The Norwich Crag Formation is a stratigraphic unit of the British

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

Epoch. It is the second youngest unit of the

Crag Group The Crag Group is a geological group outcropping in East Anglia, England and adjacent areas of the North Sea. Its age ranges from approximately 4.4 to 0.478 million years BP, spanning the late Pliocene and early to middle Pleistocene epochs. It ...

, a sequence of four geological formations spanning the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58East Anglia East Anglia is an area of the East of England, often defined as including the counties of Norfolk, Suffolk and Cambridgeshire, with parts of Essex sometimes also included. The name derives from the Anglo-Saxon kingdom of the East Angles, ...

. It was deposited between approximately 2.4 and 1.8 million years ago, during the

Gelasian The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary Period/System and Pleistocene Epoch/Series. It spans the time between 2.58 Ma (million y ...

Stage. The Norwich Crag is a marginal

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

of the thicker, much better developed sedimentary sequence in the southern

North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...

basin. It outcrops in the eastern half of the counties of

Norfolk Norfolk ( ) is a Ceremonial counties of England, ceremonial county in England, located in East Anglia and officially part of the East of England region. It borders Lincolnshire and The Wash to the north-west, the North Sea to the north and eas ...

and

Suffolk Suffolk ( ) is a ceremonial county in the East of England and East Anglia. It is bordered by Norfolk to the north, the North Sea to the east, Essex to the south, and Cambridgeshire to the west. Ipswich is the largest settlement and the county ...

, and is also represented in

Essex Essex ( ) is a Ceremonial counties of England, ceremonial county in the East of England, and one of the home counties. It is bordered by Cambridgeshire and Suffolk to the north, the North Sea to the east, Kent across the Thames Estuary to the ...

and

Hertfordshire Hertfordshire ( or ; often abbreviated Herts) is a ceremonial county in the East of England and one of the home counties. It borders Bedfordshire to the north-west, Cambridgeshire to the north-east, Essex to the east, Greater London to the ...

. It was deposited in a near-shore environment, and comprises a range of sands, silty clays and flint-rich gravels representing various

transgressive Transgressive may mean: *Transgressive art, a name given to art forms that violate perceived boundaries *Transgressive fiction, a modern style in literature *Transgressive Records, a United Kingdom-based independent record label *Transgressive (l ...

and regressive marine episodes. It rests in some places on the

Red Crag Formation The Red Crag Formation is a geological formation in England. It outcrops in south-eastern Suffolk and north-eastern Essex. The name derives from its iron-stained reddish colour and ''crag'' which is an East Anglian word for shells. It is part of t ...

and in others

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

on Coralline Crag,

Palaeogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

formations and

Chalk Group The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur ac ...

bedrock. It is overlain by the Wroxham Crag Formation, and unconformably by the Kesgrave Catchment Subgroup (part of the Dunwich Group) and Mid Pleistocene glacigenic deposits. Norwich Crag

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

fauna Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...

and

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

have been studied since the 19th century for information about environmental conditions during the early Pleistocene. They provide evidence for a general climatic cooling trend from the Pliocene to the Pleistocene.

History of research

The term Crag was first used in a geological sense by R.C. Taylor in 1823, a word commonly used in

to designate a deposit of fossil sea shellsForby, F (1830)
''The Vocabulary of East Anglia''
JB Nichols & Son, London, Volume I, p.81 or any shelly sand or gravel.Woodward, HB (1881)
''The Geology of the Country around Norwich''
Memoirs of the Geological Survey of the United Kingdom. London: HMSO. The Norwich Crag was first identified in the early 19th century as a predominantly marine geological formation, then thought to be of

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Aldeburgh Aldeburgh ( ) is a coastal town and civil parish in the East Suffolk District, East Suffolk district, in the English county, county of Suffolk, England, north of the River Alde. Its estimated population was 2,276 in 2019. It was home to the comp ...

to the valley of the

River Bure The River Bure is a river in the county of Norfolk, England, most of it in the Broads.Ordnance Survey (2005). ''OS Explorer Map OL40 - The Broads''. . The Bure rises near Melton Constable, upstream of Aylsham, which was the original head of ...

. It was variously termed the Mammaliferous Crag (Charlesworth 1836), Norwich Crag (Lyell 1839), Norfolk Crag (Phillips 1863) and Upper Crag (Godwin-Austen 1868). Five horizons were initially recognised: the Mammaliferous Stone-Bed; the Fluvio-marine Crag; the Chillesford Crag; the Chillesford Clay; the Bure Valley Crag, including the Westleton Beds. Additional units were identified in the Norwich Crag Series, the Weybourne CragPrestwich, J (1890)
''On the relation of the Westleton Beds or Pebbly sands of Suffolk to those of Norfolk and on their extension inland; with some observations on the period of the final elevation and denudation of the Weald and the Thames valley, etc. Part 1''
Quarterly Journal of the Geological Society, vol.46, pp.84-119.Reid, Clement (1882)
''The Geology of the Country around Cromer''
Memoirs of the Geological Survey of the United Kingdom. London:HMSO, p.9. and the Bure Valley Beds.Woodward, HB (1876). ''The Geology of England and Wales''. Longmans, Green & Co, London; pp.286-291. This stratigraphy was later formalised by FW Harmer, who grouped them all into an Icenian faunal zone of the Pliocene.Harmer, FW 1900
''The Pliocene Deposits of the East of England - Part II : The Crag of Essex (Waltonian) and its relations to that of Suffolk and Norfolk''
Quarterly Journal of the Geological Society, vol.56; pp.705-744. Research into sediments from the Ludham research borehole (1959) allowed a sequence of vegetational and faunal episodes to be recognised in the Norwich Crag, based on fossil

foraminifera Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...

