Multi-scale analyses of subglacial and glaciomarine deposits from the Ross Sea continental shelf, Antarctica

Abstract

AbstractPiston cores collected from the Ross Sea continental shelf, Antarctica, were studied as part of a multi-scale analysis of glacial and glaciomarine stratigraphy and sedimentology. The objective of these analyses was to differentiate glaciomarine sediments from subglacially deformed tills. Results from analyses of microstructures, lithofacies and seafloor morphology indicate that glaciomarine and subglacially deformed sediments can be clearly distinguished and further characterized by variations in textural parameters. Overcompaction, as well as presence of stratification in sediments, are not considered critical criteria for distinguishing subglacial from glaciomarine deposits. Trough-shaped morphologies and fluted terrain strongly correlate with S-C and S-C-C- type shear-zone microstructures and indicate that subglacial deformation is an important process in these areas, confirming the presence of grounded ice on the shelf during formation of these landforms and deposits. Flat, smooth topographies, as well as (low-angle) slope environments, correspond to microfabrics which lack microscopic shear-zone geometries and contain dropstones, angular-sediment clasts, large-shell fragments and slight sorting in sandy layers, which imply ice-shelf or open-water conditions present during deposition.