The BGS Lexicon of Named Rock Units — Result Details

Rora Mudstone Formation

Computer Code: RRAM Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Famennian Age (DA) — Tournaisian Stage (CT)
Lithological Description: Purple, green and greyish green mudstones. Scattered siliceous and calcareous nodules developed at some levels. A prominent 10m-thick unit of buff-weathering calcareous laminated siltstone capped by 2m of interbedded grey silty mudstones and siliceous black mudstones is present at the top of the Formation.
Definition of Lower Boundary: The lower boundary is not seen. May possibly overlie the Tavy Formation but further investigation is needed.
Definition of Upper Boundary: The upper boundary is taken at the sharp incoming of the black mudstones of the "Ararat Slate" (Teign Chert Formation) above the buff-weathering calcareous laminated siltstones capped by 2m of interbedded grey silty mudstones and siliceous black mudstones at the top of the underlying Rora Mudstone Formation.
Thickness: Uncertain, but probably not more than 200m exposed.
Geographical Limits: Liverton area (SX79 75), south Devon.
Parent Unit: Tamar Group (TAMA)
Previous Name(s): Liverton Slates (-3646)
Islington Slates (-2402)
Rora Slate (-2403)
Rora Slate Formation [Obsolete Name And Code: Use RRAM] (RSL)
Alternative Name(s): none recorded or not applicable
Partial Type Section  South Rora Down Quarry, southwest of Liverton, south Devon. 2m of green and purple mudstones with a thin bed of black siliceous mudstone is exposed in the upper part of the Formation. Neither the base nor the top of the Formation is seen. 
Bristow, C M. 1963. The geology of the area between Islington, Liverton and Bickington. Proceedings of the Ussher Society, Vol.1, 65-67. 
Selwood, E B, Edwards, R A, Simpson, S, Chesher, J A, Hamblin, R J O, Henson, M R, Riddolls, B W and Waters, R A. 1984. Geology of the countryside around Newton Abbot. Memoir of the British Geological Survey, Sheet 339 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable