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Contents

   



(Top)
 


1 Subdivisions  





2 See also  





3 References  



3.1  Notes  





3.2  Literature  
















Lias Group






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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

BunterorBuntsandstein

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 GrouporLias is a lithostratigraphic unit (a sequence of 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.[2] In the past, geologists used Lias not only for the sequence of rock layers, but also for the timespan during which they were formed. It was thus an alternative name for the Early Jurassic epoch of the geologic timescale. It is now more specifically known that the Lias is RhaetiantoToarcian 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[edit]

In southern England, the Lias Group is often divided into Lower, Middle and Upper subgroups. In Southern England the Lias is divided into the following formations (from top to base):

In the East Midlands Shelf the Lias is divided into the following formations (from top to base):

In the Cleveland Basin in Yorkshire the Lias is divided into the following formations (from top to base):

InSouth 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 FormationorRavenscar 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 Scotland where, in the Sea of the Hebrides depositional basin on 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]

InDutch 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[edit]

References[edit]

Notes[edit]

  1. ^ 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.
  • ^ Oxford English Dictionary, s.v. "lias".
  • ^ Somerset Geological TimeLine, fossilgalore.com
  • ^ British Geological Survey (BGS). "Geology of Britain viewer". mapapps.bgs.ac.uk.
  • ^ "BGS Lexicon of Named Rock Units". www.bgs.ac.uk.
  • ^ "BGS Lexicon of Named Rock Units". www.bgs.ac.uk.
  • ^ "BGS Lexicon of Named Rock Units". www.bgs.ac.uk.
  • ^ See for example Wong (2007)
  • ^ Deutsche Stratigraphische Kommission (eds.): Stratigraphische Tabelle von Deutschland 2002 Archived 2008-10-25 at the Wayback Machine (stratigraphic tables of the German commission on stratigraphy), Potsdam 2002, ISBN 3-00-010197-7 (PDF: 6.57 MB)
  • Literature[edit]


    Retrieved from "https://en.wikipedia.org/w/index.php?title=Lias_Group&oldid=1108320658"

    Categories: 
    Early Jurassic Europe
    Jurassic geology
    Jurassic England
    Jurassic Germany
    Lithostratigraphy of England
    Lithostratigraphy of Germany
    Jurassic System of Europe
    Hidden categories: 
    Webarchive template wayback links
    Articles with short description
    Short description matches Wikidata
     



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