The Barremian is an

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

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 geochron ...

(or a chronostratigraphic stage) between 125.77 Ma (

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a subdivision of the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

Epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

(or Lower Cretaceous Series). It is preceded by the

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.6 ± 2 Ma and 125.77 (million years ago). The Hauterivian is preceded by the Valangi ...

and followed by the

Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...

Stage.See Gradstein ''et al.'' (2004) or the online geowhen database (link below)

Stratigraphic definitions

The original type locality for the Barremian Stage is in the vicinity of the village of Barrême,

Alpes-de-Haute-Provence Alpes-de-Haute-Provence (sometimes abbreviated as AHP; ; ; ), formerly until 1970 known as Basses-Alpes (, ), is a department in the Provence-Alpes-Côte d'Azur region of France, bordering Alpes-Maritimes and Italy to the east, Var to the sou ...

, France. Henri Coquand defined the stage and named it in 1873. The base of the Barremian is determined by the first appearance of the

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

s '' Spitidiscus hugii'' and ''Spitidiscus vandeckii''. The end of the Barremian is determined by the

geomagnetic reversal A geomagnetic reversal is a change in the Earth's Dipole magnet, dipole magnetic field such that the positions of magnetic north and magnetic south are interchanged (not to be confused with North Pole, geographic north and South Pole, geograp ...

at the start of the M0r chronozone, which is biologically near the first appearance of the ammonite '' Paradeshayesites oglanlensis''.

Regional equivalents

The Barremian falls in the Gallic epoch, a subdivision of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

that is no longer used by the ICS. It overlaps the lower part of the stage, which is sometimes used in western European stratigraphy. In

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, the late Coahulian and the early Comanchean correspond to the Barremian. In

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, it falls within the Mokoiwian, and in

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

it corresponds to the late Aritan.

Subdivision

The Barremian is often subdivided into two substages or subages, Lower/Early and Upper/Late Barremian. In the Tethys domain, the Barremian stage contains eleven ammonite biozones: * zone of '' Pseudocrioceras waagenoides'' * zone of '' Colchidites sarasini'' * zone of '' Imerites giraudi'' * zone of '' Hemihoplites feraudianus'' * zone of '' Gerhardtia sertousi'' * zone of '' Ancyloceras vandenheckii'' * zone of '' Coronites darsi'' * zone of '' Kotetishvilia compressissima'' * zone of '' Nicklesia pulchella'' * zone of ''Nicklesia nicklesi'' * zone of ''Spitidiscus hugii''

References

Notes

Literature

* (1907): Le Barrémien supérieur à faciès Urgonien de Brouzet-lès-Alais (Gard). ''Mémoires de la Société Géologique de France, Paléontologie'' 15(37): 5-42. *; (2004): A Geologic Time Scale 2004,

Cambridge University Press Cambridge University Press was the university press of the University of Cambridge. Granted a letters patent by King Henry VIII in 1534, it was the oldest university press in the world. Cambridge University Press merged with Cambridge Assessme ...

. * (2006): Assessment of diachronism of biostratigraphic boundaries by magnetochronological calibration of zonal scales for the Lower Cretaceous of the Tethyan and Boreal belts. ''Doklady Earth Sciences'' 409(6): 843-846.

External links

GeoWhen Database - BarremianMid-Cretaceous timescale
at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic chart of the Lower Cretaceous
at the website of Norges Network of offshore records of geology and stratigraphy {{Cretaceous Footer *04 Geological ages Cretaceous geochronology