STATISTICAL APPROACH TO STUDY THE LITHOSTRATIGRAPHIC SEQUENCE IN THE PROTEROZOIC KOLHANS
Rohini Das · Indian Association of Sedimentologists · 2019
Lithofacies succession in the Proterozoic Kolhan Group has been studied statistically using modified Cross-Association Analysis, Markov chain model and Entropy function. The lithofacies analysis based on the field descriptions 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 and cross-association analysis indicates that the deposition of the lithofacies is in NonMarkovian and non cyclic process and represents asymmetric fining- upward. 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 total 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 bypassing that finally generated non-cyclicity in the sequence. Keywords: - cyclicity,assymetricity,fan-delta, braided-ephemeral