The Sherwood Sandstone Group is a

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

lithostratigraphic Lithostratigraphy is a sub-discipline of stratigraphy, the geology, geological science associated with the study of stratum, strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are ...

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic ide ...

(a sequence of

rock strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

) which is widespread in Britain, especially in the

English Midlands The Midlands (also referred to as Central England) are a part of England that broadly correspond to the Kingdom of Mercia of the Early Middle Ages, bordered by Wales, Northern England and Southern England. The Midlands were important in the Ind ...

. The name is derived from

Sherwood Forest Sherwood Forest is a royal forest in Nottinghamshire, England, famous because of its historic association with the legend of Robin Hood. The area has been wooded since the end of the Last Glacial Period (as attested by pollen sampling cores ...

Nottinghamshire Nottinghamshire (; abbreviated Notts.) is a landlocked county in the East Midlands region of England, bordering South Yorkshire to the north-west, Lincolnshire to the east, Leicestershire to the south, and Derbyshire to the west. The traditi ...

which is underlain by rocks of this age. It has economic importance as the reservoir of the

Morecambe Bay Morecambe Bay is a large estuary in northwest England, just to the south of the Lake District National Park. It is the largest expanse of intertidal mudflats and sand in the United Kingdom, covering a total area of . In 1974, the second larges ...

gas field, the second largest gas field in the UK.

Geographical extent

These rocks are found in northwest England as far north as

Carlisle Carlisle ( , ; from xcb, Caer Luel) is a city that lies within the Northern England, Northern English county of Cumbria, south of the Anglo-Scottish border, Scottish border at the confluence of the rivers River Eden, Cumbria, Eden, River C ...

(and extending just into

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

around Annan and Gretna) and in the

Vale of Eden The Vale of Eden is formed by the course of the River Eden, one of the major rivers of Northwest England. It is however of much greater extent than the actual valley of the river, lying between the Cumbrian Mountains (more usually referred to as ...

and then extending down the

Cumbria Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. Cumb ...

n coast into

Lancashire Lancashire ( , ; abbreviated Lancs) is the name of a historic county, ceremonial county, and non-metropolitan county in North West England. The boundaries of these three areas differ significantly. The non-metropolitan county of Lancashi ...

and

Cheshire Cheshire ( ) is a ceremonial and historic county in North West England, bordered by Wales to the west, Merseyside and Greater Manchester to the north, Derbyshire to the east, and Staffordshire and Shropshire to the south. Cheshire's county t ...

. They are mostly obscured by superficial deposits but the highest coastal cliffs in northwest England at

St Bees Head St Bees Head is a headland on the North West coast of the English county of Cumbria and is named after the nearby village of St Bees. It is the only stretch of Heritage Coast on the English coastline between the Welsh and Scottish borders, an ...

are formed in the St Bees Sandstone, the lowermost formation within the group. In the northeast they extend from

Hartlepool Hartlepool () is a seaside and port town in County Durham, England. It is the largest settlement and administrative centre of the Borough of Hartlepool. With an estimated population of 90,123, it is the second-largest settlement in County ...

south through the

Vale of Mowbray The Vale of Mowbray (sometimes mistakenly referred to as the Vale of York) is a stretch of low-lying land between the North York Moors and the Hambleton Hills to the east and the Yorkshire Dales to the west. To the north lie the Cleveland low ...

and the

Vale of York The Vale of York is an area of flat land in the northeast of England. The vale is a major agricultural area and serves as the main north–south transport corridor for Northern England. The Vale of York is often supposed to stretch from the R ...

, then south through

into the English Midlands, though are very largely concealed by superficial sediments. They occur widely through the Midlands (though usually concealed) and notably in an

outlier In statistics, an outlier is a data point that differs significantly from other observations. An outlier may be due to a variability in the measurement, an indication of novel data, or it may be the result of experimental error; the latter are ...

