The BGS Lexicon of Named Rock Units — Result Details

Newton Chert Formation [Obsolete Name And Code: Use COH]

Computer Code: NCH Preferred Map Code: NCh
Status Code: Index Level
Age range: Visean Stage (CV) — Visean Stage (CV)
Lithological Description: Black glassy chert with thin shale interbeds. Elsewhere the chert beds include thin to thick pale grey siltstone laminae. Black siliceous slaty mudstone structurally below the chert contains rare limestone lenses.
Definition of Lower Boundary: Faulted out.
Definition of Upper Boundary: Faulted out.
Thickness: c.100m exposed structural thickness.
Geographical Limits: Northern part of Plymouth (348) Sheet. Southern part of Tavistock (337) Sheet.
Parent Unit: Not Entered (?)
Previous Name(s): Newton Chert Member (-2953)
Lower Culm Measures (-77)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Sequences in fault blocks at Herod Down [SX356 646], Tor Wood [SX358 650], Crendle Down [SX342 655], Newton Ferrers [SX347 660] and Durnaford [SX334 669] 
Reference(s):
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). 
Leveridge B E, Holder, M T, Goode, A J J, Scrivener R C, Jones N S and Merriman, R J. 2002. Geology of the Plymouth and south-east Cornwall area. Memoir of the British Geological Survey, Sheet 348 (England and Wales). 
Whiteley, M J. 1983. The geology of the St Mellion outlier, Cornwall and its regional setting. Unpublished PhD thesis, University of Exeter. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E337 E348