Can we use seismic facies as a proxy for past ice sheet regimes?

Based on integrated analyses of seismic and borehole data from the Antarctic continental shelf and rise in the offshore area of the Wilkes Subglacial Basin, we identify two major turning points in the evolution of the East Antarctic Ice Sheet: the early Miocene and the middle Pliocene, marked by the establishment and subsequent deactivation of a prominent channel-levee system on the continental rise. Our observations support the hypoth esis that ice volume increased nonlinearly with climate before and during the Miocene Climatic Optimum (17–14.8 Ma), the warmest period of the Neogene, due to high snowfall under humid climatic conditions, with abundant moisture supplied to a more terrestrial landmass, prior to extensive erosion and overdeepening of Antarctica’s continental shelves. The deactivation of the channel-levee system, indicated by the progressive infilling of channels on the continental rise and the deposition of steeply dipping foreset beds at the shelf margin, occurred at about 3.3 Ma, just before the end of the Pliocene Warm Period (4.5–3.0 Ma), and marks the transition to the present polar regime. The late Miocene and the early to middle Pliocene are characterised by a distinctive high amplitude seismic facies, which is the signature of alternating terrigenous and diatom-rich layers, representing glacial and interglacial periods. This facies characterises the upper part of the channel system and may serve as a significant environmental and stratigraphic marker elsewhere along the Antarctic continental margin.