, pollen and mollusca.Funnell, BM (1961)
''The Palaeogene and early Pleistocene of Norfolk''
Transactions of the Norfolk and Norwich Naturalists’ Society, vol.19, pt.6, pp.340-364West, RG (1962). ''Vegetational history of the Early Pleistocene of the Royal Society Borehole at Ludham, Norfolk''. Proceedings of the Royal Society of London, B155, pp.437-453.Norton, PEP (1967). ''Marine Molluscan Assemblages in the Early Pleistocene of Sidestrand, Bramerton and the Royal Society Borehole at Ludham, Norfolk''. Philosophic Transactions of the Royal Society of London, Series B, vol.253, no.784. A revised

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

and

biostratigraphical Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. "Biostratigraphy." ''Oxford Reference: Dictionary of Biology ...

framework was published by Funnell and West (1977).Funnell, BM & West, RG (1977). ''Preglacial Pleistocene deposits of East Anglia''. In: Shotton, FW (ed). ''British Quaternary Studies: recent advances''. Oxford University Press, 1977. . Research into the lithostratigraphy of the Norwich Crag was carried out by the

British Geological Survey The British Geological Survey (BGS) is a partly publicly funded body which aims to advance Earth science, geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. ...

between 1975 and 2006 as part of work to remap the geology of Norfolk and Suffolk; new techniques allowed improved understanding of local detail,Zalasiewicz, JA & Mathers, SJ (1985). ''Lithostratigraphy of the Red and Norwich Crags of the Aldeburgh-Orford Area, south-east Suffolk''. Geological Magazine, vol.122, pt.3; pp.287-296. and it became possible to distinguish the Norwich Crag from the succeeding Wroxham Crag (now subsuming the Weybourne Crag and Bure Valley Beds). Following international revisions to the Pliocene/Pleistocene boundary, the Norwich Crag is now placed in the Lower Pleistocene.Gibbard, PL, Zalasiewicz, JA & Mathers, SJ (1998). ''Stratigraphy of the marine Plio-Pleistocene crag deposits of East Anglia''. In: van Kolfschoten, T and Gibbard, PL (eds): ''The Dawn of the Quaternary - proceedings of the SEQS-EuroMam Symposium : Kerkrade, 16–21 June 1996''. Netherlands Institute of Applied Geoscience, 1998; pp.239-262. . Six lithostratigraphic members were recognised by the

Geological Society of London The Geological Society of London, known commonly as the Geological Society, is a learned society based in the United Kingdom. It is the oldest national geological society in the world and the largest in Europe, with more than 12,000 Fellows. Fe ...

:Bowen, DQ (ed) (1999). ''A revised correlation of Quaternary deposits in the British Isles''. Special Report no.23, The Geological Society, p.22. . the Chillesford Church Member (a basal deposit of marine sand, formerly the Chillesford Sand Member); the Chillesford Member (micaceous, silty clays overlying the Church Member, formerly the Chillesford Clay Member); the Creeting Member (micaceous, inter-tidal sands); the College Farm Member (silty clay of mud flats associated with the Creeting Member); the Easton Bavents Member (clay with sand laminae); the Westleton Member (flint-rich gravels overlying the Easton Bavents Member). The

type site In archaeology, a type site (American English) or type-site (British English) is the site used to define a particular archaeological culture or other typological unit, which is often named after it. For example, discoveries at La Tène and H ...

of the Formation is at Bramerton Pits SSSI, near Norwich.Reid, Clement (1890)
''The Pliocene Deposits of Britain''
Memoirs of the Geological Survey of the United Kingdom, London: HMSO

The sedimentary record

The Norwich Crag Formation is a marginal facies of the thicker, much better developed sedimentary sequence in the southern North Sea basin. It outcrops in the eastern half of the counties of Norfolk and Suffolk, and is also represented in Essex and Hertfordshire.Mathers, SJ & Zalasiewicz, JA (1988a). ''The Red Crag and Norwich Crag Formations of southern East Anglia''. Proceedings of the Geologists’ Association vol.99, pt.4; pp.261-278 Geological field relationships show that it rests with discontinuity on the

and oversteps in other places onto the Coralline Crag, the

formations and

bedrock. It is overlain disconformably by the Wroxham Crag Formation, and unconformably by the Kesgrave Catchment Subgroup and Mid Pleistocene glacigenic deposits.''The BGS Lexicon of Named Rock Units''. British Geological Survey. Online at http://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=NCG. Accessed October 2017. The Norwich Crag comprises a widespread sheet of well sorted, fine- to medium-grained

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

ceous,

glauconitic Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek () m ...

