2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 336-2
Presentation Time: 1:45 PM


GLOVER, Katherine C., Geography, UCLA, UCLA Dept. of Geography, 1255 Bunche Hall, Los Angeles, CA 90095, MACDONALD, Glen M., Department of Geography, University of California at Los Angeles, 1255 Bunche Hall, Los Angeles, CA 90095, KIRBY, Matthew E., Geological Sciences, California State University, Fullerton, 800 N. State College Blvd, Fullerton, CA 92831, RHODES, Edward J., Department of Geography, The University of Sheffield, Sheffield, S10 2TN, United Kingdom; Earth and Space Sciences, University of California, Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095, STEVENS, Lora, Department of Geological Sciences, California State University Long Beach, Long Beach, CA 90840, LYDON, Scott, Dept of Geography, UCLA, 1255 Bunche Hall, Los Angeles, CA 90095, SILVEIRA, Emily, Department of Geological Sciences, California State University, Fullerton, 800 N State College Blvd, McCarthy Hall, room 254, Fullerton, CA 92831 and WHITAKER, Alexis, Institute of the Environment and Sustainability, UCLA, 300 La Kretz, Los Angeles, CA 90095, kcglover@ucla.edu

Retrospective studies from lake records can provide insight into linkages between terrestrial systems and climate change. Knowledge of the past range of variability can inform predictions for an uncertain future, currently an urgent research need in water-stressed and populous Southern California. Here we present a continuous 26.5 m record from alpine Southern California, with potential to fill this spatiotemporal gap in our understanding of western U.S. paleoclimate prior to Marine Isotope Stage 2 (MIS 2, c. 29 ka). Located in Big Bear Valley of the San Bernardino Mountains, the Baldwin Lake core spans c. 95.9 – 10 ka, based on AMS radiocarbon dating and infra-red stimulated luminescence dating. Magnetic susceptibility and x-ray fluorescence data show that Baldwin Lake was a closed-basin, stratified lake for much of its history, with lowstands and bottom ventilation during transitions from glacial to interglacial periods (c. 60-57 ka, c. 15-12 ka). Slow sedimentation rates and a greater proportion of terrigenous input occurred during MIS 2, eventually transitioning to a calcium-rich massive clayey silt facies that reflect intermittent lake conditions by ~11 ka, and a playa surface during the Holocene. Bulk organic content, derived from loss-on-ignition, correlates with insolation values at 34˚N throughout the sequence. Ongoing biogenic silica analysis aims to test if paleoinsolation was the primary climatic driver in alpine Southern California from MIS 5 -1.