The principal objectives of Ocean Drilling Program (ODP) Leg 178 were to examine Cenozoic depositional processes and climate change along the glacially influenced continental margin of the Antarctic Peninsula. The Antarctic Ice Sheet, involved in deep- and bottom-water formation and past eustatic sea level changes, is a major component of the global climate system. Unfortunately, the history of the Antarctic Ice Sheet is only partially known, primarily because it has been inferred from low-latitude proxy data (e.g., oxygen isotopic measurements).
During Leg 178, nine sites were drilled on the Pacific continental margin of the Antarctic Peninsula in three depositional environments (Shipboard Scientific Party, 1999a). These included a transect of the outer continental shelf prograded wedge (Sites 1097, 1100, 1102, and 1103) and sites on two hemipelagic drifts on the continental rise (Sites 1095, 1096, and 1101), as well as two sites (1098 and 1099) on an inner-shelf basin, Palmer Deep (Fig. F1). Here, we focus on two of the continental rise sites (1095 and 1096), drilled and logged to examine the fine-grained sediments of a sediment drift. These sediments, transported from the shelf to the drift by turbidity and bottom currents (e.g., McGinnis and Hayes, 1995; Rebesco et al., 1996, 1997, 1998), contain a complete and high-resolution glacial record from 0 to 10 Ma.
The major objective of this study is to answer the question of whether deposition within the drift was cyclic. We aimed to derive the main cycles from petrophysical measurements made downhole and on cores. These data reflect physical and chemical variability in the sedimentary section, which are likely related to climatic variations. Our study is based on the powerful method of Morlet wavelet transform (Barthes and Mattei, 1997), which allows the time-frequency or depth-wavelength transform of log and core data to deduce reliable paleoclimatic information.