Bartonian to Priabonian dinoflagellate cyst biostratigraphy and paleoenvironments of the M'karcha section in the Southern Tethys margin (Rif Chain, Northern Morocco)

Palynological analyses were performed on the Eocene sediments of the M'karcha section, which is located in the Taza region, structural Tsoul Unit, eastern External Rif (northeastern Morocco). The palynological content of this section is composed essentially of well-preserved and diverse dinoflagellate cyst assemblages, allowing detailed taxonomic determinations, age assignments, biostratigraphic correlations and paleoenvironmental interpretations. Other palynomorphs, such as spores, pollen grains and foraminiferal linings, are rare and therefore, not taxonomically determined up to the genus level. 131 dinoflagellate cyst species were identified. Age assignments are based on dinocyst bioevents, considered previously as potential biostratigraphic markers of the Bartonian and Priabonian, including the lowest occurrences (LOs) of Glaphyrocysta semitecta, Impagidinium dispertitum, Rhombodinium perforatum, Cooksonidium capricornum, Stoveracysta ornata, Stoveracysta sp. 2 of Brinkhuis and Biffi (1993) and LO and highest occurrence (HO) of Schematophora speciosa. The quantitative palynological analyses, based mainly on dinoflagellate cysts through the M'karcha section revealed an inner neritic, generally lagoon, environment with a low productivity, alternated with short episodes of the open marine influence. •Bartonian to Priabonian dinoflagellate biostratigraphy in the External Rif is presented.•Age precisions of the M'karcha section are provided based on dinocyst marker events.•Biostratigraphic correlations with Mediterranean regions and North Europe are suggested.•An inner neritic, generally lagoon, environment with a low productivity is recognized.