• Local GAPs

Slide Show

The Teme Valley

View from Abberley Hill looking towards Walsgrove Hill and Woodbury Hill.

Intoduction

The Teme Valley area is covered by the English Nature Malvern Hills and Teme Valley Natural Area. For this study the area chosen extends within this boundary from the Teme’s cutting of the hills at Knightwick to the outskirts of the village of Newnham Bridge. The area then extends either side of the Teme valley to the boundary of the Teme valley natural area in the west; to the geological division between the Teme Valley and the very disparate landscapes of the Silurian ridge of hills in the east and the Carboniferous Coal Measures of the north. This area has been chosen as it suits the scope of a pilot LGAP and suggestions in the future are that there should be widely adopted method of defining areas based on less numerous/inconsistent boundary types.

Generally this area is underlain by the Old Red Sandstone Raglan Mudstone Formation (Silurian/Devonian), which in this area is traversed by the River Teme. To the west of the Teme, above the Raglan Mudstone Formation and forming the Bromyard Plateau is a wooded escarpment of Bishops Frome Limestone forming the top member of the Raglan Mudstone Formation base and overlain by the St Maughans Formation of Devonian age. To the east is the Silurian ridge of the Abberley Hills, incorporating deposits of the Permian Haffield Breccia on the Worcester side of the hills and also at the southern bank of the Teme as it cuts through the Silurian ridge. To the north and northeast are the Highley Beds of the Carboniferous Coal Measures.

The Teme Valley forms a distinctive drop in the topography as on the eastern side of the Teme, on the Raglan Mudstones Formation, the land is of a hummocky character. This rises up to the ridge of Silurian hills which is over 150 m higher than the river in places. On the west an escarpment some 100 m high ascends to the Bromyard Plateau of the St Maughans Group.

Within this pilot LGAP, four sites have been chosen to represent the geodiversity of this small area. The sites comprise naturally occurring outcrops and man made exposures. A survey was carried out at each of the sites in accordance with the protocol already in place for RIGS recording. Therefore, each site has its own Geological Locality Record Sheet. Each site also has a summary which includes the geology of the site, ownership, potential site uses, conservation recommendations and a literature reference list etc. … → Read More

The Wye Gorge

View from Symmonds Yat Rock, Herefordshire.

The pre-Quaternary geology of the Symonds Yat area is outstanding as both the Devonian and Carboniferous systems are represented. The Lower Old Red Sandstone (ORS) is represented by the Brownstones Formation with the Quartz Conglomerate of the Upper ORS resting unconformably on this. The Tintern Sandstone is represented and is followed up the succession with the full sequence of the Carboniferous Limestone Series. The area provides excellent exposures of most of the formations with many of these now designated as regionally important. Of particular importance are the outcrops of Quartz Conglomerate, Lower Dolomite, Crease Limestone and Whitehead Limestone Formations on Little Doward Hill, Huntsham Hill, Coppet Hill and Kerne Bridge. The structure, illustrated by the associated bedding, provides excellent proof of the southwards dipping northern limb of the Forest of Dean basin.

The spectacular Quaternary features include entrenched meanders, solution caves, water worn high cliffs, limestone pavement and river terraces. The view from Yat rock is of one such meander, flowing between Huntsham Hill (Upper ORS) on the left of the photo and Coppet Hill (Quartz Conglomerate Formation up to Carboniferous Limestone series) on the right. In the distance the valley widens out onto the Brownstones Formation of the Lower Old Red Sandstone.

Two theories have been suggested for the development of the Wye Gorge. The accepted origin for the entrenched meanders of the Wye Gorge is that of superimposed drainage due to erosion during isostatic readjustment. The course of the Wye and its tributaries shows virtually no adjustment to the underlying geology or relief present today. This suggests that the river evolved on a higher strata of more recent rocks than are visible today, which have been removed by erosion, and the drainage pattern has been superimposed on the underlying strata (Miller, 1935). A recent alternative glacial theory has been put forward. Harris (2000) suggested that spillways from proglacial lakes could have been responsible for the dramatic downcutting of the river. He suggested that large volumes of debris-rich glacial meltwater could have cut the gorge we see today.

