Dingle Quarry

Malverns Complex

Dingle Quarry

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

Dingle Quarry is split into three different levels: Lower, Middle and Upper Dingle. Lower Dingle is located to the rear of a bus stop, with much of the exposure obscured by vegetation. Middle and Upper Dingle are located off a path directly above the bus stop. Middle Dingle can be easily accessed, whereas Upper Dingle can not be accessed safely.

Middle and Upper Dingle:

Diorite is the predominant rock type in Dingle Quarry, which is intruded by granites and a large dolerite dyke.

The dolerite dyke is 4m thick and forms a step in the quarry floor which separates Middle Dingle from Upper Dingle. The dyke is orientated NW/SE. The precise age of the dyke is unknown, but it is one of the youngest features within the quarry as it intersects the diorite mass, as well as the smaller granitic veins and intrusions. The lack of foliation in the dolerite indicates that it was intruded after the period of compression that gives the granites and diorite mass their foliated fabric. A chilled margin can be viewed in places where the dolerite was intruded into cold country rocks (i.e. the granites and diorite had already cooled down).

As well as the dolerite dyke there are some small granitic intrusions in the diorite, which are truncated by the dyke. Granite is also present in the north-east corner of the quarry. The granites and diorites in the quarry are foliated, which formed during compressional deformation that took place during the Precambrian era of geological time.

Dingle Quarry provides geologists with the opportunity to view the order of events that occurred to create this part of the Malvern Hills:

Intrusion of the main diorite mass
Intrusion of the small granitic veins
Diorites and granites were compressed to produce the foliated fabric
Intrusion of second phase of granitic material (evidence from lack of foliation)
Intrusion of dolerite dyke

Normal faulting occurs between the dolerite dyke and underlying diorites.

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

Terminology

Dyke – A sheet like, near vertical minor intrusion.

Chilled margin – The fine grained, outer layer of an igneous body formed by rapid cooling

Photos

General view of Lower Dingle

Middle and Upper Dingle quarry. Dolerite dyke seen as step separating the two levels as a step.

Sharp contact between the dolerite dyke (bottom) and Malverns Complex granite (top).

General view of Lower Dingle

Diagram illustrating the relationships between different rock types at Dingle Quarry.

Diagram illustrating calcite mineralisation at the boundary between the dolerite dyke and Malverns Complex granite.

References

Barclay W.J. et al. (1997) Geology of the county around Worcester. British Geological Society Memoir. London.

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).

Timins Rev J.H. (1867). On the Chemical Geology of the Malvern Hills. Proc. Geol. Soc.

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