Norwich Crag Formation

Norwich Crag Formation
Stratigraphic range: Early Pleistocene ~2.4–1.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Easton Wood cliffs, Covehithe, Suffolk
Type	Geological formation
Unit of	Crag Group
Sub-units	Chillesford Sand member, Chillesford Clay Member, Easton Bavents Clay Member, Westleton Beds Member, Sidestrand Member
Underlies	Wroxham Crag Formation, Kesgrave Catchment Subgroup, Mid Pleistocene glacigenic deposits
Overlies	Red Crag Formation, Coralline Crag Formation
Thickness	about 70 metres
Lithology
Primary	Sand
Other	Gravel, clay, silt
Location
Region	East Anglia
Country	United Kingdom
Type section
Named for	Bramerton, Norwich
Named by	Clement Reid
Year defined	1890
Coordinates	52°12′53″N 1°24′58″E / 52.2147°N 1.4160°E / 52.2147; 1.4160

The Norwich Crag Formation is a stratigraphic unit of the British Pleistocene Epoch. It is the second youngest unit of the Crag Group, a sequence of four geological formations spanning the Pliocene to Lower Pleistocene transition in East Anglia. It was deposited between approximately 2.4 and 1.8 million years ago, during the Gelasian Stage.

The Norwich Crag 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. It was deposited in a near-shore environment, and comprises a range of sands, silty clays and flint-rich gravels representing various transgressive and regressive marine episodes. It rests in some places on the Red Crag Formation and in others unconformably on Coralline Crag, Palaeogene formations and Chalk Group 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 fauna and flora 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.