Bouldnor Formation

The Bouldnor Formation is a geological formation in the Hampshire Basin of southern England. It is the youngest formation of the Solent Group and was deposited during the uppermost Eocene and lower Oligocene.

The Bouldnor Formation was named after Bouldnor, a small hamlet east of Yarmouth, Isle of Wight. The formation is exposed along Bouldnor Cliff between Yarmouth and Hamstead occupying the core of the eastsoutheast-striking Bouldnor Syncline.

Yet the stratotype of the formation is found at Whitecliff Bay on the east side of the Isle of Wight.

The Bouldnor Formation was scientifically established 1985 by A. Insole and B. Daly, who also defined its members. The paleogene strata on the Isle of Wight had already been described in 1853 by Edward Forbes. Forbes was followed in 1921 by H.J.O. White, a geologist from the Geological Survey.

The Bouldnor-Formation is the topmost formation of the Solent Group before the sea withdrew completely from the Hampshire Basin. The thickness of the formation can vary between 45 and 115 metres. After a long hiatus and Holocene sediments covered the formation discordantly. The Bouldnor Formation lies concordantly on desiccation cracks of the upper Bembridge Limestone (Bembridge Limestone Formation), a freshwater deposit.

The formation consists mainly of clays with some intercalated sands which were sedimented along a coastal plain in lagoonal and lacustrine/palustrine facies judging by the enclosed freshwater, brackish and marine biota. Marine conditions were only rarely achieved, examples being the Bembridge Oyster Bed, the Nematura Bed and sections of the upper Cranmore Member.

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