The BGS Lexicon of Named Rock Units — Result Details

Portway Formation

Computer Code: PWG Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Ediacaran Period (AD) — Ediacaran Period (AD)
Lithological Description: Purple and greenish grey shaly mudstones and siltstones with sandstone bands, sandstones are locally massive particularly near the base.
Definition of Lower Boundary: Drawn at the base of the Huckster Conglomerate where pebble horizons with coarse sandstone rest conformably upon purple mudstone, siltstones and sandstones of the Lightspout Formation.
Definition of Upper Boundary: Drawn at the conformable upward passage of purple and green shaly siltstones and sandstones of the Portway Group into more massive coarse-grained purple and grey sandstones of the Bayston-Oakswood Formation.
Thickness: Averages 625m
Geographical Limits: The Port Way on the Longmynd, west of Church Stretton, Shropshire.
Parent Unit: Stretton Group (YST)
Previous Name(s): Portway Formation [Obsolete Code: Use PWG] (YSP)
Portway Group (-1781)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The Port Way on the Longmynd, west of Church Stretton, Shropshire. 
Reference(s):
Bright, J E, 1968. The geology of the Church Stretton area. Explanation of 1:25,000 geological sheet SO49. British Geological Survey. 
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). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable