Cambrian Stage 2

Cambrian Stage 2
~529 – ~521 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Chronology
−540 — – −535 — – −530 — – −525 — – −520 — – −515 — – −510 — – −505 — – −500 — – −495 — – −490 — – −485 — N ♇ P a l e o z o i c Ediacaran C a m b r i a n O T e r r e n e u v i a n S e r i e s 2 M i a o l i n g. F u r o n g. E Fortunian "Stage 2" "Stage 3" "Stage 4" Wuliuan Drumian Guzhangian Paibian Jiangshanian "Stage 10" Tremadocian               ← Orsten Fauna ← Burgess Shale ← Kaili biota ← Archaeocyatha extinction ← Emu Bay Shale ← Sirius Passet biota ← Chengjiang biota ← First Trilobites ← SSF diversification, first brachiopods & archaeocyatha ← First halkieriids, mollusсs, hyoliths SSF ← Baykonurian glaciation ← Dresbachian extinction   Major Glacial period Subdivision of the Cambrian according to the ICS, as of 2024.[1] Vertical axis scale: Millions of years ago
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

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]

Naming

The name "Laolinian" after the Laolin village in Yunnan, China, was proposed for the Stage 2 in 2012.[9]

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.[10]

References

1. "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. December 2024. Retrieved January 2, 2025.
2. 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.
3. 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.
4. "GSSP List ICS". ICS. Archived from the original on 15 November 2012. Retrieved 2024-03-26.
5. 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.
6. "ISCS Working Groups: Working Group on the Stage 2 GSSP". International Subcommission on Cambrian Stratigraphy. Archived from the original on 2023-09-26.
7. 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.
8. 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.
9. 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.
10. 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

• "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.