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.

The Norwich Crag is a marginal facies of the thicker, much better developed sedimentary sequence in the southern North Sea basin.

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 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.

[2]: 32 The Norwich Crag was first identified in the early 19th century as a predominantly marine geological formation, then thought to be of Pliocene age, outcropping from Aldeburgh to the valley of the River Bure.

[14] The Norwich Crag Formation is a marginal facies of the thicker, much better developed sedimentary sequence in the southern North Sea basin.

It is overlain disconformably by the Wroxham Crag Formation, and unconformably by the Kesgrave Catchment Subgroup and Mid Pleistocene glacigenic deposits.

[17] The heavy minerals in the sand-sized fraction of the sediment are characterised by high concentrations of garnet, amphibole and epidote, which suggests that the sands originated from eastern (continental) rather than western (British) fluvial sources.

[19] These deposits represent environments fluctuating between marine transgressive and regressive episodes on the western margins of the North Sea basin.

[24] 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.

[17][26] The North Sea was a bight at this time, with its southern margin defined by the chalk hills of the Weald-Artois anticline where the Strait of Dover is now located.

[17] 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.

[32] The historic chronostratigraphic correlations and palaeoenvironmental interpretations based on biostratigraphy (local and continental) have been criticised as poorly defined and unreliable by Riches (2012).

[44] However they show evidence of considerable transportation, and consequent mixing of faunal assemblages from the earlier Red Crag Formation.

[2][7][14] Fossil shells are scarce or absent in some horizons, which may be due to contemporaneous erosion or non-deposition or post-depositional calcium carbonate solution.

[18]: 368 The most complete fossil record of plant life in the Norwich Crag is provided by evidence from the Ludham research borehole.

[8][46] Further work on Norwich Crag sediments at Bramerton, Norfolk, allowed a Bramertonian stage to be identified, characterised by temperate forest with Quercus, Carpinus and Alnus.

[33] Dinoflagellate fossil assemblages have been used in the Norwich Crag as indicators of palaeoclimatic conditions,[31] although evidence for reworking of earlier dinocysts suggests caution in interpretation.

[49] Fossil foraminifera provide important evidence for climatic and environmental interpretation and stratigraphic correlation in the Norwich Crag.

[50] The evidence from fossil plants, mammals, molluscs, foraminifers and dinoflagellates has been used to make biostratigraphic correlations between chronostratigraphic Stages recognised in East Anglia and the more complete sequence on the Continent.

[53] The human origin for these Crag specimens was refuted by FN Haward[55] on the basis of a systematic analysis of flint fracture patterns and geological context.