View source for Earth:Telychian

{{short description|Third stage of the Silurian and last stage of the Llandovery}}
{{Infobox geologic timespan
| name                         = Telychian
| color                        = Telychian
| time_start                   = 438.5
| time_start_uncertainty       = 1.1
| time_end                     = 433.4
| time_end_uncertainty         = 0.8
| image_map                    = Silurian plate tectonics.png
| caption_map                  = Paleogeography of the Telychian, 435 Ma
| image_outcrop                =
| caption_outcrop              =
| image_art                    =
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<!--Chronology-->  
| timeline                     = Silurian
| former_subdivisions          =
| formerly_part_of             =
| partially_contained_in       =
| partially_contains           =
<!--Etymology-->
| name_formality               = Formal
| name_accept_date             =
| alternate_spellings          =
| synonym1                     =
| synonym1_coined              =
| synonym2                     =
| synonym2_coined              =
| synonym3                     =
| synonym3_coined              =
| nicknames                    =
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<!--Usage Information--> 
| celestial_body               = earth
| usage                        = Global ([[Organization:International Commission on Stratigraphy|ICS]])
| timescales_used              = ICS Time Scale
| formerly_used_by             =
| not_used_by                  =
<!--Definition-->
| chrono_unit                  = Age
| strat_unit                   = Stage
| proposed_by                  =
| timespan_formality           = Formal
| lower_boundary_def           = Just above LAD of the [[Biology:Brachiopod|brachiopod]] ''Eocoelia intermedia'', below FAD of lowest succeeding species ''Eocoelia curtisi''  
| lower_gssp_location          = Cefn-cerig Road Section, Llandovery, Wales, {{wipe|United Kingdom}}
| lower_gssp_coords            = {{Coord|51.9700|N|3.7900|W|display=inline}}
| lower_gssp_accept_date       = 1984<ref name='Holland1985'>{{cite journal |last1=Holland |first1=C. |title=Series and Stages of the Silurian System |journal=Episodes |date=June 1985 |volume=8 |issue=2 |pages=101–103 |doi=10.18814/epiiugs/1985/v8i2/005 |url=http://www.episodes.org/journal/view.html?volume=8&number=2&spage=101&vmd=A#1 |access-date=15 December 2020|doi-access=free }}</ref>
| upper_boundary_def           = Imprecise. Currently placed between [[Biology:Acritarch|acritarch]] biozone 5 and LAD of ''[[Biology:Pterospathodus|Pterospathodus amorphognathoides]]''. [[Earth:Llandovery Epoch#GSSP|See Llandovery]] for more info.
| upper_gssp_candidates        = None
| upper_def_candidates         = A conodont boundary (Ireviken datum 2) which is close to the ''murchisoni'' graptolite biozone.
| upper_gssp_location          = Hughley Brook, Apedale, UK
| upper_gssp_coords            = {{Coord|52.5811|N|2.6389|W|display=inline}}
| upper_gssp_accept_date       = 1980<ref name="rhuddanianICS">{{Cite web|url=http://www.stratigraphy.org/GSSP/Rhuddanian.html|title=GSSP for the Rhuddanian Stage|website=International Commission on Stratigraphy}}</ref>
<!--Atmospheric and Climatic Data-->
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}}
In the geologic timescale, the '''Telychian''' is the third and final age of the [[Earth:Llandovery Epoch|Llandovery Epoch]] of the [[Earth:Silurian|Silurian]] Period of the [[Earth:Paleozoic|Paleozoic]] Era of the [[Earth:Phanerozoic|Phanerozoic]] Eon. The Telychian Age was between 438.5 ± 1.2 million years ago (Ma) and 433.4 ± 0.8 Ma. The Telychian Age succeeds the [[Earth:Aeronian|Aeronian]] Age and precedes the [[Earth:Sheinwoodian|Sheinwoodian]] Age.<ref name="a2004">{{cite book |isbn=9780521786737|title=A Geologic Time Scale 2004|last1=Gradstein|first1=Felix M.|last2=Ogg|first2=James G.|last3=Smith|first3=Alan G.|year=2004}}</ref> The name of the interval is derived from the Pen-lan-Telych Farm near Llandovery, Powys, Wales. The GSSP is located within the Wormwood Formation.

It ended with the [[Earth:Ireviken event|Ireviken event]].

== Ireviken event ==
{{main|Earth:Ireviken event}}
The [[Earth:Ireviken event|Ireviken event]] was the first of three relatively minor [[Biology:Extinction event|extinction event]]s (the Ireviken, [[Earth:Mulde event|Mulde]], and [[Earth:Lau event|Lau]] events) during the Silurian Period. It occurred at the [[Earth:Llandovery epoch|Llandovery]]/[[Earth:Wenlock epoch|Wenlock]] boundary (mid Silurian, {{Ma|Wenlock|{{period start error|Wenlock}}&nbsp;million years ago}}). The event is best recorded at Ireviken, Gotland, where over 50% of [[Biology:Trilobite|trilobite]] species became extinct; 80% of the global [[Biology:Conodont|conodont]] species also become extinct in this interval.

=== Anatomy of the event ===
The event lasted around 200,000 years, spanning the base of the Wenlock Epoch.<ref name=Munnecke2003/><ref name=Jeppsson1997>{{cite book|author =Jeppsson, L|year=1997|chapter=The anatomy of the Mid-Early Silurian Ireviken Event and a scenario for P-S events|editor1=Brett, C.E. |editor2=Baird, G.C. |title=Paleontological Events: Stratigraphic, Ecological, and Evolutionary Implications|publisher=Columbia University Press|location=New York|pages=451–492}}</ref>

It comprises eight extinction "datum points"—the first four being regularly spaced, every 30,797 years, and linked to the Milankovic obliquity cycle.<ref name=Jeppsson1997/> The fifth and sixth probably reflect maxima in the precessional cycles, with periods of around 16.5 and 19 ka.<ref name=Jeppsson1997/> The final two data are much further spaced, so harder to link with Milankovic changes.<ref name=Jeppsson1997/>

=== Effects ===
The mechanism responsible for the event originated in the deep oceans, and made its way into the shallower shelf seas. Correspondingly, shallow-water reefs were barely affected, while [[Earth:Pelagic zone|pelagic]] and [[Earth:Hemipelagic sediment|hemipelagic]] organisms such as the [[Biology:Graptolite|graptolite]]s, conodonts and trilobites were hit hardest.<ref name=Munnecke2003/>

=== Geochemistry ===
Subsequent to the first extinctions, excursions in the [[Biology:Δ13C|δ<sup>13</sup>C]] and [[Biology:Δ18O|δ<sup>18</sup>O]] records are observed; δ<sup>13</sup>C rises from +1.4‰ to +4.5‰, while δ<sup>18</sup>O increases from −5.6‰ to −5.0‰.<ref name=Munnecke2003/>

== References ==
{{reflist}}

{{Geological history|p|p}}

[[Category:Llandovery epoch]]
[[Category:Silurian geochronology]]



{{Sourceattribution|Telychian}}