Submarine terrace limestones from the continental slope off Saurashtra-Bombay: Evidence of Late Quaternary neotectonic activity
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Bathymetric and shallow seismic data from the continental slope off Saurashtra-Bombay indicate wide submarine terraces at 130, 145 and 170 m and reefal structures at 320-360 m water depths. 10 cm thick slabs of limestones are recovered from the 130 m depth terrace. Some of these limestones consist of thin micrite layer on the top and a sandy layer below and others are similar to calcarenites. They contain greater than 95% aragonite and minor high and low-magnesium calcite. Acicular aragonite cements occur as isopachous crusts. Dissolution and clotting of aragonite needles and drusy calcite in the interstices indicate cementation of the limestones at inter-tidal conditions. The age of the limestones is 11,900 years BP. These imply that the 130 m depth terrace was at intertidal depths at about 12,000 years BP. The eustatic sea-level, however, was at - 90 m at 12,000 years BP. This disparity suggests neotectonic activity and subsidence by about 40 m on the Saurashtra-Bombay region some time after 12,000 years BP.
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