Dinoflagellate-based age control and biostratigraphic correlations of the Eocene and Oligocene (Lutetian-Chattian) sediments in the El Habt tectonic Unit, western External Rif Chain, Morocco (NW Africa)

This study aims to refine the age of sediments from the region of Ksar El-Kebir in the El Habt tectonic Unit, northwestern Morocco (southwestern Tethys) and establish biostratigraphic correlations between the sections studied, and also with other sections in the northerrn latitudes, particularly from the Mediterranean region and northwestern Europe, based on dinoflagellate cysts (dinocysts). The study is carried out on predominantly marly successions of the Ennayemiyene I, Ennayemiyene II and Bourkha sections, which were assigned previously to the Upper Cretaceous-Eocene interval in the geological map of the Rif Chain (1/500,000), based on lithostratigraphic correlations with other previously dated sections in the western External Rif. The palynological investigations of these three Tethyan sections revealed the presence of well-preserved and dinocyst-rich palynomorph assemblages. These investigations allowed for the recognition of the Bartonian-Priabonian interval (Eocene) in the Ennayemiyene I section, the Rupelian-Chattian interval (Oligocene) in the Ennayemiyene II section and the Priabonian-Rupelian interval (upper Eocene-lower Oligocene) in the Bourkha section. Biostratigraphic correlations have been established between these sections and also with the sections of Tattofte and Ibn Batouta, also located in the western External Rif, based on dinocysts. Correlations were also possible with biostratigraphically well-calibrated sections, mainly from the North Sea Basin and from other Tethyan regions, including the Priabonian stratotype, the Global Stratotype Section and Point (GSSP) for the base of Rupelian and the GSSP for the base of Chattian in Italy. Furthermore, we recognized dinocyst zones and subzones, previously defined in the Bartonian-Chattian interval of these sections, such as the Wetzeliella simplex (Bartonian), Schematophora speciosa Zone (Priabonian), Reticulato-sphaera actinocoronata, Hystrichokolpoma pusillum and Corrudinium incompositum zones (Rupelian), and Distatodinium biffii Zone (Chattian) with its Svalbardella cooksoniae and Caligodinium pychnum subzones.

Automated summary

This study provides refined age estimation of sediments in northwestern Morocco and establishes biostratigraphic correlations with other regions, contributing to the understanding of the regional geological development.