Glaciogenic Effects During MIS 2 On The Lacustrine Sediment Flux Of Tulare Lake.

Abstract

Physical and chemical changes in the lithology of deposited sediment can act as proxies for past lake levels and, hence, climate change, particularly when terminal lake basins are studied. Ever since the MIS 2 glacial maximum one such lake, Tulare Lake, CA, has been the terminus of four of the largest rivers from the southern Sierra Nevada Mountains and hydrologic modeling has shown that its surface elevation is a good gauge of Sierran stream discharge. Here we present two chronologies which extends the relative paleolake-level record of Tulare Lake from the TL05-4 cores based on geochemical and geophysical proxies back to 29 or 44 cal kyr BP. Proxy data from these cores include magnetic susceptibility, grain size, total inorganic and organic carbon, and carbon-nitrogen ratios. To some extent, these data co-vary and based on comparisons with earlier trench sample based lake-level records, reflect relative lake level. The earliest part of the record shows millennial scale cyclic fluctuations of grain size which may relate to regional climate. After this, Tulare Lake experienced a sharp increase in lake level, likely associated with the creation of a small fan dam around 25 cal kyr BP. Lake level gradually decreased during the Tioga Glaciation (25-15 cal kyr BP). This may have been caused by decreased summer precipitation and winter precipitation that has been sequestered in the snowpack. During the late Tioga Glaciation, large amounts of runoff from the melting glaciers and addition of water from the Kings River filled the lake and significantly increase the sill height of the fan dam (18.6-15 cal kyr BP) to more or less present elevations. After this, Tulare Lake levels stabilized and varied in conjunction primarily due to changes in sea surface temperatures. Lack of age control prior to 24 cal kyr BP leaves some ambiguity between age models, both of which have merit. Further age dates are expected to refine the model and extrapolate lacustrine sediment changes to regional climate change.

AAPG Datapages/Search and Discovery Article #90215 © 2015 Pacific Section AAPG Convention, Oxnard, California, May 3-6, 2015