SEISMIC REFLECTION PROFILES REVEAL POSSIBLE SUB-LACUSTRINE PALEO-DELTAS IN JACKSON LAKE (WY)

Jackson Lake, located along the foot of the Tetons (WY), is a lacustrine basin that is fed by the Snake River from the north, canyon-confined drainages from the adjacent mountain range in the west, and drainages from the northeast. Today, a dam controls the outflow of Jackson Lake, and concerns exist around the potential for earthquakes and faulting to affect this hydrological system. Jackson Lake is an excellent area to study the influence of tectonic and climatic changes on lacustrine hydrology and sedimentary processes. Seismic reflection data was collected over Jackson Lake in August 2018 during a research class offered at the University of Kentucky. Initial analysis of the seismic data revealed the presence of a discrete sub-lacustrine sedimentary package characterized by high angle reflections (e.g., toplap and downlap) in the vicinity of Sargent’s Bay. The external geometry of this deposit is that of an oblique prograding clinoform, which suggests that it is a paleo-delta that formed during a recent lake level lowstand. This paleo-delta consists of at least two stacked lobes, and its source is the subject of current investigation. The presence of this deposits suggests that tectonic and/or glacial processes along the eastern basin margin may have influenced the paleo-hydrology of Jackson Lake. Future research will examine the distribution of other sub-lacustrine features imaged in the seismic grid that reflect the paleo-hydrology of Jackson Lake, and coring may help further constrain the chronology of deposition.