The BGS Lexicon of Named Rock Units — Result Details
Dent Group
| Computer Code: | DNT | Preferred Map Code: | DNT |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Caradoc Series (O4) — Ashgill Series (OA) | ||
| Lithological Description: | The group comprises a varied assemblage of marine clastic rocks, calcareous siltstone and limestone, and includes a number of volcanic units. The group is wholly divided into formations, but many are thin and so, on many of the Geological Survey maps, the group is depicted undivided, or partially divided. Caradoc and Ashgill. | ||
| Definition of Lower Boundary: | The base of the Dent Group is diachronous across the unconformity on the underlying Caradoc volcanic rocks (Brenchley and Rawson, 2006, fig. 5.15). | ||
| Definition of Upper Boundary: | At the top of the group an abrupt transition into distinctive mudstone of the overlying Stockdale Group is seen at the base of the Spengill Mudstone Member of the Skelgill Mudstone Formation. | ||
| Thickness: | The mudstone-dominated successions in the Cross Fell, and Cautley and Dent inliers are up to 450 and 370 m thick respectively, whereas the mainly carbonate part of the succession in the Lake District varies from 20 to about 120 m (Burgess and Holliday, 1979; Millward et al., 2000). However, thickness in the Lake District is inflated locally by the inclusion of thick basal units of conglomerate and sandstone that reach 580 m in the Ulverston area and 685 m in the Kentmere to Longsleddale area, though the latter thickness also includes up to 180 m of extrusive volcanic rocks (Lawrence et al., 1986; Johnson et al., 2001). | ||
| Geographical Limits: | Components of the Dent Group occur in the northern and southern Lake District, and in the Furness, Cross Fell, Dent and Cautley, and Craven inliers. The type area is defined as the Cautley and Dent inliers [SD 700 905 to SD 698 900] (Ingham, 1966; Rickards and Woodcock, 2005). | ||
| Parent Unit: | Windermere Supergroup (WIN) | ||
| Previous Name(s): | Coniston Limestone Series [Obsolete Name and Code: Use DNT]
(-4563)
Coniston Limestone Formation [Obsolete Name and Code: Use DNT] (-4003) Coniston Limestone [Obsolete Name and Code: Use DNT] (-2107) Coniston Limestone Group [Obsolete Name and Code: Use DNT] (COL) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | Cautley and Dent inliers. | ||
| 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. | |||
| Brenchley, P J, and Rawson, P F (editors). 2006. The Geology of England and Wales. Second edition. (London: The Geological Society.) | |||
| Burgess, I C, and Holliday, D W. 1979. Geology of the country around Brough-under-Stainmore. Memoir for 1:50 000 geological sheet 31 and parts of sheets 25 and 30. Geological Survey of Great Britain (England and Wales). (London: HMSO.) 131 pp. | |||
| Ingham, J K, 1966. The Ordovician rocks in the Cautley and Dent districts of Westmorland and Yorkshire. Proceedings of the Yorkshire Geological Society, Vol.35, 455-505. | |||
| Johnson, E W, Soper, N J, Burgess, I C, Ball, D F, Beddoe-Stephens, B, Carruthers, R M, Fortey, N J, Hirons, S, Merritt, J W, Millward, D, Roberts, B, Walker, A B and Young, B. 2001. Geology of the country around Ulverston. Memoir of the British Geological Survey, England and Wales, Sheet 48. | |||
| 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. | |||
| Lawrence, D J D, Webb, B C, Young, B and White, D E. 1986. The geology of the Late Ordovician and Silurian rocks (Windermere Group) in the area around Kentmere and Crook. Includes map, 1:25,000 series, Parts of Sheets NY40 and SD49 Kentmere and Crook, Solid and Drift Geology. Report of the British Geological Survey, 18/5. | |||
| Marr, J E, 1892. The Coniston Limestone Series. Geological Magazine, Vol.(3) 9, 97-110. | |||
| McNamara, K J. 1979. The age, stratigraphy and genesis of the Coniston Limestone Group in the southern Lake District. Geological Journal, 14, 41-69. | |||
| 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. | |||
| 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 Ashgillian succession in the tract of land to the west of Coniston Lake. Quarterly Journal of the Geological Society of London 71, 189-204. | |||
| Millward, D et al., 2000. The Eycott Volcanic Group, an Ordovician continental margin andesite suite in the English Lake District. Proceedings of the Yorkshire Geological Society, Vol.53, 81-96. | |||
| 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. | |||
| Aveline, W T, and Hughes, T M. 1888. Geology of the country around Kendal, Sedburgh, Bowness and Tebay. Memoir Geological Survey of Great Britain. | |||
| 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. 1846a. The geology of the Lake District. in Scenery of the Lakes. Hudson J (editor). (Kendal: J Hudson.) | |||
| Moseley F. 1984. Lower Palaeozoic lithostratigraphical classification in the English Lake District. Geological Journal, Vol. 19, p. 239-247. | |||
| 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.) | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E038 E048 E039 | |||