Campanian to Danian dinoflagellate cyst assemblages from the southwestern Tethyan margin (Tattofte section, western External Rif, Morocco): Biostratigraphic and paleobiogeographic interpretations

Abstract

A palynological study of the Upper Cretaceous–lower Paleocene outcrop section at Tattofte (westernmost External Rif, Morocco) has produced a well-preserved palynological assemblage rich in dinoflagellate cysts (dinocysts). For the first time, these assemblages have allowed us to determine the age of this section, to highlight a new Cretaceous–Paleogene boundary, and to make paleobiogeographic interpretations. The samples analyzed yielded 209 dinocyst species and 81 biostratigraphic dinocyst events (first occurrence, or FO, and last occurrence, or LO). We recognized the upper Campanian based on the FOs of Areoligera coronata, Areoligera reticulata, Areoligera senonensis, Cerodinium diebelii and Andalusiella mauthei subsp. mauthei, as well as the LOs of Batiacasphaera solida, Odontochitina costata, Odontochitina porifera, Sentusidinium eisenackii, Trichodinium castanea and Trithyrodinium suspectum. The lower Maastrichtian is determined by the FOs of Isabelidinium bujackii, Palaeocystodinium golzowense and Trithyrodinium evittii, and by the LO of Alterbidinium acutulum, and the upper Maastrichtian is recognized primarily by the FOs of Cerodinium speciosum subsp. speciosum, Disphaerogena carposphaeropsis, Glaphyrocysta perforata and Manumiella seelandica and the LO of Dinogymnium spp. The Danian is recognized on the basis of the FOs of several taxa, including Carpatella cornuta, Danea californica and Senoniasphaera inornata. The succession of the dinocyst events in the uppermost part of the studied interval has revealed a relatively complete record across the Cretaceous–Paleogene boundary. The Cretaceous–Paleogene boundary coincides with a 8 cm-thick reddish layer, which resembles those observed previously in the Cretaceous–Paleogene boundary reference sections in the Mediterranean area, most notably the Cretaceous–Paleogene boundary stratotype at El Kef (Tunisia). The upper Campanian dinocyst assemblage indicates a subtropical to temperate setting, while the Maastrichtian and lower Danian assemblages indicate a subtropical to warm temperate setting. The incursion of a few higher latitude cold-water dinocyst species in these provinces during the latest Campanian and around the Cretaceous–Paleogene boundary may suggest a southward migration of these species, probably related to short cooling episodes and ocean circulation.