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Fluctuation in the level of pluvial Lake Lahontan during the last 40,000 years
Article in Quaternary Research · May 1978 DOI: 10.1016/0033-5894(78)90035-2
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The user has requested enhancement of the downloaded file. QUATERNARY RESEARCH 9,300-318 (1978)
Fluctuation in the Level of Pluvial Lake Lahontan During the Last 40,000 Years
LARRY V. BENSON
Earth Sciences Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California Received July 25, 1977 Samples of algal tufa, gastropods and calcite-cemented-
INTRODUCTION radiocarbon chronology (Frye, Willman, Broecker and his co-workers (Broecker and Black, 1965). This is an alternative and OIT, 1958; Broecker and Walton, 1959; approach, but it assumes rather than proves Broecker and Kaufman, 1965) were the the synchroneity of continental glaciation first to attempt a determination of the abso- with Great Basin pluviation. lute chronology of pluvial Lakes Lahontan --.IThe .-present _ _ study has two objectives: and Bonneville. Their results suggested the development of criteria%%-_ _.“.- the-, s&ction that both lakes were relatively high at of tufa samples- that yield valid radiocarbon 17,000, 14,500, 12,000 and 9500 B.P. How- ages and the development of an -internally ever, Morrison (1965) showed that certain consistent absolute chronology of Lake of Broecker and Kaufman’s (1965) tufa Lahontan fluctuations. ~- dates were stratigraphically reversed. Con- sequently, Morrison and Frye (1965) re- THE LAHONTAN HYDROLOGIC SYSTEM jected the pluvial lake radiocarbon chronol- ogy and correlated the Lahontan and Bon- Three conditions must be met in the west- neville stratigraphies with the Midwestern ern Great Basin to enable the repeated
0033-5894/78/0093-0300$02.00/0 300 Copyright 0 1978 by the University of Washington. All rights of reproduction in any form reserved. FLUCTUATIONS OF PLUVIAL LAKE LAHONTAN 301
FIG. 1. Map showing area1 extent of Lake Lahontan at its highest known level (-- 1330 m). Area1 extent of glaciers in Sierra Nevada was taken from Wahrhaftig and Birman (1965). Solid areas indicate existing lakes. formation and destruction of large fresh- of global climate have occurred during the water lake systems: past two million years. 1. Fluctuations of climate must occur 2. Fluctuations of global climatic param- during the time frame of interest. Several eters must induce correlative fluctuations studies (Emiliani, 1966; Broecker and Van in the water balance of the Great Basin. Donk, 1970; Imbrie and Kipp, 1971; Kukla, That is to say, there must be some mech- 1970; Shackleton and Opdyke, 1973) have anism whereby a global climatic signal is shown that repeated cyclical fluctuations locally expressed. The northern Sierra Nevada achieved a significant topographic TABLE 1 expression at least two million years ago NAMESAND ELEVATIONSOF SILLSCONNECTING (Bateman and Wahrhaftig, 1966) and pro- INDIVIDUAL BASINSTO LAKE vided such a mechanism, transforming LUHOTAN SYSTEM changes in storm frequency and cloud Sill cover into perturbations of the local hydro- elevation logic cycle. Sill name (m) Basin isolated 3. Finally, hydrographically closed basins must be present at the terminations of Adrian 1308 Walker (H) Chocolate 1268 Buena Vista (G) surface drainage networks to contain and Wadsworth 1248 Carson (F) record changes in the regional hydrologic Astor 1225 Honey Lake (I) budget. Such basins have existed in the Emerson 1207 Smoke Creek (C) Great Basin for several million years (Ek- Black Rock (D) Marble 1164 Winnemucca ren et al., 1968). It is therefore reasonable to assume that the western Great Basin has LARRY V. BENSON
probably been the site of pluvial-inter- pluvial cycles for at least the past two million years. The area occupied by pluvial Lake La- hontan during a high stand incorporates nine individual basins separated by sills (Figs. 1 and 2). A sill is defined as the lowest point on the divide between adjoining ba- sins. Not until its level reaches 1308 m above sea level does pluvial Lake Lahontan become a continuous body of water (Figs. 1 and 2; Table 1). During a pluvial-interpluvial cycle, the water level in each basin changes as a func- tion of three variables: the geometry of basin, the rate of water influx, and the evap- oration rate. There are four sources of water influx: stream flow, flow across interbasin sills, interbasin groundwater flow, and precipita- tion. Basins such as Winnemucca and Smoke Creek (Fig. 1) are not fed by streams that drain high mountain ranges. Lakes in these basins will form largely through over- flow from adjoining basins; however, lakes such as Pyramid and Walker will initially rise in response to increased inflow from perennial streams (Figs. 1 and 2). Lake level response to a change in the influx of water is conditioned by the geom- etry of the basin. The relative volume of a basin and the manner in which volume changes with elevation will determine the rate of change of lake level given a con- stant rate of evaporation. For example, Pyramid Lake will rise at a much greater rate than Carson Lake with a given equiv- alent input (Fig. 1). Given the constraints discussed above, it follows that for increasing precipitation: 1. Lakes in each of the nine basins will initially rise at different rates. 