (Benson, 1993 ), which are not usually 

found in more humid environment'i; (2) the formation 

of a less stable form of calcium carbonate (aragonite) 

rather than the thermodynamically stable polymorph, 

calcite (Galat and Jacobsen, 1985); and (3) the 

occurrence of calciutn carbonate precipitation episodes 

(termed ""whitings") in the Pyramid Lake water column 

(Galat and Jacobsen, 1985). 

These modifications indicate that calcium 

carbonate precipitation in Pyramid Lake is affected by 

chemical factors that control calcium carbonate 

supersaturation levels and carbonate mineral growth 

rates (Nancollas and Reddy, 1971; Reddy, 1975, 1978, 

1986; Reddy and Nancollas, 1976; Reddy and Wang, 

1980; Reddy and Gaillard, 1981; Reddy and others, 

1981 ). Laboratoty and in-lake calcium carbonate 

formation studies at Pyramid Lake arc in progress to 

test this hypothesis. Field studies ofcalciwn carbonate 

formation in Pyramid Lake were initiated in the 

summer of 1992; laboratoty studies of calcium 

carbonate formation are continuing. 

Calcium carbonate fonnation in a test tube or a 

lake is frequently initiated by ctystal nucleation 

involving formation of unstable polymorphs and 

hydrates (Reddy and Nancolla~, 1976; Reddy, 1986). 

Calcium carbonate nucleation rates, which differ 

among these polyn1orphs and hydrates, increase with 

increasing calcium carbonate supersaturation. 

Supersaturation is defined as the ratio of calcium 

carbonate ion-activity product to the calcium carbonate 

(calcite) solubility product (Reddy, 1986). The 

sensitivity of nucleation rates to calcium carbonate 

supersaturation confounds attempts to predict the onset 

and duration of calcium carbonate formation episodes 

in Pyramid Lake (Galat and Jacobsen,1985). 

At a fixed calcium carbonate supersaturation 

level, water temperature and concentration of certain 

ions (termed "inhibitors") can affect carbonate mineral 

polymorphic composition and formation rates (Reddy, 

1977, 1978). Following nucleation, or in the presence 

of a suitable growth surface, calcium carbonate 

tninerals may form from a supersaturated solution. 

Calcite formation under such conditions follows a 

parabolic growth-rate equation (Reddy, 1986). This 

equation relates the ctystal growth rate to the product 

of three terms: the growth surface available for 

reaction, the ccystal growth-rate constant, and the 

square of the reaction driving force. 

Inhibitor ions reduce carbonate mineral growth 

rates and usually do not modify the reaction driving 

force (that is, the solution supersaturation). It is 

recognized that carbonate-ctystal-growth inhibitors 

regulate mineral formation in Great Basin lakes such as 

Mono Lake and Pyramid Lake. Inhibitor-ion 

concentration levels also may have modified carbonate 

mineral formation in paleoenvironments. 

Calcite ctystal growth rates are reduced in the 

presence of millimole to micromole concentrations of 

magnesium and phosphate ions. In Pyramid Lake, 

concentration of these ions were sufficient to decrease 

calcite formation rates in the supersaturated lake water 

(Reddy, 1975). Magnesium-ion and phosphate-ion 

inhibition of calcite ctystal growth was interpreted in 

terms of a Langmuir adsorption isotherm model. This 

model assumes that inhibitor ions adsorb at ctystal 

growth sites on the calcite surface (Reddy, 1977, 1978, 

1986). 

A test of the proposed calcium carbonate 

formation mechanism in Pyramid Lake, using an inlake ctystal growth experiment, was begun in the 

ABSTRACTS OF PRESENTATION 67 
summer of 1992. This test measured calcite and 

aragonite crystal growth rates for single crystals 

suspended in Pyramid Lake. Initial results from 

August and September 1992 (no growth in the 

REFERENCES 

supersaturated lake water) indicated the importance of 

crystal growth inhibitors, such as magnesium and 

phosphate ions, in calcium carbonate formation in 

Pyramid Lake. 

Benson, L. V., 1993, Factors affecting C-14 ages of lacustrine carbonates--Timing and duration of the last highstand lake in 

the Lahontan Basin: Quaternary Research, v. 39, no. 2, p. 163-174. 

Benson, L.V., Currey, D.R., Dorn, R.I., Lajoie, K.R., Oviatt, C.G., Robinson, S.W., Smith, G.I., and Stine, S., 1990, 

Chronology of expansion and contraction of four Great Basin lake systems during the past 35,000 years, in Meyers, P.A., 

ed., Paleoclimates; the record from lakes, ocean and land: Palaeogeography, Palaeoclimate, Palaeoecology, v. 78, 

no.3-4,p.241-286. 

Galat, D.L., and Jacobsen, R.L., 1985, Recurrent aragonite precipitation in saline-alkaline Pyramid Lake, Nevada: Archives 

ofHydrobiology, v. 105, no. 2, p. 137-159. 

Galat, D.L., Lider, E.L., Vigg, S., and Robertson, S.R., 1981, Limnology of a large, deep North American terminal lake, 

Pyramid Lake, Nevada, U.S.A: Hydrobiologia, v. 82, no. 81-82, p. 281-317. 

Nancollas, G.H., and Reddy, M.M., 1971, The crystallization of calcium carbonate--II, Calcite growth mechanism: Journal 

of Colloid Interface Science, v. 3 7, no. 4, p. 824-830. 

Reddy, M.M., 1975, Kinetics of calcium carbonate formation: Proceedings ofthe International Association of Theoretical 

and Applied Limnology, v. 19, pt. 1, p. 429-438. 

__ 1977, Crystallization of calcium carbonate in the presence of trace concentrations of phosphorus-containing anions--

I, Inhibition by phosphate and glycerophosphate ions at pH 8.8 and 25°C: Journal of Crystal Growth, v. 41, no. 2, 

p. 287-295. 

__ 1978, Kinetic inhibition of calcium carbonate formation by wastewater constituents, in Rubin, A.J., ed., Chemistry of 

wastewater technology: Ann Arbor, Mich., Ann Arbor Science Publishers, Inc., p. 31-58. 

__ 1986, Effect of magnesium ion on calcium carbonate nucleation and crystal growth in dilute aqueous solutions at 

25° Celsius, in Studies in diageneses: U.S. Geological Survey Bulletin 1578, p. 169-182. 

Reddy, M.M., and Gaillard, W.D., 1981, Kinetics of calcium carbonate (calcite)-seeded crystallization-The influences of 

solid-solution ratio on the reaction constant: Journal of Colloid Interface Science, v. 80, no. 1, p. 171-178. 

Reddy, M.M., and Nancollas, G.H., 1976, The crystallization of calcium carbonate-IV, The effect of magnesium, strontium, 

and sulfate ions: Journal of Crystal Growth, v. 35, no. 1, p. 33-38. 

Reddy, M.M., Plummer, L.N., and Busenberg, E., 1981, Crystal growth of calcite from calcium bicarbonate solutions at 

constant carbon dioxide partial pressures and 25 degrees C-A test of a calcite dissolution model: Geochemica et 

Cosmochimica Acta, v. 45, no. 8, p. 1281-1289. 

Reddy, M.M., and Wang, K.K., 1980, Crystallization of calcium carbonate in the presence of metal ions--Inhibition by 

magnesium ion at pH 8.8 and 25 deg C: Journal of Crystal Growth, v. 50, p. 470-480. 

68 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Climate of the Great Basin 

Kelly Redmond, Western Regional Climate Center, 

Desert Research Institute, Reno, Nevada 

The climate of the Great Basin is characterized 

primarily by aridity. The Great Basin is dry in two 

senses: precipitation is low, and the absolute and 

relative humidities of the air are low. The Great Basin 

is physically separated from potential oceanic moisture 

source regions by distance and mountains. In addition 

to mountains around the periphery, about 150 mountain 

ranges, separated by basins, occupy the interior of the 

basin. Because heavier and more frequent 

precipitation occurs in the vicinity of the mountains, 

most of the precipitation received in the basin falls 

over a relatively small fraction of the total horizontal 

area. Annual precipitation ranges from approximately 

140 em on mountain tops in the western part of the 

basin to 3 to 4 em in Death Valley and vicinity. 

The seasonal precipitation cycle indicates 

systematic variations with latitude/longitude position 

and with elevation. Houghton (1969) has identified the 

chief seasons that contribute most to the annual total 

precipitation at different points in the region. In the 

northern end of the basin, Hanson ( 1982) has used the 

dense network at Reynolds Creek near Boise, Idaho, to 

show that winter accounts for a successively greater 

fraction of annual precipitation as elevation increases. 

At that location, December-February precipitation 

accounts for about 43 percent of the annual total at 

1,200 m and about 58 percent at 2,100 m. 

The frequency of precipitation days (those days 

with at least 0.025 em of precipitation) ranges from 

about 90 days per year at Boise and Salt Lake City to 

about 11 days at Lathrop Wells, Nevada. The drier the 

location, the greater the fraction of the annual 

precipitation that falls during the wettest few days. 

Despite the general aridity, water is a prime element in 

landscape alteration. Flash floods, although infrequent, 

leave their imprint for many decades. In many ways, 

climatic events lasting a few hours to a few days can be 

as important for long-term change as anomalies that 

persist for a month or longer. 

The main influences on the annual cycle of 

precipitation amount and frequency are the sea~onal 

expansion and contraction of the westerlies, the 

formation of low pressure systems in the Great Basin 

during the transition months, and the southwest 

monsoon in the summer. Specific locations have from 

one to four precipitation peaks within the year, each 

ascribable to a different cause. Each cause produces a 

certain typical component, so that the seasonal cycle at 

most locations can be described as a superposition of 

these main components, each with different weights. 

Houghton ( 1969) also used this notion in trying to 

account for the variety of annual patterns observed in 

the region. 

The lack of precipitation measured at the surface 

is a reflection not only of a decreased frequency of 

water-bearing clouds, but also of the low atmospheric 

humidity. Convective clouds often have very high 

bases-also an effect of the low humidity--so that 

precipitation falls through thousands of meters of dry 

air, allowing ample opportunity for evaporation before 

reaching the valley floor. Precipitation falling onto 

mountains has a much smaller distance in which to 

evaporate, so a greater fraction of the precipitation 

leaving a cloud reaches the surface in mountainous 

locations. 

In ecological and climatological terms, the 

numerous mountain ranges can be thought of as 

"islands" rising from the valley floors. Long-term 

climate measurements at elevated sites are extremely 

difficult to obtain, so that existing data sets tend to be 

dominated by data from inhabited locations, which 

severely impairs the ability to map climate elements 

adequately. The combination of modeling, remote 

sensing, and automated observations is increasingly 

being applied to the difficult problem of interpolation, 

which needs to be solved before mapping can proceed. 

In the broadly elevated parts of the region, the 

dry soil and atmosphere result in large diurnal 

temperature ranges. Freezing temperatures are 

possible throughout the year in higher b~ins, and 

much of the region has a large number of freeze-thaw 

cycles. Somewhat protected by the Rocky Mountains 

and southerly enough to receive substantial solar 

energy in winter, the region seldom has extremely cold 

temperatures ( -15°C or less) and almost never has low 

temperatures accompanied by wind. 

ABSTRACTS OF PRESENTATION 69 
Shallow temperature inversions are very 

common, and the Great Basin region would be very 

susceptible to air pollution if the population were 

larger. Persistent regimes of high pressure can 

result in extended periods of stagnant cold air in the 

REFERENCES 

cool season. The resulting decreases in visibility 

are easily noticeable because the air is among the 

cleanest in the United States. Visibilities of 

150 km or more are frequent in eastern 

Nevada. 

Hanson, C.L., 1982, Distribution and stochastic generation of annual and monthly precipitation on a mountainous watershed 

in southwest Idaho: Water Resources Bulletin, v. 18, no. 5, p. 875-883. 

Houghton, J.G., 1969, Characterization ofrainfall in the Great Basin: Reno, Desert Research Institute, 205 p. 

70 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Climatic Control of Late Quaternary Sedimentation on the 

Leidy Creek Fan in Fish Lake Valley, Nevada-CaliforniaImplications for Geomorphic Processes in Semiarid Climates 

Marith C. Reheis and Constance K. Throckmorton, US. Geological Survey 

A critical question in arid-land geomorphology 

has been debated for decades: Does sedimentation 

occur on alluvial fans when the climate is cool 

(effectively wet), in transition from cool to warm, or 

warm (effectively dry)? This question has never been 

adequately answered due to a general lack of datable 

material in alluvial-fan deposits. However, Slate 

( 1992, this volume) has recently suggested that pulses 

of Holocene deposition on proximal fans in Fish Lake 

Valley commonly correspond to periods of warm 

climate or to transitions from cool to warm climate. 

Extensive mapping and dating and some coring 

of proximal- and distal-fan deposits and adjacent marsh 

and peat deposits on the Leidy Creek fan in Fish Lake 

Valley in west-central Nevada and adjacent California 

provide unequivocal evidence that fan deposition in the 

Holocene was extensive and indicates that soils were 

forming on stable fan surfaces that had no debris-flow 

deposition during the late middle Wisconsin in this 

valley. Cores from the peat deposits, present in a 

narrow band from the location of core 1 to just north 

of the location of core 7 along the east edge of the 

marsh deposits (fig. 1 ), is yielding a detailed record of 

late Wisconsin and Holocene climate, based on 

analyses of pollen, diatoms, ostracods, and stable 

isotopes. This research has significant implications for 

geomorphic processes and regional climate patterns. 

Proximal-fan deposits are well exposed in 

fanhead trenches and incised fault scarps along the 

White Mountains on the west side ofFish Lake Valley 

in the Leidy Creek drainage (fig. 1) and throughout 

Fish Lake Valley. The deposits consist mostly of 

superposed, matrix-supported, bouldery debris flows 

(Slate, 1992). Based on surface and soil 

characteristics, the deposits have been subdivided into 

units of late Pleistocene and early, middle, and late 

Holocene age (older depositfi also are abundant 

elsewhere in the valley). The. Holocene units are the 

most extensive and merge downfan with fine-grained 

distal-fan alluvium and valley fill. These units in 

figure 1 have been simplified from those in Reheis and 

others (1993, in press). The ages of the mapping units 

actually span only parts of the time intervals by which 

they are identified in figure 1 (for example, middle 

Holocene). The combined units show areas where 

deposits of distinctly different ages were combined for 

convenience, and the upper Holocene unit (fig. 1) 

includes two mapped units of different ages. The upper 

Pleistocene unit is only well exposed along the range 

front and is mostly buried by Holocene deposits to the 

east, but can locally be traced several kilometers 

downfan (fig. 1 ). 

