Facies analysis and sequence development of rampur and sirbu shale in vindhyan supergroup, central India

Abstract

Black shales are important sink for organic carbon. It also indicates the anoxia of a basin. In the present work, detailed study of two black shales one from the Upper Vindhyan, namely Sirbu Shale and other from the Lower Vindhyan, namely Rampur Shale were carried out. Both the shales are well exposed within the Vindhyan Super Group at and around Maihar and Chorhat, M.P. Facies analysis of both the shale units reveal that the black parts of the shales were possibly deposited during the maximum transgression. The Rampur Shale shows an overall transgressive trend and black shale appears in the Maximum flooding zone. The Sirbu Shale on the other hand shows an initial transgressive trend, marked as TST and then an overall regressive trend. Signatures of the microbiota are abundantly present within the black shales. Different types of microbial mat geometry have been identified within the shales. SEM-EDS analysis shows the different forms are present which are similar to some cultured mat form and their carbon content are also significantly high. The microbial mats of Sirbu Shale are different from the Rampur Shale and only crinckly laminated mats are observed.