Carbon and Sulphur Isotopes from the Cambrian Series 2-Series 3 Boundary: Potential Proxies for Global Correlation?

The Cambrian Series 2-Series 3 boundary intervals of five mixed carbonate-siliciclastic successions of Gondwana, Laurentia, and Siberia were analysed for their carbonate carbon isotopes (delta C-13(carb)) and sulphur isotopes from carbonate-associated sulphate (delta S-34(CAS)). For all sections, the boundary interval is characterized by distinct positive delta C-13(carb) excursions, flanking the first appearance datum (FAD) of trilobite species applied for the definition of (regional) bases of Cambrian Series 3. Whether the positive delta C-13(carb) shifts could be used as an additional proxy for an intercontinental correlation of the base of Cambrian Series 3 needs to be evaluated. No distinct positive and/or negative delta S-34(CAS) excursions are discernible for the investigated successions. However, delta S-34(CAS) data provide important information for the characterization of palaeoenvironmental conditions, but probably give no additional detail for a global correlation of the Cambrian Series 2-Series 3 boundary interval.