The exposed Holocene units have been dated in 

many parts of the valley by using 14C analysis of 

charcoal and buried logs and by tephrochronology. 

These ages clustered into groups that indicated 

intervals of debris-flow deposition throughout the 

valley separated by intervals of nondeposition (Slate, 

1992, this volume; Reheis and others, 1993, in press). 

Despite the abundance of datable material (more than 

20 14C ages and more than 20 correlated tephra layers), 

no ages have been obtained from the proximal-fan 

deposits that are older than 6,850 yr B.P. (the Mazama 

ash). However, a few late Pleistocene ages (35,000--

10,000 yr B.P.) have been obtained from alluvium that 

probably accumulated behind a landslide within the 

White Mountains. 

The age of the upper Pleistocene unit is not so 

well determined, but based on a thermoluminescence 

age (Slate, 1992), a beryllium-I 0 age estimate 

(M.J. Pavich, U.S. Geological Survey, written 

commun., 1993), and identification oftwo tephra 

layers (A.M. Sarna-Wojcicki, U.S. Geological Survey, 

written commun., 1992), it is no younger than about 

35,000 yr and probably no older than 100,000 yr. 

Seven cores from 9 to 13m long were obtained 

in 1991 from the distal part of the Leidy Creek fan, 

including 2 cores (cores 1 and 7) from a peat bog at the 

toe of the fan and another core (core 2) from adjacent 

marsh deposits (fig. 1 ). These cores were intended to 

provide a climatic and a stratigraphic record to 

investigate the relation of fan sedimentation to climate 

and to correlate to the sedimentation record provided 

ABSTRACTS OF PRESENTATION 71 
118°05' ......... ....... . . ......... ...... . ................. 

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

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

················· ................. 

················· 

................. ················· 

················· 

················· 

················· 

················· 

················· 

················· 

················· 

················· 

················· 

················· 

················· 

················· 

················· 

-~7?:-~-~-~~ ················· 

················· 

················· 

················· 

················· 

:*::::::::::::::: 

················· 

0 3 

0 2 MILES 

EXPLANATION NEVADA 

ALLUVIAL-FAN UNITS OTHER UNITS 

t .... 'i ..... HOLOCENE (UNDNIDED) MARSH DEPOSITS 

(HOLOCENE) 

········· 

1 ......... 1 

UPPER HOLOCENE DUNE DEPOSITS 

(UPPER HOLOCENE) 

I I MIDDLE HOLOCENE l : : : : : : :I BEDROCK 

LOWER HOLOCENE ---CONTACT 5 l<o>',<ol $ COREHOLE :0000 00 0:000 

- UPPER PLEISTOCENE 

...--- ' · · · · FAULT -Bar and ball on downthrown 

side; arrows, strikeslip motion; 

dotted where buried 

• CARBON-14 SAMPLE SITE 

* TEPHRA SAMPLE SITE 

Figure 1. Generalized geologic map of Leidy Creek fan and vicinity in Fish Lake Valley showing locations of core holes 

and exposed age-control sites. 

by the exposed proximal-fan deposits. Cores 1 and 7 

are similar; both have about 5.5 m of peat and organicrich silt and clay overlying about 2.0 m of fluvial, wellsorted, clean pebbly sand that, in turn, overlies finegrained deposits. In core 1, these basal deposits are 

poorly sorted, pebbly sand and silt containing 

interbedded silty clay layers, whereas in core 7, the 

basal deposits are mostly stiff, green, silty clay. Core 2 

consists mostly of locally organic-rich, calcareous silt 

and clay. 

Cores 3 through 6, on the distal fan, indicate 

coarsening trends upward in each core and in an up fan 

direction. Each core contains three weak buried soils 

in the upper few meters; these buried soils are closely 

spaced in core 3, but are separated by sediment layers 

that thicken upfan. A backhoe trench, excavated 

0. 5 km southwest of core 5 to a depth of 5 m (fig. 1 ), 

also exposed three weak buried soils. In addition, cores 

2 through 6 contain a strong buried soil characterized 

by an organic A horizon about 10 to 30 em thick, a Bt 

or Bw horizon as much as 20 em thick, and a Bk 

horizon at least 30 em thick and containing 15 to 50 

percent CaC03. The depth to the top of this buried soil 

gradually increases up fan from about 4.6 m in core 2 to 

about 11.5 min core 6. 

Eighteen 14C and tephra ages on material from 

cores 1 and 7 indicate that organic-matter accumulation 

has been continuous since about 12,500 yr B.P. A 

single 14C age of 24,240 ± 330 yr B.P. was obtained 

from the fine-grained sediment about 1 m below the 

base of the fluvial sand in core 1. Four 14C ages from 

72 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
cores 2, 3, and 4 constrain the age of the strong buried 

soil. Three samples from the A horizon (meanresidence time ages) were dated at 9,630 ± 80, 

8,900 ± 80, and 9,900 ± 80 yr B.P., respectively; the 

fourth sample wa.."i from organic-rich clay about 50 em 

above the buried soil in core 2 and was dated at 

8,810 ± 80 yr B.P. 

Preliminary interpretation of the 14C ages, tephra 

correlations, and stratigraphic relations yielded the 

following conclusions and speculations: 

1. Organics accumulated relatively rapidly in cores 1 

and 7 between about 11,000 to 10,000 and 

8,000 yr B.P. and between about 4,000 and 

2,000 yr B.P. and accumulated slowly between 

about 7,000 and 4,000 yr B.P. 

2. Beginning at about 8,900 yr B.P., the fan was 

aggrading by debris-flow and distal-fan 

sedimentation; the thickness of these 

sediment"i decreases downfan from about 

11.5 to 5.5 m. Thus, the Holocene has been a 

time of rapid fan sedimentation. However, the 

weak buried soils in the upper parts of the 

distal-fan cores indicate that deposition rates 

were slower in the middle(?) to late Holocene 

than in the early Holocene. 

REFERENCES 

3. Prior to about 12,000 yr B.P., the climate was 

effectively wet enough that an axial stream 

(represented by the fluvial deposits beneath the 

peat in cores 1 and 7) flowed at the toe of the 

fan. Deposit" of this age on the fan, however, 

are represented by the strong buried soil. Thus, 

debris-flow deposition was limited or absent, 

and slopes were stable, presumably because 

the climate was moist enough to increa.."ie the 

vegetative cover. 

4. At and before 24,000 yr B.P., a small, shallow lake 

· may have existed at the toe of the fan, based on 

the fine-grained deposits beneath the fluvial 

unit. If this lake existed, it was probably small 

because there are no preserved shorelines and 

because similar sediments do not occur at the 

same depth in core 3, located only about 1 km 

up fan from core 1. 

The development of the strong buried soil 

present in most of the cores may have required several 

tens of thousands of years. lfthe interpretations are 

correct, then the Leidy Creek fan (and, by extension, 

other fans in Fish Lake Valley) was stable and had no 

deposition during the middle(?) and late Wisconsin, 

when the climate wa.."i relatively wet. 

Reheis. M.C., Sawyer, T.L.. Slate, J.L.. and Gillespie, A.R., 1993, Geologic map of late Cenozoic deposits and faults in 

the southern part of the Davis Mountain 15' quadrangle, Esmeralda County, Nevada: U.S. Geological Survey 

Miscellaneous Investigations Series Map 1-2342, scale 1:24,000. 

Rchcis. M.C., Slate, J.L., and Sawyer, T.L.. in press. Geologic map oflate Cenozoic deposits and faults in parts of the 

Mount Barcrotl, Pipes Peak, and Soldier Pass 15' quadrangles. Esmeralda County, Nevada, and Mono County, 

California: U.S. Geological Survey Miscellaneous Investigations Series Map 1-2464. scale 1:24,000. 

Slate, J.L.. 1992, Quaternary stratigraphy, geomorphology, and geochronology of alluvial fans, Fish Lake Valley, Nevada 

and California: Boulder, University of Colorado, Ph.D. dissertation, 241 p. 

ABSTRACTS OF PRESENTATION 73 

Spatial and Temporal Variation in Nitrogen Fixation in 

Pyramid Lake, Nevada 

Cathryn L. Rhodes, John E. Reuter. Martin E. Lebo, and Charles R. Goldman, 

Division o.f Environmental Studies, University of Ca/(fornia, Davis 

Introduction 

Although generally considered oligotrophic 

(Galat and others, 1981 ), Pyramid Lake in Nevada has 

large summer-fall blooms of the nitrogen-fixing 

cyanobacterium Nodularia spumigena. Near the 

bloom peak, surface chlorophyll a concentration 

increases from an average epilimnetic value of 

3.3 mg/L to as much as 100 mg/L at the surface. 

The size of the Nodularia bloom varies 

dramatically from year to year. Although Nodularia is 

always a major nitrogen source in Pyramid Lake 

(Home and Galat, 1985), the mass of nitrogen fixed 

annually by the bloom varies by two orders of 

magnitude. During the vety large 1992 bloom, 

approximately 1,000 metric tons of nitrogen were 

fixed, accounting for 94 percent of the total annual 

nitrogen budget. Even during the small 1991 bloom, 

approximately 90 metric tons of nitrogen were fixed, 

accounting for 60 percent of the annual nitrogen 

budget. Home and Galat ( 1985) reported that 866 

metric tons of nitrogen were fixed during the 1979 

bloom, accounting for 81 percent of the annual 

nitrogen budget. 

Spatial and temporal heterogeneity of the blooms 

complicates assessment of nitrogen fixation by 

Nodularia. The dense surface scums that characterize 

Nodularia blooms in Pyramid Lake may occur anytime 

between July and October (Galat and others, 1990). 

Horizontal patchiness of the blooms is reflected in the 

surface chlorophyll concentrations. On any date 

during a bloom, surface chlorophyll may vary spatially 

by two to five orders of magnitude. Because of the 

spatial and temporal heterogeneity characteristic of 

these blooms, a multiple synoptic-sampling approach 

provided the best assessment of nitrogen fixation. In 

addition to providing a good estimate of the nitrogen 

budget, the multiple synoptic approach allowed the 

examination of the spatial and temporal patterns of 

nitrogen fixation in Pyramid Lake. 

Study Site 

Pyramid Lake is located in the Great Basin 

Desert approximately 100 km north of Reno, Nevada. 

The lake is the terminus of the Lake Tahoe-Truckee 

River watershed. Pyramid Lake is deep, having a 

maximum depth of 105 m and an average depth of 

59 m (Galat and others, 1981). The lake is nitrogen 

poor and phosphorus rich. Generally, epilimnetic 

dissolved-inorganic nitrogen averages less than 

10 tng/L during the summer, whereas dissolvedinorganic phosphorous concentrations average greater 

than 60 mg/L. Pyramid Lake is hyposaline 

(3,500 mg/L) and alkaline (9.4 pH). 

Materials and Methods 

Surface synoptic sampling was conducted 

approximately weekly during the 1991 and 1992 

Nodularia blooms. Acetylene reduction was used to 

assess nitrogenase activity and was assumed to be 

proportional to nitrogen fixation. Acetylene-reduced 

samples were incubated the day after the synoptic 

sampling for 2 hours across solar noon. Incubations 

were conducted in onshore flow-through incubators 

under ambient light conditions. At the end of the 

incubations, acetylene-reduction bottles were shaken, 

and the headspace gases were injected into 

Vacutainers. The galii samples were analyzed using a 

flatne-ionization-detector-equipped gas 

chromatograph fitted with a Porpak N column. 

Chlorophyll samples were stored frozen until 

extraction using alkaline acetone and fluorometric 

determination. 

Results 

Surface acetylene-reduction rates and 

chlorophyll concentrations were spatially and 

temporally heterogeneous during 1991 and 1992. 

Acetylene reduction was first detected during the 

2-yr study on August 28, 1991, and on July 27, 1992. 

The onset of the 1991 Nodularia bloom was aliisociated 

ABSTRACTS OF PRESENTATION 75 
with the decrease in wind speed in early August, and 

the bloom peaked around September 5, 1991. 

Nodularia appeared a month earlier in 1992 than in 

1991. Although the beginning of the 1992 bloom waf.i 

not associated with a drastic wind-speed change, the 

average wind speed during summer 1992 was similar 

to the average wind speed during the 1991 bloom. 

Acetylene-reduction rates and chlorophyll 

concentrations during the 1991 bloom were 2 to 

2,000 (nmol/L)/hr and 0.5 to 13 J..tg/L, whereas during 

the 1992 bloom, these parameters ranged from 0.6 to 

30,500 (nmol/L)/hr and 1 to 433 J..tg/L. The acetylenereduction rates and the chlorophyll concentrations 

indicated the dramatic size difference between the 

1991 and the 1992 Nodularia blooms. Collapse of the 

1991 and the 1992 blooms coincided with an increa~e 

in wind speed. 

In addition to the wide variation in acetylenereduction rates and in chlorophyll concentrations, the 

chlorophyll-specific acetylene-reduction rate varied 

by five orders of magnitude. Although the variation 

wa..~ not a~sociated with sampling date or with station, 

the variability in chlorophyll-specific acetylene 

reduction during 1992 was greater than in 1991. Most 

of the variability occurred at low chlorophyll values 

(<5 J..tg/L). 

The spatial patterns in acetylene-reduction rates 

and in chlorophyll concentrations were analyzed using 

multidimensional scaling. Before analysis, all values 

were standardized within sampling date by subtracting 

the mean and dividing by the standard deviation. The 

station interrelations mapped in a two-dimensional 

ordination using multidimensional scaling indicated a 

north-south spatial pattern in acetylene-reduction rates. 

REFERENCES 

In contra~t, no similar pattern was detected in the 

chlorophyll concentrations. Based on Landsat images 

of Nodularia blooms (Galat and others, 1990), a 

pattern indicting the concentration of algal material 

along the west-central shore of Pyramid Lake was 

expected. Neither the standardized acetylenereduction rates nor the standardized chlorophyll had a 

pattern consistent with this nearshore distribution. 