2. Upon reaching sill level, a lake will maintain a steady-state elevation until the adjoining basin fills to the same level; then both lakes will rise together. 3. Only for stages above the highest inter- nal sill depth (Adrian sill at 1308 m) will pluvial Lake Lahontan function as a single FLUCTUATIONS OF PLUVIAL LAKE LAHONTAN 303
WALKERLAKE CORESB-F SOME GEOCHEMICAL CONSIDERATIONS .I- 2- Broecker and Kaufman (1965) have pointed out that there are two fundamental .3- assumptions in computing a radiocarbon 4- age from a measured 14C/12C ratio: that the S- 14C/‘*C ratio of the sample at the time of formation can be accurately estimated and [ 6- that the present 14C/12C ratio has changed E .7- only through radioactive decay. B 3t .a- I Initial 14C112C I-6 .9- zij LO- I In freshwater lakes, the rate of carbon i5 I.,- exchange across the air-water interface may be insufficient to offset the introduction iu) 1.2- :: of dead carbon (14C-free carbon) into the &j 1.3- system (Deevey et al., 1954; Broecker and 4 Walton, 1959). Today in the Walker and I ’ 4- !i Pyramid basins, dead carbon is introduced x l.c.-- into the lakes by dissolution of carbonate 1.6- minerals within lake sediments, ground- water discharge across the sediment-water 1.7- interface, and groundwater discharge into IL.93 the streams which feed the lakes. Both 1.9- lakes receive significant carbon via the latter mechanism. The upward diffusive flux of carbon across the sediment-water interface has been noted in Walker and FIG. 3. Concentration of HCO; + CO!- expressed as Pyramid Lakes (Figs. 3 and 4), while trans- total C in interstitial fluids from five gravity cores taken port of carbon by direct groundwater dis- from Walker Lake. Cores C (half-open circle), D (open charge is of potential importance only in circle), and F (half-open square) were taken from the deepest area of lake (Fig. 7). Increasing concentrations the Pyramid basin (geothermal discharge). with depth suggest that a carbonate phase precipitated Broecker and Walton (1959) calculated the during a previous desiccation is now undergoing exchange rate for Great Basin lakes and dissolution. showed that the rate was not large enough to offset totally the present-day rate of body of water, responding in an integrated introduction of dead carbon. For example, manner to all fluid sources and sinks. a sample formed today in Pyramid Lake 4. Significant amounts of sediment will would yield a radiocarbon age of 410 years. accumulate only in river-fed basins but Broecker and Walton (1959) derived the not in others fed primarily by overhow following expression or interbasin groundwater flow. 5. Synchronously deposited carbonate CL R + lEkRCRICA k -= (1) materials such as algal tufa will not neces- CA R + lEkR + hV,IA, L’ sarily form at the same elevation within the nine-basin system except when the where basins are interconnected. CL/CA = concentration of 14C in lake 304 LARRY V. BENSON
HC03- divided by the concen- They calculated CJC, for high stands using tration of 14C in the atmosphere a range of estimates for the other param- R = exchange rate of carbon across eters. Values of CJC, ranged from 0.802 the air-water interface to 0.973, with the majority of estimates 1E = evaporation rate on the lake falling near the present-day value of 0.950. surface Therefore, Broecker and Walton applied a kR = concentration of total carbon 400-year correction to their dates based on entering the lake the 0.950 estimate of C JC,. k,, = concentration of total carbon in Data now exist which allow a better esti- the lake mation of CJC,. In particular, Broecker and h = decay constant of i4C (1.24 Walton (1959) assumed that V JAL (high standj x lo--4) = 3ViJ&,,,,,,. Detailed planimetering of CR/CA = concentration of 14C in river the Lahontan Basin (author’s unpublished water divided by the concentra- data) shows the actual relationship to be tion of i4C in the atmosphere VL/& (high stand) = 1.3 VL/&UW Broecker VL/AL = volume/area ratio of the lake. and Walton (1959) also assumed that the
PYRAMID LAKE CORES l-5 0 *
FIG. 4. Concentration of HCO; and CO;- expressed as total C in interstitial fluids from five gravity cores taken from Pyramid Lake. FLUCTUATIONS OF PLUVIAL LAKE LAHONTAN 305
