Keuper
 | This article needs additional citations for verification. (October 2010) |
| System | Series | Stage | Age ( Ma )
|
European lithostratigraphy |
|---|---|---|---|---|
| Jurassic | Lower | Hettangian | younger | Lias |
| Triassic | Upper | Rhaetian | 201.4–208.5 | |
| Keuper | ||||
| Norian | 208.5–227.0 | |||
| Carnian | 227.0–237.0 | |||
| Middle | Ladinian | 237.0–242.0 | ||
| Muschelkalk | ||||
| Anisian | 242.0–247.2 | |||
| Bunter or Buntsandstein | ||||
| Lower | Olenekian | 247.2–251.2 | ||
| Induan | 251.2–251.9 | |||
| Permian | Lopingian | Changhsingian | older | |
| Zechstein | ||||
| Major lithostratigraphic units of northwest Europe with the ICS's geologic timescale of the Triassic.[1] | ||||
The Keuper is a
Lower Jurassic Lias
or other Early Jurassic strata.
The Keuper together with the Muschelkalk and the Buntsandstein form the Germanic Trias Group, a characteristic sequence of rock strata that gave the Triassic its name.[3]
Exposure
The Upper Triassic is well exposed in
Lorraine and Luxembourg; it extends from Basel on the east side of the Rhine into Hanover, and through England into Scotland and north-east Ireland; it appears flanking the central plateau of France and in the Pyrenees and Sardinia. The Keuper sequence is linked by name to the Keuper Uplands
area of southern Germany.
In south
Burma, eastern Siberia and in Spitsbergen. The upper portion of the Karoo Supergroup of South Africa and part of the Otapiri stage of New Zealand
are probably of Rhaetian age.
Germany
In Germany and adjacent parts of western and central Europe, the Keuper unit is divided into three groups:
- Upper Keuper
- The upper part of this division is often a grey Microlestes antiquus and Triglyptzas Fraasi. The name "Rhaetic" is derived from the Rhaetic Alps where the beds are well developed; they occur also in central France, the Pyrenees and England. In South Tirol and the Judicarian Mountains, the Rhaetic is represented by the Kosseneibeds. In the Alpine region, the presence of coral beds gives rise to the so-called Lithodendron Kalk.
- Hauptkeuper or Gipskeuper, the middle
- The middle division is thicker than either of the others (at Göttingen, 450 m, 1,480 ft); it consists of a marly series below, grey, red and green marls, with Stubensandstein.
- Kohlenkeuper, Unterkeuper or Lettenkohle, the lower
- The lower division consists mainly of grey clays and schieferletten with white, grey and brightly colored sandstone and dolomitic limestone.
The
Lorraine region of France. A 4-metre (13 ft) coal is found on this horizon in the Ore Mountains on the border between Germany and the Czech Republic, and another, 2 metres thick (7 ft), has been mined in Upper Silesia, now in Poland
.
Great Britain
In Great Britain the 'Keuper' is no longer a formally recognised geological division. The one-time Keuper Marls are now redesignated as the Mercia Mudstone Group. The underlying Keuper Sandstone is now the Helsby Sandstone Formation at the top of the Sherwood Sandstone Group. Traditionally it contained the following subdivisions:
- Grey, red and green marls, black shales, and so-called white (3.0–45.7 m, 10–150 ft). Upper Keuper marl, red and grey marls and shales with rock salt, 240–910 m (800–3,000 ft). As in Germany, there are one or more bone beds in the English Rhaetic with a similar assemblage of fossils.
- Lower Keuper
- Sandstone, marls and thin sandstones at the top, red and white sandstones (including the so-called waterstones) below, with breccias and conglomerates at the base, 46–76 m (150–250 ft).
- Basal conglomerate
- A shore or scree breccia derived from local materials; it is well developed in the Mendip district. The rocksalt beds vary from 25 cm (1 inch) to 30 metres (100 ft) in thickness; they are extensively worked (mined and pumped) in Cheshire, Middlesbrough and Antrim.
The Keuper covers a large area in the
Midlands and around the flanks of the Pennine range; it reaches southward to the east Devon coast, northeastward into Yorkshire
and northwestward into Northern Ireland and southernmost Scotland.
Fossils
The Keuper is not rich in
Lepidotus
.
Labyrinthodonts represented by the footprints of Cheirotherium and the bones of Mastodonsaurus (originally called Labyrinthodon) and Capitosaurus. Among the reptiles are Hyperodapedon, Palaeosaurus, Zanclodon, Nothosaurus, Henodus and Belodon. The first fossil mammals also make their appearance at this time and the early beetle Triamyxa
is also known from the Keuper.
Notes
References
- Ogg, James G.; Ogg, Gabi M.; Gradstein, Felix M. (2016). "Triassic". A Concise Geologic Time Scale: 2016. Elsevier. pp. 133–149. ISBN 978-0-444-63771-0.
- Howe, John Allen (1911). . In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 15 (11th ed.). Cambridge University Press. p. 766.
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