The Garnedd-Wen Formation (also known as the Garnedd-Wen Beds) is an Ordovician lithostratigraphic formation (a sequence of rock strata) in Mid Wales. The rock of the formation is a mixture of mudstones, siltstones, fine- to coarse-grained sandstones, greywackes and conglomerates.[1] The formation extends from Dinas Mawddwy in the north-east to Tywyn in the south-west.[2]

Garnedd-Wen Formation
Stratigraphic range: Hirnantian
The upper slopes of Tarren y Gesail are primarily in the Garnedd-Wen Formation
TypeFormation
Unit ofAbercorris Group
OverliesNarrow Vein Mudstone Formation
Thickness1,000 metres (3,300 ft) to 3,000 metres (9,800 ft)
Lithology
PrimaryMudstone
OtherSandstone
Location
Coordinates52°38′07″N 3°54′26″W / 52.6354°N 3.9071°W / 52.6354; -3.9071
RegionMid Wales
CountryWales
ExtentTywyn to Dinas Mawddwy
Type section
Named forGarneddwen

Geography

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The Garnedd-Wen Formation is the upper strata of rock across a wide part of western Mid Wales. In particular, it forms the upper rock beds of the Tarren Hills on the south side of the Bala Fault, west of Talyllyn Lake.[3]

References

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  1. ^ "Garnedd-Wen Formation". BGS on-line lexicon of rock units. British Geological Survey. Retrieved 11 September 2019.
  2. ^ P. J. Brenchley (2006). The Geology of England and Wales. Geological Society of London. pp. 74–. ISBN 978-1-86239-200-7.
  3. ^ W. T. Pratt; D. G. Woodhall; Malcolm Fletcher Howells; M. J. Leng (1995). Geology of the Country Around Cadair Idris. H.M. Stationery Office. ISBN 978-0-11-884509-0.