Leek, Staffordshire Leek is a market town and civil parishes in England, civil parish in the county of Staffordshire, England, on the River Churnet. It is situated about north east of Stoke-on-Trent. It is an ancient borough and was granted its royal charter in 1 ...

. They extend south to the

Severn Estuary The Severn Estuary ( cy, Aber Hafren) is the estuary of the River Severn, flowing into the Bristol Channel between South West England and South Wales. Its high tidal range, approximately , means that it has been at the centre of discussions in t ...

and beyond there through

Somerset ( en, All The People of Somerset) , locator_map = , coordinates = , region = South West England , established_date = Ancient , established_by = , preceded_by = , origin = , lord_lieutenant_office =Lord Lieutenant of Somerset , lord_ ...

Budleigh Salterton Budleigh Salterton is a seaside town on the coast in East Devon, England, south-east of Exeter. It lies within the East Devon Area of Outstanding Natural Beauty, and forms much of the electoral ward of Budleigh, whose ward population at t ...

on the coast of East

Devon Devon ( , historically known as Devonshire , ) is a ceremonial and non-metropolitan county in South West England. The most populous settlement in Devon is the city of Plymouth, followed by Devon's county town, the city of Exeter. Devon is ...

. There are further occurrences in

Northern Ireland Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...

north and east of

Limavady Limavady (; ) is a market town in County Londonderry, Northern Ireland, with Binevenagh as a backdrop. Lying east of Derry and southwest of Coleraine, Limavady had a population of 12,032 people at the United Kingdom census, 2011, 2011 Census ...

, east of

Cookstown Cookstown ( ga, An Chorr Chríochach, IPA: �anˠˈxoːɾˠɾˠˈçɾʲiːxəx is a small town in County Tyrone, Northern Ireland. It is the fourth largest town in the county and had a population of 11,599 in the 2011 census. It, along with Maghe ...

, between

Dungannon Dungannon () is a town in County Tyrone, Northern Ireland. It is the second-largest town in the county (after Omagh) and had a population of 14,340 at the 2011 Census. The Dungannon and South Tyrone Borough Council had its headquarters in the ...

and

Armagh Armagh ( ; ga, Ard Mhacha, , "Macha's height") is the county town of County Armagh and a city in Northern Ireland, as well as a civil parish. It is the ecclesiastical capital of Ireland – the seat of the Archbishops of Armagh, the Pri ...

and along the

Lagan Valley The Lagan Valley (, Ulster Scots: ''Glen Lagan'') is an area of Northern Ireland between Belfast and Lisburn. The River Lagan rises on Slieve Croob in County Down and flows generally northward discharging into Belfast Lough. For a section, the ...

beneath

Belfast Belfast ( , ; from ga, Béal Feirste , meaning 'mouth of the sand-bank ford') is the capital and largest city of Northern Ireland, standing on the banks of the River Lagan on the east coast. It is the 12th-largest city in the United Kingdo ...

and

Newtownards Newtownards is a town in County Down, Northern Ireland. It lies at the most northern tip of Strangford Lough, 10 miles (16 km) east of Belfast, on the Ards Peninsula. It is in the Civil parishes in Ireland, civil parish of Newtownard ...

and on the Antrim coast. The Group comprises different sequences in each of the various basins in which it is developed as described below.

Cheshire Basin rock succession

The sequence is most thickly developed in 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 ...

, which also extends into north Shropshire. It comprises the following formations:

Helsby Sandstone Formation

The Helsby Sandstone Formation (named from the Cheshire village of

Helsby Helsby is a village, civil parish and electoral ward in the unitary authority of Cheshire West and Chester and the ceremonial county of Cheshire, England. Overlooking the Mersey estuary, it is approximately north east of Chester and south we ...

where the type section is exposed at

Helsby Hill Helsby is a village, civil parish and electoral ward in the unitary authority of Cheshire West and Chester and the ceremonial county of Cheshire, England. Overlooking the Mersey estuary, it is approximately north east of Chester and south we ...

