T96 Cenozoic Tectonism, Magmatism, Sedimentation, and Landscape Evolution in the Intermountain West (Posters)

Monday, 11 October 2021
9:00 AM - 1:00 PM
Exhibit Hall A

FRICTION-DRIVEN THERMAL DECOMPOSITION AND SYNKINEMATIC FABRICS OF CARBONATES IN THE HEART MOUNTAIN SLIDE, WYOMING

Paper number: T96-4
Program: Technical Sessions
Time: 9:00 AM – 1:00 PM

Authors

Abstract

Cataclastic deformation has long been considered to produce unfoliated rocks, i.e., materials devoid of a tectonic fabric. However, the 3 m-thick carbonate ultracataclasite formed by the Heart Mountain Slide, in Wyoming, has a consistent subhorizontal magnetic fabric across its thickness. This ultracataclasite layer developed in the Eocene during one of the largest known continental landslide on Earth (~3,500 km2). A mid-Eocene eruption in the Absaroka volcanic province most likely triggered rupture and subsequent detachment of a ~1 km-thick Paleozoic sedimentary cover. The rapid sliding was enhanced by basal fluidization due by thermo-mechanical decomposition of carbonate rocks and coeval massive production of gaseous CO2. The ultracataclasite layer has a spatially-consistent, strong magnetic fabric, whereas host carbonates preserve their weak sedimentary fabric. The anisotropy of magnetic susceptibility (AMS) arises from synkinematically deformed, pseudo-single domain magnetite grains formed by thermal decomposition of primary iron sulfides. The ultracataclasite does not generally show a visible macroscopic fabric. Yet, the strong AMS in these deformed rocks records the transport direction of the landslide. These results indicate that friction-driven decomposition of carbonates may generate consistent synkinematic fabrics and therefore that some cataclasites/ultracataclasites may indeed bear a foliation.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-370893

© Copyright 2021 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.