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International correlation of the Cambrian Series 2-3, Stage 4-5 boundary intervalстатья
- Авторы: Sundberg F.A., Geyer G., Kruse P.D., McCollum L.B., Pegel' T.V., Zylinska A., Zhuravlev A.Yu
- Журнал: Australasian Palaeontological Memoirs
- Том: 49
- Год издания: 2016
- Первая страница: 83
- Последняя страница: 124
- Аннотация: International correlation of the lower-middle Cambrian boundary interval (Series 2-3, Stage 4-5) is difficult due to the paucity of globally distributed trilobite taxa and clear documentation of the stratigraphic distribution of taxa in different palaeogeographic regions. Correlation of this interval between the Great Basin of the western United States, Taconic allochthons of the eastern United States, Greenland, Newfoundland, Morocco, Iberia, Baltica (Scandinavia and Poland), Siberia, Australia and South China is presented here using the stratigraphic ranges of 47 species and 46 genera of trilobites and supplemented with archaeocyathan assemblages and acritarch assemblage zones. These data are compared to the First Appearance Datums (FAD) of two oryctocephalids, Ovatoryctocara granulata and Oryctocephalus indicus, that have been proposed as biohorizons to define the base of Series 3, Stage 5. Based on this study, it is evident that there is no taxon suitable for lower-middle Cambrian correlation that is present in all regions. The correlation chart indicates that trilobite genera, previously used extensively as guides, have long stratigraphic ranges and are of limited use for correlation, in contrast to species that allow a more precise correlation. Although the regionally defined lower-middle Cambrian boundaries do not correlate, they generally occur near the FAD of either Ovatoryctocara granulata or Oryctocephalus indicus. The stratigraphically lower FAD of Ovatoryctocara granulata more or less coincides with the boundaries in Newfoundland, Baltica (Poland) and Siberia, but the boundary in Australia is below this level. The FAD of Oryctocephalus indicus approximates the boundary in South China. The boundaries in the Great Basin, Greenland, Baltica (Scandinavia) and Iberia occur between these two horizons. Only the sections in Siberia and possibly Greenland contain both candidate species. The sections in the Taconic allochthons, Baltica (both Scandinavia and Poland), Morocco, Iberia and Australia contain neither species. The Taconic allochthons are tied to the biostratigraphic scheme for Greenland and Newfoundland. Baltica is correlated to the overall scheme with taxa in common with Greenland, Newfoundland, Morocco, Iberia and Siberia. Morocco and Iberia are correlated based on similarities to Newfoundland, Siberia and South China. Australia is correlated based on similarities to South China and the Great Basin.
- Добавил в систему: Журавлев Андрей Юрьевич