Organic Matter Characterization and Palynological Evidence of Mid-Ordovician to Pennsylvanian Age of the Tabenken Coal, Northwest Cameroon

Abstract

: In this work, we intend to investigate the kerogen composition of the Tabenken coal hence, its palaeo-depositional environment and age. Tabenken is one of the three areas in the continental sectors of the CVL (Cameroon Volcanic Line) where coal occurs in between a granitic basement and volcanic outpours. Samples of coal from this seam were studied to determine the organic matter richness, maturity, depositional environment and its age through organic geochemical techniques such as Rock-Eval pyrolysis and palynological studies. HI (Hydrogen Index) obtained is less than 200 mgHC/gTOC for most of the samples indicating Type III kerogen for these samples (gas prone) and terrestrial source of the original peat-forming organic matter. One sample presents a HI of 462 mgHC/gTOC indicating organic matter type II, prone to producing oil. Palynological studies reveal the presence of hydrogen-rich AOM (Amorphous Organic Matter) indicating preservation under dysoxic-anoxic conditions. High values of TOC ranging from 0.29 to 1.98 are suggestive of AOM of terrestrial origin. The remarkable absence of pollen suggestive of deposition before the Pennsylvanian during which the earliest forms of flowering plants first appeared displays a relative abundance of spores in the organic residue suggestive of deposition from the mid-Ordovician. Careful interpretation of palynological data suggests the coal was laid down from the mid-Ordovician to the Pennsylvanian age.