Petrographical and geochemical characterization of lignites, sub-bituminous coals and carbonaceous sediments from the Erin Formation, Southern Basin, Trinidad - Implications on microfacies, depositional environment and organic matter alteration

Maceral analysis showed the coals at South Chatham to be dominated by huminite (86-97%), with less abundant inertinite (2-12%) and sparsely occurring liptinite (0-2%). The distribution of coal facies based on critical macerals such as humodetrinite and humocollinite suggests formation of these lignites in a reed marsh to wet forest swamp, exhibiting transition into an upper to lower delta plain environment. Similar conclusions are deduced from tissue preservation, gelification, groundwater and vegetation indices of the coals indicating that they are composed predominantly of small herbaceous plants.