Northern England district - North Pennines and the Northumberland-Durham Coalfield: Difference between revisions

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The central and eastern parts of the region comprise the North Pennines and the lower lying and coastal areas of the Northumberland and Durham Coalfield. The Pennines are predominantly rural but the coalfield area is densely populated with Newcastle-upon-Tyne, Sunderland, Durham, Stockton-on-Tees and Darlington as the main urban centres.
The central and eastern parts of the region comprise the North Pennines and the lower lying and coastal areas of the Northumberland and Durham Coalfield. The Pennines are predominantly rural but the coalfield area is densely populated with Newcastle-upon-Tyne, Sunderland, Durham, Stockton-on-Tees and Darlington as the main urban centres.


===Sedimentary Bedrock===
===Sedimentary bedrock===
South of Hadrian’s Wall lie the high, flat moorlands of the North Pennines. The moors rise gently westward to the spectacular west-facing Pennine edge at Cross Fell that overlooks the Vale of Eden. A distinctive feature of the North Pennine landscape is the marked terraces on the hillsides (P689653) caused by erosion of the soft mudstone and alternating hard sandstone and limestone layers, all deposited between 340 and 300 million years ago.
South of Hadrian’s Wall lie the high, flat moorlands of the North Pennines. The moors rise gently westward to the spectacular west-facing Pennine edge at Cross Fell that overlooks the Vale of Eden. A distinctive feature of the North Pennine landscape is the marked terraces on the hillsides ('''Plate P689653''') caused by erosion of the soft mudstone and alternating hard sandstone and limestone layers, all deposited between 340 and 300 million years ago.


The Whin Sill is also present in this area, particularly in upper Teesdale, and farther eastwards it has been encountered within many old mines and in boreholes at depths increasing to 880 m on the North Sea coast. This sheet-like intrusion, described in more detail above, thickens from about 80 m north of upper Teesdale to about 100 m beneath Tynemouth where it splits into several layers. The rocks in this area, in particular the Whin Sill and harder limestone and sandstone beds, host a large number of veins of lead and zinc ore that formed the basis of the historic mining industry of this area.
The Whin Sill is also present in this area, particularly in upper Teesdale, and farther eastwards it has been encountered within many old mines and in boreholes at depths increasing to 880 m on the North Sea coast. This sheet-like intrusion, thickens from about 80 m north of upper Teesdale to about 100 m beneath Tynemouth where it splits into several layers. The rocks in this area, in particular the Whin Sill and harder limestone and sandstone beds, host a large number of veins of lead and zinc ore that formed the basis of the historic mining industry of this area.


Layers of mudstone, sandstone and coal belonging to the Coal Measures are more than 850 m thick in the Northumberland and Durham Coalfield (P220606). These rocks were formed in a tropical, humid and forested lowland swamp crossed by rivers and subjected to short-lived incursions by the sea. Most of the valuable coal seams are present in the middle part of the sequence, with the thickest of the individual seams reaching 2.5 m. This coalfield is the oldest area of commercial coal mining in Great Britain, with records of workings dating from the 12th century, and it provided the basis for the development of the steel and shipbuilding industries of Tyneside and Wearside. Mining extended offshore for up to 7.5 km and in coastal County Durham seams were mined at depths up to 500 m. Though only a handful of coal mines remain in operation today, and all base metal mining has now ceased in the region, the effects of mining remains a major influence on the landscape.
Layers of mudstone, sandstone and coal belonging to the Coal Measures are more than 850 m thick in the Northumberland and Durham Coalfield ('''Plate P220606'''). These rocks were formed in a tropical, humid and forested lowland swamp crossed by rivers and subjected to short-lived incursions by the sea. Most of the valuable coal seams are present in the middle part of the sequence, with the thickest of the individual seams reaching 2.5 m. This coalfield is the oldest area of commercial coal mining in Great Britain, with records of workings dating from the 12th century, and it provided the basis for the development of the steel and shipbuilding industries of Tyneside and Wearside. Mining extended offshore for up to 7.5 km and in coastal County Durham seams were mined at depths up to 500 m. Though only a handful of coal mines remain in operation today, and all base metal mining has now ceased in the region, the effects of mining remain a major influence on the landscape.


East from the city of Durham, the rocks of the Coalfield descend beneath successively younger sediment layers, absent in the northwest, which are intermediate in age between the Coal Measures and red sandstone of the Whitehaven coast. First is a layer of younger limestone, traditionally called the Magnesian Limestone, that is only present in this southeastern part of the region and was laid down about 270 to 250 million years ago. It is marked by a distinctive belt of arable country terminated by the limestone cliffs of the Durham coast. The Magnesian Limestone (P221294) forms a good quality aquifer though the waters are very hard, giving problems with limescale, and there is a high vulnerability to surface nitrate pollution from fertilisers used in the arable farming. Water yields depend largely on the density of fractures present and the extent of connection between them. At greater depths, water quality is poorer due to an increased concentration of dissolved mineral salts from the overlying layers.
East from the city of Durham, the rocks of the coalfield descend beneath successively younger sediment layers, absent in the north-west, which are intermediate in age between the Coal Measures and red sandstone of the Whitehaven coast. First is a layer of younger limestone, traditionally called the Magnesian Limestone, that is only present in this south-eastern part of the region and was laid down about 270 to 250 million years ago. It is marked by a distinctive belt of arable country terminated by the limestone cliffs of the Durham coast. The Magnesian Limestone ('''Plate P221294''') forms a good quality aquifer though the waters are very hard, giving problems with limescale, and there is a high vulnerability to surface nitrate pollution from fertilisers used in the arable farming. Water yields depend largely on the density of fractures present and the extent of connection between them. At greater depths, water quality is poorer due to an increased concentration of dissolved mineral salts from the overlying layers.


