Tectonic model for the evolution of oceanic crust in the northeastern Indian Ocean from the Late Cretaceous to the Early Tertiary

Abstract

Bathymetry and magnetic studies (part of the Trans Indian Ocean Geotraverse investigations) in the northeastern Indian Ocean revealed seafloor topographic features, magnetic Lineations (19 through 32B) and abandonaed spreading centers. The seafloor topography of the Ninetyeast Ridge is relatively wider and shallower south of 15 degrees S. The magnetic anomalies indicate nine fracture zones. Two of them are newly identified. Some of the fracture zones are reflected in the bathymetry. Abandoned spreading centers between 86 degrees E Fracture Zone (FZ) and 92 degrees E FZ are interpreted as the western extensions of the Wharton Ridge. They ceased spreading along with other spreading centers in the Wharton Basin soon after the formation of magnetic anomaly 19 (around 42 Ma) and merged the Indian and Australian plates as single Indo-Australian plate. The pattern of magnetic lineations between 86 degrees E FZ and 90 degrees E FZ indicate a series of southerly ridge jumps at anomalies 30, 26 and 19. These ridge jumps transferred portions of the Antarctic plate to the Indian plate. The captured portions and offset along 86 degrees E FZ between India-Antartica Ridge and Wharton Ridge resulted in an anomalous extra oceanic crust between 86 degrees E FZ and Ninetyeast Ridge spanning 11 degrees in latitude