Early Devonian
| Early Devonian | |||||||||||||||||
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 Map of Earth as it appeared 400 million years ago during the early Devonian, Emsian stage | |||||||||||||||||
 Sample from the Lower Devonian Rhynie chert | |||||||||||||||||
| Chronology | |||||||||||||||||
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| Etymology | |||||||||||||||||
| Chronostratigraphic name | Lower Devonian | ||||||||||||||||
| Geochronological name | Early Devonian | ||||||||||||||||
| Name formality | Formal | ||||||||||||||||
| Usage information | |||||||||||||||||
| Celestial body | Earth | ||||||||||||||||
| Regional usage | Global (ICS) | ||||||||||||||||
| Time scale(s) used | ICS Time Scale | ||||||||||||||||
| Definition | |||||||||||||||||
| Chronological unit | Epoch | ||||||||||||||||
| Stratigraphic unit | Series | ||||||||||||||||
| Time span formality | Formal | ||||||||||||||||
| Lower boundary definition | FAD of the graptolite Monograptus uniformis | ||||||||||||||||
| Lower boundary GSSP | Klonk, Czech Republic 49°51′18″N 13°47′31″E / 49.8550°N 13.7920°E | ||||||||||||||||
| Lower GSSP ratified | 1972[5] | ||||||||||||||||
| Upper boundary definition | FAD of the conodont Polygnathus costatus partitus | ||||||||||||||||
| Upper boundary GSSP | Wetteldorf Richtschnitt section, Wetteldorf, Eifel, Germany 50°08′59″N 6°28′18″E / 50.1496°N 6.4716°E | ||||||||||||||||
| Upper GSSP ratified | 1985[6] | ||||||||||||||||
The Early Devonian is the first of three epochs comprising the Devonian period, corresponding to the Lower Devonian series. It lasted from 419.2 ± 3.2 to 393.3 ± 1.2 and began with the Lochkovian Stage 419.2 ± 3.2 to 410.8 ± 1.2, which was followed by the Pragian from 410.8 ± 3.2 to 407.6 ± 1.2 and then by the Emsian, which lasted until the Middle Devonian began, 393.3± 1.2 million years ago.[7] During this time, the first ammonoids appeared, descending from bactritoid nautiloids. Ammonoids during this time period were simple and differed little from their nautiloid counterparts. These ammonoids belong to the order Agoniatitida, which in later epochs evolved to new ammonoid orders, for example Goniatitida and Clymeniida. This class of cephalopod molluscs would dominate the marine fauna until the beginning of the Mesozoic Era.
References
[edit]- ^ 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.
- ^ 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.
- ^ "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
- ^ Chlupáč, Ivo; Hladil, Jindrich (January 2000). "The global stratotype section and point of the Silurian-Devonian boundary". CFS Courier Forschungsinstitut Senckenberg: 1–8. Retrieved 7 December 2020.
- ^ Ziegler, W.; Klapper, G. (June 1985). "Stages of the Devonian System" (PDF). Episodes. 8 (2): 104–109. doi:10.18814/epiiugs/1985/v8i2/006. Retrieved 18 December 2020.
- ^ Cohen, K.M.; Finney, S.C.; Gibbard, P.L.; Fan, J.-X. (2013). "The ICS International Chronostratigraphic Chart" (PDF). Episodes. 36 (3): 199–204. doi:10.18814/epiiugs/2013/v36i3/002. Retrieved 7 January 2021.
| Authority control databases: National |
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