, locally shelly sands (e.g. the Chillesford Sand Member), with localized beds of laminated silty clays (particularly the Chillesford Clay and Easton Bavents Clay members) and well sorted fine to medium sands with beds of rounded flint gravels (notably the Westleton Beds Member). The pebbles are predominantly composed of

flint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Historically, flint was widely used to make stone tools and start ...

, typically more than 95% local material, either chattermarked (beach-abraded) or angular or sub-angular flint; the remaining 5% is typically white vein

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

and white

quartzite Quartzite is a hard, non- foliated metamorphic rock that was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...

.Rose, J (2007). ''Palaeogeography of Eastern England during the Early & Middle Pleistocene''. In: Candy, I et al. ''The Quaternary of Northern East Anglia Field Guide''. Quaternary Research Association, 2007. The heavy minerals in the sand-sized fraction of the sediment are characterised by high concentrations of

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, de ...

amphibole Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...

and

epidote Epidote is a calcium aluminium iron sorosilicate mineral. Description Well developed crystals of epidote, Ca2Al2(Fe3+;Al)(SiO4)(Si2O7)O(OH), crystallizing in the monoclinic system, are of frequent occurrence: they are commonly prismatic in ha ...

, which suggests that the sands originated from eastern (continental) rather than western (British) fluvial sources.Riches, P (2012). ''The palaeoenvironmental and neotectonic history of the Early Pleistocene Crag basin in East Anglia''. Ph.D thesis, Royal Holloway, University of London. The sandy sediments are near-shore marine deposits, with the clay members being estuarine or lagoonal, and the flint gravels are also near-shore marine, interpreted as channel infills, the gravels having been reworked from gravel beach deposits.Mottram, HB, (2017). ''Tidal-inlets and gravel deposition during the late Norwich Crag (Lower Pleistocene) of north-eastern Suffolk, U.K''. Proceedings of the Geologists’ Association 128; pp.547–557. These deposits represent environments fluctuating between marine transgressive and regressive episodes on the western margins of the North Sea basin.Moorlock, BSP, Hamblin, RJO, Booth, SJ & Morigi, AN (2000). ''Geology of the country around Lowestoft and Saxmundham. Memoir for 1:50,000 Geological Sheets 176 and 191''. British Geological Survey. . The source of the distinctive flints, which are often rounded in the coarser sizes in the Westleton Beds Member, is as yet to be conclusively determined but it has been argued that the flints were obtained from local rather than distant Chalk .Mottram, HB, (2022). ''On the supply of clasts to the Westleton Beds: a review''. Bulletin of the Geological Society of Norfolk 72; pp.11–28. Comparison with better preserved sedimentary sequences of similar age in the Netherlands has shown that the Norwich Crag sequence is highly incomplete.Jones, RL & Keen, DH (1993). ''Pleistocene Environments of the British Isles''. Chapman & Hall. . Interpretation is hampered by difficulties with distinguishing major non-sequences from minor, local erosional discontinuities. For surface mapping purposes, the

has recognised five members: the Chillesford Sand, Chillesford Clay, Easton Bavents Clay, Westleton Beds and Sidestrand Members.Lee, J. R.; Woods, M. A.; Moorlock, B. S. P., eds. (2015). ''British Regional Geology: East Anglia (5th ed.)''. British Geological Survey. . The uppermost beds of the Crag Group (formerly the Bure Valley Beds and Weybourne Crag) are now attributed to the Wroxham Crag Formation, based on their high proportion of fluvially-derived, far-travelled

lithological The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lith ...

components.Rose, J, Moorlock, BSP & Hamblin, RJO (2000). ''Lithostratigraphy and palaeoenvironments of the pre-Anglian sands and gravels of East Anglia''. In: Lewis, SG, Whiteman, CA & Preece, RC (eds). ''The Quaternary of Norfolk and Suffolk Field Guide''. Quaternary Research Association, 2000. The Westleton Member may be regarded as a sedimentologically coherent and a lithologically and stratigraphically consistent unit stretching from central Norfolk to the Suffolk coast.Sinclair, J (1999). ''Plio-Pleistocene relative sea-level changes in East Anglian: evidence from the Westleton Member and related deposits''. Proceedings of the Geologists' Association 110, pp.149-162. Beds of fine-grained sediment may also serve as marker horizons in the Crag Basin. Considering the lithostratigraphy to include subsurface sediments evidence by borehole, Riches (2012) proposed three major units for the Basin; most recognisable where they are separated by regressive marine marker beds of silty clay, with the uppermost equated with the Chillesford Clay Member.

Palaeogeography

Early Norwich Crag deposition in East Anglia took place within a topographical context established in the late Pliocene: an eastward dipping plain developed on Cretaceous Chalk interrupted by three SSW to NNE trending depressions partly filled with Red Crag sediments. It is conjectured that at c.2.4 million years BP the North Sea coastline lay across east Norfolk and east Suffolk, with a continuation eastwards to

Holland Holland is a geographical regionG. Geerts & H. Heestermans, 1981, ''Groot Woordenboek der Nederlandse Taal. Deel I'', Van Dale Lexicografie, Utrecht, p 1105 and former provinces of the Netherlands, province on the western coast of the Netherland ...

; there were local embayments in the areas of

Stalham Stalham is a market town and civil parish on the River Ant in the English county of Norfolk, in East Anglia. It covers an area of and had a population of 2,951 in 1,333 households at the 2001 census, the population increasing to 3,149 at the ...

