Journal de géologie et géophysique
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Application of Markov Chain and Entropy Function for Cyclicity Analysis of a Lithostratigraphic Sequence - A Case History from the Kolhan Basin, Jharkhand, Eastern India

Sinha S, Das S, Sahoo SR

Lithofacies succession in Chaibasa-Noamundi basin of the Proterozoic Kolhan Group, Jharkhand 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-cyclic deposition. The chi-square test has been done to test for the hypotheses of 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 changing pattern in deposition has been a result of rapid to steady flow. This results a change in the depositional pattern from deltaic to lacustrine deposit and sediment by passing that finally generated non-cyclicity in the sequence.