Mercia Mudstone Group
early Triassic lithostratigraphic group
The Mercia Mudstone Group is a middle to late 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.
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.
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, 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.
Distribution
The group crops out widely across England, representing deposition within numerous Triassic basins, some of which are physically connected at depth.
“Mercia Mudstone Group” enters the record as early Triassic lithostratigraphic group. Crown Archives preserves that source wording while asking what Mercia, Mudstone and Group can confirm, complicate or overturn.
Why this record matters
“Mercia Mudstone Group” is worth following because a concise public description often conceals a longer documentary argument. Here, Mercia, Mudstone and Group provides the most credible route into that argument.
Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Feb 3, 2026. The linked authority identifier is Q6818480. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2008.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Mercia Mudstone Group”, its source revision and the description used here.
- Expand the search: follow Mercia Mudstone Group primary sources, Mercia Mudstone Group archive and Mercia research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Mercia Mudstone Group”?
- What terminology or title could unlock a more precise catalogue search?
- Which institution is responsible for the underlying evidence?
Search terms from this dossier
This entry incorporates text from “Mercia Mudstone Group” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.