2 Exhumation and Uplift of the Sierra Nevada and Tehachapi Mountains

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

UPLIFT IN THE SIERRA NEVADA: EXTENSIVE GEOLOGIC FIELD EVIDENCE THROUGHOUT THE RANGE SUPPORTS MAJOR LATE CRETACEOUS UPLIFT PLUS MAJOR INCISION INTO THE EOCENE

Paper number: 2-12
Program: Theme Sessions
Time: 11:20 AM – 11:40 AM

Authors

Abstract

The notion of late Cenozoic uplift was implied by Whitney (1865), who assumed a buried bedrock canyon lay beneath the Table Mountain latite flow, rather than what exists in the Stanislaus River drainage: latite remnants preserved atop bedrock ridges and benches. We name this concept the Late Cenozoic Uplift Paradigm (LCUP), and propose our own Late Cretaceous Uplift Paradigm (LKUP). We describe 30 key sites of ca. 300 in the range, from the Feather River south to the Kern River. These sites include Late Cretaceous to Eocene strata, Oligocene rhyolites, Mio-Pliocene andesites, and Plio-Pleistocene basalts, some remnants on canyon floors and most others on lower slopes, preserving topography at the time of deposition. Neither incision nor slope retreat have occurred at two sites since the Oligocene. This lies in contrast to the LCUP, which postulates all incision, and therefore uplift originating in the last 20 Ma in the south to 3 Ma in the north. Our work includes an extensive set of Ar-Ar dates, plus previously published ones, ours including areas where significant late Cenozoic uplift and canyon incision is proposed. Moreover, our results demonstrate a common uplift history, with crest elevation, drainage topography, and relief developed in the early Cenozoic, and only minor changes in post-Eocene time, thus supporting Stanford University research in the northern Sierra. Newer technologies, such as cosmogenic dating of cave sediments, cosmogenic measurements of slope erosion, real-time GPS and InSAR measurements projected back in time, and especially thermochronometry, yield results inconsistent with surface evidence.

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

doi: 10.1130/abs/2020CD-346925

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