GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 9-8
Presentation Time: 11:10 AM


THIGPEN, J. Ryan1, BROWN, Summer J.1, MCGLUE, Michael M.1, WOOLERY, Edward W.2, HOAR, Rachel M.3, GUENTHNER, William R.4, GALLEN, Sean F.5 and SWALLOM, Meredith L.1, (1)Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY 40506, (2)Earth & Environmental Sciences, University of Kentucky, Lexington, KY 40506, (3)Earth and Environmental Sciences, University of Kentucky, 121 Washington Ave., Lexington, KY 40506, (4)Department of Geology, University of Illinois at Urbana-Champaign, 3081 Natural History Building, 1301 W. Green St., Urbana, IL 61801, (5)Department of Geosciences, Colorado State University, 400 University Ave., Fort Collins, CO 80521-1482

Removal of mountain topography is classically attributed to surface processes such as river and glacial erosion and land sliding and because of this, complete removal of old mountain belts like the Appalachians usually takes >10-100 million years or more. Here, we demonstrate that mountain belts can be completely and rapidly (<2 Myr) removed by a migrating hotspot. In western North America, multiple mountain belts, including the Teton Range, are apparently truncated by the relatively low relief track of the Yellowstone hotspot, leading to a previously untested hypothesis that topography along the track has been erased. In the case of the Teton Range, multiple emerging datasets obtained by our group over the last three summers indicate that the paleo-Teton fault extends much further north than the topographic expression of the present-day range (~155-210 km v. 65 km), extending across the modern-day Yellowstone hotspot track. These analyses also indicate that the majority of slip and the associated footwall mountain range growth had accumulated prior to Yellowstone encroachment at ~2 Ma, leading us to interpret that the hotpot removed the northern extension of the paleo-Teton Range. This prediction is corroborated by new seismic reflection data from northern Jackson Lake that indicates that the main Teton fault scarp recognized along the range front links with multiple previously recognized active fault segments north of Jackson Lake. Linkage of disparate fault segments into a single continuous fault zone results in a minimum active northern extension of ~15 km (25%) for the main Teton fault. We propose that eastward migration of the Yellowstone hotspot relative to stable North America resulted in collapse of 600-1600 km3 of paleo-Teton mountain topography following three supercaldera (VEI 8) eruptions from 2.0 Ma to 600 ka. If correct, this cataclysmic collapse of mountain belts would represent one of the fastest topography removal mechanisms in the world.