Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

R. K. Sukhtankar ¹

Affiliations
1 Department of Geology, University of Poona, Pune 411 007, IN

Abstract

Petrographical studies of the Kaladgi sandstone of Precambrian age from the Bijapur district, Karnataka, revealed the presence of detrital and authigenic tourmaline. The presence of authigenic tourmaline in the form of individual crystals is used to decipher the post-depositional geochemical changes. The increasing silica content and the alkaline pH of the interstitial fluids have favoured the formation of authigenic tourmaline.

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R. K. Sukhtankar ¹

Affiliations
1 Department of Geology, University of Poona, Pune 411 007, IN

Abstract

Field studies along the coast of Vengurla, Maharashtra, reveal presence of stabilised dunes, older and younger raised beaches apart from the present intertidal zone. From these geomorphic features, a fall in sea-level to the extent of about 4 m and 1 m during the Holocene period is suggested.

The sediments constituting these geomorphic features have been examined for their grain-size characteristics. Statistical parameters, such as: mean size, standard deviation and skewness have been compared from each geomorphic unit. The comparison indicates reversals in their trends of variation, which have been ascribed to transgressional cycles.

It is suggested that tectonic control, which operated either through a relative fall in sea-level or an emergence of the Indian shield during the Holocene period is responsible for the accretionary nature of the beach.

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R. K. Sukhtankar ¹, S. J. Pandit ¹, A. J. Shirke ¹, S. A. Kulkarni ¹

Affiliations
1 Department of Geology, Shivaji University, Solapur 413 003, IN

Abstract

Development of living corals in the form of patch reefs has been recorded in the intertidal zone at Bhandarpule beach, District Ratnagiri, Mabarashtra. These are pink and reddish in colour and are composed of corals of the order of Stolonifera. These occur as a thin blanket on the hard substrate of volcanic breccia. Their occurrence in association with oyster bed and sea cave but at different elevations represents minor fluctuations of the sea level during the Holocene, associated with the Flandrian transgression.

Keywords

Coral Reefs, Palaeontology, Ratnagiri District, Maharashtra.

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