2 Exhumation and Uplift of the Sierra Nevada and Tehachapi Mountains

Tuesday, 12 May 2020
8:00 AM - 12:00 PM
Plaza Room

PALEOMAGNETIC ANALYSIS OF A POTENTIAL ERUPTIVE SOURCE FOR KENNEDY TABLE

Paper number: 2-5
Program: Theme Sessions
Time: 9:05 AM – 9:25 AM

Authors

Abstract

The trachyandesite at Kennedy Table east of Friant, CA is a 10.2 Ma mesa of previously unknown source. The stratigraphy, position and appearance all indicate that it formed as a lava flow that filled in the paleochannel of the San Joaquin River (Huber 1981). Hildreth & Fiersteins (2016) proposed correlation between it and lava flows near Mammoth, CA, would have the potential to more accurately constrain the uplift of the Sierras during the last 10 Ma. We focussed on a trachyandesite outcrop identified by Hildreth & Fierstein to be 9.16 +/- 0.02 Ma near Mammoth, CA as the potential source. This age is statisticaly indistinguishable from that of Manley et. al. (2000), 9.31 +/- 0.30 Ma recalculated for the latest K decay constant. We used hand samples from the proposed source at Mammoth for paleomagnetic and geochemical analysis intended to either match it to the Kennedy Table, or eliminate it as a source. The final results of analysis indicate a possible correlation, as both lava flows are normal polarity, and the average direction of ChRM magnetism was similarly oriented. We note that Hildreth & Fierstein’s 40Ar/39Ar date and our normal polarity result are inconsistent, either indicating slightly inaccurate age or the presence of a previously-unknown normal-polarity excursion or subchron 9.16 +/- 0.02 Ma. Overall, our data is consistent with the correlation hypothesis.

Geological Society of America Abstracts with Programs. Vol. 52, No. 4

doi: 10.1130/abs/2020CD-347471

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.