This study correlates paleobotanical observations with chemical tracers and geological interpretation for Bulgarian coals. Two samples were studied, i.e. clay sediment with embedded twigs paleobotanically assigned to Taxodium dubium and plant material scraped off from the leaf imprint of a macrofossil. An assignment of the geological age is presented by considering the biomarker assemblage and paleobotanical data in comparison with information already available for Taxodium dubium. The geochemical data with paleobotanical and geological observations indicate a Late Oligocene geological age for the Bobov dol coal. The following points support this assignment: (i) triterpenoids were completely altered to des-A-lupane or chrysene derivatives, and (ii) diterpenoids were diagenetically converted to their aromatized end products. (C) 2013 Elsevier B.V. All rights reserved.