Abstract: Magnetic Susceptibility as a Proxy for Climate Change in Greater Than 250,000 Year Old Sediments in Northwestern Great Basin, U.S.A.

QUILLIAM, MICHAEL, California State University, Bakersfield, Bakersfield, CA; SHANDI ALEXANDER MEYER; ROB NEGRINI, California State University, Bakersfield, Bakersfield, CA

Previous studies demonstrated that the magnetic susceptibility of 0 - 250,000-year-old lacustrian sediments from Summer Lake, Oregon correlated with Oxygen-18 isotope stratigraphy. This correlation was based upon a foundation of independent age control including radiocarbon data, thermoluminescence dating, correlation of paleosecular variation features and volcanic tephrochronology.

In our study we built upon this initial work by extending the age control of the Summer Lake sediments to ~ 350,000 years using magnetic susceptibility alone. The study was conducted using two adjacent cores with overlapping drives drilled adjacent to the outcrop containing the sediments of the original study. The previous study relied on time-consuming measurements on discrete sampling using bottle-tube sensors. Our study used both discrete sampling and a more efficient whole-core ring sampling method on a subset of both cores. Because the results showed excellent overall correlation between sampling methods ring sampling was used on the remaining core. Geochemical fingerprinting of tephra layers found within the older sediments of this study and their comparison with known radiometric dates may verify our methods.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California