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Predictive models for the deep geometry of a thick-skinned thrust matched to crustal structure; Wind River Range, Western USA

Richard H. Groshong and Ryan Porter
Predictive models for the deep geometry of a thick-skinned thrust matched to crustal structure; Wind River Range, Western USA
Lithosphere (April 2019) 11 (4): 448-464

Abstract

The ability of models designed to use near-surface structural information to predict the deep geometry of a faulted block is tested for a thick-skinned thrust by matching the surface geometry to the crustal structure beneath the Wind River Range, Wyoming, USA. The Wind River Range is an approximately 100-km-wide, thick-skinned rotated basement block bounded on one side by a high-angle reverse fault. The availability of a deep seismic-reflection profile and a detailed crustal impedance profile based on teleseismic receiver-function analysis makes this location ideal for testing techniques used to predict the deep fault geometry from shallow data. The techniques applied are the kinematic models for a circular-arc fault, oblique simple-shear fault, shear fault-bend fold, and model-independent excess area balancing. All the kinematic models imply that the deformation cannot be exclusively rigid-body rotation but rather require distributed deformation throughout some or all of the basement. Both the circular-arc model and the oblique-shear models give nearly the same best fit to the master fault geometry. The predicted lower detachment matches a potential crustal detachment zone at 31 km subsea. The thrust ramp is located close to where this zone dies out to the southwest. The circular-arc model implies that the penetrative deformation could be focused at the trailing edge of the basement block rather than being distributed uniformly throughout and thus helps to explain the line of second-order anticlines along the trailing edge of the Wind River block. Key points: (1) The circular-arc fault model and the oblique-shear model predict a lower detachment for the Wind River rotated block to be approximately 31 km subsea, consistent with the crustal structure as defined by teleseismic receiver-function analysis. The thrust ramp starts where this zone dies out. (2) The kinematic models require distributed internal deformation within the basement block, probably concentrated at the trailing edge. (3) The uplift at the trailing edge of the rotated block is explained by the circular-arc kinematic model as a requirement to maintain area balance of a mostly rigid block above a horizontal detachment; the oblique-shear model can explain the uplift as caused by displacement on a dipping detachment.


ISSN: 1941-8264
EISSN: 1947-4253
Serial Title: Lithosphere
Serial Volume: 11
Serial Issue: 4
Title: Predictive models for the deep geometry of a thick-skinned thrust matched to crustal structure; Wind River Range, Western USA
Affiliation: University of Alabama at Tuscaloosa, Department of Geological Sciences, Tuscaloosa, AL, United States
Pages: 448-464
Published: 20190416
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 77
Accession Number: 2019-036119
Categories: Applied geophysicsStructural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
N42°45'00" - N43°30'00", W109°30'00" - W108°30'00"
N42°00'00" - N44°00'00", W110°00'00" - W108°00'00"
Secondary Affiliation: Northern Arizona University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201919
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