SHALLOW-WATER FACIES DURING THE CENOMANIAN-TURONIAN ANOXIC EVENT - BIO-EVENTS, ISOTOPES, AND SEA-LEVEL IN SOUTHERN GERMANY

The sediments, palynofacies, macrofossils, planktic and benthic forami nifera, radiolaria, ostracoda, stable carbon and oxygen isotopes (whol e rock and inoceramid prisms) of the hemipelagic Eibrunn Marls at the northern Tethys margin were studied in the Muhlberg section of the Reg ensburg area, southern Germany. The biotas reveal extinction and origi nation events that are known elsewhere, although other species may be involved. The palaeontological evidence suggests a control of global c hanges on the biotas (macroevolutionary impact of the Oceanic Anoxic E vent), rather than changes in the local environmental conditions. Carb on isotopes of inoceramid prisms do not reflect the standard isotope s tratigraphy; differences in Vital effects between Inoceramus and Mytil oides probably dominate the isotopic composition. Ridge facies (conglo merates, cliffs, erosional platforms) in Saxony (southeastern Germany) provide evidence of the timing of sea-level changes. The partial deri vative(13)C values increase through the section representing a late Ce nomanian, long-term sea-level rise, and have a maximum when widespread flooding occurs. Marine erosion (nutrient mobilization) during a long -term sea-level highstand that exceeded previous highstands may have s upported higher productivity during the Cenomanian-Turonian Oceanic An oxic Event, and potentially during other widespread anoxic events in t he Mesozoic. Organic matter remineralization may have lead to more aci dic bottom waters that reduced carbonate preservation, and amplified t he partial derivative(13)C excursion through carbonate disolution. (C) 1996 Academic Press Limited