• 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.

Potential Geodiversity

Silurian
Pridoli – Lower Old Red Sandstone – Raglan Mudstone Formation Raglan Mudstone Formation and has at its base the Ludlow Bone Bed which appears to rest conformably on the on the Upper Ludlow Shales at the top of the Silurian sequence. The bone beds are coarse micaceous sandstones containing the fish debris that gave the beds their name. Above this are grey shales and beige sandstones which make up the Temeside Beds. There is then a change from grey beds to red marls and micaceous sandstones followed by a band of pebbly coarse sandstones which may be correlated with the Holdgate Sandstone. This coarse layer can be found north of Abberley and may correspond to a similar deposit near Stanford Bridge. Red, green and purple marls dominate and replace the sandstones further up the sequence, towards the base of the Bishops Frome Limestone. In the Teme valley below Stanford Bridge and on both sides of the river these rocks consist of red and green marls with distinctive belts of sandstone. The Raglan Mudstones represent fluvial sedimentation in a hot, low rainfall climate.

The Bishops Frome Limestone (previously Psammosteus Limestone) forms the top part of the Raglan Mudstone Formation. It is best exposed at the western side of the Teme Valley and forms an almost continuous bed along the valley escarpment. The rock is pale greenish limestone which is both massive in some areas and interbedded with marl in others. Sections are generally exposed here by way of a gullies cut in to the rock by streams. The exposures of the bishops Frome limestone are frequently obscured by tufa deposited by the springs at this limestone band.

Devonian
Lower Old Red Sandstone – St Maughans Formation Above the Bishops Frome Limestone lies the St Maughans Formation. Due to the continental deposition of these rocks, the Silurian – Devonian boundary (as defined by marine fossils) is difficult to place. Generally the Raglan Mudstone is said to be Silurian for the greater part and the St Maughans Formation is Devonian. The St Maughans Formation has mudstones as its dominant sediment type. Sandstones are more abundant in this formation however than the Raglan Mudstone Formation. The marls are a dull red colour and are more compact than the sediments of the Raglan Mudstone Formation. Their grading in to fine, marly sandstones is often indiscernible. In places are hard bands/nodules of red and grey calcareous marlstone, forming an intermediated between the common marls and the limestone. The sandstone colour in this formation has been noted to be anything from red to brown to purple and grey. They are calcareous in nature and fine grained. Sedimentary structures include widespread current bedding which hinders determination of the dip of a given section. The sandstone bands themselves are said to be lenticular based on an inability to match the sandstone bands across stream sections. Immediately above the Bishops Frome Limestone the sandstone is massive, as is another section roughly 90 to 100 m above the Formation’s base. This second massive sandstone is often associated with calcareous intraformational conglomerates (conglomeratic cornstones). The conglomerates do not generally exceed 2 m in thickness and are constantly lenticular, passing laterally into sandstones or marls.

Permian
Dolerite Dyke A Dolerite dyke intrudes in to the Raglan Mudstone Formation at Brockhill in the Teme Valley. It is visible on the east bank of the river in a quarry and again on the opposite side but in smaller exposures. The dyke runs in a westerly direction for approximately 1200 metres and has affected the course of the Teme, which runs along it for some way before breaching the hard rock barrier to produce a noticeable meander. At its maximum the dyke is around 7.5 m thick at its centre. Its mineralogy is of an alkali gabbro (teschenite) with pyroxene, serpentized olivine, intermediate plagioclase and interstitial calcite. Along its margins it consists of a 2.5 to 5 cm band of quartz dolerite with pyroxene, lathy feldspar and quartz. There is no contact between these two igneous types suggesting that the quartz-dolerite has resulted from acidification of alkali gabbro magma prior to emplacement. The country rock is altered to a distance of around 9 m on each side of the intrusion converting the marls to a purple rock with light spots of calcite, analite, chlorite and garnet. Tridymite needles have also developed around the quartz grains in the sandstone indicating a temperature range of 870 to 1470°C. The cornstone has become a quartz-calcite-garnet-hornfels. Radiometric dating of two samples from the dyke at Lowe’s Hill yielded ages of 260 +/- 20 my, and 286 +/- 18 my.

Haffield Breccia The Haffield (or Clent) Breccia is Permian in age and is composed of angular fragments and blocks of volcanic rocks in a sand/marl matrix. The rock is haematite stained and so is a dull red in colour. The deposits at Woodbury and Abberley have been described to contain numerous greenstone, felstone, ashy conglomerate, greenstone-amygdaloid, feldspathic ash and porphyry, purple grit, red conglomerate, micaceous marl, green banded slate, ribboned slate and altered black and green slate. The origin of these rocks is said to be locally derived through erosion and transportation by rivers from rocks now buried beneath the Trias that stood proud as highlands during the Late Carboniferous. The deposit at Osebury Rock near Lulsley has been correlated with both the Clent and Haffield Breccias in the past. Generally, the rock is now thought to be of Permian age and is described as Haffield Breccia. Further proof of the age of the unit is needed as an alternative idea places the age at late Carboniferous. This is based on its location west of the East Malvern fault, giving rise to the possibility that it predates the rifting and formation of the Worcester Graben. Bridgnorth Sandstone At Osebury Rock the Haffield Breccia can be seen to pass conformably up in to the Bridgnorth Sandstone Formation. This formation represents aeolian windblown sands and is regarded as being of Lower Permian age. The sandstone is generally uniform in thickness and consists of well sorted, fairly well rounded coarse-grained quartz with haematite coatings. Large scale cross bedding can be seen in beds 15-20 m thick. Foresets, up to 4 m thick, consistently dip southwards to indicate depositing winds that originated from the north. The sandstone has little cement and is very friable.

