The site is 80 km southeast of DSDP Site 282, which is located in deeper water and on a structural high. It lies north of the oceanographic Subtropical Front. Site 1168 was planned to penetrate marine rift to open-margin sediments deposited from the Eocene onward 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.
Younger sequences are poorly parallel bedded and almost transparent seismically.
Biostratigraphy indicates no major time breaks. Subunit IA to 45 mbsf and Subunit IB to 260 mbsf. 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 upper Miocene. Deposition was in middle bathyal depths in well-oxygenated bottom waters.