Supplemental Material: A red bole zircon record of cryptic silicic volcanism in the Deccan Traps, India

Data tables, analytical protocols, and additional discussion.

Supplemental Material: A red bole zircon record of cryptic silicic volcanism in the Deccan Traps, India

Data tables, analytical protocols, and additional discussion.

Volcanic origin of the mercury anomalies at the Cretaceous-Paleogene transition of Bidart, France

The timing and mechanisms of the climatic and environmental perturbations induced by the emplacement of the Deccan Traps large igneous province (India) and their contribution to the Cretaceous-Paleogene (K-Pg) mass extinction are still debated. In many marine sediment archives, mercury (Hg) enrichments straddling the K-Pg boundary have been interpreted as the signature of Deccan Traps volcanism, but Hg may also have been derived from the Chicxulub (Mexico) impact. We investigated the Hg isotope composition, as well as the behavior of iridium (Ir) and other trace elements, in K-Pg sediments from the Bidart section in southwest France. Above the K-Pg boundary, Ir content gradually decreases to background values in the Danian carbonates, which is interpreted to indicate the erosion and redistribution of Ir-rich fallouts. No significant enrichment in Ir and W, or Zn and Cu, is observed just below the K-Pg boundary, excluding the hypothesis of downward remobilization of Hg from the boundary clay layer. Positive Δ199Hg and slightly negative values in the upper Maastrichtian and lower part of the early Danian are consistent with the signature of sediments supplied by atmospheric Hg2+ deposition and volcanic emissions. Up section, large shifts to strongly negative mass-dependent fractionation values (δ202Hg) result from the remobilization of Hg formerly sourced by the impactor or by a mixture of different sources including biomass burning, volcanic eruption, and asteroid impact, requiring further investigation. Our results provide additional support for the interpretation that the largest eruptions of the Deccan Traps began just before, and encompassed, the K-Pg boundary and therefore may have contributed to the K-Pg mass extinction.

Clumped-isotope-derived climate trends leading up to the end-Cretaceous mass extinction in northwest Europe

Paleotemperature reconstructions linked to Deccan traps volcanic greenhouse gas emissions and associated feedbacks in the lead-up to the end-Cretaceous meteorite impact and extinction document local and global climate trends during a key interval of geologic history. Here, we present a new clumped-isotope-based paleotemperature record derived from fossil bivalves from the Maastrichtian type region, in southeast Netherlands and northeast Belgium. Clumped isotope data documents a mean temperature of 19.2 ± 3.8 °C, consistent with other Maastrichtian temperature estimates, and an average seawater δ18O value of −0.3 ± 0.9 ‰ VSMOW for the region during the latest Cretaceous (67.1–66.0 Ma). A notable temperature increase at ~66.4 Ma is interpreted to be a regional manifestation of the globally-defined Late Maastrichtian Warming Event, linking Deccan Traps volcanic CO2 emissions prior to the end-Cretaceous extinction to climate change in the Maastricht region. Fluctuating seawater δ18O values coinciding with temperature changes suggest alternating influences of warm, salty southern-sourced waters and cooler, fresher northern-sourced waters from the Arctic Ocean. This new paleotemperature record contributes to the understanding of regional and global climate response to large-scale volcanism and ocean circulation changes leading up to a catastrophic mass extinction.