Biostratigraphy, palaeoenvironments and palaeogeography of the Cretaceous–Paleogene succession in the Oudiksou Basin, Central Middle Atlas of Morocco

We describe the biostratigraphy, palaeoenvironments and palaeogeography of a Cretaceous–Paleogene succession in the Oudiksou Basin of the Middle Atlas region, Morocco. Facies analysis allows the recognition of depositional units that record a complex transition from marine to continental environments. Possible Late Maastrichtian phosphate-bearing beds comprise shallow marine facies and contain an elasmobranch-rich fauna. These beds are overlain by ?Late Maastrichtian marl facies deposited within a continental lacustrine setting, which contain rare dinosaur remains (teeth and eggshell fragments). The lowermost Paleocene succession (likely Danian in age) consists of red conglomerates and gypsiferous facies interpreted as fluvial and sabkha deposits, respectively. Additionally, we document coastal facies of Thanetian or Ypresian age that contain microelasmobranchs and a mammalian fauna. The Cretaceous–Paleogene sedimentary series shows considerable lateral thickness variations, controlled by syn-sedimentary tectonics, and sea-level changes, and reflects the paleogeographic position of the Oudiksou Basin at the margin of the Atlantic Gulf. Our study provides a comprehensive biostratigraphic and lithostratigraphic synthesis of the Cretaceous–Paleogene transition along the northwestern Gondwanan margin, and the Oudiksou Basin thus emerges as a key locality for investigating the K–Pg boundary interval and associated biotic turnover within a continental depositional framework, one of the very few such records preserved in Africa.