The BGS Lexicon of Named Rock Units — Result Details

Meadfoot Group

Computer Code: MDT Preferred Map Code: Mdt
Status Code: Full
Age range: Pragian Age (DP) — Emsian Age (DE)
Lithological Description: The lower part of the Group is comprised of coarsening-up cycles of laminated silty sandstone to thickly bedded sandstone with local coarsely bioclastic limestone (Lower and Upper Long Sands Sandstone Members of the Bovisand Formation). Above this, the remainder of the Bovisand Formation is characterised by grey slaty mudstone and siltstone with lenses, beds and packets of cross-laminated sandstone. The overlying Staddon Formation is comprised of dark grey and grey slaty mudstone and siltstone with sandstone packets (up to 6 m thick in lower part) and thin limestone beds (mainly in the upper part).
Definition of Lower Boundary: Transitional boundary with the underlying Whitsand Bay Formation (of the Dartmouth Group). Contact is seen at Tregantle Cliffs [SX 388 526], where the uppermost strata of the Whitsand Bay Formation (of the Dartmouth Group) comprise interbedded red and green slaty mudstone with sporadic thin quartzose sandstone beds and grey slaty mudstone; this passes upwards in to the overlying Bovisand Formation (of the Meadfoot Group) which is comprised of bioturbated grey mudstone with sandstone laminae, thin beds, load casts and black phosphatic nodules. Near Oldhouse Cove [SX 367 536] the contact is expressed as an upward passage in to grey slaty mudstone with thin interbeds of grey-green siltstone and fine sandstone, with dark grey mudstone becoming predominant over 20 m.
Definition of Upper Boundary: A faulted contact, variably a steeply-dipping normal or reverse fault. The overlying Saltash Formation of the Tamar Group is juxtaposed along faulted boundaries at many localities to the west of the Tamar Esuary. The upper boundary of the Meadfoot Group in this area would commonly be identified by the juxtaposition of the Staddon Formation of the Meadfoot Group (thick to thin beds of fine to coarse-grained sandstone with tabular and trough cross-bedding) with the Saltash Formation of the overlying Tamar Group (predominate grey mudstone and siltstone sequence). At other localities, rocks of the Meadfoot Group are juxtaposed with rocks asigned to other Groups - an example is where the normal-sense Cawsand Fault, in Cawsand Bay [SX 4379 5090] juxtaposes the lithologies of the Staddon Fomation (see above) against the reddish brown breccia conglmerate and purplish pink rhyolite of the Kingsand Rhyolite Formation. In the Torquay district, the Meadfoot Group is either overlain by the Nordon Formation (grey to blue/grey with with limestone layers) or has a faulted contact with other rock types in the district.
Thickness: Up to 1700 m.
Geographical Limits: In south-west England, forming an east-west trending band across the peninsula of south Devon and Cornwall.
Parent Unit: Not Applicable (-)
Previous Name(s): Meadfoot Group [Obsolete Name and Code: Use MDT] (*558)
Meadfoot Series [Obsolete Name and Code: Use MDT] (-1688)
Meadfoot Beds (-76)
Meadfoot Grits [Obsolete Name and Code: Use MDT] (-4784)
Meadfoot Group [Obsolete Name and Code: Use MDT] (*558)
Meadfoot Beds And Staddon Grit [Obsolete Name And Code: Use MDT And STG] (MFSG)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Meadfoot Sands, Torquay. Ussher, 1933 (2nd edition). 
Reference(s):
Ussher, W A E, by Lloyd, W. 1933. The Geology of the country around Torquay. Explanation of sheet 350. Memoirs of the British Geological Survey. 
Ussher, W A E. 1907. The Geology of the country around Plymouth and Liskeard. Memoir of the Geological Survey of Great Britain, Sheet 348 (England and Wales). 
Ussher, W A E. 1890. The Devonian rocks of south Devon. Quarterly journal of the Geological Society, London. Vol.46, 487-517. 
Harwood, G M, 1976. The Staddon Grits - or the Meadfoot Beds? Proceedings of the Ussher Society, Vol.3, 333-338. 
Seago, R D and Chapman, T J, 1988. The confrontation of structural styles and the evolution of a foreland basin in central south-west England. Journal of the Geological Society of London, Vol.145, 789-800. 
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. 
Champernowne, A. 1881. Notes on a find of Homalontus in the Red Beds at Torquay. Geological Magazine, Vol.8, 487-488. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E355 E356 E350