Changes in Glacial Flow Patterns and Provenance of the Mid-Miocene in the Friis Hills and Olympus Range, McMurdo Dry Valleys, Antarctica

The Friis Hills and the Olympus Range are two regions located in the McMurdo Dry Valleys of Antarctica that serve as a terrestrial archive of the East Antarctic Ice Sheet during the early to mid-Miocene. The Friis Hills are a 1-km-high inselberg that provides notable geological evidence of past glacial deposits and ice flow patterns. Previous work by Lewis and Ashworth (2015) found three distinct glacial deposits, Friis I, Friis II and the Cavendish drift. These were found to be deposited from alpine glaciers flowing SW, SE, and outlet glaciers flowing E, respectively. The three units were differentiated by methods of sedimentological and lithological characteristics to determine ice flow direction, and 40Ar/39Ar isotope analysis on ash deposits provided age-dating. The Olympus Range is a series of cirques that sit approximately 30 km north of the Friis Hills and provides substantial evidence on the permanent local thermal transition between 14.11 and 13.94 Ma where the environment shifted from wet-based glaciers to cold-based glaciers. Lewis et al. (2007) similarly used methods of lithological characteristics and 40Ar/39Ar isotopes on the Circe Till and the Dido Drift deposits to recognise and age-constrain this shift and further investigate the response of the ice sheet to the thermal cooling. This project aims to build on that work with the specific goals of distinguishing changes in glacial flow patterns, changes in provenance over time, and search for evidence of the mid-Miocene overriding event. This will be done by processing glacial deposits from both the Friis Hills and the Olympus Range with zircon dating, geochemical, and grain size analysis. Detrital zircon dating can provide a unique age distribution for each unit which acts as a geochemical fingerprint that allows us to identify different source areas. 16 samples from the Friis Hills and 7 samples from the Olympus Range have been processed for zircon dating through U-Pb isotope ages using the LA-ICP-MS. 7 samples from the Friis Hills have been analysed for bulk geochemistry using the Niton XRF Analyzer and grain size using the Malvern Mastersizer 3000. These analyses will help attain a better understanding of the provenance of the Friis Hills and the Olympus Range which contributes to our overall knowledge on ice sheet behaviour in response to climactic events.