View source for Earth:Coniacian

{{Short description|Age of the Late Cretaceous}}
{{Infobox geologic timespan
| name                         = Coniacian
| color                        = Coniacian
| time_start                   = 89.8
| time_start_uncertainty       = 0.3
| time_end                     = 86.3
| time_end_uncertainty         = 0.5
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<!--Chronology-->  
| timeline                     = Cretaceous
| formerly_part_of             =
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<!--Etymology-->
| name_formality               = Formal
| name_accept_date             =
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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             =
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<!--Definition-->
| chrono_unit                  = Age
| strat_unit                   = Stage
| proposed_by                  =
| type_section                 =
| timespan_formality           = Formal
| lower_boundary_def           = [[Earth:First appearance datum|FAD]] of the Inoceramid [[Biology:Bivalvia|Bivalve]] ''[[Biology:Cremnoceramus|Cremnoceramus deformis erectus]]''
| lower_gssp_location          = Salzgitter-Salder quarry, {{wipe|Germany}}
| lower_gssp_coords            = {{Coord|52.1243|N|10.3295|E}}
| lower_gssp_accept_date       = May 2021
| upper_boundary_def           = FAD of the Inoceramid Bivalve ''[[Biology:Cladoceramus|Cladoceramus undulatoplicatus]]''
| upper_gssp_location          = Olazagutia, {{wipe|Spain}}
| upper_gssp_coords            = {{Coord|42.8668|N|2.1968|W}}
| upper_gssp_accept_date       = January 2013<ref>{{cite journal |last1=Lamolda |first1=M. |last2=Paul |first2=C. |last3=Peryt |first3=D. |last4=Pons |first4=J. |title=The Global Boundary Stratotype and Section Point (GSSP) for the base of the Santonian Stage, "Cantera de Margas", Olazagutia, northern Spain |journal=Episodes |date=March 2014 |volume=37 |issue=1 |pages=2–13 |doi=10.18814/epiiugs/2014/v37i1/001 |url=https://www.researchgate.net/publication/263378103 |access-date=24 December 2020|doi-access=free }}</ref>
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}}
The '''Coniacian''' is an [[Earth:Age (geology)|age]] or [[Physics:Stage (stratigraphy)|stage]] in the geologic timescale. It is a subdivision of the [[Earth:Late Cretaceous|Late Cretaceous]] [[Earth:Epoch (geology)|Epoch]] or [[Earth:Upper Cretaceous|Upper Cretaceous]] [[Earth:Series (stratigraphy)|Series]] and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by the [[Earth:Turonian|Turonian]] and followed by the [[Earth:Santonian|Santonian]].<ref>See Gradstein ''et al.'' (2004) for a detailed version of the [[Organization:International Commission on Stratigraphy|ICS]]' geologic timescale</ref>

== Stratigraphic definitions ==
The Coniacian is named after the city of [[Earth:Cognac, France|Cognac]] in the {{wipe|France}} region of Saintonge. It was first defined by French geologist Henri Coquand in 1857.

The base of the Coniacian Stage is at the first appearance of the [[Biology:Inoceramidae|inoceramid]] bivalve species ''[[Biology:Cremnoceramus|Cremnoceramus deformis erectus]]''. The official reference profile for the base (a GSSP) is located in Salzgitter-Salder, Lower Saxony, Germany.

The top of the Coniacian (the base of the Santonian Stage) is defined by the appearance of the inoceramid bivalve ''[[Biology:Cladoceramus|Cladoceramus undulatoplicatus]]''.

The Coniacian overlaps the regional Emscherian Stage of {{wipe|Germany}}, which is roughly coeval with the Coniacian and Santonian Stages. In [[Earth:Magnetostratigraphy|magnetostratigraphy]], the Coniacian is part of magnetic chronozone C34, the so-called Cretaceous Magnetic Quiet Zone, a relatively long period with normal polarity.

=== Sequence stratigraphy and geochemistry ===
After a maximum of the global sea level during the early Turonian, the Coniacian was characterized by a gradual fall of the sea level. This cycle is in [[Earth:Sequence stratigraphy|sequence stratigraphy]] seen as a first order cycle. During the middle Coniacian a shorter, second order cycle, caused a temporary rise of the sea level (and global transgressions) on top of the longer first order trend. The following [[Earth:Marine regression|regression]] (Co1, at 87,0 Ma) separates the Middle from the Upper Coniacian Substage. An even shorter third order cycle caused a new transgression during the Late Coniacian.

Beginning in the Middle Coniacian, an [[Earth:Anoxic event|anoxic event]] (OAE-3) occurred in the [[Earth:Atlantic Ocean|Atlantic Ocean]], causing large scale deposition of black shales in the Atlantic domain. The anoxic event lasted till the Middle Santonian (from 87.3 to 84.6 Ma) and is the longest and last such event during the Cretaceous period.<ref>See Meyers ''et al.'' (2006)</ref>

=== Subdivision ===
The Coniacian is often subdivided into Lower, Middle and Upper Substages. It encompasses three [[Biology:Ammonite|ammonite]] [[Earth:Biozone|biozone]]s in the [[Earth:Tethys Ocean|Tethys domain]]:
* zone of ''Paratexanites serratomarginatus''
* zone of ''Gauthiericeras margae''
* zone of ''[[Biology:Peroniceras|Peroniceras tridorsatum]]''

In the boreal domain the Coniacian overlaps just one ammonite biozone: that of ''[[Biology:Forresteria|Forresteria petrocoriensis]]''

== References ==

=== Notes ===
<references />

=== Literature ===
* {{aut|Gradstein, F.M.; Ogg, J.G. & Smith, A.G.}}; '''2004''': ''A Geologic Time Scale 2004'', {{wipe|Cambridge University Press}}.
* {{aut|Meyers, P.A.; Bernasconi, S.M. & Forster, A.}}; '''2006''': ''Origins and accumulation of organic matter in expanded Albian to Santonian black shale sequences on the Demerara Rise, South American margin'', Organic Geochemistry '''37''', pp 1816–1830.

==External links==
* [http://www.stratigraphy.org/bak/geowhen/stages/Coniacian.html GeoWhen Database - Coniacian]
* [http://stratigraphy.science.purdue.edu/charts/Timeslices/3_Late_Cret.pdf Late Cretaceous timescale], at the website of the subcommission for stratigraphic information of the ICS
* [https://web.archive.org/web/20040511104934/http://norges.uio.no/timescale/Fig18.1_Cret_colA.pdf Stratigraphic chart of the Late Cretaceous], at the website of Norges Network of offshore records of geology and stratigraphy

{{Geological history|p|m}}


[[Category:Coniacian| ]]
[[Category:Late Cretaceous|*03]]
[[Category:Cretaceous geochronology]]

{{Sourceattribution|Coniacian}}