The BGS Lexicon of Named Rock Units — Result Details

Oreton Limestone Formation

Computer Code: ORTL Preferred Map Code: Ort
Status Code: Full
Age range: Tournaisian Stage (CT) — Tournaisian Stage (CT)
Lithological Description: The lower part is dominated by hard grey crystalline Limestones, crinoidal limestones and ooidal limestones. The upper part of the succession comprises mudstone with thin nodular limestones.
Definition of Lower Boundary: The base of the lowermost ooidal or crinoidal limestone-dominated sequence of the Oreton Limestone Formation, underlain conformably by calcareous mudstone and impure limestone of the Avon group in the southern crop near Cleehill [SO 571 750]. This boundary has not been mapped on the Ludlow (181) Sheet. In the north crop near Oreton [SO 665 806]] , the Oreton Likestone Formation is shown resting directly upon conglomeratic sandstone, interpreted to be the basal unit of the Avon Group.
Definition of Upper Boundary: Mudstone and nodular limestones of the Oreton Limestone Formation are overlain with an angular unconformity by quartzitic sandstone of the Cornbrook Sandstone Formation.
Thickness: About 45 m thick in the northern outcrop between Oreton and Farlow [SO 646 803], and 20 m thick in the southern crop at Clee Hill [SO 571 750].
Geographical Limits: Clee Hills Outlier, between Cleehill [SO 571 750] and Oreton [SO 665 806].
Parent Unit: Pembroke Limestone Group (PEMB)
Previous Name(s): Oreton Limestone (-2354)
Main Limestone (ML)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Two quarries at Oreton, about 250 m NE of the New Inn. The western quarry [SO 6519 8068] comprises 11.5 m ofmainly ooidal limestone; the eastern one [SO 6518 8062] comprises 10-11 m of ooidal limestone. Neither base nor the top of the formation are seen. Greig et al., 1968 
Reference(s):
Greig D C, Wright, J E, Hains, B A and Mitchell, G H. 1968. Geology of the country around Church Stretton, Craven Arms, Wenlock Edge and Brown Clee. Memoir of the Geological Survey, Sheet 166 (England and Wales). (London: H.M.S.O.). 379pp. 
Turner, N and Spinner, E. 1988. A palynological study of Lower Carboniferous strata (Dinantian), from Titterstone Clee, Shropshire, England. Pollen et Spores, Vol. 30, 429-459. 
Dixon, E E L. 1917. The geology of the Titterstone Clee Coal Field. Transactions of the Royal Society of Edinburgh, Vol.51, 1064-1071. 
George, T N. 1956. The Namurian Usk Anticline, Proceedings of the Geologists' Association, Vol.66, 297-316. 
George, T N, Johnson, G A L, Mitchell, M, Prentice, J E, Ramsbottam, W H C, Sevastopulo, G D and Wilson, R B. 1976. A correlation of the Dinantian rocks of the British Isles. Special Report of the Geological Society of London, No 7. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E181 E166