Conclusions 

The timing and magnitude of the annual 

Nodularia spumigena bloom in Pyramid Lake is 

related to wind speed. The large, early-1992 bloom 

occurred during a low wind-speed year, whereas the 

small, late-1991 bloom occurred during a calm period 

in an otherwise windy year. The inverse relation of 

wind speed to bloom size implies that water-column 

stability affects the size of the yearly bloom. There is 

no consistent relation of the rate of nitrogen fixation to 

chlorophyll concentration. Because the chlorophyllspecific nitrogen-fixation rate is variable, estimates of 

nitrogen fixed by Nodularia based on chlorophyll 

concentration may be inaccurate. The station 

interrelations mapped in a two-dimensional ordination 

using multidimensional scaling indicated a north-south 

spatial pattern in acetylene-reduction rates. This 

pattern is consistent with wind-direction data from 

Sutcliffe, Nevada, that indicated prevailing north 

winds during the summers of 1991 and 1992. A similar 

analysis based on chlorophyll concentrations did not 

indicate a comparable spatial pattern. 

Galat, D.L., Lider, E.L., Vigg, S., and Robertson, S.R., 1981, Limnologyofa large, deep, North American terminal lake, 

Pyramid Lake, Nevada, U.S.A.: Hydrobiologia, v. 82, p. 281-317. 

Galat, D.L., Verdin, J.P., and Sims, L.L., 1990, Large-scale patterns of Nodularia spumigena blooms in Pyramid Lake, 

Nevada, determined from Landsat imagery-1972-1986: Hydrobiologia, v. 197, p. 147-164. 

Horne, A.J., and Galat, D.L., 1985, Nitrogen fixation in an oligotrophic, saline desert lake-Pyramid Lake, Nevada: 

Limnology and Oceanography, v. 30, no. 6, p. 1229-1239. 

76 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Middle Holocene Decrease in the Surface Level of Lake Tahoe, 

Nevada and California 

Martin Rose, Biological Sciences Center, Desert Research Institute, Reno, Nevada 

Susan Lindstrom, Archaeologist, Truckee, Cal!fornia 

Submerged tree stumps in Lake Tahoe, dating 

6,300 to 5,000 cal (calibrated) yr B.P., document an 

interval of lower lake level. Three hypotheses can be 

offered to account for this phenomenon. The first and 

probably most obvious hypothesis is that a period of 

aridity caused the lake level to drop. The forest 

surrounding the lake gradually followed the lake 

surface to a lower elevation. Approximately 5,000 yr 

B.P., a return to more mesic conditions caused the lake 

to rise and kill the trees, some of which are still 

preserved in the cold water. A second hypothesis is 

that sediments were deposited over the natural sill 

during a period of decreased outflow that is related to a 

regional drying trend. The sediment accumulation 

over the sill functioned as a dam, causing the lake level 

to rise, resulting in the death of trees that becatne 

submerged. A third hypothesis is that a structural rise 

in the sill or subsidence at the south end of the basin, or 

both, resulted in the death of trees that were submerged 

(Harding, 1965). 

Lake Tahoe, averaging a depth of302 m, is 

believed to be the 1Oth deepest lake in the world and 

the 3d deepest in the United States. Its maximum depth 

is about 503 m. The total drainage area that is tributary 

to the lake is 1,310 km2

; the lake itself occupies 497 

km2

• With an average surface elevation of 1,897 m, it 

is the highest lake of its size in the United States. Lake 

Tahoe occupies a graben, a steep-sided valley formed 

when faulting caused a block-shaped area to drop 

relative to the surrounding terrain. 

Lake level has fallen below the natural sill 

11 times during the present century (Lindstrom, 1990). 

It is currently ( 1993) below the natural sill for the 

fourth consecutive year. During the drought of the late 

1920's and early 1930's, the lake dropped below the 

natural sill for 6 straight years, reaching a recorded low 

of 1,896.4 m in December 1934 (Tahoe World, Incline 

Village, Nev., April21, 1988). 

When Lake Tahoe was at its lowest elevation in 

1934, Harding ( 1965) observed 11 stumps near Tallac. 

Three samples from two stumps were radiocarbon 

dated. One stump, at an elevation of 1 ,896. 7 m dated 

4,250 ± 200 and 4, 790 ± 200 yr B.P. The 

second stump, at an elevation of 1,896.7 m, dated 

4,460 ± 200 yr B.P. These dates are about 700 yr less 

than the calendar age of the stumps because they have 

not been calibrated against the exactly dated 

bristlecone pine record. Six of the 11 stumps located 

by Harding ( 1965) were relocated by Lindstrom in 

1985 (Lindstrom, 1990). Elevations for the six stumps 

ranged from 1,896.1 to 1,896.9 m. Lindstrom (1990) 

reported that two radiocarbon satnples obtained from 

Harding's lowest reported stump dated 4,870 ± 60 and 

4,520 ± 60 yr B.P. (uncalibrated dates) or 5,640 and 

5,197 cal yr B.P. (calibrated). These dates indicated 

that the tree was at least 350 yr old. In 1990, some of 

these stumps were relocated, and several increment 

cores were obtained that showed the radial growth 

pattern. If the lake-level fluctuations were climatic in 

origin, the age of the tree indicated the lake dropped 

below 1,896.9 m for at least 350 yr. 

Between 1989 and August 1992, 20 additional 

stumps were located at South Lake Tahoe between 

Stateline and Emerald Bay. All of these stumps are at 

or below the natural sill level. Twelve stumps are at 

Baldwin Beach, one is at the mouth of Emerald Bay, 

four are at AI Tahoe, and one is at El Dorado Beach in 

Stateline. Two stumps were recently found near the 

University ofNevada Extension facility and 4-H camp 

in Stateline. 

The largest stump found to date ( 1993) is more 

than 2.5 m tall and about 1.07 min diatneter. In 

general, the deepest stumps are the tallest, and the 

shallowest stumps are the shortest. The shallow 

stumps have been repeatedly exposed during the past 

5,000 to 6,000 yr and have been subjected to decay and 

abrasive wave action. Fourteen stumps have 

been radiocarbon dated; the ages were between 6,304 

and 4,846 cal yr B.P. The oldest stumps are generally 

the deepest. They document a period about 1,300 yr 

long when the trees were exposed, but whether the land 

on which the trees are located was continuously 

exposed for the entire period cannot be answered with 

ABSTRACTS OF PRESENTATION n 
the limited data available. Higher frequency 

fluctuations in lake level may have occurred, but such 

fluctuations cannot be identified using the stnall sample 

of radiocarbon dates. 

Untill993, no stumps from Lake Tahoe were 

found outside the south-shore region. Because of the 

immense publicity the trees have received in 

newspaper articles and on television, additional stumps 

have been reported and verified elsewhere in Lake 

Tahoe. A large submerged tree in about 10m ofwater 

ha~ been independently reported by two divers several 

hundred meters off the pier at Tahoe Vista. A single 

tree has been reported off Dollar Point~ and numerous 

additional stumps have been independently reported by 

several individuals from Emerald Bay. 

The unique and potentially scientifically 

valuable reports are of submerged trees at depths of 

21 to 23 m in Sand Harbor. One of the trees was 

recently located using a rcn1otely operated 

submersible. The tree is about I 0 m long and larger 

than 1.3 m in diameter. It is lying horizontal, located 

along a dropoff to deeper water; the trunk faces the 

lake, and the top points toward shore. Currently, trees 

that are rooted upright are being sought, a difficult and 

time-consuming task, at depths of 23 m. The Sand 

Harbor trees are definitely not sinkers or remnants of 

logging activity during the last century because they 

have not been cut. 

Submerged tree stutnps have been observed in 

other high-altitude Sierran lakes. Ten stumps were 

observed in Independence Lake, California, several 

years ago. Three samples from below the pre-dam 

level were radiocarbon dated from between 700 cal yr 

B.P. to within the past 150 yr. Samples for radiocarbon 

dating also have been obtained from several submerged 

tree stumps at pre-dam levels in Donner Lake, 

California (Lindstrom, 1990). Additional stumps at 

depths of about 21 to 24 m have been reported from 

Fallen Leaf Lake, California (John Kleppe, University 

ofNevada, oral commun., 1990). One of the deep 

stumps was verified by a diver in 1990. Finally, 

Lindstrom ( 1990) reported stumps 3 to 6 m below the 

surface of a lake west of Downieville, California. The 

widespread presence of submerged stumps of 

approximately similar ages would strongly indicate 

that a large-scale climate change caused simultaneous 

drops in the surfaces of several lakes. 

Several hypotheses can be offered to account for 

the presence of the submerged trees below the natural 

sill of Lake Tahoe. A climatic argument can be 

proposed that postulates more arid conditions than in 

the present century. According to this hypothesis, a 

middle Holocene decline in lake level resulted from a 

drying trend in the Western United States. Such a trend 

is supported by geomorphological and palynological 

.data. This evidence includes 5- to 6-m-high beach 

ridges at Kings Beach, drowned shorelines and sandspit-dammed marshes along the south shore, submarine 

canyons on the east and west sides of the lake, buried 

lakeshore deposits on the south shore, pollen cores 

from within the Tahoe Basin, and sediment cores from 

the lake bottom. A modification of the hotter and drier 

hypothesis suggested by Davis and Elston ( 1972), was 

that the middle Holocene may have been more variable 

and not necessarily hotter and drier. A combination of 

the two hypotheses also is possible. 

A subsidiary to the climatic hypothesis proposes 

that a rise in the level of Lake Tahoe could have 

resulted from sediment accumulation over the natural 

sill. Cores obtained from inside the outflow channel 

by the U.S. Department of Agricultural Forest Service 

(Hug, 1989) and the Bureau of Reclamation (Hawkins 

and others, 1986) revealed 4-m-thick sediments. 

Radiocarbon samples need to be obtained to date the 

sediments and provide a test for this subsidiary. 

Another hypothesis that could account for the 

presence of the submerged stumps in Lake Tahoe is 

tectonic in origin (Harding, 1965). This hypothesis is 

that there was a structural rise in the elevation of the 

natural sill near Tahoe City or subsidence at the south 

end of the basin, or both. Although there has been 

considerable tectonic activity in the Tahoe Basin, it ha~ 

not been demonstrated to be of Holocene age. Tectonic 

activity within the Tahoe Basin, and in the lake in 

particular, during the Holocene needs to be 

investigated. 

78 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
REFERENCES 

Davis, J.O., and Elston, R.O., 1972, New stratagraphic evidence of late Quaternary climatic change in northwestern 

Nevada, in Fowler, D.D., ed., Great Basin cultural ecology-A symposium: Desert Research Institute Pubs in the 

Social Sciences 8, p. 43-55. 

Harding, S.T., 1965, Recent variations in the water supply of the western Great Basin: Berkeley, University of California 

Water Resources Center, Archives Series Report 16, 226 p. 

Hawkins, F.F., LaForge, Roland, and Hansen, R.A., 1986, Seismotectonic study of the Truckee/Lake Tahoe area, northeastern 

Sierra Nevada, California, for Stampede, Prosser Creek, Boca, and Lake Tahoe Dams: Bureau of Reclamation 

Seismotectonic Report 85-4, 210 p. 

Hug, W.L., 1989, Tahoe City Visitors Center foundation investigation, Lake Tahoe Basin Management Unit: South Lake 

Tahoe, Calif., U.S. Department of Agriculture Forest Service, Lake Tahoe Basin Management Unit, unpublished 

manuscript, 10 p. 

Lindstrom, S.G., 1990, Submerged tree stumps in the Lake Tahoe Basin: Journal of California and Great Basin Anthropology, 

v. 12, p. 146--157. 

ABSTRACTS OF PRESENTATIONS 79 

Sediment-Magnetic and Paleomagnetic Records of 

Middle Pleistocene Sediment from Buck Lake, Southern Oregon 

Joseph G. Rosenbaum, Richard L. Reynolds, Priscilla Fitzmaurice, David P. Adam, and 

Andrei M Sarna- Wl?jcicki, U.S. Geological Survey 

Sediment-magnetic and paleomagnetic studies 

of lacustrine sediment from Buck Lake in southern 

Oregon are designed to contribute to understanding 

regional paleoclimatic change during the Pleistocene. 

The results could be used to determine intrabasin and 

interbasin correlations and sedimentation rates. These 

studies also may reveal variations in the concentration 

and character of detritaltnagnetic particles that record 

changes in environmental conditions in the source 

are~ in depositional environments, or in alteration 

of the sediment. Magnetic-susceptibility (MS) 

mealiiurement'i, using a whole-core, pass-through 

instrument, have been made for the greater than 41-m 

length of the core. Sediment-magnetic and 

paleomagnetic analyses also have been completed for 

more than 300 azimuthally unoriented specimens from 

depths of 5.2 to 24.1 m in a rotary-drill core. 

The age of the sediment is controlled by several 

tephra layers correlative with the Loleta ash bed/Bend 

pumice (greater than 400,000 to 300,000 yr B.P., depth 

9.5 to 9.6 m), the Rockland ash bed (less than 470,000 

to 400,000 yr B.P., depth 19.9 m), the Dibekulewe ash 

bed [between 600,000 and 500,000 yr B.P. ('?), 

depth 20.8 m], the Lava Creek Bash bed (greater than 

665,000 yr B.P., depth 22.3 m), and the Rye Patch 

Dam ash bed [670,000 yr B.P. (?),depth 22.6 m]. 

Normal polarity inclinations were measured to 24.1 m, 

indicating deposition of the sediment during the 

Brunhes chron (less than 780,000 yr B.P. ). 

Comparisons of magnetic properties that reflect 

the abundance, mineral type, and grain size of 

magnetic minerals (fig. 1) strongly imply that the 

magnetization of the sediment is dominated by detrital 

magnetite. The magnetic properties indicate no 

obvious post-depositional alteration, such as the 

conversion of magnetite to ferric oxide or to 

nonmagnetic iron sulfide minerals, and the properties 

lack evidence for authigenesis of magnetic iron sulfide, 

such alii greigite. Nevertheless, the requisite petrologic 

study to confirm or deny a detrital origin of magnetic 

grains needs to be undertaken. 

