View source for Toarcian

{{short description|Fourth and last age of the Early Jurassic}}
{{Infobox geologic timespan
| name = Toarcian
| color = Toarcian
| time_start = 184.2 
| time_start_uncertainty = 0.3
| time_end = 174.7 
| time_end_uncertainty = 0.8
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<!--Chronology-->  
| timeline = Jurassic
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<!--Etymology-->
| name_formality = Formal
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<!--Usage Information--> 
| celestial_body = earth
| usage = Global ([[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 =
| type_section =
| timespan_formality = Formal
| lower_boundary_def = [[Peniche, Portugal]]
| lower_gssp_location = [[First appearance datum|FAD]] of the [[Ammonite]] ''[[Dactylioceras|D. (E.) simplex]]''
| lower_gssp_coords = {{Coor|39.3708|N|9.3853|W|display=inline}}
| lower_gssp_accept_date = 2014<ref>{{cite journal |last1=da Rocha |first1=Rogério Bordalo |last2=Mattioli |first2=Emanuela |last3=Duarte |first3=Luís Vítor |last4=Pittet |first4=Bernard |last5=Elmi |first5=Serge |last6=Mouterde |first6=René |last7=Cabral |first7=Maria Cristina |last8=Comas-Rengifo |first8=Maria José |last9=Gómez |first9=Juan José |last10=Goy |first10=António |last11=Hesselbo |first11=Stephen P. |last12=Jenkyns |first12=Hugh C. |last13=Littler |first13=Kate |last14=Mailliot |first14=Samuel |last15=Veiga de Oliveira |first15=Luiz Carlos |last16=Osete |first16=Maria Luisa |last17=Nicola |first17=Perilli |last18=Pinto |first18=Susana |last19=Ruget |first19=Christiane |last20=Suan |first20=Guillaume |title=Base of the Toarcian Stage of the Lower Jurassic defined by the Global Boundary Stratotype Section and Point (GSSP) at the Peniche section (Portugal) |journal=Episodes |date=September 2016 |volume=39 |issue=3 |pages=460–481 |doi=10.18814/epiiugs/2016/v39i3/99741 |doi-access=free |hdl=10261/140775 |hdl-access=free }}</ref>
| upper_boundary_def = FAD of the Ammonites ''[[Leioceras opalinum]]'' and ''[[Leioceras lineatum]]''
| upper_gssp_location = [[Fuentelsaz]], Spain
| upper_gssp_coords = {{Coord|41.1708|N|1.8333|W|display=inline}}
| upper_gssp_accept_date = 2000<ref>{{cite journal |last1=Cresta |first1=S. |last2=Goy |first2=A. |last3=Arias |first3=C. |last4=Barrón |first4=E. |last5=Bernad |first5=J. |last6=Canales |first6=M. |last7=García-Joral |first7=F. |last8=García-Romero |first8=E |last9=Gialanella |first9=P. |last10=Gómez |first10=J. |last11=González |first11=J. |last12=Herrero |first12=C. |last13=Martínez |first13=G. |last14=Osete |first14=M. |last15=Perilli |first15=N. |last16=Villalaín |first16=J. |title=The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic) |journal=Episodes |date=September 2001 |volume=24 |issue=3 |pages=166–175 |doi=10.18814/epiiugs/2001/v24i3/003 |doi-access=free |url=https://timescalefoundation.org/references/Aalenian.pdf |access-date=13 December 2020}}</ref>
<!--Atmospheric and Climatic Data-->
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}}
The '''Toarcian''' is, in the [[International Commission on Stratigraphy|ICS]]' [[geologic timescale]], an [[age (geology)|age]] and [[stage (stratigraphy)|stage]] in the [[Early Jurassic|Early or Lower Jurassic]]. It spans the time between 184.2 [[Megaannum|Ma (million years ago)]] and 174.7 ±0.8 Ma.<ref name="benton, 2012">{{cite book|last=Benton|first=Michael J.|title=Prehistoric Life|year=2012|publisher=Dorling Kindersley|location=Edinburgh, Scotland|isbn=978-0-7566-9910-9|pages=44–45}}</ref>  It follows the [[Pliensbachian]] and is followed by the [[Aalenian]].<ref>For a detailed geologic timescale see Gradstein ''et al.'' (2004)</ref>

