A fault-bounded palaeo-lake basin preserved beneath the Greenland Ice Sheet
Paxman, G.J.G., J. Austermann, and K.J. Tinto, 2021: A fault-bounded palaeo-lake basin preserved beneath the Greenland Ice Sheet. Earth and Planetary Science Letters , vol. 553,116647, https://doi.org/10.1016/j.epsl.2020.116647.
Abstract
Subglacial topography not only exerts strong controls on contemporary ice sheet dynamics, but also provides an important long-term record of landscape evolution pertaining to past glacial and interglacial conditions. In particular, the bed topography beneath the Greenland Ice Sheet bears the signatures of past processes of landscape evolution that record the development of the ice sheet since its inception. Here we present evidence from airborne radio-echo sounding, gravity, and magnetic data for an enclosed palaeo-lake basin situated beneath the ice sheet in northwest Greenland. Geomorphological analysis and hydrological modelling indicate that the basin once hosted a lake with a surface area of up to ∼7,100 km2 and a volume of up to ∼580 km3. The basin and associated topography control the organisation of a preserved palaeo-fluvial channel network, suggesting that the basin pre-dates widespread glaciation in northwest Greenland. We use flexural modelling to show that the morphology of the basin and surrounding topography is consistent with elastic plate flexure driven by mechanical displacement along a normal fault bounding the basin margin. Analysis of gravity and magnetic anomalies indicates that the basin contains a sedimentary infill up to ∼1.2 km thick, which may contain valuable records of past ice sheet extent and environmental conditions in northwest Greenland. We therefore propose that this newly identified palaeo-lake basin may be a promising target for future acquisition of ground-based active source seismic data and potential recovery of subglacial material by sub-ice drilling programs.