Magnetobiostratigraphic synthesis of Leg 123: Sites 765 and 766 (Argo Abyssal Plain and lower Exmouth Plateau)

Abstract

During ODP Leg 123, Sites 765 and 766 were drilled to examine the tectonic evolution, sedimentary history, and palaeoceanography of this area of the Indian Ocean. Based on nannofossils, the base of the sedimentary section at Site 765 was dated as Tithonian. A complete Cretaceous sequence and a condensed Cainozoic sequence from the upper Palaeocene to the lower Miocene was recovered. A dramatic increase in sedimentation rate was observed in the lower Miocene, and a 480-m-thick Neogene section is present. The base of the sedimentary section at Site 766 is Valanginian, in agreement with the site's position on marine magnetic anomaly M11. Valanginian to Barremian sediments are terrigenous; younger sediments are pelagic, with abundant well-preserved microfossils. Sedimentation rate is highest in the Lower Cretaceous and decreases continually upsection. Upper Cainozoic sediments are condensed, with several hiatuses. -from Authors