Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian Series. It lies atop the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia.[2][3] Neither the upper nor lower boundary has yet been defined by the International Commission on Stratigraphy.[4][5] The preferred definitions for the lower boundary are the first appearance of the molluscs Watsonella crosbyi or Aldanella attleborensis around 529 million years ago.[6][7] The correlation between the lowest occurrences of A. attleborensis and W. crosbyi with the Zhujiaqing positive carbon isotope excursion (ZHUCE) has led to the conclusion that the combination of these two markers are a reliable indicator of the boundary between the Fortunian and Stage 2.[8] The proposed upper boundary might be the first appearance of trilobites around 521 million years ago.[4]
| Cambrian Stage 2 | ||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chronology | ||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||
| Etymology | ||||||||||||||||||||||||||||||||||||||
| Name formality | Informal | |||||||||||||||||||||||||||||||||||||
| Usage information | ||||||||||||||||||||||||||||||||||||||
| Celestial body | Earth | |||||||||||||||||||||||||||||||||||||
| Regional usage | Global (ICS) | |||||||||||||||||||||||||||||||||||||
| Time scale(s) used | ICS Time Scale | |||||||||||||||||||||||||||||||||||||
| Definition | ||||||||||||||||||||||||||||||||||||||
| Chronological unit | Age | |||||||||||||||||||||||||||||||||||||
| Stratigraphic unit | Stage | |||||||||||||||||||||||||||||||||||||
| Time span formality | Formal | |||||||||||||||||||||||||||||||||||||
| Lower boundary definition | Not formally defined | |||||||||||||||||||||||||||||||||||||
| Lower boundary definition candidates | First appearance of small shelly fauna or Archaeocyathids | |||||||||||||||||||||||||||||||||||||
| Lower boundary GSSP candidate section(s) | None | |||||||||||||||||||||||||||||||||||||
| Upper boundary definition | Not formally defined | |||||||||||||||||||||||||||||||||||||
| Upper boundary definition candidates | FAD of Trilobites | |||||||||||||||||||||||||||||||||||||
| Upper boundary GSSP candidate section(s) | None | |||||||||||||||||||||||||||||||||||||
Naming
editThe name "Laolinian" after the Laolin village in Yunnan, China, was proposed for the Stage 2 in 2012.[9]
Stratotype
editPossible candidates for a GSSP include the first appearance of Watsonella crosbyi in the Zhujiaqing Formation (朱家庆组) in Yunnan, China or the Pestrotsvet Formation near the Aldan River on the Siberian Platform.[10]
References
edit- ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. September 2023. Retrieved November 10, 2024.
- ^ Kouchinsky, Artem; Bengtson, Stefan; Missarzhevsky, Vladimir V.; Pelechaty, Shane; Torssander, Peter; Val'kov, Anatolij K. (24 September 2001). "Carbon isotope stratigraphy and the problem of a pre-Tommotian stage in Siberia". Geological Magazine. 138 (4): 387–396. Bibcode:2001GeoM..138..387K. doi:10.1017/S0016756801005684. S2CID 3884375.
- ^ Landing, E.; Kouchinsky, A. V. (2016). "Correlation of the Cambrian Evolutionary Radiation: geochronology, evolutionary stasis of earliest Cambrian (Terreneuvian) small shelly fossil (SSF) taxa, and chronostratigraphic significance". Geol. Mag. 153 (4): 750–756. Bibcode:2016GeoM..153..750L. doi:10.1017/s0016756815001089. S2CID 132867265.
- ^ a b "GSSP List ICS". ICS. Archived from the original on 15 November 2012. Retrieved 2024-03-26.
- ^ P. Yu. Parkhaev, Yu. E. Demidenko, M. A. Kulsha (2020). "Zooproblematica Mobergella radiolata as Index Species of the Lower Cambrian Stage Units" (PDF). Стратиграфия. Геологическая корреляция (in Russian). 28 (2): 34. doi:10.31857/S0869592X20020064. Archived (PDF) from the original on 2024-01-30.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ "ISCS Working Groups: Working Group on the Stage 2 GSSP". International Subcommission on Cambrian Stratigraphy. Archived from the original on 2023-09-26.
- ^ Yaqin Qiang, Junfeng Guo, Guoxiang Li, Zuchen Song, Jiaxin Peng, Jie Sun, Jian Han, Zhifei Zhang (2023). "Aldanella attleborensis (Mollusca) from Cambrian Stage 2 of the Three Gorges Area and Its Stratigraphic Implications". Biology. 12 (2): 1—21. doi:10.3390/biology12020261. PMC 9953005. PMID 36829538.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Yang, Chuan; Bowyer, Fred T.; Condon, Daniel J.; Li, Xian-Hua; Zhu, Maoyan (15 April 2023). "New U-Pb age from the Shuijingtuo Formation (Yangtze Gorges area) and its implications for the Cambrian timescale". Palaeogeography, Palaeoclimatology, Palaeoecology. 616: 111477. Bibcode:2023PPP...61611477Y. doi:10.1016/j.palaeo.2023.111477. ISSN 0031-0182. Retrieved 2024-03-26 – via Elsevier Science Direct.
- ^ Ed Landing, Gerd Geyer, Adam C. Maloof, Martin B. Brasier, Samuel A. Bowring (2013). "Proposal of the global stratotype section and point for the Laolinian Stage (=informal Cambrian Stage 2) as the upper stage of the Terreneuvian Series". International Cambrian Subcommission: 1—43. doi:10.13140/RG.2.1.4198.1842.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Li, Guoxiang; Zhao, Xin; Gubanov, Alexander; Zhu, Maoyan; Na, Lin (1 April 2011). "Early Cambrian Mollusc Watsonella crosbyi: A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2". Acta Geologica Sinica - English Edition. 85 (2): 309–319. Bibcode:2011AcGlS..85..309L. doi:10.1111/j.1755-6724.2011.00400.x. S2CID 129506892.
External links
edit- "GSSP Table - Paleozoic Era". Geologic Timescale Foundation. Archived from the original on 2023-10-08. Retrieved 2024-06-13.
- "GSSPs - The Cambrian System 2019". International Commission on Stratigraphy. Archived from the original on 2023-07-21.
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