The MS (primarily magnetite content, fig. 1) of 

fine-grained lacustrine sediment, the predominant 

lithology to 24 m in depth, ranges over about 2 orders 

of magnitude. Between 5- and 24-m depths, two zones, 

each 3 to 4 m thick, of relatively high MS are bounded 

by intervals oflower MS. Except for the Rockland ash 

bed, a 50-cm thick interval of basaltic cinders above 

the Rockland ash (greater than 19.4 to 19.7 m), and two 

thin tephra layers (12.23 and 14.92 m), each ofwhich 

contains material having high MS, the variations in MS 

have no obvious correspondence to lithology. 

The content of ferric oxide mineral, such as 

hematite [the hard isothermal remanent magnetization 

(HIRM) shown in fig. 1], correlates so closely with the 

content of magnetite that both mineral types must be 

part of a detrital heavy-mineral suite and are not related 

by in-situ alteration. The ratio of magnetite to ferric 

oxide mineral (indicated by the S parameter in fig. 1 ), 

however, does not remain constant. The greater the 

absolute amount of magnetite (high MS), the greater 

the relative amount of magnetite (highS values). This 

relation indicates that high magnetite content is 

associated with source rocks that have undergone little 

chemical weathering involving alteration of magnetite 

to ferric oxide. Conversely, low magnetite content may 

be associated with relatively more chemical 

weathering (lowS values), possibly during soil 

formation, in the catchment. On a broad scale, large 

magnetic grain size (lower ratios of IRM/MS and 

ARM/MS indicate larger size, fig. 1) corresponds to 

high magnetite content (high MS), and small magnetic 

grain size (high-ratio values) corresponds generally to 

low magnetite content. Paradoxically, the magnetite 

grain size generally decreases (higher ARM/MS) as 

tnagnetite content increases (higher MS) for the 

MS spikes within both high MS zones,. Whatever 

erosional or depositional processes increased the 

magnetite content, causing the high MS spikes within 

the broad high MS zones, they also decreased the grain 

size of the magnetite. The possibility of mechanical 

weathering needs to be tested using detailed grain-size 

ABSTRACTS OF PRESENTATION 81 
~-~-

=:~.,=~=== 

·.~· 

·-=:~J:. -~·.-... 

10 100 2 10 100 

S HIRM X 10·4 MS X 10·6 

parameter (emu/em 3) 

