New data on geology of the Osborn Knoll, Indian ocean

Abstract

The Osborne Plateau is a large intraplate elevation in the eastern part of the Indian Ocean, which has been poorly studied by geological and geophysical methods. In cruise SO258/1 on RV Sonne, were collected new data with Parasound seismic profiling and multi-beam echo sounder survey. Fractures in the sedimentary cover, which extend to the bottom surface, indicate on high neotectonic activity in the area of the Osborne Plateau. It can continue up to the present, as well as in the adjacent segment of the Ninetyeast Ridge, where strong earthquakes are recorded. Two reflectors in the upper part of the sedimentary cover mark global regressive changes in the World Ocean level at the boundary of the Miocene / Pliocene and Pliocene / Pleistocene. The reflector in the sediments at the boundary of the Lower / Upper Pliocene is associated with a change in the regional hydrodynamic regime at the time in the eastern Indian Ocean. The rocks dragged on the Osborn Knoll are identical to volcanic rocks of the Ninetyeast Ridge, confirming their assumed genetic similarity, but they are more identical to basalts of the Kerguelen plateau. Extremely modified vitroclastic tuffs appear to have been formed as a result of explosive volcanic eruptions of alkaline basalts or foidites in subaeral or relatively shallow water conditions and represent the most recent eruption in the region.