Late Pleistocene glacial chronology and paleoclimate of Big Cottonwood Canyon, Wasatch Range, Utah.

Abstract:

Development of high-resolution glacial chronologies and paleoclimate modeling play a critical role in understanding modern climate variability. The glacial chronology of Big Cottonwood Canyon, Wasatch Range, Utah is poorly understood, and has not been assessed since the early 1900’s. We used a variety of modern techniques to establish new understanding of Late Pleistocene glaciation in Big Cottonwood and other Wasatch Range canyons. An absolute chronology was established through the use of cosmogenic nuclide (beryllium-10) exposure age dating; we processed seventeen samples from moraine boulders, erratics, and striated bedrock throughout Big Cottonwood Canyon. Remote mapping of glacial landforms was completed using 2-meter LiDAR digital elevation models, and all identified landforms later verified and mapped in the field. We then used a coupled energy-mass-balance and ice-flow model to 1. infer ice extents in Big Cottonwood Canyon, incorporating neighboring canyons with well constrained maxima; and 2. explore paleoclimate conditions during the Late Pleistocene necessary to reproduce these ice extents. Results reveal new information regarding the influence of Pleistocene Lake Bonneville on climate and landscape evolution in the Wasatch Range during and following the Last Glacial Maximum.