IODP Expedition 318: From Greenhouse to Icehouse at the Wilkes Land Antarctic Margin

Abstract

Integrated Ocean Drilling Program (IODP) Expedition 318, Wilkes Land Glacial History, drilled a transect of sites across the Wilkes Land margin of Antarctica to provide a long-term record of the sedimentary archives of Cenozoic Antarctic glaciation and its intimate relationships with global climatic and oceanographic change. The Wilkes Land drilling program was undertaken to constrain the age, nature, and paleoenvironment of the previously only seismicallyinferred glacial sequences. The expedition (January–March 2010) recovered ~2000 meters of high-quality middle Eocene–Holocene sediments from water depths between 400 m and 4000 m at four sites on the Wilkes Land rise (U1355, U1356, U1359, and U1361) and three sites on the Wilkes Land shelf (U1357, U1358, and U1360). These records span ~53 million years of Antarctic history, and the various seismic units (WL-S4–WL-S9) have been successfully dated. The cores reveal the history of the Wilkes Land Antarctic margin from an ice-free “greenhouse” Antarctica, to the first cooling, to the onset and erosional consequences of the first glaciation and the subsequentdynamics of the waxing and waning ice sheets, all the way to thick, unprecedented “tree ring style” records with seasonal resolution of the last deglaciation that began ~10,000 y ago. The cores also reveal details of the tectonic history of the Australo-Antarctic Gulf from 53 Ma, portraying the onset of the second phase of rifting between Australia and Antarctica, to ever-subsiding margins and deepening,to the present continental and ever-widening ocean/continent configuration

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

“…1). Overall recovery was 35% with sediments dated between the early Eocene and Pliocene, but several intervals provide good stratigraphic control (Escutia et al, 2011;Tauxe et al, 150 2012). The Oligocene section was recovered between 895 and 434 mbsf, Cores U1356-95R-3 83 cm to U1356-46R.…”

“…Our study focuses on the relatively high-recovery (78.2 %) interval within the late Oligocene, which spans from 689.4 to 641.4 mbsf (Cores U1356-72R to -68R). The sediments from this interval are part of shipboard lithostratigraphic Unit V, which is characterized by light greenish-grey, strongly bioturbated claystones and micritic limestones interbedded with dark brown, sparsely 155 bioturbated, parallel-and ripple-laminated claystones with minor cross-laminated interbeds (Escutia et al, 2011). The bioturbated and calcareous claystones and limestones were broadly interpreted to represent pelagic sedimentation superimposed on the background hemipelagic sedimentary input (Escutia et al, 2011).…”

“…Site U1356 (63º 18.6138'S, 135º 59.9376'E) is located at 3992 m water depth in front of the glaciated margin of the eastern Wilkes Land Coast of East Antarctica, and penetrated 1006 meters into the flank of a levee deposit in the transition between the lower continental rise and the abyssal plain (Escutia et al, 2011;Fig. 1).…”

“…The sediments from this interval are part of shipboard lithostratigraphic Unit V, which is characterized by light greenish-grey, strongly bioturbated claystones and micritic limestones interbedded with dark brown, sparsely 155 bioturbated, parallel-and ripple-laminated claystones with minor cross-laminated interbeds (Escutia et al, 2011). The bioturbated and calcareous claystones and limestones were broadly interpreted to represent pelagic sedimentation superimposed on the background hemipelagic sedimentary input (Escutia et al, 2011). The laminated claystones and ripple cross-laminated sandstones were interpreted to likely result from variations in bottom current strength and fine-grained terrigenous supply (Escutia 160 et al, 2011).…”

“…The age model for Site U1356 was established on the basis of the magnetostratigraphic datums constrained by marine diatom, radiolaria, calcareous nannoplankton and dinocyst biostratigraphic control (Escutia et al, 2011;Tauxe et al, 2012;Bijl et al, in press …”