The BGS Lexicon of Named Rock Units — Result Details

Yarlside Volcanic Formation

Computer Code: YRL Preferred Map Code: Yrl
Status Code: Full
Age range: Cautleyan Stage (OU) — Cautleyan Stage (OU)
Lithological Description: Pink to pale grey, flow banded rhyolitic vitrophyre (felsite), locally with beds of massive tuff and lapilli-tuff, particularly at the base.
Definition of Lower Boundary: Taken at the base of volcanic rocks (generally the felsite, but locally tuff and lapilli-tuff) overlying calcareous siltstone of the Stile End Formation. In part overlies andesite of the Borrowdale Volcanic Group.
Definition of Upper Boundary: Defined by the base of the overlying Kirkley Bank Formation.
Thickness: Up to 325m
Geographical Limits: In the northeastern Lake District, from near Stile End (NY 471 047) to Shap Wells (NY 577 096).
Parent Unit: Dent Group (DNT)
Previous Name(s): Stockdale Rhyolite Member (-3151)
Stockdale Rhyolite (-542)
Stockdale Rhyolite Formation [Obsolete Name And Code: Replaced By YRL] (SRH)
Yarlside Rhyolite (-3693)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Stockdale Beck, Longsleddale, Cumbria Lawrence et al., 1986 
Reference(s):
Lawrence, D J D, Webb, B C, Young, B and White, D E. 1986. The geology of the Late Ordovician and Silurian rocks (Windermere Group) in the area around Kentmere and Crook. Includes map, 1:25,000 series, Parts of Sheets NY40 and SD49 Kentmere and Crook, Solid and Drift Geology. Report of the British Geological Survey, 18/5. 
Kneller, B C, Scott R W, Soper N J, Johnson E W and Allen P M, 1994. Lithostratigraphy of the Windermere Supergroup, Northern England. Geological Journal, Vol. 29, 219-240. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E039 E030