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Waucobi Seismic Study 2015

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Tent in a field

The sedimentary record in Owens Valley provides constraints on the timing and mechanism of the most recent uplift of the Sierra Nevada.  Studies of the Waucobi Lake Beds (De Masi, 2013) show that the exposed lacustrine section near Big Pine, CA represents a transtensional basin of late Pliocene age.  The 120 meters of exposed lacustrine deposits identified in Waucobi have been radiometrically dated (Ar/Ar) and range between 2.65-2.1 Ma, and are unconformably overlain by a fanglomerate, containing a tuff dated 1.04 Ma.  This interval of lacustrine deposition is coeval with dessication events in several surrounding paleo-lakes, indicating that the capture of freshwater in the basin was controlled by tectonics rather than by climate.

The increased tectonic activity that created the Waucobi embayment was likely contemporaneous with the most recent uplift of the Sierra Nevada.  The oldest lacustrine sediments in Waucobi can address competing models for the uplift of the Sierra Nevada and the timing of extension of the westernmost Basin and Range. To address this issue we conducted an active source seismic study near Duchess Canyon, which contains 91 meters of exposed lacustrine sediments dated 2.65-2.35 Ma. Our results suggest basement at ~300m depth.  Projecting the sedimentation rate from Duchess Canyon (0.3 m/kyr) the lakebed-basement contact may be as old as 3.25 Ma.