Site 1165 was drilled on Wild Drift, a thick contourite deposit on the continental rise off Prydz Bay, East Antarctica (64°22.77´S, 67°13.14´E; 3537 m water depth) to a total depth of 999.1 meters below seafloor (mbsf) (Fig. F1) (O'Brien, Cooper, Richter, et al., 2001). Terrigenous and hemipelagic sediments of early Miocene-Quaternary age were recovered including a thick section of contourites. Of special interest to several members of the shipboard science party and their colleagues is the uppermost sediment column between 0 and 50 mbsf, which consists of a section of hemipelagic and pelagic Pliocene-Pleistocene sediments. The stability of the Antarctic ice sheets during the Pliocene—particularly the Gauss Chron (C2An; 2.581-3.580 Ma)—was and is the subject of much debate (Robin, 1988; Hodell and Warnke, 1991; Webb and Harwood, 1991; Hambrey and Barrett, 1993; Quilty, 1993, 1996; Kennett and Hodell, 1993; Warnke et al., 1996; Burckle et al., 1996), mainly based on studies in the Ross Sea/Transantarctic Mountains region. There are several competing ideas concerning the size and fluctuations of the Antarctic ice sheets. These range from minimal size to greatly expanded ice volume, from a perennially frozen landscape to one undergoing active modification, from survival of southern beech trees on Antarctica to environments not supporting higher land plants at all, and so on. Lately, there seems to have been some convergence of ideas among some participants in this debate to the effect that expansions of the ice sheet across the continental shelves took place during brief intervals of time (Whitehead et al., 2001; Bart, 2001). On the topic of ice volume reduction and retreat of the grounding line, there is less agreement. It is not our intention to review the entire debate here. The reader is referred to the above publications. A recent description of the problem, from a "conservative" point of view, is provided by Murphy et al. (2002).
For the entire interval of Antarctic cryospheric evolution, the Pliocene, particularly the early late Pliocene (Piacenzian) is probably the interval that is least understood and most widely debated. The reason for this wide range of ideas is the fact that different investigators used completely different proxies as the bases for their interpretations, and it was inherently difficult to reconcile the contrasting evidence provided by these different proxies.
During Leg 188, it became clear that shipboard scientists were positioned on all sides of the debate. We realized that Site 1165 contained a reasonably well preserved (for an Antarctic margin setting) Pliocene record, particularly the Gauss normal polarity chron including the Kaena (C2An.1r; 3.040-3.110 Ma) and Mammoth (C2An.2r; 3.220-3.330 Ma) Subchrons, which are well identified at this site (timescale of Berggren et al., 1995; Shipboard Scientific Party, 2001). This interval is important because it contains the PRISM2 (Middle Pliocene Paleoenvironmental Reconstruction) time slab (3.15-2.85 Ma) described by Dowsett et al. (1999). The global ice volume and, consequently, the sea level stand during this period of past global warmth is important because both Pliocene ice volume and sea level stand may provide an indication of how Earth may respond to future global warming (Dowsett et al., 1999). Because of the importance of this possibility, we organized the "High-Resolution Integrated Stratigraphy Committee" (HiRISC), whose members reflect various nuances of the ongoing Pliocene debate. The goal of this committee is to provide proxy data sets of various parameters throughout this interval that can be used by all investigators in their participation in the Pliocene debate. It is not the aim of the committee to "solve" the Pliocene problem but rather to provide facts that can be used by all as they see fit. Sampling was done at 10-cm intervals (although in places the sampling interval was variable), and most samples were shared by committee members. Other samples were taken where needed near the "main samples."
The proxies that were determined in our various laboratories were the following: magnetostratigraphy and magnetic properties, grain-size distributions (granulometry), near-ultraviolet/visible/near-infrared (NUV/VIS/NIR) spectrophotometry, calcium carbonate content, characteristics of foraminifer, diatom, and radiolarian content, clay-mineral composition, and stable isotopes. In addition to the HiRISC samples, other data sets contained in this report are subsets of much larger data sets. We included these subsets in order to provide the reader with a convenient integrated data set of Pliocene-Pleistocene strata from the East Antarctic continental margin.