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The Poigny borehole near Provins (Seine-et-Marne) provides the most complete single pristine section through the Upper Cretaceous Chalk of the Paris Basin. A well preserved and diverse palynoflora including 236 species and subspecies of organic-walled dinoflagellate cysts (dinocysts) is documented from the borehole, together with a high-resolution carbon-isotope curve (${\delta }^{13}$C$_{\mathrm{carb}}$) for the Coniacian–Campanian interval. Integration of the palynological and ${\delta }^{13}$C$_{\mathrm{carb}}$ data provides a basis for a chemostratigraphic and biostratigraphic correlation to England and Germany. Carbon isotope events (CIEs) are used to refine the placement of sub-stage boundaries in the core, and to calibrate and correlate distinctive palynological events with those from other European sections. Thirty-three palynological events in the upper Coniacian–Campanian, judged to be of biostratigraphic significance, are described. Palynological assemblages, the peridinioid/gonyaulacoid (P/G) dinocyst ratio and clay mineralogy are compared to depositional sequences and implicate sea-level as a major driver of palaeoenvironmental change.

Drilled in 1983, DSDP Site 534A is a prime location to investigate marl-limestone alterations from the middle Tithonian to the earliest Barremian. In 336 metres, the studied interval encompasses a nearly complete succession, allowing a high-resolution long-term study for this critical interval of Earth's history. To strengthen the Stratigraphy of the Jurassic-Cretaceous system boundary, we integrate the already published magnetostratigraphic, chemostratigraphic (bulk carbonate carbon isotopes) and biostratigraphic framework of the core (based on nannofossils, radiolarians, dinoflagellates and calpionellids) with cyclostratigraphy based on high-resolution (4cm) XRF data. Astronomical tuning of the core suggests a total duration of ~19 million years for the studied interval. Interestingly, long-term trends in the Ca/Fe ratio compare well with that of carbon isotopes. These trends are forced by the 9.1 Myr grand eccentricity cycle, placing the Weissert event close to a maximum of this grand cycle. Astronomical configuration appears to have played a major role in the development of this oceanic anoxic event. [ABSTRACT FROM AUTHOR]