Environmental Reconstruction of the Mediterranean Basins in NE Morocco During the Messinian

The peripheral sedimentary basins of Boudinar and Melilla-Nador located on the Moroccan Mediterranean coast have known important environmental changes during the Messinian. They are characterized by marl-diatomite alternation including cineritic intercalations. Sediments from four sections, located respectively in the Boudinar Basin and the Melilla-Nador Basin, were analysed in order to reconstruct the marine and continental environments during the pre-evaporitic Messinian. The detailed micropalaeontological and palynological study using planktonic foraminifera, pollen and dinocysts has allowed, on the one hand, to specify the chronostratigraphic context of these marno-diatomite alternations and, on the other hand, to characterize the paleoenvironmental evolution. From the detailed study of planktonic foraminiferal associations and previous data, the base of the marno-diatomic alternations in these basins is located around 7.24 Ma and the top is dated at 6.08 Ma. During the pre-evaporitic Messinian, between 7.24 Ma and 6.52 Ma the marine environment is relatively open and probably submitted to the action of upwellings. It was neritic tending to oceanic with warm surface water conditions. The vegetation was dominated by herbs that populate the plain, thermophilic trees that colonize the middle altitude, while the Avicennia mangrove, megatherm element, was developing on the coast. The climatic conditions were warm subtropical and dry at low altitude. After 6.35 Ma, the degradation of marine conditions and the trend towards a proximal environment start. The continental environment showed a less diversified flora and a landscape more open with herbaceous plants, reflecting the same climatic conditions but not much warm and more dry than before.