In the

geologic timescale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochr ...

, the Bajocian is an

age Age or AGE may refer to: Time and its effects * Age, the amount of time someone or something has been alive or has existed ** East Asian age reckoning, an Asian system of marking age starting at 1 * Ageing or aging, the process of becoming older ...

and

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma (million years ago). The Bajocian Age succeeds the

Aalenian The Aalenian () is a subdivision of the Middle Jurassic Epoch/Series of the geologic timescale that extends from about 174.1 Ma to about 170.3 Ma (million years ago). It was preceded by the Toarcian and succeeded by the Bajocian. Stratigraphi ...

Age and precedes the

Bathonian In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age. Str ...

Age.

Stratigraphic definitions

The Bajocian Stage takes its name from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

name (Bajocae) of the town of Bayeux, in the region of

Normandy Normandy (; french: link=no, Normandie ; nrf, Normaundie, Nouormandie ; from Old French , plural of ''Normant'', originally from the word for "northman" in several Scandinavian languages) is a geographical and cultural region in Northwestern ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

. The stage was named and introduced in scientific literature by French palaeontologist

Alcide d'Orbigny Alcide Charles Victor Marie Dessalines d'Orbigny (6 September 1802 – 30 June 1857) was a French naturalist who made major contributions in many areas, including zoology (including malacology), palaeontology, geology, archaeology and anthropol ...

in 1842. The base of the Bajocian stage is defined as the place in the stratigraphic column where

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s of the ammonite

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

Hyperlioceras ''Hyperlioceras'' is an extinct genus of cephalopod included in the ammonitid family Graphoceratidae that lived during the Bajocian stage of the Middle Jurassic. The type species is ''Hyperlioceras discites'' (Waagen, 18567) Morphology The shel ...

'' first appear. A global reference profile (a

GSSP A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. The effort to define GSSPs is conducted ...

) for the base is located at Murtinheira, close to

Cabo Mondego Cabo Mondego is a cape located in central western Portugal bordering the Atlantic Ocean. It is the westernmost point of the Serra da Boa Viagem and is located three kilometers north of Figueira da Foz Figueira da Foz (), also known as Figueir ...

Portugal Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...

.The GSSP is described by Pavia & Enay (1997) The top of the Bajocian (the base of the Bathonian) is at the first appearance of ammonite species ''Parkinsonia convergens''.

Subdivision

The Bajocian is often divided into Lower/Early and Upper/Late subages or substages. In the Tethys domain, the Bajocian contains seven ammonite

biozone In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa, as opposed to a lithostratigraphic unit which is defined by the lithological properties ...

s: *zone of ''Parkinsonia parkinsoni'' *zone of '' Garantiana garantiana'' *zone of '' Strenoceras niortense'' *zone of '' Stephanoceras humphriesianum'' *zone of '' Sonninia propinquans'' *zone of '' Witchellia laeviuscula'' *zone of ''

Hyperlioceras discites ''Hyperlioceras'' is an extinct genus of cephalopod included in the ammonitid family Graphoceratidae that lived during the Bajocian stage of the Middle Jurassic. The type species is ''Hyperlioceras discites'' (Waagen, 18567) Morphology The she ...

References

Notes

Literature

*; 2004: ''A Geologic Time Scale 2004'',

Cambridge University Press Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by King Henry VIII in 1534, it is the oldest university press in the world. It is also the King's Printer. Cambridge University Pre ...

. *; 1842: ''Paléontologie française. 1. Terrains oolitiques ou jurassiques'', 642 pp., Bertrand, Paris. *; 1997: ''Definition of the Aalenian-Bajocian Stage boundary'', Episodes, 20(1): pp 16–22. *; 2002
''A compendium of fossil marine animal genera (entry on cephalopoda)''
Bulletins of American Paleontology 364, p 560. *

External links

Jurassic-Cretaceous
an
Lower Jurassic
timescales, at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic chart of the Upper Jurassic
at the website of Norges Network of offshore records of geology and stratigraphy {{Geological history, p, m *02 Geological ages