Chronostratigraphic framework for the IODP Expedition 318 cores from the Wilkes Land Margin: Constraints for paleoceanographic reconstruction

Abstract

1] The Integrated Ocean Drilling Program Expedition 318 to the Wilkes Land margin of Antarctica recovered a sedimentary succession ranging in age from lower Eocene to the Holocene. Excellent stratigraphic control is key to understanding the timing of paleoceanographic events through critical climate intervals. Drill sites recovered the lower and middle Eocene, nearly the entire Oligocene, the Miocene from about 17 Ma, the entire Pliocene and much of the Pleistocene. The paleomagnetic properties are generally suitable for magnetostratigraphic interpretation, with well-behaved demagnetization diagrams, uniform distribution of declinations, and a clear separation into two inclination modes. Although the sequences were discontinuously recovered with many gaps due to coring, and there are hiatuses from sedimentary and tectonic processes, the magnetostratigraphic patterns are in general readily interpretable. Our interpretations are integrated with the diatom, radiolarian, calcareous nannofossils and dinoflagellate cyst (dinocyst) biostratigraphy. The magnetostratigraphy significantly improves the resolution of the chronostratigraphy, particularly in intervals with poor biostratigraphic control. However, Southern Ocean records with reliable magnetostratigraphies are notably scarce, and the data reported here provide an opportunity for improved calibration of the

Orbital forcing of the East Antarctic ice sheet during the Pliocene and Early Pleistocene

“…The geometry of strata on the Wilkes Land continental shelf indicate that the EAIS expanded towards the continental shelf edge during glacial maxima in the Pliocene 12 , indicating most Antarctic ice-volume variance at this time was growth and retreat of the marine-based ice sheets (Supplementary Fig. 1).…”

“…Steeply dipping, seaward prograding wedge sediments are evident in seismic reflection profiles across the continental shelf and extend onto the upper continental slope above seismic unconformity WL-U8 (∼4.2 Ma; Supplementary Fig. 1; refs [12][13][14]. The geometry of these strata is characteristic of grounding zone deposition by repetitive advances of a marine-based ice sheet to the shelf edge during glacial periods 13 .…”

“…2). Our age model is based on a magnetic polarity stratigraphy constrained by biostratigraphy 12 and is not orbitally tuned ( Supplementary Fig. 5).…”

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

“…440 The depositional setting on the continental rise was however different during the late Oligocene. The stratigraphic evolution of the region testifies the progradation of the continental shelf taking place after continental ice sheet build-up during the Eocene-Oligocene Transition (EOT, 34 Ma) (Eittreim et al, 1995;Escutia et al, 1997;Escutia et al, 2005), which resulted in: 1) seismic and sedimentary facies becoming more proximal up-section (Hayes and Frakes, 1975;Escutia et el., 2000;Escutia et al, 2005;445 Escutia et al, 2014), and 2) high sedimentation rates during the Oligocene (Escutia et al, 2011;Tauxe et al, 2012). In this context, the late Oligocene sediments from Site U1356 record distal continental rise deposition in an incipient/low-relief levee of a channel-levee complex.…”

“…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 …”