Biomarker signatures of Early Cretaceous coals of Kutch Basin, western India

摘要

The unique position of the Indian plate during the Late Mesozoic draws our attention to study the palaeofloral community from the Early Cretaceous coals of the Kutch Basin using organic geochemical proxies. The biomarkers were studied by GC-MS technique to reveal the botanical source of organic matter. The Rock-Eval pyrolysis data show that samples are thermally immature and organic matter is a mixture of type-II and type-III kerogen. Saturated hydrocarbons are characterized by nC(14) to nC(35) alkanes with odd over even preference (carbon preference index 1.4 to 3). The pristane/phytane ratios ranging from 0.8 to 2.9 indicate suboxic depositional environment. The occurrence of sesquiterpenoids and diterpenoids depicts that the organic matter was derived from conifers. The predominance of abietane/pimarane class diterpenoids and presence of phyllocladane suggest that Araucariaceae and Podocarpaceae-dominated conifer vegetation served as the source material for the formation of these Early Cretaceous coal beds of the Kutch Basin.