TABLE 2 d3C = ( 13c/12c)&(13c/ 12C)L& (2) VALUES OF CL/C,* can be combined with the S13C expression CLCA Ratio p3c = 13c~12GalnLlle- 1 x 103 (3) R = 3 moles/ R = 9 moles/ 13c/12Gta”dard m*-year m2-year to yield an expression relating a13C to meas- C,IC, = 1.0 ured P3C kL = 15 0.962 0.985 kL = 10 0.975 0.990 1 + 613c,“,/103 kL= 5 0.987 0.995 a’3C = (4) 1 + ls3C&/103 CRICA = 0.9 kL = 15 0.943 0.978 Substituting ?P3C values for dissolved in- kL = 10 0.955 0.983 organic carbon and modern tufa (Broecker k,,= 5 0.968 0.987 and Walton, 1959)
a Values are calculated from Eq. (1). (W’BC = 1 + 6.5/103 = 1 .0125 1 - 5.91103 concentration of lake water carbon was the same in the past as today. However, meas- and assuming the l*C enrichment to be urements by both Russel (1885) and Jones twice the 13C enrichment (Craig, 1954), (1925) indicate that the concentration of (Yang= 1.0250 which is equivalent to a 2.5% total carbon (expressed as CO.& was 30% increase of 14C during tufa deposition. Thus smaller even in the recent past. a zero age tufa sample would date 200 years A new set of estimates for CJCA in Table in the future as a result of isotopic fraction- 2 is given. Broecker and Walton’s values ation. (1959) for the range of the exchange rate Since the errors introduced by dilution R and their estimate of the evaporation of lake water by dead carbon and preferen- rate 1, were used in the calculations. How- tial fractionation of l*C into tufa are oppo- ever, new values for the other parameters site in sign and of the same order, no radio- were obtained or estimated from more carbon corrections were made for tufas recent data. The results of the calculations deposited during high stands of Lake La- indicate that CJCA is particularly sensitive hontan (Table 3; Figs. 5 and 6). In addition, to the concentration of carbon in the lake since much of the dead carbon introduced during a high stand (kL) as well as the l*C into the lakes today may result from agri- concentration of river water (CR/C,>. Rea- cultural practices, no radiocarbon correc- sonable assumptions of decreased concen- tions were made for tufas deposited during trations of carbon in high-stand lake water the past 4000 years (Table 3; Fig. 6). If, and CR/CA values approaching unity due however, the present-day carbon cycle is to increased turbulence accompanying representative of prehistoric conditions, increased discharge lead to the suggestion 200 years should be subtracted from the that CJC, is on the order of 0.98 during ages of recent tufas. a high stand. Therefore, tufa deposited dur- ing a high stand will date only about 160 Isotopic Exchange years too old. It also appears (Table 3) that the heavier There are several ways by which the isotopes of carbon are preferentially incor- 14CP2C ratio of a calcium carbonate sample porated in tufa during its deposition. The can be altered. 13C fractionation factor 1. Surface exchange of carbon may 306 LARRY V. BENSON
TABLE 3
6-T VALUES~
Elevation Site Sample (ml Age (years B.P.) 8’T Wt.% (mg)
9 WL-IT” 1312 25,280 c 750 3.0 1.21 9 WL-2Tb 1324 12,340 + 160 - 1.49 9 WL-3Tb 1327 12,275 2 160 - 1.52 10 WL-4Tb 1211 2185 + 80 3.2 0.46 10 WL-ST* 1216 1335 2 75 2.6 0.60 10 WL-6Tb 1222 1720 -t 80 2.6 0.82 10 WL-7Tb 1229 1205 r 75 3.6 1.46 10 WL-8T 1236 cl85 2.9 1.01 10 WL-9T* 1244 4445 2 95 3.0 2.27 10 WL-MT* 1252 2970 r 85 3.1 2.68 10 WL-1lT 1253 >40,000 3.1 1.57 10 WL-12T 1292 >40,000 2.4 1.20 10 WL-13T 1299 >40,000 3.0 0.59 10 WL-14Tb 1318 12,240 r 160 2.7 1.46 10 WL-lST* 1327 11,850 -c 160 3.2 1.56 11 WL-16Bb 1332 11,075 2 160 - - 11 WL- 17Tb 1328 21,480 + 370 - 1.22
12 AD-2T” -1295 11,880 k 170 - 1.39 12 AD-3Tb -1302 12,275 f 175 - 1.66
1 PL3C 1254 18,910 + 340 2.0 0.60 1 PL-4c 1256 17,250 + 270 2.2 0.57 1 PL-SC 1257 17,810 + 280 - 0.42 1 PL-6T 1228 12,650 2 280 - 1.61 1 PL-7T 1229 16,515 f 310 - 1.21 1 PL-IT 1239 13,300 k 200 - 0.88 1 PL-9T 1249 13,300 T 200 - 0.98 1 PL-1OT 1262 13,580 + 200 - 0.95 1 PL-1lT 1276 10,370 2 145 - 1.15 1 PL-12T 1302 12,270 2 175 - 1.56 2 PL-13T 1203 22,090 + 450 3.3 1.07 2 PL- 14T 1209 >40,000 1.5 1.26 2 PL-15P 1230 15,140 + 250 2.7 0.76 2 PL- 16Tb 1238 21,370 2 420 3.0 0.80 2 PL-17T* 1260 18,580 f 310 2.3 0.48 2 PL-18Tb 1267 16,510 + 250 2.6 0.74 2 PL-19T 1277 12,390 k 180 3.2 1.37 2 PL-20T* 1311 13,550 k 195 3.3 1.15 2 PL-21Tb 1325 12,610 2 180 3.3 1.70 3 PL-22G 1260 19,620 k 360 -1.6 - 3 PL-23T” 1260 19,620 + 350 2.6 0.74 3 PL-24T 1260 12,460 + 175 - 1.63 4 PL-38T -1155 17,170 f 270 - 0.49 5 PL-40B 1170 875 + 74 - - 6 PL-41Tb -1311 13,430 2 195 3.0 1.23 6 PL-41Gb -1311 13,260 f 200 -0.8 - 6 PL-42T -1319 10,700 2 150 2.7 1.13 6 PL-43Tb -1328 11,430 f 160 2.5 I .29 3 PL-44AT 1260 17,100 * 340 - 0.71 3 PL-44BT* 1260 20,180 2 350 - 0.82 3 PL-44CT* 1260 19,910 c 350 - 0.64 3 PL-44DT* 1260 19,525 2 350 - 0.58 FLUCTUATIONS OF PLUVIAL LAKE LAHONTAN 307
TABLE 3 (Conrinued)
Elevation Site Sample Cm) Age (years B.P.)
