During Leg 178, cores were obtained from multiple holes at Sites 1095 and 1096, located on a sediment drift on the upper continental rise of the Antarctic Peninsula Pacific margin, mainly by use of the advanced piston corer (APC) at shallow subbottom depths. These two sites were selected to be complementary. Site 1096 lies on the proximal part of Sediment Drift 7, where sedimentation rates were known to be higher and thus where the younger part of the drift section could be sampled in expanded form. At the more distal Site 1095, the older part of the drift is more accessible because the younger part is thinner. The sediment drifts contain a high-resolution record of the glacial state of the adjacent continent. At Site 1095, in ~3842 m water depth, Hole 1095A was cored to 87.3 meters below sea floor (mbsf) with 99.1% recovery, Hole 1095B was cored to 570.2 mbsf (487.2-m cored section) with 79.2% recovery, and Hole 1095D was cored to 84.6 mbsf with 93.3% recovery. At Site 1096, in ~3152 m water depth, Hole 1096A was cored to 140.7 mbsf with 84.2% recovery, Hole 1096B was cored to 260.6 mbsf with 80.5% recovery, and Hole 1096C was cored to 607.7 mbsf (409.9-m cored section) with 84.2% recovery.
The objective of multiple coring, a common Ocean Drilling Program (ODP) practice for paleoenvironmental studies usually involving triple coring, is to obtain a continuous sediment column that allows high-resolution sampling of undisturbed core. Coring depths are offset between holes so that the cores overlap. It is necessary then to produce an optimal "spliced" sediment column, usually aboard ship, to permit informed sampling, by correlating measurements of core physical properties between holes. A common composite depth scale is produced that allows the combination of selected sections of cores from different holes into an optimal spliced column. During Leg 178, not all sites were multiple cored and the main objectives were usually deeper in the drift. Only one site, Site 1098, was fully triple cored (see Acton et al., Chap. 5, this volume).
The effect of multiple coring at shallow subbottom depth at both of the sites reported here was duplication; very rarely were three cores available from which sections for splicing could be chosen. This degree of cover created more coring gaps than would have been likely with triple coring and restricted the choice of section. Some correlations between cores reported here are speculative, and a few are probably wrong; the spliced sections are inevitably less secure than for the usual triple-cored sites. Nevertheless, the greater time available postcruise and the opportunity to consider the available, less-than-perfect data sets at length have resulted in a revised calculation of mean composite depths and creation of spliced sections that are probably an improvement over the shipboard version (Shipboard Scientific Party, 1999b, 1999c).