| Computer Code: |
GRGT |
Preferred Map Code: |
GtG |
| Status Code: |
Index Level |
| Age range: |
Marsdenian Substage (CZ)
— Marsdenian Substage (CZ) |
| Lithological Description: |
Pale brown, medium- to coarse-grained cross-bedded sandstone with ganisters and mudstone interbeds. |
| Definition of Lower Boundary: |
Lower boundary is taken where the Greta Grit overlies gradationally the dark grey fissile mudstones and micaceous laminated siltstones with the Bilinguites gracilis Marine Band. |
| Definition of Upper Boundary: |
The upper boundary is taken where the Greta Grit is overlain sharply by mudstones with Bilinguites bilinguis (see Settle Memoir). In the type section, the overlying beds contain the Gastrioceras cancellatum Marine Band (Ford, 1954). |
| Thickness: |
Varies from 26m (in River Greta section) to 88.7m (in Seat Hall Borehole) (SD66NE/2). |
| Geographical Limits: |
Craven Basin, northwest England. |
| Parent Unit: |
Marsden Formation (MARSD)
|
| Previous Name(s): |
Greta Grits Formation [Obsolete Name and Code: Use GRGT]
(-2216)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
River Greta section 1.5km west of Burton-in-Lonsdale. |
| Reference(s): |
| Arthurton, R S, Johnson, E W, and Mundy, D J C. 1988. Geology of the country around Settle. Memoir of the British Geological Survey, Sheet 60 (England and Wales). |
| Moseley, F, 1954. The Namurian of the Lancaster Fells. Quarterly Journal of the Geological Society of London, Vol.109, 423-454. |
| Ford, T D, 1954. The Upper Carboniferous rocks of the Ingleton Coalfield. Quarterly Journal of the Geological Society of London. Vol.110, 231-265. |
| Brandon, A, Aitkenhead, N, Crofts, R G, Ellison, R A, Evans, D J, and Riley, N J. 1998. Geology of the country around Lancaster. Memoir of the British Geological Survey, Sheet 59 (England and Wales). |
| Waters, C N, Waters, R A, Barclay, W J, and Davies, J R. 2009. Lithostratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/09/01. 184pp. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E059
E060
|
