The geology of Cheshire in

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

consists mainly of

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s and mudstones. To the north west of Cheshire, these rocks are heavily faulted and the underlying Carboniferous Coal Measures are thrown up. Around the areas of

Poynton Poynton is a town in Cheshire, England, on the easternmost fringe of the Cheshire Plain, south-east of Manchester, north of Macclesfield and south of Stockport. Poynton has formed part of the Cheshire East unitary authority since the ab ...

and Macclesfield, the coal is close to the surface and was easily mined. Below the Coal Measures is the Millstone Grit, which appears towards the

Derbyshire Derbyshire ( ) is a ceremonial county in the East Midlands, England. It includes much of the Peak District National Park, the southern end of the Pennine range of hills and part of the National Forest. It borders Greater Manchester to the nor ...

border on the flanks of the

Peak District The Peak District is an upland area in England at the southern end of the Pennines. Mostly in Derbyshire, it extends into Cheshire, Greater Manchester, Staffordshire, West Yorkshire and South Yorkshire. It includes the Dark Peak, where moorla ...

dome. The

Cheshire Basin The Cheshire Basin is a late Palaeozoic and Mesozoic sedimentary basin extending under most of the county of Cheshire in northwest England. It extends northwards into the Manchester area and south into Shropshire. The basin possesses something of t ...

is a major

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subside ...

which comprises the larger part of the county. This fault-bounded half-graben structure is bounded to the east and southeast by a series of faults of which the most significant is the Red Rock Fault. Numerous faults trend north-south through the basin, some of which help to define the series of hills which are known collectively as the Mid Cheshire Ridge. The basin was flooded on several occasions in the

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last ...

and early Triassic periods resulting in the laying down of massive

halite Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...

(salt) beds. These beds have been mined both by cavern working and hot water brine extraction for over 200 years, mainly in the area around Northwich. The collapse of some of these worked-out halite beds has given rise to some of Cheshire's noted features, the Cheshire Meres.

Carboniferous

Rocks originating in the Carboniferous period are largely restricted to that part of the county to the east of the Red Rock Fault. They comprise mudstones, siltstones and sandstones of the Lower Coal Measures and of the Millstone Grit Group. A very small outcrop of

Carboniferous Limestone Carboniferous Limestone is a collective term for the succession of limestones occurring widely throughout Great Britain and Ireland that were deposited during the Dinantian epoch (geology), Epoch of the Carboniferous period (geology), Period. T ...

formerly occurred near

Astbury Astbury is a surname. Notable people with the surname include: * Andrew Astbury, English swimmer * Ian Astbury, English rock singer * Jill Astbury, Australian researcher into violence against women * William Astbury, English physicist and molecular ...

though this has largely been removed by quarrying. Coal Measures strata also occurs in the

Neston Neston is a town and civil parish on the Wirral Peninsula, in Cheshire, England. It is part of the unitary authority of Cheshire West and Chester. The village of Parkgate is located to the north west and the villages of Little Neston and Nes ...

area though it is obscured by glacial till and estuarine alluvium. It represents the easternmost extent of the Flintshire Coalfield. An inlier of upper Carboniferous rocks occurs to the south of Chester though it too is obscured by superficial deposits. Carboniferous strata underlies the entire Cheshire basin at depth.

Permo–Triassic

The majority of the solid rocks of Cheshire are sedimentary rocks laid down during the

and

periods. Both the east and west

Cheshire Plain The Cheshire Plain is a relatively flat expanse of lowland within the county of Cheshire in North West England but extending south into Shropshire. It extends from the Mersey Valley in the north to the Shropshire Hills in the south, bounded b ...

s are immediately underlain by Triassic sandstones, siltstones and mudstones, although outcrops are restricted to those areas that are not covered by thick expanses of glacial till of glacio-fluvial sands and gravels, such as the Mid Cheshire Ridge and

Alderley Edge Alderley Edge is a village and civil parish in Cheshire, England. In 2011, it had a population of 4,780. Alderley Edge is northwest of Macclesfield and south of Manchester, at the base of a steep and thickly wooded sandstone escarpment, Alder ...

. Rocks of Permian age occur to the west of Chester and in restricted areas to the southeast and northeast of the city, although again largely obscured by superficial deposits.

