During ODP Leg 178, eight holes were drilled at three sites (1095, 1096, and 1101) on the continental rise and ten holes at four sites (1097, 1100, 1102, and 1103) on the continental shelf, respectively, of the western Antarctic Peninsula (Barker, Camerlenghi, Acton, et al., 1999).
Excellent magnetostratigraphic and generally good biostratigraphic control is present for the past ~9.6 m.y. at Sites 1095, 1096, and 1101 on the sediment drifts. Diatoms and radiolarians offer the best biostratigraphic control for the upper Miocene to middle Pliocene, whereas calcareous nannofossils and planktonic foraminifers are useful in the upper Pliocene to lower Pleistocene section. Leg 178 studies have allowed refinement of the magnetobiochronologic framework for the Cenozoic of the Southern Ocean. Siliceous microfossil stratigraphy from diatoms (Winter and Iwai, Chap. 29, this volume; Iwai, 2000a, 2000b) and radiolarians (Weinheimer in Barker, Camerlenghi, Acton, et al., 1999; Lazarus, Chap. 13, this volume) provides the basis for much of the stratigraphic division of Leg 178 Neogene sediments presented here (Fig. F2). Biostratigraphic control for the early to middle Pleistocene is from calcareous nannofossils (Winter and Wise, Chap. 26, this volume; Kameo in Iwai et al., Chap. 28, this volume).
The paleomagnetic and biostratigraphic data are mostly in excellent agreement for the three continental rise sites. One exception is that there is a systematic shift of the biostratigraphic events from the depth-age curve derived from magnetostratigraphy in the latest Miocene-earliest Pliocene interval at Site 1095. This shift is not easily explainable in our data by processes such as reworking, downcore contamination, taxonomic confusion, or diachroneity of biostratigraphic events. We suggest that the published magnetobiostratigraphic calibration in the Southern Ocean for the late Miocene-earliest Pleistocene time interval had a problem caused by the unusual common hiatus.