The Evolution of the Indian Ocean since the Late Cretaceous

Abstract

All available ship and aeroplane tracks across the Indian Ocean were searched for identifiable magnetic anomalies and transform faults, and hence the age and direction of motion at the time of formation of about two-thirds of the floor of the ocean established. The magnetic lineations show that India moved away from Antarctica at about 18 cm/y for 20 My in the Early Tertiary. This rapid motion ceased in the Eocene and was followed by a period in which little or no spreading took place west of the Ninety East Ridge. Australia separated from Antarctica during this period. The present spreading episode began about 36 My ago. This detailed study has permitted instantaneous poles of rotation to be obtained, and has established that Africa is now moving northward at 2cm/y relative to Antarctica in the South West Indian Ocean. The evolution of the triple junction between the South East, South West and Central Indian Ridges is clearly reflected in the topography and magnetic lineations. The depth of parts of the ocean formed since the Late Cretaceous increases with age in the manner expected from the temperature structure of a cooling plate, and supports the evolution determined from the magnetic lineations in a most remarkable way. Heat flow observations are more scattered but also consistent with the same thermal model. The proposed evolution agrees with the distribution of known continental fragments and with the Late Cretaceous palaeomagnetic poles from surrounding continents and one obtained from the shape of the magnetic lineations south of India. It is, however, not yet clear how to reconstruct Gondwanaland from the Late Cretaceous reconstructions.

Early Cenozoic global plate reorganization

“…A statement by McKenzie and Sclater [64] with reference to the Indian Ocean region helps to elucidate the global observations presented: "Since the momentum of plates can always be neglected, any change in their motion must involve a change in either the driving forces or the resistive forces." The evidence presented clearly supports the interpretation that the plate reorganization from Mesozoic to Cenozoic patterns of plate motion was primarily a response to the global distribution of resistive forces.…”

Probabilistic seismic hazard maps for the sultanate of Oman

“…Plate motion models (e.g. McKenzie and Sclater 1971;Chase 1978;Minster et al 1974;Minster and Jordan 1978;Quittmeyer and Kafka 1984) assumed right lateral slip along Owen fracture zone. Earthquake focal mechanisms show that the sense of motion along Owen fracture is right lateral strike-slip motion (Fig.…”

The role of latitude in mobilism debates

“…2a), are silent on geographic latitude, the main determinant of climate and hence of the distribution of life. However, for over a decade we had been drawing latitudes for continents: plate rotations could bring these together and global geographic grids could be constructed (32,33). Oceanic displacements, paleopoles, and latitudes were integrated into one global geographical framework (M in Fig.…”