Unraveling the Cretaceous-Paleogene Mass Extinction : Chicxulub, Deccan Volcanism, or a Dual Catastrophe?

The nature and causes of mass extinctions in Earth’s geological past have been the subject of intense scientific debate for over three decades. At the center of this debate is whether one or more large bolide impacts, the eruption of large igneous provinces (LIP), or a combination of both were the primary mechanisms driving the environmental changes that are widely regarded as the direct causes of four out of the five major Phanerozoic extinction events. The Chicxulub asteroid impact in present-day Mexico and the eruption of the vast Deccan volcanic province in India are two leading hypotheses for the cause of the end-Cretaceous mass extinction, which led to the demise of non-avian dinosaurs. Although the impact hypothesis has gained widespread acceptance, the lack of a high-resolution timeline for the Deccan basalt eruptions has hindered a comprehensive assessment of their relationship to the mass extinction. The bulk (80%) of the Deccan Trap eruptions occurred over a relatively short period within the magnetic polarity chron C29r. U-Pb zircon geochronology indicates that this main phase of eruptions began approximately 250,000 years before the Cretaceous-Paleogene (KPg) mass extinction and continued into the early Danian, suggesting a potential cause-and-effect relationship. Mercury (Hg) and more recently tellurium (Te) have been identified as indicators of large-scale volcanism in marine sediments, providing valuable insights into the relative timing of biological and environmental changes, mass extinctions, and delayed recoveries. Several studies have examined the correlation between Hg anomalies in sediments and LIP activity across mass extinction boundaries. However, Hg and Hg/TOC chemostratigraphies often yield conflicting results and appear to be influenced by non-volcanic secondary processes. In contrast, sedimentary tellurium (Te) concentrations, when normalized to immobile trace elements such as thorium (Th), may represent a more reliable proxy for volcanic input. We present a comprehensive high-resolution analysis of Hg and Te concentrations associated with the Deccan Traps, climate change, and the end-Cretaceous (KPg) mass extinction. This study is based on a transect of 30 sections from both shallow and deep environments across France, Spain, Italy, Denmark, Israel, Tunisia, Turkey, and India. In all sections, results show that Hg and Te concentrations increase by more than two orders of magnitude during the last 100,000 years of the Maastrichtian, continuing into the early Danian P1a zone (the first 380,000 years of the Paleocene). These Hg anomalies correspond with the main Deccan eruption pulses (Poladpur, Ambelani and Mahalabeswhar). These observations provide further support that Deccan volcanism played a key role in increasing atmospheric CO2 and SO2 levels that resulted in global warming and acidified oceans, increasing biotic stress that predisposed faunas to eventual extinction at the KPg.