The BGS Lexicon of Named Rock Units — Result Details

Greywacke Conglomerate Formation

Computer Code: GRWC Preferred Map Code: GRWC
Status Code: Full
Age range: Wenlock Epoch (SW) — Early Devonian Epoch (DL)
Lithological Description: Conglomerate of cobbles and boulders up to 250mm diameter but most clasts are less than 70mm, mostly subrounded, consisting of greywacke, minor chert and quartzite, with a few sandstone beds.
Definition of Lower Boundary: In the type section, defined as the lowest bed of conglomerate with predominant greywacke clasts overlying the Quarry Arenite Formation. Elsewhere generally unconformable on Lower Palaeozoic rocks.
Definition of Upper Boundary: The upper surface of the highest bed of greywacke conglomerate below the overlying Swanshaw Sandstone Formation.
Thickness: From 25 m to 560 m thick.
Geographical Limits: Overlies the Lower Palaeozoic inliers in the southern part of the Midland Valley from Girvan to North Esk, on 50k sheets 14W, 14E, 15W, 23W, 23E, 24W, 32W.
Parent Unit: Lanark Group (LNK)
Previous Name(s): Greywacke Conglomerate (-1575)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Monk's Water/Douglas Water section, near Monksfoot Farm. 
Reference(s):
Rolfe, W D I, 1961. The Geology of the Hagshaw Hills Silurian Inlier, Lanarkshire. Transactions of the Edinburgh Geological Society, Vol.18, Part 3, 240-269. 
Peach, B N and Horne, J. 1899. The Silurian Rocks of Britain, Volume 1. Scotland. Memoir of the Geological Survey of the United Kingdom. 
Browne, M A E, Smith, R A and Aitken, A M. 2001. A lithostratigraphical framework for the Devonian (Old Red Sandstone) rocks of Scotland south of a line from Fort William to Aberdeen. Version 3. British Geological Survey Research Report RR/01/04. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S015 S024 S015 S033 S023 S023 S008 S007 S008 S032 S032 S014 S014 S022