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.
Volume 128 | Issue 8
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