Description
8c WIS-361 1160 2710 2 60 Wood debris 8 WIS-374 1168 8800 +- 90 Wood debris 8 WIS-375 1166 2690 -+ 65 Wood debris 8 WIS-377 1169 9720 r 100 Wood debris 8 WIS-363 1174 670 c 55 Wood debris 8 WIS-364 1173 1110 2 5.5 Wood debris 8 WIS-376 1174 2890 I 50 Wood debris 8 WIS-378 1172 2270 2 50 Wood debris 1162 1850 ? ? Collagen
n Exact locations are given in Fig. 7. b Indicates tufa samples plotted in Figures 5 and 6. c Dates on Site 8 materials and collagen from Born (1972). occur. Broecker and Orr (1958) demon- porous samples yielded radiocarbin ages strated experimentally that atmospheric 3-4% too young. contamination of dense tufa was trivial 2. Contamination by carbon-bearing but that atmospheric contamination of detritus or a secondary precipitate may
13207
1300-13207 1
I280 - I
, 1260- , I
1240 - / si I s 1220-I220
L c BLACKROCK SMOKE CREE” r 1200-1200 ! ,’
i
i;. WINNEMUCC,
,140 - LEGEND
VISUAL SIGHTING . 1120 - WOOD IN ANCESTRAL TRUCKEE ., DELTA (BORN. 1972) -I I I 00
DENSE STROMATOLITES ,LITHOIO~ . 1080 BEACH ROCK CEMENT tASfROPOOS PYR*t4ID LAKE BOTTOM 1060 1- I I I I I I ! I I I I I 0 2 6 .-a lb 12 14 16 18 20 22 2s 26
THOUSANDS OF YEARS BEFORE PRESENT FIG. 5. Elevation ofpluvial Lake Lahontan constructed from Pyramid Basin data. Size of sample is equivalent to lcr counting error. 308 LARRY V. BENSON
1200 - : LEGEND ,I Ilao- i VISUAL SIGHTING . : l’ DENSE STROMATOLITES (LITHOlD) . BEACH ROCK CEMENT 0 ,160L--.---m--, DENSE TUFA HEADS (ADRIAN PASS) 0
0 2 4 6 a 10 12 14 16 18 20 22 24 26 THOUSANDS OF YEARS BEFORE PRESENT FIG. 6. Elevation of pluvial Lake Lahontan constructed from Walker Basin data. Size of sample is equivalent to lu counting error.
occur. Porous tufa deposited at relatively SAMPLING METHODS low elevations may trap detrital particles (e.g., gastropod fragments) and/or act as a The most frequently sampled carbonates nucleation site for secondary precipitated were deposits of algal tufa. Tufa deposits carbonates during a subsequent high stand. vary from l-mm-thick coatings to 30-m-high Carbon dioxide-saturated rain can dissolve pinnacles composed of interlocking sphe- CaCO,. Reprecipitation of CaCO, can roids 2 to 3 m in diameter (for a more de- then be caused by evaporative concentra- tailed review of the origin and habit of tufa tion and/or the elevated temperature accom- see Russell, 1885; Jones, 1925; Radbruch, panying the evaporative process. A sample 1957; and Scholl, 1960. contaminated in either of these ways would Calcium carbonate samples used in this yield a date younger than the actual date. study can be grouped into seven macro- 3. Tufa composed of a metastable phase scopic classes: or containing a metastable contaminant 1. Thin (lo-50 mm), dense, sometimes may recrystallize at a later date. This may distinctly laminated stromatolitic tufa com- be the case for the thinolite form described monly termed “lithoid.” below (Broecker and Kaufman, 1%5). 2. Large (50-200 cm) porous reef-like 4. A single sample may actually repre- tufa, occurring in a variety of growth forms sent a series of growth stages. This is most (dendritic, mammillary). certainly the case for the thick reef-like 3. Califlower-like heads composed of tufa deposits and may hold true even for long prismatic crystals (thinolite tufa) at the relatively thin (I-50 mm) dense lithoid the base which grade upward into a porous variety. mammillary habit. FLUCTUATIONS OF PLU [VIAL LAKE LAHONTAN 309
4. Five to ten centimeter thick coatings of radiocarbon dates. A collection of sam- on volcanic talus. These coatings are char- ples from relatively thick porous tufas was acterized by the presence of continuous made along a vertical traverse at Site 1. vertical pores. Calcium carbonate-cemented sand (beach- 5. Calcite-cemented sand and gravel- rock) was collected at Sites 5 and 11, and size fragments of reworked talus. Morpho- one sample of thinolite-rooted material was logically, the combined material looks taken from Site 4. like beachrock or concrete. 6. A 7-m-thick layer of marl composed ANALYTICAL METHODS primarily of the alga Chara. 7. Gastropods which lived within shel- X-ray determinations were made on all tered areas formed by lithoid-cemented samples, and the presence of monohydro- boulders. calcite, aragonite, high-Mg calcite, and The locations of gravity cores and of low-Mg calcite was determined. Analyses samples collected for this study are shown for Mg were done by atomic absorption in Fig. 7. At Sites 2 and 10, thin coatings spectrophotometry after dissolution of the of lithoid material were collected along solid. Two or more portions of each solid vertical traverses. A SO-mm-thick sample sample were separately analyzed, and the of lithoid tufa composed of four macro- data were averaged. Radiocarbon determina- scopic layers was collected at Site 3. Lith- tions were made by Teledyne isotopes under oid samples deposited during former high the supervision of J. Buckley. Prior to stands of Lake Lahontan were collected analysis, the samples were acid-leached to at Sites 2, 3, 6, 9, 10, and 11. At Sites 3 remove surficial contaminants. The weight and 6, multiple types of coexisting carbo- percentage removed during the leaching nate materials (tufa and gastropods) were process was: tufa, 46-59%; gastropods, collected to test for internal consistency 10%; and beachrock, O-15%. The I’O-
FIG. 7. Sample location map. Solid dots represent tufa, gastropod, and beachrock collecting sites. Open circles are gravity core sites. 310 LARRY V. BENSON
FIG. 8. Gastropod fragments infilling primary porosity. Note dark micritic cement. Width of picture is about 1 cm.
