The BGS Lexicon of Named Rock Units — Result Details

Great Whin Sill

Computer Code: GWHIN Preferred Map Code: notEntered
Status Code: Full
Age range: Late Mississippian Epoch (CMIL) — Cisuralian Epoch (PLC)
Lithological Description: A locally pegmatitic quartz-dolerite, with finer grained 'chilled' contact rock. Sills are typically columnar jointed, and comprise up to three leaves are present in places. The component sills and associated dykes cut strata up to and including those of Carboniferous, Duckmantian (Westphalian B) age, and derived pebbles are reworked into breccias of Early Permian age. Radiometric dates (K-Ar, Ar-Ar and U-Pb) are in the range of 301-294 Ma. The large volume of literature on this sill is listed, referred to and discussed in Stephenson et al., 2003.
Definition of Lower Boundary: Taken at the sharp intrusive contact of the component sills, where they are in contact with sedimentary strata below.
Definition of Upper Boundary: Taken at the sharp intrusive contact with the strata overlying the sill.
Thickness: Individual leaves average a thickness of about 30m; the thickest individual leaf is 73 m.
Geographical Limits: Crops out throughout Northern England from Holy Island, south to Alnwick, to the Hadrian's Wall country, and to the Pennine escarpment to Teesdale; proved in mine workings and boreholes to underlie the area, enclosed at the east of the outcrop, and may extend for some considerable distance offshore.
Parent Unit: Whin Sill Complex (WHINS)
Previous Name(s): WHIN SILL (WHSI)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  High Force and High Force Quarry, Teesdale, Co. Durham. 
Reference(s):
Stephenson, D, Loughlin, S C, Millward, D, Waters, C N and Williamson, I. 2003. Carboniferous and Permian igneous rocks of Great Britain, north of the Variscan Front. Geological Conservation Review Volume 27. Joint Nature Conservation Committee: Peterborough. 374 pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E004 E024 E006 E019 E025 E031 E009 E013 E014 E018 E026