Organic geochemistry and petrology of subsurface Paleocene-Eocene Wilcox and Claiborne Group coal beds, Zavala County, Maverick Basin, Texas, USA

► Sapropelic Claiborne coals are moderately persistent or recurring. ► A previously unrecognized unconformity or change in regional heat flow exists. ► Locally elevated thermal maturity is from Laramide orogenic thickening. ► Fluorescence and chromatography characteristics are linked to resinite. ► Microbial methanogenesis may be restricted by low recharge and nutrient availability.