Английская Википедия:Cambrian Stage 2

Материал из Онлайн справочника
Перейти к навигацииПерейти к поиску

Шаблон:Short description Шаблон:Infobox geologic timespan 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] Neither the upper nor lower boundary has yet been defined by the International Commission on Stratigraphy.[2] The preferred definitions for the lower boundary are the first appearance of the molluscs Watsonella crosbyi or Aldanella attleborensis around Шаблон:Period start million years ago.[3] 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.[4] The proposed upper boundary might be the first appearance of trilobites around Шаблон:Period start million years ago.[2]

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.[5]

References

Шаблон:Reflist

Шаблон:Cambrian footer Шаблон:Geological history

Шаблон:Geochronology-stub Шаблон:Cambrian-stub