0 

t 

==r-'========== e.;. 

~~~~~~~~~~~ .,,. 

.., 

·?.· ,;I 

_] 

~ .. ,..... 

j 

f~ '=-= L. 

===-L::;o========= Loleta ash bed ·~· .. c. 

-~ ,,.-r 

'!l;. 

==f.======== ==unnamed ash bed 

:c::: 

.')· 

-~· .-~-

=~. == "~~====unnamed ash bed 

.~· 

.:= 

,~. 

·~':-;:==--· 

- ~;i~·~=~~~==-~~=c~n~c~:nd ash bed 

~· ='""'r~=========== Dibekulewe ash bed 

-1' •-=!.!,. .-• 

=~)·============Lava Creek Bash bed 'I 

~ 

·~· 

500 

IRM I MS 

1,000 0 10 

ARM/MS 

20 

Figure 1. Plots of magnetic properties with depth, Buck Lake (southern Oregon) core 1. The S parameter shows relative amounts of magnetite and high-coercivity magnetic minerals (for example, ferric oxide minerals, such as hematite and goethite). Higher values indicate more magnetite. The S parameter is the ratio of the isothermal remanent 

magnetization (lAM) acquired in a backfield of 0.3 Tesla (T) to forward IRM acquired at 1.2 T: -IRM.o.ar11RM1.

2r. HIRM 

(hard IRM; [IRM.o.ar + IRM1.2r]/2) is a measure of the concentration of high coercivity magnetic minerals. Magnetic 

susceptibility (MS), in cgs-volume units, is primarily a measure of magnetite content. IRM/MS and ARM/MS 

(ARM=anhysteretic remanent magnetization) are measures of magnetic grain size. Lower values of these ratios indicate larger effective magnetic grain size. 

analyses of bulk sediment across a number of the 

magnetic features. 

Pollen and MS zonations correspond closely. 

Warm climates are indicated for the intervals 5.3 to 

9.8 m and 14.5 to 16.5 m, which are both zones of 

mostly low MS. In contrast, cold and open 

environments of sagebrush steppe are characteristic of 

the intervals 9.8 to 14.5 m and 16.5 to about 20m, 

which are both zones of predominantly high MS. The 

magnetic mineralogy thus seems to indicate changes in 

climate, at least for broad intervals of time. The shorter 

wavelength magnetic features also may record climate 

change-a possibility that could be tested by detailed 

palynologic and sedimentologic analyses of a few such 

features. 

82 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Tephrochronology in Studies of Middle to Late Quaternary 

Climate Change, Northern Great Basin 

Andrei M. Sarna- Wqjcicki, Charles E. Meyer, and Elmira Wan 

U.S. Geological Survey 

Tephrochronology, the study of the age and 

correlation of volcanic ash layers, is useful in studies of 

Quaternary climate change in the northern Great Basin 

because it makes it possible to identify spatial and 

temporal reference datum planes (Sarna-Wojcicki and 

Davis, 1991; Sarna-Wojcicki and others, 1991}. Much 

of this region is downwind from two n1ajor volcanic 

area~ that have been the sources of sporadic, but 

prolific, explosive volcanic activity throughout the 

middle and late Quaternary. These sources are the 

Ca~cade Range of Wa~hington, Oregon, and northern 

California, and the Long Valley-Mono Craters area of 

east-central California (fig. I). Isotopic and other 

numerical ages determined from widespread ash 

layers from these sources provide local and regional 

age control, whereas chemical and petrographic 

characterization of the layers allows unambiguous 

temporal correlation of a~sociated sediment~. 

Correlations of ash layers also provide a means of 

evaluating the accuracy of numerical ages obtained 

from the same layers. Tephrochronology has been 

particularly useful when applied to upper Quaternary 

sediments because the geologically young tephra is 

usually unaltered and because the method 

complements magnetostratigraphy, which may not be 

as effective within the Brunhes Normal Chron (the last 

approximately 77 5,000 yr). 

Tephra layers that originated from the Cascade 

Range generally provide the largest number of 

unatnbiguously identifiable a~h layers in the northern 

Great Basin. This is because the volcanic field is large 

and has several active sources of explosive activity 

(fig. 1) and also because the tephra is derived from 

small magma bodies that formed frequently throughout 

Quaternary time (table 1 ), providing compositional 

contrasts that can be readily determined with the 

electron microprobe. 

Tephra layers that originated from the Long 

Valley and Mono Craters in ea~t-central California are 

generally less distinctive and, consequently, more 

difficult to identify than tephra layers from the Cascade 

Range, probably because the former tephra layers were 

derived from mostly larger, longer-lived magma 

bodies. Nevertheless, sets of these layers can be 

separated on the basis of chemical characteristics and 

chronostratigraphic data into temporal sequences 

representing several past eruptive episodes. 

Furthe.rmore, certain individual layers of the Long 

Valley and Mono Craters suite can be readily identified. 

Tephra layers that originated from the volumetrically 

smaller Inyo Craters and from Mammoth Mountain in 

Long Valley are generally distinctive. 

All tephra layers become thinner, finer, and 

scarcer with distance from the two main source areas. 

Dispersal from the sources was multidirectional. Some 

tephra clouds, such as the Loleta ash, were carried to 

the west, and their layers are present in marine 

sediments of coastal northern California and in deepsea cores of the Pacific. Layers from these eruptions 

provide vital chronostratigraphic units that allow 

correlation between land basins and the deep-ocean 

paleoclimatic record. Predominant direction of tephra 

transport, however, was toward the east. The Lahontan 

Basin of northwestern Nevada (including Pyramid 

Lake, the Humboldt River Basin, and the Carson Sink) 

is the area where tephra layers from the two volcanic 

sources overlap most frequently. Widespread tephra 

layers derived from the Yellowstone volcanic source in 

northwestern Wyoming and in eastern Idaho also are 

present within the northern Great Basin. 

Generally, good numerical age control to about 

35,000 yr B.P. from radiocarbon dating is obtained 

from Holocene and late Pleistocene tephra layers, 

although finite ages within the older end of this range 

may be suspect. Tephra layers in the age range of about 

300,000 to 35,000 yr B.P. have been poorly dated until 

recently. New work using the 40ArP9 Ar method, 

combined with thermoluminescence and uraniumseries methods, has begun to provide geologically 

realistic and stratigraphically consistent numerical 

ages within this range. Laser-fusion 40 ArP9 Ar analysis 

of single crystals is providing some reliable new age 

data on both proximal and distal tephra layers older 

ABSTRACTS OF PRESENTATION 83 
45° 

T A H 

35° 

0 50 100 150 200 KILOMETERS EXPLANATION 

1-l -.L..' --.-, -L'--''-r•-.1' 0 50 100 MILES * CASCADIAN VOLCANIC SOURCE 

0 MONO CRATERS-INYO CRATERS-LONG VALLEY VOLCANIC SOURCE 

@ YELLOWSTONE NATIONAL PARK VOLCANIC SOURCE 

• PALEOCUMATE STUDY SITE 

Figure 1. Location of middle to late Quaternary volcanic sources and sites where studies of Quaternary climate change 

are being conducted or have been recently completed. 

84 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Table 1. Tephra layers useful in correlation of upper Quaternary sediments, northern Great Basin 

Age, (1o2 yr B.P.) Name of layer Layer, also known as 

0- (number of layers in 

stage1 (age range) (or tephra sequence) sequence) Source of tephra 

[age event] [name of magnetic event] [name of magnetic event] 

(-0.7-11) (Mono-Inyo Craters) (20 layers, minimum) Mono, Inyo Craters 

6.85 ± 0.15 Mazama2 Climatic airfall pumice Crater Lake 

7.02 ± 0.05 Tsoyowata Llao Rock airfall pumice Crater Lake 

2 (-13-36) (Wilson Creek ash beds) ( 19 layers, minimum) Mono Craters 

2 20.5-23.4 Trego Hot Springs Redcloud pumice Crater Lake 

2 -25 Wono Crater Lake 

2 -27 Tule Lake T24 3 8 Summer Lake E1 unknown 

2 -27 Wilson Creek ash 15 Mono Craters 

2 [-27] [Mono Lake Event] 

2-3 (33-36?) (Marble Bluff) (Mount St. Helens set C) Mt. St. Helens 

( 5 layers, minimum) 

4? 55-75 Olema Clear Lake Ash 4 Newberry (?) 

3-5? 

(50-100) (Proto-Mono Craters and Mono Craters and MamMammoth Mountain) moth Mountain 

5 [112-114?] [Blake Event] 

5 -120-130 TuleLake T642 DSDP 173-1-3, 4 Crater Lake (?) 

6? -140 Tule Lake T1193 Summer Lake V Newberry (?) 

6 -150 Summer Lake FF Bend-Three Sisters (?) 

6 -150 Summer Lake GG Paoha Island 4 Bend-Three Sisters (?) 

6 -155-160 Tule Lake T2080L Wadsworth Bed (?) Medicine Lake(?) 

6 -160 Summer Lake JJ Paoha Island 3 Bend-Three Sisters (?) 

6 -160±25 Tule Lake T2023 Sunm1er Lake KK Medicine Lake 

6? [-160-180] {Jamaica?] [Biwa I Event?] 

6? -180 Summer Lake NN Paoha Island 2 Bend-Three Sisters (?) 

10? 300-400 Loleta2 Bend pumice Bend-Three Sisters (?) 

11? 

400-470 Rockland2 Rockland pumice tuff Lassen Peak area breccia; Maidu 

16? -500-600? Dibekulewe unknown 

16 665 ± 5 Lava Creek B2 Pearlette 0 Yellowstone 

16 670? Rye Patch Dam Desert Springs Bend-Three Sisters 

19 758±2 Bishop B2 Ash of the Bishop Tuff Long Valley Caldera 

[19] [-775] [Brunhes/Matuyama 

Chron boundary] 

Imbrie and others ( 1984 ). 

2

Tephra layers present, or magnetic events detected, in both marine and nonmarine sediments. 

ABSTRACTS OF PRESENTATIONS 85 
than about 100,000 yr when potassium-rich minerals, 

such as sanidine. are present. This mineral is present 

in tephra layers from the Long Valley-Mono Craters 

and Yellowstone sources, but is not present in tephra 

layers from the Ca'icade Range. For tephra layers 

from the latter sources, plagioclase concentrates of 

about 100 mg or more that are obtained from proximal 

exposures can be analyzed by the step-heating 

40 ArP9 Ar method. These methods minimize the 

problem of detrital or accidental contamination in the 

mineral concentrates and permit evaluation of results 

caused by alteration or other perturbations of the argon 

isotopic ratios that could result in spurious ages. 

REFERENCES 

Recently completed or ongoing studies using 

tephrochronology, which are relevant to paleoclimatic 

studies of upper Quaternary sediments within the 

western Great Basin and closely adjoining regions, 

are within the Pringle Falls and Summer Lake area 

of central Oregon; the Tule Lake-Klamath area of 

south-central Oregon and northern California; the 

Mohawk Valley of northeastern California; Pyramid 

Lake, Humboldt River, Carson Sink, Walker Lake, and 

Fish Lake in western Nevada; and the Mono Basin 

(which contains the Mono Craters), Long Valley, 

Owens Valley, and Lake Tecopah in east-central 

and southern California (fig. 1). 

Imbrie, J., and others, 1984, The orbital theory of Pleistocene climate; support from a revised chronology ofthe marine 

180 record, in Rerger, A.L., and others, eds., Milankovich and climate, part 1: Dordrecht, The Netherlands, D. Reidel 

Publishing, p. 169-305. 

Sarna-Wojcicki, A.M., and Davis, J.O., 1991, Quaternary tephrochronology, in Morrison, RB., ed .• Quaternary nonglacial 

geology---Conterminous United States: Geological Society of America, DNAG Series, v. K-2, p. 93-116. 

Sarna-Wojcicki, A.M., Lajoie, K.R., Meyer, C.E., Adam, D.P., and Rieck, H.J ., 1991, Tephrochronologic correlation of upper 

Neogene sediments along the Pacific margin, conterminous United States, in Morrison, R.B., ed., Quaternary nonglacial 

geology---Conterminous United States: Geological Society of America, DNAG Series, v. K-2, p. 117-140. 

86 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Effect of Holocene Climatic Fluctuations on Alluvial-Fan 

Deposition, Fish Lake Valley, Nevada-California 

Janet L. Slate, Associated Western Universities-Northwest Division, 

Washington State University, Tri-Cities Campus 

Many authors recognize similarity in deposits, 

morphology, and inferred processes in alluvial fans of 

the arid and semiarid Southwest United States (for 

example, in Nilsen, 1985), but interpretations of the 

origins and timing of deposition and entrenchment of 

modem fans are diverse. A combination of several 

factors may control fan formation and development; 

these factors include source-basin lithology, tectonics, 

and climatic change. Whether fan aggradation occurs 

during relatively humid climatic intervals (Lustig, 

1965; Dom and others, 1987) or during transitional 

intervals from relatively humid to arid periods (Bull 

and Schick, 1979; Wells and others, 1987) is 

controversial. Relating fan deposition to climatic 

change requires independent age control that is 

generally difficult to establish in desert basins because 

of the paucity of datable materials in such deposits 

(Wells and others, 1987). 

Fish Lake Valley (FLY) in Nevada and 

California (fig. 1) is an ideal place to study the timing 

of alluvial-fan development. The Quaternary deposits 

contain abundant datable materials such as charcoal 

and wood fragn1ents, tephra, and buried soil A (Ab) 

horizons (table 1 ). These materials help to constrain 

the ages of fan formation and can help to resolve the 

controversy of climatic controls on fan aggradation and 

entrenchment. 

The fan deposits were dated wherever suitable 

materials were available to help detennine whether 

deposit~ mapped in four different drainage settings are 

approximately coeval. Coeval deposits among the 

diverse drainage settings would indicate that a broad 

controlling factor, such as climatic change, affected 

alluvial-fan aggradation. If deposits are not coeval, 

however, other more local factors, such as faulting or 

factors related to the source-area setting or geomorphic 

history, could have been responsible for alluvial-fan 

aggradation. 

Thirty-two satnples consisting of charcoal and 

wood fragments, tephra, and buried soil A horizons 

from FLY fan deposits define eight depositional pulses 

within four Holocene surficial units (Q7, Q6, Q5, Q4) 

(table 1). Most of the dates of the depositional pulses 

represent the average of two or more 14C dates and 

estimated tephra ages that overlap at one standard 

deviation. These subunits were interpreted as discrete, 

basinwide depositional pulses. Because the four areas 

studied have similar geomorphic and soil sequences 

(Slate, 1992) and the dates among the units from 

different drainages agree, deposition of the FLY 

alluvial fans may be controlled mostly by climate. 

A comparison of depositional pulses recorded 

by dated Holocene alluvial-fan deposits in FLY to 

proxy paleoclimatic records from nearby areas (fig. 2) 

indicated an influence of Holocene climatic 

fluctuations on alluvial-fan deposition. The records 

of areas in the adjacent White Mountains (LaMarche, 

1973), northern Eureka Valley just south ofFLV 

(Spaulding, 1985), and two sites in the Sierra 

Nevada--100 km to the west (Curry, 1969, 1971; 

Burke and Birkeland, 1983) and 150 km to the 

southwest (Scuderi, 1987}--were used for this 

comparison. These data indicate that three pulses 

occurred during times of relative warmth, two pulses 

occurred during climatic transitions from cold to warm, 

two pulses occurred during cold or cooler climates, and 

one pulse had an uncertain correlation (table 2). Thus, 

Holocene fan deposition in FLY was associated with 

warm periods or transitions from cold to warm periods 

in 63 percent of the cases. 

ABSTRACTS OF PRESENTATION 87 
37°45' 

Study 

site 

···. 

... 

SILVER 

RANGE 

... · ... 37"30' ...... 

·. 

10 15 20 KILOMETERS 

0 5 10 MILES 

Figure 1. Location map of Fish Lake Valley (FLV) in Nevada and California. The named drainages include those from 

which dates were obtained. 

88 Proceedings of the Workshop "Ongoing Paleoclimatic Studies In the Northern Great Basin," Reno, Nevada, May 1993 
HOLOCENE 

SURFICIAL 

SOIL UNITS 

FISH LAKE 

VALLEY 

(this study) 

VEGETATION 

WHITE EUREKA GLACIAL ADVANCES SIERRA NEVADA 

MTS VALLEY Scuderi Curry Burke and 

LaMarche Spaulding (1987) (1969, 1971) Birkeland 

(1973) (1985) (1983) Or---- -----------------------w-a_r_m------~r-------w--ar-m------------~~~~M~at~th~e-s--_-?--------~ 

warm=== cold --Matthes I T ===cold 

1--

z 

w 

(/) 

w 

c:: 

a.. 

1,000 r2,000-

~ 3,000-

0 

LL 

w 

aJ 

(/) 

c:: 

<( 

w 4,000r-

>-

z 

u.i 

(.9 

<( 

5,000-

6,000-

07 

06 

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05 

05 

05 

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04 

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I 

I 

I 

I 

I 

I 

I 

I 

cold 

and 

dry 

T 

cool 

but 

drier 

--

cooler 

and 

wetter 

1 

I 

I 

I 

I 

I 

1 

warm 

vegetation 

