Sediment-filled cavities in the Morecambe Bay karst (UK): Examples from the Warton and Silverdale area

Various types of sediment-filled natural cavities are exposed in abandoned haematite and copper mines in Carboniferous limestones around Morecambe Bay, northwest England. They range in age from pre-mineralization through to Pleistocene though, because the date of the mineralization is disputed, it has been impossible to propose a confident chronology for many of them. Re-examination of two sites in the eastern part of the district, together with recently published results that point to a Mid Triassic age for the mineralization episode, now make it possible to propose a Neogene age for at least one example. Other, pre-mineralization, cavities and infill sediments probably date from the period of denudation that removed Carboniferous strata in this area prior to deposition of Permo-Triassic red beds. Some unconsolidated sediments are assigned on lithological evidence to being Pleistocene glacial deposits.