Paleoenvironmental and Paleodepositional Reconstruction of the Permian Coals From Burhar Seam IV of Sohagpur Coalfield, India: Using Integrated Mineralogical, Geochemical and Petrographic Proxies

Abstract

Deciphering the paleoenvironment from coal samples is of great academic and industrial relevance. Coal samples from the Burhar seam IV, Sharda coalmine of the Sohagpur coalfield, were analysed using a multi-proxy approach to interpret paleoclimate and paleo-depositional conditions. The analysis incorporated several techniques, viz., Ultimate Analysis, X-ray Fluorescence (XRF), X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy and coal petrography. The Sohagpur coal deposit is a part of the Lower Gondwana coal group, which is characterised by high ash content resulting from proximate analysis. While XRD and FT-IR spectra identify the mineral components in the coal, XRF results show different oxide and elemental concentrations. Micropetrography provided insights into the maceral and mineral constituents of the samples. XRD, XRF and FT-IR results indicate a warm and humid paleoclimate favoured by intense chemical weathering, evidenced by the presence of minerals such as kaolinite. Depositional conditions were further examined through sulphur content analysis using Ultimate Analysis and elemental concentrations from the XRF. These suggest deposition in a transitional environment between oxic and suboxic conditions. Petrographic analysis also supported these findings, which indicate the coal samples were deposited in alternating oxic and anoxic moor conditions, with good tissue preservation.