Examining the volcanism-extinction link: an end-Guadalupian case study (2006-2010)
I have been researching the stratigraphic record of foraminifera, particularly fusulinaceans (a major casualty) as well as calcareous algae, in the Guadalupian-Lopingian (Permian) interval. The research team consists of palaeontologists (myself and Paul Wignall (PI)), stable isotope geochemists (Simon Bottrell (Co-I), Rob Newton (Co-I) and Helen Cope (RA)), a palynologist (Jason Hilton (Co-I)), a magnetostratigrapher (Jason Ali (Co-I)), and a stratigrapher (Lai Xulong (Co-I)).
The project is now "complete" although we are still working on it. I'm leaving the rationale etc up on my webpage, but you can read all about what we found out in the various publications that have come out of this project. A nice review is available in the journal Earth Science Reviews.
Project rationale
All mass extinctions of the past 300 Ma, and many of those before this time, coincide with large igneous province eruptions, but demonstrating a causal link has proved difficult. However, the connection is one of great relevance in earth sciences and the wider community because it allows the cause and consequence of high-amplitude climatic changes to be assessed. Many extinction scenarios involve a cascade of volcanically-driven environmental changes that including global warming from CO2 release and volcanic winters from pyroclastic eruptions (Fig. 1). Such conflicting causes form the core of extinction debates that began in the early 1980s. They have been difficult to resolve because the detailed time resolution required to compare disparate data such as fossil ranges and eruption histories are not available. For example, many workers have implicated the high-volume flood basalt eruptions of the Siberian Traps as a cause of the end-Permian mass extinction, whereas others “blame” the extensive Tuffaceous Series that underlies the basalts. It is difficult to test this link because the timing relationship relies on radiometric dating and its associated errors. Thus, the end-Permian mass extinction is best dated in its Chinese type section where U/Pb data indicate an age of 252.6 ± 0.2 Ma.In contrast, Ar-Ar dates for the Siberian Traps flood basalt eruptions indicate an age of 249.4 ± 0.5 Ma. Even allowing for problems when comparing two different radiometric systems, the resolution is still not sufficient to resolve which style of volcanism shows the closest temporal link with extinction. The key issue is the wide geographic separation between the site of volcanism and the areas where the fossil data is obtained. The development of proxies for volcanism, such as the marine osmium isotope record, offer a potential way forward, but the ideal test occurs when the extinction and volcanism record can be examined in the same sections.
 
Fortunately, such a test is available in the form of the end-Guadalupian extinction/Emeishan volcanism link. Hitherto, there has been very little work on this Permian extinction event because it lies “in the shadow” of the great end-Permian mass extinction peak (Fig. 2), and for a long time the Guadalupian extinction losses were incorporated into one protracted, late Permian phase of extinctions. Only in 1994 did two teams independently identify a separate mass extinction late in the Middle Permian followed by a phase of radiation and recovery prior to the end-Permian even. This crisis is best known from shallow marine, equatorial carbonate settings and was particularly severe for brachiopods, corals, echinoderms (blastoids, echinoids, crinoids), reef-forming sponges and foraminifera (especially fusulinids). In Sepkoski’s (1996) analysis of marine taxa the crisis ranks between second and fifth most severe of the Phanerozoic depending upon the extinction metric (Fig. 2).
Intriguingly, at around the same time as the identification of this extinction event, a flood basalt province was discovered in SW China. This is the Emeishan Province and it was initially considered a contributory factor in the end-Permian crisis. However, improvements in dating indicated that there is a better temporal link with the Guadalupian event.
The Emeishan basalts were emplaced on a carbonate platform and in some sections, notably in Guizhou Province, the lavas are interbedded with limestones. Thus, it is possible to directly study extinction and eruption histories within the same region and even within the same sections. Usefully, the volcanic province also has manifestations of a variety of eruption types, including voluminous early-stage flood basalts and late-stage pyroclastics. The latter volcanics are interbedded with plant-bearing deposits that offer the potential to also examine the floral extinction losses when compared with Early Permian plant assemblages of China. It will therefore be possible to directly compare extinction losses, both in the marine and terrestrial sphere, and the associated environmental changes with eruption styles and their timing.
This proposal aims to test the hypothesis that the Emeishan basalt eruptions precisely coincide with the onset of marine dysoxia and mass extinction due to a chain of cause-and-effects driven by volcanic CO2 release (Fig. 1).
Here are some photos of the team in China, and below them are some images of the forams I am looking at. These are taken from the Chaotian section in China, which contains both fusulinids and lagenide forams (click an image to enlarge).
   
    
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