U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY THE LAST INTERGLACIATION AT OWENS LAKE, CALIFORNIA: CORE OL-92 Edited by James L. Bischoff1 Open-File Report 98-132 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards (or with the North American Stratigraphic Code). Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government ! U.S. Geological Survey, Menlo Park, CA 94025 1998 THE LAST INTERGLACIATION AT OWENS LAKE, CALIFORNIA U.S. Geological Survey Open File Report 98-132 Table of Contents Pages 1. Introduction and rationale of study (J.L. Bischoff) 1-5 2. Sedimentary features in core OL-92,0.9-82.5 m depth, Owens Lake, California 6-34 (J. P. Smoot) 3. A high-resolution study of sediments from the last interglaciation at Owens Lake, 35-65 California: Geochemistry of sediments in core OL-92, 83-32 m depth (J.L. Bischoff, D. Chazan, and R.W. Canavan, IV) 4. Climatic and hydrologic conditions in Owens Basin California between 45 and 145 ka 66-81 as reconstructed from the high-resolution stable isotope records. (H.-C. Li, T.-L. Ku, J.L. Bischoff, and L.D. Stott) 5. Carbonate mineralogy in Owens Lake, California from 45-145 ka: a proxy for lake 82-98 hydrology and productivity (H.-C. Li, T.-L. Ku, and J.L. Bischoff) 6. Sediment magnetic data (83-18 m depth) and XRF geochemical data (83-32 m depth) 99-119 from lacustrine sediment in core OL-92 from Owens Lake, California (R.L. Reynolds, J.G. Rosenbaum, N. Mazza, W. Rivers, and F. Luiszer) 7. Diatom count data and Owens Lake paleolimnology during the last interglacial (J.P. 120-14 Bradbury and M. Paquette) 8. Ostracodes from Owens Lake core OL-92 and the paleoenvironment of the last 142-15 interglacial (R.M. Forester and C. Carter) 9. Testing climate stability during the last interglacial interval: pollen evidence from 156-17 Core OL-92 (R.J. Litwin) 10. Thermoluminescence and optical dating of fine-silt-size feldspars from mud from 171-17 Owens Lake, California Core OL-92 (G.W. Berger) 11. A test of uranium-series dating of ostracode shells from the last interglaciation at 180-18 Owens Lake, California, core OL-92 (J.L. Bischoff, T.D. Bullen, R.W. Canavan IV, and R.M. Forester) INTRODUCTION AND RATIONALE OF STUDY James L. Bischoff Owens Lake, located at the eastern base of the central Sierra Nevada (Fig. 1), was the terminus of the Owens River prior to the lake's complete desiccation shortly after 1913 due to river diversion by the City of Los Angeles. During earlier wetter cycles, the lake overflowed to fill a series of downstream basins including China Lake Basin, Searles Valley, Panamint Valley, and ultimately, Death Valley (Smith and Street-Perrott, 1983). In 1992 the U.S. Geological Survey drilled a 323-m-deep core (OL-92) into Owens Lake sediments near the depocenter of the basin to obtain a continuous record of silty-clay sediment spanning the last 800,000 yrs. A multi-parameter reconnaissance study of the entire core (ca 7000-yr resolution), was reported in a 13-chapter summary volume (Smith and Bischoff, 1997). A document containing the numerical and other detailed forms of raw data collected by that volume's authors was prepared earlier (Smith and Bischoff, 1993). The reconnaissance study provided an approximate time-depth model for the entire core, based on radiocarbon dates from the top 31m, the Bishop Ash (759,000 yrs) at 304 m, ten within-Brunhes paleomagnetic excursions, and a compaction-corrected mass-accumulation rate of 51.4 g/cm/lOOOyr (Bischoff et al., 1997a). Application of this model to observed sediment parameters indicates that Owens Lake was saline, alkaline, and biologically productive at times of decreased water-flow, and was generally hydrologically flushed and relatively unproductive during times of increased water-flow. Grain size, abundance of CaCOs, organic carbon, clay mineralogy, cation-exchange capacity of the clay fraction, fossil pollen, fish, ostracodes, and diatoms (see summary by Smith et al., 1997) all show cyclic variation down the core. CaCOs abundance, in particular, strongly reflects an approximately 100 ka dominant cycle, characteristic of global ice-volume indicated by the MIS 818O record. Four of the last five marine isotope terminations are clearly shown in the OL-92 record. An intermediate resolution (1500 yr) study was later undertaken and the results are reported by Menking et al (1997) and Bischoff et al (1997b). The results show that, to a first order, the records match well the marine 818O record (MIS), but that the last interglaciation appears to span the entire period from 120 to 53 ka (corresponding to 36- 75 m depth in the core, see Fig. 2). The