Siderite- and Calcite-bearing Concretionary Nodules in the Lias of Yorkshire

Abstract Nodules containing siderite and calcite in the Yorkshire Lias have been studied quantitatively using petrographic, X-ray and chemical methods. Ankerite is recorded from the Lias for the first time. It is shown how the relative abundance of early diagenetic siderite and calcite correlates with sandiness of the sediment and provides an index of environmental change.