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The southern Sierra Nevada pediment, central California

Sousa, Francis J. and Saleeby, Jason and Farley, Kenneth A. and Unruh, Jeffrey R. and Lloyd, Max K. (2017) The southern Sierra Nevada pediment, central California. Geosphere, 13 (1). pp. 82-101. ISSN 1553-040X.

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The southern Sierra Nevada foothills, central California (USA), expose a fossil pre–40 Ma bedrock pediment which we call the southern Sierra Nevada pediment. We document this landscape with multiple types of data, and also report new apatite ^4He/^3He, (U-Th)/He, and zircon (U-Th)/He data from the pediment that significantly expand the spatial extent of southern Sierra low-temperature thermochronology data westward into the foothills. Applying recently published thermal modeling software for thermochronologic data, which uses a transdimensional Bayesian Monte Carlo Markov chain statistical approach, we tightly constrain the thermal history of the southern Sierra Nevada pediment. Integrating this thermal history with numerous previously published data sets from across the southern Sierra, we present a chronology of tectonic and landscape evolution of the southern Sierra Nevada. For the first time we cover the entire width of the range, integrate the numerous published data sets into a single coherent geologic story, and link each phase of this story to a potential mechanism. Modeling results are consistent with a three-phase cooling history for the southern Sierra Nevada pediment. Rapid exhumation ca. 95–85 Ma resulted in cooling to between 55 °C and 100 °C. Following this, slow cooling to surface conditions occurred from 85 Ma to 40 Ma at rates consistent with those estimated for the axial southern Sierra during the same time period by previous studies. Little if any additional cooling occurred post–40 Ma. We hypothesize that a thin sedimentary cover protected the 40 Ma bedrock landscape through much of the last 40 m.y., and that this cover eroded away post–10 Ma, re-exhuming the southern Sierra Nevada pediment as a fossil pre–40 Ma landscape. Each of these three phases of cooling links to a distinct tectonic or geomorphic regime, including the profound rapid exhumation of the southern Sierra Nevada–Mojave segment of the Cretaceous arc due to subduction of a large oceanic plateau, the formation of the low-relief landscape of the high-elevation areas of the southern Sierra Nevada with more limited tectonic forcing, and Eocene activity on the Western Sierra Fault System.

Item Type:Article
Related URLs:
URLURL TypeDescription
Sousa, Francis J.0000-0003-1623-4023
Farley, Kenneth A.0000-0002-7846-7546
Lloyd, Max K.0000-0001-9367-2698
Additional Information:© 2016 Geological Society of America. Received 24 May 2016. Revision received 17 August 2016. Accepted 20 October 2016. First Published on November 11, 2016. Themed Issue: Origin and Evolution of the Sierra Nevada and Walker Lane. Guest editors: Keith D. Putirka and Cathy J. Busby. We thank Kerry Gallagher for assistance with setting up QTQt runs and Lindsey Hedges for help with sample preparation, analyses, and a life full of friendship. Thanks to Guest Associate Editor Cathy Busby and two anonymous reviewers for constructive reviews of this manuscript. This work was partially supported by the Gordon and Betty Moore Foundation through grant GBMF #423.01 to the Caltech Tectonics Observatory.
Group:Caltech Tectonics Observatory
Funding AgencyGrant Number
Gordon and Betty Moore Foundation423.01
Issue or Number:1
Record Number:CaltechAUTHORS:20161117-085737387
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Official Citation:Francis J. Sousa, Jason Saleeby, Kenneth A. Farley, Jeffrey R. Unruh, and Max K. Lloyd The southern Sierra Nevada pediment, central California Geosphere, February 2017, v. 13, p. 82-101, first published on November 11, 2016, doi:10.1130/GES01369.1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72102
Deposited By: Tony Diaz
Deposited On:17 Nov 2016 17:29
Last Modified:09 Mar 2020 13:19

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