Bungay Bungay () is a market town, civil parish and electoral ward in the East Suffolk district of Suffolk, England.OS Explorer Map OL40: The Broads: (1:25 000) : . It lies in the Waveney Valley, west of Beccles on the edge of The Broads, and at th ...

and

Stradbroke Stradbroke ( ) is an English village in the Mid Suffolk district of the county of Suffolk. The census of 2011 gave the parish a population of 1,408, with an estimate of 1,513 in 2018. Heritage The village was listed in the Domesday Book of ...

.Funnell, BM (1996). ''Plio-Pleistocene Palaeogeography of the Southern North Sea Basin (3.75 - 0.60 Ma)''. Quaternary Science Reviews, vol.15. The North Sea was a

bight The word is derived from Old English ''byht'' (“bend, angle, corner; bay, bight”). In modern English, bight may refer to: * Bight (geography), recess of a coast, bay, or other curved feature * Bight (knot), a curved section, slack part, or loo ...

at this time, with its southern margin defined by the chalk hills of the Weald-Artois anticline where the

Strait of Dover The Strait of Dover or Dover Strait, historically known as the Dover Narrows, is the strait at the narrowest part of the English Channel, marking the boundary between the Channel and the North Sea, and separating Great Britain from continental ...

is now located.Kuhlmann, G (2004). ''High resolution stratigraphy and paleoenvironmental changes in the southern North Sea during the Neogene : an integrated study of Late Cenozoic marine deposits from the northern part of the Dutch offshore area''. Geologica Ultraiectina, Vol.245 There is evidence for later marine transgression and extension of the sea as far west as the

Stansted Stansted Airport is an international airport serving London, the capital of England and the United Kingdom. It is located near Stansted Mountfitchet, Uttlesford, Essex, northeast of Central London. As London's third-busiest airport, Stan ...

area of Essex, associated with deposition of the Chillesford Sand Member during a period of high sea levels around two million years agoFunnell, BM (1987). ''Late Pliocene and Early Pleistocene stages of E Anglia and the adjacent North Sea''. Quaternary Newsletter 52, June 1987 correlated with the Antian/Bramertonian Stage. This was followed by marine regression during the Baventian/Pre-Pastonian a Stage. Evidence for major rivers, the Bytham and Proto-Thames, draining into the Crag Basin at this time is represented by far-travelled material found in estuarine deposits in eastern Suffolk, the Easton Bavents Clay and Chillesford Clay Members.Hamblin, RJO, Moorlock, BSP, Booth, SJ, Jeffery, DH & Morigi, AN (1997). ''The Red Crag and Norwich Crag formations in eastern Suffolk''. Proceedings of the Geologists’ Association, vol.1088, pp.11-23. The coastline shifted north-eastwards to a position in north-east Norfolk by about 1.75 million years BP. This later period is associated with deposition of the Wroxham Crag Formation and marked fluvial input by the Proto-Thames, Bytham River and Ancaster River systems.

Tectonic context

Since its deposition, the Norwich Crag Formation has undergone tectonic uplift and tilting as part of regional processes operating on the margins of the North Sea basin. The Chillesford Sand Member ranges in elevation from c.90 metres above sea level at Widdington, Essex, to its base at c.6 metres below sea level in the Aldeburgh-

Sizewell Sizewell is an English fishing hamlet in the East Suffolk district of Suffolk, England. It belongs to the civil parish of Leiston and lies on the North Sea coast just north of the larger holiday village of Thorpeness, between the coastal tow ...

area. There is therefore evidence for regional uplift of over 90 metres in western East Anglia and tilting towards the North Sea over the last two million years.Mathers, SJ & Zalasiewicz, JA (1988). ''The Pliocene to early Middle Pleistocene of East Anglia''. In: Gibbard, PL & Zalasiewicz (eds). ''Pliocene-Middle Pleistocene of East Anglia Field Guide''. Quaternary Research Association, 1988. The uplift has, however, been uneven, with little change apparent in north-east Norfolk in the

West Runton West Runton is a village in North Norfolk, England, on the North Sea coast. Toponymy The villages name means either, Runa's farm/settlement' or 'Runi's farm/settlement'. Overview West Runton and East Runton together form the parish of Runt ...

–

Happisburgh Happisburgh () is a village civil parish in the English county of Norfolk. The village is on the coast, to the east of a north–south road, the B1159 from Bacton on the coast to Stalham. It is a nucleated village. The nearest substantial ...

area. Evidence for fluctuations in relative sea level in the Crag Basin during the Plio-Pleistocene have been attributed to a variety of mechanisms including glacio-isostatic adjustments, eustatic changes and basinal response to sedimentary loading.

