Significant carbon isotope excursions in the Cambrian and their implications for global correlations

Abstract

The existing δ13C data in the Cambrian from different regions of the world are analyzed here. There are four well-documented carbon isotope excursions with global significance. In ascending order, they are: (1) a large negative excursion, comparable to “BACE” (BAsal Cambrian Carbon isotope Excursion) event, which occurs near the Precambrian-Cambrian boundary with a magnitude of 4‰–10‰ (PDB); (2) the “ZHUCE” (ZHUjiaqing Carbon isotope Excursion) event, a distinct positive excursion (over 5‰) that can be recognized at the Fortunian Stage to Stage 2 transition; (3) another strong negative one, so-called “ROECE” (Redlichiid-Olenellid Extinction Carbon isotope Excursion) event, shifting at the interval between Series 2 and Series 3, peaking at −3‰–−5‰ (PDB); (4) the famous Steptoean positive carbon isotope excursion (SPICE), which has been widely identified at the base of Furongian Series, Paibian Stage, with an amplitude about 4‰ (PDB). The four sharp δ13C shifts correlate well with coeval paleoceanographic changes and bioevents. Besides, there are some δ13C excursions from a few sections in previous studies, and more data are required to identify whether they are global or regional ones.