Lithostratigraphy and biostratigraphy of the Hunstanton Formation (Red Chalk, Cretaceous) succession at Speeton, North Yorkshire, England

Abstract

SUMMARY The Hunstanton Formation (Red Chalk), as interpreted here, is 24 m thick at Speeton and is divided into five members (Queen Rocks, Speeton Beck, Dulcey Dock, Weather Castle and Red Cliff Hole), each of which is characterized by a distinctive lithology. Above the Red Chalk, in the Ferriby Chalk Formation, a further member is established (Crowe’s Shoot Member) which extends the succession up to the regionally important marker, the First Inoceramus Bed. The lithological boundaries between the lowest three members of the Red Chalk are close to important changes in the belemnite assemblages and consequently belemnites, which are abundant, provide the most suitable fossils for placing small sections of Red Chalk within the lithostratigraphical scheme. The distribution of the most important macrofossils is described and used to suggest a correlation of the Red Chalk succession at Speeton with the standard ammonite zones and subzones established in southern England. This demonstrates that Red Chalk deposition began in early Mid-Albian times at Speeton, similar to other sections in north-east England (e.g. South Ferriby and Hunstanton), and the transition to ‘white chalk’ deposition occurred during the earliest Cenomanian. The Albian-Cenomanian boundary is recognized using the carbon isotope signature and compared with various biostratigraphical markers previously used for the Albian-Cenomanian boundary. A comparison of the Red Chalk succession between Speeton, South Ferriby and Hunstanton shows a number of regionally important erosional/flooding surfaces, and these have also been recognized in southern England. Three new species of brachiopod (Concinnithyris microsubundata sp. nov., Nerthebrochus nosetrapensis sp. nov. and Atactosia jeansi sp. nov.) are described.