The Wrekin & The Ercall

Also within

Shropshire County Shropshire Hills Scenic Area

Condition (Natural England)

Geology & landscape

Geological Feature: Rock Outcrop · Mining / Industrial: Quarry · Geological Period: Cambrian, Precambrian · Rock Type: Gneiss, Quartzite, Sandstone

Landscape processes: Volcanic / Igneous

Birds & fish recorded

Birds

Description

Area, 283.3 ha. 700.2 ac. Description A prominent ridge which is of geological and biological importance. It forms the northeastern extremity of the South Shropshire Hills Area of Outstanding Natural Beauty. The area is extensively used for recreation. Biology The site is particularly valuable for the range of woodland vegetation which occurs at the northern end of the Wrekin and on the Ercall. Different types of woodland show a strong correlation with the underlying geology and with drainage. Much of the Ercall is occupied by sessile oak Quercus petraea woodland on thin, acidic soils overlying the Wrekin Quartzite. Other tree species present in this woodland type include holly Ilex aquifolium, downy birch Betula pubescens and rowan Sorbus aucuparia and the ground flora is dominated by species characteristic of acidic soils, such as wavy hair grass Deschampsia flexuosa, heather Calluna vulgaris, bilberry Vaccinium myrtillus, creeping soft grass Holcus mollis and the uncommon climbing fumitory Corydalis claviculata. Oak with hazel Corylus avellana occurs on slightly more fertile soils. On damper and more base rich soils, the woodland is characterised by ash Fraxinus excelsior and wych elm Ulmus glabra, although, as in many Shropshire woods, the elm is now mostly dead or dying. Where the ground is permanently wet, alder Alnus glutinosa is the dominant species. Ground flora species characteristic of the more fertile woodland vegetation types include ramsons Allium ursinum, yellow archangel Lamiastrum galeobdolon, woodruff Galium odoratum, dog’s mercury Mercurialis perennis and sanicle Sanicula europaea. Towards the summit of the Wrekin there are areas of heathland dominated by heather and acidic grassland with wavy hair grass, early hair grass Aira praecox, sheep’s sorrel Rumex acetosella and heath bedstraw Galium saxatile. There is a varied bird population. Breeding species include sparrowhawk Accipiter nisus, woodcock Scolopax rusticola, all three British woodpecker, seven species of warbler and redstart Phoenicurus phoenicurus. Geology The Wrekin ridge provides the best and most varied exposures of Uriconian rocks in England. This site is of great historical importance, as the place where the unconformable relationship between the Uriconian and Cambrian and the volcanic nature of the Uriconian, were first demonstrated. Recent radiometric dating of these rocks strongly suggests an early Cambrian, rather than Precambrian, age for this part of the Uriconian. The site also includes the small but significant outcrop of primrose Hill Gneiss, which resembles rocks found in the Malverns and has been interpreted as a rare relic, pre dating the Uriconian. The Uriconian has provided important evidence in attempts to reconstruct the early evolution of an ancient sea called the Iapetus Ocean and provides a valuable link with several other exposures of the early basement rocks in England, Wales and Canada. The Ercall Quarry contains the most instructive section available through the Wrekin Quartzite and lower part of the Lower Comley Sandstone Comley Series, Lower Cambrian. The conglomerates and massive quartzites of the Wrekin Quartzite contain a variety of sedimentary features which are a record of the submergence of the old Pre cambrian landmass by the sea in Cambrian times. The overlying greenish sandstones contain thin, nodular, lime rich beds and beds burrowed by marine animals. These rocks are of great importance in that they yield the oldest fossils apart from trails etc in this region. These are small shelly fossils and include brachiopods, hyolithellids and various, as yet, unclassified phosphatic forms. These provide the only links between the classic Lower Cambrian succession in Shropshire used as the British standard of reference and the equivalent strata in the English Midlands, the Malvern Hills, Scandinavia and Asia. Both units contain new and unusual assemblages of fossil traces. The site is of great importance in the interpretation of Lower Cambrian stratigraphy in Britain.

Species mentioned