| Computer Code: |
THUN |
Preferred Map Code: |
TsS |
| Status Code: |
Full |
| Age range: |
Early Triassic Epoch (TE)
— Anisian Age (TA) |
| Lithological Description: |
Sandstone, reddish-orange and rare pebbly sandstone, reddish-grey. Predominantly fine-grained; well-sorted with spherical to sub spherical grains. Rare laterally impersistent pebbly sandstone beds up to 3m thick in lower part. Soft sediment deformation common in pebble-free units. Less well-cemented in comparison to overlying Delamere Sandstone Member. |
| Definition of Lower Boundary: |
Taken at base of a maximum 3m thick pebbly sandstone bed (the 'Thurstaston Hard Sandstone Bed'), overlying pebble-free reddish-orange sandstone of the Wilmslow Sandstone Formation. |
| Definition of Upper Boundary: |
At boundary of weakly-cemented, pebble-free sandstone and overlying pebbly sandstone of the Delamere Sandstone Member (Helsby Sandstone Formation). |
| Thickness: |
58m in Hoylake Water Works No.2 Borehole (SJ28NW/5). Wirral. 62m in Hoylake Water Works No.1 Borehole (SJ28NW/4). Wirral. |
| Geographical Limits: |
Cheshire Basin; possibly southern part of the East Irish Sea Basin. |
| Parent Unit: |
Helsby Sandstone Formation (HEY)
|
| Previous Name(s): |
Upper Mottled Sandstone [Obsolete Name And Code: See WLSF And WRS]
(UMS)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
A450, Thurstaston road cutting. 300-600 m north of junction with Station Road and Thurstaston Road (Thompson, 1970a). |
| Reference Section |
Hoylake Water Works No.2 Borehole (SJ28NW/5). 9.15-67.07 m from surface (Hough, 1999). |
| Reference Section |
Hoylake Water Works No.1 Borehole (SJ28NW/4). 3.04-65.54 m from surface (Hough, 1999). |
| Reference(s): |
| 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. |
| 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. |
| Earp, J R and Taylor, B J, 1986. Geology of the country around Chester and Winsford. Memoir of the British Geological Survey, Sheet 109 (England and Wales). |
| 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. |
| Hough, E, 1999. The geology of the north Wirral district. British Geological Survey Technical Report WA/98/66. |
| Ambrose, K, Hough, E, Smith, N J P, and Warrington, G. 2014. Lithostratigraphy of the Sherwood Sandstone Group of England, Wales and south-west Scotland. British Geological Survey Research Report RR/14/01. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E096
|