corrected 813 C measurements were made dissolution to infilling with secondary pre- at Brown University on a V.G. Micromass cipitates and detritus. 602C. Lithoid samples. The majority of hthoid samples (WL-IT-5T, WL-IlT, WL-13T, RESULTS WL-17T; PL-ST-18T, PL-20T, PL-21T, PL-23T, PL-41T, PL-43T, PL-44T) have Petrography experienced dissolution; however, certain samples (WL-6T- lOT, WL-14T, and All varieties of tufa have suffered some WL-15T) also evidence minor infilling of degree of diagenetic alteration ranging from secondary porosity by elastic debris and FLUCTUATIONS OF PLUVIAL LAKE LAHONTAN 311 micritic material. A few samples (WL-12T; the samples (PL-6T, PL-7T, and PL-llT), PL-14T, and PL-42T) contain limited acicular carbonate was precipitated prior amounts of acicular or blocky carbonate to detrital infilling (Fig. 9). cement. Thinolite-rooted head. The base of this Reef-like samples. All the massive tufas sample (PL-38T) is composed of prismatic (PL-6T-13T, PL-19T, and PL-24T) con- crystals which were “rooted” in the former tain significant amounts of secondary poros- lake bed. The head is stromatolitic and ity. Both primary and secondary pores are has a large amount of primary and second- filled to various degrees with detritus, e.g., ary porosity filled with sedimentary debris gastropod fragments (Fig. 8). In three of and acicular cement.
FIG. 9. Dark brown acicular precipitate coating primary void. Width of picture is about 1 cm. 312 LARRY V. BENSON
Thick coatings. Samples AD-2T and The outermost layer (PL-44DT) yielded a AD-3T appear to be precursors of reef- date (19,525 r 350 B.P.) nearly identical like tufa; however, these specimens con- with the gastropods affixed to it (19,620 tain only small amounts of debris, primarily + 360 B.P.). The outer three layers (PL- volcanic. 44BT, PL-44CT, and PL-44DT) have ages Petrographic observations indicate that consistent with the deposition of a single the uncontaminated lithoid samples and sample during one and not three separate the thick coatings from Adrian Pass should high stands; however, the innermost layer give reliable radiocarbon ages. The other (PL-44AT) appears to have been contam- tufas contain significant amounts of second- inated by younger material. ary carbon-bearing material which could The ages and elevations of those samples cause the true age to be underestimated. which are thought to be the most reliable estimators of the time of sample deposi- X-Ray Diffraction tion are plotted in Figs. 5 and 6. The radio- carbon ages of the Chara samples (PL-3C- Gastropod samples (PL-22G, PL-41G) SC) are not stratigraphically consistent, are totally aragonite. The great majority probably as a result of sediment reworking. of tufa samples are low-Mg calcite; how- The ages and elevations of these samples ever, WL-7T, WL-8T, and WL-9T have and the contaminated massive reef-like traces of monohydrocalcite, and WL-9T tufas have therefore not been plotted in and WL-10T have traces of high-Mg calcite. Figs. 5 and 6. The X-ray data indicate that the gastro- Also plotted in Fig. 5 and listed in Table 3 pods should yield valid radiocarbon ages. are the radiocarbon ages of wood samples Although WL-7T, WL-8T, and WL-9T taken from deltaic sediments (Born, 1972) contain small amounts of secondary mate- (see Fig. 7 for locations). rial, the contaminant was introduced at The data of Figs. 5 and 6 document the the same time the tufa was deposited. There- internal consistency of radiocarbon ages of fore, these samples are also assumed to coexisting materials and in addition show give accurate radiocarbon age estimates. that lithoid tufas which formed in different The micritic and acicular precipitates regions at approximately the same elevation common to the more massive tufas were yield essentially the same radiocarbon age. probably initially either aragonite or For example, four lithoid samples (WL-2T, high-Mg calcite (Friedman, 1968). Failure WL-3T, WL-14T, and PL-21T) from the to detect either of these phases suggests interval 1318 to 1327 range in age from the possibility of recrystallization sub- 12,240 f 160 to 12,610 r 180 years. sequent to deposition. This process would of course alter the apparent radiocarbon age. DISCUSSION Radiocarbon Ages Absolute Chronology: Pyramid and Walker Basins Radiocarbon ages range between the limits of precision, i.e., from <185 to Figures 5 and 6 and the data of Table 3 >40,000 years (Table 3). Coexisting gastro- suggest an absolute chronology for Lake pod and lithoid samples at Sites 3 (PL-22G Lahontan fluctuations. At least one high and PL-23T) and 6 (PL41G and PL-41T) stand occurred before 40,000 B.P. No yield dates which are internally consistent. evidence was found of any high stands Because PL-23T was macroscopically during the period 40,000 to 25,000 B.P., layered, an additional sample from the which suggests the possibility of an inter- same site (PL-44T) was collected, and each pluvial during this time. Within the last of its four layers was separated and dated. 25,000 years there were two high stands FLUCTUATIONS OF PLUVIAL LAKE LAHONTAN 313
0 8OO .I--1 88 .2- 8 8 .3- l 8 00 .4 - m cl
WALKER LAKE CORES # .5 m w .6- ,3 SEDIMENT-WATER INTERFACE CORE B f l m c-0 l uz .7- 0 CORE C 0 CORE D r l % .6- l CORE E 8 CORE F 2 n 8 g .9- E l l 0 0 bj l.O- m 0 4 I.)- : l 3 1.2- If 8 m g 1.3- z l I 1.4- t 1 x l.5- m 1.6- 8 8 1.7- 8 8 l.6-
l.9-
2.0 I I Id00 do0 3dO0 40001 do0 6000 7000 Sob0 MG/L CI- FIG. 10. Chloride-depth profiles for interstitial fluids from Walker Lake cores. Note that concentration of Cl- in deep water, Cores C, D, and F, increases with depth. This indicates presence of one or more chloride salts precipitated during prior desiccation that are now undergoing dissolution.
