The BGS Lexicon of Named Rock Units — Result Details
Malpas Sandstone Member
| Computer Code: | MASS | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Anisian Age (TA) — Anisian Age (TA) | ||
| Lithological Description: | Sandstone, red, fine- to medium-grained, with abundant rounded "millet seed" grains. Sandstone is cross-stratified and weakly cemented. Subordinate beds also occur of sandstone and coarse siltstone, brown, fine-grained, micaceous, laminated; these resemble sandstones of the parent Tarporley Siltstone Formation. | ||
| Definition of Lower Boundary: | Conformable, within a gradational, interdigitating transition from the interbedded brown sandstone, siltstone and mudstone of the underlying Tarporley Siltstone Formation (undivided) to the red sandstone with abundant millet seed grains of the Malpas Sandstone Member. | ||
| Definition of Upper Boundary: | Conformable, with an abrupt transition to interbedded red mudstone and pink micacesous siltstone of the Bollin Mudstone Member of the Sidmouth Mudstone Formation. | ||
| Thickness: | Up to 180 m at outcrop in the Malpas area. | ||
| Geographical Limits: | A locally developed sandstone-rich facies of the Tarporley Siltstone Formation, occurring in the upper part of that formation. The member occurs at outcrop at Malpas, west Cheshire; it is also proved at depth to the east in the Wilkesley Borehole (SJ64SW/7) [SJ 6286 4144], Cheshire (Stephens, 1961). | ||
| Parent Unit: | Tarporley Siltstone Formation (TPSF) | ||
| Previous Name(s): | Malpas Sandstone [Obsolete Name and Code: Use MASS]
(-4181)
Upper Keuper Sandstone [Obsolete Name and Code: Use MASS, AS] (-1683) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | Town of Malpas, Cheshire, which is largely constructed on an outcrop of this unit. Poole and Whiteman (1966). | ||
| Reference(s): | |||
| Howard, A S, Warrington, G, Ambrose, K, and Rees, J G. 2008. A formational framework for the Mercia Mudstone Group (Triassic) of England and Wales. British Geological Survey Research Report, RR/08/04. | |||
| Poole, E G, and Whiteman, A J. 1966. Geology of the country around Nantwich and Whitchurch. Memoir of the Geological Survey of Great Britain, Sheet 122 (England and Wales). | |||
| Pugh, W. 1960. Triassic salt: discoveries in the Cheshire-Shropshire Basin. Nature, London. Vol.187, 278-279. | |||
| Stephens, J V. 1961. North Western district. 37-39 in Geological Survey of Great Britain. Summary of Progress for 1960. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| none recorded or not applicable | |||