Fauna and flora

The fossil fauna and flora of the Norwich Crag have been studied since the early 19th century for

biostratigraphic Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. "Biostratigraphy." ''Oxford Reference: Dictionary of Biology ...

and

palaeoclimatic Paleoclimatology (British spelling, palaeoclimatology) is the scientific study of climates predating the invention of meteorological instruments, when no direct measurement data were available. As instrumental records only span a tiny part of Ea ...

interpretation. Taxa used include plants, molluscs,

foraminifer Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of Rhizarian protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

s, mammals and

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

s.Head, MJ (1988). ''Marine environmental change in the Pliocene and early Pleistocene of eastern England: the dinoflagellate evidence reviewed''. In: van Kolfschoten, T and Gibbard, PL (eds): ''The Dawn of the Quaternary - proceedings of the SEQS-EuroMam Symposium : Kerkrade, 16–21 June 1996''. Netherlands Institute of Applied Geoscience, 1998. . They provide evidence for a general climatic cooling trend from the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

. Three biostratigraphic stages have been identified based on fossil pollen assemblages: Thurnian, Antian/Bramertonian and Baventian/Pre-Pastonian a, representing a cold-warm-cold climatic sequence. Comparison with the better preserved sedimentary sequence in the Netherlands and the North Sea suggests it is unlikely that this represents a single climatic cycle but rather a sequence of episodes represented in an incomplete sedimentary record.Gibbard, PL, Gibbard, West, RG, Zagwijn, WH, Balson, PS, Burger, AW, Funnell, BM, Jeffery, DH, de Jong, J, van Kolfschoten, T, Lister, AM, Meijer, T, Norton, PEP, Preece, RC, Rose, J, Stuart, AJ, Whiteman, CA and Zalasiewicz, JA. (1991). ''Early and early Middle Pleistocene correlations in the southern North Sea Basin''. Quaternary Science reviews, vol.10, no.1. The historic chronostratigraphic correlations and palaeoenvironmental interpretations based on biostratigraphy (local and continental) have been criticised as poorly defined and unreliable by Riches (2012). As the Norwich Crag is a marine formation, the majority of fossils found in it are of marine origin; any terrestrial species were originally blown or washed into it from land, or derived from earlier deposits, particularly the

Red Crag ''Red Crag'' or ''Red Rock'' () was a 1961 novel based partly on fact by Chinese authors Luo Guangbin and Yang Yiyan, who were former inmates in a Kuomintang prison in Sichuan. It was set in Chongqing during the Chinese Civil War in 1949, and fe ...

.Spencer, HEPS (1970). ''A Contribution to the Geological History of Suffolk, Part 5 : The Early Pleistocene. The Crag Epochs and their Mammals''. Transactions of the Suffolk Naturalists’ Society no.15, pt.4. Vertebrate fossils tend to be concentrated in the basement bed or in gravel lags.Richards, AE, Gibbard, PL and Pettitt, ME (1999). ''The sedimentology and palaeoecology of the Westleton Member of the Norwich Crag Formation (early Pleistocene) at Thorington, Suffolk, England''. Geological Magazine vol.136, pt.4. Species of warm and cold substages are represented, sometimes mixed together; this may pose problems for palaeoecological interpretation.Norton, PEP (1977). ''Marine Mollusca in the East Anglian pre-glacial Pleistocene''. In: Shotton, FW (ed). ''British Quaternary Studies - Recent Advances''. Clarendon Press, Oxford, 1977.

Mammals

Land mammal fauna

From a biostratigraphic point of view, the terrestrial mammal fauna of the Norwich Crag belongs to the Late

Villafranchian Villafranchian age ( ) is a period of geologic time (3.5–1.0 Ma) spanning the Late Pliocene and Early Pleistocene used more specifically with European Land Mammal Ages. Named by Italian geologist Lorenzo Pareto for a sequence of terrestrial se ...

European Land Mammal Age The European Land Mammal Mega Zones (abbreviation: ELMMZ, more commonly known as European land mammal ages or ELMA) are zones in rock layers that have a specific assemblage of fossils ( biozones) based on occurrences of fossil assemblages of Europ ...

and is correlated with European Neogene Mammal Zone MN17. The richest and best-preserved assemblage is found in deposits of Antian/Bramertonian age at Easton Wood,

Covehithe Covehithe is a village and civil parish in the East Suffolk (district), East Suffolk district of the English county of Suffolk. It lies on the North Sea coast around north of Southwold and south of Lowestoft. Neighbouring settlements include B ...

. Taxa collected from this site include proboscideans ''

Mammuthus meridionalis ''Mammuthus meridionalis'', sometimes called the southern mammoth, is an extinct species of mammoth native to Eurasia during the Early Pleistocene. Reaching a size exceeding modern elephants, unlike later Eurasian mammoth species, it was largely ...

'' and ''

Anancus arvernensis ''Anancus'' is an extinct genus of "tetralophodont gomphothere" native to Afro-Eurasia, that lived from the Tortonian stage of the late Miocene until its extinction during the Early Pleistocene, roughly from 8.5–2 million years ago. Taxonomy ...

'', horse '' Equus robustus'', deer '' Eucladoceros falconeri'' and '' Eucladoceros sedgwicki'', gazelle '' Gazella anglica'', beaver ''

Trogontherium ''Trogontherium'' is an extinct genus of Eurasian giant beavers that lived from the Late Pliocene to the Late Pleistocene. Fossils of ''Trogontherium'' have been found across northern Eurasia, from Western Europe to China and Siberia. Taxonomy ...

'' sp., wolf ''

Canis etruscus ''Canis etruscus'' (the Etruscan wolf), is an extinct species of canine that was endemic to Mediterranean Europe and Crimean peninsula during the Early Pleistocene. The Etruscan wolf is described as a small wolf-like dog. It is widely agreed to ...

