APPLICATIONS OF LOW-TEMPERATURE THERMOCHRONOLOGY TO GLACIAL EROSION AND BEDROCK EXHUMATION IN THE CENTRAL TRANSANTARCTIC MOUNTAINS

The Transantarctic Mountains (TAM) were one of the nucleation sites of the Antarctic ice sheet at ~34 Ma and have some of the highest tip-to-trough relief of any mountain range in the world. In addition to constraining the history of the ice sheet itself and the unique uplift history of the region through records of bedrock exhumation, thermochronology can also provide insight into the initial subglacial topography beneath this section of the East Antarctic ice sheet. A period of Cretaceous TAM uplift along an extensional rift flank above the West Antarctic rift basin and an interval of increased glacial incision and subsequent isostatic peak uplift in the Oligocene have been proposed. The timing and tectonic details of these events, however, as well as East Antarctic glacial history during the Miocene and Pliocene, are still very much debated. In this study, we analyze apatite grains from low-elevation granite and sandstone samples bordering the central Transantarctic Mountains with (U-Th)/He thermochronology to determine the time at which they passed through the upper several kilometers of Earth’s crust (corresponding to the ~60 °C geotherm), thereby constraining timing of both glacial incision and associated isostatic uplift. Results include ages from along the Shackleton Glacier of primarily between 50 and 95 Ma, displaying significant age scatter between samples and a major cooling event aligned with Cretaceous uplift and related erosion at ~95 Ma, as well as a smaller cooling pulse circa 55 Ma. As no ages younger than ~34 Ma were recorded by the upper Shackleton Glacier samples, we infer that glacial erosion in this area was not extensive enough to excavate younger cooling ages, though young ages at other sites reveal dynamic ice sheet behavior nearby. Obtaining evidence of more recent cooling events and developing a more detailed thermal profile of the uppermost crust in this region improves our understanding of the complex responses of these East Antarctic outlet glaciers to past warmth.