Tectonic constraints on the hot-spot formation of Ninetyeast Ridge

Abstract

Magnetic data in the Central Indian Basin demonstrate that the spreading center immediately west of Ninetyeast Ridge jumped to the south by a total amount of 11° between 68 and 46 Ma, implying that parts of the mirror image of Ninetyeast Ridge on the Antarctic plate were transferred onto the Indian plate. The obliquity of Ninetyeast Ridge relative to the fracture zone pattern and the occurrence of an Eocene extinct spreading axis in the Wharton Basin suggest that the northern part of Ninetyeast Ridge was emplaced by intraplate volcanism on the Indian plate, whereas the middle and southern parts of the ridge were emplaced along transform plate boundaries. The northward drift of the Indian plate over a single hot spot is the most plausible origin for Ninetyeast Ridge. Based on a recent kinematic model for the relative motions of the Indian, Antarctic, and Australian plates, we present a simple model that reconciles most of the available observations for Ninetyeast Ridge. -from Authors