Geology of Norfolk

Last updated

The geology of Norfolk in eastern England largely consists of late Mesozoic and Cenozoic sedimentary rocks of marine origin covered by an extensive spread of unconsolidated recent deposits. [1]

Contents

Jurassic

The oldest rocks at or near the surface in Norfolk are late Jurassic mudstones and muddy limestones which underlie recent deposits in the area west of King's Lynn and Downham Market.

Cretaceous

Overlying the Jurassic is a Cretaceous sequence whose lowermost unit is the Wealden Group comprising mudstones, limestones, siltstones and sandstones and which extends in a band from Hunstanton southwards to south of the village of Southery. A narrow band of sandstone immediately east of this constitutes the Lower Greensand Group and beyond this, and stratigraphically above it, lie the mudstones and sandstones of the Gault and Upper Greensand formations.

The Grey Chalk and the White Chalk subgroups and the Hunstanton Formation overlie the Greensand. The Chalk extends across the rest of Norfolk east of a wavering line from Holme-next-the-Sea on the north coast to Hockwold cum Wilton on the Suffolk border though it is concealed beneath later Neogene sediments in the east.

Palaeogene

The Palaeogene Period is represented by a small area of Eocene clay assigned to the Thames Group which is recorded in the vicinity of Loddon.

Neogene

The shelly sand, clay and gravel deposits known locally as 'crag' cover the eastern part of the county. The western 'feather edge' of the crag is mapped south from the coast west of Sheringham through Cawston and Norwich to the Suffolk border east of Diss. The sequence is divided into the Red Crag, Norwich Crag and Wroxham Crag formations. Some of the youngest rocks in Britain, these are of Pliocene to Pleistocene age.

Structure

A granite pluton associated with the Acadian orogeny is inferred to exist beneath central and western Norfolk. [2]

Quaternary

The larger part of Norfolk's bedrock geology is concealed beneath superficial deposits, the oldest of which is a spread of glacial till dating from the Anglian glaciation. Interspersed with the till are sheets of glacial sands and gravels. The fact that the Chalk scarp in East Anglia is much reduced in height compared to its outcrop in Lincolnshire and the Chiltern Hills has been put down to erosion by the Anglian icesheet which reached as far south as Essex. [3] The late Devensian glaciation resulted in the North Sea icesheet impinging upon the north coast of Norfolk. Of more recent origin are alluvial deposits which extend across the floors of the main river valleys and widely across the flats of the Broads. Coastal alluvium is also present along the north coast from Holme-next-the-Sea to Brancaster. River terrace deposits occur in places, for example around the valley of the River Waveney. Blown sand characterises the lower sections of coast. Peat is widespread in the fenland areas south and west of Downham Market. [4]

See also

Further reading

Related Research Articles

Geology of Great Britain Overview of the geology of Great Britain

The geology of Great Britain is renowned for its diversity. As a result of its eventful geological history, Great Britain shows a rich variety of landscapes across the constituent countries of England, Wales and Scotland. Rocks of almost all geological ages are represented at outcrop, from the Archaean onwards.

The Howgill Fells are hills in Northern England between the Lake District and the Yorkshire Dales, lying roughly in between the vertices of a triangle made by the towns of Sedbergh, Kirkby Stephen and Tebay. The name Howgill derives from the Old Norse word haugr meaning a hill or barrow, plus gil meaning a narrow valley.

Geology of England

The geology of England is mainly sedimentary. The youngest rocks are in the south east around London, progressing in age in a north westerly direction. The Tees-Exe line marks the division between younger, softer and low-lying rocks in the south east and the generally older and harder rocks of the north and west which give rise to higher relief in those regions. The geology of England is recognisable in the landscape of its counties, the building materials of its towns and its regional extractive industries.

Geology of Wales

The geology of Wales is complex and varied; its study has been of considerable historical significance in the development of geology as a science. All geological periods from the Cryogenian to the Jurassic are represented at outcrop, whilst younger sedimentary rocks occur beneath the seas immediately off the Welsh coast. The effects of two mountain-building episodes have left their mark in the faulting and folding of much of the Palaeozoic rock sequence. Superficial deposits and landforms created during the present Quaternary period by water and ice are also plentiful and contribute to a remarkably diverse landscape of mountains, hills and coastal plains.

London Basin

The London Basin is an elongated, roughly triangular sedimentary basin approximately 250 kilometres (160 mi) long which underlies London and a large area of south east England, south eastern East Anglia and the adjacent North Sea. The basin formed as a result of compressional tectonics related to the Alpine orogeny during the Palaeogene period and was mainly active between 40 and 60 million years ago.

Geology of East Sussex Overview of the geology of East Sussex

The geology of East Sussex is defined by the Weald–Artois anticline, a 60 kilometres (37 mi) wide and 100 kilometres (62 mi) long fold within which caused the arching up of the chalk into a broad dome within the middle Miocene, which has subsequently been eroded to reveal a lower Cretaceous to Upper Jurassic stratigraphy. East Sussex is best known geologically for the identification of the first dinosaur by Gideon Mantell, near Cuckfield, to the famous hoax of the Piltdown man near Uckfield.

