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 geochronol ...

, the Sinemurian 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 in the Early or Lower Jurassic

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 by ...

or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the

Hettangian The Hettangian is the earliest age and lowest stage of the Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (My ...

and is followed by the Pliensbachian. In Europe the Sinemurian age, together with the Hettangian age, saw the deposition of the lower

Lias Lias may refer to: Geology * Lias Formation, a geologic formation in France *Lias Group, a lithostratigraphic unit in western Europe * Early Jurassic, an epoch People * Godfrey Lias, British author * Mohd Shamsudin Lias (born 1953), Malaysian ...

, in Great Britain known as the Blue Lias.

Stratigraphic definitions

The Sinemurian Stage was defined and introduced into scientific literature by French palaeontologist Alcide d'Orbigny in 1842. It takes its name from the French town of Semur-en-Auxois, near

Dijon Dijon (, , ) (dated) * it, Digione * la, Diviō or * lmo, Digion is the prefecture of the Côte-d'Or department and of the Bourgogne-Franche-Comté region in northeastern France. the commune had a population of 156,920. The earlies ...

. The

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

soil formed from the Jurassic

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

of the region is in part responsible for the character of the classic Sancerre wines. The base of the Sinemurian Stage is at the first appearance of the

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

genera 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 nomenclat ...

'' Vermiceras'' and ''

Metophioceras ''Metoioceras'' is an extinct genus of cephalopod belonging to the Ammonite subclass which lived during the Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest s ...

'' in the stratigraphic record. A global reference profile ( GSSP or golden spike) for the Sinemurian Stage is located in a cliff north of the hamlet of

East Quantoxhead East Quantoxhead is a village in the district of Somerset West and Taunton, from West Quantoxhead, east of Williton, and west of Bridgwater, within the Quantock Hills Area of Outstanding Natural Beauty in Somerset, England. History Above the ...

, east of Watchet,

Somerset ( en, All The People of Somerset) , locator_map = , coordinates = , region = South West England , established_date = Ancient , established_by = , preceded_by = , origin = , lord_lieutenant_office =Lord Lieutenant of Somerset , lord_ ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

.See for the description of the GSSP Bloos & Page (2001) Eteoderoceras armatum sinemurian

The top of the Sinemurian (the base of the Pliensbachian) is at the first appearances of the ammonite species '' Bifericeras donovani'' and ammonite genus ''

Apoderoceras ''Apoderoceras'' is an extinct genus of cephalopod belonging to the ammonite subclass. Biostratigraphic significance The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of genus ''Apoderoceras'' and of '' ...

''. The Sinemurian contains six ammonite biozones in the Tethys domain: *zone of '' Echioceras raricostatum'' *zone of '' Oxynoticeras oxynotum'' *zone of ''

Asteroceras obtusum ''Asteroceras'' is an extinct genus of cephalopod belonging to the Ammonite subclass. These fast-moving nektonic carnivores lived during the Triassic and Jurassic periods (from 205.6 to 189.6 Ma). Species *''Asteroceras blakei'' Spath, 1925 *'' ...

'' *zone of '' Caenisites turneri'' *zone of ''

Arnioceras semicostatum ''Arnioceras'' is an extinct genus of large, evolute, discoidal ammonite from the Lower Jurassic. The shell is normally coiled so that all whorls are exposed. Sides bear strong sharp ribs that are straight until reaching the ventrolateral edg ...

'' *zone of '' Arietites bucklandi''

References

Sources

*; 2001: ''Global Stratotype Section and Point for base of the Sinemurian Stage (Lower Jurassic)'', Episodes 25(1), pp. 22–28
PDF
*; 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 Henry VIII of England, King Henry VIII in 1534, it is the oldest university press A university press is an academic publishing hou ...

. *; 1842: ''Paléontologie française. 1. Terrains oolitiques ou jurassiques'', Bertrand, Paris.

External links

GeoWhen Database - SinemurianLower Jurassic timescale
at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic chart of the Lower Jurassic
at the website of Norges Network of offshore records of geology and stratigraphy {{Geological history, p, m *02 Geological ages

Stratigraphic definitions

References

Sources

See also

External links