The BGS Lexicon of Named Rock Units — Result Details
Bealsmill Formation
| Computer Code: | BEAL | Preferred Map Code: | notEntered |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Namurian Stage (CN) — Namurian Stage (CN) | ||
| Lithological Description: | Thin- to thick-bedded commonly coarse and feldspathic sandstones interbedded with siltstones and dark grey mudstones. Scattered beds of ill-sorted pebble to cobble conglomerate up to 2 m thick contain clasts including chert, lava and limestone as well as derived Dinantian and ?Namurian fossils. Some channels are present. | ||
| Definition of Lower Boundary: | The depositional lower boundary is not seen as the base is always faulted. The lower boundary is thought to post-date the D1 deformation phase, with the formation resting unconformably on Dinantian sequences. | ||
| Definition of Upper Boundary: | The depositional upper boundary is not seen but probably tectonic. | ||
| Thickness: | Unknown. Minimum thickness 120 m. | ||
| Geographical Limits: | Mapped from Altarnun [SX 22 81], east Cornwall to northwest Dartmoor [SX 49 85], but thought to extend into the southwestern part of the Okehampton area [SX 53 87], mid Devon, where it has been mapped as Crackington Formation. Formational diagnosis needs further work, as does the area where it has not been mapped. | ||
| Parent Unit: | Holsworthy Group (HOWY) | ||
| Previous Name(s): | Bealesmill Sandstone Formation [Obsolete Name and Code: Use BEAL]
(-4451)
Bealsmill Sandstone Formation [Obsolete Name and Code: Use BEAL] (-4452) Crackington Formation (CKF) Eggesford-Type Culm [Obsolete Name and Code: Use BEAL, CKF] (-47) Middle or Exeter-Type Culm [Obsolete Name and Code: Use CKF, BEAL] (-3835) Okehampton Sandstone Group [Obsolete Name and Code: Use CKF, BEAL] (-3836) |
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| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Partial Type Section | Carthamartha Crags, south of Launceston, east Cornwall. Located about 700m eastnortheast of Rezare. Only a small part of the formation is exposed with no base or top. Turner (1982); Sellwood and Thomas (1986). | ||
| Type Area | Bealsmill, Cornwall. | ||
| Reference(s): | |||
| Sellwood, E B and Thomas, J M. 1986. Variscan facies and structure in central southwest England. Journal of the Geological Society, London, Vol.153, 199-207. | |||
| Ussher, W A E. 1892. The British Culm Measures. Proceedings of the Somerset Archeological and Natural History Society, Vol.38, 111-219. | |||
| Turner, P J. 1982. Aspects of the evolution of the Hercynides in central southwest England. Unpublished PhD thesis, University of Exeter. | |||
| Dearman W R, and Butcher, N E. 1959. The geology of the Devonian and Carboniferous rocks of the northwest border of the Dartmoor Granite, Devonshire. Proceedings of the Geologists' Association, Vol. 70, 51-92. | |||
| Edmonds, E A, Wright, J E, Beer, K E, Hawkes, J R, Fenning, P J, Freshney, E C, Lovelock, P E R, McKeown, M C, Ramsbottom, W H C, and Williams, M. 1968. Geology of the country around Okehampton. Memoir of the Geological Survey of Great Britain, Sheet 324 (England and Wales). | |||
| Isaac, K P. 1985. Thrust and nappe tectonics of west Devon. Proceedings of the Geologists' Association, Vol.96, 109-127. | |||
| Ussher, W A E. 1887. The Culm of Devonshire. Geological Magazine, Vol.24, 10-17. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| none recorded or not applicable | |||