In the geologic timescale, the Roadian is an age or stage of the Permian. It is the earliest or lower of three subdivisions of the Guadalupian Epoch or Series. The Roadian lasted between 273.01 and 266.9 million years ago (Ma). It was preceded by the Kungurian and followed by the Wordian.[3]
| Roadian | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chronology | |||||||||||||
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| Etymology | |||||||||||||
| Name formality | Formal | ||||||||||||
| 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 | FAD of the Conodont Jinogondolella nanginkensis | ||||||||||||
| Lower boundary GSSP | Stratotype Canyon, Guadalupe Mountains, Texas, USA 31°52′36″N 104°52′36″W / 31.8767°N 104.8768°W | ||||||||||||
| Lower GSSP ratified | 2001[2] | ||||||||||||
| Upper boundary definition | FAD of the Conodont Jinogondolella aserrata | ||||||||||||
| Upper boundary GSSP | Guadalupe Pass, Guadalupe Mountains, Texas, USA 31°51′57″N 104°49′58″W / 31.8658°N 104.8328°W | ||||||||||||
| Upper GSSP ratified | 2001[2] | ||||||||||||
Stratigraphy
editIn 1961, the regional timescale used for the southeastern US had the Wordian and Capitanian as subdivisions of the Guadalupian.[4] Efforts to correlate the Permian stratigraphy of the southeastern US with that of Russia led to the conclusion that between the Wordian stage and the Russian Artinskian stage, another stage needed to be introduced.[5] This stage, the Roadian Stage, was established in 1968 and took its name from the Road Canyon Formation in Brewster County, Texas, formerly considered the lower (oldest) part of the Word Formation.[6] The stage was added to the internationally used IUGS timescale in 2001.[7]
The base of the Roadian is defined as the place in the stratigraphic record where fossils of conodont species Jinogondolella nankingensis first appears. The global reference profile for the base (the GSSP) is located in Stratotype Canyon in the Guadalupe Mountains, Texas (31°52′36″N 104°52′36″W / 31.87667°N 104.87667°W). The top of the Roadian (the base of the Wordian Stage) is at the first appearance of fossils of conodont species Jinogondolella aserrata.
Life
edit
Some studies suggested that Olson’s Extinction, a worldwide loss of terrestrial vertebrate life occurred during the Early Guadalupian (Roadian, Wordian),[8] but the temporal resolution of most studies only indicates that this possible extinction event indicates around the Kungurian/Roadian boundary.[9][10] Studies using higher-resolution stratigraphic data and the fossilized birth-death model suggest that this even is actually a slow decline over 20 Ma that started in the Sakmarian and that may have extended into the Roadian.[11][12]
Notable formations
edit- Cherry Canyon Formation (New Mexico, Texas, USA)
- Road Canyon Formation (Texas, USA)
References
edit- ^ "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
- ^ a b "GSSP for Roadian Stage". International Commission on Stratigraphy. Retrieved 13 December 2020.
- ^ Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press
- ^ Glenister, B.F. & Furnish, W.M.; 1961: The Permian ammonoids of Australia, Journal of Paleontology 35(4), pp 673–736.
- ^ Nassichuk, W.W.; 1964: Pennsylvanian and Permian rocks in the Parry Islands Group, Canadian Arctic Archipelago, Report of activities, field
- ^ Furnish & Glenister (1968)
- ^ Glenister, B.F.; Wardlaw, B.R.; Lambert, L.L.; Spinosa, C.; Bowring, S.A.; Erwin, D.H.; Menning, M. & Wilde, G.L.; 1999: Proposal of Guadalupian and Component Roadian, Wordian and Capitanian Stages as International Standards for the Middle Permian Series, Permophiles 34: pp 3–11.
- ^ Sahney, S. & Benton, M.J. (2008). "Recovery from the most profound mass extinction of all time". Proceedings of the Royal Society B: Biological Sciences. 275 (1636): 759–65. doi:10.1098/rspb.2007.1370. PMC 2596898. PMID 18198148.
- ^ Brocklehurst, Neil; Day, Michael O.; Rubidge, Bruce S.; Fröbisch, Jörg (12 April 2017). "Olson's Extinction and the latitudinal biodiversity gradient of tetrapods in the Permian". Proceedings of the Royal Society B: Biological Sciences. 284 (1852): 20170231. doi:10.1098/rspb.2017.0231. ISSN 0962-8452. PMC 5394676.
- ^ Brocklehurst, Neil (10 June 2020). "Olson's Gap or Olson's Extinction? A Bayesian tip-dating approach to resolving stratigraphic uncertainty". Proceedings of the Royal Society B: Biological Sciences. 287 (1928): 20200154. doi:10.1098/rspb.2020.0154. ISSN 0962-8452. PMC 7341920. PMID 32517621.
- ^ Didier, Gilles; Laurin, Michel (9 December 2021). "Distributions of extinction times from fossil ages and tree topologies: the example of mid-Permian synapsid extinctions". PeerJ. 9: e12577. doi:10.7717/peerj.12577. ISSN 2167-8359. PMC 8667717.
- ^ Didier, Gilles; Laurin, Michel (June 2024). "Testing extinction events and temporal shifts in diversification and fossilization rates through the skyline Fossilized Birth-Death (FBD) model: The example of some mid-Permian synapsid extinctions". Cladistics. 40 (3): 282–306. doi:10.1111/cla.12577. ISSN 0748-3007. PMID 38651531.
Literature
editExternal links
edit- GeoWhen Database - Roadian
- Upper Paleozoic stratigraphic chart at the website of the subcommission for stratigraphic information of the ICS