Southwards, the Magnesian Limestone is concealed by younger mudstone and thick beds of mineral salts, and then by the Sherwood Sandstone and brownish Mercia Mudstone. The mineral salts in these layers formerly supplied the chemical and other industries on Teesside.
Southwards, the Magnesian Limestone is concealed by younger mudstone and thick beds of mineral salts, and then by the Sherwood Sandstone and brownish Mercia Mudstone. The mineral salts in these layers formerly supplied the chemical and other industries on Teesside.

Revision as of 14:15, 6 October 2014

Terraced hillside in the Northern Pennines formed of harder Carboniferous sandstone and limestone with intervening mudstone, near Alston, Cumbria. P689653.
Alternating sandstone, mudstone and coal of the Coal Measures in a former opencast mine at Widdrington, Northumberland. P220606.
The Magnesian Limestone at Blackhall Rocks, north of Hartlepool, Co. Durham. P221294.

The central and eastern parts of the region comprise the North Pennines and the lower lying and coastal areas of the Northumberland and Durham Coalfield. The Pennines are predominantly rural but the coalfield area is densely populated with Newcastle-upon-Tyne, Sunderland, Durham, Stockton-on-Tees and Darlington as the main urban centres.

Sedimentary bedrock

South of Hadrian’s Wall lie the high, flat moorlands of the North Pennines. The moors rise gently westward to the spectacular west-facing Pennine edge at Cross Fell that overlooks the Vale of Eden. A distinctive feature of the North Pennine landscape is the marked terraces on the hillsides (Plate P689653) caused by erosion of the soft mudstone and alternating hard sandstone and limestone layers, all deposited between 340 and 300 million years ago.

The Whin Sill is also present in this area, particularly in upper Teesdale, and farther eastwards it has been encountered within many old mines and in boreholes at depths increasing to 880 m on the North Sea coast. This sheet-like intrusion, thickens from about 80 m north of upper Teesdale to about 100 m beneath Tynemouth where it splits into several layers. The rocks in this area, in particular the Whin Sill and harder limestone and sandstone beds, host a large number of veins of lead and zinc ore that formed the basis of the historic mining industry of this area.

Layers of mudstone, sandstone and coal belonging to the Coal Measures are more than 850 m thick in the Northumberland and Durham Coalfield (Plate P220606). These rocks were formed in a tropical, humid and forested lowland swamp crossed by rivers and subjected to short-lived incursions by the sea. Most of the valuable coal seams are present in the middle part of the sequence, with the thickest of the individual seams reaching 2.5 m. This coalfield is the oldest area of commercial coal mining in Great Britain, with records of workings dating from the 12th century, and it provided the basis for the development of the steel and shipbuilding industries of Tyneside and Wearside. Mining extended offshore for up to 7.5 km and in coastal County Durham seams were mined at depths up to 500 m. Though only a handful of coal mines remain in operation today, and all base metal mining has now ceased in the region, the effects of mining remain a major influence on the landscape.

East from the city of Durham, the rocks of the coalfield descend beneath successively younger sediment layers, absent in the north-west, which are intermediate in age between the Coal Measures and red sandstone of the Whitehaven coast. First is a layer of younger limestone, traditionally called the Magnesian Limestone, that is only present in this south-eastern part of the region and was laid down about 270 to 250 million years ago. It is marked by a distinctive belt of arable country terminated by the limestone cliffs of the Durham coast. The Magnesian Limestone (Plate P221294) forms a good quality aquifer though the waters are very hard, giving problems with limescale, and there is a high vulnerability to surface nitrate pollution from fertilisers used in the arable farming. Water yields depend largely on the density of fractures present and the extent of connection between them. At greater depths, water quality is poorer due to an increased concentration of dissolved mineral salts from the overlying layers.

Southwards, the Magnesian Limestone is concealed by younger mudstone and thick beds of mineral salts, and then by the Sherwood Sandstone and brownish Mercia Mudstone. The mineral salts in these layers formerly supplied the chemical and other industries on Teesside.

In the Teesside area, older sandstone and mudstone with variable amounts of limestone have also been proved below the Magnesian Limestone to extend to depths exceeding 4 km.

Basement rocks

In this area basement rocks are only found at the surface along the western edge of the Pennine Hills. These hard mudstones are of similar character to those seen in the northern Lake District and underlie the sedimentary bedrock that forms most of the moors. These older mudstones have also been found at depth in a few boreholes beneath the North Pennines. By contrast, in the Weardale area a large intrusion of granite, about 400 million years old, has been encountered in boreholes at 275 to 380 m beneath the surface. These basement rocks extend to depths exceeding 3 km underneath the whole area.