Late Miocene-early Pliocene Palaeoenvironmental Changes in the Western Rifian corridor (NE Morocco)

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Abstract The Gharb basin constitutes the western part of one of the main corridors that connecting the Mediterranean Sea and the Atlantic Ocean during the Upper Miocene. This basin is characterized by a continuous sedimentary filling from the Upper Tortonian to the Pliocene, likely to record environmental information useful for the reconstruction and evolution of the marine environment before and during the Messinian salinity crisis.Based on an integrated study of the planktonic and benthic foraminifera of borehole DF 101 (Gharb basin, Morocco), the objective of this work is, on the one hand, to clarify the biostratigraphic framework of the sediments studied and, on the other hand, to make a further contribution to the reconstitution and evolution of the marine environment during the Upper Neogene in the Gharb Basin.The high-resolution biostratigraphic study of borehole DF 101 revealed the succession of eight bioevents and characterized the Upper Tortonian, Messinian and Zanclean.The composition of benthic foraminiferal assemblages, paleoecological indices and statistical analysis show an evolution of depositional conditions in terms of bathymetry and oxygen content from the Upper Tortonian to the Pliocene.The Upper Tortonian is marked by an association of very diversified benthic foraminifers that characterizes the upper bathyale, the estimated paleobobathymetry is over 800 m and the medium is well oxygenated. Messinian marl deposits are characterized by a decrease in bathymetry, and a reduction in the rate of oxygenation. While during the Lower Pliocene, the medium becomes relatively deeper, higher bathyal type and normal oxygenation rate.

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