The response of shallow-water sequences to oceanic anoxic event 2 and
mid-Cenomanian events 1a and 1b was investigated along the west African
margin of Morocco north of Agadir (Azazoul) and correlated with the
deep-water sequence of the Tarfaya Basin (Mohammed Beach) based on
biostratigraphy, mineralogy, phosphorus and stable isotopes. In the
deeper Mohammed Beach section results show double peaks in delta
13C(org) for mid-Cenomanian events 1a and 1b (Rotalipora reicheli
biozone, lower CC10a biozone), the characteristic oceanic anoxic event 2
delta 13C excursion (Rotalipora cushmani extinction, top of CC10a
biozone) and laminated (anoxic) black shale. In the shallow environment
north of Agadir, a fluctuating sea-level associated with dysoxic,
brackish and mesotrophic conditions prevailed during the middle to late
Cenomanian, as indicated by oyster biostromes, nannofossils, planktonic
and benthonic foraminiferal assemblages. Anoxic conditions
characteristic of oceanic anoxic event 2 (for example, laminated black
shales) did not reach into shallow-water environments until the maximum
transgression of the early Turonian. Climate conditions decoupled along
the western margin of Morocco between mid-Cenomanian event 1b and the
Cenomanian-Turonian boundary, as also observed in eastern Tethys. North
of Agadir alternating humid and dry seasonal conditions prevailed,
whereas in the Tarfaya Basin the climate was dry and seasonal. This
climatic decoupling can be attributed to variations in the Intertropical
Convergence Zone and in the intensity of the north-east trade winds in
tropical areas.