The stratigraphy of the upper Campanian Chalk of the southern English coast (Isle of Wight, Dorset), United Kingdom

Abstract

The litho- and biostratigraphy of the coastal exposures of upper Campanian chalk on the southern English coast, in east Dorset and on the Isle of Wight are described, correlated within the region and with the succession eastern England (Norfolk) and northern Germany using macrofossils. A succession of flint layers and thin marl beds is can be traced in detail along the English coastal outcrop over a distance of 60 km; important new markers are the Needles Flint and its distinctive associated suite of marls, and the Alum Bay Marls in the uppermost Portsdown Chalk Formation. The successions exposed at the eastern and western ends of the Isle of Wight are similar in both bed development and thickness, but the succession at Studland in Dorset is considerably expanded in comparison. The upper Campanian succession at Studland is a thrust slice, emplaced from south of the Purbeck Fault during Paleogene inversion and subsequently tilted. The Studland succession is both expanded and contains redeposited chalk, both evidence that the Purbeck Fault was actively extensional during the Campanian. The Mucronata Transgression of Germany possibly correlates with an interval in the lower Portsdown Chalk characterised by abundant microcrinoid and bryozoan debris. A new microcrinoid zonation for the upper Campanian is developed on the Isle of Wight, and zones CaR11-CaR15 are defined. New microcrinoid taxa described are Hessicrinus vectensis sp. nov., Sagittacrinus rotundacutus sp. nov., Costatocrinus fragilis sp. nov. and Douglasicrinus alumensis gen. et sp. nov.