It lies north of the oceanographic Subtropical Front. Site 1168 was planned to penetrate marine rift to open margin sediments deposited from the Eocene onwards as Australia moved northward from Antarctica. Initially the site was at the far eastern end of the restricted Australo-Antarctic Gulf and separated from the Pacific Ocean by the Tasmanian land bridge. Plate movements and related margin subsidence led to its Neogene location in open water facing a broad Southern Ocean. Seismic profiles suggest that the site was subject to downslope sediment movement to the northwest in the Paleogene, but was protected from downslope movement from the east in much of the Neogene by the upslope high.
Younger sequences are poorly parallel-bedded and almost transparent seismically.
A bridge prevented running the GHMT-Sonic to the base of the cored interval, and we chose not to run the FMS because of the poor hole conditions. Biostratigraphy indicates no major time breaks. Subunit IA is light greenish gray foraminifer-bearing nannofossil ooze with minor calcareous turbidite sands, and Subunit IB is white nannofossil ooze. Calcareous microfossils are abundant and little altered, benthic foraminifers are always present, dinoflagellate cysts are absent only in the middle Miocene, and radiolarians and diatoms are common in the late Miocene. Deposition was in middle bathyal depths in well oxygenated bottom waters.