which joined all nine basins, the first 25,000 fluids extracted from five gravity cores. to 21,500 B.P. and the second 13,600 to Cores C, D, and F, which were taken from 11,000 B.P. Throughout much of the inter- the deepest portion of the lake basin (Fig. 7), vening.period, i.e., 21,000 to 15,000 B.P., show increasing concentrations of Cl- with Lake Lahontan stood at about 1265 m, depth below the sediment-water inter- indicating that all basins except Walker face. This is interpreted to indicate that were joined. Shortly before 11,000 B.P., Walker Lake became dry or nearly dry in water levels declined rapidly in both basins the past, causing the precipitation of chlo- resulting in a low stand during the period ride salts in the deepest portion of the basin. 9000 to 5000 B .P. During this period, Walker These salts were covered first by wind- Lake desiccated. Figure 10 shows the chlo- borne sediments and later by sediments ride composition of Walker Lake pore carried by the Walker River. As the lake 314 LARRY V. BENSON basin began to fill again, soluble salts such a 4.5-m core taken near Core F (Fig. 7), as NaCl and KC1 began to dissolve, causing indicate that saturation with halite should an upward migration of dissolved solids to occur at a depth of 10.5 m. This corre- the overlying lake water. Benson and Leach sponds to a sediment age in the range of (1977) have shown that 85% of the total 9050 to 6400 B.P. This provides an approx- mass of Cl- presently in Walker Lake is due imate estimate of the time that Walker Lake to this source located below the sediment- desiccated and is in accord with the tufa water interface. Radiocarbon dates on bulk data (Fig. 6). The lack of evidence of a materials from Cores B and D indicate brine at depth in Pyramid Lake sediments sedimentation rates ranging from 800 to (Fig. 11) suggests that Pyramid Lake re- 1050 years/m. Fore fluid data from Core G, mained in existence, although it may have
a 8 00 0 .I- .2- cm 0 8 0 .3- .4- Y oc 0 2 .5- E I- .6- z l 0800 5 .7- 5( .6- !z g .9- E ii l.O- I l a& m s I,,- !+ u) 1.2- PYRAMID LAKE CLwlES 6 l 0 00 H g 1.3- A SEDIMENT-WATER INTERFACE l CORE I 0 z 1.4- CORE 2 l 0 0 0 CORE 3 E 8 CORE 4 % 1.5- 0 CORE 5 0 1.6-
I.?- l 0 l.6- 0
1.9-
20 ' n I 1400 1500 Id00 100 ;p”B' l&O 2cbo coo 2 10 MG/L FIG. 11. Chloride-depth profiles for interstitial fluids from Pyramid Lake cores. Note concentration is a decreasing function of depth. This indicates that chloride salts do not exist within deeper sediments and suggests that Pyramid Lake did not go dry when Walker Lake desiccated. The vertical increase in concentration is attributed to the increased concentration of overlying lake waters since 1910. FLUCTUATIONS OF PLUVIAL LAKE LAHONTAN 315 been severely restricted in size. It should However, the data of Broecker and Kauf- be noted, however, that both Mg2+ and Caz+ man, which support and even earlier high parallel the increasing carbon concentra- stand around 9500 B.P., are clearly in con- tion with depth in cores from the center of flict with the data of Born (1972). Pyramid Lake (Figs. 4 and 7). This suggests 3. Broecker and Kaufman did not find that a magnesium-bearing carbonate phase any evidence of a prior high stand compar- was precipitated in the past when the lake able in elevation to the 12,000 B.P. high water was more concentrated. stand. Data of this study indicate that a The radiocarbon chronology discussed former high stand connecting all nine basins above differs from Broecker and Kaufman’s occured 25,000 to 21,500 years ago; how- (1965) chronology in several ways: ever, more data are needed to fuIIy substan- 1. A more detailed picture is now avail- tiate this finding. able for the period 5000 to 0 B.P. Apparently, both Walker and Pyramid Lakes were rising Comparison of Lahontan Lake-Level until agricultural practices commencing Chronology with Searles Lake-Level around the turn of the century caused their Chronology unnatural recession. 2. Broecker and Kaufman interpreted During pluvial periods of the Pleistocene, their data to indcate two high stands at Searles Lake in southeast California was 12,000 and 9500 B.P.; however, the data third in a chain of lakes which received of this study indicate a single high stand the majority of their water from the Sierra 13,600 to 11,100 B.P. It is quite possible Nevada. In a series of publications, Smith that significant changes in lake level result- (1962, 1968, and 1970) has detailed the sub- ing in more than one high stand occurred surface stratigraphy of the lake. Radiocar- during the interval 13,600 to 11,100 B.P. bon dating of the stratigraphic section has
El270
: 5260
