Quantification of Foraminiferal Biofacies and Reconstruction of Palaeobiogeo-Graphy of the Cauvery Basin

Abstract

The paper deals with broad principles of quantified foraminiferal palaeoecology involved and their application in reconstructing the palaeoenvironments for different stratigraphic units (Upper Jurassic-Lower Palaeogene in age) exposed in the western part of the Cauvery Basin. The parameters used are the functions of structurally related characteristics and morphogenetic diversities of the foraminiferal fauna which are resultant of the environmental requirements, tolerance and preferences. The first sedimentary cycle started with fresh water deposits which soon gave way to brackish water and later continued under dominantly marine influence. The major transgressive phases during Neocomian-Albian, Senonian and Paleocene are better reflected in the quantitative bio-facies analysis. Along certain palaeomarginal highs, the environment favoured reef development where terrigenous influx was minimum. The strand-line progressively shifted since Lower Cretaceous times from west to east. The shift during Lower-Middle Eocene was more prominent and a delta front progressively started building with regression in the region bordering the western margin. The resultant sediments now cover a greater part of the exposed area and form the youngest exposed stratigraphic unit of this Basin.