15 - Durham Magnesian Limestone Plateau : Description

Physical and functional links to other National Character Areas

A striking, west-facing Magnesian Limestone escarpment forms a series of spurs and valleys which mark the western boundary of the National Character Area (NCA), and overlooks the Tyne and Wear Lowlands to the north and west, affording dramatic views of the City of Durham. The plateau drops gradually to the Tees Lowlands to the south and the Durham Coalfield Pennine Fringe to the south-west. Transport routes such as the A19 and the coastal railway form prominent features in the landscape and provide links to the north and south, but also detract from tranquillity and create physical and psychological barriers to public access.

The NCA’s two main rivers connect it to surrounding NCAs. The River Wear rises from the high moorland of the North Pennines and flows through the Durham Coalfield Pennine Fringe and Tyne and Wear Lowlands before crossing the Durham Magnesian Limestone Plateau to drain into the North Sea at Sunderland. Water for domestic use is abstracted from the tributaries of the River Wear upstream of the NCA, and pollution from disused mines and spoil heaps in the Durham Coalfield Pennine Fringe and North Pennines affects the water quality. The River Skerne rises within the Durham Coalfield Pennine Fringe near Trimdon and then flows south to the Tees Lowlands where it joins the River Tees. The Wear Magnesian Limestone Groundwater body, which underlies the area, supplies drinking water for Hartlepool, and is an important source of water for other areas.

A number of migratory species are associated with the coast and the sea to the east of the NCA, providing functional links to much further afield. The coast provides winter feeding grounds for large numbers of wading birds, many of which are migratory. The River Wear is also an important route for salmon and sea trout passing through the area en route between the North Sea and spawning grounds in rivers upstream of the NCA.

There are commercial links with the sea and other areas along the coast, particularly through traffic into and out of Sunderland, Seaham and the deep water port at Hartlepool, for freight, fisheries and services for offshore industry. Hartlepool, on the very southern edge of the area, has increasing links with the offshore wind energy sector, through manufacture of parts for wind turbines and transport services.

The Durham Magnesian Limestone Plateau today

The Durham Magnesian Limestone Plateau forms a gently undulating plateau of large, open arable fields, with low hedges and few trees. It has dramatic, well-defined boundaries in the form of a steep limestone escarpment to the west and the coastline to the east. The escarpment rises to 193 m and is dissected by streams which have carved it into a series of incised valleys where broadleaved woodland, scrub and species-rich grasslands survive on uncultivated steep slopes. The coast is made up of limestone and boulder clay, eroded to form a series of cliffs, headlands and bays, peppered with sea caves and isolated sea stacks. The dominant streams of the area drain eastwards down the gently inclined slope of the Magnesian Limestone towards the North Sea. Short streams run off the escarpment westwards as tributaries of the River Wear. Streams from the southern part of the plateau drain south into the River Skerne.

The area has long been important for agriculture, and is now predominantly farmed for arable crops, interspersed with grassland for livestock production. Field patterns are a mixture of smaller 17th-century fields around villages, the escarpment and the coast, all subject to some enlargement and reorganisation, and large, regular ‘surveyor enclosed’ fields (mostly from around the 18th century) on the central clay plateau. Coal mining and limestone quarrying have had a big impact on the landscape. Although the last of the deep coal pits were closed in the 1990s, coal mining still plays a strong role within local culture and identity. The area was also once important for its sea fisheries, with fishing ports along the coast.

Habitats of high conservation importance include the Magnesian Limestone grassland which exists in small, isolated fragments, with concentrations along the western escarpment, the coast and the central area around Thrislington Plantation and Cassop Vale. It supports a unique assemblage of species at the northern and southern extent of their natural range, and many rare species such as bird’s-eye primrose, dark red helleborine and orchid species (pyramidal, fragrant and bee orchids). Pockets of ancient ash and elm woodland survive in parkland, country estates, the River Wear Valley and coastal denes, such as Castle Eden Dene (a National Nature Reserve and popular recreation destination). The mixture of arable land and grassland supports breeding populations of farmland birds such as grey partridge and corn bunting. Water voles are present along some of the watercourses in the area, and the River Wear has a healthy population of salmon and sea trout. The coast provides feeding grounds for large numbers of wading birds and breeding grounds for little tern, as well as habitat for numerous other marine and littoral species.

The northern part of the plateau has a strong urban character, influenced by Sunderland and South Shields, larger former mining towns such as Easington, and the planned modern ‘New Town’ of Peterlee, where the colour and texture of the buildings reflect the influence of artist Victor Pasmore. Further south, former mining villages dominate the landscape with their Victorian terraces of red brick and Welsh slate. The villages have a distinctive industrial urban character, and are surrounded by features such as small pony paddocks, allotments and sheds. The plateau also has traditional stone-built villages clustered around village greens which formerly provided grazing and protection for livestock. Railway lines, the A19 corridor, and other infrastructure such as landfill sites, light industry and warehouses give an urban feel to many parts of the NCA.

Use of the area for access and recreation is primarily by local residents, although this may change with restoration of the coast and the creation of the England Coast Path. The area is well provided with nature reserves and access routes near residential areas, many of which are associated with reclaimed colliery sites and former mine railways. Disused railways and other cycle routes form good connections between settlements and enable commuting by bike. Poor crossing routes across major roads and railways still act as physical and psychological barriers in the access network. There are some key sites which offer a strong sense of tranquillity and inspiration, such as the coast and the denes. The cultural significance attached to parts of the coast has been recognised through its designation as a Heritage Coast.

