TheFamennianis the later of twofaunal stagesin theLate Devonianepoch. The most recent estimate for its duration is that it lasted from around 371.1 to 359.3 million years ago.[8]An earlier 2012 estimate, still used by the International Commission on Stratigraphy, is that it lasted from 372.15 million years ago to 358.86 million years ago. It was preceded by theFrasnianstage and followed by theTournaisianstage.
| Famennian | |||||||||||||||||
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| 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 | FADof the conodontPalmatolepis subperlobata LAD of the conodontPalmatolepis bogartensis | ||||||||||||||||
| Lower boundary GSSP | Coumiac quarry,Montagne Noire, France 43°27′41″N3°02′25″E/ 43.4613°N 3.0403°E | ||||||||||||||||
| Lower GSSP ratified | 1993[5] | ||||||||||||||||
| Upper boundary definition | FAD of theconodontSiphonodella sulcata(discovered to have biostratigraphic issues as of 2006).[6] | ||||||||||||||||
| Upper boundary GSSP | La Serre,Montagne Noire,France 43°33′20″N3°21′26″E/ 43.5555°N 3.3573°E | ||||||||||||||||
| Upper GSSP ratified | 1990[7] | ||||||||||||||||
Major events
editIn the seas, a novel major group ofammonoidcephalopodscalledclymeniidsappeared, underwent tremendousdiversificationand spread worldwide, then just as suddenly went extinct.
The beginning of the Famennian is marked by the final stages of a majorextinction event,theKellwasser Event,which is the largest component of the Late Devonian mass extinction. The end of the Famennian experiences a smaller but still quite severe extinction event, theHangenberg Event.A brief episode of glaciation, possibly linked to the Hangenberg event, occurred during the late Famennian, the first in a series of short glaciations that preceded theLate Palaeozoic ice ageof theCarboniferousandPermianperiods.[9]
Subdivisions
editTheInternational Commission on Stratigraphydivides the Famennian into four informal substages based primarily onconodontzonation. The Famennian corresponds to four historical subdivisions inGermanstratigraphy: the Nehdenian, Hembergian, Dasbergian, and Wocklumian (from oldest to youngest). However, these are based solely on ammonoid zonation and do not precisely correspond to the informal ICS subdivisions. The Uppermost Famennian substage (approximating the Wocklumian) is also known as the Strunian in theArdennesregion.[8]
North American subdivisions of the Famennian include the Chautauquan, Canadaway, Conneaut, Conneautan, Conewango and Conewangan.
Name and definition
editThe Famennian Stage was proposed in 1855 by Belgian geologistAndré Hubert Dumontand was accepted for the upper stage of the Upper Devonian by the Subcommission on Devonian Stratigraphy in 1981.[10]It is named afterFamenne,a natural region in southern Belgium. The lower GSSP, ratified in 1993, is located within theCoumiac FormationnearCessenonin southern France.[5][8]
Since 2017, the base of the Famennian has been defined by a distinctive turnover of conodonts, particularly the last appearance ofPalmatolepis bogartensis,the first appearance ofPalmatolepis subperlobata,and an increase in the abundance ofPalmatolepis ultima.It was previously defined by the start of thePalmatolepis triangularisconodont zone, but later studies showed thatP. triangularisfirst appeared slightly later than the main conodont turnover in the GSSP.[8][11]
A 2012 ICS timescale based on rough radioisotopic records estimated the Famennian began around 372.2 ± 1.6 Ma, and ended at 358.9 ± 0.4 Ma. In 2020 this was revised to a start at 371.1 ± 1.1 Ma and an end at 359.3 ± 0.3 Ma.[8]
References
edit- ^Kaufmann, B.; Trapp, E.; Mezger, K. (2004). "The numerical age of the Upper Frasnian (Upper Devonian) Kellwasser horizons: A new U-Pb zircon date from Steinbruch Schmidt(Kellerwald, Germany)".The Journal of Geology.112(4):495–501.Bibcode:2004JG....112..495K.doi:10.1086/421077.
- ^Algeo, T. J. (1998). "Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events".Philosophical Transactions of the Royal Society B: Biological Sciences.353(1365):113–130.doi:10.1098/rstb.1998.0195.
- ^Parry, S. F.; Noble, S. R.; Crowley, Q. G.; Wellman, C. H. (2011)."A high-precision U–Pb age constraint on the Rhynie Chert Konservat-Lagerstätte: time scale and other implications".Journal of the Geological Society.168(4). London: Geological Society:863–872.doi:10.1144/0016-76492010-043.
- ^"International Chronostratigraphic Chart"(PDF).International Commission on Stratigraphy.September 2023.RetrievedDecember 16,2024.
- ^abKlapper, G.; Feist, R.; Becker, R.; House, M. (December 1993)."Definition of the Frasnian/Famennian Stage boundary".16(4):433–441.Retrieved19 December2020.
{{cite journal}}:Cite journal requires|journal=(help) - ^Kaiser, Sandra (1 April 2009)."The Devonian/Carboniferous boundary stratotype section (La Serre, France) revisited".Newsletters on Stratigraphy.43(2):195–205.doi:10.1127/0078-0421/2009/0043-0195.Retrieved7 December2020.
- ^Paproth, Eva; Feist, Raimund; Flajs, Gerd (December 1991)."Decision on the Devonian-Carboniferous boundary stratotype"(PDF).Episodes.14(4):331–336.doi:10.18814/epiiugs/1991/v14i4/004.
- ^abcdeBecker, R. T.; Marshall, J. E. A.; Da Silva, A. -C.; Agterberg, F. P.; Gradstein, F. M.; Ogg, J. G. (2020-01-01), Gradstein, Felix M.; Ogg, James G.; Schmitz, Mark D.; Ogg, Gabi M. (eds.),"Chapter 22 - The Devonian Period",Geologic Time Scale 2020,Elsevier, pp.733–810,ISBN978-0-12-824360-2,retrieved2022-02-21
- ^Lakin, J. A.; Marshall, J. E. A.; Troth, I.; Harding, I. C. (15 April 2016)."Greenhouse to icehouse: a biostratigraphic review of latest Devonian–Mississippian glaciations and their global effects".Geological Society, London, Special Publications.423:439–464.doi:10.1144/SP423.12.S2CID130689152.Retrieved13 September2022.
- ^Thorez, Jacques; Dreesen, Roland; Streel, Maurice (2006)."Frasnian".Geologica Belgica.9(1–2):27–45. Archived fromthe originalon May 1, 2014.Retrieved16 March2013.
- ^Spalleta, Claudia; Perri, Maria Cristina; Over, D. Jeffrey; Corradini, Carlo (2017)."Famennian (Upper Devonian) conodont zonation: revised global standard"(PDF).Bulletin of Geosciences.92(1):31–57.doi:10.3140/bull.geosci.1623.
See also
edit- List of fossil sites(with link directory)