Arkley, S. L. B., Browne, M. A. E., Albornoz-Parra, L. J. and Barron, H. F. 2011. East Dumbartonshire Geodiversity Audit. British Geological Survey Open Report, OR/09/19. 265pp.
EDC 3: Board Craigs Quarry, Twechar
Grid reference:
Site type: Artficial quarry works
Site ownership: Not known
Current use: Disused
Field surveyor: Sarah Arkley & Luis Albornoz-Parra
Current geological designations: None
Date visited: 5th March 2009
Site map
Summary description
Disused quartz-microgabbro quarry, formerly used for roadstone. Recorded as an 'old quarry' in
Robertson, 1937 and on the1922/23 Ordnance Survey map.
This intrusion is part of the Midland Valley Sill Complex intruding into the upper part of the Limestone
Coal Formation (above the Meiklehill Main Coal).
Approximately 10m high cliff faces are exposed along an escarpment through the quartz-microgabbro sill. The medium/coarse-grained nature of the rock would suggest the quarry was positioned in the middle part of the sill, the height of the faces give some indication to the thickness of the intrusion. No evidence of top or base of the sill seen. The exposures vary in their quality along the escarpment, but some areas display good sub-vertical columnar jointing and rusty coloured weathering, typical of a basic igneous intrusion with its high Fe/Mg mineral content. There are also good examples of spheroidal and biological weathering here.
Great views from the site northwards across the Kelvin valley to the Kilsyth Hills and Campsie Fells.
EDC 3: Stratigraphy and rock types
Age: Upper Carboniferous Formation: Midland Valley Sill-Complex
Rock type: Quartz-microgabbro
Assessment of site value
Access and safety
Aspect/Description
Road access and parking Street parking is available in the housing estate at the southern edge of Twechar village, opposite the school. Footpath from here heads uphill across grassy farmland to wooded area where the exposures are. Need to cross old barbed wire fence to access woodland. Few minutes walk.
Safety of access Gently sloping ground in fairly open mature woodland, access is fine with a little care.
Safety of exposure Quarry faces should be checked for any loose material which may fall. Permission to visit No permission sought
Current condition Good; moss and ivy growing in places on the quarry faces but generally they are well exposed. Some good biological weathering where tree roots are growing in the joints of the microgabbro. Minor amounts of household/garden rubbish in places, generally clean.
Current conflicting activities None
Restricting conditions None known
Nature of exposure Vertical quarry faces
Culture, heritage & economic
Historic, archaeological & literary associations None known. Rating: 0.
Aesthetic landscape Farmland at the edge of the village of Twechar. Good views over 2 the village to the Kilsyth Hills
History of earth sciences None known. Rating: 0.
Economic geology Former road metal quarry. Rating: 2.
EDC 3: Geoscientific merit
Current site value
Community Dog walkers and local residents are likely to visit the fields adjacent to the site, located immediately behind a residential estate. Rating: 8.
Education The quarry exposes typical features associated with the middle part of a thick sill, and some examples of spheroidal and biological weathering. Rating: 4.
Fragility and potential use of the site
Fragility Geohazard
Potential use: School
Geodiversity value
Geologically this site displays a good section through the middle part of a thick quartz- microgabbro intrusion, combined with being used as a local resource and the great view to the Campsie Fells. Rating: 3.