Jurassic

Small areas of the extreme south of the county are underlain by rocks of

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

age. Outcrops are very scarce as the thick cover of

glacial till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

in this area largely obscures the underlying bedrock. The strata are assigned to the lowermost Jurassic

Lias Group The Lias Group or Lias is a lithostratigraphic unit (a sequence of rock strata) found in a large area of western Europe, including the British Isles, the North Sea, the Low Countries and the north of Germany. It consists of marine limestones, sh ...

comprising mudstones and limestones.

Quaternary

The larger part of the

is covered by a thick mantle of

and sands and gravels of glacio-fluvial origin. These deposits are the legacy of the over-riding of the area on several occasions by glacial ice during the past 2 million years. The present distribution of deposits and the landforms to which they give rise are largely the result of the last

ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...

, the Devensian which peaked around 22-20,000 years ago.

Kettle hole A kettle (also known as a kettle lake, kettle hole, or pothole) is a depression/hole in an outwash plain formed by retreating glaciers or draining floodwaters. The kettles are formed as a result of blocks of dead ice left behind by retreating gla ...

s caused by the in-situ melting of ice-blocks during deglaciation are a notable feature of the landscape. Many are now dry though others such as Hatchmere and Pettypool remain as locally significant waterbodies. The morphology of both the Dee and

Mersey The River Mersey () is in North West England. Its name derives from Old English and means "boundary river", possibly referring to its having been a border between the ancient kingdoms of Mercia and Northumbria. For centuries it has formed part ...

estuaries is in large part owed to the passage of Irish Sea Ice southwestwards over the relatively soft sandstones of the area. These features have been termed iceways. There are also a number of

tunnel valley A tunnel valley is a U-shaped valley originally cut under the glacial ice near the margin of continental ice sheets such as that now covering Antarctica and formerly covering portions of all continents during past glacial ages. They can be as l ...

s beneath modern river valleys and other parts of the plain, excavated by ice and meltwater. Striking examples underlie the lower and middle stretches of the Weaver valley and those of the Dee and Gowy near Chester. A considerable number of small glacial meltwater channels have been identified along the Mid Cheshire Ridge such as that known as Urchin's Kitchen near

Kelsall Kelsall is a village and civil parish in the unitary authority of Cheshire West and Chester and the ceremonial county of Cheshire, England. It is located around east of Chester, west of Northwich and north west of Tarporley. The village is s ...

whilst larger examples occur along the edges of the

. There are notable examples at

Lyme Park Lyme Park is a large estate south of Disley, Cheshire, England, managed by the National Trust and consisting of a mansion house surrounded by formal gardens and a deer park in the Peak District National Park. The house is the largest in Ches ...

and southwards to

Bollington Bollington is a town and civil parish in Cheshire, England, to the east of Prestbury. In the Middle Ages, it was part of the Earl of Chester's manor of Macclesfield and the ancient parish of Prestbury. In 2011, it had a population of 8,310. ...

and again in the

Bosley Bosley is a village and civil parish in Cheshire, England. At the 2001 census, it had a population of 406.Macclesfield. The floodplains of the majority of watercourses in the county are composed of

alluvium Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. ...

which has accumulated in the post-glacial period.

River terrace Fluvial terraces are elongated terraces that flank the sides of floodplains and fluvial valleys all over the world. They consist of a relatively level strip of land, called a "tread", separated from either an adjacent floodplain, other fluvial te ...

s can be identified along some valleys such as those of the

River Mersey The River Mersey () is in North West England. Its name derives from Old English and means "boundary river", possibly referring to its having been a border between the ancient kingdoms of Mercia and Northumbria. For centuries it has formed par ...

and River Dane, reflecting changing base levels to which these rivers have been cutting down. Peat deposits have accumulated in various of the kettle-holes, not least within

Delamere Forest Delamere Forest is a large wood in the village of Delamere in Cheshire, England. The woodland, which is managed by Forestry England, covers an area of making it the largest area of woodland in the county. It contains a mixture of deciduous and ...

, and on parts of the high ground of the east of the county where thin soils and high rainfall have contributed to their formation.British Geological Survey 1:50K map series sheets 96-98, 108-110, 122,123 and accompanying memoirs

References

{{Cheshire

Carboniferous

Permo–Triassic

Jurassic

Quaternary

See also

References