Carine Lézin

The Upper Cenomanian–Lower Turonian Anoxic Event in the Carbonate Platform of the Pre-African Trough, Morocco

During the late Cenomanian–early Turonian, the environment of the carbonate platform of the Pre-African Trough, Morocco, ranged from a peritidal zone/inner ramp to a deep, open platform. Four depositional sequences are recognized, and the major drowning phase appeared after the Cenomanian–Turonian boundary. Oceanic Anoxic Event 2 (OAE2) is well identified by the δ13C excursion, even in shallow water. Chemical and biological disturbances are recorded during the Cenomanian–Turonian anoxic event on the carbonate platform, with dysoxic conditions in the outer-ramp environment (west of the platform). The displacement of these dysoxic waters was controlled by sea-level variations. After OAE2, dysoxic conditions were linked to high productivity, following a humidification of the climate, which increased chemical weathering; these conditions applied to the whole platform and were the cause of a biological crisis.