Palaeoecology of foraminiferid assemblages across late Cretaceous phosphogenic cycles, south west Atlas, Morocco
Abstract Major phosphogenic episodes throughout geological history appear to lie in close proximity to periods of extensive faunal turnover. Late Cretaceous phosphogenic deposits of the southwest Atlas, Morocco, comprise part of the great Tethyan phosphogenic belt stretching across North Africa to the middle east. The palaeoenvironmental conditions under which these Moroccan deposits formed have been investigated largely through the interpretation of their associated foraminiferid plankton and benthos. Changes in the composition of foraminiferid assemblages across phosphogenic features suggest a close relationship between phosphogenesis, oceanic upwelling and the impingement of cold, oxygen depleted waters onto a broad continental shelf environment. Such a scenario is believed to be followed by high mortality in specialised faunal assemblages and the accumulation of organic material on hard lithified surfaces. The erosion and redistribution of hardground and biogenic remanie deposit has been associated with late Campanian tectonic disturbances in the Atlas mobile belt. These events appear to be cyclic occuring throughout the lower Maastrichtian of southern Morocco.