Foraminiferal signatures of mass transport from the north-west continental shelf off Western Australia, IODP Exp. 356

Abstract

In 2015, Integrated Ocean Discovery Program Expedition 356 drilled along the margin off Western Australian to investigate the history of the Indonesian Throughflow (ITF) and its integral role in the development of global thermohaline circulation and climate. Throughout the expedition, a suite of foraminiferal analyses were employed wherein planktic specimens provided biostratigraphy and an incredibly diverse benthic fauna (~ 260 species) was used to reveal palaeo- water depth, palaeobathymetric setting and variable conditions at the sediment-water interface. Benthic foraminiferal biofacies are particularly sensitive to changes in environmental conditions, have a rapid turnover and are ideal proxies for monitoring physical and chemical changes in marine environments. When this information is combined with lithostratigraphic and other microfossil data, a robust understanding of past environments and past geological events can be reconstructed. Shipboard data were used to isolate horizons of interest for more intense sampling at IODP Site U1461, situated on the North-West Shelf, at 127 m of water depth. The shipboard data revealed a large (~150 m-thick) turbidite horizon hosting benthic foraminifera from a substantially shallower water depth than the horizon immediately preceding the horizon. We present preliminary foraminiferal results combined with shipboard sedimentary descriptions to better constrain the deposit’s occurrence in the biostratigraphic record, use benthic foraminifera to elucidate the deposit’s sedimentary origins and link this event with others in the region to investigate potential catalysts for its deposition.