Sediment lithofacies, processes and sedimentary models in the Central Bransfield Basin, Antarctic Peninsula, since the Last Glacial Maximum

Abstract

This work provides a regional perspective on the links between glacial, glacimarine and marine sedimentary processes occurring since the Last Glacial Maximum along the Central Bransfield Basin (Antarctic Peninsula), from shallow to deep areas, by combining information provided by gravity cores from shelf to deep basin settings, swath bathymetry and high-resolution reflection seismic and sub-bottom (TOPAS) profiles. Seven lithofacies have been identified. Their textural, compositional and X-radiographic characteristics, as well as their spatial distribution allow the differentiation of two stages of deposition, involving distinct sedimentary processes. The Last Glacial Maximum was characterised by subglacial deformation by the Antarctic Peninsula Ice Sheet as it reached its most extended position on the distal mid-slope platforms of the Central Bransfield Basin. Proglacial debris flows occurred on the external edges of the mid-slope platforms and lower slope. Since the last deglaciation, glacimarine (proglacial debris flows, glacimarine proglacial processes and turbid glacial meltwater) and open-marine sedimentary processes (turbidity currents, sliding and contour current activity) have predominated in the Central Bransfield Basin. Glacial cyclicity is the main factor controlling the sedimentary processes in the basin, but several secondary factors, including physiography, sediment entry points and oceanography, have been identified as local controls on the sediment distribution. The unusual physiography of the Central Bransfield Basin, where slope platforms form wide flat surfaces seaward from glacial troughs, is a key factor in the widespread occurrence of glacial and glacimarine processes on the entire continental margin.