The cenomanian-turonian boundary at Eastbourne (Sussex, UK): a proposed European reference section

The Cenomanian-Turonian boundary (CTB) section at Eastbourne, Sussex, England is the thickest at outcrop in the Angle-Paris Basin, is rhythmic throughout, rich in macro-, micro- and nanno-fossils, and shows less diagenetic alteration than other sections in NW Europe. Geochemical and biostratigraphic data are all related to detailed (rhythmic) lithostratigraphy, allowing correlation with the global boundary stratotype section to within 20,000 years and accurate estimates of rates of changes. Very detailed stable isotope curves for oxygen and carbon are presented and show that the build-up phase of the CTB carbon excursion had two portions separated by a trough. Patterns of occurrence of coarse-fraction benthic foraminifera (>250 mu m) show two peaks of extinction corresponding to the two build-up phases of the carbon excursion. Benthic and planktic foraminifera, ostracods and calcareous nannofossils all show declines in diversity and abundance across the CTB. Foraminifera also decline significantly in size. Key biomarker events for the CTB include: first occurrences of the ammonites Fagesia catinus and Mammites nodosoides, the bivalve Mytiloides, the planktic foraminifera Helvetoglobotruncana praehelvetica and Marginotruncana renzi, and the calcareous nannofossils Quadrum intermedium, Q. gartneri and Eprolithus octopetalus; and last occurrences of the ammonite Sciponoceras, the planktic foraminifera Rotalipora greenhornensis and R. cushmani, the calcareous nannofossils Corolithion kennedyi, Axopodorhabdus albianus, Lithraphidites acutus, Rhagodiscus asper and Microstaurus chiastius. Cyclostratigraphy allows very precise correlation of isotopic and bioevents with other sections in Europe and North America. Eastbourne is recommended as a NW European standard section. (C) 1999 Elsevier Science B.V. All rights reserved.