interglaciation appears to have been punctuated by three short periods of wetter, spilling-lake conditions during an otherwise dry climate. This study also revealed that the timing of Termination II, the end of the penultimate glaciation, is proxy-dependent. The onset of the last interglaciation is shown by abrupt increases in a number of parameters including authigenic CaCOs and an abrupt decrease in rock flour, at about 118 ka (at 75.0 m). according to our time scale. In contrast, the boundary appears to be gradual in the 818O record in which the change from light to heavy values begins at about 140 ka (85.5 m depth). Conditions of high carbonate and low rock-flour prevailed during the entire period from 118 ka until the glacial advance at 53 ka (36 m depth) signaled the end of this long interglaciation. The present study was focused on the Last Interglaciation, referred to as MIS 5 in the marine record, or as Sangamon and Eemian in the North American and European continental records respectively. The objective was to obtain a high resolution record of this interval as a comparison to the Holocene, in order to observe fine-scale climatic departures not observable at the resolution of the earlier studies. The earlier studies identified the interval 36-75 m depth in the core as representing this interglaciation. Accordingly, in order to include the transitions of the beginning (MIS 5/6 boundary) and end (MIS 4/5 boundary) sampling spanned the interval from 32-83 m depth, representing the time span of ca 35-145 ka. Channel samples each of 10 cm length were taken continuously through this interval, with each sample representing about 250 years. These samples were dried and homogenized by light grinding, and aliquots were split for 1.) TIC, TOC and acid-leachable chemistry (Bischoff and others, part 3), 2.) 818O and 813C and mineralogy of the carbonate fraction, (Li and others, parts 4 and 5) 3.) pollen studies (Litwin, part 9), and 4.) magnetic studies including bulk chemical analyses (Reynolds and others, part 6). In a second suite, point samples were taken approximately every 10 to 20 cm for diatoms (Bradbury and Paquette, part 7) and every 20 cm for ostracodes (Forester and Carter, part 8). In addition, the sedimentary features of the interval were described and photographed in fine detail (Smoot, part 2). Also presented are the preliminary results of continuing efforts to improve the geochronology U-series results on 6 ostracode samples (Bischoff and others part 10) and the results of optical dating of 8 samples (Berger, part 11). The purpose of the present volume is to present the data collected by the collaborating investigators in a single document. Data are reported in terms of depth rather than time because the chronology of the core is subject to refinement and further improvement. Because the data are correlative from study to study, the volume provides a basis for in- depth analysis and interpretation by each principle investigator of his own data in light of the data obtained by others, and a citable data base for the preparation of formal publication in the outside literature. ACKNOWLEDGMENTS The chapters in this collection benefited from careful reviews by G.I. Smith, John Barron, Brian Edwards, and Robert Rosenbauer. I thank them warmly for their considerable efforts and for the many useful suggestions. REFERENCES Bischoff, J.L., Stafford, T.W., Jr., and Rubin, M. (1997a). A time-depth scale for Owens Lake sediments of core OL-92: Radiocarbon dates and constant mass-accumulation rate. In "An 800,000-year geologic and climatic record from Owens Lake, California: Core OL-92" (G.I. Smith and J. Bischoff, Eds.), pp. 91-98. Geological Society of America Special Paper 317. Bischoff, J.L., Menking, K.M., Fitts, J.P., and Fitzpatrick, J.A. (1997b). Climatic oscillations 10,000-155,000 yr B.P. at Owens Lake, California reflected in glacial rock flour abundance and lake salinity in core OL-92. Quaternary Research. 48, 313-325. Menking, K.M., Bischoff, J.L., Fitzpatrick, J.A., Burdette,vJ.W., and Rye, R.O. (1997). Climatic/hydrologic oscillations since 155,000 yr B.P. at Owens Lake, CA, reflected in abundance and stable isotope composition of sediment carbonate. Quaternary Research. 48, 58-68. Smith, G.L, and Bischoff, J.L., eds (1993). Core OL-92 from Owens Lake, southeast California. U.S. Geological Survey Open File Report 93-683. Smith, G.L, and Bischoff, J.L., eds. (1997). An 800,000-year geologic and climatic record from Owens Lake, California: Core OL-92 Geological Society of America Special Paper 317. "2. Smith, G.I., Bischoff, J.L., and Bradbury, J.P. (1997).