Working Groups and Task Group of the International Subcommission on Cambrian Stratigraphy.
The Cambrian Subcommission has devised and approved a plan for subdividing the Cambrian System into four series and 10 stages. This four-fold division of the Cambrian supersedes all previous three-part (“Lower”, “Middle” and “Upper” Cambrian) and two-part (“Lower” and “Upper” Cambrian) subdivisions that had been used in the past and which had varying meanings in different parts of the world. The two lower series will embrace two stages each, and the upper two series will embrace three stages each. Through June 2013, two series (Terreneuvian and Furongian) and five stages (Fortunian, Drumian, Guzhangian, Paibian and Jiangshanian) had been ratified with GSSPs. In addition, an ASSP has been ratified for the Jiangshanian Stage. During 2018, the Miaolingian (previously Series 3) and the Wuliuan (Stage 5) have been added.
Remaining stages and series to be defined by GSSPs are Stage 2 through 4 (and Series 2), and Stage 10. Until GSSPs for these stages and series are ratified, their boundary positions are considered provisional.
The Cambrian Subcommission has formed a Working Group to examine issues concerning the definition of the Fortunian Stage base. The base of the stage, which is conterminant with the bases of the Terreneuvian Series, Cambrian System, Paleozoic Erathem and Phanerozoic Eonothem, was ratified in 1992.
Chaired by Maoyan Zhu (China)
A Working Group has been assembled to investigate the definition of the base of the Fortunian Stage, which is conterminant with the bases of the Terreneuvian Series, Cambrian System, Paleozoic Erathem and Phanerozoic Eonothem. The GSSP for the base of the Fortunian Stage and conterminant boundaries was ratified in 1992, and will remain the standard unless modification of the definition is recommended by the Working Group, and then approved by the International Subcommission on Cambrian Stratigraphy, the International Commission on Stratigraphy and the International Union of Geological Sciences.
Chaired by Michael Steiner (Germany)
The base of the second stage of the Cambrian has not yet been defined, and a criterion for defining the boundary has not yet been determined. Several fossils have been suggested as criteria for determining the boundary level. Among them, the First Appearance Datum (FAD) levels of two widely distributed microfossils, have emerged as leading candidates. They are the micromollusk (rostroconch) Watsonella crosbyi and the mollusk Aldanella attleborensis.
Chaired by Xingliang Zhang (China)
The base of Cambrian Stage 3, which is also the base of Cambrian Series 2, has not been defined. This boundary is expected to be marked by a significant and widely recognizable event that will divide the lower half of the Cambrian subequally into a subtrilobitic series and a trilobite-dominated series. The FAD of trilobites, with its historic aspects, is a possibility for the boundary position. However, precise correlation of a horizon marked solely by the FAD of trilobites will be difficult because trilobites appear in strata at slightly different times in different regions. It is more likely that the FAD of a Small Shell Fossil (SSF) will be selected as the primary marker of the boundary.
Chaired by James B. Jago (Australia)
The base of provisional Stage 4 has not been formally defined. One level, the base of the interval bearing the eodiscoid trilobites Hebediscus, Calodiscus, Serrodiscus, and Triangulaspis, referred to as the HCST band has been suggested as a potential stage marker. Another possibility for the base of Stage 4 is a level coinciding with the FAD of a single trilobite species. Possibilities include a species of Olenellus (s.l.), Redlichia (s.l.), Judomia or Bergeroniellus.
Chaired by Per Ahlberg (Sweden)
The base of Cambrian Stage 10, the uppermost stage of the Furongian Series and the Cambrian System, is undefined. The Cambrian Subcommission favours marking the base at or close to the FAD of the cosmopolitan agnostoid Lotagnostus americanus. L. americanus co-occurs with the polymerid trilobite Hedinaspis in certain regions, and the FAD of Hedinaspis can be used as a proxy marker for the level of L. americanus where L. americanus is absent. Two conodont species, Eoconodontus notchpeakensis and Cordylodus andresi, also have been suggested as possible markers for the base of the uppermost Cambrian stage.
Chaired by Malgorzata Moczydlowska-Vidal (Sweden)
Webmaster is Michael Streng (Sweden)
The Web Page Task Group facilitates web-based communication about progress toward definition of chronostratigraphic boundary positions within the Cambrian System.