Brockhill Court Quarry

Exposed Units: Brockhill Dyke, Raglan Mudstone

Conservation Status: Local Geological Site

The Brockhill Dyke is a type of intrusive igneous rock with a dolerite/teschenite chemistry, which has been extensively quarried for aggregate at this site. It was intruded into the surrounding sandstones and marls at a time when these country rocks were cold. This created a marked temperature gradient between the sedimentary ‘country rocks’ and the hot, molten igneous intrusion and resulted in the formation of a baked margin.

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Terminology

Dyke – A body of igneous rock that has been intruded into the surrounding rocks and has a ‘sheeted’ geometry. This ‘sheet’ cuts across the sedimentary layering in the surrounding rocks.

Marl – A type of mudstone that consists of clay and carbonate, i.e. a lime-rich mudstone.

Country rock – The host rock into which an igneous rock has been intruded. It is also termed ‘surrounding rocks’ in this entry.

Baked margin – The part of the country rock that is immediately adjacent to an igneous intrusion. High temperatures experienced by the country rock during the intrusion of an igneous body can cause clay-rich rocks to become baked in the immediate vicinity of the intrusion. The effect of this baking decreases with distance from the intrusion.

References

Bailey, E., 2002, ‘Malvern Hills – May 18th 2002’, Magazine of the Geologists Association, vol.2, pp.10-11.

Baker, J.W., 1947, ‘The Geology of the West Malvern District’, Thesis, University of Birmingham, Birmingham, pp.48.

Bennett, A.G., 1942, The Geology of Malvernia, Malvern Naturalists’ Field Club, Malvern, pp.73

Duncan, C.C., 1928, ‘Southstone Rock and Brockhill’, Transactions of Worcester Naturalists Club, years 1923-31, pp. 299.

Guppy, E.M. and Sabine, P.A., 1956, ‘Chemical analysis of igneous rocks, metamorphic rocks and minerals’, Memoir of the British Geological Survey, London.

Hallimond, A., 1939, ‘Magnetic observations on the Brockhill Dyke’, Bulletin of the Geological Survey of Great Britain, vol. 2, pp.85-92

Hamblin, R.J.O., 1983, Geological notes and local details for 1:10000 sheet SP 07 SW (Alvechurch), British Geological Survey, London, pp.20.

Miller, C.G., 1995, ‘Ostracod and Conodont distribution across the Ludlow/Pridloi boundary of Wales and the Welsh Borderlands’, Palaeontology, vol. 38, pp. 341-384.

Murchison, R.I., 1839, The Silurian System, founded on geological researches in the counties of Salop, Hereford, Worcester and Stafford; with descriptions of the Coal fields and overlying formations, vo. 1,

John Murray, London, pp.185-194.

Penn, J.S.W., 1969, ‘The Silurian rocks of the west Malvern Hills from Clencher’s Mill to Knightsford Bridge’, PhD Thesis, University of London, London, pp.145.

Phillips, J., 1845, Brockhill dyke and quarry, Field notebook 5 Apr-22 Apr, Geological Survey of Great Britain, pp.55.

Phillips, J., 1848, ‘The Malvern Hills, compared with the Palaeozoic districts of Abberley, Woolhope, May Hill, Tortworth and Usk’, Memoir of the Geological Survey, vol. 2, pp. 330.

Reeve, F.A.E., 1953, ‘The structure of the Silurian rocks of the Malvern and Abberley hills Worcestershire’, PhD Thesis, University of Birmingham, Birmingham, pp.286,

Richards, T.D., Chapman, E., Ashbee, E. and Gillespie, R., 2008, Worcestershire Geodiversity Action Plan phase 2: Geodiversity Audit. Final Report, Herefordshire and Worcestershire Earth Heritage Trust, Worcester, pp.79pp.