Thermochronologic Constraints on the Formation of the Transantarctic Mountains, Antarctica

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9315831 Fitzgerald This award supports a study of the thermal evolution of the Shackleton Glacier region of the Transantarctic Mountains using fission track and 40Ar/39Ar thermochronology. The goal is to use the thermal history of the rocks (temperature-time data that dates the time of cooling) to infer the timing and rate of uplift and denudation of the region. This information will, in turn, allow constraints on mechanistic models for uplift of the range on the southwestern edge of the Ross Embayment. The first year of the award will be used to analyze rocks from existing collections and to prepare for field work in the second year. The Shackleton Glacier region is the focus of new field work because it represents a substantial crustal block that is between two segments of the Transantarctic Mountains which have already been extensively studied. The sampling strategy is to collect vertical profiles from basement rocks at regular intervals across, and along the length of, the Transantarctic Mountains. This strategy minimizes the potential for complications and ambiguities which can result from unmapped faults in the region and maximizes the potential for a good estimate of the cooling history. This new field work will test the hypothesis that the Transantarctic Mountains is segmented, with each segment having a distinct uplift history. The data on the time of cooling at each of several vertical profiles is basic information on the geologic development of the region. These data will be used to infer the uplift and denudation history for each locality. The geographic patterns that emerge will help to constrain the tectonic evolution of the central Transantarctic Mountains and they will place constraints on a diversity of geologic problems from Gondwana breakup and development of the Ross Embayment to development of the Cenozoic ice sheets of Antarctica. ***