Organic geochemical evidence for environmental changes since 34,000 yrs BP from Lago di Mezzano, central Italy |
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| Authors: | Heinz Wilkes Antje Ramrath Jörg FW Negendank |
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| Institution: | (1) Institut für Erdöl und Organische Geochemie, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany;(2) GeoForschungsZentrum Potsdam, Projektbereich 3.3, Telegrafenberg A26, 14473 Potsdam, Germany |
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| Abstract: | The composition of organic matter in a 34,000 yr sediment profile from Lago di Mezzano, central Italy, was investigated by bulk organic geochemical methods and analyses of lipid distributions. High relative amounts of long-chain fatty acids, n-alkanols and n-alkanes from the cuticular waxes of terrestrial plants in the Late Pleistocene sediments indicate a high relative proportion of allochthonous organic matter. In the Holocene sediments higher relative amounts of algal and bacterial lipids are detected which indicate a higher relative contribution of autochthonous organic matter. These results are corroborated by Hydrogen Index (HI) and Oxygen Index (OI) values from Rock-Eval pyrolysis which show a good general correlation with the TOC content indicating significant variations of the organic matter composition. Variations of HI and OI observed for different lithozones of the sediment profile can be related to environmental and climatic changes throughout the lake history. Both bulk organic geochemical and molecular data point to a good overall preservation of the organic matter. |
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| Keywords: | Lago di Mezzano Hydrogen Index lipids autochthonous organic matter allochthonous organic matter |
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