There is a high density of rock shelters and solution caves in the area, together with water worn high cliffs. King Arthur’s Cave (SO 545 158)(pictured right) is one such cave. It boasts Devensian fauna remains beneath a stalagmite floor (Barton, et al. 1997). Other caves in the vicinity include Little Doward Caves, Symonds Yat East Caves, Symonds Yat West Caves and Merlin’s Cave (Barton, et al. 1997).

Limestone pavement occurs on Little Doward Hill. Postglacial erosion of the near horizontal bedding planes has formed a smooth pavement. Solution activity has followed to form clints and grikes in the pavement. Deposits of tufa and travertine have also been recorded in the Wye Valley, near the Biblins Centre.

There is evidence of Quaternary deposition in the form of river terraces. Four terraces have been mapped by the BGS along the length of the Wye – at Bigsweir, Whitchurch and Dixton. The first terrace is discernible along much of the length of the Wye (Welch and Trotter, 1961). Terraces have been recorded at Kerne Bridge within the designated area.

Period
Series or Group
Formation
Quaternary
Holocene
Alluvium
River Gravels
Carboniferous
Carboniferous Limestone Series
Drybrook Sandstone
Whitehead Limestone
Crease Limestone
Lower Dolomite
Lower Limestone Shale
Devonian
Upper Old Red Sandstone
Tintern Sandstone
Quartz Conglomerate
Lower Old Red Sandstone
Brownstones
St Maughan’s
Raglan Mudstone
Silurian
Pridoli
Downton Castle Sandstone with Ludlow Bone Bed

The Silurian-Devonian boundary is actually situated within the Raglan Mudstone. The stratigraphy shown above is only a small part of that for the whole of Herefordshire. To see how the rocks found in the Wye Gorge relate to others in Herefordshire, click here.

References

  • Barton, R.N.E., Price, C. and Proctor, C., (1997) The Wye Valley Caves project: recent investigations into King Arthur’s Cave and the Madawg Rockshelter. In Lewis, S.G. and Maddy, D., (1997) The Quaternary of the South Midlands and the Welsh Marches: Field Guide. Quaternary Research Association pp. 63-75.
  • Harris, E., (2000) The formation of the Lower Wye Valley between Hereford and Chepstow and modification to the drainage patterns of the area during the Pleistocene era. Proceedings of the Cotteswold naturalists’ Field Club pp. 341-371.
  • Miller, A.A. (1935) The entrenched meanders of the Herefordshire Wye. Geographical Journal LXXXV (2) pp. 158-178.
  • Welch, F.B.A. and Trotter, F.M., (1961) Geology of the Country around Monmouth and Chepstow. Memoirs of the Geological Survey of Great Britain. HMSO

Howle Hill Quarry

West Quarry - The Causeway, Howle Hill, Ross-on-Wye from West side. June 1997. Field sketch by Rollo Gillespie.

The Carboniferous Lower Limestone Shales at Howle Hill are a series of transgressive marine and deltaic sediments of a back barrier and open shallow shelf environment. The overall trend of coarsening upwards is modified by several events. The Lower beds are mainly lagoonal laminated black carbonaceous shales containing the ostracods Kirkbyella and Beyrichiopsis glyptopleuroides, and also terrigenous plant material, mostly broken down into small cellular clumps.

View of the South face of The Causeway, Howle Hill Quarry.

Bed 12 is stromatolitic, of vertically stacked, linked hemispheroids. Several episodes of open shelf dominance, with a sparse brachiopod and crinoid population, are replaced by invasions of fine sediment and the return of the brackish back barrier conditions, (Beds 13-19) with Zoophycos and other trace fossils present also. Bed 23 is an apparent barrier washout, with a single trough cross-bed, ripple marks and thereafter a fully marine ecology with several types of brachiopods, crinoids, corals, bryozoa in abundance.

View of the East face of The Causeway, Howle Hill Quarry.

The Lower Dolomite, Whitehead Limestone and Drybrook Sandstone are absent at Howle Hill and the Lower Trenchard Coal Measures lie unconformably on the Lower Limestone Shales. This led to a mutually supportive mining/quarrying industry for lime burning in the 19th Century. Around 17 quarries were in use, and the Causeway is now the last remaining substantial exposure of the north edge of the Lower Limestone Shales which stretches through South Wales, Chepstow, the Forest of Dean and into South Herefordshire.