oa Geochemical Investigation on the Organic Rich Sediments of Ashoka Coalfield of North Karanpura Basin, India

The organic rich sediments of the Ashoka Coalfield, North Karanpura Basin is investigated geochemically using GC-MS, FTIR and Petrographic techniques to understand the depositional environment and hydrocarbon potential. The n-alkanes distribution displays unimodal and bimodal patterns, reflecting diverse organic matter sources. The values of Pr/Ph ratio (av. 3.95) also suggest that deposition largely occurred in oxic environments in distal settings. The overall dominance of odd number carbon alkane over even carbon numbered n-alkanes in the coals indicates input from higher vascular plants. The hopane presence indicates contribution of microbial lipids and suggests bacterial degradation of the organic matter after deposition. The C27 steranes shows the marine incursion to the paleomire. The C29 sterane and the vitrinite and liptinite groups of macerals indicate that the peat-forming vegetation (mainly higher plants) accumulated in the suboxic condition. Hence it can be assumed that the overall deposition occurred in oxic-suboxic conditions. The vitrinite reflectance (0.52-0.60%) classify the studied coal as Medium-Rank ‘D’, reaching the mature zone of hydrocarbon generation.