The BGS Lexicon of Named Rock Units — Result Details

Gwespyr Sandstone

Computer Code: GS Preferred Map Code: notEntered
Status Code: Full
Age range: Yeadonian Substage (CY) — Langsettian Substage (CA)
Lithological Description: Fine-grained, feldspathic and micaceous sandstones, cross-stratified on a variety of scales, with conglomerate-lined scours and intercalated siltstone and mudstone beds. Intertongues with Craven Group mudstones in its lower part and Pennine Lower Coal Measures Formation in its upper part. The Gwespyr Sandstone records the entry and southwards advance of a northerly derived "Millstone Grit" deltaic facies into the North Wales area.
Definition of Lower Boundary: Entry of feldspathic sandstones above the Cancelloceras cancellatum Marine Band in north Flintshire and the Cancelloceras cumbriense Marine Band in south Flintshire and the Wrexham area.
Definition of Upper Boundary: Base of thin sequence of mudstones and seatearths immediately underlying the Llwyneinion Half Yard Coal.
Thickness: To 260m
Geographical Limits: Between Point of Air [SJ1080] and the River Dee south of Wrexham [SJ2742].
Parent Unit: Millstone Grit Group [See Also MIGR] (MG)
Previous Name(s): Halkyn Formation [Obsolete Name And Code: See Revision Data] (HAF)
Gwespyr Sandstone Formation (-2834)
Aqueduct Grit [Obsolete Name And Code: See GS] (AQG)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Gwespyr Quarries, 2.5km SSW of Point of Air. Strahan, 1885 
Reference(s):
Strahan, A, 1885. The geology of the coasts adjoining Rhyl, Abergele and Colwyn. With notes by R H Tiddeman. Memoir of the Geological Survey of Great Britain, Quarter-sheet 79NW. (England and Wales). 
Jones, R C B and Lloyd, W. 1942. The stratigraphy of the Millstone Grit of Flintshire. Journal of the Manchester Geological Association, Vol.13, 78-99. 
Davies, J R, Wilson, D and Williamson, I T. 2004. Geology of the country around Flint. Memoir for 1:50 000 Geological Sheet 108. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E096