Early tertiary seafloor spreading magnetic anomalies and paleo-propagators in the northern Arabian Sea

Abstract

Study of closely spaced new marine magnetic profiles, in conjunction with published magnetic data, provide an updated identification of linear magnetic anomalies in the northern Arabian Sea from the Owen Fracture Zone in the west to the Laxmi and Chagos-Laccadive Ridges in the east. For the first time the entire magnetic anomaly sequence 28 through 20 is mapped eastwards from 65~'E up to about 70~'E. Further eastward the post-anomaly 28 oceanic crust appears to have been overlain by the volcanic material forming the Chagos-Laccadive Ridge. Contrary to earlier interpretations, the identified magnetic lineations are observed to have been segmented mainly by oblique offsets representing the pseudofaults associated with 11 major paleo-propagating ridges. These ridge propagation eventscommenced around anomaly 28 time (~6 63 Ma) and continued at least until anomaly 23 time (~6 52 Ma) and during the process a large amount of crust was transferred from the African plate to the Indian plate. The pre-anomaly 24 period was characterized by ridge reorientation, whereas such a phenomenon was not apparent durign the post-anomaly 24 period. Almost all these propagating ridges appear to have been propagating westward, probably to migrate away from the proximity of the Reunion hotspot. The accretionary process of the Early Tertiary oceanic crust in the Arabian Sea thus appears to have been greatly influenced by the propagating ridges and the nearly hotspot.