GEOCHEMICAL SIGNIFICANCE OF THE AROMATIC HYDROCARBON DISTRIBUTION IN THE BITUMENS OF THE PUERTOLLANO OIL SHALES, SPAIN

The bituminous series of the Puertollano basin consists of three oil s hale beds named PA, PB and PC from top to bottom. In this work, result s from the study of the aromatic fractions of the bitumens are present ed. The gas chromatographic traces are dominated by phenanthrene deriv atives associated with variable contributions of arborane/fernane deri vatives and benzohopanes and, overall, small amounts of chrysene deriv atives and secohopanes. The compounds can be considered as part of two sub-groups: the first one consists of those compounds derived from re gular hopanes such as secohopanes, benzohopanes, fully aromatized hopa nes, and degradation products of hopanes such as alkylated chrysenes a nd naphthalenes. The second group is composed of arborane/fernane deri vatives and their degradation products such as alkylated phenanthrenes and tetrahydrophenanthrenes. Both groups of compounds appear to be in dicative of a strong bacterial input to the sedimentary organic matter . (C) 1997 Elsevier Science Ltd.