Deposition or diagenesis? Probing the Ediacaran Shuram excursion in South China by SIMS
نویسندگان
چکیده
The Ediacaran Period (ca. 635–541 Ma) witnessed the earliest paleontological evidence for macroscopic animals (i.e., Ediacara biota) and geochemical observations of largest carbon cycle anomaly in Earth history Shuram Excursion, SE). Numerous hypotheses have been proposed origins SE, ranging from primary seawater to syn- or post-depositional diagenesis. Despite intensive theoretical work published past decade, empirical that is strictly based on fundamental petrographic results at micrometer scale still limited. To evaluate depositional compositions diagenetic effects samples we investigated EN3 interval Doushantuo Formation South China via integrated cathodoluminescence (CL), secondary ion mass spectrometry (SIMS), scanning electron microscope (SEM). Detailed reveal limestone dominated by calcite microspar, with minor but variable amounts disseminated zoned dolomite crystals. former likely formed neomorphism micrite, while latter was result progressive dolomitization. mean values paired SIMS δ13Ccalcite δ13Cdolomite are indistinguishable each sample consistent micro-drilled bulk-powder δ13C values, which interpret represent “background” signals dissolved inorganic (DIC). We also observed μm-scale variability data may reflect a overprint after deposition. Our origin SE provide little hypothesized isotope alteration meteoric mixing-zone diagenesis late burial In light this study, propose indeed represents marine bears close temporal link surface environment.
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ژورنال
عنوان ژورنال: Global and Planetary Change
سال: 2021
ISSN: ['0921-8181', '1872-6364']
DOI: https://doi.org/10.1016/j.gloplacha.2021.103591