Variations of depositional redox conditions across the Cambrian-Ordovician boundary (GSSP, Green Point Formation) in western Newfoundland: implications from Mo-, U-, and S-isotope signatures and I/Ca ratios ...

• Main Author: Li, Jie
• Format: Text
• Language: English
• Published: Memorial University of Newfoundland 2024
• Subjects: Newfoundland
• Online Access: https://dx.doi.org/10.48336/hbxt-kj37; https://research.library.mun.ca/16369/

The Green Point Formation in western Newfoundland, Canada, includes the Global Boundary Stratotype Section and Point (GSSP) of the Cambrian-Ordovician (Є-O) boundary. This formation consists mainly of slope deposits of alternating lime mudstone and shale interbeds (rhythmites). In this study, we conducted an analysis of the isotopic and elemental signals of Mo and U in the shale and limestone. Additionally, we examined the textures and bulk δ³⁴Spy signals of biological pyrite in the shale and investigated the I/Ca ratios of the limestone. These analyses aim to provide a more comprehensive understanding of the depositional environments and marine redox conditions during the Є-O transition. The analysis revealed broad ranges of the shale authigenic δ⁹⁸ (−0.40 to +3.16‰) and the limestone δ⁹⁸Mocarb (−0.30 to +2.34‰) values. These observations, combined with significantly low Mo concentrations and the lack of fossils and bioturbations, suggest that the shale and limestone were both deposited under weakly ...