The Toarcian Age began with the [[Toarcian Oceanic Anoxic Event]], a major [[anoxic event]] associated with marine extinctions and increased global temperatures  that sets its fossil faunas apart from the previous [[Pliensbachian]] age. It is believed to have ended with a global cooling event known as the Comptum Cooling Event, although whether it represented a worldwide event is controversial.<ref>{{cite journal |last1=Henriques |first1=Maria Helena Paiva |last2=Canales |first2=Maria Luisa |date=September–October 2013 |title=Ammonite-benthic Foraminifera turnovers across the Lower-Middle Jurassic transition in the Lusitanian Basin (Portugal) |url=https://www.sciencedirect.com/science/article/abs/pii/S0016699513000727 |journal=[[Geobios]] |volume=46 |issue=5 |pages=395–408 |doi=10.1016/j.geobios.2013.06.002 |bibcode=2013Geobi..46..395H |access-date=23 November 2022|hdl=10316/27258 |hdl-access=free }}</ref>

==Stratigraphic definitions==
The Toarcian takes its name from the city of [[Thouars]], just south of [[Saumur]] in the [[Loire Valley]] of [[France]]. The stage was introduced by French palaeontologist [[Alcide d'Orbigny]] in 1842, after examining [[stratum|rock strata]] of this age in a [[quarry]] near Thouars.

In Europe this period is represented by the upper part of the [[Lias Group|Lias]].

The base of the Toarcian is defined as the place in the stratigraphic record where the [[ammonite]] [[genus]] ''[[Eodactylites]]'' first appears. A global reference profile (a [[GSSP]]) for the base is [[List of Global Boundary Stratotype Sections and Points|located]] at [[Peniche, Portugal]]. The top of the stage is at the first appearance of ammonite genus ''[[Leioceras]]''.

In the [[Tethys Ocean|Tethys domain]], the Toarcian contains the following ammonite [[biozone]]s:
*zone of ''[[Pleydellia|Pleydellia aalensis]]''
*zone of ''[[Dumortieria|Dumortieria pseudoradiosa]]''
*zone of ''[[Phlyseogrammoceras|Phlyseogrammoceras dispansum]]''
*zone of ''[[Grammoceras|Grammoceras thouarcense]]''
*zone of ''[[Haugia|Haugia variabilis]]''
*zone of ''[[Hildoceras|Hildoceras bifrons]]''
*zone of ''[[Harpoceras|Harpoceras serpentinum]]''
*zone of ''[[Dactylioceras|Dactylioceras tenuicostatum]]''

== References ==
{{reflist}}

==Sources==
*{{aut|Gradstein, F.M.; Ogg, J.G. & Smith, A.G.}}; '''2004''': ''A Geologic Time Scale 2004'', [[Cambridge University Press]].
*{{aut|d´Orbigny, A.C.V.M.D.}}; '''1842''': ''Paléontologie française. 1. Terrains oolitiques ou jurassiques'', Bertrand, Paris. {{in lang|fr}}
*Elmi, S., Rulleau, L., Gabilly, J. & Mouterde, R. 1997: Toarcien. ''In'': Cariou, E. & Hantzpergue, P. (eds): Biostratigraphie du Jurassique ouest-européen et méditerranéen. ''Bulletin du Centre des Recherches, Elf Explor. Prod. Mém.'', 17.

==External links==
*[http://www.stratigraphy.org/bak/geowhen/stages/Toarcian.html GeoWhen Database - Toarcian]
*[http://stratigraphy.science.purdue.edu/charts/Timeslices/6_LowerJurassic.pdf Lower Jurassic timescale], at the website of the subcommission for stratigraphic information of the ICS
*[https://web.archive.org/web/20060518101459/http://norges.uio.no/timescale/Fig17.1_Jur_colB.pdf Stratigraphic chart of the Lower Jurassic], at the website of Norges Network of offshore records of geology and stratigraphy

{{Jurassic Footer}}
{{Geological history|p|m}}

[[Category:Toarcian| ]]
[[Category:Early Jurassic|*04]]
[[Category:Geological ages]]