Cheshire Basin
Encyclopedia
The Cheshire Basin is a late Palaeozoic and Mesozoic
sedimentary basin
which extends 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 the character of a half-graben
as its deepest extent is along its eastern and southeastern margins where it is well-defined by a series of sub-parallel faults, most important of which is the Red Rock Fault
. These faults divide the basin from the older Carboniferous
rocks of the Peak District
and the North Staffordshire Coalfield
.
In terms of its architecture, the basin is sometimes considered to be divided into two sub-basins - the more southerly Wem-Audlem Sub-basin and the Sandbach-Knutsford Sub-basin to its northeast.
The basin fill is mainly Permian
and Triassic
sandstone
s and mudstone
s though also incorporating economically important halite
beds. An isolated outlier of Jurassic
rocks occurs within the basin at Prees in north Shropshire.
The basin is just one part of a wider complex of basins which include the Worcester Graben, the Stafford Basin and the East Irish Sea Basin, the development of each of which began whilst the crust
of this region was experiencing east-west tension during the Permian period. It is traversed by a series of largely north-south aligned normal faults, some of which help to define the Mid Cheshire Ridge
and Alderley Edge
, two upstanding areas within the Cheshire Plain
.
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
sedimentary basin
Sedimentary basin
The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification...
which extends under most of the county of Cheshire
Cheshire
Cheshire is a ceremonial county in North West England. Cheshire's county town is the city of Chester, although its largest town is Warrington. Other major towns include Widnes, Congleton, Crewe, Ellesmere Port, Runcorn, Macclesfield, Winsford, Northwich, and Wilmslow...
in northwest England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. It extends northwards into the Manchester
Manchester
Manchester is a city and metropolitan borough in Greater Manchester, England. According to the Office for National Statistics, the 2010 mid-year population estimate for Manchester was 498,800. Manchester lies within one of the UK's largest metropolitan areas, the metropolitan county of Greater...
area and south into Shropshire
Shropshire
Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...
. The basin possesses something of the character of a half-graben
Graben
In geology, a graben is a depressed block of land bordered by parallel faults. Graben is German for ditch. Graben is used for both the singular and plural....
as its deepest extent is along its eastern and southeastern margins where it is well-defined by a series of sub-parallel faults, most important of which is the Red Rock Fault
Wem-Bridgemere-Red Rock Fault System
The Wem-Bridgemere-Red Rock Fault System is a complex zone of intersecting faults which defines the eastern boundary of the Cheshire Basin, a deep sedimentary basin in the northwest of England and extending south into the northern Midlands...
. These faults divide the basin from the older Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
rocks of the Peak District
Peak District
The Peak District is an upland area in central and northern England, lying mainly in northern Derbyshire, but also covering parts of Cheshire, Greater Manchester, Staffordshire, and South and West Yorkshire....
and the North Staffordshire Coalfield
North Staffordshire Coalfield
- Introduction :The North Staffordshire Coalfield is an historic coalfield in the County of Staffordshire, England. The Coalfield emcompasses an area of nearly and that area is virtually wholly contained within the boundaries of the city of Stoke on Trent and the borough of Newcastle under Lyme...
.
In terms of its architecture, the basin is sometimes considered to be divided into two sub-basins - the more southerly Wem-Audlem Sub-basin and the Sandbach-Knutsford Sub-basin to its northeast.
The basin fill is mainly Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
and Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s and mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
s though also incorporating economically important halite
Halite
Halite , commonly known as rock salt, is the mineral form of sodium chloride . Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pink, red, orange, yellow or gray depending on the amount and type of impurities...
beds. An isolated outlier of Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
rocks occurs within the basin at Prees in north Shropshire.
The basin is just one part of a wider complex of basins which include the Worcester Graben, the Stafford Basin and the East Irish Sea Basin, the development of each of which began whilst the crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
of this region was experiencing east-west tension during the Permian period. It is traversed by a series of largely north-south aligned normal faults, some of which help to define the Mid Cheshire Ridge
Mid Cheshire Ridge
The Mid Cheshire Ridge is a range of low sandstone hills which stretch north to south through Cheshire in North West England. The ridge is discontinuous, with the hills forming two main blocks, north and south of the "Beeston Gap"...
and Alderley Edge
Alderley Edge
Alderley Edge is a village and civil parish within the unitary authority of Cheshire East and the ceremonial county of Cheshire, England. According to the 2001 census the parish had a population of 4,409....
, two upstanding areas within the Cheshire Plain
Cheshire Plain
The Cheshire Plain is a relatively flat expanse of lowland situated almost entirely within the county of Cheshire in northwest England. It is bounded by the hills of North Wales to the west, and the Peak District of Derbyshire and North Staffordshire to the east and southeast...
.