IODP Expedition 356: Drilling to reveal a 5 million year carbonate and subsidence history on the Northwest Shelf of Australia

Abstract

The late Cenozoic carbonates of the Northwest Shelf are important subsidence history archives that also cause significant sonic velocity problems affecting seismic imaging of underlying strata. Despite their substantial thickness and areal extent, these carbonates have been sampled only in engineering foundation boreholes and as cuttings and rare sidewall cores in petroleum wells. In August-September 2015 the International Ocean Discovery Program (IODP) will drill a transect of shelf to shelf margin cores in this region. Six sites will be drilled over 10° latitude from the Perth Basin to the Bedout sub-basin by RV JOIDES Resolution with continuously cored penetrations of 300 m to 1.1 km. An array of shipboard and post-cruise biostratigraphic, sedimentological and geochemical analyses will be carried out on these cores to achieve three primary aims: 1. Provide empirical input into the spatiotemporal patterns of subsidence along Northwest Australia that can be used to place fundamental constraints on the interaction between Australian plate motion and mantle convection and to ground truth geodynamic models. 2. Determine the timing and variability of regional oceanographic features in order to understand the controls on Neogene carbonate stratigraphy and reef development. 3. Obtain a tropical to subtropical climate and ocean archive, directly comparable to deep-ocean oxygen isotope and ice-core archives, to chart the variability of the Australian monsoon and the onset of aridity in northwestern Australia. Each site will be triple cored using a combination of Advanced Piston Coring (APC), Extended Core Barrel (XCB) and Rotary Core Barrel (RCB). An array of downhole measurements will be taken using three standard IODP tool string configurations: the triple combination (triple combo), Formation MicroScanner (FMS)-sonic, and Versatile Seismic Imager (VSI). These will be used to correlate the cores to regional multichannel seismic profiles in order to gain a better understanding of Northwest Shelf stratigraphy and neotectonics.