Geology

Biography

Biography: Shipra Sinha

Abstract

Lithofacies succession in Chaibasa-Naomundi Basin of the Proterozoic Kolhan Group, Jharakhand has been studied statistically using modified Markov chain model and entropy function. The lithofacies analysis based on the field descriptions, petrographic investigation and their vertical packaging has been done for assessing the sediment depositional framework and the environment of deposition. Six lithofacies arranged in two genetic sequences have been recognized within the succession. The result of Markov chain analysis indicates that the deposition of the lithofacies is Non-Markovian process and represents asymmetric fining-upward non-cyclicity. The chi-square test has been done to test of randomness in hypotheses for lithofacies transition at confidence level of 95%. The entropy analysis has been done to evaluate the randomness of occurrence of lithofacies in a succession. Two types of entropies are related to every state; one is relevant to the Markov matrix expressing the upward transitions (entropy after deposition) and the other relevant to the matrix expressing the downward transitions (entropy before deposition). The energy regime calculated from the entropy analysis showing maximum randomness suggests that deposition is by quick rapid flow which gradually changes to slow flow by changing the depositional pattern from deltaic sandstone to lacustrine shale deposit as a result of sediment bypassing giving rise to non-cyclicity in the sequence.