The shallow-water Eocene siliciclastics are distinguished by a continuous record of abundant organic dinoflagellate cysts and pervasive pollen and spores, which are critical for biostratigraphic subdivision of this interval and provide a richness of paleoenvironmental information. The Paleocene sediments also contain abundant assemblages of organic palynomorphs, but only rare to few calcareous nannofossils. Planktonic foraminifers, radiolarians, and diatoms are absent. Benthic foraminifers, which have provided critical information on benthic environments, are largely present throughout the entire sequence and are noticeably more abundant in the Eocene. This strongly suggests that the driving force for the strike-slip motion, the separation of Australia and Antarctica, no longer affected this part of the STR from that time, accurately defining the age of the onset of seafloor spreading to the south as 55 Ma.
Organic matter is immature through most of the cored interval, with maturity increasing with depth.
However, toward the base of the cored interval organic matter is mature, and gases have a thermogenic signature, although gas quantities are low. The wireline logs were confined to a single complete run of the triple-combo tool in Hole 1171D because of technical and hole stability problems. Logging data appear to be strongly cyclic, especially the Th spectrum of the natural gamma-ray log in the middle Eocene section. Variability in log data also may be recording alternating marine and terrestrial influences. Late Paleocene sediments were deposited in near anoxic conditions in near-shore highly sheltered environments, with resulting high organic carbon content.