Quaternary to Recent
Tufa Calcareous tufa and travertine is found on the escarpment on the west side of the Teme. The tufa is found in valleys that cut the escarpment, beneath springs in the vicinity of the band of Bishops Frome Limestone which is the likely source for the calcium carbonate. Deposition of tufa and travertine continues today but at a much slower rate than previously. Tufa is formed around the moss Palustriella commutate. In some areas of the deposits, shade-demanding species dominate the assemblage which indicates the presence of forest cover. In contrast the presence of Palustriella indicates broken canopy. The largest deposit and a prior designated SSSI site is Southstone Rock.

Structural Geodiversity

The structure of the area in question is very much a story of the Malvern Axis and the Palaeozoic terrane to the west of it. The Malvern Axis marks a Proterozoic zone of crustal weakness that has undergone repeated reactivation. It shows itself as the narrow zone of anticlinally folded and locally overthrusted Silurian rocks forming the Abberley Hills. To the west of the Axis a Precambrian basement is overlain unconformably by a cover of Lower Palaeozoic rocks in which the dominant structures are horizontal and synclinal strata with some north north-west trending faults.

Geophysical surveys suggest that the basement rocks lie at between 1500m and 2000m below the surface. The overlying Silurian sequence of Llandovery through to Pridoli dips steeply away to the west. The Lower Devonian is less affected and in places is near horizontal. The Carboniferous rocks form a gentle syncline to the north-west the whole resting unconformable on Silurian and Devonian strata. But to the east the Malvern Axis shows itself as north south structures with westerly directed thrusting producing the thrusts of Ankerdine Hill and others to the north. It is also present as a western boundary fault alongside the southern parts of the Abberley Hills but is absent around Abberley Hill itself.

All of this complex structure is the result of the collision of the Avalonian and Laurentian continents as the Iapetus Ocean closed at the end of the Lower Palaeozoic. This marked the onset of the continental red beds of the Old Red Sandstone during the Pridoli as the Acadian Orogeny got underway. An extensive period of mountain building and continental deposition was followed by erosion until the coal measure swamps of the Carboniferous occurred. It is likely that late Carboniferous strata were deposited over much of the area but some subsequently underwent erosion during the Variscan Orogeny. It is this tectonic episode that resulted in the Malvernoid and Charnoid structural patterns.

Some of the youngest rocks represented in the area are the Highley Beds of the Coal Measures. They are involved in the severe Variscan folding to the west of Walsgrove Hill where they are tightly folded along with the underlying Silurian strata. This late Carboniferous tectonic activity resulted in the Cockshot, Rodge Hill and Penny Hill Thrusts and the overfolding of the Carboniferous, Devonian and Silurian strata that outcrop form the line of the Abberley Hills westwards to the River Teme.

The steeply dipping limbs of the synclinal structure described above give way to a very different picture to the west of the River Teme. Here the Raglan Mudstone Formation and the overlying St Maughans Formation are nearly horizontal as the western limb of the syncline flattens out. The change in steepness of dip and tightness of fold could not be more obvious as the influence of the Malvern Axis wanes away from the Hills of Walsgrove, Woodbury, Berrow and Ankerdine. But to the north-west of the area the Upper Silurian/Lower Devonian mudstones and sandstones begin to dip steeply towards the Cleobury Mortimer syncline.

The folded strata described are unconformably overlain by the horizontal beds of the Permian Haffield Breccia on Woodbury and Abberley Hills. There is no evidence of similar rocks to the west or north of the Teme valley.

Economic Geology

Historically, the breccia of Osebury Rock was used for road surfaces. More recently and to a greater extent, the Brockhill dolerite dyke has been extracted for road metal aggregates. The Bishops Frome Limestone and cornstones of the St Maughans Formation also have been used for this purpose. There has been local use of the Teme Valley river gravels as farm road surface but they are limited deposits and no great extraction has taken place.

The mudstones of both the St Maughans Formation and Raglan Mudstone Formation have been used on a small scale historically for brick making as they have in other areas of the county. However the sandy nature of the beds makes them less than ideal for this purpose.

The calcareous tufa can be seen as building stones in Shelsley Walsh Church and gatehouse and elsewhere in walls around the area. Because of its free carving properties and lightness the stone has also been used in the vaulting of the transepts of Worcester Cathedral.

The Bishops Frome Limestone was formerly worked for lime burning as indicated through the remains of lime kilns along the Sapey Brook. The Limestone has been extensively dug in some areas and this may have been for lime burning or aggregates.

The Aymestry Limestone at Woodbury Quarry was used for the aggregates industry. Operations ceased at this quarry in December 2000.

Agriculturally the land to the east of the River Teme is very productive and has sustained hop growing in an almost continuous fashion with no rotation. Cherry and apple orchards are common on the Ragland Mudstone Formation making use of the less easily ploughed undulating hillsides.

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