Introduction

Abstract

Understanding Earth's climatic history has lead researchers to explore the glacial history of Antarctica and its role in the Earth's climate system. Scientists have used the information recorded both on the continent and from the surrounding marine sediments. Attention to the deep sea record has focused on the use of proxy indicators such as ice-rafted detritus, sedimentological variations, stable-isotope records and changes in faunal and floral assemblages to identify fluctuating ice sheets and changes in continental ice volume. Dating of specific geological events has relied on microfossil biostratigraphy with calibration of specific biostratigraphical datums (e.g. first and last occurrences) to polarity stratigraphies. In the absence of polarity records, dating of biostratigraphical events was based on known calibrations and/or stratigraphical successions of specific species from regions other than the Southern Ocean. For example, Miocene diatom events in the Southern Ocean were typically assigned ages based on the known ranges of the species in the North Pacific. The chronological framework, based on imported microfossil datums, was used to calibrate the ages of datums specific to the Southern Ocean, i.e. a process involving secondary correlation. These approaches assumed isochroneity of events between oceans. The biochronological framework in this paper is based on the results of the numerous shipboard and shorebased scientists who completed detailed analyses of the sediments recovered at the 59 Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) Southern Ocean sites (Fig. 1; Table 1). Their contributions have made significant advances in the understanding of species biogeography, evolutionary succession