Large sulphur isotopic perturbations and oceanic changes during the Frasnian–Famennian transition of the Late Devonian

Abstract

The Frasnian-Famennian transition of the Late Devonian was one of the most critical intervals in the Phanerozoic. Sulphur isotopic pairs of carbonate-associated sulphate and pyrite sulphide from coeval sections in South China and Poland reveal frequent perturbations of sulphur cycling during this time interval. These data suggest a sudden oceanic overturn during a rapid sea-level fall probably induced by jerky block tilting in the latest Frasnian. This event was followed by long-lasting photic-zone euxinia during a rapid sea-level rise in the earliest Famennian. Large increases in continental nutrient fluxes, and subsequent primary productivity and organic burial, could have greatly enhanced bacterial sulphate reduction, producing excessive sulphide through the water columns owing to iron depletion. Subsequently, rapid ventilation of oceanic basins occurred, during which direct aerobic oxidation of sulphide into sulphate predominated in bottom waters and even surface sediments with minimal fractionation. This oxygenation was probably induced by intensive climatic cooling and/or large-scale sea-level fall. The temporal coincidence of two extinction phases with the oceanic overturn and succeeding photic-zone euxinia suggests that these extreme oceanic events played an important role in the severe biotic crisis. Furthermore, photic-zone euxinia coupled with subsequent climatic cooling may have delayed post-extinction recovery of some taxa.

Changes of palaeoenvironmental conditions recorded in Late Devonian reef systems from the Canning Basin, Western Australia: A biomarker and stable isotope approach

“…3). Similar δ 34 S values were previously reported in some European Late Devonian sediments (Joachimski et al, 2001) although sediments from Northern America, Southern China and Poland from the same time period showed more positive values (Goodfellow and Jonasson, 1984;Chen et al, 2013). Table 1 Selected elemental and molecular maturity parameters throughout the MR-1 core indicating an exceptionally low thermal maturity.…”

Ostracods (Crustacea) as shelf to basin indicators: evidence from Late Devonian Yangdi and Nandong sections in Guangxi, South China

“…Geochemistry, sedimentology, and other faunal evidence (e.g. conodonts) suggest a slope environment in the Yangdi section (Ji, 1989;Ma and Bai, 2002;Chen et al, 2013;Huang and Gong, 2016). However, none of the spinose podocopids (indicative of deep-and cold-water environments; Blumenstengel, 1965Blumenstengel, , 1979Kozur, 1972;Bandel and Becker, 1975;Lethiers and Crasquin, 1987;Wang, 1988;Casier, 2004; some authors also considered spinose-podocopid ostracod assemblages as indicative for low-energy environments, which might not be particularly deep or cold; Becker, 2000;Groos-Uffenorde et al, 2000) were found together with the smooth-podocopid association in the Yangdi section.…”

“…It is a well-outcropped section with continuous deposition of the Late Devonian, which has been studied in detail for biostratigraphy, lithostratigraphy, chemostratigraphy and cyclostratigraphy (Ji, 1989;Gong et al, 1997Gong et al, , 2005Wang, 1990;Ma and Bai, 2002;Chen et al, 2013). A reliable and high-resolution conodont biostratigraphy has been established in this section by Huang and Gong (2016).…”

Geochemical evidence for euxinia during the Late Devonian extinction events in the Michigan Basin (U.S.A.)

“…Recently, two high-resolution studies that utilized carbonateassociated sulfate to reconstruct the sulfur isotope composition of seawater sulfate have reported negative excursions in δ 34 S SO 4 near the F-F boundary (John et al, 2010;Chen et al, 2013). This negative excursion δ 34 S is potentially reflected in our δ 34 S py data from the Lower Antrim at the LKE and UKE.…”

“…However, such a mechanism leading to the synchronous and uniform distribution of this sulfate to the ocean, while also delivering enough material to impact the δ 34 S SO 4 , is difficult to rectify on a global scale. Alternatively, Chen et al (2013) advocated that the transient decline in δ 34 S SO 4 was caused by both the increased delivery of continentally weathered sulfur and the oxidation of sulfide from euxinic water masses in epicontinental water columns. In basins that turn euxinic, iron becomes the limiting reagent in the formation of pyrite leading to accumulation of aqueous sulfide.…”