The BGS Lexicon of Named Rock Units — Result Details

Lake District Devonian Minor Intrusion Suite

Computer Code: LDDMI Preferred Map Code: notEntered
Status Code: Full
Age range: Early Devonian Epoch (DL) — Early Devonian Epoch (DL)
Lithological Description: Quartz feldspar-phyric microgranite, plagioclase-biotite-phyric microgranodiorite, and rhyolite dykes and minor intrusions. Examples of these dykes in the Scafell area have the following radiometric ages: 393 +/- 9 Ma, 392 +/- 4 Ma ( Rb-Sr whole rock) (Al Jawadi, 1987).
Definition of Lower Boundary: Includes all dykes, sills and other minor intrusions in the Lake District of proved and inferred Lower Devonian age.
Definition of Upper Boundary: Not defined.
Thickness: Not defined.
Geographical Limits: Within the Lake District Lower Palaeozoic inlier of Cumbria, and in the Cross Fell Inlier.
Parent Unit: Caledonian Supersuite (CIGSS)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Duddon valley, south from Troutal to Logan Beck: various SW-trending dykes of porphyritic microgranite exposed in the river and stream banks. Millward and 22 others 2000 
Type Area  Kirk Fell to Great Bank, Wasdale: a major dyke of quartz-feldspar-phyric microgranite. Millward and 22 others 2000. 
Reference(s):
Morrison, J. 1918. The Shap minor intrusions. Quarterly Journal of the Geological Society, London. Vol.74, 116-144. 
Al Jawadi, A E. 1987. Minor igneous intrusions of the Lake District; geochronology, geochemistry and petrology. PhD thesis, University of Newcastle. 
Millward, D. 2002. Early Palaeozoic magmatism in the English Lake District. Proceedings of the Yorkshire Geological Society, Vol. 54, Part 2, 65-93. 
Millward, D, Johnson, E W, Beddoe-Stephens, B, Young, B, Kneller, B C, Lee, M K, Fortey, N J, Allen, P M, Branney, M J, Cooper, D C, Hirons, S, Kokelaar, B P, Marks, R J, McConnell, B J, Merritt, J W, Molyneux, S G, Petterson, M G, Roberts, B, Rundle, C C, Rushton, A W A, Scott, R W, Soper, N J and Stone, P. 2000. Geology of the Ambleside district. Memoir of the British Geological Survey, England and Wales, Sheet 38. 
Soper, N J and Kneller, B C. 1990. Cleaved microgranite dykes of the Shap swarm in the Silurian of NW England. Geological Journal, Vol.25, 161-170. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E039 E038 E047 E030 E024 E003 E037 E029 E048