Abstract
Chromatographic separation and mass spectral studies of bitumens extracted from lithotypes (humovitrain, xylain, liptain and humoclarain) from the Miocene Maritza-Iztok lignite reveal the following: (1) A preponderance of the α-phyllocladane skeleton over the pimaranes/abietanes. The variety of tricyclic diterpanes confirms that the generation biota included gymnosperms; (2) The presence of dicotyledonous angiospermaes in the generation biota is indicated by the occurrence of widely distributed des-A-lupane structure; (3) The dominance of terpanes over steranes confirms the prevailing contribution of terrigenous input; (4) The preponderance of C27β hopane and the presence of ββ hopanes indicates a low degree of thermal maturation.