| Computer Code: |
DELA |
Preferred Map Code: |
DmS |
| Status Code: |
Full |
| Age range: |
Early Triassic Epoch (TE)
— Anisian Age (TA) |
| Lithological Description: |
Sandstone and pebbly sandstone with subordinate mudstone beds. Reddish-orange and pale yellow. Planar and trough cross-bedded or massive. Common intraformational pebbles of sandstone and mudstone and extraformational quartz, up to 2.5cm. The Member is more strongly cemented than those immediately above and below, and is therefore commonly more resistant and consequentially commonly feature-forming. |
| Definition of Lower Boundary: |
Lowermost occurrence of dominantly pebbly sandstone overlying pebble-free weakly cemented sandstone of the Wilmslow Sandstone Formation. |
| Definition of Upper Boundary: |
Uppermost occurrence of pebbly sandstone under weakly cemented pebble-free sandstone of the Frodsham Soft Sandstone Member (Helsby Sandstone Formation), or under interbedded siltstone and sandstone of the Tarporley Siltstone Formation (Mercia Mudstone Group). |
| Thickness: |
40m (Helsby area); c.90m (north Wirral). |
| Geographical Limits: |
Cheshire Basin; possibly southern part of the East Irish Sea Basin. |
| Parent Unit: |
Helsby Sandstone Formation (HEY)
|
| Previous Name(s): |
Basement Beds [Obsolete Name and Code: Use WAR, HEY, BRCT, BABE, LFSB, LLW, DELA, FRM, PLT, FRFA, PFLD, DDC]
(-3812)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
Irby Hill Quarry, Irby, Wirral (Hough, 1999). |
| Type Area |
Helsby Hill, north Cheshire (Thompson, 1970a). |
| Partial Type Section |
Helsby Sandstone Quarry (Thompson, 1970a). |
| Reference Section |
Over Helsby Hill (Thompson, 1970a). |
| Reference(s): |
| Rees, J G and Wilson, A A. 1998. Geology of the country around Stoke-on-Trent. Memoir of the British Geological Survey, Sheet 123 (England and Wales). |
| 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, 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. |
| Hough, E, 1999. The geology of the north Wirral district. British Geological Survey Technical Report WA/98/66. |
| 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). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E096
|
