The geology of Norfolk in eastern

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 ...

largely consists of late

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

and Cenozoic sedimentary rocks of marine origin covered by an extensive spread of unconsolidated recent deposits.

Jurassic

The oldest rocks at or near the surface in

Norfolk Norfolk () is a ceremonial and non-metropolitan county in East Anglia in England. It borders Lincolnshire to the north-west, Cambridgeshire to the west and south-west, and Suffolk to the south. Its northern and eastern boundaries are the No ...

are late

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 ...

mudstones and muddy

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s which underlie recent deposits in the area west of King's Lynn and

Downham Market Downham Market, sometimes simply referred to as Downham, is a market town and civil parish in Norfolk, England. It lies on the edge of the Fens, on the River Great Ouse, approximately 11 miles south of King's Lynn, 39 miles west of Norwich and 30 ...

Cretaceous

Overlying the Jurassic is a

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

sequence whose lowermost unit is the Wealden Group comprising mudstones, limestones, siltstones and

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 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 The Lower Greensand Group is a geological unit present across large areas of Southern England. It was deposited during the Aptian and Albian stages of the Early Cretaceous. It predominantly consists of sandstone and unconsolidated sand that were ...

and beyond this, and stratigraphically above it, lie the mudstones and sandstones of the

Gault The Gault Formation is a geological formation of stiff blue clay deposited in a calm, fairly deep-water marine environment during the Lower Cretaceous Period (Upper and Middle Albian). It is well exposed in the coastal cliffs at Copt Point in ...

and

Upper Greensand Greensand or green sand is a sand or sandstone which has a greenish color. This term is specifically applied to shallow marine sediment that contains noticeable quantities of rounded greenish grains. These grains are called ''glauconies'' and c ...

formations. The Grey Chalk and the

White Chalk ''White Chalk'' is the seventh studio album by English singer-songwriter and musician PJ Harvey, released on 24 September 2007 on Island Records. Work on the album started in 2006, with producer Flood and John Parish, who also worked on her ...

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 Hockwold cum Wilton (''"Hock/mallow wood and willow-tree farm/settlement"'') is 10 miles west of Thetford, Norfolk, England and is in the borough of King's Lynn and West Norfolk. It is located near several USAF airbases, notably RAF Lakenheath ...

on the Suffolk border though it is concealed beneath later Neogene sediments in the east.

Palaeogene

The

Palaeogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...

Period is represented by a small area of

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

assigned to the

Thames Group The Thames Group is an Eocene lithostratigraphic group (a sequence of rock strata) which is widespread in southeast England, especially in the Hampshire Basin from Dorset through Hampshire to West Sussex and in the Isle of Wight and in the London ...

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 Sheringham (; population 7,367) is an English seaside town within the county of Norfolk, United Kingdom.Ordnance Survey (2002). ''OS Explorer Map 252 - Norfolk Coast East''. . The motto of the town, granted in 1953 to the Sheringham Urban Distr ...

through Cawston and

Norwich Norwich () is a cathedral city and district of Norfolk, England, of which it is the county town. Norwich is by the River Wensum, about north-east of London, north of Ipswich and east of Peterborough. As the seat of the See of Norwich, with ...

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 The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

age.

Structure

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

pluton associated with the Acadian orogeny is inferred to exist beneath central and western Norfolk.

Quaternary

The larger part of Norfolk's bedrock geology is concealed beneath superficial deposits, the oldest of which is a spread 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 ...

dating from the

Anglian glaciation The Anglian Stage is the name used in the British Isles for a middle Pleistocene glaciation. It precedes the Hoxnian Stage and follows the Cromerian Stage in the British Isles. The Anglian Stage is correlated to Marine Isotope Stage 12 (MIS 12), ...

. 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 Lincolnshire (abbreviated Lincs.) is a Counties of England, county in the East Midlands of England, with a long coastline on the North Sea to the east. It borders Norfolk to the south-east, Cambridgeshire to the south, Rutland to the south-we ...

and the Chiltern Hills has been put down to erosion by the Anglian icesheet which reached as far south as

Essex Essex () is a county in the East of England. One of the home counties, it borders Suffolk and Cambridgeshire to the north, the North Sea to the east, Hertfordshire to the west, Kent across the estuary of the River Thames to the south, and Grea ...

. The late Devensian glaciation resulted in the North Sea icesheet impinging upon the north coast of Norfolk. Of more recent origin are

alluvial deposits 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. Alluv ...

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 Brancaster is a village and civil parish on the north coast of the English county of Norfolk. The civil parish of Brancaster comprises Brancaster itself, together with Brancaster Staithe and Burnham Deepdale. The three villages form a more or ...

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 ...

deposits occur in places, for example around the valley of the

River Waveney The River Waveney is a river which forms the boundary between Suffolk and Norfolk, England, for much of its length within The Broads. The "ey" part of the name means "river" thus the name is tautological. Course The source of the River Wavene ...

. Blown sand characterises the lower sections of coast.

Peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficient ...

is widespread in the fenland areas south and west of Downham Market.British Geological Survey 1:625,000 scale geological map ''Quaternary Map of the United Kingdom South'' 1st Edn. 1977

References

{{Geology of England