Sequence stratigraphy of the ANDRILL AND-2A drillcore, Antarctica: A long-term, ice-proximal record of Early to Mid-Miocene climate, sea-level and glacial dynamism

A sedimentological record of early Miocene ice advance and retreat, AND-2A drill hole, McMurdo Sound, Antarctica

“…Smear slides were examined during initial core logging at McMurdo at generally one-meter intervals over the entire core, providing initial estimates of variation in grain size, biogenic material, and volcanic glass Panter et al, 2008). Fielding et al (2011) divided the entire cored succession into 74 high-frequency (fourth or fifth order) glacimarine sequences recording repeated advances and retreats of glaciers into and out of the Victoria Land Basin; these can be resolved into thirteen longer-term, composite sequences (third order; CS1-13), each characterized by one of six sedimentary motifs that comprise distinct assemblages of facies Passchier et al, 2011). These motifs build on the three recognized by McKay et al (2009) in AND-1B and largely represent facies deposited in more ice-distal settings in AND-2A compared to those represented in AND-1B (table 1 of McKay et al [2009]).…”

“…It recovered a 1138.54 m long drill core spanning early Miocene to Pliocene time, though with substantial parts of the early, middle and late Miocene and Plio-Pleistocene record absent due to the presence of erosional unconformities. The facies have been described and interpreted by Passchier et al (2011), and the stratigraphy and sequences have been described by Fielding et al (2008Fielding et al ( , 2011Figs. 2 and 3).…”

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“…Carbonate (e.g., calcareous nannofossils/foraminifers) may also be present in late Pleistocene interglacial sequences (e.g., Escutia, Brinkhuis, Klaus, and the Expedition 318 Scientists, 2011;Scherer et al, 2008;Theissen et al, 2003;Villa et al, 2008). In the lower to middle Miocene, biogenic carbonate is more common in the Southern Ocean and Antarctica's margins ( Figure F5) (Escutia, Brinkhuis, Klaus, and the Expedition 318 Scientists, 2011;Exon, Kennett, Malone, et al, 2001;Fielding et al, 2011;Hayes et al, 1975;Kennett and Barker, 1990;Shevenell et al, 2004), making stable isotope (δ 18 O and δ 13 C), trace element (e.g., Mg/Ca, Li/Ca, U/Ca, Ba/Ca, and B/Ca), and clumped isotope analyses possible, with careful consideration of proxy strengths/weaknesses in a marginal marine setting. (e.g., sea level and temperature) on WAIS stability/instability WAIS collapse events during past warmer-than-present climates may be the consequence of intensified ocean-cryosphere interactions Pollard and DeConto, 2009).…”

“…Major hiatuses are likely to occur in continental shelf sequences, but the existing sediments provide critical snapshots into past interglacial intervals. The timing of major hiatuses will allow us to determine if widespread WAIS advances coincided with major global cooling steps (e.g., Anderson, 1999;Zachos et al, 2001;Bart, 2003;Fielding et al, 2011;Bart et al, 2011).…”

“…Model senstivity of Last Glacial Maximum AIS to changes in sea level (sl) and ocean heat flux (ohf) (Golledge et al 2012) Terrestrial-based AIS extent (modelled) due to changes in topography (after Wilson et al, 2013) C Figure F5. Neogene Ross Sea continental shelf lithofacies interpretations (after McKay et al, 2009;Fielding et al, 2011). GSE = glacial surface of erosion (sharp contacts associated with subglacial deformation features Figure F6.…”