'', voles ''Mimomys pliocaenicus'', ''Mimomys reidi'' and ''Mimomys tigliensis'', and lemming ''Lemmus kowalskii''.UK Fossils (undated). ''Easton Wood''
/ref>Mayhew, DF (2011). ''West European arvicolid evidence of intercontinental connections during the early Pleistocene''. Quaternary International, vol.30.Carreck, JN (1966). ''Microtine remains from the Norwich Crag (Lower Pleistocene) of Easton Bavents, Suffolk''. Proceedings of the Geologists' Association, vol.77, pt. 4. Bramerton has yielded

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

s of the extinct otter ''Enhydra reevei'' and the gazelle '' Gazella daviesii''. The whole skeleton of a

mastodon A mastodon, from Ancient Greek μαστός (''mastós''), meaning "breast", and ὀδούς (''odoús'') "tooth", is a member of the genus ''Mammut'' (German for 'mammoth'), which was endemic to North America and lived from the late Miocene to ...

is reported to have been found in the basal Stone Bed resting on Chalk at Horstead in 1820. Vole fossils from the Norwich Crag contribute to the ‘vole clock’ used for biostratigraphic zonation of Pliocene and Pleistocene sediments. For instance, ''Mimomys pliocaenicus'' is a biozonal species for European Neogene Mammal Zone MN17. Bramerton has yielded the most primitive microtine rodent assemblage known from the British Isles.Mayhew, DF & Stuart, AJ (1986). ''Stratigraphic and taxonomic revision of the fossil vole remains (Rodentia, Microtinae) from the Lower Pleistocene of Eastern England''. Philosophical Transactions of the Royal Society of London, B312, pp.431-485.

Marine mammal fauna

Marine taxa from Easton Wood include ''

Orca The orca (''Orcinus orca''), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus '' Orcinus'', it is recognizable by its black-and-white-patterned body. A cosmopol ...

'' and the walrus '' Alachatherium cretsii''. The short-beaked common dolphin ''

Delphinus delphis The common dolphin (''Delphinus delphis'') is the most abundant cetacean in the world, with a global population of about six million. Despite this fact and its vernacular name, the common dolphin is not thought of as the archetypal dolphin, with ...

'' and indeterminate whale bones are recorded from Holton and Thorington.

Birds

Very few avian fossils have been found in the Norwich Crag. Bones of ''

common guillemot The common murre or common guillemot (''Uria aalge'') is a large auk. It has a circumpolar distribution, occurring in low-Arctic and boreal waters in the North Atlantic and North Pacific. It spends most of its time at sea, only coming to land to ...

'', ''

little auk The little auk (Europe) or dovekie (North America) ''Alle alle'' is a small auk, the only member of the genus ''Alle''. ''Alle'' is the Sami name of the long-tailed duck; it is onomatopoeic and imitates the call of the drake duck. Linnaeus was n ...

'' and various indeterminate seabird bones have been recorded from Aldeby, Chillesford, Easton Bavents and Yarn Hill.Mlikovsky, J (1995). ''Tertiary Avian Localities of the United Kingdom''. Acta Universitatis Carolinae Geologica, vol.29, pp.759-771. The albatross ''Phoebastria anglica'' has been recorded from Easton Wood, Covehithe.Dyke, GJ, Nudds, RL & Walker, CA (2007). ''The Pliocene Phoebastria (‘Diomedea’) anglica: Lydekker's English fossil albatross''. Ibis vol.149, no.3, pp.626-631.

Reptiles and Amphibians

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

and

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

fossils have yet been recorded from the Norwich Crag.Holman, JA (1998). ''Pleistocene Amphibians and Reptiles in Britain and Europe''. Oxford University Press. .

Fish

Fossil marine fish from the Norwich Crag include genera ''Chrysophrys'' sp. (a

snapper Snapper(s) may refer to: Animals * Lutjanidae, a family of fish known as snappers **''Lutjanus campechanus'', a fish found in the Gulf of Mexico and the Atlantic coast of the United States ** Bigeye snapper (''Lutjanus lutjanus''), a fish that p ...

), ''Acipenser'' (

sturgeon Sturgeon (from Old English ultimately from Proto-Indo-European language, Proto-Indo-European *''str̥(Hx)yón''-) is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the ...

) and ''Notidanus'' (a

cow shark Cow sharks are a shark family, the Hexanchidae, characterized by an additional pair or pairs of gill slits. Its species are placed within the 11 genera: '' Gladioserratus'', '' Heptranchias'', '' Hexanchus'', ''Notidanodon'', '' Notorynchus'', '' ...

), and species ''Platax woodwardi'' (a batfish), ''

Gadus morhua The Atlantic cod (: cod; ''Gadus morhua'') is a fish of the family Gadidae, widely consumed by humans. It is also commercially known as ''cod'' or ''codling''.Raja clavata The thornback ray (''Raja clavata''), or thornback skate, is a species of ray fish in the family Rajidae. Distribution The Thornback ray is found in the Atlantic coastal waters of Europe and western Africa. It is also present from South Afric ...