I I I I I I I I 6 6 IO I2 I4 I6 I6 20 22 ; THOUSANDS OF YEARS BEFORE PRESENT FIG. 12. Age-elevation plot for all dated tufas from Pyramid Lake area. Note that thick tufas (dendritic) that exhibit infilling consistently yield low lake level estimates. See text for discussion. 316 LARRY V. BENSON revealed a record of lake level fluctuations and between the two basins investigated. largely in agreement with the data presented If, however, age-elevation data for thick in this paper (for example, compare Fig. 2 reef-like tufas (dendritic) is incorporated, of Smith (1968) with Figs. 5 and 6 of this the chronology becomes inconsistent. Fig- paper). The interval 10,500 to 24,000 B.P. ure 12 is an age-elevation plot for all types was characterized by a series of expansions of dated tufa found in the Pyramid Basin. and recessions terminated by a final desicca- The dashed rectangle in Fig. 12 outlines tion of about 10,000 B.P. From 10,000 to the area of inconsistency. The well-pre- 6000 B.P. the lake was nearly dry, as served lithoid tufa and gastropod data indi- evidenced by the deposition of soluble salts. cate that lake level ranged from 1310 to These data suggest that both lake systems 1330 m during the period 13,600 to 11,100 fluctuated synchronously. B.P. However, data from thick tufas sug- gest that algae flourished at depths of up Climatic Implications to 100 m during the same period. This is not reasonable, since algal growth is a func- The shape of the Lahontan lake level tion of available sunlight. In addition, on- curve from Pyramid Basin (Fig. 5) indicates going limnological studies of Pyramid Lake that major changes in climatic parameters by W. F. Sigler have shown that periphyton occurred during two periods: 15,000 to range in depth from 1 to 12 m, with optimum 13,500 B.P. and 12,000 to 10,000 B.P. Dur- growth at 3 m. Therefore, it is concluded ing the first period, Lake Lahontan rose that thick tufas, which invariably contain approximately 100 m. This represents a secondary material, yield radiocarbon dates 6-fold increase in volume (from 356 to 2,130 that are too young and should not be used km3) and a 2.3-fold increase in surface area in studies of lake level fluctuations. (from 9700 to 22,300 km2). Between 11,000 and 10,000 years ago the lake fell 150 m to an elevation approximately equivalent to CONCLUSIONS the 1880 A.D. value of 1180 m in Pyramid 1. Only dense forms of tufa and arago- Basin. If the lakes in the Walker, Pyramid, nite gastropods yield reliable radiocarbon and Winnemucca Basins 10,000 years ago ages of lake levels in the Lahontan Basin. are also assumed to have been at elevations 2. An internally consistent absolute chro- corresponding to their 1880 A.D. levels, then a calculation shows that the volume nology of pluvial Lake Lahontan fluctua- occupied by lakes in the Lahontan Basin tions for the past 40,000 years has been decreased from 2130 to 55 km3, and the pieced together from radiocarbon dates on surface area of the lakes decreased from various materials from Pyramid and Walker Basins. An interpluvial period possibly 22,300 to 1100 km2 within less than 2000 occurred from 40,000 to 25,000 years B.P. years. This was followed by a piuviai period which The rapid changes in lake level and sur- lasted until 11,100 B.P. This pluvial pe- face area which occurred before and after riod began and ended with high stands of the last 1330-m high stand imply significant changes in the rate of fluid input (stream greater than 1300 m, which spanned the intervals 25,000 to 21,500 and 13,600 to flow, groundwater discharge, and precipita- 11,100 B.P. tion directly onto the lake) and/or changes in the rate of fluid loss (evaporation rate). Warm arid conditions prevailed from 9000 to 5000 B.P. During this time probably all lakes except Pyramid desiccated. Radiocarbon Reliability of Tufa During the last 5000 years, both Pyramid The lake level chronology presented and Walker Lakes have increased in size. in this paper is internally consistent within Unfortunately, the onset of irrigation in FLUCTUATIONS OF PLUVIAL LAKE LAHONTAN 317 the late 1800s affected the last 100 years Deevey, E. S., Gross, M. S., Hutchinson, G. E., of the lake level record. and Kraybill, H. L. (1954). The natural C? contents 3. Sufficient data exist in the Pyramid of materials from hard-water lakes. Proceedings National Academy of Science Washington 40, Basin to suggest that radical changes in 285-288. climate occurred before and after the last Ekren, E. B., Rogers, C. L., Anderson, R. E., and 1330-m high stand. Orkild, P. P. (1968). Age of basin and range normal faults in Nevada Test Site and Nellis Air Force Range Nevada, in Eckel, E. B., ed., Nevada Test ACKNOWLEDGMENTS Site: Geological Society of America Memoir 110, 247-250. The author thanks R. Byrne. C. Wahrhaftig, W. S. Broecker, G. I. Smith, J. Apps, and R. K. Matthews Emiliani, C. (1966). Paleotemperature analysis of Caribbean cores P6304-8 and P6304-9 and a gen- for their helpful criticisms. Special thanks are due to M. Mifflin and M. Wheat who guided the author to eralized temperature curve for the past 425,000 various excellent sample localities. J. Hainline was years. Journal