The BGS Lexicon of Named Rock Units — Result Details

Eyam Limestone Formation

Computer Code: EYL Preferred Map Code: notEntered
Status Code: Full
Age range: Brigantian Substage (CX) — Brigantian Substage (CX)
Lithological Description: A thinly bedded, dark grey, cherty, bioclastic limestone with fossiliferous beds of brachiopods, corals and crinoids and a few dark mudstone intercalations, which is overlain by massive pale reef limestone in the south. The reef facies occur at the base in the central and southern parts, and in the upper part in the north, and is typically a core of massive biomicrite with a distinctive brachiopod fauna, passing laterally and downward into well-bedded, coarsely crinoidal biomicrites and biosparites.
Definition of Lower Boundary: Dark grey to grey brown basal limestone, resting upon clay or mudstone partings of the Eyam Limestone Formation, on a potholed surface above pale to medium grey limestone of the Monsal Dale Limestone Formation. Around Ashford-in-the-Water [SK 19 69], where both formations are dark grey, the boundary is taken at the top of the laminated beds of the Monsal Dale Limestone Formation.
Definition of Upper Boundary: A gradational top, marked by a transition from dark grey, bioclastic limestone or pale grey massive reef limestone of the Eyam Limestone, to dark grey, calcareous mudstone of the Widmerpool Formation.
Thickness: At Eyam Dale, 54 m thick including 30 m of reef facies; at Wardlow Mires No 2 borehole, it is 9.18 m, and contains no reef facies.
Geographical Limits: The Peak District of the East Midlands.
Parent Unit: Peak Limestone Group (PKLM)
Previous Name(s): Cawdor Group [Obsolete Name And Code: See Revision Data] (CW)
Cawdor Limestone [Obsolete Name And Code: Use EYL] (CWDL)
Eyam Limestones Formation (-4036)
Eyam Group [Obsolete Name And Code: See EYL] (EMGP)
Ashford Beds (-900)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Eyam Dale, shows 19.51m of strata, starting about 3.05m above the base of the Formation. 
Reference Section  Wardlow Mires No 2 Borehole, SK17NE/10, proved entire thickness at 9.18m, upper boundary with Widmerpool Formation and lower boundary with Monsal Dale Limestone Formation. 
Reference Section  Furness Quarry, Middleton Dale, displays basal 4.65m of formation, with a clay bed up to 0.38 m at the base resting above the Monsal Dale Limestone Formation. 
Reference Section  Stoney Middleton, shows reef facies passing down into bedded unit 10.9m thick, resting upon the Monsal Dale Limestone Formation. 
Reference(s):
Shirley, J, and Horsfield, E L. 1945. The structure and ore deposits of the Carboniferous Limestone of the Eyam district, Derbyshire. Quarterly Journal of the Geological Society, London, Vol. 100, 289-310. 
Aitkenhead, N and Chisholm, J I. 1982. A standard nomenclature for the Dinantian formations of the Peak District of Derbshire and Staffordshire. Report of the Institute of Geological Sciences, No.82/8. 
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. 
Stevenson, I P and Gaunt, G D, 1971. Geology of the country around Chapel-en-le-Frith. Memoir of the Geological Survey of Great Britain, England and Wales, Sheet 99. 
Aitkenhead, N, Chisholm, J I and Stevenson, I P. 1985. Geology of the country around Buxton, Leek and Bakewell. Memoir of the British Geological Survey, England and Wales Sheet 111. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E099 E112 E125 E111