High-resolution dinoflagellate cyst biostratigraphy of the Santonian–basal Campanian (Upper Cretaceous): new data from Whitecliff, Isle of Wight, England

Abstract

Results are presented of a high-resolution study of dinoflagellate cysts from part of the Upper Chalk succession on the Isle of Wight, southern England. The section was logged in detail, and stage and zonal boundaries were located using macrofossil data. Lower and middle Santonian samples are dominated by species of Senoniasphaera, Canningia, Circulodinium and Heterosphaeridium. Major changes in the dinocyst assemblages coincide with the base of the upper Santonian Uintacrinus socialis crinoid Zone, with an increase in abundance and diversity, and a shift to assemblages dominated by Spiniferites spp. and Palaeohystrichophora infusorioides Deflandre. Our palynological records (114 dinocyst, 4 acritarch species) provide the basis for a new event stratigraphy. Cyclonephelium filoreticulatum (Slimani) Prince, Jarvis et Tocher, comb. nov. temporarily disappears and an acme of Heterosphaeridium? heteracanthum (Deflandre et Cookson) Eisenack et Kjellstrom occur in the lower Santonian. The total range of Renidinium rigidum Prince, Jarvis et Tocher, sp. nov. and the FAD of Senoniasphaera protrusa Clarke et Verdier emend. lie within the middle Santonian. Raetiaedinium truncigerum (Deflandre) Kirsch and Pervosphaeridium monasteriense Yun first appear, and Hystrichostrogylon membraniphorum Agelopoulos reappears around the base of the upper Santonian. The FADs of Pervosphaeridium intervelum Kirsch and Thalassiphora? spinosa (Clarke et Verdier) Foucher, and the reappearance datums (RADs) of Chlamydophorella nyei Cookson et Eisenack, Subtilisphaera pontis–mariae (Deflandre) Lentin et Williams and Membranilarnacia polycladiata Cookson et Eisenack occur in the upper Santonian. No major changes in dinocyst assemblages occur at the Santonian/Campanian boundary, but a sequence of LADs occur in the basal lower Campanian, in the order: Xenascus perforatus (Vozzhennikova) Yun; Spinidinium echinoideum (Cookson et Eisenack) Lentin et Williams; Surculosphaeridium? longifurcatum (Firtion), Davey et al.; Raetiaedinium truncigerum (Deflandre) Kirsch and S. protrusa; Florentinia ferox (Deflandre) Duxbury; Acanthaulax wilsonii Yun and T.? spinosa. The range of Endoscrinium campanula (Gocht) Vozzhennikova extends into the upper Santonian. Additional taxonomic proposals are: Senoniasphaera Clarke emend.; S. rotundata Clarke et Verdier emend.; Circulodinium latoaculeus (Yun) Prince, Jarvis et Tocher, comb. nov.