Abstract Field studies and review of the nineteenth century literature have led to a new model for the conditions of formation of Senonian phosphorites of the Anglo-Paris Basin. All Chalk phosphorites are floored by a well developed hardground Its formation was a direct result of increased current activity which eroded troughs of up to I km in length within the underlying white chalk and also produced by winnowing a coarser sediment more susceptible to sea-floor lithification. A prolific biota developed within these cuvettes This biota concentrated phosphorus from sea water and produced an organic rich substrate predominantly of fecal pellets suitable for early diagenetic phosphatization. The increase in current activity and the ubiquitous nature of shiny phosphate veneers which are of potential algal origin suggest that the late Santonian to early Campanian was a period of shallowing of the Chalk sea These distinctive sediments may be related to major changes in oceanic circulation.