Provenance, tectonics and palaeo environment of Mesoproterozoic Saundatti Quartzite Member of Kaladgi Basin, India: A petrographic view.

Abstract

The Kaladgi Basin, one of the important Proterozoic Sedimentary basins of Peninsular India, exposes a thick sequence of Proterozoic succession composed of a variety of lithologies with predominance of arenaceous rocks interrupted with Carbonate sediments at different stratigraphic levels. The present work focuses mainly on understanding the Sedimentological nature and diagenetic character of the Lower part of the Lokapur sub-group rocks that are exposed in and around Savadatti Town, Belagavi District of Karnataka. These rocks are mainly composed of Arenite sequences of varying grain size. The clastic succession comprises lithologies Sandstones with minor conglomeratic facies at the lower regimes. An attempt is made to identify the detailed petrographic character of the sandstones to understand the provenance and depositional environments based on the detailed petrographic observation. The study suggests that the coarse clastic conglomerates are essentially polymictic types and the sandstones are sub-mature to mature (mineralogically), medium to coarse grained and can be categorized mainly into lithic/feldspathic and quartz arenites. Minor occurance of feldspars as the framework constituent also suggests that the rock have undergone considerable transport. However with their variable degree of alteration (from fresh to partially alter to completely altered grains) associated with textural maturity and nature of Quartz point towards the possibility of derivation of these sediments from two different sources. Palaeocurrent data that indicate a NW palaeoslope suggest the derivation of sediments from a variety of granitic and gnesssic crystalline complexes occurring along the basin margin. The maturity of the sandstones (Quartz Arenites) is attributed to the recycling and re-working of the older sediments. Analysis of Textural parameters of these rocks pointed towards deposition under beach environments. The lack in preservation of much amount of feldspar in these sandstones is indicates a remote source and relatively dry-arid climate of the source area.