Geodiversity Landscapes: Uplands 

In the west of the county, there are four areas of ‘uplands’, less famous than the hills in the south of Cambridgeshire. Three of these western uplands, the Grafham Plateau, Alconbury Weald and the Western Plateau, are mostly underlain by Jurassic clays and covered with extensive areas of glacial deposits, also with a high content of clay. However, the northernmost upland, the Jurassic Limestone Ridge, is very different, consisting mainly of limestone interspersed with clays and sandstones. The ridge lies between the Welland and Nene Valleys, with an additional area lying to the south of the latter. Limestone quarries at Barnack are the source of one of the most famous building stones in the east of England, used to build the cathedrals at Ely and Peterborough. These Jurassic formations are part of the limestone sequence that extends south as the Cotswolds and north into Yorkshire.

The ‘Ice Age’ glacial deposits (mostly ’tills’) date from the last half a million years and consist of a mixture of clays, sands, silts, chalk, gravel, pebbles, cobbles and a few larger ‘erratics’. The Western Plateau, between the Cam and Ouse valleys to the west of Cambridge, is famous for its ‘boulder clay’ woodlands.

Towards the south east, the bedrock become younger, with the lowest Cretaceous rock formation (overlying the youngest Jurassic) being the Woburn Sands. This sandstone, a continuation of the Greensand Ridge that runs through Bedfordshire. outcrops in several areas from around Gamlingay to Ely, giving the county a small area of sandy heath in the south west on the Western Plateau.

The Chalk escarpment that forms the southern part of the county dates from the Cretaceous and provides Cambridgeshire with a share of England’s chalk downland, extending as the Chilterns to the south west and as the Yorkshire Wolds in the north of the country. The escarpment forms two landscapes, the Heydon Uplands and the Balsham Uplands.