The BGS Lexicon of Named Rock Units — Result Details
Thirlmere Tuff Member
| Computer Code: | TMR | Preferred Map Code: | Tmr |
|---|---|---|---|
| Status Code: | Full | ||
| Age range: | Caradoc Series (O4) — Caradoc Series (O4) | ||
| Lithological Description: | White to pink-weathered, parataxitic, garnetiferous rhyo-dacitic lapilli-tuff and vitric tuff, locally lithic-rich and with breccia. | ||
| Definition of Lower Boundary: | Mostly faulted but locally rests conformably on bedded pyroclastic rocks at the base of the Lincomb Tarns Tuff Formation, or unconformably on sandstone (Seathwaite Fell Sandstone Formation) or andesite lavas (Birker Fell Andesite Formation). | ||
| Definition of Upper Boundary: | Conformably overlain by tuff and volcaniclastic sandstones of the Raise Beck Member (Lincomb Tarns Tuff Formation), or by undivided parts of the Lincomb Tarns Tuff Formation. | ||
| Thickness: | At least 300m | ||
| Geographical Limits: | North Lake District, around Thirlmere Reservoir, including Watson's Dodd and Stybarrow Dodd. | ||
| Parent Unit: | Lincomb Tarns Tuff Formation (LTA) | ||
| Previous Name(s): | Thirlmere Rhyolite [Obsolete Name and Code: Use TMR]
(-1868)
Thirlmere Member [Obsolete Name and Code: Use TMR] (-4372) |
||
| Alternative Name(s): | none recorded or not applicable | ||
| Stratotypes: | |||
| Reference Section | Crags on and around Steel Fell. | ||
| Type Area | Whelpside to Dunmail Raise. | ||
| Reference Section | Crags along east side of Thirlmere, to Dunmail Raise. | ||
| Reference(s): | |||
| Millward, D. 1998. Summary of the geology east of Thirlmere, part of 1:10000 Sheet NY31NW. British Geological Survey Technical REport WA/98/17. | |||
| 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. | |||
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
| E029 | |||