THE SEDIMENTOLOGY AND ORIGINS OF THE NATARAJA SLIDE, ARABIAN SEA: A GIANT MASS TRANSPORT DEPOSIT

The Nataraja Slide was recently discovered by seismic mapping off the west coast of India in the Arabian Sea. It is the second largest mass transport deposit by volume known on a passive margin. This event is important to aid in the understanding of how mass wasting affects the shape of the seafloor of sedimentary basins and the effects, such as tsunamis, that are generated from them. The deposit was emplaced around 10.8 Ma as a result of collapse of the western India margin running 550 km into the basin. The deposit has been cored in two locations by the International Ocean Discovery Program (IODP) Expedition 355 in places where it is ~300 m (Site U1456) and ~100 m thick (Site U1457). Although homogenous in seismic the deposit appears to have two units at Site U1456, each with a coarse carbonate dominated base, composed of clast supported breccia and massive calcarenite with minor volumes of weathering, and vesicular basalt. These strata are overlain by steeply inclined, slumped but otherwise coherent pyritized mudstones and minor volumes of matrix-supported conglomerates, interpreted as debris flows. Emplacement appears to have eroded significant thicknesses of Indus Fan turbidites at Site U1456, as there is a hiatus spanning ~5 m.y. at the base, while at Site U1457, the slide directly overlies Paleocene reddish mudstones on the eastern flank of the Laxmi Ridge, whose presence diverted the deposit to the south in the Laxmi Basin and away from the main Arabian Sea basin. This study aims to further evaluate the depositional mechanisms, the sediment sources, and the original trigger for the mass wasting. We use bulk sediment Nd and Sr isotope geochemistry, single grain zircon U-Pb dating and basic petrography to understand the provenance of sediment in this late Miocene mass transport deposit.