Palaeoenvironmental significance of storm coquinas in a Lower Cretaceous coastal lagoonal succession (Vectis Formation, Isle of Wight, southern England)

Abstract

Thin bioclastic limestone beds (‘coquinas’) in the Vectis Formation (Wealden Group, Lower Cretaceous) of the Isle of Wight, southern England, exhibit a range of biofabrics and internal stratigraphies. These features are attributed to both simple and complex storm deposition of allochthonous biogenic and siliciclastic materials in coastal lagoons and on adjacent mudflats. These modes of deposition facilitated preservation of dinosaur trackways, desiccation cracks, shallow-tier trace fossils and in situ bivalve colonies through rapid burial. The coquinas thus preserve a record of surficial muds, commonly lost through reworking. The principal components of the coquinas comprise dispersed elements from within the argillaceous ‘background’ facies. Some of these beds are laterally traceable for up to 27 km, providing the foundations for a high-resolution event-stratigraphic framework.