UNTANGLING THE RELATIONSHIP BETWEEN DECCAN VOLCANISM, CHICXULUB IMPACT, AND ORBITAL FORCING AND THE EVENTS THAT OCCURRED ACROSS THE CRETACEOUS/PALEOGENE BOUNDARY

The 1 Myr interval across the Cretaceous/Paleogene boundary (KPB) is a brief period of Earth's history during which several remarkable events took place: the asteroid impact of Chicxulub (~66 Ma), the massive volcanic episode of Deccan Traps (~66.3–65.6 Ma), and the KPB mass extinction event (~66 Ma). Other relevant events were the Late Maastrichtian Warming Event (LMWE; 66.25-66.10 Ma), the Dan-C2 (65.8-65.7 Ma), and the Lower-C29n (LC29n; 65.48-65.41 Ma), which seem to be mainly related to orbital forcing according to recent astrochronological calibrations.

Here we focus on evaluating the relationship of the climatic, environmental, and biological changes mentioned above with the Deccan volcanism and the Chicxulub impact. For it, we carried out high-resolution planktic foraminiferal and geochemical analyses from some of the most internationally known sections of the KPB, such as Caravaca and Zumaia (Spain), El Kef and Aïn Settara (Tunisia), and ODP-1262 (South Atlantic). All proxies have been calibrated with an updated and orbitally tuned age model and compared with the eruptive models proposed for the Deccan Traps.

No relevant paleoenvironmental changes have been recognized during the LMWE nor the last 100 kyr of the Maastrichtian, suggesting a weak environmental impact of Deccan volcanism during this period. Similarly, we have not recognized an increase in environmental stress conditions during the Dan-C2 and LC29n climatic events. Conversely, we have identified in all the studied sections a bloom of opportunistic triserial guembelitriids Chiloguembelitria in the early Danian (~65.9 Ma), which covariate with an increase in aberrant planktic foraminifera suggesting a rebound in the environmental stress conditions 100 kyr after the KPB event. This environmental stress episode is correlated with an anomaly in Hg content and Hg/TOC ratio (~65.9 Ma) recognized at ODP-1262, which supports a cause-effect relationship with the Deccan volcanism, specifically with the emplacement of the Ambelani Fm. according to the most recent radiometric dating of the Deccan Traps.