EXTRACTABLE AND BOUND FATTY-ACIDS IN-CORE SEDIMENTS FROM THE NORDLINGER-RIES, SOUTHERN GERMANY

Gas chromatography (g.c.) and gas chromatography-mass spectrometry (g. c.-m.s.) analyses of fatty acids directly extracted by organic solvent s from five sulfur-rich lacustrine sediments in the Nordlinger Ries co mprise several homologous series. Saturated normal monocarboxylic acid s (C-9-C-33) were the dominant series, while isoprenoid acids (C-14-C- 21, except C-18), iso- (i) and anteiso (ai)-acids (C-11-C-18), hopanoi c acids (C-30-C-33) and monounsaturated acids (C-16:1 and C-18:1) were minor constituents. Moreover, 10-oxoacids (n-C-16 and n-C-18) were id entified in abnormally high amounts in the three samples from well NR- 10. Base hydrolysis of kerogen concentrates and extractable polar frac tions liberated, in addition to the fatty acid constituents belonging to the compound classes mentioned above, steroidal acids (C-28-C-31) a nd alpha,omega-dicarboxylic acids (C-7-C-28). The results are discusse d in terms of qualitative and quantitative variations of the fatty aci ds in the free and bound lipid fractions. The high concentrations of f atty acids in the bitumens are attributed to early diagenesis. The car bon number distributions of n-alkanoic acids in the free and bound fra ctions indicate a major contribution of autochthonous sources in sampl es from well NR-10, and a mixed contribution of both autochthonous and allochthonous sources in samples from well NR-30. Bacterial biomarker s, including extended hopanoic acids and i-/ai-branched acids are more significant in the bound lipid fractions. The results further support previous suggestions of a broad similarity between the structure of a sphaltenes and kerogen derived from the same source rock. Finally, the data confirm the extremely mild thermal history of the Nordlinger Rie s sediments.