Texas A&M University, United States

Integrated Ocean Drilling Program (IODP) Expedition 317 focuses on understanding the relative importance of global sea level (eustasy) versus local tectonic and sedimentary processes in controlling continental margin depositional cyclicity. The emphasis is on the Oligocene-Holocene period when global sea level change was dominated by glacioeustasy. Drilling the Canterbury Basin on the eastern margin of the South Island of New Zealand takes advantage of high rates of Neogene sediment supply, which preserved a high-frequency (0.5-1 m.y. periods) record of depositional cyclicity. The Canterbury Basin offers the opportunity for expanded study of the complex interactions between processes responsible for the preserved stratigraphic record of sequences and provides information on the early history of the Alpine Fault plate boundary. The deepest target of this expedition is the early Oligocene Marshall Paraconformity hypothesized to mark the initiation of thermohaline circulation and the proto-Antarctic Circumpolar Current. Currents have strongly influenced deposition in parts of the basin by locally building large sediment drifts, which aggraded to shelf depths, within the prograding Neogene section. Understanding the depositional history, paleoceanographic record, and sequence stratigraphic significance of these drifts are secondary drilling objectives. The sequences to be drilled are correlative with those drilled on the New Jersey margin (Legs 150, 150X, 174A, and 174AX), Bahamas (Leg 166), and Marion Plateau (Leg 194) during the Ocean Drilling Program. Completion of at least one transect across a far-field siliciclastic margin, which has been subject to entirely different local forcing, is a necessary next step in deciphering continental margin stratigraphy. The Canterbury Basin, where both sequence stratigraphic geometries and seismic databases are of qualities comparable to those of New Jersey, is an ideal setting for such a drilling program.