Marine karstic infillings: evidence of extreme base level changes and geodynamic consequences (Paleocene of Languedoc, south of France)

Abstract

Abstract Late Jurassic platform carbonates of Languedoc (southern France) are deeply incised by Late Miocene canyons, allowing the observation of karst systems filled with sediments containing evidences of marine origin. Field and structural relationships as well as new biostratigraphic data (planktonic foraminifera and calcareous nannofossils) provide a Latest Cretaceous-Earliest Paleocene age for the major karstification and a Paleocene (Danian-Selandian) age for the sedimentary filling. The ≥ 350 m vertical extent of this karst system and its subsequent marine filling gives a minimum amplitude for the base-level variation responsible for the karstification and then the marine flooding events. The observations suggest that at least, two marine successive events occurred in the Late Danian then in Selandian time. The large amplitude of base level is not in agreement with eustatic sea-level change, and the rate of base-level change is too fast for tectonic uplift and subsidence within the tabular, poorly deformed studied area. We propose a model of a silled endoreic basin, which was dessiccated and karstified over hundreds of meters, when it was disconnected from the World Ocean, and later suddently transgressed by the Paleocene sea and the karst flooded, when the bounding sill was submerged. Such a model is similar, although with significant differences, with the later Messinian-Zanclean event that affected the Mediterranean realm.