T160 Grand Canyon, Colorado Plateau, and Rocky Mountain Debates and Their Global Reverberations, 150 Years after Powell II

Tuesday, 24 September 2019
8:00 AM - 12:00 PM
Room 221AB, North Building

CATASTROPHIC SHEAR-REMOVAL OF SUBCONTINENTAL LITHOSPHERIC MANTLE BENEATH THE COLORADO PLATEAU BY THE SUBDUCTED FARALLON SLAB

Paper number: T160-11
Program: Technical Sessions
Time: 10:20 AM – 10:35 AM

Authors

Abstract

The causes of Cenozoic uplift of the Colorado Plateau, southwestern USA, are strongly debated, though most hypotheses acknowledge the importance of northwest-directed subduction of the Farallon oceanic plate beneath North America since c. 100 Ma. Existing thermomechanical models suggest that the Farallon slab underthrust the proto-plateau region at ~200 km depth, removing the basal portions of its subcontinental lithospheric mantle (SCLM) root, although such small-volume subduction erosion cannot fully account for the degree of uplift observed today. Here we show via petrological modeling of lawsonite-bearing eclogite xenoliths exposed in diatremes in the center of the plateau that the Farallon slab surface penetrated through the proto-plateau SCLM at much shallower depths (~120 km) than these previous estimates, allowing shear-removal of ~80 km of SCLM – a volume up to three-times greater than previously suggested. This removal led to asthenospheric upwelling and isostatic rebound of the plateau region during the late Cretaceous to the Eocene. We posit that similar shear-removal of SCLM likely played a major role in inhibiting cratonic growth and stabilization in the Neoarchean and Paleoproterozoic – when low-angle subduction of oceanic lithosphere was more prevalent than today – accounting for the atypically thin roots existing below many ancient cratons worldwide.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-332886

© Copyright 2019 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.