15 The Kinematics, Dynamics, and Surface Expression of Faults in Eastern California—Improving Hazard Forecasts and Long-Term Slip Histories

Tuesday, 12 May 2020
1:30 PM - 5:30 PM
Madera Room

HIGH-RESOLUTION ANIMATED TECTONIC RECONSTRUCTION OF THE DEATH VALLEY REGION

Paper number: 15-8
Program: Theme Sessions
Time: 3:45 PM – 4:05 PM

Authors

  • Brandon M Lutz Presenting Author
    New Mexico Tech, Socorro, NM
  • Gary Axen
    New Mexico Inst Mining and TechnologyDept. Earth & Environmental Science, Socorro, NM
  • Fred Phillips
    New Mexico Institute of Mining and Technology, Socorro, NM
  • Jolante van Wijk
    New Mexico Institute of Mining and Technology, Socorro, NM

Abstract

We have developed a new Miocene-Holocene tectonic reconstruction of the Death Valley region. A comprehensive database of offset features and fault slip-rates constrains the kinematic model. Map-view deformation is interpolated in 0.1-Myr time-steps. Two major tectonic transitions emerge: at ca. 12 Ma, rapid extension (~14-15 mm/yr), accommodated on regional detachment faults, began between the Sierra Nevada and Spring Mountains; at ca. 6 Ma, Sierran motion relative to stable North America slowed by ~10 mm/yr, coincident with the southern San Andreas fault relocating onto the Gulf Extensional Province. From ca. 6-3.5 Ma, slip rates on western fault systems of the region accelerated as intraplate strain localized in a zone ~100 km wide east of the Sierra Nevada. From ca. 3.5-0 Ma, Sierra Nevada-North American relative velocity approached modern values of ~11.5 mm/yr.

Mechanical coupling between brittle crust and continental mantle lithosphere appears to have strengthened at ca. 6-3.5 Ma, coincident with an intraplate rheological feedback. Thermo-kinematic modeling and crustal thickness reconstructions suggest that the upper crust was decoupled from lower crust/mantle lithosphere by weak middle crust prior to ca. 6 Ma. Subsequent exhumation, thinning, cooling, and embrittlement of the weak middle crust enhanced crust-mantle coupling via juxtaposition of gabbroic lower crust beneath exhumed/embrittled middle crust. This enabled mantle flow to drive upper-crustal strain, focusing dextral shear into the ~100 km-wide zone east of the Sierra Nevada.

Enhanced crust-mantle coupling following mid-crustal exhumation/embrittlement coincided with the northward propagation of dextral shear into the Walker Lane belt. A NW-oriented, dextral deflection in lithosphere-asthenosphere boundary slope, with magnitude and azimuth similar to post-6-3.5 Ma Sierra Nevada motion, suggests penetrative dextral shear of the entire lithosphere.

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

doi: 10.1130/abs/2020CD-347387

© 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.