A comparative study of texture, mineralogy and sedimentation of selected beach sediments of Goa Coast, India

Abstract

Present work on beach sediments of Goa Coast has been attempted in order to understand the variations in textural and mineralogical parameters of sands for the interpretation of depositional and transportational mechanisms. The grain-size parameters of beach sands suggest that (i) the sands are fine-to-coarse-grained, very well-sorted to well-sorted, positively skewed to negatively skewed, platykurtic to leptokurtic in Tiracol-Chapora beach of north Goa and (ii) fine-grained, moderate to well sorted, negatively skewed, platykurtic to leptokurtic sands in Colva beach of south Goa. The shape parameters suggest that the sands in both areas are subspherical, subangular to subrounded in nature indicating probably a short distance of transportation. The heavy mineral assemblage consisting of unstable to ultrastable opaque and non-opaque minerals suggest a nearby mixed igneous and metamorphic source of the sediments. The discriminant analysis using all the samples and seven variables clearly separates the sediments of Tiracol-Chapora and Colva sands. In general, the grain size data of these sands along the Goa Coast indicate a fluctuating energy condition of the depositional site contributing a mixed nature of sediments with variable amounts of sand, silt and clay in northern part as compared to that of the southern part of the area where sands show unimodal distributions indicating uniform depositional conditions.