analogous 

to 

today 

1 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

increased 

effective 

moisture 

and 

higher 

temperature 

warm== cold --Matthes 

warm -?-

cooler with 

cold pulses 

warm 

--Matthes 

--Unnamed - --Unnamed-- Unnamed 

I Recess 

Peak 

---r- Recess _J__ Peak 

-

Recess -- Peak -

-

-

-

7,000~----------------------------L-------~L-----------------------------------------~ 

Figure 2. Chronology of Fish Lake Valley depositional pulses compared to proxy paleoclimatic records of the White 

Mountains, Eureka Valley, and Sierra Nevada during the last 7,000 yr B.P. Horizontal lines that terminate vertical lines in 

this figure indicate the time period over which a soil-forming, climate, vegetation, or glacial event occurred. 

ABSTRACTS OF PRESENTATIONS 89 
CD 

0 

"'tt 

a Table 1. Geochronologic controls on alluvial-fan-deposit ages n 

CD 

& 

3' Depth below Surficial unit Technique Laboratory cc Date1 surface Area Field number Comments "' (age) (material) number2 0 (em) 

--:::r 

CD 

~ Q7 11 0±60 yr B.P. 14C (charcoal) 80 Trail Cyn FLV-C-11 QL-4370 3.1 km upstream from soil24-TC at 1,805 m3 

i (Late Holocene) 120±45 yr B.P. 14C (wood) 5-26 Marble Cr 5-TS-1-51MC-I Beta-26169 Site RC-1 (Sawyer, 1990) 0 <150 yr B.P. AMS-14C (charcoal) 65 Trail Cyn FLV-C-25 LL-858 Soil profile JH-6.5A , 4 

c:S 520±50 yr B.P. AMS 14C (charcoal) 65 Trail Cyn FLV-C-15 T0-1667 Soil profile JH -6.5A ::s 

cc 640±40 yr B.P. EMA (tephra)5 0 200 Marble Cr 5-TS-1-7MC-C T145-1 Site RC-1 (Sawyer, 1990) 3' 

cc 660±50 yr B.P. 14C (wood) 80 Marble Cr 5-TS-1-7MC A-4765 Site RC-1 (Sawyer, 1990) "'tt 

I» 680±65 yr B.P. 14C (wood) 200 Marble Cr 5-TS-1-49-B A-5068 Site RC-1 (Sawyer, 1990) f 

Sl 1 ,090±50 yr B.P. AMS 14C (charcoal) -200 Trail Cyn FLV-C-16 T0-1668 Composite of soil sites 24-TC, JH -7 3' 

I» 

~ Q6 1 ,065±55 yr B.P. 14C (wood) 40-50 Marble Cr 5-TS-1-52 Beta-26170 Site RC-4 (Sawyer, 1990) 

~ (Late ~olocene) 1,150±1.15 yr B.P. EMA (tephra) 70 Trail Cyn FLV-70-TC T195-4 Surface disturbed; not true depth CD 1,150±1.15 yr B.P. EMA (tephra) 80 Toler Cr FLV-67-MA T195-1 Distal fan "' 3' 

:;. 100 Cave Spg CD 1,150±1.15 yr B.P. EMA (tephra) FLV-64-CS T170-7 NE side ofFLV; Rhyolite Ridge Quad Wash z 

0 1,150±1.15 yr B.P. EMA (tephra) -200 Iron Cr FLV-68-IC T195-2 Proximal fan i 

se 1,000-2500 yr B.P. EMA (tephra) 90 Furnace Cr FLV-131-FC T203-4 1.0 km downstream ofsoil18-FC at 1,575 m ::s 

C) 1,410±200 yr B.P. 14C (charcoal) 100 Indian Cr FLV-C-6 W-6181 1-cm-thick reworked lens l 1,420±210 yr B.P. 14C (charcoal) N/A Indian Cr FLV-C-3 W-6168 Base of colluv. wedge overlying deposit IIJ 14C (wood) I» 1 ,555±45 yr B.P. 50 Marble Cr 5-TS-1-28FC A-4768 Site RC-3 (Sawyer, 1990) !!!. 

~ : 6,845±50 yr B.P. EMA (tephra) 490 Furnace Cr FLV-71-FC T-195-5 Southernmost Mt. Mazama ash locality 

::rJ 

CD 

::s 

9 Q5 1,93 8±50 yr B.P. AMS 14C (charcoal) -100 Indian Cr FLV-C-5 AA-4886 In -situ burn buried by debris flow z 

~ (Middle 2,155±50 yr B.P. 14C (wood) 220 Marble Cr 5-TS-1-22A A-4767 Site RC-2 (Sawyer, 1990) I» 

, Holocene) 2,340±55 yr B.P. 14C (wood) -500 Marble Cr 5-TS-1-10MC A-4766 Site RC-2 (Sawyer, 1990) 

5: 2,400±500 yr B.P. 14C (charcoal) -200 Indian Cr FLV-C-4 W-6179 In-situ burn, 1 m below FLV-C-5 ~ .... 3,600±3.6 yr B.P. EMA (tephra) 87-89 Trail Cyn FLV-135-TC T203-5 Soil JH-6A; 2.4 km dn fan of 141-TC I 

w 3,600±3.6 yr B.P. EMA (tephra) -630 Trail Cyn FLV-141-TC T-203-7 Surface disturbed; depth uncertain 

3,600±3.6 yr B.P. EMA (tephra) -500 Trail Cyn FLV-142-TC T203-8 0.9 km down fan of 141-TC 

3,860±100 yr B.P. AMS 14C (charcoal) -510 Trail Cyn FLV-C-24 LL-859 10 em below FLV-142-TC 
):lo 

m 

en 

~ 

:a 

l:; 

u1 

, 

0 

., 

:a 

m 

en 

m 

z 

~ 0 

z 

en 

!l 

Table 1. Geochronologic controls on alluvial-fan-deposit ages-Continued 

Surficial unit Technique Depth below Laboratory 

(age) Date1 

(material) surface Area Field number number-2 Comments 

(em) 

4,213±157 yr B.P. AMS 14C (charcoal) 50 Indian Cr FLV-C-7 AA-4907 In-situ burn buried by debris flow 

5,680±250 yr B.P. 14C (charcoal) 220 Indian Cr FLV-C-2 W-6166 1. 7 m below FLV-C-7 

Q4 6,260±100 yr B.P. 14C (charcoal) 95 Trail Cyn FLV-C-14 QL-4369 Soil profile JH-5C 

(Pleistocene/ 6,550±100 yr B.P. 14C (charcoal) 330 Indian Cr FLV-C-13 QL-4371 3-cm-thick reworked lens 

Holocene (?) or 7,500±100 yr B.P. TL (Ab horizon)6 133-140 Trail Cyn FLV-L-6-TC ITL-270 Buried by Q4 alluv; soil JH-5B 

Early 11,000±2,000 yr TL (Ab horizon) 133-137 Trail Cyn FLV-L-9-TC ITL-282 Buried by Q4 alluv; soil JH-5B Holocene(?)) B.P. 

1

Carbon-14 and TL error ranges reported at 1cr level. 14C dates provided by M.C. Reheis, USGS-Denver, Colorado: J.W. Harden, USGS--Menlo Park, California; and T.L. Sawyer, University of NevadaReno. 

Dates ofSawyer(1990) are calibrated according to schemes ofStuiver and Pearson (1986). 

2Key to numbers for 14C Dates: 

A-# = University of Arizona, Tucson 

AA-# = Accelerator mass spectrometry (AMS) date, University of Arizona, Tucson. 

Beta-#= Beta Analytic, Inc., Coral Gables, Florida. 

LL-# = Lawrence Livermore Laboratory, Livermore, California 

QL-# = University ofWashington, Seattle 

TO-# = University ofToronto, Ontario, Canada. 

W-# = U.S. Geological Survey, Reston, Virginia 

3Soil profiles with suffixes keyed to localities (FC=Furnace Creek, TC=Trail Canyon) were described by J.L. Slate. 

4Soil profiles with JH prefix are at Trail Canyon, and were described by J.W. Harden or J.L. Slate, or both. 

5

Electron microprobe analyses (EMA) of volcanic glass done by C.E. Meyer, USGS-Menlo Park, California. 

6Thermoluminescence (TL) analyses done by J.L. Slate at INST AAR facility, University of Colorado-Boulder. 
Table 2. Average age ranges of depositional pulses within Holocene surficial units (07, 06, 05, 04) in 

Fish Lake Valley, number of carbon-14 and tephra samples providing age control, and inferred paleoclimate for 

those times based on records in the nearby White Mountains, Eureka Valley, and Sierra Nevada 

[--,no samples provide age control for that depositional pulse.] 

Age in years 

Number of samples providing 

age control Inferred paleoclimate before present 14c Tephra 

Unit 

Q7 110 ±55 3 Transitional 

600 ±50 3 Cooler or cold 

Q6 1,100 ±55 2 5 Transitional 

1,450 ± 205 3 Uncertain 

Q5 2,200 ± 500 4 Cool 

3,900 ± 300 2 3 Warm 

5,700 ± 250 1 Warm 

Q4 6,550 ± 200 2 Warm 

REFERENCES 

Bull, W.B., and Schick, A.P., 1979, Impact of climatic change on an arid watershed-Nahal Yael, southern Israel: Quaternary 

Research, v. 11, no. 2, p. 153-171. 

Burke, R.M., and Birkeland, P.W., 1983, Holocene glaciation in the mountain ranges of the Western United States, 

in Wright, H. E., Jr., ed., Late-Quaternary environments of the United States, v. 2, The Holocene: Minneapolis, 

University of Minnesota Press, p. 3-11. 

Curry, R.R., 1969, Holocene climatic and glacial history of the central Sierra Nevada, California: Geological Society of 

America Special Paper 123, p. 1-47. 

__ 1971, Glacial and Pleistocene history ofthe Mammoth Lakes Sierra, a geologic guidebook: Missoula, University of 

Montana Department of Geology Publication 11, 49 p. 

Dorn, R.I., de Niro, M.J., and Ajie, H.O., 1987, Isotopic evidence for climatic influence on alluvial-fan development in Death 

Valley, California: Geology, v. 15, no. 2, p. 108-110. 

LaMarche, V.C., Jr., 1973, Holocene climatic variations inferred from treeline fluctuations in the White Mountains, California: 

Quaternary Research, v. 3, p. 632--660. 

Lustig, L.K., 1965, Clastic sedimentation in Deep Springs Valley, California: U.S. Geological Survey Professional 

Paper 352-F, p. 131-192. 

Nilsen, T.H., ed., 1985, Modem and ancient alluvial fan deposits: New York, Van Nostrand Reinhold, 372 p. 

Sawyer, T.L., 1990, Quaternary geology and neotectonic activity along the Fish Lake Valley fault zone, Nevada and 

California: Reno, University ofNevada, Masters thesis, 379 p. 

Scuderi, L.A., 1987, Glacier variations in the Sierra Nevada, California, as related to a 1200-year tree-ring chronology: 

Quaternary Research, v. 27, no. 3, p. 220-231. 

92 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Slate, J.L., 1992, Quaternary stratigraphy, geomorphology, and geochronology of alluvial fans, Fish Lake Valley, Nevada 

and California: Boulder, University of Colorado, Ph.D. dissertation, 241 p. 

Spaulding, W.G., 1985, Vegetation and climates of the last 45,000 years in the vicinity of the Nevada Test Site, south-central 

Nevada: U.S. Geological Survey Professional Paper 1329, 83 p. 

Stuiver, M., and Pearson, G. W., 1986, High-precision calibration of the radiocarbon time scale, AD 1950-500 BC: 

Radiocarbon, v. 28, p. 805-838. 

Wells, S.G., McFadden, L.D., and Dohrenwend, J.C., 1987, Influence oflate Quaternary climatic changes on geomorphic and 

pedogenic processes on a desert piedmont, eastern Mojave Desert, California: Quaternary Research, v. 27, no. 2, 

p. 130-146. 

ABSTRACTS OF PRESENTATIONS 93 

Preliminary Report on the Ostracod Record from 

Pyramid Lake, Nevada 

Alison J. Smith, Department of Geology, Kent State University 

A preliminary investigation of the ostracod 

record from Pyramid Lake sediments (trenches PLT8 7, 

PLT91-2; cores PLC87-2, PLC87-4, PLC91-1, and 

PLC91-2) indicated a faunal assemblage similar to that 

indicated by records from Walker Lake, Nevada 

(Bradbury and others, 1989), and the San Agustin 

Plains, New Mexico (Markgraf and others, 1983; 

Phillips and others, 1992). This similarity wa.." offset 

by the unusually low abundance of ostracods in the 

Pyramid Lake samples as compared to samples from 

Walker Lake. Therefore, the ostracod record from 

Pyramid Lake is not as detailed as the records obtained 

from other previously studied saline systems. 

An analysis of 150 samples obtained from the 

64.5-m record of sediment cores indicated that the 

dominant species throughout most of the history of 

Pyratnid Lake were alternately Limnocythere 

ceriotuberosa and Limnocythere bradburyi (fig. 1). 

These ostracod~ are benthic, euryhaline species that 

inhabited saline water in which calcium wa..~ depleted 

CJ) 

0:: 

15 

20 

~ 25 

w 

2 30 

z 

-~ 35 I 

b: 40 w 

Cl 

45 

50 

60 

relative to bicarbonate (Forester, 1983, 1985, 1987; 

Smith, 1993). Both species are living today in calciumdepleted, bicarbonate-enriched saline lakes that have 

dissolved-solids concentrations ranging from 1,050 to 

11,500 mg/L (Smith, 1993; R.M. Forester, 

U.S. Geological Survey, written commun., 1993). 

These species are not known to co-occur in the modem 

world. In the sediment cores from Pyramid Lake, as in 

the cores from Walker Lake and the San Agustin 

Plains, there was some overlap in the ostracod 

distributions that may be due to the sediment 

accumulation rates and sediment mixing. The species 

L. bradburyi is confined today to shallow saline lakes 

in the Southwest United States and Mexico, and its 

northernmost known occurrence is Rhoad Forks Playa, 

New Mexico (R.M. Forester, oral commun., 1993). 

The species L. ceriotuberosa is distributed in deep and 

shallow lakes north of the frost line and extends into the 

northern Midwest United States and northward into the 

Canadian Great Plains (Delorme, 1971; Smith, 1993). 

50 100 0 16 32 48 64 0 6 12 18 24 0 10 20 30 0 2 0 8 0 100 200 0 24 48 72 

Limnocythere Limnocythere Limnocythere Candona Hetero- Cyprideis 

ceriotuberosa bradburyi platyforma rawsoni cypris sp. beaconens is 

VALUES PER GRAMS 

GRAM OF OF 

SEDIMENT SAMPLE 

NUMBER OF VALUES 

Figure 1. Fossil ostracod abundance with depth in Pyramid Lake cores. 

ABSTRACTS OF PRESENTATION 95 
These distributions are strongly indicative of a 

temperature control on the life cycles of the two 

species. The species L. bradburyi may be unable to 

reproduce and thrive in regions that have seasonal 

variation in temperature, whereas L. ceriotuberosa 

may be unable to reproduce and thrive in regions that 

do not have strong seasonal temperature fluctuations 

(Forester, 198 7). 

The oxygen isotope values from the Pyramid 

Lake carbonates can be cmnpared with the distribution 

of the two ostracod species in the cores. When 

L. bradburyi is abundant, the associated carbonates are 

isotopically light, whereas when L. ceriotuberosa is 

abundant, the associated carbonates are isotopically 

heavier. Because both species inhabit lakes that have 

similar water composition and concentration and, yet, 

are geographically incompatible in the modern world, 

one interpretation is that these species are indicators of 

temperature changes. On the basis of that 

interpretation, the L. bradburyi peaks that coincide 

with the isotopically light values from the carbonates 

would indicate warmer air and water temperatures than 

the L. ceriotuberosa peaks that precede and follow 

L. bradburyi. 

The presence of L. platyjorma at the base of 

the core sequence is an additional point of interest. 

The species L. p/atyforma is a rare species in the 

modem world. Modem geographic locations include 

Canadian prairie lakes (Delorme, 1971 ); the species 

also has been reported in the Pleistocene records from 

the San Agustin Plains (Phillips and others, 1992). It is 

associated in the modern world with fresher watermore dilute water in which calcium is not depleted 

relative to bicarbonate--than is L. ceriotuberosa. 

A multivariate statistical method known as the 

modem analog technique (Overpeck and others, 1985) 

was applied in this study to the ostracod record from 

Pyramid Lake. The modern distributions of 70 taxa 

and associated hydrochemistry from 250 lacustrine, 

spring, and wetland sites located throughout the 

Western United States, Mexico, midcontinent, and 

Alaska were used as the calibration data set. By 

comparing the fossil a..~semblage in each srunple with 

the modern calibration data set using a distance 

measure [in this ca..'ie, the presence-absence mea..'iure 

known as the Jaccard coefficient (Pielou, 1984)], and 

the Multivariate Statistical Package (MVSP) computer 

program (Kovach, 1990), a 111odem analog for each 

fossil assemblage was obtained. 

The modem analogs for most of the Pyramid 

Lake ostracod record are modem Pyramid Lake and 

Walker Lake. However, the best modem analog for the 

L. bradburyi assemblages that are present in cores at 

10.21, 17 .15, and 17.57 m is Rhoad Forks Playa, New 

Mexico, which implies a time in which annual air 

temperature was higher, seasonality was decreased 

(warmer winters), and runoff or surface input 

decreased. In the past, L. bradburyi may have been 

present in lakes that were much deeper than the playas 

. in which the species is present today and as represented 

in the modern data set. Large lakes that have an 

extensive pan-shaped littoral zone could provide a 

habitat suitable for L. bradburyi, as long as the 

temperature and seasonality limitations are met. There 

is no modem analog for the L. platyforma assemblage 

at the base of the core sequence because there is no L. 

platyforma in the modem data set. However, based on 

the limited information available on this species, it can 

be inferred that the lake basin probably was receiving 

more surface runoff or input, the water was fresher, and 

seasonality was enhanced (cooler winters). 

These results correspond well with the oxygen 

isotope record in the cores. In general, the heavier 

isotope values are associated with L. ceriotuberosa and 

L. platyforma, indicating cooler annual temperatures 

and enhanced seasonality. The lighter isotope values 

are associated with L. bradburyi, indicating a change to 

warmer air temperatures and decreased seasonality. 

One difficulty with the Pyramid Lake ostracod 

record is that it is relatively sparse compared with 

records from other saline lakes, such as Walker Lake 

and Mono Lake. This paucity of ostracods may be the 

result oflocation of the core sites away from a sediment 

focus point or of post-depositional dissolution of the 

ostracods. An additional problem with the ostracod 

record is the high abundance of reworked material, 

indicating that many of the shells have been 

transported from other depositional sites. Continued 

analysis of more samples from Pyi-amid Lake may 

produce srunples that have higher ostracod abundances. 

Isotopic analysis of the ostracod shells could provide a 

direct link to the faunal-climate record. 

96 Proceedings of the Workshop "Ongoing Paleoclimatic Studies In the Northern Great Basin," Reno, Nevada, May 1993 
