The Ornatenton Formation is a

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 143.1 Mya. ...

marine formation in

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 ...

that is middle

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 165.3 ± 1.1 Ma (million years ago) and 161.5 ± 1.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

in age. The formation represents a shallow marine environment.Rauhut, Oliver W.M., Hübner, Tom R., and Lanser, Klaus-Peter, 2016, "A new megalosaurid theropod dinosaur from the late Middle Jurassic (Callovian) of north-western Germany: Implications for theropod evolution and faunal turnover in the Jurassic", ''Palaeontologia Electronica'' 19.2.26A: 1-65Mönnig, E. 1993, "Die Ornatenton-Formation in NW Deutschland." ''Newsletter in Stratigraphy'', 28(2/3):131-150. (In German)Riegraf, W. 1994, "Der Ornatenton in Deutschland und seine Äquivalente", pp. 7-72. In Martill, D.M. and Hudson, J.D. (eds.), ''Fossilien aus Ornatenton und Oxford Clay.'' Goldschneck-Verlag, Korb. (In German)

History and naming

The Ornatenton Formation was named by Gert Bloos, Gerd Dietl and Günter Schweigert in 2005. This southern German Jurassic layer had already been previously referred to as the 'Ornatenton' by

Friedrich August von Quenstedt Friedrich August von Quenstedt (10 July 1809 – 21 December 1889) was a German geologist and palaeontologist. Life Von Quenstedt was born at Eisleben in Saxony, and educated at the Humboldt University of Berlin. After a period as assistant i ...

in 1857. The formation was named after the ammonite ''Ammonitus ornatus'', today known as '' Kosmoceras ornatum''. A type locality has not yet been determined.

Definition and distribution area

The Ornatenton Formation is composed mainly of

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

with some iron-oolith benches,

glauconitic Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek () m ...

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s, and a horizon of carbonate

concretion A concretion is a hard and compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes a ...

s. It stretches from the

Eastern Alps The Eastern Alps are usually defined as the area east of a line from Lake Constance and the Alpine Rhine valley, up to the Splügen Pass at the Main chain of the Alps, Alpine divide, and down the Liro (Como), Liro River to Lake Como in the south. ...

to the

Rhine valley Rhine Valley (German: ''Rheintal'' ) is the valley, or any section of it, of the river Rhine in Europe. Particular valleys of the Rhine or any of its sections: * Alpine Rhine Valley ** Chur Rhine Valley (or Grisonian Rhine Valley; , or sometimes ...

, and the facies area stretches into

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

where it is known as the 'argovian' facies. In southern Germany, the formation is underlain by the Variansmergel Formation and regionally overlapped by the Kandern or Impressamergel Formation, while in the Wutach area it is replaced by the Wutach Formation. Further east, in the

French Alps The French Alps are the portions of the Alps mountain range that stand within France, located in the Auvergne-Rhône-Alpes and Provence-Alpes-Côte d'Azur regions. While some of the ranges of the French Alps are entirely in France, others, such a ...

, it dovetails with the Sengenthal Formation. Its thickness varies from a few meters in 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 ...

up to about in the

Plettenberg Plettenberg (; Westphalian: ''Plettmert'') is a town in the Märkischer Kreis, in North Rhine-Westphalia, Germany. Geography Plettenberg is located to the west of the Sauerland hills. The highest elevation of the town area is in the Ebbe Mount ...

area.

Time frame and subdivision

The Ornatenton Formation is divided into three subformations: the Macrocephalae Subformation, the Ornatenton Subformation, and the Glaukonitsandmergel Subformation. Some of the sediments of the Ornatenton Formation are dated to the upper

Bathonian In the geologic timescale the Bathonian is an age (geology), age and stage (stratigraphy), stage of the Middle Jurassic. It lasted from approximately 168.2 ±1.2 annum, Ma to around 165.3 ±1.1 Ma (million years ago). The Bathonian Age succeeds ...

, but most were deposited during the

. The formation locally reaches into the lower Oxfordian.

Paleofauna

The remains of dinosaurs and marine reptiles are known from the Ornatenton Formation alongside a rich invertebrate fauna including the oyster '' Gryphaea dilatata'' along with the ammonites '' Clydoniceras discus'', '' Bullatimorphies bullatus'', '' Macrocephalites gracilis'', '' Reineckeia anceps'', '' Erymnoceras coronatum'', '' Peltoceras athleta'', '' Quenstedtoceras lamberti'', '' Quenstedtoceras mariae'', and '' Cardioceras cordatum''.Lange, W. 1973, "Ammoniten und Ostreen (Biostratigraphie, Ökologie, Zoogeographie) des Calloviums - Oxfordium Grenzbereichs im Wiehengebirge." ''Münstersche Forschungen Geologie und Paläontologie'', 27:1-209. (In German)Klassen, H. 1984. ''Geologie des Osnabrücker Berglandes XVI.'' Naturwissenschaftliches Museum, Osnabrück. (In German)

References

{{reflist Jurassic Germany Jurassic System of Europe Callovian Stage Mudstone formations Sandstone formations