Turbidite layers and grain size distribution in ODP Site 123-765 (Table 2)

A middle to upper Miocene turbidite depositional system exists at Site 765 in the southeastern Argo Abyssal Plain, along the northwest margin of Australia. Turbidites consist predominantly of planktonic calcareous components. Textural, mineralogical, bedding, and downhole logging trends within the system support the idea of a rapid progradation of the turbidite system in the middle to late Miocene. The onset of abundant turbidity currents into the area is attributed to changes in oceanographic conditions that accompanied the progressive lowering of sea level associated with major continental ice build-up on Antarctica. These data, in conjunction with seismic stratigraphy, support the existence of two major depositional pulses. Gradual retrogradation of the system occurred in latest Miocene time, coincident with the subsequent rising of sea level. Retrogradation of the system was overwhelmed by massive slope failures during the Pliocene, presumably triggered by earthquakes associated with the progressive Miocene-Pliocene collision of the Australian margin and the Sunda-Banda Arc.