Morphotectonics and ridge jumpings in the Indian Ocean

Abstract

AbstractThe Indian Ocean experienced a complex tectonic evolution after its initial rifting since the Late Cretaceous, including three major jumpings and reorganizations of mid‐ocean ridges at 80 Ma, 60 Ma, and 40 Ma, respectively, which had important impacts on the present‐day tectonic pattern and physiography. We develop a new division principle on submarine morphotectonics and subdivide the Indian Ocean into first‐ to fourth‐order tectonic geomorphologic units and four growth phases, by integrating bathymetric and gravity anomaly data within a regional plate kinematic framework. The Southwest Indian Ocean (SWIO), the Central Indian Ocean (CIO), and the Southeast Indian Ocean (SEIO) comprise the first‐order geomorphologic units, based on tectonic symmetry and seafloor‐spreading rates. Four second‐order units with plate ages of >80 Ma, 80–60 Ma, 60–40 Ma, and 40–0 Ma, respectively, are divided in the Indian Ocean, based on dramatic changes in the direction of the main fracture zones due to three ridge jumping events. Third‐order units are characterized either by positive gravity anomaly associated with transform faults or oceanic core complexes (OCCs) or by negative gravity anomaly associated with hotspots or continental fragments of East Gondwana. The third‐order units are subdivided into fourth‐order units. Typical fourth‐order units are characterized either by gravity values of less than −46 mGal associated with hotspot‐related crustal thickening or greater than 46 mGal associated with OCC‐related or other unconfirmed tectonic‐related crustal thinning. Copyright © 2015 John Wiley & Sons, Ltd.