Exposed Units: Shatterford Dyke, Etruria Formation
The intrusion is widely known as the ‘Shatterford Dyke’, however the structure is apparently intruded parallel to the grain of the country rock, meaning that it is technically a sill.
The Witnell’s End Quarries are a series of at least six disused quarries scattered in woodland along a prominent ridge. It is bounded in the west by a stream and in the east by the eastward sloping ridge-side. There is evidence of significant quarrying with some good exposures, plenty of quarry waste and scree. There are also good natural outcrops in the stream bed.
The intrusion is well exposed in two of the quarries, where it has a dolerite composition. It is a hard, dark grey, fine-grained rock with well defined jointing that dips steeply to the east. Spheroidal weathering is present in some of the exposures and where it has been intensely weathered, the rock takes on a brown colouring and is more prone to erosion – this eroded material forms the scree deposits.
The Shatterford Dyke is intruded into the Etruria Formation, which consist of grey, brown and red clays and are seen towards the north end of the area of interest. It is possible that the contact between the dolerite intrusion and the host sedimentary rocks may be exposed in a stream bed but this has not yet been located.
Terminology
Dyke/sill – A body of igneous rock that has been intruded into the surrounding rocks and has a ‘sheeted’ geometry. In a dyke, this ‘sheet’, cuts across the sedimentary layering in the surrounding rocks. In a sill, the sheet is intruded parallel to layering in the surrounding rock.
Spheroidal weathering – A weathering process, whereby shells of surface material on a rock face flake off, leaving ‘spherical’ bulges on the rock face (see picture).
Photos
General view of the exposure at Witnell’s End Quarries.
General view of the exposure at Witnell’s End Quarries.
Spheroidal weathering in the dolerite dyke.
Exposures of dolerite in the path near to the Witnell’s End Quarries.
References
Anon, 1990, Special wildlife sites in Hereford and Worcester with geological interest, Worcestershire Nature Conservation Trust, pp. 13.
Fitch F.J. and Williams, S.C., 1970, ‘Isotopic ages of British Carboniferous rocks’, Conference Report, 6th Congress of International Stratigraphy, Sheffield, vol. 2, pp.771-789.
King, W.W., 1921, ‘The geology of Trimpley’, Transactions of the Worcestershire Naturalists’ Club, vol. 7, 4, pp. 319-322.
Whitehead, T.H. and Pocock, R.W., 1947, ‘Dudley and Bridgnorth, Sheet 167’, Memoir of the Geological Survey of Great Britain, London, pp. 226.
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