A seismic proxy identifying the transition to an ice sheet polar regime from the sedimentary sequence on the George V Land continental margin (Antarctica)

Based on the integrated analyses of seismic and borehole data from the Antarctic continental shelf and rise in the offshore area of Wilkes Subglacial Basin, we recognize two major turning points in the evolution of the East Antarctic Ice Sheet: in the early Miocene and middle Pliocene, defined by the establishment and deactivation of a noticeable channel-levee system on the continental rise. Our observation supports the earlier hypothesis that ice volume increased nonlinearly with climate before and during the Miocene Climatic Optimum (17–14.8 Ma), the warmest period of the Neogene, as a result of high snowfall under humid climatic conditions, with high moisture supply onto a more terrestrial landmass, prior to extensive erosion and overdeepening of Antarctica's continental shelves. The deactivation of the channel-levee system, evidenced by the progressive filling of the channels on the 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 represents the transition to the present polar regime. The late Miocene,and the early to middle Pliocene are also characterized by a particular high-amplitude seismic facies that is the signature of alternating terrigenous and diatom-rich layers, representing glacial and interglacial periods. This facies characterizes the upper part of the channel system and may represent a potential significant environmental and stratigraphic marker, elsewhere along the Antarctic continental margin.