Abstract
Expedition 317 investigated the record of global sea-level change (eustasy) within continental margin sedimentary sequences and how eustasy interacts with local forcing to produce preserved sedimentary architectures. The Canterbury Basin, on the eastern margin of the South Island of New Zealand, was selected to study these complex interactions because of high rates of Neogene sediment supply from the uplifting Southern Alps. This sediment input results in a high-frequency (~0.1–0.5 My periods) record of depositional cyclicity that is modulated by the presence of strong ocean currents. The expedition recovered sediments as old as Eocene but focused on the sequence stratigraphy of the late Miocene to Recent, when global sea-level change was dominated by glacioeustasy. A transect of three sites was drilled on the continental shelf (Sites U1353, U1354, and U1351), plus one on the continental slope (Site U1352). The transect samples the shallow-water environment most directly affected by relative sea-level change. Lithologic boundaries, provisionally correlative with seismic sequence boundaries, have been identified in cores from each site. Continental slope Site U1352 provides a record of ocean circulation and fronts during the last ~35 My. The early Oligocene (~30 Ma) Marshall Paraconformity was the deepest target of Expedition 317 and is hypothesized to represent intensified current erosion or non-deposition associated with the initiation of thermohaline circulation in the region. Expedition 317 involved operational challenges for JOIDES Resolution, including shallow-water, continental-shelf drilling and deep penetrations. Despite these challenges, Expedition 317 set a number of records for scientific ocean drilling penetration and water-depth.
Highlights
Introduction and GoalsIn order to evaluate predictions of future changes in global sea level and shoreline location, it is vital to constrain the range of past variability
Throughout the “Icehouse” period of the last ~30–40 million years, the changing volume of continental ice has been the principal driver of high-amplitude and high-frequency (~1 My and less) global sea-level change
The eastern margin of the South Island of New Zealand is date clinoformal seismic sequence boundaries and sample part of a continental fragment, the New Zealand Plateau, that associated facies to provide information (e.g., paleo-water rifted from Antarctica beginning at ~80 Ma (Anomaly 33)
Summary
In order to evaluate predictions of future changes in global sea level and shoreline location, it is vital to constrain the range of past variability. Depositional processes associated with sequence stratigraphic record provides information on ages, the sequence stratigraphic model on a prograding continendepositional environment, and past water depths during tal margin where large-scale depositional geometries and sea-level cycles from coastal plain to continental slope sequence architectures are well constrained by seismic data. Since boreholes provide information at only a few Canterbury Basin complements MAT because the Middle locations, integration with seismic imaging is crucial Such Miocene to Recent Canterbury sequences are mainly integration performs three vital functions: 1) placing drilling younger than those calibrated so far on the New Jersey marresults within a two- and three-dimensional context, 2) con- gin (Fig. 4). Expedition 317 complements Leg 181 drilling by focusing on the landward part of ENZOSS
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