Integrated Stratigraphy of the English Turonian - Campanian Chalk: Refining and Calibrating the Late Cretaceous Time Scale

We present high-resolution (10–25 cm interval) carbonate carbon- and oxygen-isotope records (δ13Ccarb, δ18Ocarb) for the 162 m thick Chalk section exposed in the sea cliffs at Seaford Head, southern England. This reference section for the Upper Cretaceous of NW Europe has been proposed as a global reference for the Coniacian–Santonian stage boundary and is a Standard Auxiliary Boundary Stratotype (SABS) for the Campanian Stage. Carbon-isotope stratigraphy, comprising 30 named carbon-isotope events (CIEs), supported by lithostratigraphy, macrofossil, microcrinoid, microfossil, organic walled dinoflagellate cyst and calcareous nannofossil biostratigraphy, allows for precise correlation to other key European sections. CIEs provide the means of placing the Coniacian (top Navigation CIE) and Campanian (top Late Santonian Event) stage boundaries, while the lowest occurrence of the inoceramid bivalve Cladoceramus undulatoplicatus defines the base Santonian. Our integrated stratigraphic approach allows for intercalibration of bioevents, biozonation schemes and chemostratigraphy. Spectral analysis of carbon and oxygen isotope profiles at Seaford Head demonstrates a clear expression of 405 kyr orbital cycles, offering the basis for orbital tuning of the isotope time series. Correlation of the Seaford Head orbital time scale to geochronological ages of bentonites from the US Western Interior Basin permits anchoring of the isotope records to various astronomical solutions. We favour a tuning approach to the La04 sinusoidal eccentricity solution along with a tie of 405 kyr minima to existing Laskar/Zeebe solutions for age calibration of biostratigraphic datum levels. Our results provide a basis for improved correlation and age calibration of Coniacian to Campanian successions at a regional to global scale.