The BGS Lexicon of Named Rock Units — Result Details

Frodsham Sandstone Member

Computer Code: FRM Preferred Map Code: FsS
Status Code: Full
Age range: Early Triassic Epoch (TE) — Anisian Age (TA)
Lithological Description: Sandstone, reddish-orange, predominantly fine-grained; well-sorted with spherical to subspherical-grains; large-scale dune bedding common; characrterised by presence of 'dome-shaped dune' structures. Weakly cemented in comparison to underlying Delamere Pebbly Sandstone Member.
Definition of Lower Boundary: Lowermost occurrence of non-pebbly weakly-cemented sandstone, with characteristic 'dome-shaped dune' structures on the dominantly pebbly sandstone of the underlying Delamere Pebbly Sandstone Member.
Definition of Upper Boundary: Uppermost occurrence of weakly-cemented non-pebbly sandstone with characteristic dome-shaped dune structures, under interbedded siltstone and subordinate sandstone of the Tarporley Siltstone Formation (Mercia Mudstone Group).
Thickness: 55m in the Marston region, North Cheshire. 30.14m at Ford Pumping Station (SJ28NE/3), Wirral. 21.1m in the Heron Road Borehole (SJ28NW/22), Wirral.
Geographical Limits: Cheshire Basin; possibly also the southern part of the East Irish Sea Basin.
Parent Unit: Helsby Sandstone Formation (HEY)
Previous Name(s): Basement Beds (-3812)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Railway cutting, north-east from Frodsham Railway Station, Cheshire. Thompson, D B, 1970a; Thompson, D B, 1969. 
Type Area  Ford Pumping Station (SJ28NE/3), 157.31 - 187.45m below surface. Hough, E, 1999. 
Reference Section  Heron Road Borehole, Saughall Massie, Wirral. 117.4-138.5m from surface. Hough, E, 1999. 
Reference(s):
Thompson, D B, 1970B. Sedimentation of the Triassic (Scythian) Red Pebbly Sandstones in the Cheshire Basin and its margins. Geological Journal 7, Pt.1, 183-216. 
Wedd, C B, Smith, B, Simmons, W C and Wray, D A, 1923. The Geology of Liverpool, with Wirral and part of the Flinthsire Coalfield. Memoir of the Geological Survey of Great Britain, Sheet 96 (England and Wales). 
Rice, R C, 1939. The Trias of north-west Wirral. Proceedings of the Liverpool Geological Society 17, 349-370. 
Thompson, D B, 1970. The stratigraphy of the so-called Keuper Sandstone Formation (Scythian-?Anisian) in the Permo-Triassic Cheshire Basin. Quarterly Journal of the Geological Society of London, Vol.126, p.151-181. 
Thompson, D B, 1969. Dome-shaped Aeolian dunes in the Frodsham Member of the so-called 'Keuper' Sandstone Formation, (Scythian ?Anisian-Triassic) at Frodsham, Cheshire, England. Sedimentary Geology 3, 263-289. 
Hough, E, 1999. The geology of the north Wirral district. British Geological Survey Technical Report WA/98/66. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E096