COEVAL, IN- AND OUT-OF-SEQUENCE DEFORMATION WITHIN THE FRONTAL THRUST SHEETS OF THE TENDOY MOUNTAINS, SW MONTANA
ANASTASIO, David J., HARKINS, Nathan W., and LATTA, Diana K., Earth and Environmental Sciences Dept, Lehigh Univ, 31 Williams Dr, Bethlehem, PA 18015, dja2@lehigh.edu

Structural and synkinematic stratigraphic relationships within the Tendoy Mountains, Montana recess, record broadly coeval, in-, and out-of-sequence deformation within the Sevier foreland. New mapping of the Dixon Mountain 7.5 minute quadrangle (DOI-USGS EDMAP) provides evidence of the emergence and emplacement of several thrust sheets. Exposures of the Beaverhead Conglomerate, an extensive Cretaceous alluvial deposit, record details of synsedimentary deformation along the thrust front. During emplacement, the Tendoy thrust sheet overrode proximal Beaverhead detritus and developed kilometer scale transverse folding in response to complex oblique ramp geometry. The Deadwood Gulch thrust, a leading-edge imbricate of the Tendoy, was later emplaced over the Tendoy thrust and sourced olistostromes within younger Beaverhead strata. While the majority of displacement on the Four Eyes Canyon thrust, the next hinterward major thrust sheet was in sequence, it also experienced late emergent out-of-sequence activity as recorded by overthrusting of synthetically derived synorogenic conglomerates within the Tendoy sheet wedge-top basin. Hinterward dips within these conglomerates suggest that there was some late stage in-sequence movement along the underlying Tendoy thrust or on a more frontal décollement associated with Beaverhead deformation within the Red Rock Valley.

Rocky Mountain - 54th Annual Meeting (May 7–9, 2002)
Session No. 3--Booth# 1
National Cooperative Geologic Mapping Program—New Maps, New Research, New Discoveries (Posters)
Sharwan Smith Center: Ballroom
8:00 AM-12:00 PM, Tuesday, May 7, 2002
 

© Copyright 2002 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.