The BGS Lexicon of Named Rock Units — Result Details
Helvellyn Tuff Formation
| Computer Code: | HLV | Preferred Map Code: | Hlv |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Caradoc Series (O4) — Caradoc Series (O4) | ||
| Lithological Description: | Dacitic lapilli-tuff, with eutaxitic foliation at the base and with intercalations of tuff. | ||
| Definition of Lower Boundary: | Base of lapilli-tuff, or locally that of a very thin basal tuff layer, rests with slight unconformity on sandstone of the Esk Pike Formation. | ||
| Definition of Upper Boundary: | Highest lapilli-tuff or (locally) tuff is overlain unconformably by volcaniclastic rocks of the Deepdale Sandstone Formation. | ||
| Thickness: | 400m maximum known. | ||
| Geographical Limits: | Helvellyn, Fairfield, Striding Edge eastwards to Glenridding, northeastern Lake District, Cumbria. | ||
| Parent Unit: | Borrowdale Volcanic Group (BVG) | ||
| Previous Name(s): | Helwellyn Tuff Member [Obsolete Name and Code: Use HLV]
(-319)
Hellvellyn Formation [Obsolete Name and Code: Use HLV] (-4709) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Type Area | Nethermost, Ruthwaite and Cock Coves, adjacent to Helvellyn. | ||
| Reference(s): | |||
| Woodhall, D G, 1998. The geology of the Wythburn, Thirlmere and Fairfield areas of the north-east Lake District. British Geological Survey Technical Report WA/98/07. | |||
| Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E029 | |||