REFERENCES 

Bradbury, J.P., Forester, RM., and Thompson, R.S., 1989, Late Quaternary paleolimnology of Walker Lake, Nevada: 

Journal of Paleolimnology, v. 1, p. 24 7-267. 

Delorme, L.D., 1971, Freshwater ostracodes of Canada-Part 5, Families Limnocytheridae, Loxoconchidae: Canadian 

Journal of Zoology, v. 49, no. 1, p. 43--64. 

Forester, R.M., 1983, Relationship of two lacustrine ostracod species to solute composition and salinity; implications for 

paleohydrochemistry: Geology, v. 11, no. 8, p. 43 5-43 8. 

__ 1985, Limnocythere hradhw:vi, n. sp.; a modem ostracod from central Mexico and a possible Quaternary paleoclimatic 

indicator: Journal of Paleontology, v. 59, no. 1, p. 8-20. 

__ 1987, Late Quaternary paleoclimate records trom lacustrine ostracodes, in Ruddiman, W.F., and Wright, H. E., Jr., eds., 

North America and adjacent oceans during the last deglaciation: Boulder, Colo., Geological Society of America, 

The Geology of North America, v. K-3, p. 261-276. 

Kovach, W., 1990, MVSP (Multivariate Statistical Package) Plus, version 2: Aberystwyth, United Kingdom, University 

College of North Wales at Aberystwyth, (software for personal computer). 

Markgraf, Vera. Bradbury, J.P., Forester, R.M., McCoy, W., Singh, G .• and Sternberg, R., 1983, Paleoenvironmental 

reassessment of the 1.6 million year old record trom San Agustin Basin, New Mexico, in Chapin, C.E., ed., Socorro 

_region II: New Mexico Geological Society Guidebook 34, p. 291-297. 

Overpeck, J.T., Webb, T., III, and Prentice, I. C .• 1985, Quantitative interpretation of fossil pollen spectra-Dissimilarity 

coefficients and the methods of modern analogs: Quaternary Research, v. 23, p. 87-108. 

Phillips, F.M., Campbell. A.R., Kruger, C., Johnson. P., Roberts, R., and Keyes, E., 1992, A reconstruction ofthe response of 

the water balance in Western United States lake basins to climate change: New Mexico Water Resources Institute 

Technical Completion Report 1345662, WRRI Report 269, v. 1, 167 p. 

Pielou, E. C., 1984, The interpretation of ecological data: New York, Wiley, p. 40-62. 

Smith, A.J .• 1993, Lacustrine ostracods as hydrochemical indicators in lakes of the north-central United States: Journal of 

Paleolimnology, v. 8, p. 121-134. 

ABSTRACTS OF PRESENTATIONS 97 

Lithologic Variations in Core OL92 from Owens Lake, 

California, and Their Probable Climatic Significance 

George I. Smith and James L. Bischoff, U.S. Geological Survey 

Jonathan Glen, University of Cal(fornia, Santa Cruz 

Owens Lake, in southea'it California, was 15 m 

deep and covered about 290 km2 in 1872 when it wa'i 

the terminus of the Owens River, which drains the east 

side of the high Sierra Nevada. Although it has been 

dry since about 1920 as a result of construction of the 

Owens Valley Aqueduct in the early 1900's, Owens 

Lake was the first in a chain of as many as five lakes 

that were created as a result of the increased volume of 

water received during the pluvial periods of the 

Pleistocene. To obtain a more complete record of 

variations in runoff during these pluvial periods, three 

7 .6-cm-diameter cores were obtained from adjacent 

sites on Owens Lake in late spring 1992. The three 

cores extend from 0.00 to 7.16 m (100 percent 

recovery), 5.49 to 61.37 m (80-85 percent recovery), 

and 61.26 to 322.86 m (75-79 percent recovery); and 

together, these cores represent about 800,000 yr of 

sedimentation. The core site is in the south-central part 

of the now-dry lake (SE comer of sec. 9, T. 18 S., 

R. 37 E., Mount Diablo Meridian) and about 4 km from 

the nearest pre-1900's shore. 

Except for 2 to 3 m of salts on the surface, which 

formed during this century, all of the sediments appear 

to be perennial lake deposits. A 4.2-m-thick oolite bed 

underlies the salts, and a 14C date on humus in the dark 

silt or clay immediately beneath the oolite layer 

indicates that its deposition began shortly after 

8,930 ± 70 yr B.P. Below the oolite bed, clay, silt, and 

a little sand characterize the underlying 200± m of lake 

fill. Fine to coarse sand and less common silt and clay 

characterize the lowest 100± m of sediments. Notable 

concentrations offish scales and bones, aquatic 

mollusk shells, and plant fragments and seeds occur in 

two 20-m-thick zones centered near 200- and 300-m 

depths. A thick bed of volcanic ash (303.5 to 

309.1 m) has been identified as airfall and reworked 

Bishop Tuff (758,000 ± 2,000 yr B.P.); the top of the 

Brunhes-Matuyama magnetic polarity reversal is near 

320m. 

Many of the fine sediments in the upper 200± m 

of core are moderately well bedded, with clast size or 

subtle color changes defining the beds. Many beds are 

massive or mottled (bioturbated?), and laminar 

bedding is rare. In this interval, beds of coarse to very 

coarse sand were noted near67 m (0.25 m thick) and 95 

m ( 1.25 m thick); the deeper bed contained methane 

under high pressure. The grain sizes of sediments in 

the lower 100 m of the core are more variable and 

include lacustrine(?) sediments ranging from clay to 

very coarse sand that may include a few granules or 

very small pebbles. Besides the Bishop Tuff, several 

additional beds tentatively identified as tephra are 

being studied. 

The 200± m of fine-grained sediments 

underlying the near-surface oolite bed appear to 

represent deep-water perennial-lake deposition since 

about 500,000 yr B.P. (using the apparent overall 

perennial-lake sedimentation rate--2,500 yr/m-for 

estimating their age). The two coarse sand beds in this 

interval apparently represent nonclimatic events, 

because neither bed is underlain or overlain by 

sediments indicating a shallowing or deepening of the 

lake. This would be expected in a transitional stage 

before or after a brief, climatically caused shallowwater episode (study of the fossil content of these zones 

may change this interpretation). The lowest 1 00± m of 

coarser, more variable sediments, including four zones 

containing coarse to very coarse lacustrine sand, 

suggest a 300,000-yr period of fluctuating lake levels 

that included four or more shallow, but not dry, periods, 

although a flood-plain environment cannot be ruled out 

at this time. However, this 1 00± m interval also 

includes repeated zones of interbedded clay, silt, and 

very fine sand that show that periods when the lake was 

also deep and possibly overflowing recurred many 

times-an interpretation that is compatible with the 

record from Searles Lake, which was downstream from 

Owens Lake during pluvial periods. 

In the late 1800's, Owens Lake waters had a 

salinity of 6 to 9 percent. The oolite bed near the 

surface is interpreted to represent a period of saline 

lakes that were ( 1) shallow (allowing wind energy to 

produce currents on the bottom) and (2) constantly 

ABSTRACTS OF PRESENTATION 99 
saturated or supersaturated with CaC03 (so that 

carbonate deposition would overwhelm clastic 

deposition). Assuming that the lower I 00 m of 

sediments are eventually detennined to be lacustrine, 

the absence of similar oolite beds in the deeper parts 

of the OL92 core sequence is interpreted to mean 

that, in this area (and probably in a much larger 

area as well), the past 9,000 yr have been more 

arid than during any period in the past 800,000± yr and 

have been characterized by several high-latitude 

glacial-interglacial cycles. 

100 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Sedimentary Record of Climatically Induced Lake-Level 

Fluctuations, Pyramid Lake, Nevada 

Joseph P. Smoot, U.S. Geological Survey 

Pyramid Lake is a large, perennial, terminal lake 

that was part of the late Pleistocene Lake Lahontan. 

Shoreline deposits and outcrops of lacustrine material 

attest to dramatic changes in the depth and area of the 

lake during the past few thousand years that are 

attributed to fluctuations in regional rainfall and 

evaporation. A core (PLC87) obtained on the-north 

side of the lake about 1.5 km from the lake shore 

penetrated 65 m of unconsolidated sediment overlying 

Tertiary volcanic rocks. The upper 3m of sediment 

were not cored, but were sampled from a trench 

(PLT87). The sedimentary structures in this core were 

analyzed to determine their sensitivity to changes in 

lake depth that indicate changes in climate. 

Most of the sedimentary variability in 

core PLC87 is within seven categories that are 

interpreted as indicators of different lake depths. In 

the first category, brecciated silts and clays are 

interpreted as lake sediments that were desiccated 

during subaerial exposure. Root cast~ and gypsum 

crystals are common accessories. In the second 

category, oscillatory rippled sand formed in relatively 

shallow water (less than 3 m in the modern lake) and 

thin clay drapes or flasers (in clay lenses), were present 

in the deeper formations. In the third category, sand 

lenses within bioturbated clay represent storm wave 

deposits in conditions where settling out of silt and 

clay was the nonn. The sand lenses range from layers 

of oscillatory ripples like those formed in shallower 

water to low-amplitude pinch-and-swell laminae that 

represent rolling-grain oscillatory ripples in tnuch 

deeper water. The bioturbated clay contains ostracods 

and sand-filled burrows. The depth range for the 

formation of this sedimentary category depends on the 

surface area of the lake and the scale of storms and 

probably varied through time. In the fourth category, 

graded silt laminae in bioturbated clay are interpreted 

as storm lag layers in a deeper water setting. The silt 

laminae consist mostly of skeletal material that was 

dispersed within the bioturbated clay, then 

concentrated in layers with no orientation, indicating 

transport as waves winnowed the finer matrix. As in 

the third category, the absolute depth for this wave 

activity depends on the size of the lake, but the water 

needed to be deeper than that for the pinch-and-swell 

laminae. In the fifth category, silty clay containing 

random burrows represents deposition caused by 

settling out below wave base. Skeletal material in 

these muds is generally smaller than that in the 

shallower water deposits, which were possibly 

dominated by pelagic organisms. The bioturbation 

indicates that infaunal organisms randomly burrowed 

the upper part of the sediment, indicating oxygenated 

conditions. This category of structure in core PLC87 is 

coincident with lighter carbon and oxygen isotopes 

measured by L.V. Benson (unpublished data). Benson 

interprets the isotope shift from heavy to light as a 

transition from closed- to open-basin conditions as the 

lake exceeded spillover height. The lowest spillover 

that would produce this change is 3 7 m higher than the 

elevation of the core site, which can be used as a 

minimum depth for this deposit. In the sixth category, 

clays dominated by horizontal burrows and partial 

preservation oflaminae represent conditions below the 

wave base where oxygen is very depleted at the 

sediment-water interface. The burrows are smaller in 

diameter than those of the randomly burrowed muds, 

and the skeletal debris is totally dominated by pelagic 

organisms; both conditions were consistent with 

oxygen-depleted bottom water, probably due to greater 

lake depths. This change is interpreted as being depth 

controlled rather than controlled by salinity or 

seasonality. Because the deposits are only transitional 

to randomly burrowed mud and flat-laminated mud, 

they have only light isotopic signatures, and their 

thicknesses are too large to represent deposition for 

periods less than several tens of years. In the seventh 

category, flat, continuous laminae of graded silt or 

alternations of clay and biogenic or calcareous material 

are interpreted as deposits settling out on an anoxic 

lake bottom, as indicated by the absence of 

bioturbation. The graded silt laminae are associated 

with pebbles and cobbles that randomly penetrate the 

laminae in a manner consistent with drop stones. 

These deposits are interpreted as representing ice cover 

allowing saltation of coarser material over larger areas 

ABSTRACTS OF PRESENTATION 101 
and transportation of cobbles-and pebbles in ice floes. 

The highest shorelines around Pyramid Lake are 150 m 

above the elevation of the drill site, which probably 

indicates the upper range of the deepest lakes. 

The seven sedimentary categories are present in 

systematic successions that indicate the rise and fall of 

lake level at a variety of time scales. Transitions from 

deepest water deposits (categories 6 and 7) to 

shallowest water or subaerial deposits (categories I and 

2) are present over intervals of about I 0 m. Smaller 

scale changes are present rhythmically at the scales of 

3m and decimeters. The changes in sedimentary 

categories are gradational, except for wave deposits 

that commonly have abrupt contacts with underlying 

deeper water deposit~ or subaerial deposits. The sharp 

contacts are interpreted as erosional surfaces with 

depths that cannot be assessed from the core. In all of 

the depth-change intervals, the transgressive deposit is 

characteristically thinner than the regressive deposit 

and may have resulted from sediment depletion during 

transgression as lake water flooded drainages. During 

regression, these sediments would be eroded and 

transported lakeward, producing a thicker sedimentary 

sequence. 

Core PLC8 7 may, in part, be correlative to the 

Truckee River Canyon deposits that have the 

Wadsworth tephra in the middle and are capped by tufa 

dated at about 12,500 yr B.P. The lake must have been 

more than I 00 m deep at the core site for deposition of 

the clay sequence in the canyon. Therefore, 

sedimentary categories 6 and 7 are the only likely 

correlative deposits in the core. If the lake dropped to 

levels below 60 m deep at the core site, the canyon 

sequence was subaerially exposed. The difference in 

sedimentation rates between the core site and the 

canyon make relative thicknesses a poor tool for 

comparison. 

102 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
Uranium-Series Dating of Tufas from Pyramid Lake, Nevada 

Barney J. Szabo and Larry V. Benson, U.S. Geological Survey 

Pyramidal tufa mounds (as much as 100m in 

height) border the present shore of Pyramid Lake in 

Nevada. The elevations of the tops of many ofthese 

mounds correspond to elevations ofintcrsubbasin sills. 

Although the late Pleistocene highstands of Pyramid 

Lake are well studied, the relation of the tufa mounds 

to lake level has not been previously documented. A 

reconnaissance survey of the tufa mounds indicated a 

variety of morphologies. Varieties of tufas sampled for 

dating included dense laminated, branching, nodular, 

platy, and concentrically laminated tubular tufas. 

Precipitation probably occurred where the calciumrich ground water mixed with carbonate-rich lake 

water. 

The U-series ages oftnore than 30 samples 

collected at elevations between 1,160 and 1,220 m 

indicate that at least some, and possibly most, of the 

pyramidal mounds formed between about 40,000 and 

13,000 yr B.P. These results are consistent with 

unpublished 14C ages of the same tufa samples that 

were determined by M. Kashgarian (written commun., 

1993 ). The water in Pyramid Lake stood above 

1,177 m during ~40,000 to 30,000 yr B.P., and the 

Pyramid Lake and Winnemucca Lake (Nevada) 

subbasins were usually connected. During 

approximately 23,000 to 16,000 yr B.P., Pyramid Lake 

stood at or above about I ,207 m, indicating that lakes 

in the Pyramid Lake, Winnemucca Lake, and Smoke 

Creek-Black Rock Desert subbasins had coalesced. 

The U-series ages of laminated tufas that line the walls 

of a small cave at Marble Bluff on the southeastern 

part of the Pyramid Lake subbasin at an elevation of 

1,204 m indicate that lakes in the Pyramid Lake, 

Winnemucca Lake, and Smoke Creek-Black Rock 

Desert subbasins probably were connected between 

about 400,000 and 170,000 yr B.P. 

Chemical analyses of the tufa samples indicate 

the presence of a small acid-insoluble residue having as 

much as 40 Jlglg uranium, 3,700 Jlg/g thorium, and 

4, 700 percent excess 230rrh activity relative to 234U. 

This residue probably wa..li transported as a colloidal 

suspension in ground water, which discharged through 

the tubular structure present in the bases of tufa 

