Global Standard Stratotype‐section and Point (GSSP) of the Furongian Series and Paibian Stage (Cambrian)

Abstract

The Global Standard Stratotype‐section and Point (GSSP) of the Furongian Series (uppermost series of the Cambrian System) and the Paibian Stage (lowermost stage of the Furongian Series), has been recently defined and ratified by the International Union of Geological Sciences (IUGS). The boundary stratotype is 369 metres above the base of the Huaqiao Formation in the Paibi section, northwestern Hunan Province, China. This point coincides with the first appearance of the cosmopolitan agnostoid trilobite Glyptagnostus reticulatus, and occurs near the base of a large positive carbon isotopic excursion (SPICE excursion).

Geochemical evidence for widespread euxinia in the Later Cambrian ocean

“…Ultimately, the burial of both species results in the removal of carbon and sulphur from the ocean. This coupling can result in positive isotope shifts for both species in seawater: the carbon and sulphur leaving the ocean through burial are enriched in 12 C and 32 S via isotope fractionations accompanying photosynthetic and MSR pathways, respectively, leaving the seawater correspondingly enriched in 13 C and 34 S. Importantly, our model puts quantitative constraints on the size of the marine sulphate reservoir during the later Cambrian. An assumption of pre-SPICE sulphate concentrations greater than 2.5 mM demands more than 8 million years for recovery of δ 34 S sulphate (i.e., return to the pre-event baseline) following the SPICE (Figure S13), which is unreasonable in light of the available constraints on the duration of the SPICE 11 .…”

“…A well-documented extinction of trilobites coincides with the onset of the SPICE on the paleocontinent of Laurentia 10,12 , and the isotopic excursion has also been correlated to intervals of biological turnover on other paleocontinents 13 . The SPICE is also coincident with global changes in sea level; its onset coincides with a transgressive event, and its peak is concurrent with a lowstand recorded as the Sauk-II/III hiatus 10,11 .…”

The SPICE carbon isotope excursion in Siberia: a combined study of the upper Middle Cambrian–lowermost Ordovician Kulyumbe River section, northwestern Siberian Platform

“…4 herein). The two biozones constraining the Middle-Upper Cambrian boundary are now regarded as phylozones, because G. stolidotus is believed to be ancestral to G. reticulatus (Peng et al 2004). Non-evolutionary changes in trilobite complexes, such as migrations, have been suggested, however, to be common especially at the beginning of the G. reticulatus Biozone (Rozanov et al 1992).…”

“…2000), China (Saltzman et al 2000;Peng et al 2004;Zhu et al 2004), Antarctica (Buggisch, 2006) and Scandinavia (Ahlberg et al 2006) (Fig. 4).…”

“…2). The ratification by the International Union of Geological Sciences of the MiddleUpper Cambrian boundary between the Glyptagnostus stolidotus and G. reticulatus biozones in the Paibi section on the South China Platform (Peng et al 2004; Fig. 4) requires that the traditional position of this boundary on the Siberian Platform be changed accordingly.…”