Chemostratigraphy of the Cerro Victoria Formation (Lower Cambrian, Uruguay): Evidence for progressive climate stabilization across the Precambrian–Cambrian boundary
Claudio GaucherAlcídes N. SialValderez P. FerreiraMárcio Martins PimentelLeticia ChiglinoPeter Sprechmann
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Chemostratigraphy
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Abstract The Wa'ergang section in South China has been proposed as a potential Global Stratotype Section and Point (GSSP) for the base of Stage 10, the uppermost stage of the Cambrian System. In this study, high-resolution C-isotopic compositions are reported and we identified three large negative δ 13 C excursions, namely N1, N2 and N3, at Wa'ergang. The N1 is located just above the First Appearance Datum (FAD) of Lotagnostus americanus , corresponding to the possible base of the Proconodontus posterocostatus conodont Zone. The N2 was identified within the Micragnostus chuishuensis trilobite Zone and the Proconodontus muelleri conodont Zone. The N3 is located in the lowermost part of the Leiagnostus cf. bexelli – Archaeuloma taoyuanense trilobite Zone or Eoconodontus conodont Zone. The N1 and N2 can be correlated with the negative δ 13 C excursions preceding the Top of Cambrian Carbon Isotope Excursion (TOCE) observed globally. The N3 can be correlated with the TOCE or the HEllnmaria–Red Tops Boundary (HERB) Event. The inter-basinal correlation of N1 and L. americanus strongly supports that the base of Stage 10 may be best defined by the FAD of L. americanus . We also used a box model to quantitatively explore the genesis of the negative δ 13 C excursions from South China. Our numerical simulations suggest that weathering of the organic-rich sediments on the platform, probably driven by intermittent sea level fall and/or the oxygenation of the Dissolved Organic Carbon (DOC) reservoir in seawater, may have contributed to the generation of the negative δ 13 C excursions observed in the Stage 10 at Wa'ergang in South China.
Conodont
Trilobite
Chemostratigraphy
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Marine isotope stage
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This research was financially supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC 7961-215) to Uwe Brand.
Chemostratigraphy
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Ediacaran is a new system addition to the Stratigraphical Time Scale, which lies on the uppermost of the Neoproterozoic. Its GSSP (Global Boundary Stratotype Section and Point) have been affirmed in the Enorama Creek section in the central Flinders Ranges, South Australia and the point of the lower boundary was selected at the base of the Nuccaleena cap carbonate stood on the top of the uppermost Elatina diamictite (Gradstein et al., 2004; Knoll et al., 2004). The redefined Sinian System in China, bounded by the base of the cap carbonate (the lowermost Doushantuo Fm.) just above the Nantuo diamictite, quite corresponds with the Ediacaran System. In this paper, we synthesized new data on the Neoproterozoic at home and abroad and summed up advances in the chronostratigraphy of the Ediacaran Period, existing questions and developments in future, so that brings the attentions to the Precambrian stratigraphers and paleontologists.
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Snowball Earth
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Conglomerate
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paleoceanography
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Chemostratigraphy
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