mounds. 

ABSTRACTS OF PRESENTATION 103 

Changes in the Pyramid Lake, Nevada, Drainage Basin as 

Indicated by the Organic Content of Recent Sediments 

Gabrielle E. Tenzer and Philip Meyers, Department of Geological Sciences, 

University of Michigan 

Organic-matter contents of lake sediments 

indicate the amounts and types of biota that have 

inhabited lake environments. Indicators of organicmatter sources can provide information about lake 

productivity (changes in the amount and type of 

aquatic-source material) and about changes in climate, 

river runoff, and land-use practices (changes in the 

amount and type of terrigenous source indicators). A 

number of organic-matter-source signals have been and 

are presently ( 1993) being analyzed in sediment cores 

from Pyramid Lake to determine changes in the lake 

systen1. Biomarkers from core 2, collected in 1976 just 

to the west of Anaho Island, were analyzed by Meyers 

and others ( 1980). First, a decrease in the n-C29 to 

n-C 17 ratio at a depth of approximately 1 111 was 

concluded to represent a change from oligotrophy to 

mesotrophy at around A.D. 1300 to 1400. Second, an 

increase in n-alkanoic acid concentrations in the top 

3 0 em, unaccompanied by any such increase in alkane 

concentrations, was interpreted a~ a preservational 

effect resulting from an increase in the rate of 

sedimentation. Finally, the various geolipids within the 

core were postulated to be primarily terrigenous in 

origin and supplemented by aquatic sources. In the 

absence of measured sedimentation rates, 

interpretations from the study by Meyers and others 

( 1980) were based on the known history of the drainage 

ba~in and on sedimentation rates of nearby Walker 

Lake. The 210Pb dating of Pyramid Lake cores 96A, 

93A, and 93L collected in 1991 allow these previous 

interpretations to be examined within an improved 

chronological framework. 

A combination of isotopic, elemental, and 

molecular determinations have been obtained for cores 

96A, 93L, and for the very top part of core 93A (fig. 1). 

Dry-weight percent CaC03 was analyzed by the 

carbonate bomb method, and values were verified 

using a UIC/Coulometrics C02 coulometer. All 

2ooo~~~~~~~ ~~~~~~~~ ~~~~~~~~ ~~~~~~~ ~~~~~~~ 

1900 

1800 

0:: 1700 

<( 

~ 1600 

0:: 

<( 1500 

0 

z 

~ 1400 

<( 

u 1300 

1200 

1100 

1ooo~~~~~~~ ~~~~~~~~ ~~~~~~~~ ~~~~~~~ ~~~~~~~ 

-28 -27 -26 -25 -24 -23 1 2 3 4 5 9 10 11 12 13 0 1 2 3 4 5 6 7 0 10 20 30 40 50 

()

13C(%o) TOTAL ORGANIC CARBON/NITROGEN n-C17 n-C29 

ORGANIC FRACTION CARBON (MOLES) STRAIGHT CHAIN STRAIGHT CHAIN 

(% C) HYDROCARBON,17 HYDROCARBON,29 

CARBON ATOMS LONG CARBON ATOMS LONG 

(MOLE FRACTION) (MOLE FRACTION) 

Figure 1. Selected chemical characteristics of shallow- and deep-basin cores in the Pyramid Lake drainage basin. Open 

circles represent cores 93A/L (shallow basin), and solid circles represent core 96A (deep basin). Isotopic values are relative 

to PDB; TOC values are total organic-carbon wet-weight percentages; C/N ratios are molar; and the hydrocarbon (HC) 

values are in 1 03 ng/g organic carbon. 

ABSTRACTS OF PRESENTATION 105 
inorganic carbon wa~ assumed to be present as CaC03. 

Total organic-carbon (TOC) values and C/N ratios 

were obtained using a Perkin-Elmer 2400 CHN 

elemental analyzer after removal of carbonates using 

3N HCI. These carbonate-free samples were analyzed 

for 8 13Corg using a Finnigan MAT Delta-S mass 

spectrmneter. Organic compounds, including fatty 

acids and straight-chained hydrocarbons, were 

extracted by sonication using dichloromethane. Fatty 

acids were converted to their methyl esters after having 

been saponified using BF3. Unsaponified and 

saponified fractions were separated in petroleum ether 

and toluene, respectively, using alumina.over silica gel 

columns. Geolipid fractions were analyzed using a gas 

chromatograph that had an automatic injector and a 

flame ionization detector. 

The TOC values were higher in core 96A than in 

cores 93A/L. These higher values for core 96A were 

probably due to a finer grain-size distribution and a 

higher mass-accumulation rate at the deeper site. 

Core 96A is located farther from the Truckee River 

input, thereby decreasing any dilution of the TOC 

signal by river input, as may have been happening at 

the core 93A/L sites. In contrast, C/N ratios were 

higher in cores 93A/L, as was the long-chained 

hydrocarbon content (Ln-C27, n-C29, n-C31 ) of cores 

93A/L. Both of these signals indicated a larger amount 

of terrigenous input to the shallow basin of Pyramid 

Lake, which was to be expected considering the 

location of the Truckee River inlet with respect to the 

shallow and deep basins. On average, there is a higher 

aquatic-source-material signal in the deep basin as 

indicated by the short-chained hydrocarbon content of 

core 96A. A comparison of the short- and long-chained 

hydrocarbon contents ofboth cores indicated an overall 

domination of the organic sedimentary material of the 

lake by terrigenous sources, as was suggested by 

Meyers and others ( 1980). The C/N molar ratios of 

about 10-12 and an organic-carbon flux study for 

Pyrrunid Lake by Galat ( 1986), however, indicated the 

dominance of autochthonous sources. The 

predominance of long-chained hydrocarbons is 

probably due to the higher proportion of n-alkanes in 

land-derived organic material in comparison to lake 

algae (Cranwell and others, 1987; Goossens and others, 

1989~ Meyers and Ishiwatari, 1993). 

Decreases in long-chained hydrocarbon content 

were interpreted as periods of decreasing river 

runoff and more arid climate conditions in the Pyramid 

Lake drainage basin. rhis interpretation is supported 

by some evidence from archaeological findings 

(Hattori and Tuohy, this volume). These periods of 

increasing dryness were indicated in core 96A from 

approximately A.D. 1600 to A.D. 1750, A.D. 1780 to 

1860, and A.D. 1890 to 1960 (includes the Dust Bowl) 

and in cores 93A/L from approximately A.D. 1030 to 

1130, A.D. 1230 to 1420, A.D. 1790 to 1945, and 1970 

to about 1980 to the top of the core. A distinct increase 

in n-C29 in core 96A, which also may occur in cores 

93A/L from approximately A.D. 1860 to 1920, 

corresponded to a period of logging and agricultural 

development in the Pyramid Lake drainage basin. The 

decrease in n-C29 in core 96A after 1920 may be a 

delayed effect of the Derby Diversion Dam, 

constructed in 1905, to provide irrigation in the FallonCarson Desert areas. 

106 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 
REFERENCES 

Cranwell, P.A., Eglinton, G., and Robinson, N., 1987, Lipids of aquatic organism-; as potential contributors to lacustrine 

sediments--II: Organic Geochemistry, v. 11, p. 513-527. 

Galat, D.L., 1986, Organic carbon flux to a large salt lake, Pyramid Lake, Nevada, U.S.A.: Intermediate Revue der Gesamten 

Hydrobiologic, v. 71, p. 621-654. 

Goossens, H., Duren, C., de Leeuw, J.W., and Schenck, P.A., 1989, Lipids and their mode of occurrence in bacteria and 

sediments--11, Lipids in the sediment of a stratified, freshwater lake: Organic Geochemistry, v. 14, p. 27-71. 

Meyers, P.A., Maring, H.B., and Bourbonniere, R.A., 1980, Alkane and alkanoic acid variations with depth in modem 

sediments of Pyramid Lake, in Douglas, A.G., and Maxwell, J.R., eds., Advances in organic geochemistry, 1979: 

Oxford, Pergamon, p. 365-374. 

Meyers, P.A., and Ishiwatari, R., 1993, Lacustrine organic geochemistry-An overview of indicators of organic matter 

sources and diagenesis in lake sediments: Organic Geochemistry, v. 20, p. 867-900. 

ABSTRACTS OF PRESENTATIONS 107 

Late Quaternary Vegetation and Stable-Isotope Record 

from the Lahontan Basin 

Peter E. Wigand, Quaternary Sciences Center, Desert Research Institute, Reno, Nevada 

Plant macrofossil and stable-isotope data from 

multiple strata of a single fossil woodrat (Neotoma 

spp.) den (midden) on the former western shore of 

pluvial Lake Lahontan extend the paleoclimatic proxy 

record for this area to 30,000 yr B.P. These data 

indicate Pleistocene depressions of distributions of 

plant species of as much a..'i 1, 100 n1 and horizontal 

extensions ranging as much as 30 km in northwestern 

Nevada. 

Changes in plant cotnmunity composition 

indicate three periods of effectively moister climate 

generally coincident with expansions of pluvial 

Lake Lahontan, approximately 24,000 yr B.P., 

between about 16,000 and 12,000 yr B.P., and about 

10,700 yr B.P. The first two periods were typified 

by expansion, down to 1,380 m, ofwhitebark pine 

(Pinus albicaulis) into Utah juniper (Juniperus 

osteosperma) woodland. During the second period, 

approximately 16,000 to 12,000 yr B.P., increased 

importance of sagebrush (Artemisia sp.) in the 

understory was markedly greater than during the earlier 

period, and mountain mahogany ( Cercocarpus 

ledifolius) was depressed as much as 330 tn in 

elevation. The latest period, approximately 10,700 yr 

B.P., wa..'i typified by the maintenance of Utah juniper 

woodland in areas as much as 20 km beyond where it 

presently ( 1993) occurs. 

Variations in the proportions of heavy isotopes of 

carbon and hydrogen in radiocarbon-dated Utah 

juniper from the same midden (and confirmed by stable 

isotopes from other middens in the region) recorded the 

corresponding three periods of effectively wetter 

climate. Coincident maximums in Utah juniper seed 

length probably indicated increased productivity 

resulting from greater effective precipitation. Greater 

woodrat-dung widths probably indicated increased 

woodrat size due to cooler temperatures. Together, 

these data indicate that the temperature decreased and 

precipitation increased at about 24,000 yr B.P. and that 

temperature decreased between about 14,000 and 

12,000 yr B.P., but the precipitation increases were 

smaller than the increases that occurred at about 

24,000 yr B.P. Apparent breaks in the woodrat midden 

record between 28,000 and 25,000 yr B.P. (last 

interstade), between 20,000 and 16,000 yr B.P. (glacial 

maximum), and between 8,000 and 4,000 yr B.P. 

(Altithermal) may indicate periods when 

environmental conditions were locally too dry, too 

cold, or too hot for woodrats to flourish. 

ABSTRACTS OF PRESENTATION 109 

Sedimentary Facies, Quaternary History, and Paleoclimatic 

Implications from Sediments in Mohawk Valley, California 

James C. Yount. DavidS. Harwood. John P. Bradbury. Andrei M. Sarna- Wojcicki, and 

Charles E. Meyer, U.S. Geological Survey 

Mohawk Valley is along the Middle Fork of the 

Feather River between the Sierra Valley and Quincy, 

California. The floor of Mohawk Valley is at 

approximately the 1 ,280-m elevation, at the 

intersection of the Feather River and Sulphur Creek. 

The crest of the Sierra Nevada is west of Mohawk 

Valley, and summit elevations reach 2,589 m. Typical 

elevations are in the range of 1,980 to 2,290 m. 

Although the Sierra Nevadan crest is west of Mohawk 

Valley, the actual drainage divide separating the 

westward-flowing Feather River from drainage to the 

east is at Beckworth Pass on the east edge of the Sierra 

Valley. This eastward position of the drainage divide 

indicates past capture of the Sierra Valley drainage by 

the Feather River. 

Tertiary volcanic rocks, including thick sections 

of intermediate composition lahar, debris flow, and 

lava, surround Mohawk Valley on the north and east. 

Pre-Tertiary metavolcanic, metasedimentary, and 

plutonic rocks are west and south of the valley. These 

pre-Tertiary rocks underlie most of the area that was 

glaciated to the southwest of Mohawk Valley. The 

contrast in source-rock lithology across the valley aids 

in separating glacial outwash from fluvial Feather 

River deposits, particularly in the older part of the 

Quaternary section. 

In the 1890's, Turner ( 1891) interpreted the 

sedimentary section at Mohawk Cliff as lacustrine and 

assigned the strata there the name Mohawk Lake Beds. 

This interpretation was continued by Durrell ( 1987), 

who postulated a lake filling Mohawk Valley whose 

shore followed the 1,585-m contour. The lake, 

impounded by a large landslide at Consignee Creek, 

may have had a water depth of as much as 150m in its 

central part. The original outlet of the lake may have 

been located at Poplar Creek, a few kilometers 

southwest of the present ( 1993) exit of the Feather 

River out ofMohawk Valley. Durrell ( 1987) suggested 

that headward erosion by the Feather River through the 

Consignee Creek landslide may have been completed 

sometime during the late Pleistocene or Holocene and 

that this breach may have resulted in rapid lake 

emptying and subsequent erosion and exposure of the 

sedimentary fill in Mohawk Valley. 

The studies discussed in this report confirmed 

that erosion has recently exposed the sediments of 

Mohawk Valley, but tnost of these sediments may have 

accumulated in meadow or braided-stream 

environments, and there tnay have been periodic 

contributions of glacial outwash from ice advancing 

out of the Gold Lakes and Lakes Basin area southwest 

of Mohawk Valley. The only lacustrine sediments that 

were recognized in the valley-fill sequence were 

pro glacial sediments of limited extent that are 

associated with the glacial outwash facies. Rather than 

rapid exhumation of the section following the 

emptying of the hypothesized lake by stream capture, 

recent tectonic activity along the Quaternary faults that 

bound Mohawk Valley may have altered the Feather 

River grade and encouraged downcutting. 

The eastern arm of Mohawk Valley, extending 

from Clio to Portola, contains as much as 100 m of 

trough cross-bedded cobble to pebble gravel and planar 

and trough cross-bedded coarse and medium sand, 

which is interpreted as braided-stream deposits. 

Sections exposed in the western arm ofMohawk Valley 

consist, in their lower parts, of pebble gravel, which is 

dominated by pre-Tertiary clasts and is interpreted as 

glacial outwash that is overlain by massive organicrich silt and clay interbedded with blocky to fissile peat 

beds as much as 1 m thick. Diatmn assemblages are 

dominated by benthic species of Cocconeis, Cymbe/la, 

Epithemia, Eunotia, Fragilaria, Gomphonema, 

Navicula, Pinnularia. and Surirella, indicating fresh 

marsh environments that had very shallow water 

depths of 1 m or less. The peaty intervals contain the 

Rockland Ash ( 400,000 yr B.P.) in their lower parts and 

Summer Lake LL (180,000 yr B.P.) and TuleLake 

2079, 264, or 2036 (155,000-160,000 yr B.P.) tephra 

layers. 

The fine-grained sections are overlain by glacial 

outwash that was associated with ice descending into 

ABSTRACTS OF PRESENTATION 111 
the valley from the Gold Lakes and Lakes Basin region 

to the southwest. Proglacial lacustrine deposits of 

limited lateral extent are present within the outwash 

complexes as indicated by varved fine-sand and silt 

couplets, poorly sorted quartz-rich silt beds containing 

dropstones, and contorted beds of diamict grading 

laterally into slump blockli surrounded by woodbearing silt and silty sand. A log, buried in diamict and 

slumped into a proglaciallake and lying approximately 

3 km downstream from the Tioga Stage ice termini in 

Jamison and Gray Eagle Creeks, yields an age of 

18,715 ± 235 yr B.P. 

REFERENCES 

Comparison with the eastern Sierra Nevada 

glacial chronology indicates that the late Wisconsin 

deposits are well correlated. Correlation also may exist 

between the oldest outwash in Mohawk Valley and the 

SheiWin Till, although tills with SheiWin properties in 

the Gold Lakes and Lakes Basin area have not been 

identified. 

The peat-rich section in western Mohawk Valley, 

spanning the age range of approximately 500,000 to 

155,000 yr B.P., has no apparent stratigraphic breakli 

and also presents no evidence of outwash correlatable 

to the older Tahoe (Tahoe II), Mono Basin, or pre-

· Mono Basin tills of the eastern Sierra Nevada. 

Durrell, Cordell, 1987, Geologic history of the Feather River country, California: Berkeley, University of California Press, 

337 p. 

Turner, H.W., 1891, Mohawk lake beds: Philosophical Society ofWashington Bulletin, v. 11, p. 385--410. 

112 Proceedings of the Workshop "Ongoing Paleoclimatic Studies in the Northern Great Basin," Reno, Nevada, May 1993 

*U.S. GOVERNMENT PRTNTING OFFICE: 1996 - 774-396 / 26001 REGION NO. 8