Editing Jurassic (section)

==== Middle Jurassic ====
The Aalenian is named after the city of [[Aalen]] in Germany. The Aalenian was defined by Swiss geologist [[Karl Mayer-Eymar]] in 1864. The lower boundary was originally between the dark clays of the Black Jurassic and the overlying clayey sandstone and [[Iron|ferruginous]] oolite of the Brown Jurassic sequences of southwestern Germany.<ref name="Ogg-2012" /> The GSSP for the base of the Aalenian is located at [[Fuentelsaz]] in the [[Sistema Ibérico|Iberian range]] near [[Guadalajara, Spain]], and was ratified in 2000. The base of the Aalenian is defined by the first appearance of the ammonite ''[[Leioceras|Leioceras opalinum]]''.<ref>{{Cite journal|last1=Barrón|first1=Eduardo|last2=Ureta|first2=Soledad|last3=Goy|first3=Antonio|last4=Lassaletta|first4=Luis|date=August 2010|title=Palynology of the Toarcian–Aalenian Global Boundary Stratotype Section and Point (GSSP) at Fuentelsaz (Lower–Middle Jurassic, Iberian Range, Spain)|url=https://linkinghub.elsevier.com/retrieve/pii/S0034666710000898|journal=Review of Palaeobotany and Palynology|language=en|volume=162|issue=1|pages=11–28|doi=10.1016/j.revpalbo.2010.04.003|bibcode=2010RPaPa.162...11B }}</ref>

Alcide d'Orbigny in 1842 named the Bajocian Stage after the town of [[Bayeux]] (Latin: ''Bajoce'') in Normandy, France. The GSSP for the base of the Bajocian is located in the Murtinheira section at [[Cabo Mondego]], Portugal; it was ratified in 1997. The base of the Bajocian is defined by the first appearance of the ammonite ''[[Hyperlioceras|Hyperlioceras mundum]].''<ref>{{Cite journal|last1=Pavia|first1=G.|last2=Enay|first2=R.|date=1997-03-01|title=Definition of the Aalenian-Bajocian Stage boundary|journal=Episodes|volume=20|issue=1|pages=16–22|doi=10.18814/epiiugs/1997/v20i1/004|issn=0705-3797|doi-access=free}}</ref>

The Bathonian is named after the city of [[Bath, Somerset|Bath]], England, introduced by Belgian geologist [[Jean Baptiste Julien d'Omalius d'Halloy|d'Omalius d'Halloy]] in 1843, after an incomplete section of oolitic limestones in several quarries in the region. The GSSP for the base of the Bathonian is Ravin du Bès, Bas-Auran area, [[Alpes-de-Haute-Provence|Alpes de Haute Provence]], France; it was ratified in 2009. The base of the Bathonian is defined by the first appearance of the ammonite ''[[Gonolkites|Gonolkites convergens]]'', at the base of the [[Zigzagiceras|''Zigzagiceras zigzag'']] ammonite zone''.''<ref>{{cite journal|last1=López|first1=Fernández|last2=Rafael|first2=Sixto|last3=Pavia|first3=Giulio|last4=Erba|first4=Elisabetta|last5=Guiomar|first5=Myette|last6=Paiva Henriques|first6=María Helena|last7=Lanza|first7=Roberto|last8=Mangold|first8=Charles|last9=Morton|first9=Nicol|last10=Olivero|first10=Davide|last11=Tiraboschi|first11=Daniele|date=2009|title=The Global Boundary Stratotype Section and Point (GSSP) for base of the Bathonian Stage (Middle Jurassic), Ravin du Bès Section, SE France|journal=Episodes|volume=32|issue=4|pages=222–248|doi=10.18814/epiiugs/2009/v32i4/001|doi-access=free |s2cid=51754708 |df=dmy}}</ref>

The Callovian is derived from the [[Latinisation of names|Latinized]] name of the village of [[Kellaways]] in [[Wiltshire]], England, and was named by Alcide d'Orbigny in 1852, originally the base at the contact between the [[Forest Marble Formation]] and the [[Cornbrash Formation]]. However, this boundary was later found to be within the upper part of the Bathonian.<ref name="Ogg-2012" /> The base of the Callovian does not yet have a certified GSSP. The working definition for the base of the Callovian is the first appearance of ammonites belonging to the genus ''[[Kepplerites]].<ref name="jurassic.stratigraphy.org">{{Cite web|title=International Commission on Stratigraphy-Subcommission on Jurassic Stratigraphy|url=https://jurassic.stratigraphy.org/our-work|access-date=2021-04-09|website=jurassic.stratigraphy.org}}</ref>''