Terrestrial Environments of West Antarctica

Over the past 7 Ma, the APIS has always been relatively thin (few hundred metres). It was also wet based and erosive, at least until about 2 Ma ago. There is also evidence for several ice-poor periods (interglacials) preserved in northern volcanic sequences, particularly in latest Miocene and Early Pliocene. A relatively thin ice cover (probably tens of metres) existed in Ellsworth Land, and it may have locally reached a few hundred metres, but is very poorly dated. Although there are numerous large volcanoes in Marie Byrd Land, each potentially preserving important evidence for past glacial conditions, most are essentially undissected and the only eruptive products available for study are subaerial units. They thus yield minimal useful environmental information other than maximum possible elevations for any former ice sheet(s) that may be hypothesized from other evidence. A glacial cover existed in Marie Byrd Land by 9-8 Ma, at least. It was thin (tens of metres) and formed local icecaps on the large volcanoes. It was wet based at the coast but may have been dry-based (polar) inland. A thicker ice sheet (at least several hundred metres) existed by c. 7-6 Ma, but its thermal regime is unknown. There is also evidence for at least one important episode of overriding by an unusually thick ice sheet in Pliocene or younger time (>1.5km thick; <3.5Ma).

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