Caracterización paleoambiental mediante biomarcadores de las sucesiones lacustres oligocénicas superiores (Formación Mequinenza) del sector SE de la cuenca del Ebro (NE de España)
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[1] Universitat de Barcelona
Universitat de Barcelona
Barcelona, España
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[2] Universitat Politècnica de Catalunya
Universitat Politècnica de Catalunya
Barcelona, España
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- Localización: Geotemas (Madrid), ISSN 1576-5172, Nº. 2, 2000 (Ejemplar dedicado a: IV Congreso del Grupo Español del Terciario (Tremp, 19-21 septiembre, 2000)), págs. 47-50
- Idioma: español
- Enlaces
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Resumen
The Late Oligocene Mequinenza Formation (SE Ebro Basin, NE Spain) was deposited in shallow, low gradient ancient lacustrine zones, which evolved under subtropical, warm climatic regime and closed drainage conditions. Limestones, mudstones and thin coal seams are the most characteristic deposits in these successions. Lacustrine water solute concentration underwent changes during the alternative high and low stand episodes, with lacustrine waters ranging mainly from fresh to oligosaline. Non sulphurised (NSC) and sulphurised (OSC) biomarkers record primary contributions of aquatic and terrestrial higher plants, bacteria and algae. Higher plants biomarkers were recorded mostly as normal, non sulphurised lipids. The biomarker assemblages suggest that the lacustrine system was eutrophic and the water column was poorly oxigenated and sometimes stratified as shown by gammacerane occurrence. Both organic petrological data and biomarker record make evident intense bacterial degradation of the organic matter and the coexistence of well developed anaerobial sulfur and methane-carbon cycles. Intense reworking of organic matter by sulphate reducing eubacteria gave rise to organo sulphurised compounds (OSC). Among them, linear thiols are new biomarkers, which probably were generated by the early incorporation of sulphur into functionalised precursors (e.g: alkanols) resulting from bacterial activity.
