Gardiners Quarry

Exposed Units: Malverns Complex

Conservation Status: Local Geological Site; SSSI; Within an AONB

Gardiners Quarry is one of many aggregates quarries that can be found across the Malvern Hills. Found on the western side of the hills, it is a small quarry; 30m across and 15m high. Currently the quarry is used as a Malvern Hills Conservators car park, as it one of the main points of access to the hills above.

The dominant rock type in Gardiners Quarry is diorite belonging to the Malverns Complex. A metadolerite dyke is located in the centre of the quarry.

Throughout the quarry there is also a series of pegmatite dykes. Made of a coarse granitic material, these pegmatites cut through the diorites that compose the majority of the exposure within the quarry. Muscovite, together with minor amounts of biotite, chlorite and epidote can be found as accessory minerals

In the south eastern part of the quarry there is a large granitic intrusion which has been sheared intensely. This zone of shearing is thought to be the continuation of the NW-SE trending Colwall Fault; a normal fault that runs through the village of Colwall, north-west of Gardiners Quarry.

Both the diorite and granite within the quarry have a sheared fabric. This shearing occurred during the first phase of metamorphism experienced by the rocks of the Malvern Hills. The intensity of shearing varies throughout the exposure. The shearing has also made rock boundaries and the relationships between rock units hard to determine.

From the quarry, the landscape of Herefordshire can be viewed, with the prominent ridges made of Silurian limestone running parallel to the Malvern Hills. Beyond these ridges the Woolhope Dome and Shucknall Inlier can be identified, with the flat Herefordshire plain in the distance. On days where the visibility is high, the Black Mountains of the Welsh Borderlands can be seen.

This site is part of the Community Earth Heritage Champions Project.

Terminology

Sheared – Where a rock is subject to directional stress (i.e. pressure with a directional element), minerals in the rock to realign according to the direction in which the pressure is directed.

Normal Fault – Movement along a line of weakness in the Earth’s crust where the hanging wall (land on top of the fault) is displaced downwards relative to the footwall (land underneath the fault).

Inlier – An area of older rocks surrounded by younger rocks

Photos

General view of Gardiners Quarry.

Granitic intrusion in zone of intense shearing (facing East).

References

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British Geological Survey (1993) Geology of the country around Worcester. Sheet 199: 1:50,000

Bullard D.W. (1989) Malvern Hills; A student’s guide to the geology of the Malverns. Nature Conservancy Council. Peterborough.

Butcher N.E. (1962) The Tectonic Structure of the Malvern Hills. Proc. Geol. Soc. 73 pp.103-123.

Falcon N.L (1947) Major Clues in the Tectonic History of the Malverns.

Fitch F.J. (1966) Isotopic age determinations on rocks from Wales and the Welsh Borderland. pp. 22-45 in Pre-Cambrian and Lower Palaeozoic rocks of Wales. Wood, A (Editor). University of Wales Press.

Kellaway G.A. and Hancock P.L. (1983) Structure of the Bristol District, Forest of Dean and the Malvern Fault Zone. in The Variscan Fold Belt in the British Isles. Hancock P.L. (Editor). Adam Hilger LTD. Bristol.

Lambert R. St J. and Holland J.G. (1971) The Petrography and Chemistry of the Igneous Complex of the Malvern Hills, England. Proc. Geol. Ass. 82. pp. 323-352.

Penn J.S.W. and French J. (1971) No 4: The Malvern Hills. Geologists Association Guides.

Pharoah T.C. et al. (1987) Geochemical Evidence of the Tectonic Setting of Late Proterozoic Volcanic Suites in central England. Geol. Soc. Special Publication No. 33. pp. 541-552.

Pharoah T.C and Gibbons W. (1994) Chapter 10: Precambrian rocks in England and Wales south of the Menai Strait Fault System. from Gibbons W. and Harris A.L: A revised correlation of Precambrian rocks in the British Isles. Geol. Soc. Special Report No. 22.

Phipps C.B. and Reeve F.A.E. (1967) Stratigraphy and Geological History of Malvern, Abberley and Ledbury. Geological Journal. 5 (2).

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Thorpe R.S. (1972) Possible subduction zone origin for two calc-alkaline plutonic complexes from Southern Britain. Bulletin of the Geological Society of America. 83 pp. 115-120.

Thorpe R.S. (1987) Psuedotachylite from a Precambrian shear zone in the Malvern Hills. Proc. Geol. Ass. 98 (3) pp. 205-210.

Tucker R.D. and Pharoah T.C. (1991) U-Pb zircon ages for Late Precambrian igneous rocks in Southern Britain. Journal of the Geological Society. 148 pp. 435-443.

Woodcock, N and Strachan, R. 2000.Geological History of Britain and Ireland. Blackwell Publishing.

March 2011