Cambrian Stage 2 Explained

Cambrian Stage 2
Color:Cambrian Stage 2
Time Start:529
Time Start Prefix:~
Time End:521
Time End Prefix:~
Timeline:Cambrian
Name Formality:Informal
Celestial Body:earth
Usage:Global (ICS)
Timescales Used:ICS Time Scale
Chrono Unit:Age
Strat Unit:Stage
Timespan Formality:Formal
Lower Boundary Def:Not formally defined
Lower Def Candidates:First appearance of small shelly fauna or Archaeocyathids
Lower Gssp Candidates:None
Upper Boundary Def:Not formally defined
Upper Def Candidates:FAD of Trilobites
Upper Gssp Candidates:None

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.[1] [2] Neither the upper nor lower boundary has yet been defined by the International Commission on Stratigraphy.[3] [4] The preferred definitions for the lower boundary are the first appearance of the molluscs Watsonella crosbyi or Aldanella attleborensis around million years ago.[5] [6] 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.[7] The proposed upper boundary might be the first appearance of trilobites around million years ago.

Naming

The name "Laolinian" after the Laolin village in Yunnan, China, was proposed for the Stage 2 in 2012.[8]

Stratotype

Possible 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.[9]

External links

Notes and References

  1. Kouchinsky. Artem. Bengtson, Stefan . Missarzhevsky, Vladimir V. . Pelechaty, Shane . Torssander, Peter . Val'kov, Anatolij K. . Carbon isotope stratigraphy and the problem of a pre-Tommotian stage in Siberia. Geological Magazine. 24 September 2001. 138. 4. 387–396. 10.1017/S0016756801005684. 2001GeoM..138..387K. 3884375 .
  2. 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 . 10.1017/s0016756815001089. 2016GeoM..153..750L . 132867265 .
  3. Web site: GSSP List ICS. ICS. 2024-03-26. dead. https://web.archive.org/web/20121115175854/http://www.stratigraphy.org/GSSP/index.html. 15 November 2012.
  4. P. Yu. Parkhaev, Yu. E. Demidenko, M. A. Kulsha. 2020. Zooproblematica Mobergella radiolata as Index Species of the Lower Cambrian Stage Units. Стратиграфия. Геологическая корреляция. 28. 2. 34. 10.31857/S0869592X20020064. ru. https://web.archive.org/web/20240130053043/http://csl.isc.irk.ru/bd/%D0%96%D1%83%D1%80%D0%BD%D0%B0%D0%BB%D1%8B/%D0%A1%D1%82%D1%80%D0%B0%D1%82%D0%B8%D0%B3%D1%80%D0%B0%D1%84%D0%B8%D1%8F.%20%D0%93%D0%B5%D0%BE%D0%BB%D0%BE%D0%B3%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%B0%D1%8F%20%D0%BA%D0%BE%D1%80%D1%80%D0%B5%D0%BB%D1%8F%D1%86%D0%B8%D1%8F%202020%20%D0%A228/%E2%84%96%202/33-54.pdf#page=2. 2024-01-30. live.
  5. Web site: ISCS Working Groups: Working Group on the Stage 2 GSSP. International Subcommission on Cambrian Stratigraphy. https://web.archive.org/web/20230926093607/http://www.palaeontology.geo.uu.se/ISCS/ISCS_working_groups.html#2. 2023-09-26. live.
  6. 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. 10.3390/biology12020261. free . 36829538 . 9953005 .
  7. 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 . . 616 . 111477 . 10.1016/j.palaeo.2023.111477 . 2023PPP...61611477Y . 0031-0182 . 2024-03-26 . Elsevier Science Direct.
  8. 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. 10.13140/RG.2.1.4198.1842.
  9. Li. Guoxiang. Zhao, Xin . Gubanov, Alexander . Zhu, Maoyan . Na, Lin . Early Cambrian Mollusc Watsonella crosbyi: A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2. Acta Geologica Sinica - English Edition. 1 April 2011. 85. 2. 309–319. 10.1111/j.1755-6724.2011.00400.x. 2011AcGlS..85..309L . 129506892 .

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