Catastrophic shear-removal of subcontinental lithospheric mantle beneath the Colorado Plateau by the subducted Farallon slab

David Hernández-Uribe,Richard M Palin

doi:10.1038/s41598-019-44628-y

David Hernández-Uribe, Richard M Palin

Open Access

https://doi.org/10.1038/s41598-019-44628-y

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Journal: Scientific Reports	Publication Date: May 31, 2019
Citations: 17	License type: open-access

Affiliation: Colorado School of Mines

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.

Highlights

The present-day elevation, thickness, and lithospheric structure of the Colorado Plateau, southwestern USA, is well-constrained by satellite observations[1], digital elevation models[2], and regional-scale geophysical investigations[3,4,5,6,7,8]
Tectonic reconstructions of the recent geological history of the Colorado Plateau indicate various stages of uplift related to the northeastward subduction of the Farallon oceanic plate beneath the southwestern USA during the Late Cretaceous and Early Cenozoic[23,24,28], the exact geodynamic processes responsible remain subject to debate[29]
If our knowledge of the rates and styles of metamorphism and tectonic deformation are poorly constrained, the results and implications drawn from thermo-mechanical simulations become less reliable

Summary

Introduction

The present-day elevation, thickness, and lithospheric structure of the Colorado Plateau, southwestern USA, is well-constrained by satellite observations[1], digital elevation models[2], and regional-scale geophysical investigations[3,4,5,6,7,8]. Geophysical profiles of the adjacent and undeformed Great Plains, eastern Colorado, show SCLM to a depth of ~200 km[25], indicating large-scale shear-removal of at least ~80 km of the pre-uplifted Colorado Plateau’s mantle keel – notably larger than volumes predicted by previous thermomechanical and petrological models. This effect is likely to have been significantly important in the Late Archean and Proterozoic, when low-angle subduction of oceanic lithosphere was more prevalent than today. Tectonic reconstructions of the recent geological history of the Colorado Plateau indicate various stages of uplift related to the northeastward subduction of the Farallon oceanic plate beneath the southwestern USA during the Late Cretaceous and Early Cenozoic[23,24,28], the exact geodynamic processes responsible remain subject to debate[29]

Methods

Conclusion