The Silty Beds are a Lower Albian tidal flat deposit with sediments of the intertidal and subtidal zone. They are interpreted as the deposit of a sheltered shore, near an estuary mouth, with low wave energy and low tidal range. The Silty Beds are a well-bedded series of sands, silts and clays with minor ironstone and intermittent carbonate lenses occurring towards the top of the unit. These beds include carbonaceous material, pyritized, glauconitic and other trace fossils as well as glauconite-rich sands. Some beds are highly bioturbated, while others show only moderate burrowing. Where there is no burrowing activity, detailed sedimentary structure has been preserved, such as fine parallel-lamination, cross-stratification, fine ripple lamination and abundant flaser bedding. The environment of deposition is interpreted as tidal sand and mud flats with intermittent freshwater and brackish lagoons. Ironstone development was probably early diagenetic. The top of the succession culminates in emergence and erosion of the topmost ironstone. Cavities, thus formed, were subsequently infilled with a bioclastic limestone (the Shenley Limestone) during the transgression leading into the deeper water marine clays of the Gault.