El horizonte radiolarítico-bituminoso del límite CenomanienseTuroniense en la Zona Subbética

Resumen

A well defined stratigraphic interval, made of dark bituminous pelites and radiolarites, and dated as the Cenomanian-Turonian transition by calcareous nannofossils, planktonic foraminifers and radiolarians, is present in different Subbetic realms. It represents the local expresión of the OAE2. Radiolarian faunal turnover; occurred within the anoxic event and detected in all studied successions, allow a detailed correlation. The expansion o f the oxygen minimum zone during the Cenomanian-Turonian boundary affected all the Subbetic Zone, but different features are observed depending on the paleogeographic location. External Subbetic successions are thicker and more calcareous, with less radiolaritic levels, because they were located nearer to the continent. Median Subbetic succesions are more siliceous than those of the External Subbetic, but less than in the Penibetic, and intercalate frequent calcareous turbidites and breccias after erosion of jurassiccretaceous submarine reliefs rised by local tectonic movements. The Penibetic was the most distal and starved realm, with low terrigenous input and very reduced sedimentation, and constituted an intrabasinal high inherited from previous periods that was affected by deep bottom currents that winnowed clay fraction and contributed to form thin silty-sandy radiolarian accumulations