Nd and Pb isotope evolution of deep water masses in the eastern Indian Ocean during the past 33 Myr

The location of a second crust (VA16 13KD-1) from 2100 m water depth on the Scott Plateau off NW Australia is beneath the present day outflow of Pacific-derived surface and thermocline water masses into the eastern Indian Ocean. The pattern of the Pb isotope time series of this crust and the observed changes in Pb isotope mixing relationships, which occurred at ∼ 11.5 and ∼ 3.5 Ma, reflect the combined influence of advection and mixing of water masses through the Indonesian Seaway and weathering of volcanic source rocks within the emerging Indonesian Island Arcs over the past 33 Myr. The Nd isotope time series shows a pattern similar to central and southwest Pacific crusts and is best explained by a mixture between Nd from water masses advected from the Indian and Southern Ocean and Nd released by weathering from the emerging Indonesian Island Arcs.