The landscape through time

The landscape of the area is defined by its underlying geology, most notably the Magnesian Limestone and overlying boulder clay. The Magnesian Limestone was deposited during the Permian, approximately 255 million years ago, when the area was on the margins of a shallow sea, known as the Zechstein Sea, which then covered much of northern Europe. The Permian climate was hot and arid, similar to the modern-day Sahara, and beneath the Magnesian Limestone lie yellow desert sands (quarried in places such as Sherburn Hill). As sea levels rose, the Permian deserts were inundated. Initially the Marl Slate, rich in fish fossils, was deposited and then the thick sequence of Magnesian Limestone. Magnesian Limestones of Permian age which underlay the area are a complex succession of calcium and magnesium carbonates with important fossil reef structures which developed around the margins of the Zechstein Sea.

The Permian Magnesian Limestone overlies Carboniferous Coal Measures rocks (around 310 million years old). Glaciations shaped the landscape into the one we see today. The last, late Devensian, glaciation 26,000 to 10,000 years ago removed nearly all evidence of earlier glaciations and scraped bare the western Magnesian Limestone escarpment. The ice sheet deposited layers of till (boulder clay) across the area, burying earlier river valleys. When the 500-metre-thick ice sheet melted new valleys were cut, including the Wear gorge at Sunderland and the denes that run down to the Durham coast. Tundra vegetation, of grasses, sedges, club mosses and herbaceous plants, gradually became established on the barren glacial landscape and was followed by an expansion of mixed deciduous woodland as the climate warmed. The sea level rose as the ice sheets melted, eroding the cliffs that now form the Durham coast. The coastal exposures reveal the most complete succession of Magnesian Limestone in the British Isles and are of international importance (Limestone Landscapes – a geodiversity audit and action plan for the Durham Magnesian Plateau, British Geological Survey Open Report OR/09/007, DJD Lawrence, 2009), (Durham Geodiversity Audit, DJD Lawrence, CI Vye and B Young, British Geological Service, 2004).

Humans probably migrated into the area in Mesolithic times (8,000 to 4,000 BC) but left marks on the landscape that are visible today only from the Iron Age (750 BC to 75 AD) when forest clearance for agriculture began. The limestone plateau has a high concentration of prehistoric barrows and cairns (such as Copt Hill and Warden Law barrows), and the coastal area is rich in remains from Mesolithic and Neolithic activity. There is also an important body of data relating to palaeo-environmental conditions in the southern part of this area in the interface with the Carr lands.

The area was well used during medieval times for agriculture, commerce and manufacture. Much of it was owned by the medieval Benedictine monastery at Durham and by the ‘prince bishops’, who between them controlled all of the land ‘between Tyne and Tees’. Medieval settlements were essentially nucleated and planned villages, dating from the 12th and 13th centuries. Medieval agriculture was mixed, producing grain and cattle for the monastic estates, and farmsteads developed from the 15th century on estates.

Post-medieval enclosure and re-organisation resulted in a large number of deserted medieval settlements, large, regular field patterns and very low survival of pre-1750 farmsteads. The remaining commons and pastures were enclosed in the 18th century. Many of the linear farmsteads from the late 17th century and loose and regular courtyard farmsteads from the late 18th and 19th centuries still survive today.

The rich mineral wealth of the area has been exploited for many years, and continues to be in the case of a small number of active quarries for limestone and sand. The quarrying of limestone expanded rapidly in the late 18th century, for use in agriculture, construction, steel making and pharmaceuticals. The now-disused quarries are important for their geological exposures and have been colonised by a typical limestone flora. The underlying geology and glacial clays of the area supported the manufacture of glass and bricks (from laminated glacial clays at sites such as Birtley). The glacially deepened River Wear provided an ideal deep water channel for ship building in Sunderland, once reputed to be the biggest ship-building centre in the world.

The Carboniferous Coal Measures underlying the limestone yielded poor quality gas and coking coal which was used by early steel and engineering industries. In the 19th century workers’ villages sprang up next to the expanding collieries. The Durham Coast railway line, which runs north-south, was constructed to transport coal from the coastal mines. It has since formed a physical barrier which has limited the encroachment of built development onto the coastal landscape.

In the 1940s the planned ‘New Towns’ of Peterlee and Newton Aycliffe were built. The closure of the coal mines in the 1980s and 1990s was followed by the removal of the distinctive colliery structures and the reclamation and environmental improvement of former colliery sites for new housing, mixed use development and green space. Despite the closure of all the pits in the area, mining is still important to the sense of identity in the former colliery towns and villages. The decline of the local fishing industry had a significant influence on the landscape and economy of places such as Sunderland, Seaham and Hartlepool. The fishing industry in the area has been in decline since the 1980s and 1990s partly as a result of collapses in North Sea fish stocks. The decline of ship building was also a serious blow to the economy and community of Sunderland, and influenced the landscape.

Other changes in the 20th century included increases in field size and removal of hedgerows, the introduction of new crops such as oilseed rape, the decline of elm trees through Dutch elm disease, and the introduction of new features such as overhead power lines, telecommunication masts and wind turbines. The end of the 20th century saw an expansion in transport and commercial development.

At the beginning of the 21st century development continued (urban expansion and infilling around Sunderland, Peterlee and Hartlepool and along the A182). There has been some woodland expansion and restoration of hedgerows. Arguably the most dramatic change to the landscape in the early 21st century was the clearing of 1.3 million tonnes of colliery waste from the coast by the Turning the Tide project. This was accompanied by other work along the coast to return large areas (around 250 ha) of arable and brownfield sites to semi-natural grassland and create new coastal access routes.