Identification of probable faults in the vicinity of Harnai-Ratnagiri region of the Konkan coast, Maharashtra, India
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The Konkan coastline from Harnai to Guhagar consists of many straight line segments being arranged in an en-echelon manner. The false color composite (FCC) reveals the coincidence of these segments with NW-SE trending lineaments that conspicuously cut across the Deccan Basalt Province adjoining the seacoast. Furthermore, another less prominent lineament set has been noticed in ENE-WSW direction offsetting the former. These lineaments are occupied by major rivers which originate from the Western Ghats escarpment and flow westerly into the Arabian Sea. Trellis and barbed type of drainage pattern are observed due to strong influence of these sets of lineaments. One of the NNW-SSE lineaments extending from Harnai to Kajurli has been studied, which reveals the presence of narrow and straight course of river flowing along it. While the western bank of the river is steep with a number of waterfalls, the eastern side carries flat terraces. The riverbed exposes highly fractured basalt criss-crossed by NNW-SSE and ENE-WSW sets of fractures. The NNW-SSE set which is sympathetic to the main lineament, hosts quartz veins that show pinch-and-swell and boudinage structure. The boudins are sigmoidal and are arranged in en-echelon pattern indicating shear origin. Hence it is believed that the NNW-SSE lineaments are probable faults in the area. Rare slickensides are observed on the quartz vein wall, which are mostly subvertical, suggesting a dip slip nature of faulting. The faulting is post-Deccan Basalt and could be Quaternary in age.
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