The geology of Suffolk in eastern England largely consists of a rolling chalk plain overlain in the east by Neogene clays, sands and gravels and isolated areas of Palaeocene sands. A variety of superficial deposits originating in the last couple of million years overlie this 'solid geology'.

The geology of Cambridgeshire in eastern England largely consists of unconsolidated Quaternary sediments such as marine and estuarine alluvium and peat overlying deeply buried Jurassic and Cretaceous age sedimentary rocks.

The geology of Essex in southeast England largely consists of Cenozoic marine sediments from the Palaeogene and Neogene periods overlain by a suite of superficial deposits of Quaternary age.

The geology of Kent in southeast England largely consists of a succession of northward dipping late Mesozoic and Cenozoic sedimentary rocks overlain by a suite of unconsolidated deposits of more recent origin.

The geology of Rutland in eastern England largely consists of sedimentary rocks of Jurassic age which dip gently eastwards.

The geology of Lincolnshire in eastern England largely consists of an easterly dipping succession of Mesozoic age sedimentary rocks, obscured across large parts of the county by unconsolidated deposits dating from the last few hundred thousand years of the present Quaternary Period.

The geology of Merseyside in northwest England largely consists of a faulted sequence of Carboniferous Coal Measures rocks overlain in the west by younger Triassic and Permian age sandstones and mudstones. Glaciation during the present Quaternary Period has left widespread glacial till as well as erosional landforms. Other post-glacial superficial deposits such as river and estuarine alluvium, peat and blown sand are abundant.

Coralline Crag Formation

The Coralline Crag Formation is a geological formation in England. The Coralline Crag Formation is a series of marine deposits found near the North Sea coast of Suffolk and characterised by bryozoan and mollusc debris. The deposit, whose onshore occurrence is mainly restricted to the area around Aldeburgh and Orford, is a series of bioclastic calcarenites and silty sands with shell debris, deposited during a short-lived warm period at the start of the Pliocene Epoch of the Neogene Period. Small areas of the rock formation are found in locations such as Boyton and Tattingstone to the south of Orford as well as offshore at Sizewell.

The geology of West Sussex in southeast England comprises a succession of sedimentary rocks of Cretaceous age overlain in the south by sediments of Palaeogene age. The sequence of strata from both periods consists of a variety of sandstones, mudstones, siltstones and limestones. These sediments were deposited within the Hampshire and Weald basins. Erosion subsequent to large scale but gentle folding associated with the Alpine Orogeny has resulted in the present outcrop pattern across the county, dominated by the north facing chalk scarp of the South Downs. The bedrock is overlain by a suite of Quaternary deposits of varied origin. Parts of both the bedrock and these superficial deposits have been worked for a variety of minerals for use in construction, industry and agriculture.

This article describes the geology of the Broads, an area of East Anglia in eastern England characterised by rivers, marshes and shallow lakes (‘broads’). The Broads is designated as a protected landscape with ‘status equivalent to a national park’.

The geology of national parks in Britain strongly influences the landscape character of each of the fifteen such areas which have been designated. There are ten national parks in England, three in Wales and two in Scotland. Ten of these were established in England and Wales in the 1950s under the provisions of the National Parks and Access to the Countryside Act 1949. With one exception, all of these first ten, together with the two Scottish parks were centred on upland or coastal areas formed from Palaeozoic rocks. The exception is the North York Moors National Park which is formed from sedimentary rocks of Jurassic age.

The geology of Exmoor National Park in south-west England contributes significantly to the character of a landscape which was designated as a national park in 1954. The bedrock of the area consists almost wholly of a suite of sedimentary rocks deposited during the Devonian, a period named for the English county of Devon in which the western half of the park sits. The eastern part lies within Somerset and it is within this part of the park that limited outcrops of Triassic and Jurassic age rocks are to be found.

Geology of the Isle of Mull

The geology of the Isle of Mull in Scotland is dominated by the development during the early Palaeogene period of a ‘volcanic central complex’ associated with the opening of the Atlantic Ocean. The bedrock of the larger part of the island is formed by basalt lava flows ascribed to the Mull Lava Group erupted onto a succession of Mesozoic sedimentary rocks during the Palaeocene epoch. Precambrian and Palaeozoic rocks occur at the island's margins. A number of distinct deposits and features such as raised beaches were formed during the Quaternary period.

The geology of the Gower Peninsula in South Wales is central to its character and to its appeal to visitors. The peninsula is formed almost entirely from a faulted and folded sequence of Carboniferous rocks though both the earlier Old Red Sandstone and later New Red Sandstone are also present. Gower lay on the southern margin of the last ice sheet and has been a focus of interest for researchers and students in that respect too. Cave development and the use of some for early human occupation is a further significant aspect of the peninsula's scientific and cultural interest.

References

  1. British Geological Survey 1:625,000 scale geological map Bedrock Geology UK South 5th Edn. NERC 2007
  2. Brenchley, P.J. & Rawson, P.F. (eds) 2006 The Geology of England and Wales. The Geological Society, London. p142
  3. Brenchley, P.J. & Rawson, P.F. (eds) 2006 The Geology of England and Wales. The Geological Society, London. p442
  4. British Geological Survey 1:625,000 scale geological map Quaternary Map of the United Kingdom South 1st Edn. 1977