of Geology 74, 109- 126. responsible for much of the sample collection; P. Friedman, G. M. (1%8). The fabric of carbonate Harris supervised the chemical analyses: and R. cement and matrix and its dependence on the Fifer performed the X-ray and stable isotope analysis. salinity of water. In Recent Developments in Car- This research was supported primarily by Oflice bonate Sedimentology in Central Europe (Miiller, of Water Research and Technology Grant No. 14-31- German, and Friedman, Eds.), pp. 11-20. Springer- Oool-5236 and U. S. Energy Research and Development Verlag, New York. Frye, J. C., Willman, H. B., and Black, R. F. (1965). Administration Grant No. AT (29-2)1253. A portion of this work was done while the author was a prin- Outline of glacial geology of Illinois and Wisconsin. In “The Quatemary of the United States” (Wright cipal investigator at the Desert Research Institute, Reno, Nevada. and a visiting geologist at the Univer- and Frey, Eds.), pp. 43-61. Princeton University sity of California, Berkeley. Press, Princeton, N. J. lmbrie, J., and Kipp, N. G. (1971). New method for quantitative paleoclimatology. In “The Late REFERENCES Cenozoic Glacial Ages” (K. K. Turkekian, Ed.), pp. 71-181. Yale University Press, New Haven, Bateman, P. C., and Wahrhaftig, C. (1966). Geology Conn. of the Sierra Nevada. California Bureau of Mines Jones, J. C. (1925). The geologic history of Lake and Geology Bulletin 190, 107- 169. Lahontan. Carnegie Institute of Washington Pub- Benson, L. V., and Leach, D. (1977). Hydrochemistry lication No. 325, pp. 3-50. of uranium in the Walker Basin, Nevada and Cali- Kukla, J. (1970). Correlation between loesses and fornia, in preparation. deep-sea sediments. Geol. Fiiren. Stockholm Born, S. M. (1972). “Lake Quaternary History, Ftirk 92, 148- 180. Deltaic Sedimentation, and Mudlump Formation Mehringer, P. J., Jr. 1977. Great Basin late Quaternary at Pyramid Lake, Nevada.” Published by Center environments and chronology. In “Models and for Water Resources, Desert Research Institute, Great Basin Prehistory” (D. D. Fowler, Ed., pp. Reno, Nevada, 97 pp. 113- 167. Desert Research Institute Publications in Broecker,‘ W. S., and Kaufman, A. (1965). Radio- Social Science No. 12, Univ. of Nevada, Reno. carbon chronology of Lake Lahontan and Lake Morrison, R. B. (1965). Radiocarbon chronologies Bonneville II, Great Basin. Geological Society of Lakes Lahontan and Bonneville: A stratigraphic of America Bulletin 76, 537-566. evaluation. In International Association for Quater- Broecker, W. S., and On-, P. C. (1958). Radiocarbon nary Research, VII International Congress, p. 347. chronology of Lake Lahontan and Lake Bonne- Morrison, R. B., and Frye, J. C. (1965). Correlation ville. Geological Society of America Bulletin 69, of the Middle and Late Quatemary successions 1009- 1032. of the Lake Lahontan, Lake Bonneville, Rocky Broecker, W. S., and Walton, A. (1959). The geo- Mountain (Wasatch Range), Southern Great Plains, chemistry of CL4 in freshwater systems. Geochimica and Eastern Midwest Areas. Report 9 of the Nevada et Cosmochimica Acta 16, 15-38. Bureau of Mines, 45 pp. Broecker, W. S., and Van Donk, J. (1970). Insolation Radbruch, D. H. (1957). Hypothesis regarding the changes, ice volumes and the 0’s record in deep- origin of thinolite tufa at Pyramid Lake, Nevada. sea cores. Reviews of Geophysics and Space Phys- Geological Society of America Bulletin 68, 1683- ics 8, 169-198. 1688. Craig, H. (1954). Carbon 13 in plants and the relation- Russell, I. C. (1885). Geological history of Lake ships between carbon 13 and carbon 14 variations Lahontan. United States Geological Survey Mono- in nature. Journal of Geology 62, I15- 149. graph 11, 288. 318 LARRY V. BENSON
Scholl. D. W. (1960). Pleistocene algal pinnacles at climatic history of Searles Lake, southeastern Searles Lake, California. Jolrvnal of Sedimentary California. 8th Internat. Quaternary Congress., Pefrology 30, 414-43 I. Proc. 7. pp. 293-310. Shackleton. N. J., and Opdyke. N. D. (1973). Oxygen Smith. G. I. (1970). Late Wisconsin lake fluctuations isotope and paleomagnetic stratigraphy of equa- in Searles Valley, California: American Quaternary torial Pacific core V28-238: Oxygen isotope temper- Assoc. Meeting. Aug. 28-Sep. I. Yellowstone atures and ice volumes on a IO” year and IO” year Park and Montana State Univ.: AMQUA Abstr., time scale. Quuternary Research 3, 39-55. p. 124. Smith. G. I. (1962). Subsurface stratigraphy of late Wahrhaftig, C.. and Birman. J. H. (1965). The Quater- Quaternary deposits, Searles Lake, California: A nary of the Pacific Mountain system in California. summary. United States Geological Survey Prof. In “The Quaternary of the United States” (Wright Paper 450-C. pp. C65-C69. and Frey, Eds.). pp. 299-339. Princeton Univer- Smith, G. I. (1962). Late-Quatemary geologic and sity Press. Princeton, N. J.
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