Middle Eocene to early Oligocene dinoflagellate cyst biostratigraphy and paleoenvironmental interpretations of the Ben Attaya section at Taza, eastern External Rif, Morocco

Abstract

The palynological study was carried out on middle Eocene to early Oligocene sediments from the Ben Aattaya section, located in the Taza region, eastern External Rif, northeastern Morocco. The palynological content is dominated by dinoflagellate cysts (dinocyst), while spores and pollen are rare. Very known dinocyst event markers were used for dating the Ben Attaya section. The first occurrences (FO) of Cerebrocysta bartonensis, Glaphyrocysta semitecta, Lentinia serrata, Operculodinium divergens indicate the Bartonian. The FOs of Deflandrea heterophlycta, Schematophora speciosa, Stoveracysta ornata were used to recognize the Priabonian. While the FOs of Chiropteridium lobospinosum and Wetzeliella gochtii, as well as the last occurrences (LO) of Achilleodinium biformoides, Charlesdowniea coleothrypta subsp. coleothrypta, Enneadocysta pectiniformis, Glaphyrocyst semitecta, Hemiplacophora semilunifera, Lentinia serrata, Operculodinium divergens, Rhombodinium perforatum, Schematophora speciosa and Stoverocysta ornata highlight the Rupelian. The changes in relative abundances of selected dinocyst groups and sporomorphs (pollen and spores) suggest a lagoonal to coastal inner neritic marine environment during the Bartonian and Priabonian, which was interrupted by a short phase of outer neritic conditions at the basal part of the section and ended by a marked decrease in the sea level, probably due to a regression during the Priabonian. The Rupelian deposits indicate a middle neritic marine environment marked by a progressive rise during the transgression.