The spatial pattern and morphometry of bedforms and their relationship to sediment thickness have been analysed in the Marguerite Bay Palaeo-ice stream Trough, western Antarctic Peninsula. Over 17 000 glacial landforms were measured from geophysical datasets, and sediment thickness maps were generated from acoustic sub-bottom profiler data. These analyses reveal a complex bedform pattern characterised by considerable spatial diversity, influenced heavily by the underlying substrate. The variability in length and density of mega-scale lineations indicates an evolving bedform signature, whereby landforms are preserved at different stages of maturity. Lineation generation and attenuation is associated with regions of thick, soft till where deformation was likely to be the greatest. The distribution of soft till and the localised extent of grounding-zone wedges (GZWs) indicate a dynamic sedimentary system characterised by considerable spatio-temporal variability in sediment erosion, transport and deposition. Formation of GZWs on the outer shelf of Marguerite Trough, within the error range of the radiocarbon dates, requires large sediment fluxes (upwards of 1000 m(3) a(-1) (m grounding line width)(-1)), and a >1 m thick mobile till layer, or rapid basal sliding velocities (upwards of 6 km a(-1)).
This work was funded by Natural Environmental Research Council (NERC) UK standard grants NE/G015430/1 and NE/G018677/1. Jamieson was supported by NERC Fellowship NE/J018333/1 and Spagnolo was supported by NERC new investigator grant NE/J004766/1. Underlying data are available by request to Livingstone. This research would not have been possible without the hard work of scientists and crew during research cruises JR59, JR71, JR157 and NBP0201. We thank two anonymous reviewers for their comments, which helped to improve the manuscript. We also thank Jeremy Ely for his comments on an earlier draft.
- glacial lineations
- grounding-zone wedges
- ice stream
- subglacial bedforms