The Paleocene–Eocene Thermal Maximum (PETM) interval in the southwestern Mediterranean Tethys at Morocco: New data from a high-resolution study of dinoflagellate cysts and palynofacies in the Rif Chain

Palynological research, carried out in the Paleocene–Eocene transition of the Sekada section, Tangier Unit (western External Rif, northwestern Morocco), revealed the presence of a palynological content composed essentially of dinoflagellate cysts (dinocysts), phytoclasts and amorphous organic matter (AOM). Their qualitative and quantitative analyses allowed a detailed biostratigraphic interpretation, a reconstruction of the paleoenvironment and paleoclimate and identification of the Paleocene–Eocene Thermal Maximum (PETM) interval in the Sekada section.

Thanetian and Ypresian ages, previously assigned respectively to the grey-brown marls and the marly limestones in the studied section are here revised based on several marker dinocyst events. Acmes of the subtropical dinocyst Apectodinium spp. (in particular, Apectodinium homomorphum), recorded along the analyzed interval, represent a response to the global warming of the PETM, and therefore support the assignment of this interval to the Paleocene–Eocene transition.

Quantitative analyses of the main constituents of kerogen (dinocysts, phtoclasts, AOM) and selected dinocyst groups, which are previously considered in the literature as environmental markers, generally suggest a proximal (coastal eutrophic) depositional environment. Furthermore, quantitative fluctuations in the heterotrophic dinocyst Apectodinium and open marine autotrophic dinocysts versus total dinocysts, and in phytoclasts, AOM and palynomorphs versus total kerogen appear to be controlled by fluctuations in terrestrial inputs, which are most likely related to climate changes.