Paper No. 227-10
Presentation Time: 4:25 PM
THE SEDIMENTARY RECORD OF DEGLACIATION AND POSTGLACIAL TECTONIC ACTIVITY IN THE TETON RANGE FROM LAKES IN GRAND TETON NATIONAL PARK, WY
Climate and tectonic processes influence the geomorphic development of mountain landscapes through the production, transport, and eventual deposition of sediment. Consequently, sedimentary basins positioned alongside mountain ranges can preserve a record of landscape evolution including past tectonic activity and/or climate-mediated processes such as glacier fluctuations. Here we investigate the sediment fill contained in glacial lakes at Grand Teton National Park, WY to characterize the tectonic and glacial history of the adjacent Teton Range. The iconic geomorphology of the Tetons has been attributed to uplift along the Teton fault, a major range-bounding normal fault that extends along the eastern front of the mountains, and to periodic Quaternary glaciations. Well-preserved fault scarps that displace glacier deposits from the most recent (Pinedale) glaciation provide evidence for recent high fault activity. However, the paleoseismic record of the Teton fault remains incomplete. Recent findings indicate that sediments deposited in glacial lakes positioned along the fault contain a continuous and well-dated archive of slope failure events such as landslides, inflow delta failures, and subaqueous gravity flows, that are likely related to past seismic activity. These lakes also preserve a record of alpine glacier recession at the end of the Pinedale glaciation ~15 ka. 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. A particular emphasis is placed on the sedimentary signatures of past seismic activity and methods of integrating geophysical tools with lake sediment core data.