The Mercia Mudstone Group is an early Triassic lithostratigraphic group (a sequence of rock strata) which is widespread in Britain, especially in the English Midlands—the name is derived from the ancient kingdom of Mercia which corresponds to that area. It is frequently encountered in older literature as the Keuper Marl or Keuper Marl Series.[1]
The Mercia Mudstone Group is now divided into five formations recognised and mappable across its entire outcrop and subcrop. The formations are a mix of mudstones, siltstones, sandstones and halites. Historically this sequence of rocks has been subdivided in different ways with different names in each of the basinal areas in which it is found. Increasing knowledge of the sequences and the more recent development of seamless electronic mapping by the British Geological Survey (BGS) necessitated a reappraisal of these divisions. A report published by BGS in 2008 recommended the abandonment of previous divisions and naming schemes in favour of a simpler approach which, having now been adopted, is set out below.[2]
Blue Anchor Formation
Branscombe Mudstone Formation
Arden Sandstone Formation
Sidmouth Mudstone Formation
Tarporley Siltstone Formation
Older schemes will remain in maps and literature well into the future,[3] providing a source of potential confusion. An example might be the Arden Sandstone Formation which previously enjoyed lower status as a member and also higher status as a group.
^British Geological Survey 1998–2014 (c)NERC. "BGS Lexicon of Named Rock Units - Result Details". bgs.ac.uk. Retrieved 16 March 2014.{{cite web}}: CS1 maint: numeric names: authors list (link)
^Howard, A. S., Warrington, G., Ambrose, K. and Rees, J. G. 2008. A formational framework for the Mercia Mudstone Group (Triassic) of England and Wales. British Geological Survey Research Report, RR/08/04.
^Mercia Mudstone Group at Fossilworks.org
and 26 Related for: Mercia Mudstone Group information
Schilfsandstein of Germany and various members of the United Kingdom's MerciaMudstoneGroup) are intervals of river sediments enriched with kaolinitic clay...
marl is included within the MerciaMudstoneGroup. British Geological Survey: Lexicon of Named Rock Units: MerciaMudstoneGroup (accessed 10 April 2010)...
(uppermost/youngest at top): MerciaMudstoneGroup Tarporley Siltstone Formation (siltstones, mudstones and sandstones) including Retford Member (mudstones) Sherwood Sandstone...
found in the Tarporley Siltstone Formation (MerciaMudstoneGroup) and possibly the Sherwood Sandstone Group of the United Kingdom. Cladogram based on Ezcurra...
Group is up to 900m thick and comprises red, brown and grey mudstones with beds of halite and anhydrite. It is the offshore equivalent of the Mercia Mudstone...
which "subcrop" in the east. The slightly younger mudstones and siltstones of the MerciaMudstoneGroup are found west of a line drawn roughly between Freckleton...
between Ashbourne and Derby under layers of clays and sandstones (MerciaMudstoneGroup and Sherwood Sandstones) of Permo-Triassic age. Small amounts of...
the south-east of Glenfrome Road, and Triassic mudstone and halite-stone of the MerciaMudstoneGroup to the north. The solid geology in the Mina Road...
resulted in an accumulation of windblown Loess, which now forms the MerciaMudstoneGroup. With the subsequent sinking of the East Midlands crust, these deposits...
sequences referred to the Sherwood Sandstone Group and the overlying MerciaMudstoneGroup are the thickest in England. An isolated outlier of Jurassic rocks...
Sandstone Group in the Newent Coalfield, by mudstones of the MerciaMudstoneGroup in the Oxfordshire Coalfield and either the Sherwood Sandstone or Mercia Mudstone...
and Cotham Members, grey limestones of marine origin with associated mudstones, are recognised within the Lilstock Formation, itself named from Lilstock...
Hill and Harrol Edge. The younger siltstones and mudstones are assigned to the MerciaMudstoneGroup. The sequence of sandstones is exposed in a railway...
made of Triassic sandstone capped by Keuper marl ascribed to the MerciaMudstoneGroup. Burrow Mump is also known as St Michael's Borough or Tutteyate...
Sherwood Sandstone Group are overlain by claystones and siltstones of the MerciaMudstoneGroup and limestones of the Penarth Group. A complete Jurassic...
sequence overlying Warwickshire Group strata is thus (uppermost, youngest at top): MerciaMudstoneGroup Sherwood Sandstone Group Helsby Sandstone Formation...
The following sequence is encountered within Merseyside: MerciaMudstoneGroup Sidmouth Mudstone Formation (formerly 'Keuper Marl') Tarporley Siltstone...
confused due to their similar composition. Its upper layers consist of mudstones, but most of the formation consists of reddish to yellowish sandstones...
geological features which show the Tarporley Siltstone Formation of the MerciaMudstoneGroup. Natural England citation sheet Metropolitan Borough of Wirral:...
Formation, completing the Sherwood Sandstone Group (SSG) sequence in this basin. The overlying MerciaMudstoneGroup (MMG) has the Tarporley Siltstone Formation...
Sandstone Group in the Newent Coalfield, by mudstones of the MerciaMudstoneGroup in the Oxfordshire Coalfield and either the Sherwood Sandstone or Mercia Mudstone...
of which are the mudstones of the MerciaMudstoneGroup (formerly known as the Keuper Marl), overlain in the west by more mudstones of the late Triassic...
mudstone that marks the Jurassic boundary - the primary marker at this site is the ammonite Psiloceras planorbis A slump fold in the Triassic Mercia Mudstone...
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