| Computer Code: |
TNTH |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Sheinwoodian Age (SS)
— Gorstian Age (SG) |
| Lithological Description: |
The succession is dominated by laminated hemipelagic mudstone and siltstone (Brathay and Wray Castle mudstone formations) that record a background accumulation of anaerobic organic mud with periodic input of turbiditic sand. Interbedded with these are a unit of calcareous siltstone (Coldwell Siltstone Formation) and units of turbiditic sandstone (Birk Riggs Sandstone Formation in the south-west Lake District, and the Austwick Sandstone Formation in the Craven inliers). The nomenclature is distinct in the Craven inliers (Arthurton et al., 1988), reflecting the subtle differences in lithofacies.
Wenlock to lower Ludlow (lowest Gorstian). |
| Definition of Lower Boundary: |
The base of the group coincides with that of the Brathay Mudstone Formation. |
| Definition of Upper Boundary: |
The upper boundary is defined by the diachronous base of the overlying Coniston Group. |
| Thickness: |
From Ulverston to Shap the thickness varies between 450 and 1110 m, whereas only 260 m are present in the Howgill Fells. |
| Geographical Limits: |
The group is represented in the Cross Fell, Cautley, Dent, and Craven inliers, though in Cross Fell only the oldest unit (Brathay Mudstone Formation) is present. |
| Parent Unit: |
Windermere Supergroup (WIN)
|
| Previous Name(s): |
Windermere Group [Obsolete Name and Code: Use TNTH, WIN]
(-2491)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Southern Lake District, Cumbria. All constituent formations have individually defined type sections. Kneller et al., 1994. |
| Reference(s): |
| Millward, D, and Stone, P. 2012. Stratigraphical framework for the Ordovician and Silurian sedimentary strata of northern England and the Isle of Man. British Geological Survey Research Report, RR/12/04. 119pp. |
| Cocks, L R M, Holland, C H and Rickards, B. 1992. A revised correlation of Silurian rocks in the British Isles. Geological Society of London Special Report. No.21, 32pp. |
| King, L M. 1992. A basin study of the early Palaeozoic Windermere Group, northwest England. Unpublished PhD thesis. University of Cambridge. |
| King, L M. 1994. Turbidite to storm transition in a migrating foreland basin: The Kendal Group (Upper Silurian), northwest England. Geological Magazine, Vol.131, 255-267. |
| Marr J E. 1892. On the Wenlock and Ludlow strata of the Lake District. Geological Magazine, Vol. 9, p 534-541. |
| Rose, W C C, and Dunham, K C. 1977. Geology and hematite deposits of South Cumbria. Economic Memoir of the Geological Survey of Great Britain, Sheet 58, part 48 (England and Wales). |
| Sedgwick, A. 1845. On the comparative classification of the fossiliferous strata of North Wales, with the corresponding deposits of Cumberland, Westmorland and Lancashire. Quarterly Journal of the Geological Society of London, Vol. 1, 442-450. |
| Sedgwick A. 1846. On the classification of the fossiliferous slates of Cumberland, Westmoreland and Lancashire. Quarterly Journal of the Geological Society of London, Vol 2, 106 - 122. |
| Marr, J E. 1916. The geology of The Lake District and the scenery as influenced by geological structure. (Cambridge: Cambridge University Press.) |
| Sedgwick, A. 1852. On the Lower Palaeozoic rocks at the base of the Carboniferous chain between Ravenstonedale and Ribblesdale. Quarterly Journal of the Geological Society of London, Vol. 8, 35-54. |
| Soper, N J. 1999. The Windermere Supergroup of 1:25 000 sheets NY50 and NY60, Southern Shap Fells and Northern Howgill Fells, Cumbria. British Geological Survey Technical Report, WA/99/35. |
| 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). |
| Kneller, B C, Scott R W, Soper N J, Johnson E W and Allen P M, 1994. Lithostratigraphy of the Windermere Supergroup, Northern England. Geological Journal, Vol. 29, 219-240. |
| Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. |
| Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) |
| Rickards R B and Woodcock, N H. 2005. Stratigraphical revision of the Windermere Supergroup (Late Ordovician-Silurian) in the southern Howgill Fells, northwest England. Proceedings of the Yorkshire Geological Society, Vol 55. 263-285. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E030
E038
E039
E048
E050
E060
|
