The BGS Lexicon of Named Rock Units — Result Details

Harrath Tuff Member

Computer Code: HHT Preferred Map Code: HhT
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Rhyolitic tuff - densely welded, foliated, white-weathered.
Definition of Lower Boundary: Base of rhyolitic tuff that rests on an erosion surface cut in dacitic lapilli-tuff of the Waberthwaite Formation; basaltic andesite intrusions may intervene.
Definition of Upper Boundary: Top of rhyolitic tuff - probably an erosion surface at contact with overlying dacitic lapilli-tuff of the Waberthwaite Formation.
Thickness: 60 to c.250m
Geographical Limits: Between Harrath (hill) and Corner Croft, north of The Hill, near Millom, Cumbria.
Parent Unit: Waberthwaite Tuff Formation (WB)
Previous Name(s): Harrath Tuffs And Lavas (-3886)
Rhyolitic Series (-4093)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Between Harrath (hill) and Corner Croft north of The Hill near Millom, Cumbria. 
Reference(s):
Johnson, E W, Soper, N J, Burgess, I C, Ball, D F, Beddoe-Stephens, B, Carruthers, R M, Fortey, N J, Hirons, S, Merritt, J W, Millward, D, Roberts, B, Walker, A B and Young, B. 2001. Geology of the country around Ulverston. Memoir of the British Geological Survey, England and Wales, Sheet 48. 
Green, J F N, 1913. The older Palaeozoic succession of the Dudden Estuary. London, 23pp. 
Mathieson, N A, 1986 Geology, structure and geochemistry of the Ordovician volcanic succession in south west Cumbria. Unpublished Ph.D. thesis, University of Sheffield. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E048