| Computer Code: |
TWM |
Preferred Map Code: |
TwM |
| Status Code: |
Full |
| Age range: |
Norian Age (TN)
— Norian Age (TN) |
| Lithological Description: |
[Obsolete: use BCMU]
Mainly structureless red-brown silty mudstones and siltstones with common gypsum/anhydrite; minor green mudstones and siltstones and laminated beds. |
| Definition of Lower Boundary: |
Placed at the base of red, structureless mudstones where they rest on green beds of the underlying Arden Sandstone Formation; boundary is sharp or a rapid transition. |
| Definition of Upper Boundary: |
Placed at top of red mudstones where they are overlain by the green beds of the Blue Anchor Formation. Boundary is sharp or rapidly transitional. |
| Thickness: |
169.01m in type section; 15-20m in eastern Warwickshire. |
| Geographical Limits: |
Worcester Basin to Warwickshire. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
Twyning Formation [Obsolete Name and Code: Use TWM]
(-2507)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Reference Section |
ICI Saleway Borehole, near Droitwich, Hereford and Worcester, from 35.66m to 214.27m depth |
| Type Section |
BGS Twyning Borehole, 560m at 040 from Twyning Church, Twyning, near Tewkesbury, Gloucestershire; from 141.5-310.51m depth. (Barclay, W J and others. 1997; Worssam and others, 1989). |
| Reference Section |
BGS Stowell Park Borehole, near Northleach, Gloucestershire, from 2112' 9" to 2512' 1" depth. (Green and Melville, 1956). |
| Reference(s): |
| Worssam, B C, Ellison, R A and Moorlock, B S P. 1989. Geology of the country around Tewkesbury. Memoir of the British Geological Survey, Sheet 216 (England and Wales). |
| Green, G W and Melville, R V. 1956. The stratigraphy of the Stowell Park Borehole (1949-1951). Bulletin of the Geological Survey of Great Britain, No.11, p.1-66. |
| Barclay, W J, Ambrose K, Chadwick, R A, and Pharaoh, T C. 1997. Geology of the country around Worcester. Memoir of the British Geological Survey, Sheet 199 (England and Wales). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E199
|
