The Quaternary Climate Record from Pluvial Lakes in the Great Basin: Relationship to Global Climate Change
R. M. Negrini
Department of Physics and Geology, California State Univ Bakersfield, Bakersfield, CA
Lakes from the internally-drained Great Basin of western North America are potentially ideal repositories of Quaternary climate records for several reasons. For example, the location of the Great Basin is such that precipitation/evaporation ratios should respond significantly both to changes in surface water temperature in the adjacent NE Pacific and to changes in the mean position of the polar jet stream. The amassing of a representative collection of climate records from Great Basin lakes is progressing slowly but steadily though the quality of independently determined age control and of lake-size measurements varies greatly between records. Milankovitch-scale climate change is particularly well represented as several records contain variations in lake conditions with the approximate timing and morphology as the marine oxygen isotope proxy for global ice volume. To a first order, these records support the well known migrating jet stream hypothesis first forwarded early in the twentieth century by Ernst Antevs. More recently, higher resolution records have been recovered which exhibit millennial scale variations in lake conditions. These variations are arguably coincident and have the same relative amplitudes of higher frequency global climate variations such as Bond cycles and Dansgaard-Oeschger oscillations. These results, in conjunction with similar results from offshore western North America, support computer simulations of high frequency response in the NE Pacific region to climate changes originating in the North Atlantic region.
The potential of the Great Basin for long term, high resolution records of Quaternary climate has been barely tapped. There is a particularly strong need for greater geographic coverage both latitudinally and longitudinally. This will allow more refined testing of climate models. Also, replication of records in nearby basins is important as gaps in records from any basin due to processes like deflation can be difficult to detect. Such undetected gaps may seriously affect conclusions regarding timing of climate change when the assumption of constant accumulation rate is used across such intervals.
AAPG Search and Discovery Article #90904©2001 AAPG Pacific Section Meeting, Universal City, California