Isabel Urbat

Oceanic Anoxic Event (Oae) 1b: High Resolution Geochemical Studies, Mazagan Plateau and the Vocontian Basin Isabel Urbat

The Cretaceous OAE 1b is one of the major perturbations of the global carbon cycle. It is documented in Albian deposits from the Atlantic regions as well as in regions of the Western Tethys. High-resolution geochemical profiles show, that the perturbation of the carbon cycle occurred synchronously in the oceanic- and atmospheric carbon reservoirs. This is indicated by the stable isotopic composition of biomarkers for terrestrial higher plant waxes and marine algal lipids. The climate system in the tropics responded with a rapid rise in sea surface temperature (SST). Climate proxies indicate a shift towards more humid climate conditions. The effects of this major perturbation of the climate had also consequences for the biota. At the Mazagan Plateau the organic matter production increased even though the upwelling weakened probably due to an increased influx of nutrients from the adjacent African Continent. The bioproduction of the Vocontian Basin shifted towards bacterial dominated communities. These major perturbations of the carbon cycle had complex effects in different regions of the Lower Albian tropics.