Abstract:
High resolution satellite derived Free Air Gravity (FAG) anomalies over the Maldive Ridge segment of the
Chagos-Laccadive Ridge and adjoining areas of the Arabian Basin and Central Indian Basin was analyzed to
understand their structure. Indian Ocean Geoidal Low corrected FAG depict the N-S trending relative highs
associated with the Maldive Ridge, the lows associated with the Vishnu Fracture Zone, and the seafloor fabrics
associated with spreading Central Indian Ridge in the Arabian Basin. Transformation operations for enhancing
the short, intermediate and long wavelength anomalies were carried out. The northward continuation of the
Vishnu Fracture Zone, the eastward extension of the fracture zones of the Arabian Basin into the Deep Sea
Channel (DSC) region, between the Maldive Ridge and the Chagos Bank, and the signatures related to northsouth
trending coral reefs have been deciphered from the enhancement of short wavelength anomalies. The long
wavelength anomalies show N-S highs along the axis of the Maldive Ridge and the DSC, which on comparison
with previous studies, is inferred to be the signature related with the underplated material from the passage of
the Indian plate over the Reunion Plume. Depth to top of two interfaces over the Maldive Ridge and the DSC
were computed using the power spectral method by assuming a window of 110 km dimension and 50 km
overlap. Depths were thus calculated for 44 blocks along the ridge axis. The average depth to the top of the
shallow interface was found to be 5.5 km while that of the deeper was 11.0 km. These depths and interfaces were
confirmed by undertaking 2D forward modelling along a 300 km long N-S profile along the western segment of
the Maldive Ridge. Integrating with the available previous geophysical studies, it is inferred that the shallow
interface represents the depth to the top of the acoustic basement underlying 1–1.5 km thick lava flow unit while
the deeper is associated with the interface between the crust and initial Moho before the underplating took place
(presently top of the underplated material). From the present study, it has been inferred that the Deep Sea
Channel between the Maldive Ridge and Chagos Bank can be purely oceanic in nature.
