Calcrete profiles in the Eyam Limestone (Carboniferous) of Derbyshire: petrology and regional significance



Calcrete profiles (caliche) have been recognized in the Eyam Limestone from the Lower Carboniferous in the area around Monyash, Derbyshire. They occur at the top of the flank facies surrounding carbonate-mud buildups (‘knoll reefs’). Four units make up the complete profile. These are from base to top: (1) grain-supported sediment with rhizocretions, (2) matrix-supported sediment with alveolar texture, (3) pelleted calcrete, (4) laminar calcrete. Commonly one or more units are missing from the profile. Calcretes indicate subaerial exposure. The carbonate buildups of the Eyam Limestone were completely exposed soon after deposition, requiring a fall in sea-level probably in excess of 10 m. This discovery demands a review of previous regional palaeoenvironmental studies.