Core KM-Sj a Surf ace-to-Bedrock Record of Late Cenozoic Sedimentation in Searles Valley, California GEOLOGICAL SURVEY PROFESSIONAL PAPER 1256 Core KM-3, a Surf ace- to-Bedrock Record of Late Cenozoic Sedimentation in Searles Valley, California By GEORGE I. SMITH, VIRGIL J. BARCZAK, GAIL F. MOULTON, and JOSEPH C. LIDDICOAT GEOLOGICAL SURVEY PROFESSIONAL PAPER 1256 The basin sedimentation history of Searles (dry) Lake from Miocene or early Pliocene time to the present UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1983 UNITED STATES DEPARTMENT OF THE INTERIOR JAMES G. WATT, Secretary GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Core KM-3, a surface-to-bedrock record of late Cenozoic sedimentation in Searles Valley, California. (Geological Survey professional paper 1256) Bibliography Supt. of Docs, no.: I 19.16:1256 1. Rocks, sedimentary. 2. Geology, stratigraphic Cenozoic. 3. Geology California Searles Valley. 4. Borings California Searles Valley. I. Smith, George Irving, 1927- II. Title. III. Series: United States. Geological Survey. Professional Paper 1256. QE471.C73 1982 551.T8'0979495 82-600347 For sale by the Distribution Branch, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 CONTENTS Page Page Abstract................................................................................................ 1 History of sedimentation Continued Introduction ........................................................................................ 1 From Miocene or early Pliocene time to 3.18 m.y. B.P. History of coring in Searles Valley .............................................. 3 alluvial sand and gravel ................................................16 Methods of study ................................................................................ 3 3.18-2.56 m.y. B.P. Unit I, Mixed Layer..........................16 Lithology ...................................................................................... 3 2.56-1.94 m.y. B.P. Unit H ..................................................16 Chemistry .................................................................................... 7 1.94-1.27 m.y. B.P. Unit G ...............-................ ..........16 Mineralogy .................................................................................. 9 1.27-1.00 m.y. B.P.-Unit F ..................................................17 Dating ..........................................................................................10 1.00-0.57 m.y. B.P. Unit D+E ............................................17 Acknowledgments ....................................................................11 0.57-0.31 m.y. B.P. Unit C ..................................................17 Stratigraphy ........................................................................................ 11 0.31-0.13 m.y. B.P. Units A and B ....................................17 Summary ...................................................................................... 11 Rates of sedimentation ....................................................................18 Description of units of the Mixed Layer.............. ................ 12 Trends in sedimentation and their significance........................18 Unit A ..................................................................................12 Change from alluvial to lacustrine sediment ....................18 Increases in the percentage of chemical sediment ..........18 Changes in composition of the lake water ..........................18 Unit D+E .............................................................................. 14 Changes in carbonate minerals in mud layers ..................19 Paleoclimatic interpretation ..........................................................20 History of Searles Lake... ..................................................20 UnitH ..................................................................................14 History of Owens River flow, as indicated by the size of Unit I ....................................................................................15 Searles Lake ...................................................................21 Alluvial sand and gravel............. ...................................... .......15 Relation between Searles Lake sizes and Sierra Nevada Bedrock ........................................................................................15 glacial stages ....... ... ................................................22 History of sedimentation. ................................................................. 15 Nature of the climate 3-1 m.y. B.P ......................................23 References cited ................................................................................23 ILLUSTRATIONS [Plates are in pocket] PLATE 1. Graphic log of core KM-3, showing lithologies, stratigraphic-unit boundaries, magnetic stratigraphy, and hues of mud units 2. Stratigraphic variations in percentages of five acid-soluble components and the acid-insoluble residue in core KM-3 3. Stratigraphic variations in normative weight percentages of acid-soluble minerals commonly concentrated in saline layers of core KM-3 4. Stratigraphic variations in normative weight percentages of acid-soluble minerals and acid-insoluble residue commonly concentrated in mud layers of core KM-3 Page FIGURE 1. Map showing positions of late Pleistocene and present-day lakes in chain that included Searles Lake.................................. 2 2. Map of Searles (dry) Lake, showing location of corehole KM-3, locations of cross section A-A' and coreholes plotted in figure 5, and approximate limits of dry lake.................................................................................................................................... 4 3. Plots of chemical analyses of samples from core KM-3 for borate, lithium, potassium, and bromine.................................... 8 4. Plots of arc-emission spectrographic analyses of samples from core KM-3 for manganese, molybdenum, titanium, and vanadium ...... - . .. ....... .... ................ ...........-. .................... ...... 9 5. Diagram of east-west section through 11 cores, showing Stratigraphic relations between Bottom Mud and Units A and B of Mixed Layer, and lateral variations of subunits within Unit A ........................................................................................13 6. Graph showing reconstructed history of Searles Lake, based primarily on evidence from core KM-3..................................21 TABLES Page TABLE 1. Summary of Stratigraphic units in core KM-3........................................--.-..-........---. -- -- -------- 3 2. Generalized log of core KM-3 -. - . - .. ............. - ... ..... ... -...-.-. - -- - - ----- 5 3. Sedimentation rates between paleomagnetically dated horizons in core KM-3 18 in CORE KM-3, A SURFACE-TO-BEDROCK RECORD OF LATE CENOZOIC SEDIMENTATION IN SEARLES VALLEY, CALIFORNIA By GEORGE I. SMITH, VIRGIL J. BARCZAK1, GAIL F. MOULTON2, and JOSEPH C. LIDDICOAT3 ABSTRACT The most extreme change in sedimentation in Searles Valley was the shift from alluvial to lacustrine deposition 3.18 m.y. B.P., A 930-m core designated KM-3, recovered from an area near possibly as a result of volcanic damming of a river channel across the the center of Searles Lake in Searles Valley, Calif., records a history Sierra Nevada that had previously allowed part of the Great Basin to of nearly continuous sedimentation from Miocene or early Pliocene drain externally. Subsequent changes in the mineralogy and amount time to the present. The earliest sedimentary deposits, 220 m of of chemical sediment in the lacustrine deposits indicate marked reddish-brown alluvial gravel, rest on 15+ m of quartz monzonite fluctuations in lake level superimposed on a gradual increase in the bedrock. Lacustrine sedimentation in ancestral Searles Lake started salinity of the deeper lakes and a progressive change in the chemis­ 3.18 million years ago (m.y. B.P.) and left 693 m of various types of try of their waters. Upon concentration or desiccation, the composi­ lake deposits that make up the rest of the fill in that part of the valley tion of the saline deposits changed accordingly. where the core was recovered. Paleoclimatic reconstructions indicate a decrease over time in The lacustrine sediment is here divided into 14 informal strati- the amount of runoff that fed the lake, partly owing to continuing graphic units, three of which are new, on the basis of field logs, uplift of the Sierra Nevada that created an enlarging rain shadow, chemical and mineralogic data, and study of the preserved core and although climatically induced variations in runoff caused fluctua­ color photographs taken when the core was fresh. Quantitative tions in inflow that exceeded this more gradual change. Correlation reconstruction of the evaporite mineralogy, based on 254 analyses of of the perennial lake deposits in Searles Valley with the Sherwin Till the acid-soluble components and X-ray diffraction data, allows the and the McGee Till of the Sierra Nevada a reasonable relation details of chemical sedimentation to be documented. Ages of critical because of the inferred hydrologic connection between these areas contacts are estimated from 14C data (younger sediment), paleomag- suggests that the Sherwin Glaciation began 1.28 m.y. B.P., waned netically established horizons (older sediment), and interpolation 1.00 m.y. B.P., but did