Carbon isotopes, stratigraphy and environmental change: the Middle/Upper Cambrian Positive Excursion (SPICE) in Port-au-Port Group, Western Newfoundland, Canada

• Main Authors: Barili, Rosalia, Neilson, Joyce, Brasier, Alexander, Goldberg, Karin, Pastro Bardola, Tatiana, De Ros, Luiz Fernando, Leng, Melanie
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: NRC Research Press (a division of Canadian Science Publishing) 2018
• Subjects: Canada; Newfoundland
• Online Access: http://hdl.handle.net/1807/90557; http://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2018-0025

In many basins, Upper Cambrian carbonate successions display intervals with a positive carbon isotope excursion (CIE) of up to +5‰. In North America, this marks the boundary between the Sauk II-III super-sequences. A Steptoean Positive Carbon Isotope Excursion (SPICE) locality previously identified in the Port-au-Port peninsula, western Newfoundland, has been revisited and an additional potential SPICE locality found. In both locations, a CIE is found to be associated with a prominent bioherm and sandstone layer within a sequence of carbonate rocks. At March Point, columnar stromatolites occur while at Felix Cove thrombolites can be seen. In the latter, the sandstone immediately overlies the thrombolites coincident with the CIE, while at March Point a dolomitized grainstone occurs above the stromatolites. The sandstone at this locality post-dates the CIE. Although lower than the SPICE in some localities, a positive CIE is present in both sections, March Point (+1.1‰) and Felix Cove (+1.8‰). Additionally, δ13Corg rises from –30.0‰ to –22.0‰ at March Point, and from -27‰ to –24.0‰ at Felix Cove and, in accordance with previously published work, we suggest that this could be the SPICE. Comparison of the stratigraphy and petrography between the two localities suggest that both depositional and diagenetic factors could have influenced the nature of the interpreted SPICE in Newfoundland. It is also possible that the local carbon isotopic signature may have been influenced by a semi-restricted depositional and early diagenetic environment, related to the paleogeographic configuration, rather than the global marine excursion. The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author.