APPRAISAL OF PYROLYTIC TECHNIQUES ON DIFFERENT FORMS OF ORGANIC-MATTER FROM A CRETACEOUS BASEMENT IN CENTRAL SPAIN

Pyrolytic techniques were used to characterize three different forms o f fossil organic matter in Cerro de Ia Mesa (an important Cretaceous p aleobotanic basement in Central Spain): two kerogens isolated from car bonaceous marls, and from lignitiferous layers, and well-preserved rem ains of the fossil Gymnosperm. Frenelopsis oligostomata. By convention al flash pyrolysis the Frenelopsis remains released mainly alkyl-subst ituted phenols and polyaromatic compounds, whereas the organic matter from the lignitiferous layer is dominated by phenols and that from the carbonaceous marls by polycyclic and aliphatic compounds. Pyrolysis-t hermochemolysis alkylation in the presence of tetramethylammonium hydr oxide (TMAH) allowed the detection of additional diagnostic compounds, such as series of methylated fatty acids, benzenecarboxylic and pheno lic acids, which revealed further differences between the three materi als studied. The chemical characterization of the organic matter in ad dition to the micropalaeontological study suggests that the Frenelopsi s remains consist mainly of heavily altered lignin and cuticular lipid biomacromolecules, whereas the materials from the lignitiferous layer s and the carbonaceous marls correspond to intermediate coalification stages of woody plants, the latter showing the greatest degree of sele ctive preservation of,aliphatic structures. The comparison of the abov e results with those obtained by thermochemolysis suggests that the la tter technique produces independent and complementary reactions to con ventional pyrolysis, providing additional information to an extent whi ch depends mainly on the polyalkyl and oxidized character of the sampl e. (C) 1998 Elsevier Science Ltd. All rights reserved.