Late Quaternary sediment facies in Prydz Bay, East Antarctica and their relationship to glacial advance onto the continental shelf

Abstract

A marine survey in Prydz Bay, provides an unparalleled view of glacigenic and marine sedimentation across Prydz Channel and Amery Depression during the Late Quaternary. Gravity cores and a suite of eight radiocarbon dates indicate that the Late Wisconsin Glacial Maximum (LGM) was associated with grounding of a palaeo-ice shelf along the periphery of Prydz Channel. Deposition in front of the grounding line was dominated by ice-rafting. A granulated facies, containing angular clay and diamicton clasts, was produced by a combination of regelation freezing, near to the grounding line, and remelting of this basal debris in the sub-ice shelfsetting. Beneath these LGM marine deposits lie two key beds of diatom ooze that are distinct in size sorting and Pliocene diatoms. These "interstadial" units can be traced across most ofthe Prydz Channel, and are underlain by additional glacial marine units. Debris related to the Lambert Deep is distinct from detritus from eastern Prydz Bay and deposition ofthese two sources within the channel oscillated during the LGM. We suggest that coastal drainage systems contributed to a limited glaciation of the shelf during the LGM, rather than direct outflow via the Lambert /Amery system. It is proposed that shelf-wide glaciation is related to the duration ofglacial sea level lowstands rather than the absolute magnitude of eustatic fall during such episodes.

The sedimentary legacy of a palaeo-ice stream on the shelf of the southern Bellingshausen Sea: Clues to West Antarctic glacial history during the Late Quaternary

“…Our interpretations are largely consistent with published facies classifications from elsewhere on the Antarctic shelf (e.g. Kurtz and Anderson, 1979;Anderson et al, 1980;Wright and Anderson, 1982;Licht et al, 1996Licht et al, , 1998Licht et al, , 1999Domack et al, 1998Domack et al, , 1999Domack et al, , 2005Anderson, 1999;Pudsey and Evans, 2001;Wellner et al, 2001;Evans and Pudsey, 2002; We interpret muddy diamictons of the lower lithological unit, which are characterised by medium to high shear strength values, low CaCO 3 contents and only minor fluctuations in MS, water content, WBD and grain-size composition, as subglacial soft tills (ST) deposited at the base of the ice stream that had advanced through Belgica Trough (Table 2, Fig. 2).…”

“…Variability in sediment supply and current-induced sorting is reflected in the muddy diamictons of our cores by the variability of physical properties and grain-size composition (cf. Domack et al, 1998Domack et al, , 1999Licht et al, 1999;Evans and Pudsey, 2002;Hillenbrand et al, 2005). In the upper muddy diamicton of core GC374 we observe a stratified interval (Fig.…”

“…With the exception of site GC359, the down-core variability of the d 13 C org values at each individual core site is 1.1& (Table 1), which is comparable or less than at core sites from other parts of the Antarctic shelf (e.g. Harden et al, 1992;Domack et al, 1998Domack et al, , 1999Domack et al, , 2001Licht and Andrews, 2002;Ó Cofaigh et al, 2005a;Pudsey et al, 2006;Hemer et al, 2007;McKay et al, 2008;Hillenbrand et al, 2010). The d 13 C org composition of marine particulate organic substance typically ranges from À18& to À27& (e.g.…”

On the origin of Antarctic marine benthic community structure

“…The advance of grounded ice masses across the shelf would have erased the benthic fauna and is, therefore, considered to be the main limiting factor in the survival of marine shallow-water benthos [31] (Box 2, Figure Ib). However, marine geological evidence also shows that grounded ice did not advance to the shelf edge on some parts of the East Antarctic shelf, such as the western Ross Sea [32,33], Prydz Bay [34] and George Vth Land [35] (Box 2; Figure 1). Consequently, such shelf areas were assumed to act as shelters, where benthic organisms might have survived during glacial periods [36].…”

“…Consequently, such shelf areas were assumed to act as shelters, where benthic organisms might have survived during glacial periods [36]. This is, however, unlikely, given that these shelf regions were likely to be either covered by ice shelves [33,34] or subject to intense iceberg scouring [35].…”