LAKE SEDIMENT RECORDS OF DEGLACIATION AND POSTGLACIAL TECTONIC ACTIVITY IN THE TETON RANGE, WY

The impressive geomorphology of the Teton mountain range forms the centerpiece of Grand Teton National Park and showcases a legacy of tectonic and glacial processes that have attracted scientific research for decades. Active uplift of the Tetons is associated with the Teton fault, a major eastward-dipping normal fault that extends for ~70 km along the base of the mountains. Well-preserved fault scarps up to ~30-m-tall displace glacier deposits from the most recent (Pinedale) glaciation and provide evidence for high fault activity since deglaciation ~15 ka. Previous and ongoing efforts to excavate trenches across the fault have been successful in identifying the timing and magnitude of past rupture events. However, the postglacial paleoseismic record of the Teton fault remains incomplete. Our recent findings indicate that sediments contained in a series of glacial lakes positioned along the fault trace contain a datable archive of slope failure events such as landslides, inflow delta failures, and subaqueous gravity flows, that were likely triggered by past seismic activity. These lakes also preserve a record of alpine glacier recession at the end of the Pinedale glaciation. We combine multibeam sonar bathymetry and seismic reflection images of Jenny Lake with sediment cores taken from Jenny Lake and other nearby lakes to identify glacial and tectonic landforms and to characterize infill stratigraphy and slide deposits. This presentation will place emphasis on lake sedimentary signatures of past seismic activity, methods of integrating geophysical tools with lake sediment core data, and the temporal relationship between regional deglaciation and paleoseismicity in the Tetons.