Sediment distribution and sedimentary processes across the Antarctic Wilkes Land margin during the Quaternary

Abstract

The study of existing cores collected across the Wilkes Land margin provides us with a better understanding of the sediment distribution and processes across this margin during the Holocene, and during Pleistocene glacial and interglacial cycles. Holocene depositional rates are high in deep (>1000 m) inner-shelf basins where diatomaceous ooze is deposited at estimated minimum sedimentation rates ranging from 40 to 60 cm/kyr. In the shelf troughs, Holocene sediment has a patchy distribution or is totally absent. This is also the case on the shelf banks due to differential deposition because of the irregular relief of the continental shelf and the erosion and redistribution by bottom currents. Pleistocene interglacial sedimentation is well represented in sediment from the continental rise and is dominated by hemipelagic deposition of massive mud with the highest biogenic content (as indicated by %opal) and with a high abundance of clasts (IRD). During the Pleistocene glacial cycles, diamictons were deposited in the continental-shelf troughs and on the banks. Reworking (e.g., by bottom currents) and remobilization (e.g., gravity flows) of these diamictons is a common process along the shallow continental-shelf banks. On the continental slope and the continental rise, gravity flows are one of the most important sedimentary processes. Sediment from continental-slope cores, with a texture that greatly resembles the diamictons on the shelf, is interpreted to represent either part of a slump block or the start of a debris flow. Downslope, crudely stratified to laminated intervals represent the transition between an end member of a debris flow and a turbidity flow. Some of the laminated intervals in cores from the continental rise represent sediment deposited from a turbidity flow. Ages obtained from cores further support that slumps and gravity flows are dominant processes in this margin, because numerous hiatuses apparently are present in cores from the base of the slope. One of these cores extends into the Miocene. Elsewhere on the continental rise, massive and laminated sediments in cores of similar length record near-continuous Pleistocene sedimentation. r

Glacial ice and atmospheric forcing on the Mertz Glacier Polynya over the past 250 years

“…Variations of Fragilariopsis cylindrus populations and di-unsaturated highly branched isoprenoid (HBI) lipid [HBI:2] abundances characterize spring sea ice occurrence 14,15 , while summer open ocean conditions are inferred from high abundances of open water diatoms 16 (see Methods section). Titanium (Ti) content is used here to infer changes in terrigenous supply to the ocean 17 , thus reflecting the variability of the terrigenous delivery by glacial melting, the dominant process in Antarctic coastal areas at such timescale 18,19 of open water diatoms and Ti during 1740-1760, 1800-1845 and 1880-1915 periods (Fig. 2), therefore indicate the presence of a well-developed polynya characterized by low SIC during the winter, early spring sea ice retreat and long summer season.…”

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

“…Alternations between laminated glacial deposits and hemipelagic deposits have been previously reported to characterize Pleistocene and Pliocene glacial-interglacial continental rise sedimentation, respectively, on this sector of the Wilkes Land margin (Escutia et al, 2003;Patterson et al, 2014).…”

“…Interglacial sedimentation is dominated by hemipelagic deposition with higher opal and biogenic content (Escutia et al, 2003). Erosion and re-deposition of fine-grained sediment by bottom contour currents has also been reported as another important process during Pleistocene interglacials (Escutia et al, 2002;Escutia et al, 2003).…”

Chapter 5 Cenozoic Climate History from Seismic Reflection and Drilling Studies on the Antarctic Continental Margin

“…The oldest sediment has been dated as late Miocene in age, indicating that gravity flows have been a dominant slope process since at least this time (Escutia et al, 2003). Fig.…”

“…WL-1) formed during the Cretaceous separation of Australia and Antarctica (Cande and Mutter, 1982;Veevers, 1987;Sayers et al, 2001;Colwell et al, 2006;Leitchenkov et al, 2007;O'Brien and Stagg, 2007). The stratigraphy of the margin is known mainly from the seismic stratigraphic interpretation of numerous MCS surveys (Sato et al, 1984;Wanneson et al, 1985;Tsumuraya et al, 1985;Eittreim and Hampton, 1987;Ishihara et al, 1996;Tanahashi et al, 1997;Brancolini and Harris, 2000;Stagg et al, 2004a, b); complemented by surface sediment cores (Domack et al, 1980;Domack, 1982;Tsumuraya et al, 1985;Hampton et al, 1987;Ishihara et al, 1996;Tanahashi et al, 1997;Brancolini and Harris, 2000;Leventer et al, 2001;Escutia et al, 2003;Michel et al, 2006); and limited deep geological sampling recovery at DSDP Sites 268 and 269 . The best-surveyed area is the eastern Wilkes Land margin (EWL) from the Ade´lie Coast to George V Land.…”