) comprises around 250m thickness of sandstone with conglomerate and siltstone which occurs across the Cheshire Basin. Older literature includes it as part of the Lower Keuper Sandstone. It is often divided into an upper ''Frodsham Member'' and a lower ''Delamere Member''.British Geological Survey 1:50,000 scale geological map sheet (England and Wales series) 96 ''Liverpool'' Faulted blocks of these rocks are largely responsible for the prominent west facing escarpment of the

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". The main mas ...

and the Helsby Sandstone is exposed in numerous localities here, southwards from

Runcorn Runcorn is an industrial town and cargo port in the Borough of Halton in Cheshire, England. Its population in 2011 was 61,789. The town is in the southeast of the Liverpool City Region, with Liverpool to the northwest across the River Mersey. ...

through

Frodsham Frodsham is a market town, civil parish, and electoral ward in the unitary authority of Cheshire West and Chester and the ceremonial county of Cheshire, England. Its population was 8,982 in 2001, increasing to 9,077 at the 2011 Census. It is s ...

Utkinton 200px, Map of civil parish of Utkinton within the former borough of Vale Royal Utkinton is a village and former civil parish, now in the parishes of Utkinton and Cotebrook and Tarporley, in the unitary authority of Cheshire West and Chester an ...

, spectacularly at the outlier of

Beeston Castle Beeston Castle is a former Royal castle in Beeston, Cheshire, England (), perched on a rocky sandstone crag above the Cheshire Plain. It was built in the 1220s by Ranulf de Blondeville, 6th Earl of Chester (1170–1232), on his return from th ...

hill and lastly within the

Peckforton Hills The Peckforton Hills are a sandstone ridge running broadly northeast–southwest in the west of the English county of Cheshire. They form a significant part of the longer Mid Cheshire Ridge which extends southwards from Frodsham towards Malpas. ...

Wilmslow Sandstone Formation

The Wilmslow Sandstone Formation (named from the town of

Wilmslow Wilmslow ( ) is a market town and civil parish in the unitary authority of Cheshire East in Cheshire, England, south of Manchester city centre. The population was 24,497 at the 2011 Census. History Toponymy Wilmslow derives its name from Old ...

in Cheshire) comprises up to 900m thickness of early Triassic sandstones with occasional siltstones. It was earlier known as the Upper Mottled Sandstone. In Wirral, the 60m thick ''Thurstaston Sandstone Member'' and the 2m thick ''Thurstaston Hard Sandstone Bed'' are distinguished at the top of the sequence.

Chester Pebble Beds Formation

The Chester Pebble Beds Formation (named from the city of

Chester Chester is a cathedral city and the county town of Cheshire, England. It is located on the River Dee, close to the English–Welsh border. With a population of 79,645 in 2011,"2011 Census results: People and Population Profile: Chester Loca ...

) comprises sandstones with some conglomerates and siltstones of early Triassic age. It ranges from less than 90m to over 220m in thickness. It has been known in the past as the Bunter Pebble Beds. There are a couple of reference sections for this sequence in the vicinity of Chester.

Kinnerton Sandstone Formation

The Kinnerton Sandstone Formation (named from the twin villages of Higher and Lower Kinnerton on the England/Wales border west of Chester) is a sequence which ranges from 0m to over 150m thickness of largely aeolian sandstones of early Triassic age. It was formerly known as the Lower Mottled Sandstone.

English Midlands rock succession

Bromsgrove Sandstone Formation

The Bromsgrove Sandstone Formation (named from the town of

Bromsgrove Bromsgrove is a town in Worcestershire, England, about northeast of Worcester and southwest of Birmingham city centre. It had a population of 29,237 in 2001 (39,644 in the wider Bromsgrove/Catshill urban area). Bromsgrove is the main town in the ...

in Worcestershire) is early Triassic to Anisian in age and comprises variously coloured sandstones whose bases are frequently conglomeratic, together with mudstones and siltstones. The thickness of the formation is variable but reaches around 500m in the Worcester area. It is often encountered in older literature as the Lower Keuper Sandstone. The formation includes the Shepshed Sandstone Member.

