Classically held mechanisms for removing mountain topography (e.g., erosion and gravitational collapse) require 10-100 Myr or more to completely remove tectonically generated relief. Here, we propose that mountain ranges can be completely and rapidly (< 2 Myr) removed by a migrating hotspot. In western North America, multiple mountain ranges, including the Teton Range, terminate at the boundary with the relatively low relief track of the Yellowstone hotspot. This abrupt transition leads to a previously untested hypothesis that preexisting mountainous topography along the track has been erased. We integrate thermochronologic data collected from the footwall of the Teton fault with flexural-kinematic modeling and length-displacement scaling to show that the paleo-Teton fault and associated Teton Range was much longer (min. original length 190-210 km) than the present topographic expression of the range front (~65 km) and extended across the modern-day Yellowstone hotspot track. These analyses also indicate that the majority of fault displacement (min. 11.4-12.6 km) and the associated footwall mountain range growth had accumulated prior to Yellowstone encroachment at ~2 Ma, leading us to interpret that eastward migration of the Yellowstone hotspot relative to stable North America led to removal of the paleo-Teton mountain topography via posteruptive collapse of the range following multiple supercaldera (VEI 8) eruptions from 2.0 Ma to 600 ka and/or an isostatic collapse response, similar to ranges north of the Snake River plain. While this extremely rapid removal of mountain ranges and adjoining basins is probably relatively infrequent in the geologic record, it has important implications for continental physiography and topography over very short time spans.
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This work was supported by a UW-NPS seed grant and NSF-EAR 1932808; GSA Student Research Grants to RMH, MLS, and ALH; and an AAPG Student Grant-In-Aid to MLS. The Overcash Field Fund at UK supported undergraduate student participation in fieldwork. WRG acknowledges NSF-EAR 1735788, which supports analytical facilities used for this work.
Thigpen, J. Ryan; Brown, Summer J.; Helfrich, Autumn L.; Hoar, Rachel; McGlue, Michael M.; Woolery, Edward W.; Guenthner, William R.; Swallom, Meredith L.; Dixon, Spencer; and Gallen, Sean, "Removal of the Northern Paleo-Teton Range along the Yellowstone Hotspot Track" (2021). Earth and Environmental Sciences Faculty Publications. 27.