Geological Template of the Thwaites Glacier Catchment

Abstract:

Thwaites Glacier is thinning and retreating today. Its setting, with a reverse slope extending to over two kilometres below sea level, leaves it vulnerable to catastrophic collapse. Current geological knowledge indicates it is underlain by the West Antarctic Rift System. However, the rift structure, timing and distribution of extension, location of any associated sedimentary basins, and presence of a highly magmatic volcanic province are all disputed. These geological factors matter as associated elevated geothermal heat flux and distribution of thick marine sediments all impact on future ice sheet stability. Here we utilise models of new magnetic and gravity data collected as part of the International Thwaites Glacier Collaboration (ITGC) to evaluate the detailed geology up to ~200 km inboard from the glacier grounding line. We show that linear gravity and magnetic highs are present running parallel to the current grounding line. These structures can be well modelled by dense sources with high magnetic susceptibility at or just beneath the ice-sheet bed. We produce a geological sketch map of the sub-ice geology of the Thwaites Glacier using our new data, and expand our interpretation using data from previous surveys. The possible origins of these features in the geodynamic context of an evolving West Antarctic Rift System and their potential impact on ice sheet dynamics are discussed.