Petrographic signature of the gravel fraction from late Quaternary glacigenic sediments in the Ross Sea (Antarctica): Implications for source terranes and Neogene glacial reconstructions

Abstract

The Ross Embayment is a key region to study the dynamics of the ice sheets during colder and warmer than present climatic conditions, because both the East and West Antarctic Ice sheets shed into the Ross Sea. Numerical modeling and reconstructions of the paleo ice flows during the Last Glacial Maximum show variable contribution of East and West Antarctic Ice sheets based on a variety of proxies. In this study, we present the first petrographic and minero-chemical investigation of the gravel-sized fraction of Last Glacial Maximum subglacial-glacimarine sediments collected with piston cores in a W–E transect across the Ross Sea. The clast petrographic features are compared with outcropping geology to individuate the sediment source regions. The gravel content of the glacigenic diamictite was classified on the basis of petrographic and minero-chemical features, and three main petrofacies were identified. They reflect changes in the basement geology of the source regions, allowing the reconstruction of the paleo ice flow pattern and their comparison with scenarios built up with other datasets. Moreover, the comparison with the Oligocene to Pleistocene glacigenic sediments provided information about the changes of the gravel signature across the Ross Sea and the erosion history of the source regions during Cenozoic.