The End of Paleogene White River Group Deposition in Wyoming and Nebraska, USA: A Distal Record of the Collapse and Emplacement of the Markagunt Gravity Slide at 23 Ma

The late Paleogene White River Group is a post-Laramide sedimentary succession that occurs within Laramide intermontane basins and atop some basement-cored uplifts. Detrital zircon U-Pb dates of tuffaceous sandstones from the uppermost White River Group in eastern Wyoming and western Nebraska yield a maximum depositional age of 23.07 ± 0.46 Ma, which overlaps the emplacement of the Markagunt Gravity Slide in Utah’s Marysvale Volcanic Field at 23.05 + 0.22/− 0.20 Ma. The Marysvale Volcanic Field (~31–18 Ma) lies at the east margin of the Nevadaplano, a longstanding highland in the Sevier Hinterland later dismembered by basin and range extension. Strata both proximal and distal to the Marysvale Volcanic Field show an increase in Marysvale provenance up to the emplacement of the Markagunt Gravity Slide. After emplacement, distal sediment sourcing of Miocene strata in the Great Plains shifted back to older Paleogene volcanic fields farther west in Nevada. This temporal relationship suggests that the collapse of the Marysvale Volcanic Field associated with the emplacement of the Markagunt Gravity Slide forced drainage reorganization and sediment sourcing during the transition from White River to Arikaree Group sedimentation.