The BGS Lexicon of Named Rock Units — Result Details

Wentnor Group

Computer Code: YW Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Ediacaran Period (AD) — Ediacaran Period (AD)
Lithological Description: Massive, purple and green, coarse-grained volcaniclastic sandstones with subordinate mudstones and siltstones, and beds of conglomerate. The suffix 'Western Longmynd' is superfluous and it is also preferable not to ascribe a geographical extent to this division, given the uncertainties over its relationship to the Stretton Group that underlies it; i.e. whether the boundary is unconmformable or not . It is possible that the term will become obsolete in the future, depending on the degree of acceptance of the stratigraphy proposed by Pauley (1990). However the term 'Wentnor Group' is currently used and understood widely, and it is suggested that it is retained as an informal name.
Definition of Lower Boundary: Taken at the change from purple and green shaly mudstones and sandstones of the Portway Formation of the Stretton Group, into the more massive coarse purplish sandstones of the Bayston Formation of the Wentnor Group. It has been argued that the boundary is an unconformity by Greig et al. (1968), although there is no obvious angular discordance at this level. However, Pauley (1990) considered that no such unconformity exists, and the succession was one of prograding alluvial facies.
Definition of Upper Boundary: Not seen
Thickness: 1800 m - 3600 m thick.
Geographical Limits: Welsh Borderlands, Shropshire, Longmynd.
Parent Unit: Longmyndian Supergroup (LO)
Previous Name(s): Wentnor Series (-2547)
Alternative Name(s): none recorded or not applicable
Type Area  The northern part of the Longmynd. Greig D C, et al, 1968. 
Greig D C, Wright, J E, Hains, B A and Mitchell, G H. 1968. Geology of the country around Church Stretton, Craven Arms, Wenlock Edge and Brown Clee. Memoir of the Geological Survey, Sheet 166 (England and Wales). (London: H.M.S.O.). 379pp. 
Lapworth C and Watts W W. 1910. Shropshire. 739-769 in Geology in the field; the Jubilee Volume of the Geologists' Association (1858-1908). Monckton H W and Herries R S (editors). (London: Edward Stanford). 
Pauley J C. 1990. The Longmyndian Supergroup and related Precambrian sediments of England and Wales. 5-27 in Avalonian and Cadomain geology of the North Atlantic. Strachan R A and Taylor G K (editors). (Glasgow: Blackie). 
Pauley J C. 1990. Sedimentology, structural evolution and tectonic setting of the Late Precambrian Longmyndian Supergroup of the Welsh Borderland, UK. 341-351 in the Cadomian Orogeny. D'Lemos R S, Strachan R A and Topley C G (editors). Geological Society of London Special Publication No. 51. 
Pauley J C. 1991. A revision of the stratigraphy of the Longmyndian Supergroup, Welsh Borderland, and of its relationship to the Uriconian volcanic complex. Geological Journal, Vol. 26, 167-183. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E197 E180 E166