Pre- and post-monsoonal changes in grain size and heavy minerals in the sediments from Kalbadevi Bay, Ratnagiri, west coast of India

Abstract

Sediments from the Kalbadevi Bay, Ratnagiri collected during January, May and October have been studied for processes responsible for the observed grain size variations and heavy mineral distribution. The study shows transportation of loose sand fractions from shallow depth (< 5 m) during the SW monsoon and deposition in deeper depths (>10 m) during post-monsoon. It is further inferred that the E-W trending depression in the central part of the Bay partially controls the sand distribution. Clay accumulation in the Bay begins after the culmination of monsoonal effects. Distribution of ilmenite appears similar to that of magnetite. Pre- and post- monsoonal changes in the distribution pattern of heavy minerals show that fine to very fine particles (< 62.5 µ) of magnetite and ilmenite have maximum concentration (14 to 26 % and 14 to 29 % respectively) in the month of October (post-monsoon). This may be due influence of strong currents in the Bay after the culmination of SW monsoon.