Archaic-style shell concentrations in brackish-water settings: Lower Cretaceous (Wealden) examples from southern England

Shell pavements, shelly gutter and scour fills, and coquinas are described from brackish-water mudrock facies of the southern English Lower Cretaceous (Wealden) successions. These shell concentrations are consistently thin, reflecting small shell sizes, conservative molluscan life-modes, high net deposition and low levels of bioturbation in lacustrine and lagoonal environments. In biostratinomic terms the shell concentrations are of archaic aspect and similar to other occurrences within Mesozoic mudrock formations ascribed to ‘stressed’, brackish-water settings. As such, Wealden mud-dominated brackish-water settings are identified as a biostratinomic ‘window’ for generation and preservation of archaic-style shell concentrations.