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Step-over in the structure controlling the regional west tilt of the Sierra Nevada microplate: eastern escarpment system to Kern Canyon system

Saleeby, J. and Saleeby, Z. and Nadin, E. and Maheo, G. (2009) Step-over in the structure controlling the regional west tilt of the Sierra Nevada microplate: eastern escarpment system to Kern Canyon system. International Geology Review, 51 (7-8). pp. 634-669. ISSN 0020-6814.

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The Sierra Nevada and Great Valley are coupled, and behave as a semi-rigid microplate. The microplate formed as it was calved off the western edge of the Nevadaplano in the late Miocene, at which time westward regional tilting began. Tilting is controlled by west-side-up normal faulting primarily along the eastern Sierra escarpment system. Uplift and exhumation along the eastern Sierra are balanced by subsidence and sedimentation along the western Great Valley. The west tilt of the microplate is expressed by the west slope of a regional relict landscape surface that developed across much of the Sierra Nevada basement, and by the westward continuation of the surface as the basal Eocene nonconformity of the west-dipping Great Valley Tertiary section. The rigid behaviour of the microplate breaks down along its southern ~100-150 km segment as expressed by seismicity, pervasive faulting and the development of a deep marine basin, the San Joaquin Basin (SJB), whose facies and palaeogeographic patterns diverge from regional patterns of the rest of the Great Valley. The disrupted state of the southern segment of the microplate resulted from its Late Cretaceous position above a regional lateral ramp in the underlying Franciscan-related subduction megathrust. The Kern Canyon fault system began its polyphase history as a complex oblique dextral shear zone above the megathrust lateral ramp. It was remobilized in the Neogene as an oblique transfer structure partitioning differential extension between the southern Sierra Nevada and the SJB. In Quaternary time, the Kern Canyon zone was again remobilized as a west-side-up normal fault system whose geomorphic and structural expressions are best developed south of ~36.4° N. This normal fault system controls the west tilt of the relict landscape surface in the southern Sierra region, as well as the west dip pattern in the strata of the adjacent SJB. To the east of the Kern Canyon normal fault system, the relict landscape surface slopes continuously southwards from the high eastern Sierra into a low-lying, multiply extended terrane. Thus, from ~36.4° N southwards, the west tilt along the western Sierra and the west dip of the adjacent Great Valley strata are controlled by the Kern Canyon system. Fresh normal scarps along the eastern Sierra escarpment system become more subdued and ultimately die out southwards from ~36.4° N. Thus, currently, the controlling structure for the west tilt of the microplate steps westwards in the south from the eastern escarpment system over to the Kern Canyon system.

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Additional Information:© 2009 Taylor & Francis. Accepted 27 February 2009. Discussions with Marin Clark, Tor Nilsen, Laetitia Le Pourhiet, Jeff Unruh, and John Wakabayashi were helpful for this synthesis. Critical reviews by Cathy Busby and Brian Wernicke are kindly acknowledged. Our research compiled in this synthesis was made possible by NSF grants EAR 0230383 and 0606903, and funds from the Gordon and Betty Moore Foundation. Caltech Tectonics Observatory Contribution no. 105.
Group:Caltech Tectonics Observatory
Funding AgencyGrant Number
NSFEAR 0230383
NSFEAR 0606903
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:microplate; remobilization; delamination; epeirogeny
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Caltech Tectonics Observatory105
Issue or Number:7-8
Record Number:CaltechAUTHORS:20101112-112547370
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20774
Deposited By: Tony Diaz
Deposited On:17 Nov 2010 22:21
Last Modified:03 Oct 2019 02:14

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