Late Cretaceous marine flooding and installation of a mangrove swamp environment in the Prebetic (Betic External Zones, SE Spain)

Abstract

AbstractThe Cenomanian (Upper Cretaceous) sedimentary rocks of the External Prebetic (Betic Cordillera) in the Sierra de Montearagón-Carcelén (SE Spain) record the transgression and flooding of continental deposits and the subsequent development of an inner shallow carbonate platform. The transgressive surface is densely colonized by infaunal trace-makers of the Glossifungites ichnofacies (Gastrochaenolites and Glossifungites), which indicate sediment starvation and erosion as well as colonization of a firmground. The first deposits were a thick calcarenite bar (2 to 11 m) with large-scale cross-bedding pointing to a high-energy environment in a shallow carbonate platform. The record of the Rosselia ichnofacies (Rosselia and Ophiomorpha) confirms a loose sandy bottom under high-energy conditions. The overlaying stratigraphic succession is characterized by subtidal laminated marly limestones and intertidal limestones with rhizoliths interpreted as a mangrove swamp environment. These facies are organized in shallowing-upwards sedimentary sequences. An episodic high-energy event is represented by bivalve-rich limestones representing shell lags of disarticulated valves. This facies could be related to a climatic perturbation evidenced by a negative excursion of δ13C and δ18O. The successive shallowing-upwards sedimentary sequences persisted thanks to subsidence related to the tectonically controlled depocenters located in the south of the Sierra de Montearagón-Carcelén. The differential subsidence, evidenced by the increasing thickness towards the south of the sector under study, suggests the activity of listric faults that controlled the depocenters. This is the first report of the Cenomanian transgression in this sector of the External Prebetic and the first record of the very extensive mangrove swamp that developed close to the land that emerged.