CLIMATE, ENVIRONMENTAL, AND BIOLOGICAL CHANGES ACROSS THE CRETACEOUS/PALEOGENE BOUNDARY: UNRAVELLING THE ROLE OF THE CHICXULUB IMPACT, DECCAN VOLCANISM, AND ORBITAL FORCING THROUGH AN INTERDISCIPLINARY APPROACH AT THE ZUMAIA SECTION (Invited Presentation)

Radiometric dating has recently revealed that the main volcanic activity of the Deccan Traps occurred between ~400 kyr prior and ~600 kyr after the Cretaceous/Paleogene boundary (KPB), renewing interest in the causes of the climatic, environmental, and biological changes that occurred around the Chicxulub impact at ~66 Ma. Here, we focus on constraining the timing of environmental perturbations linked to Deccan volcanism to fully understand its relative influence on Earth's climate during this 1 Myr interval, along with the Chicxulub impact and orbital forcing.

We conducted high-resolution planktic foraminiferal, geochemical, and geophysical analyses calibrated to an updated orbitally tuned age model developed at Zumaia, Spain. This led us to propose a revised chronology of major carbon isotope excursions (CIEs) and planktic foraminiferal events. Excluding the KPB CIE, the largest observed CIEs in this interval correlate with the following climatic events: the Late Maastrichtian Warming Event (LMWE, 66.25–66.10 Ma) and the Danian events Dan-C2 (65.8–65.7 Ma) and LC29n (65.48–65.41 Ma). Both the LMWE and the Dan-C2 align with 405 kyr eccentricity maxima, the last of the Maastrichtian and the first of the Danian respectively, while the LC29n event correlates with a 100 kyr eccentricity maximum. Comparison with the latest eruptive models of Deccan volcanism suggests that high volcanic activity co-occurred with the 405 kyr eccentricity maxima during the LMWE. The other climatic events do not seem to coincide with Deccan volcanic phases. However, in several open marine localities worldwide we identified a bloom of opportunistic triserial guembelitriids and aberrant forms (indicating environmental stress), coinciding with one of the Deccan volcanic phases around ~65.9 Ma. To further understand the relationship between volcanism and climate change, we report for the first time at Zumaia a complete Hg enrichment profile across the entire Deccan volcanic activity interval, along with a novel volcanic input proxy, the tellurium/thorium (Te/Th) ratio. This multidisciplinary and high-resolution approach will allow us to robustly integrate our results with paleoclimatic, paleoenvironmental, and paleobiological proxies, improving our understanding of the Cretaceous-Paleogene transition.