'' (thornback ray).Newton, ET (1891). ''The Vertebrata of the Pliocene Deposits of Britain''. Memoirs of the Geological Survey of the United Kingdom, London. Teeth of the freshwater fish ''

Esox lucius The northern pike (''Esox lucius'') is a species of carnivorous fish of the genus ''Esox'' (pikes). They are commonly found in brackish water, moderately salty and fresh waters of the Northern Hemisphere (''i.e.'' holarctic in distribution). T ...

'' (northern pike) have been found at Bramerton.

Molluscs

Molluscan fossils are abundant at certain horizons in the Norwich Crag. Historically, they have been used to construct palaeontological zonal schemes and to infer palaeoclimatic changes.Harmer, FW 1902. ''A sketch of the later Tertiary history of East Anglia''. Proceedings of the Geologists’ Association, vol.17. However they show evidence of considerable transportation, and consequent mixing of faunal assemblages from the earlier Red Crag Formation.Long, PE & Cambridge, PG (1988). ''Crag Mollusca: an overview''. In: Gibbard, PL & Zalasiewicz, JA (eds). ''Pliocene-Middle Pleistocene of East Anglia Field Guide''. Quaternary Research Association, 1988. . The use of molluscan fossils for climatic reconstruction has proved problematic. For instance species found together at several levels in the Ludham borehole notably '' Serripes groenlandicus'' (Greenland cockle) and ''

Calyptraea chinensis ''Calyptraea chinensis'', common name the Chinese hat snail or Chinese hat shell, is a species of small sea snail, a marine gastropod mollusk in the family Calyptraeidae, the slipper snails or slipper limpets, cup-and-saucer snails, and Chinese h ...

'' (Chinese hat snail) have notably different climatic tolerances today (arctic and lusitanic respectively). The presence of mixed arctic, boreal and lusitanic faunal elements at certain levels in the Ludham borehole give no indications of the climatic fluctuations evident from foraminiferal evidence. The local variability of molluscan assemblages at similar horizons was noted by Reid as adding uncertainty to their use for biostratigraphic correlation. However, molluscan fossils have proved most useful as indicators of water depth in marine facies. Molluscan assemblages identified from Norwich Crag deposits represent a range of environments (inner sublittoral; open coast; tidal flat wadden; offshore sublittoral) and climatic conditions (boreal; low arctic; temperate). Cold climate indicator species include ''

Astarte borealis ''Astarte borealis'' or ''Tridonta borealis'', the boreal astarte, is a species of bivalve mollusc in the family (biology), family Astartidae. It can be found in the Arctic Ocean and in the northern Pacific and Atlantic Oceans. Distribution ''A. ...

'' and '' Yoldia myalis'' from Baventian deposits at Covehithe. Some species have distinct biostratigraphic value. The absence of ''

Macoma balthica ''Limecola balthica'', commonly called the Baltic macoma, Baltic clam or Baltic tellin,Sartori, André F. (2016)''Limecola balthica'' (Linnaeus, 1758).In: Sartori, André F. (2016). Limecola balthica (Linnaeus, 1758). In: MolluscaBase (2016). Wo ...

'' is considered to be an indicator distinguishing Norwich Crag molluscan assemblages from those of the later Wroxham Crag. Fossil shells are scarce or absent in some horizons, which may be due to contemporaneous erosion or non-deposition or post-depositional

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

solution.

Plants

The most complete fossil record of plant life in the Norwich Crag is provided by evidence from the Ludham research borehole. Pollen analysis in association with foraminiferan evidence allowed the identification of pollen assemblage biozones and consequent designation of five biostratigraphic stages, of which three (Thurnian, Antian and Baventian) are correlated with the Norwich Crag. The Thurnian was identified as a glacial stage with an oceanic heath type of vegetation; the Antian with temperate mixed coniferous / deciduous forest including ''

Tsuga ''Tsuga'' (, from Japanese (), the name of '' Tsuga sieboldii'') is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The English-language common name "hemlock" arose from a perceived similarity in the smell of it ...

'' (hemlock) and ''

Pterocarya ''Pterocarya'', often called wingnuts in English, are trees in the walnut family Juglandaceae. They are native to Asia. The botanic name is from Ancient Greek (''pteron'') "wing" + (''karyon'') "Nut (fruit), nut". Description ''Pterocarya'' a ...

'' (wingnut); the Baventian, a glacial stage more severe than the Thurnian, with the return of oceanic heath.West, RG, Funnell, BM, and Norton, PEP (1980). ''An Early Pleistocene cold marine episode in the North Sea: pollen and faunal assemblages at Covehithe, Suffolk, England''. Boreas, vol.9. Further work on Norwich Crag sediments at

Bramerton Bramerton is a village and civil parish in the England, English county of Norfolk. Bramerton is located north-west of Loddon, Norfolk, Loddon and south-east of Norwich. History Bramerton's name is of Anglo-Saxons, Anglo-Saxon origin and d ...

, Norfolk, allowed a Bramertonian stage to be identified, characterised by temperate forest with ''

Quercus An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

'', ''

Carpinus Hornbeams are hardwood trees in the plant genus ''Carpinus'' in the family Betulaceae. Its species occur across much of the temperate regions of the Northern Hemisphere. Common names The common English name ''hornbeam'' derives from the hard ...

