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Llandovery Epoch
| Llandovery | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
.png) A map of Earth as it appeared 440 million years ago during the Llandovery Epoch, Aeronian Age | |||||||||||||
| Chronology | |||||||||||||
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| Etymology | |||||||||||||
| Name formality | Formal | ||||||||||||
| Name ratified | 1984 | ||||||||||||
| 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 Akidograptus ascensus | ||||||||||||
| Lower boundary GSSP | Dob's Linn, Moffat, UK 55°26′24″N 3°16′12″W / 55.4400°N 3.2700°W | ||||||||||||
| Lower GSSP ratified | 1984[4][5] | ||||||||||||
| Upper boundary definition | Imprecise. Currently placed between acritarch biozone 5 and last appearance of Pterospathodus amorphognathoides. See text for more info. | ||||||||||||
| Upper boundary definition candidates | A conodont boundary (Ireviken datum 2) which is close to the murchisoni graptolite biozone. | ||||||||||||
| Upper boundary GSSP candidate section(s) | None | ||||||||||||
| Upper boundary GSSP | Hughley Brook, Apedale, UK 52°34′52″N 2°38′20″W / 52.5811°N 2.6389°W | ||||||||||||
| Upper GSSP ratified | 1980[6] | ||||||||||||
In the geological timescale, the Llandovery Epoch (from 443.8 ± 1.5 million years ago to 433.4 ± 0.8 million years ago) occurred at the beginning of the Silurian Period. The Llandoverian Epoch follows the massive Ordovician-Silurian extinction events, which led to a large decrease in biodiversity and an opening up of ecosystems.
Widespread reef building started in this period and continued into the Devonian Period when rising water temperatures are thought to have bleached out the coral by killing their photo symbionts.
The Llandoverian Epoch ended with the Ireviken event which killed off 50% of trilobite species, and 80% of the global conodont species.
- ^ Jeppsson, L.; Calner, M. (2007). "The Silurian Mulde Event and a scenario for secundo—secundo events". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 93 (02): 135–154. doi:10.1017/S0263593300000377.
- ^ Munnecke, A.; Samtleben, C.; Bickert, T. (2003). "The Ireviken Event in the lower Silurian of Gotland, Sweden-relation to similar Palaeozoic and Proterozoic events". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (1): 99–124. doi:10.1016/S0031-0182(03)00304-3.
- ^ "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. September 2023. Retrieved December 16, 2024.
- ^ Lucas, Sepncer (6 November 2018). "The GSSP Method of Chronostratigraphy: A Critical Review". Frontiers in Earth Science. 6: 191. Bibcode:2018FrEaS...6..191L. doi:10.3389/feart.2018.00191.
- ^ Holland, C. (June 1985). "Series and Stages of the Silurian System" (PDF). Episodes. 8 (2): 101–103. doi:10.18814/epiiugs/1985/v8i2/005. Retrieved 11 December 2020.
- ^ "GSSP for the Rhuddanian Stage". International Commission on Stratigraphy.
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