Lias Group

Source: Wikipedia, the free encyclopedia.
For other uses, see Lias.
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 Lias Group or Lias is a

rock strata) found in a large area of western Europe, including the British Isles, the North Sea, the Low Countries and the north of Germany. It consists of marine limestones, shales, marls and clays
.

Lias is a Middle English term for hard limestone, used in this specific sense by geologists since 1833.

geologic timescale. It is now more specifically known that the Lias is Rhaetian to Toarcian in age (over a period of c. 20 million years between 200 to 180 million years ago) and thus also includes a part of the Triassic
. The use of the name "Lias" for a unit of time is therefore slowly disappearing.

Subdivisions

In southern

formations
(from top to base):

In the East Midlands Shelf the Lias is divided into the following

formations
(from top to base):

In the

formations
(from top to base):

In South Wales only the Blue Lias is present.

The Lias is underlain by the Late Triassic Penarth Group,[3] and overlain by the Inferior Oolite in most of England and the Dogger Formation or Ravenscar Group in the Cleveland Basin. In some areas there is a stratigraphic hiatus, and the rocks are overlain by Cretaceous marine sediments.

There are restricted outcrops of Lias rocks on the west coast of

Skye, Raasay and Mull, the Broadford Beds Formation, Pabay Shale Formation and overlying Scalpay Sandstone Formation are assigned to the Lias Group.[4][5][6][7]

In Dutch lithostratigraphy, the name Lias has no official status, however, it is often used for the lower part of the Altena Group in the subsurface of the Netherlands and the southern North Sea.[8]

In northern Germany, the Lias Group consists of nine formations (from top to base):[9]

See also

References

Notes

  1. ISBN 978-0-444-63771-0
    .
  2. ^ Oxford English Dictionary, s.v. "lias".
  3. ^ Somerset Geological TimeLine, fossilgalore.com
  4. ^ British Geological Survey (BGS). "Geology of Britain viewer". mapapps.bgs.ac.uk.
  5. ^ "BGS Lexicon of Named Rock Units". www.bgs.ac.uk.
  6. ^ "BGS Lexicon of Named Rock Units". www.bgs.ac.uk.
  7. ^ "BGS Lexicon of Named Rock Units". www.bgs.ac.uk.
  8. ^ See for example Wong (2007)
  9. ISBN 3-00-010197-7
    (PDF: 6.57 MB)

Literature
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