Paleoenvironmental Approach on the Lower Cretaceous Sequences of Areia do Mastro (Cabo Espichel, Southern Portugal)

This palaeontological study focuses on the sedimentology and palaeofauna of Areia do Mastro locale in Cabo Espichel (Sesimbra, south of Lisbon). Two main geological formations are identified in Areia do Mastro: the Areia do Mastro Formation and the Papo-Seco Formation. We report herein the fossilized vertebrate and invertebrate remains from the basal deposits (marls, sands and gravels) of Papo-Seco Formation assigned to Lower Barremian (Lower Cretaceous). The sedimentological analysis and identified palaeofauna indicated a changing environment with important biological and ecological aspects. Extensive periods of sea level fluctuations and subsequent transgressive marine episodes had as a result the continental infralittoral internal platform to be gradually replaced by a lagoon, as revealed from the fossil remains embodied in the sediments during the formation of the afore mentioned sedimentary sequences.