Late Pleistocene California Droughts During Deglaciation and Arctic Warming

J. L. Oster¹, I. P. Montanez¹, and W. D. Sharp^2
1University of California, Davis, [email protected], [email protected]
²Berkeley Geochronology Center, Berkeley, CA, [email protected]

A stalagmite from Moaning Cave in the central Sierra Nevada (38°N), California, records abrupt changes in stable and radiogenic isotopes and trace elements approximately coeval with the Younger Dryas and Bølling/Allerød climatic events. The stalagmite precipitated without visible discontinuity from 18 to 8 ka based on ²³⁰Th/U dating. d¹⁸O and d¹³C profiles measured along the stalagmite growth axis are reproducible in off-axis transects, consistent with precipitation of the stalagmite in isotopic equilibrium with drip water.

Moaning Cave speleothem d¹⁸O, d¹³C, [Mg], [Sr], [Ba], and ⁸⁷Sr/⁸⁶Sr document sub-centennial changes in water-soil-rock interactions, driven by changes in precipitation in the Sierra Nevada during the last deglaciation. From 16.5 to 10.6 ka, the Moaning Cave stalagmite proxies record drier and possibly warmer conditions, signified by elevated d¹⁸O, d¹³C, [Mg], [Sr], and [Ba] and more radiogenic ⁸⁷Sr/⁸⁶Sr, during Northern Hemisphere warm periods (Bølling, early and late Allerød) and wetter and possibly colder conditions during Northern Hemisphere cool periods (Older Dryas, Inter-Allerød Cold Period, and Younger Dryas). Despite the influence of local hydrology on the trace element records between 10.6 and 9.6 ka, the Moaning Cave stable isotope records indicate wet conditions persisted in this area well beyond 11.5 ka, suggesting the effects of the Younger Dryas event may have been longer lived in the western Sierra Nevada than in Greenland. The Moaning Cave record provides new insight into the climatic impacts of the Younger Dryas and Bølling/Allerød in California and the teleconnections between the study region, the North Atlantic, and Europe during abrupt climatic events.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009