Wildmoor Sandstone Formation

The Wildmoor Sandstone Formation (named from the Worcestershire locality of Wildmoor, north of Bromsgrove) is a 0 - 284m thick sequence of sandstones formerly known as the Upper Mottled Sandstone or Wildmoor Beds. It also includes some mudstones and siltstones.

Kidderminster Formation

The Kidderminster Formation (named from the Worcestershire town of

Kidderminster Kidderminster is a large market and historic minster town and civil parish in Worcestershire, England, south-west of Birmingham and north of Worcester. Located north of the River Stour and east of the River Severn, in the 2011 census, it had ...

) is a 0 - 200m thick sequence of conglomerates and sandstones previously known as either the Bunter Pebble Beds or the Kidderminster Conglomerate Formation.

Polesworth Formation

The Polesworth Formation (named from the Warwickshire village of

Polesworth Polesworth is a large village and civil parishes in England, civil parish in the North Warwickshire district of Warwickshire, England. Polesworth is situated close to the northern tip of Warwickshire, adjacent to the border with Staffordshire. It ...

) is of ?Olenekian to Anisian age.

Moira Formation

The Moira Formation (named from the Leicestershire village of Moira) is of Induan/Olenekian age. Also encountered as the Hopwas or Moira Breccia.

Lenton Sandstone Formation

The Lenton Sandstone Formation (named from the Nottingham suburb of Lenton) is of Induan/Olenekian age.

Stafford Basin rock succession

The Stafford Basin includes the Kibbleston Formation (named from the Staffordshire locality of Kibbleston) which is underlain by the Wildmoor Formation which is in turn underlain by the Kidderminster Formation.British Geological Survey 1:50,000 scale geological map sheet (England and Wales series) 123 ''Stoke-on-Trent''

Needwood Basin rock succession

The rock succession in the Needwood Basin includes the Hollington Formation (named from the Staffordshire locality of Hollington) which is underlain by the Hawksmoor Formation (named from the Staffordshire locality of Hawksmoor) which includes the ''Hulme Member'', a conglomerate and which is in turn underlain by the Huntley Formation (named from the Staffordshire locality of Huntley). They are all of Scythian age.

Cumbria rock succession

On the Cumbrian coast the Group comprises the Calder Sandstone Formation and the underlying St Bees Sandstone Formation. The former is around 500m thick and includes sandstones of both aeolian and fluviatile origin. The latter is between 400 and 600m thick and includes some siltstone and claystone beds. It overlies the varied lithologies of the

Permian The Permian ( ) is a geologic period and 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 period of the Paleoz ...

age Cumbrian Coastal Group. The Kirklinton Sandstone Formation in places overlies the Calder Sandstone Formation in the Carlisle and Vale of Eden basins of north and east Cumbria. A sandstone which underlies

Sellafield Sellafield is a large multi-function nuclear site close to Seascale on the coast of Cumbria, England. As of August 2022, primary activities are nuclear waste processing and storage and nuclear decommissioning. Former activities included nucle ...

and

Drigg Drigg is a village situated in the civil parish of Drigg and Carleton on the West Cumbria coast of the Irish Sea and on the boundary of the Lake District National Park in the Borough of Copeland in the county of Cumbria, England. Drigg and C ...

is known as the Sellafield Member and is assigned to the Helsby Sandstone Formation.

Southwest England rock succession

The group is represented in Somerset and east Devon by the Otterton Sandstone and the underlying Budleigh Salterton Pebble Beds formations,.British Geological Survey 1:50,000 scale geological map (England) sheets 325, 326, 327 ''Exeter'', ''Sidmouth'' & ''Bridport''

References

{{Reflist, colwidth=35em Geological groups of the United Kingdom Geologic formations of England Geology of Nottinghamshire Sandstone formations Triassic England Triassic System of Europe Induan Stage Olenekian Stage Sherwood Forest