The BGS Lexicon of Named Rock Units — Result Details

Charnian Supergroup

Computer Code: CHA Preferred Map Code: CHA
Status Code: Full
Age range: Ediacaran Period (AD) — Ediacaran Period (AD)
Lithological Description: Fine-, medium- and coarse-grained volcaniclastic sedimentary rocks with locally abundant tuffs and volcanic breccias. Intruded in Charnwood Forest by massive to brecciated andesites and dacites of the Whitwick Volcanic Complex and the Bardon Hill Volcanic Complex. The rocks are fractured, cleaved and show very low-grade metamorphism (Nuneaton) or upper greenschist metamorphism (Charnwood Forest).
Definition of Lower Boundary: Not seen.
Definition of Upper Boundary: Weathered and eroded, fractured or cleaved volcaniclastic rocks are overlain unconformably by strata ranging from earliest Palaeozoic to Mesozoic age.
Thickness: 3000m minimum.
Geographical Limits: Extends from Blackbrook (SK 452 185) south-eastwards to the Bradgate area of Charnwood Forest (SP 543 107), and thence beneath younger rocks south-westward to Nuneaton (SP 340 937). Present beneath younger strata westwards to Malvern 'line'.
Parent Unit: Not Applicable (-)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Usually Called 'Ancient Volcanic Rocks'.
Reference Section  The upper northern level of Boons Quarry, 50m south of Grange Farm, near Nuneaton (SSSI). Shows erosional unconformity with Lower Cambrian Hartshill Sandstone Formation. 
Type Area  The area of Leicestershire extending from Blackbrook south-eastwards to the Bradgate area. 
Moseley, J and Ford, T D, 1985. A stratigraphic revision of the Late Precambrian rocks of Charnwood Forest, Leicestershire. Mercian Geologist, Vol.10(I), 1-18. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E169 E141 E155