Integrated stratigraphical study of the candidate Oxfordian Global Stratotype Section and Point (GSSP) at Redcliff Point, Weymouth, Dorset, UK

Kevin N. PAGE, Guillermo MELENDEZ, Malcolm B. HART, Gregory D. PRICE, John K. WRIGHT, Paul BOWN, Julia BELLO

Abstract


Ham Cliff near Redcliff Point, Weymouth, Dorset (SW England) exposes one of Europe’s most completeCallovian-Oxfordian boundary sequences and has consequently been identified as a potential candidate GSSP for the base of the Oxfordian Stage. The boundary sequence lies within the thick mudrock facies of the Oxford Clay Formation and is abundantly fossiliferous, cardioceratid ammonites in particular being conspicuous. By convention, the stage boundary is drawn at the first occurrence of the genus Cardioceras here represented by C. redcliffense Page, Meléndez and Wright at the base of the Scarburgense Subchronozone of the Mariae Chronozone. Associated Perisphinctoidea (including Peltoceras, Alligaticeras and Euaspidoceras) provide additional biostratigraphical information. Othermacrofossil groups show less discernible changes, although frequent belemnites (Hibolithes) provide new highresolution carbon and strontium isotope data which are consistent with global curves and continuous sedimentation across the boundary interval. Magnetostratigraphic information is also available. Foraminiferal assemblages are dominated by epistominids but include a flood of early planktonic forms, including ?Globuligerina oxfordiana (Grigelis) immediately above the boundary. Well-preserved nannofloras are dominated by Watznaueria with conspicuous Zeugrhabdotus, podorhabdids and Stephanolithion indicating the NJ14 Biozone. Ostracoda and holothurian spicules are also recorded. These results are synthesised to provide a multidisciplinary, integrated review of the suitability of Redcliff Point for the definition of an Oxfordian GSSP. Correlations with the French candidate site in Haute-Provence are discussed and proposals made for formally establishing a GSSP for the base of the Oxfordian Stage in Europe.

Keywords


stratigraphy; Callovian; Oxfordian; GSSP; Dorset; ammonites; Geochemistry; micropalaeonotology

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