The stratigraphic signature of the late Cenozoic Antarctic Ice Sheets in the Ross Embayment

Late Oligocene obliquity-paced contourite sedimentation in the Wilkes Land margin of East Antarctica: implications for paleoceanographic and ice sheet configurations

“…Warm Pliocene seasonal temperatures up to 6°C warmer than today during interglacials and prolonged Pliocene warm intervals have been reported in the Ross Sea 535 (e.g., Naish et al, 2009;McKay et al, 2012) and other locations around Antarctica (Whitehead and Bohaty, 2003;Whitehead et al, 2005;Escutia et al, 2009;Bart and Iwai, 2012). Contrary to what we observe in our late Oligocene record, during the warm Pliocene abundant IRD were delivered to adjacent continental rise sites (Escutia et al, 2011;Patterson et al, 2014).…”

“…Although the data is somewhat noisy due to gaps in our record, it clearly shows that the glacial-interglacial cyclicity (every 2 m or 41 kyr) discussed above has a persistent obliquity pacing throughout the studied late Oligocene (Patterson et al, 2014). In the Ross Sea, cyclicity in sediments collected by the CRP from the late Oligocene, the late Miocene and the early warm Pliocene period was also paced by obliquity (Naish et al, 2001;McKay et al, 2009;Naish et al, 2009). Similar orbital variability in the deep-water circulation patterns have also been inferred to have occurred with the growth of the EAIS during the middle Miocene between 15.5 to 12.5 Ma (Hall et al, 2003).…”

“…These studies have shown that early Pliocene Southern Ocean surface waters were much warmer (i.e., between 2.5-> 4 ºC) than present and that the summer sea ice cover was greatly reduced, or even absent (Bohaty and Hardwood, 1998;Whitehead and Bohaty, 2003;Escutia et al, 2009;Cook et al, 2013). They also record the periodic collapse of both the WAIS and EAIS marine-based margins (Naish et al, 2009;Pollard and DeConto, 2009;Cook et al, 2013;Reinardy et al, 2015;DeConto and 85 Pollard, 2016). Foster and Rohling (2013) demonstrated a sigmoidal relationship between eustatic sealevel and atmospheric CO 2 levels whereby sea levels stabilise at ~22+/-12m above present day level between about 400 ppm and 650 ppm, suggesting loss of the Greenland Ice Sheet and the marine-based West Antarctic Ice Sheet (+11 m s.l.e.).…”

Diatom evidence for the onset of Pliocene cooling from AND-1B, McMurdo Sound, Antarctica

“…Each diatomite within this oscillating record has distinctive assemblage characteristics ; although one unit appears to preserve a continuous interval of open ocean conditions from 3.6 to 3.4 Ma, most are interpreted to preserve the interglacial interval of a single 40 kyr glacial/interglacial cycle Winter et al, 2010;Konfirst et al, 2011;McKay et al, 2012). The loss of additional interglacial intervals by subsequent glacial advance is also identified by the presence of glacial surfaces of erosion (GSEs) that truncate some diamictites (Krissek et al, 2007;McKay et al, 2009). In all, the AND-1B core preserves evidence of nearly 60 oscillations of ice advance and retreat ; thirty-eight of these cycles in the upper 600 m of the core record oscillations during the past 5 Myr.…”

“…1). The drillsite is located beneath a floating portion of the McMurdo Ice Shelf (the northwestern portion of the Ross Ice Shelf) (Falconer et al, 2007) on the western margin of the Victoria Land Basin within the Terror Rift (Naish et al, 2007a;McKay et al, 2009). Ice shelf thickness at the AND-1B drillsite was ~82 m during coring, and the core was collected from a water depth of ~917 m, reflecting the local influence of volcanic load-induced subsidence (Falconer et al, 2007;Naish et al, 2007a).…”