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

Abstract

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.

Timing and Provenance of Volcanic Fluxes Around the Permian‐Triassic Boundary Mass Extinction in South China: U‐Pb Zircon Geochronology, Volcanic Ash Geochemistry and Mercury Isotopes

“…Hg derived from direct volcanic emission is thought to have no measurable MIF (i.e., Δ 199 Hg, Δ 200 Hg = ∼0‰, Thibodeau & Bergquist, 2017;Zambardi et al, 2009), consistent with a recent estimate of the Δ 199 Hg value of the primitive mantle (0.00 ± 0.10‰, Moynier et al, 2021). Therefore, near-zero Δ 199 Hg values recorded for rock samples in the geologic record have been interpreted as reflecting unaltered volcanic Hg input to the depositional environment (e.g., Font et al, 2021;Thibodeau et al, 2016;Yager et al, 2021;H. Zhang, Zhang, & Shen, 2021).…”

“…Hg derived from direct volcanic emission is thought to have no measurable MIF (i.e., Δ 199 Hg, Δ 200 Hg = ∼0‰, Thibodeau & Bergquist, 2017; Zambardi et al., 2009), consistent with a recent estimate of the Δ 199 Hg value of the primitive mantle (0.00 ± 0.10‰, Moynier et al., 2021). Therefore, near‐zero Δ 199 Hg values recorded for rock samples in the geologic record have been interpreted as reflecting unaltered volcanic Hg input to the depositional environment (e.g., Font et al., 2021; Thibodeau et al., 2016; Yager et al., 2021; H. Zhang, Zhang, & Shen, 2021). Alternatively, near‐zero Δ 199 Hg values have also been interpreted as reflecting Hg contributions from a combination of terrestrial and oceanic Hg reservoirs (e.g., J. Shen, Chen, et al., 2019; J. Shen et al., 2021; X. Wang, Cawood, Zhao, Zhao, et al., 2019).…”

Extreme Planktic Foraminiferal Dwarfism Across the ETM2 in the Tethys Realm in Response to Warming

“…An increasing number of studies have shown that Hg geochemistry is complex and can be easily interfered with by local factors, rendering the use of Hg enrichment ineffective in tracing volcanism (Jin et al., 2023; Them et al., 2019). These factors include the transport pathway (Font et al., 2022; Liu et al., 2021), early diagenetic processes, and excessive TOC levels (Frieling et al., 2023). Charbonnier et al.…”

“…An increasing number of studies have shown that Hg geochemistry is complex and can be easily interfered with by local factors, rendering the use of Hg enrichment ineffective in tracing volcanism (Jin et al, 2023;Them et al, 2019). These factors include the transport pathway (Font et al, 2022;Liu et al, 2021), early diagenetic Paleoceanography and Paleoclimatology 10.1029/2023PA004762 processes, and excessive TOC levels (Frieling et al, 2023). Charbonnier et al (2020), evaluating the potential role of intense weathering and postdepositional organic matter (OM) degradation on the Hg/TOC, show that postdepositional degradation of marine OM type II to type III may largely modify the amount and the quality of OM.…”

Evidences of Teratology and Mutagenensis in Palynological Assemblages from the Middle Triassic Puesto Viejo Group, San Rafael Depocenter, Argentina. Implications of Volcanism and Regional Environmental Stress

“…Massive volcanism due to large igneous provinces has been associated with several mass extinction events but individual large explosive volcanoes can also cause regional to global environmental perturbations beyond climate change (Williams et al, 1992;Wignall, 2001Wignall, , 2005Ward, 2009;Black et al, 2012Black et al, , 2014Grasby et al, 2013Grasby et al, , 2019Spalletti & Limarino, 2017;Osipov et al, 2020;Racki, 2020;Cui et al, 2021;Font et al, 2022;Shen et al, 2022). Kutterolf et al (2013) suggest large explosive volcanoes can inject appreciable enough volumes of bromine and chlorine into the atmosphere that substantially deplete the stratospheric ozone layer on regional scale.…”