Centre for Earth, Ocean and Atomospheric Sciences (CEOAS)

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Browsing Centre for Earth, Ocean and Atomospheric Sciences (CEOAS) by Author "Ajay, K. K."
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    Bathymetric highs in the mid-slope region of the western continental margin of India-Structure and mode of origin
    ( 2010-10-01) Rao, D. Gopala ; Paropkari, A. L. ; Krishna, K. S. ; Chaubey, A. K. ; Ajay, K. K. ; Kodagali, V. N.
    Analysis of the multi- and single beam bathymetric, seismic, magnetic and free-air gravity (ship-borne and satellite derived) data from the western continental margin of India between 12°40' N and 15°N had revealed the presence of several flat topped NNW-SSE trending bathymetric highs of considerable areal extent, 256 to 1165km2 area each at base. They are interspersed by bathymetric lows, thereby, forming a chain of horst and graben structures covered by thick sediments. 2-D modeling of the gravity and magnetic anomalies constrained by seismic results (reflection and refraction) had indicated ~23km thick crust consisting of 2 to 3km thick sediments, and a thin basaltic and granitic layer. The model has brought into focus the presence of mantle based volcanic plugs. Their geomorphological and geophysical expressions and structural pattern and associated deep-seated faults led to suggest continental crust. These features are inferred as rifted fragments of the western continental margin of India formed during its northward movement. They were subjected to sub-aerial erosion during the Paleogene due to lowered sea levels resulting in flat tops. Subsequently they were submerged to the present depths in the Neogene. The basic tectonic process appears to be regional. © 2010.
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    Seaward dipping reflectors along the SW continental margin of India: Evidence for volcanic passive margin
    ( 2010-01-01) Ajay, K. K. ; Chaubey, A. K. ; Krishna, K. S. ; Rao, D. Gopala ; Sar, D.
    Multi-channel seismic reflection profiles across the southwest continental margin of India (SWCMI) show presence of westerly dipping seismic reflectors beneath sedimentary strata along the western flank of the Laccadive Ridge - northernmost part of the Chagos-Laccadive Ridge system. Velocity structure, seismic character, 2D gravity model and geographic locations of the dipping reflectors suggest that these reflectors are volcanic in origin, which are interpreted as Seaward Dipping Reflectors (SDRs). The SDRs; 15 to 27 km wide overlain by ~1 km thick sediment; are observed at three locations and characterized by stack of laterally continuous, divergent and off-lapping reflectors. Occurrence of SDRs along western flank of the Laccadive Ridge adjacent to oceanic crust of the Arabian Basin and 2D crustal model deduced from free-air gravity anomaly suggest that they are genetically related to incipient volcanism during separation of Madagascar from India. We suggest that (i) SWCMI is a volcanic passive margin developed during India-Madagascar breakup in the Late Cretaceous, and (ii) continent-ocean transition lies at western margin of the Laccadive Ridge, west of feather edge of the SDRs. Occurrence of SDRs on western flank of the Laccadive Ridge and inferred zone of transition from continent to ocean further suggest continental nature of crust of the Laccadive Ridge. © Indian Academy of Sciences.