Clay mineralogical and geochemical expressions of the “Late Campanian Event” in the Aquitaine and Paris basins (France): Palaeoenvironmental implications

• Increased terrigenous inputs during the Late Campanian Event
• Late Campanian cooling explained by CO2 uptake linked to continental weathering
• Milankovitch-based duration of the LCE: 1.3 Myr

Campanian sediments from two French sedimentary basins were studied, using clay mineralogy and stable isotope (δ13C and δ18O) geochemistry, in order to investigate the Late Campanian Event. The clay fraction of the Campanian sediments from the Tercis-les-Bains section (Aquitaine Basin) and from the Poigny borehole (Paris Basin) is mainly composed of smectite. This background sedimentation was, however, interrupted during the Upper Campanian in the two basins by a substantial increase in detrital inputs, including illite, kaolinite, and chlorite at Tercis-les-Bains, and illite at Poigny. This detrital event, resulting from the enhanced erosion of nearby continental areas triggered by increasing runoff, has also been recognized in the Tethys and South Atlantic oceans. It coincided with a global negative carbon isotope excursion, the Late Campanian Event (LCE). Carbon isotope stratigraphy was used to correlate the two basins with previously studied sections from distant areas. Spectral analysis of the bulk δ13C from Tercis-les-Bains suggests a duration of ca. 400 kyr for a pre-LCE negative excursion and ca. 800–900 kyr for the LCE sensu stricto. The detrital event, as characterized by clay mineralogy, spans the interval that comprises the pre-LCE and the LCE, with a duration of 1.3 Myr. Intensification of continental erosion during the LCE may have resulted either from the Late Campanian polyplocum regression and/or from a regional tectonic pulse that triggered the emersion of previous submerged shelf areas and the increase of silicate erosion. As the LCE seems to be recorded at a large geographic scale, it is proposed here that enhanced chemical weathering and an associated decrease in atmospheric pCO2 levels could have contributed to the long-term Late Cretaceous cooling trend.