Eruptive environment of volcanism on Brabant Island: evidence for thin wet-based ice in northern Antarctic Peninsula during the Late Quaternary

Terrestrial volcanism occurred extensively on Brabant Island, northern Antarctic Peninsula, during the Late Quaternary (< 200 ka; probably entirely Late Pleistocene). Two compositionally distinct volcanic sequences formed three large shield volcanoes. The volcanoes were constructed in association with a < 150 m-thick, non-ice stream glacial cover, although it was likely to be thicker (few hundred metres) where it extended onto the continental shelf. The glacial cover on the volcanoes was probably mainly permeable snow, firn and fractured (crevassed) ice. It was wet-based, erosive and sediment-forming, indicating either a temperate or, perhaps more likely, sub-polar thermal regime, and would have been more extensive than that present today. Such a thin ice sheet would have had a low surface gradient during periods of extension across the continental shelf. This is the first direct evidence for the thickness and thermal regime of the terrestrial ice sheet in the Antarctic Peninsula during any Quaternary period prior to the last glacial maximum.