Woodbury Quarry

Exposed Rock units: Lower Ludlow Shales, Aymestry Limestone, Upper Ludlow Shales, Anglian Deposits (Wolston Formation)

Conservation Status: Site of Special Scientific Interes, Local Geological Site

Woodbury Quarry exposes a complete succession through the Ludlow Shales and Aymestry Limestone Formations.  It is a unique site and one of the finest Silurian sections in the Welsh Borderlands.  This active quarry provides extensive and continuous exposure through much of the Mid-Silurian and the whole of the Upper Silurian succession of the Abberley area.  The highly fossiliferous rocks, coupled with the interesting sedimentology, make this locality a very important site for continuing research into Silurian palaeontology and palaeoenvironments.

The Lower Ludlow Shales at this site comprises buff coloured shales with thin limestone bands and nodules.  Towards the top of the succession, a 35cm thick, bentonitic clay is present. The fauna is rich and varied with brachiopods, trilobites, cephalopods and ostracods being commonly found.  Rare corals, bivalves and gastropods also occur.

The Aymestry Limestone Formation at Woodbury Quarry is variably made up of silty limestones and nodular limestones, with a poor fossil content that includes brachiopods and rare bivalves, gastropods and corals.

The entire succession of the Upper Ludlow Shales is preserved, encompassing the Mocktree Shale Member, the Woodbury Shale Member and the Whitcliffe Flags Member.  These three units are dominated by calcareous siltstones, although limestones are more common in the Mocktree Shale Member. The units are defined in the quarry by their differing faunal successions, which contain varying species of brachiopods, bivalves, cephalopods, gastropods, ostracods, corals and trilobites.

A rare exposure of Anglian-age deposits rests unconformably on rocks of the Aymestry Limestone Formation.  The unconformity is well displayed on an extensive quarry bench. The basal bed of the sequence is a till that contains fragments of Devonian- and Silurian-age material.  This is overlain by red-brown fluvio-glacial silts, sands and gravels showing current bedding, imbrication and channels.  Part of the exposure shows yellow sands with coal clasts and derived fossils are common.

Other rock units are also present at Woodbury Quarry, such as the World-famous Ludlow Bone Bed and Downton Castle Sandstone which sequentially overlie the Whitcliffe Flags Member. These are not extracted for aggregate and so are not considered further.

Terminology
Fossiliferous – Containing fossils.

Bentonitic (sic bentonite) – Clay layers formed from the alteration of volcanic ash.

Imbrication – vertical stacking of clasts in a sedimentary rock formed by currents.

Photos

View of Woodbury looking east. This image shows the buff-coloured Lower Ludlow Shales overlain by the Anglian-age Wolston Formation. A bench forms directly on top of the cliff face and the Wolston Formation lies on top of this bench, where it forms a thick layer of pale brown sediments.

Active quarrying at Woodbury Quarry during the late 1990’s.

References

Cottle, R., 1993, Woodbury quarry SSSI: Geological site documentation/management brief, English Nature, London.

Lawson, J.D., 1956, ‘The Ludlovian rocks of the Welsh Borderland’, The Advancement of Science, vol. 12, pp. 563-570.

Holland, C.H., Lawson, J.D., and Walmsley, V.G.A., 1959, ‘Revised classification of the Ludlovian succession at Ludlow’, Nature, vol. 184, pp. 1037.

Phipps, C.B., 1957, ‘The structure and Stratigraphy of the Silurian rocks West of the South Malvern Hills’, PhD Thesis, University of Birmingham, Birmingham, pp. 235.

March 2011