Sediment Thickness and Igneous Crust Beneath the Arabian Basin, NW Indian Ocean

Abstract:

The Arabian Basin is known for its widespread Indus Fan sediments- second largest submarine fan in the world- covering the entire basin which got deposited primarily by erosion of sediments from the western Himalaya, Karakoram and Hindu Kush. Further, the basin was evolved due to complex processes of spreading ridge propagation under the influence of Reunion hotspot during the Early Tertiary. Though crystalline crust of the basin is considered as a normal oceanic crust, it displays basement depth anomalies. In view of the above complexity, estimates of volume and mass of sediment, as well as igneous crust beneath the seafloor of the Arabian Basin are provided in this study that can be used as constraints to refine its tectonic evolution. Ship-borne and satellite altimetry derived bathymetry and gravity data along with seismic data are utilized to estimate sediment thickness, depth to the Moho as well as igneous crustal thickness in the Arabian Basin. Both 2D forward and 3D inverse gravity modeling were carried out and maps depicting spatial distribution of sediment thickness, igneous crustal thickness, depth to the Moho and mean sedimentation rate are presented. The study reveals that northwestern region of the Arabian Basin is covered with maximum 3.5 km thick Indus fan sediments, whereas thin veneer of sediments (~500 m) is interpreted near northeastern flank of the Carlsberg Ridge. Depth to the Moho and crystalline crustal thickness vary from 9 to 13 km and 3 to 8 km, respectively across the basin. The estimated volume and mass of the basinal (i) sediments are ~1.48x10⁶ km³ and 3.2x10¹⁸ kg, whereas (ii) crystalline crust are ~4.87x10⁶ km³ and 1.36x10¹⁹ kg, respectively. Improved understanding of sediment thickness within the basin will aid in a wide range of subject areas, including analyses of thermal subsidence of the oceanic lithosphere and in palaeo-bathymetric reconstructions. Further, information provided by this study will be useful in planning detailed geological and geophysical studies to explore mineral resources as well as in substantiating India’s claim in delimiting the outer edge of the continental margin, defined according to the United Nations Convention of the Law of the Sea (UNCLOS).