PALEOMAGNETIC ANALYSIS OF A POTENTIAL ERUPTIVE SOURCE FOR KENNEDY TABLE

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.