Citation:

S0016756808004913

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Abstract:

An integrated, high-resolution chemostratigraphic (C, O and Sr isotopes) and magnetostratigraphic study through the upper Middle Cambrian – lowermost Ordovician shallow-marine carbonates of the northwestern margin of the Siberian Platform is reported. The interval was analysed at the Kulyumbe section, which is exposed along the Kulyumbe River: an eastern tributary of the Enisej River. It comprises the upper Ust'-Brus, Labaz, Orakta, Kulyumbe, Ujgur, and lower Iltyk formations and includes the Steptoean positive carbon isotopic excursion (SPICE) studied here in detail from upper Cambrian carbonates of the Siberian Platform for the first time. The peak of the excursion, showing d13C positive values as high as +4.6‰ and least-altered 87Sr/86Sr ratios of 0.70909, is reported herein from the Yurakhian Horizon of the Kulyumbe Formation. The stratigraphic position of the SPICE excursion does not support traditional correlation of the boundary between the Orakta and Labaz formations at Kulyumbe River with its supposedly equivalent level in Australia, Laurentia, South China, and Kazakhstan, where the Glyptagnostus stolidotus and G. reticulatus biozones are known to immediately precede the SPICE excursion and span the Middle-Upper Cambrian boundary. The Cambrian-Ordovician boundary is probably situated in the middle Nyajan Horizon of the Iltyk Formation, in which carbon isotope values show a local maximum below a decrease in the upper part of the Nyajan Horizon, attributed herein to the Tremadocian. A refined magnetic polarity sequence shows that the geomagnetic reversal frequency was very high during the Middle Cambrian at 5-10 reversals per Ma, assuming a total duration of ~10 Ma and up to 100 magnetic intervals in the Middle Cambrian. By contrast, the sequence attributed herein to the Upper Cambrian on chemostratigraphic grounds contains only 10-11 magnetic intervals.

Preprint in Open Access hdl:10013/epic.30209.d001

Coverage:

Median Latitude: 68.000000 * Median Longitude: 88.790000 * South-bound Latitude: 68.000000 * West-bound Longitude: 88.700000 * North-bound Latitude: 68.000000 * East-bound Longitude: 89.000000

Event(s):

Kulyumbe-section * Latitude Start: 68.000000 * Longitude Start: 88.700000 * Latitude End: 68.000000 * Longitude End: 89.000000 * Location: Kulyumbe river, Siberia, Russia * Method/Device: Geological profile sampling (GEOPRO) * Comment: The profile derives from several outcrops along the Kulyumbe River, located ~100 km E of the Enisej River, at the northwestern margin of the Siberian Platform, where the Middle Cambrian – Lower Ordovician sediments are exposed along ca. 10 km of the Kulyumbe River. The beds are inclined, so their total thickness does not correspond to the topographic elevation between their base and top.

License:

Creative Commons Attribution 3.0 Unported (CC-BY-3.0)

Size:

5 datasets

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Datasets listed in this publication series

Kouchinsky, A (2008): Appendix Table 1. δ¹³C, δ¹⁸O and palaeomagnetic data from the Kulyumbe section. https://doi.org/10.1594/PANGAEA.687391
Kouchinsky, A (2008): Appendix Table 2. Concentrations of major and trace elements in selected samples from the Kulyumbe section. https://doi.org/10.1594/PANGAEA.687440
Kouchinsky, A (2008): Appendix Table 3. Sr-isotopic data from the Kulyumbe section and associated C-, O- and S-isotopic and trace elemental data. https://doi.org/10.1594/PANGAEA.687438
Kouchinsky, A (2008): Appendix Table 4. Strontium isotope results of leaching experiments. https://doi.org/10.1594/PANGAEA.687435
Kouchinsky, A (2008): Appendix Table 5. List of trilobite species from the Kulyumbe section. https://doi.org/10.1594/PANGAEA.687433