'' and ''

Alnus Alders are trees of the genus ''Alnus'' in the birch family Betulaceae. The genus includes about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species ext ...

''. Correlation was made with the pollen assemblage from Chillesford.Funnell, BM, Norton, PEP & West, RG (1979). ''The crag at Bramerton, near Norwich, Norfolk''. Philosophical Transactions of the Royal Society of London, B, 287, 489-534.West, RG (1980). Pleistocene Forest History in East Anglia. New Phytologist, 85 Specimens of fossil wood have occasionally been found, for example pyritised

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

and

oak An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

at Holton.

Dinoflagellates

Dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

fossil assemblages have been used in the Norwich Crag as indicators of palaeoclimatic conditions, although evidence for reworking of earlier

dinocysts Dinocysts or dinoflagellate cysts are typically 15 to 100 μm in diameter and produced by dinoflagellates as a dormant, zygotic stage of their lifecycle, which can accumulate in the sediments as microfossils. Organic-walled dinocysts are ofte ...

suggests caution in interpretation.Riding, JB, Moorlock, SP, Jeffrey, DH & Hamblin, RJO (1997). ''Reworked and indigenous palynomorphs from the Norwich Crag Formation (Pleistocene) of eastern Suffolk: implications for provenance, palaeogeography and climate''. Proceedings of the Geologists’ Association, vol. 108, pt.1.

Foraminifers

Fossil

provide important evidence for climatic and environmental interpretation and stratigraphic correlation in the Norwich Crag. The Ludham borehole has provided the most complete foraminiferal record, and has allowed the designation of seven biozones. Further biozones were identified at Bramerton and Easton Bavents, and assemblages identified at a number of other Norwich Crag sites, permitting correlation with the more complete sequence in the Netherlands.

Dating and correlations

The Norwich Crag Formation was deposited during the

Stage of the

, between about 2.4 and 1.8 million years ago.Mathers, SJ & Hamblin, RJO (2015). ''Late Pliocene and Pleistocene Marine Deposits''. In: Lee, JR; Woods, MA; Moorlock, BSP, eds. ''British Regional Geology: East Anglia (5th Edition)''. British Geological Survey; fig.46. . The evidence from fossil plants, mammals, molluscs, foraminifers and dinoflagellates has been used to make

correlations between

chronostratigraphic Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geological ...

Stages recognised in East Anglia and the more complete sequence on the Continent. Wider correlation is made with

Marine Isotope Stage Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from Oxygen isotope ratio cycle, oxygen isotope data derived from deep sea core ...

s (MIS) and

magnetostratigraphy Magnetostratigraphy is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their ' ...

, despite uncertainties in interpretation.Maher, B & Hallam (2005). ''Palaeomagnetic correlation and dating of Plio/Pleistocene sediments at the southern margins of the North Sea Basin''. Journal of Quaternary Science, vol.20, pt.1. It has been noted by Riches (2012) that pollen and foraminiferan assemblages are not age diagnostic, and may not alone be sufficient to sustain reliable stratigraphy. The Thurnian Stage has been variously correlated with Stage Tiglian A or Tiglian B in the Netherlands; the Antian/Bramertonian with Tiglian C1-3 or C1-4b; the Baventian/Pre-Pastonian a with Tiglian C1-4b or C-4c. This timespan is correlated with MIS 81 to 68 or MIS 95 to 71,Kuhlmann, G et al (2006). ''Integrated chronostratigraphy of the Plio-Pleistocene interval and its relation to the regional stratigraphical stages in the southern North Sea region''. Netherlands Journal of Geological Sciences, vol.85, pt.1. covering a time period of between 2.44 and 1.8 million years before present in the Matuyama Chron, corresponding to the magnetostratigraphic interval between the Reunion Sub-chron and the top of the Olduvai Sub-chron.

Eoliths and early humans

The discovery of chipped and flaked flints in the Norwich Crag and Red Crag basement beds in the late 19th and early 20th centuries was claimed as evidence for some of the earliest human settlement in Britain.Reid Moir, J (1927). ''The Antiquity of Man in East Anglia''. Cambridge University Press. A typologically diagnostic form of 'eolithic' beak-shaped instrument was proposed by E Ray Lankester, the ‘rostro-carinate’, based upon a ‘Norwich Test Specimen’ flint found in the basal Norwich Crag at Colman's Pit, Whitlingham. The human origin for these Crag specimens was refuted by FN HawardHaward, FN (1919). ''The origin of the 'Rostro-carinate Implements' and other Chipped Flints from the Basement Beds of East Anglia''. Proceedings of the Prehistoric Society of East Anglia vol.3 pt.1 (1918-1919). on the basis of a systematic analysis of flint fracture patterns and geological context. The fractures were identified by Warren (1923) as caused by sub-soil pressure flaking.Warren, SH (1923). ''Sub-soil Pressure flaking''. Proceedings of the Geologists' Association of London, vol.34.

References

External links

BGS Stratigraphic Lexicon: Norwich Crag Formation

Geological Society of Norfolk

GeoEssex

GeoSuffolk

Norfolk Geodiversity Partnership

Quaternary Research Association
Stratigraphy of the United Kingdom Lithostratigraphy of England Pleistocene Europe Sandstone formations East Anglia Geology of Norfolk