The Aalenian () is a subdivision of the

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

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 ...

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 i ...

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 geochron ...

that extends from about 174.7 ±0.8 Ma to about 170.9 ±0.8 Ma (million years ago). It was preceded by the

Toarcian The Toarcian is, in the International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million ...

and succeeded by the

Bajocian In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.9 ±0.8 Ma to around 168.2 ±1.2 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonia ...

Stratigraphic definitions

The Aalenian takes its name from the town of

Aalen Aalen (; Swabian German, Swabian: ''Oole'') is a town located in the eastern part of the German state of Baden-Württemberg, about east of Stuttgart and north of Ulm. It is the seat of the Ostalbkreis district and is its largest town. It is ...

, some 70 km east of

Stuttgart Stuttgart (; ; Swabian German, Swabian: ; Alemannic German, Alemannic: ; Italian language, Italian: ; ) is the capital city, capital and List of cities in Baden-Württemberg by population, largest city of the States of Germany, German state of ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

. The town lies at the northeastern end of the

Swabian Jura The Swabian Jura ( , more rarely ), sometimes also named Swabian Alps in English, is a mountain range in Baden-Württemberg, Germany, extending from southwest to northeast and in width. It is named after the region of Swabia. It is part of th ...

. The name Aalenian was introduced in scientific literature by

Swiss Swiss most commonly refers to: * the adjectival form of Switzerland * Swiss people Swiss may also refer to: Places * Swiss, Missouri * Swiss, North Carolina * Swiss, West Virginia * Swiss, Wisconsin Other uses * Swiss Café, an old café located ...

geologist

Karl Mayer-Eymar Karl David Wilhelm Mayer-Eymar (29 July 1826 – 25 February 1907) was a Franco-Swiss paleontologist and geologist known for his work on classifying the stratigraphy of the Tertiary into 12 stages. He was born Karl Mayer but added the anagram Eyma ...

in 1864. The base of the Aalenian is defined as the place in the stratigraphic column where 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 ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

'' Leioceras'' first appears. The global reference profile (

GSSP A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...

) is located 500 meters north of the village of

Fuentelsaz Fuentelsaz is a municipality located in the province of Guadalajara, Castile-La Mancha, Spain. According to the 2004 census A census (from Latin ''censere'', 'to assess') is the procedure of systematically acquiring, recording, and calculatin ...

in the

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many countries in the Americas **Spanish cuisine **Spanish history **Spanish culture ...

province of Guadalajara Guadalajara ( , ) is a province of Spain, belonging to the autonomous community of Castilla–La Mancha. As of 2019 it had a population of 258,890 people. The population of the province has grown in the last 10 years. It is located in the centre ...

.Cresta ''et al.'' (2001) The top of the Aalenian (the base of the Bajocian) is at the first appearance of ammonite genus ''

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 sh ...

''. In the Tethys domain, the Aalenian contains four ammonite

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

s: *zone of '' Graphoceras concavum'' *zone of '' Brasilia bradfordensis'' *zone of '' Ludwigia murchisonae'' *zone of ''Leioceras opalinum''

References

Notes

Literature

*; 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 ...

. *; 2001: ''The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic)'', Episodes 24(3): pp 166–175. *; 1864: ''Tableau synchronistique des terrains jurassiques. 1 Tabelle'', Zürich. *; 2002
''A compendium of fossil marine animal genera (entry on cephalopoda)''
Bulletins of American Paleontology 364, p 560.

External links

Lower Jurassic timescale
at the website of the subcommission for stratigraphic information of the ICS *Stratigraphic chart o
the Upper
an
Lower
Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy {{Geological history, p, m *01 Geological ages