Deglaciation and postglacial environmental changes in the Teton Mountain Range recorded at Jenny Lake, Grand Teton National Park, WY

Abstract

Sediments contained in lake basins positioned along the eastern front of the Teton Mountain Range preserve a continuous and datable record of deglaciation and postglacial environmental conditions. Here, we develop a multiproxy glacier and paleoenvironmental record using a combination of seismic reflection data and multiple sediment cores recovered from Jenny Lake and other nearby lakes. Age control of Teton lake sediments is established primarily through radiocarbon dating and supported by the presence of two prominent rhyolitic tephra deposits that are geochemically correlated to the widespread Mazama (∼7.6 ka) and Glacier Peak (∼13.6 ka) tephra layers. Multiple glacier and climate indicators, including sediment accumulation rate, bulk density, clastic sediment concentration and flux, organic matter (concentration, flux, δ13C, δ15N, and C/N ratios), and biogenic silica, track changes in environmental conditions and landscape development. Sediment accumulation at Jenny Lake began centuries prior to 13.8 ka and cores from three lakes demonstrate that Teton glacier extents were greatly reduced by this time. Persistent ice retreat in Cascade Canyon was slowed by an interval of small glacier activity between ∼13.5 and 11.5 ka, prior to the end of glacial lacustrine sedimentation ∼11.5 ka. The transition to non-glacial sediments marks the onset of Holocene conditions at Jenny Lake and reflects a shift toward warmer summers, increased vegetation cover, and landscape stability in the Tetons. We discuss the Teton lake sediment records within the context of other regional studies in an effort to construct a comprehensive overview of deglaciation and postglacial environmental conditions at Grand Teton National Park.