Deccan Volcanism caused the mass extinction 66 million years ago

Wednesday, Sep 23, 2020

Fig. 1 Deccan Traps volcanic mountains. (see full Fig. captions below)

Fig. 1 Deccan Traps volcanic mountains. (see full Fig. captions below)

Multiple evidence reveals the killing mechanism for the mass extinction 66 m.y. ago began 25,000 years earlier with the onset of cataclysmic Deccan volcanic eruptions in India that caused hyperthermal warming, mercury toxicity, ocean acidification and acid rain on land.  Once the tipping point for life was reached, the mass extinction occurred within less than 1000 years correlative with accelerated maximum volcanic eruption, maximum mercury fallout globally, as documented in Tunisia and Israel, and the longest known lava flows that traversed over 1000 km across India. Age control is based on U-Pb dating of the Deccan Traps and correlated with orbital cyclicity at the Elles section in Tunisia, which yielded the highest age resolution possible to date. Our database reveals Deccan volcanism as primary cause for the mass extinction. Recent claims that the Chicxulub impact caused the mass extinction during global cooling and in the absent of Deccan eruptions are not substantiated and based on incomplete deep-sea records with common erosion/hiatus across the mass extinction. 

 

Published online Sept. 3, 2020. Global and Planetary Change 194:103312.  DOI:10.1016/j.gloplacha.2020.103312

Mercury linked to Deccan Traps volcanism, climate change and the end-Cretaceous mass extinction

Gerta Keller, Paula Mateo, Johannes Monkenbusch, Nicolas Thibault, Jahnavi Punekar, Jorge E. Spangenberg, Sigal Abramovich, Sarit Ashckenazi-Polivoda, Blair Schoene, Michael P. Eddy, Kyle M. Samperton, Syed F.R. Khadri, Thierry Adatte, 2020.

Fig. 2 The mass extinction, climate change, Mercury fallout directly correlated to cataclysmic Deccan eruptions. (see full Fig. captions below)

Fig. 2 The mass extinction, climate change, Mercury fallout directly correlated to cataclysmic Deccan eruptions. (see full Fig. captions below)

Abstract: We test whether Hg in marine sediments over the last 550 m.y. of the Cretaceous is a reliable proxy linking Deccan Traps volcanic eruptions to late Maastrichtian global climate warming and the mass extinction at the Cretaceous-Paleogene boundary (KPB). Our primary test site is the Elles section in Tunisia, the auxiliary Global Stratotype Section and Point (GSSP) to El Kef. Elles has the most complete marine sedimentary record and a high average sedimentation rate of ~4.7 cm/ky. We chose the Hor Hahar section in Israel to corroborate the geographic distribution of Hg fallout from Deccan volcanism. Reliability of the Hg proxy over the last 550 ky of the Maastrichtian to early Danian was evaluated based on high-resolution age control (orbital cyclostratigraphy), stable isotope climate record, Hg concentrations, biotic turnover and mass extinction. The results were correlated with the pulsed Deccan eruptive history constrained previously by U-Pb zircon geochronology.

Our results support Hg as robust proxy for Deccan volcanism with large Hg spikes marking “extreme event” (EE) pulsed eruptions correlative with climate warming peaks separated by steady, less intense eruptions. Long-term global climate warming began near ~350 ky pre-KPB, reached maximum warming (3–4 °C) between 285 and 200 ky pre-KPB, followed by gradual cooling and rapid temperature drop between 45 and 25 ky pre-KPB. During the last 25 ky before the KPB, multiple Hg EE eruptions correlate with hyperthermal warming and culminate in the rapid mass extinction at Elles during ≤1000 years of the Cretaceous. These latest Cretaceous Hg peaks may correlate with massive, distal, Deccan-sourced lava flows (> 1000 km long) that traversed the Indian subcontinent and flowed into the Bay of Bengal, bracketing the mass extinction. Results support Deccan volcanism as the primary driver of the end-Cretaceous mass extinction.

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Fig. 1. Deccan Traps Volcanic Mountains in western India near Pune. Deccan eruptions accumulated over 350,000 years in horizontal Lava flows covering an area the size of France to a height of 3400 m. Eruptions occurred in pulses resulting in global climate warming. The major eruption pulse coincided with the KPB mass extinction.

Fig. 2. Fig. 7. High-resolution planktic foraminifera and relative abundances, δ18O and Hg data at the astronomically tuned Elles section in Tunisia and comparison with δ18O data at Sites 525A and 1262, Deccan Traps stratigraphy and geochronology. Note the direct link between Hg anomalies and δ18O at Elles (and at Sites 525A and 1262, except for the KPB hiatus) demonstrates the effect of Deccan volcanism on global climate; the rapid increase in Hg loading (paroxysmal Deccan eruptions) correlates to hyperthermal warming and surface ocean acidification during the last 25 ky pre-KPB. Ocean acidification is also observed in C30n, lower C29n (CF2 and CF2/CF1). Increased stress on marine life through the late Maastrichtian (increased relative abundance of disaster opportunist species, decreased specialist species) reached maximum during the last 25 ky pre-KPB and ended with the mass extinction. KPB age at 66.016 Ma; Deccan Traps U-Pb dates from Schoene et al. (2015, 2019) and Eddy et al. (2020). Uncertainty in cyclostratigraphic ages: 20 ky (one precession cycle). Ma: millions of years ago, ky: thousands of years.