The mineralogy and origin of interbedded clay wayboards in the Lower Carboniferous of the Derbyshire Dome

Interbedded clays, or clay wayboards, from the Lower Carboniferous Limestones of Derbyshire and Staffordshire, are discussed in terms of their geological relationships, textural features and mineralogy, and comparison is made between these clays and other interbedded argillaceous materials from the area. It is concluded that the clay wayboards are the argillation products of contemporaneous volcanic ashfalls, and lie within the definition of K‐bentonites. Stratigraphical and palaeogeographical aspects of clay wayboard distribution are briefly discussed, and it is shown that despite the probable widespread extent of individual clay horizons they are only of limited value for the purposes of correlation.