Red Crag Formation

The Red Crag Formation is a series of marine deposits at the base of the Pleistocene in Suffolk and Essex. This material rests on an erosion surface of Cretaceous to Palaeogene rocks. It is a shore deposit, medium to coarse-grained and locally shelly.

The most extensive exposure of Red Crag is found at Bawdsey Cliff, the site of which is designated a Site of Special Scientific Interest. Around 2 kilometres (1.2 mi) of Crag from the Gelasian are exposed. Red Crag deposits have been dated from Piacenzian age at Walton-on-the-Naze to Preludhamian age at Sizewell on the basis of microfossils.

Crag is a local word for a shelly sand. The Red Crag is generally stained red by ferruginous compounds.

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