The Hettangian is the earliest

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 lowest

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 ...

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 (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

Period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

of 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 ...

. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the

Rhaetian The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age ...

(part of the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

Period) and is followed by the

Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch 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 and is ...

. In European stratigraphy the Hettangian is a part of the time span in which the

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 ...

was deposited. An example is the British

Blue Lias The Blue Lias is a geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassi ...

, which has an upper Rhaetian to Sinemurian age. Another example is the lower Lias from the

Northern Limestone Alps The Northern Limestone Alps (german: Nördliche Kalkalpen), also called the Northern Calcareous Alps, are the ranges of the Eastern Alps north of the Central Eastern Alps located in Austria and the adjacent Bavarian lands of southeastern Germany. ...

where well-preserved but very rare ammonites, including

Alsatites ''Alsatites '' is an extinct genus of cephalopod belonging to the Ammonite subclass. They lived during the Early Jurassic, Hettangian till the Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower J ...

, have been found.

Stratigraphic definitions

The Hettangian was introduced in the literature by Swiss palaeontologist,

Eugène Renevier Eugène Renevier (26 March 18314 May 1906) Swiss geologist, was born at Lausanne, Switzerland, as a descendant of a noble family. After about three years of study at the polytechnical school of Stuttgart, Renevier in 1851 went to Geneva to study ...

, in 1864. The stage takes its name from

Hettange-Grande Hettange-Grande (; ; Lorraine Franconian: ''Grouss-Hetténgen'') is a commune in the Moselle department in Grand Est in north-eastern France. The town gives its name to the Hettangian age, the earliest age of the Jurassic period of the geologic ...

, a town in north-eastern

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

, just south of the border with

Luxembourg Luxembourg ( ; lb, Lëtzebuerg ; french: link=no, Luxembourg; german: link=no, Luxemburg), officially the Grand Duchy of Luxembourg, ; french: link=no, Grand-Duché de Luxembourg ; german: link=no, Großherzogtum Luxemburg is a small lan ...

on the main road from

Luxembourg City Luxembourg ( lb, Lëtzebuerg; french: Luxembourg; german: Luxemburg), also known as Luxembourg City ( lb, Stad Lëtzebuerg, link=no or ; french: Ville de Luxembourg, link=no; german: Stadt Luxemburg, link=no or ), is the capital city of the Lu ...

Metz Metz ( , , lat, Divodurum Mediomatricorum, then ) is a city in northeast France located at the confluence of the Moselle and the Seille rivers. Metz is the prefecture of the Moselle department and the seat of the parliament of the Grand E ...

. The base of the Hettangian Stage (which is also the base of the Lower Jurassic

Series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used in ...

and the entire Jurassic

System A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment (systems), environment, is described by its boundaries, ...

) is defined as the place in the stratigraphic column where fossils 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) ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Psiloceras ''Psiloceras'' is an extinct genus of ammonite. ''Psiloceras'' is among the earliest known Jurassic ammonites, and the appearance of the earliest ''Psiloceras'' species form the definition for the base of the Jurassic. Unlike most earlier ammoni ...

'' 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 b ...

) for the base was defined 2010 for an exposure of the

Kendlbach Formation The Kendlbach Formation is a Late Triassic (latest Rhaetian) to Early Jurassic (Hettangian) geological formation in Austria and Italy. It contains the Global Boundary Stratotype Section and Point (GSSP) for the Hettangian stage (the first stage o ...

at the Kuhjoch section in the Karwendel Mountains of western

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

.GSSP Table
The top of the Hettangian Stage (the base of the Sinemurian) is at the first appearances of ammonite

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 ''Vermiceras'' is an ammonite that belongs to the order Ammonitida. Its shell is evolute and is covered in nonbranching ribs. Its whorls do not increase in size very fast, but there are many revolutions on its shell, which is fairly narrow. It h ...

'' and '' Metophioceras''.

Biostratigraphy

The Hettangian contains three 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 of ...

s in the Tethys domain: *zone of '' Schlotheimia angulata'' *zone of '' Alsatites liasicus'' *zone of '' Psiloceras planorbis''

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 Henry VIII of England, King Henry VIII in 1534, it is the oldest university press A university press is an academic publishing hou ...

. *: ''Notices géologiques et paléontologiques sur les Alpes Vaudoises, et les régions environnantes. I. Infralias et Zone à Avicula contorta (Étage Rhaetien) des Alpes Vaudoises'' Bulletin de la Société Vaudoise des Sciences Naturelles 8, p. 39-97.

External links

GeoWhen Database - HettangianLower 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 *01 Geological ages