A major sulphur isotope event at c. 510 Ma: a possible anoxia–extinction–volcanism connection during the Early–Middle Cambrian transition?

Abstract

A new approach to constraining seawater δ34S and sulphate concentration using francolite‐bound sulphate reveals an abrupt increase in δ34S to +50‰ around the Early–Middle Cambrian boundary. Such high δ34S values are best explained by increased rates of pyrite burial due to ocean anoxia coupled with an increased sensitivity of the ocean sulphate reservoir to perturbations due to low sulphate concentrations of 500–700 μgL−1. We argue that the spread of anoxic waters at this time was partly the result of greenhouse warming related to the eruption of the Kalkarindji Large Igneous Province of northern Australia and that it triggered the collapse of early metazoan reef ecosystems during the latest Early Cambrian. Mass extinctions of the last 260 Myr have all coincided with enhanced volcanic activity, while several are also associated with positive shifts in seawater δ34S. Extending this correlation back in time further implicates volcanically induced climate change as a major determining factor in biosphere evolution. Terra Nova, 18, 257–263, 2006

Carbonates in Skeleton-Poor Seas: New Insights From Cambrian and Ordovician Strata of Laurentia

“…On the basis of widespread black shales and low C:S ratio, widespread dysoxia and local anoxia have long been inferred for subsurface water masses of Series 3 and Furongian Cambrian oceans (e.g., Berry and Wilde, 1978;Raiswell and Berner, 1986;Zhuravlev and Wood, 1996;Hallam, 1998;Gaines et al, 2005;Hough et al, 2006;Hurtgen et al, 2009). Recent geochemical research supports earlier hypotheses and indicates that at times subsurface anoxia may have been global (Gill et al 2007).…”

The Henson Gletscher Formation, North Greenland, and its bearing on the global Cambrian Series 2–Series 3 boundary

“…The beginning of this large-magnitude shift to negative δ 13 C values lies just beneath an extinction level associated with the upper boundary of the Olenellus Zone (Palmer 1998). The hypothesis that anoxic waters developed below the surface mixed layer at least locally during the latest Early Cambrian, before the major transgressions at the Lower-Middle Cambrian boundary interval is well supported by sulphur isotope data (Hough et al 2006).…”

A paired sulfate–pyrite δ34S approach to understanding the evolution of the Ediacaran–Cambrian sulfur cycle

“…547 and 540 Ma . The Ara Group and E-C boundary strata are known definitively only from the sub- (Kampschulte and Strauss, 2004;Goldberg et al, 2005;Fike et al, 2006;Hurtgen, 2006); evaporites (Pisarchik and Golubchina, 1975;Claypool et al, 1980;Houghton, 1980;Strauss, 1993;Banerjee et al, 1998;Walter et al, 2000;Strauss et al, 2001;Schrö der et al, 2004); phosphorites: (Shen et al, 1998;Shields et al, 1999;Shen et al, 2000;Goldberg et al, 2005;Hough et al, 2006). Age ranges have been updated to the most recent geochronological constraints where possible (Gradstein et al, 2004).…”