The BGS Lexicon of Named Rock Units — Result Details

Threlkeld Intrusion

Computer Code: THKD Preferred Map Code: notEntered
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: A garnet-bearing, alkali feldspar-quartz-plagioclase-phyric microgranite. Age: 451.0 +/- 1.1 (2-sigma) Ma (U-Pb, zircon), Millward, D and Evans, J A, 2003.
Definition of Lower Boundary: Not defined.
Definition of Upper Boundary: Not defined.
Thickness: A laccolith 0.5 to 1km thick and with an area of about 12 sq. km intruded into the Skiddaw Group and lowermost part of the Borrowdale Volcanic Group.
Geographical Limits: Low Rigg [NY 305 230],Threlkeld Knotts [NY 328 238], around White Pike [NY 339 229] and in Bramcrag Quarry, east of Keswick,Cumbria.
Parent Unit: Lake District Ordovician Felsic Plutonic Suite (LDFP)
Previous Name(s): Threlkeld Microgranite (-3723)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Bramcrag Quarry, east of Keswick Cumbria. Wadge et al.(1974), Loughlin (1999). 
Reference(s):
Loughlin, S C.1999. Bramcrag Quarry in Stephenson, D, Bevins, R E, Millward D, Highton, A J, Parsons I, Stone P, and Wadsworth W J. Caledonian igneous rocks of the British Isles. (Peterborough: Joint Nature Conservation Committee.) >References cited contain other important subsidiary references. 
Wadge A J, Harding, R R, and Darbyshire, D P F. 1974.The Rb-Sr age and field relations of the Threlkeld Microgranite.Proceedings of the Yorkshire Geological Society, Vol.40, p.211-222.>References cited contain other important subsidiary references. 
Woodhall, D G. 2000. Geology of the Keswick district. British Geological Survey Sheet Description, England and Wales, Sheet 29. 
Millward, D and Evans, J A. 2003. U-Pb chronology and duration of Upper Ordovician magmatism in the English Lake District. Journal of the Geological Society of London, Vol. 160, 773-781. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E029