Geology

The nature and landscape of Greensand Country has been shaped by its geology, soils and historic land use. The area is famous for its patchwork of different habitats, including woodland, heathland (heather and acidic grassland), wetland, acid grassland, farmland and rivers.

Approximately 125 million years ago, the area we now know as Greensand Country was dominated by tropical shallow seas. Sediments of sandy minerals were deposited as silt, sand and gravel, which eventually became compressed into the Greensand rocks. Because the Greensand is a more resistant rock, it was not eroded as quickly as the softer clays surrounding it, leaving a ridge as a prominent feature in the landscape. Today, the ridge forms the ‘backbone’ of Greensand Country – it is the area’s most prominent landmark, home to diverse habitats, abundant wildlife and enjoyed year-round by walkers, cyclists and horse-riders.

Which rocks do you live on?

Jurassic Limestones: The oldest rocks in Greensand Country are rarely seen at the surface, but were quarried along the Ouse Valley upstream from Bedford. Often grey, but sometimes honey-coloured, they make attractive building stones for houses, churches and ancient bridges in Turvey, Harrold and Bromham.

Oxford Clay: This occur in Marston Vale and conceals the limestones in North Bedfordshire around villages like Riseley and Thurleigh. Much of this area is arable farmland, but brick-making left massive pits near Marston Moretaine, Stewartby and Elstow.

Lower Greensand: From the Woburn Sands Formation, this red-brown, iron-rich sandstone underlies Greensand Country from Leighton Buzzard to Potton. It appears in many churches & walls. Much of Greensand Country is wooded & large parks exist at Woburn, Ampthill and Southill. The Formation includes sand, extracted near Heath & Reach and Sandy, as well as pockets of Fuller Earth, formed from volcanic ash and formerly quarried near Clophill and Woburn.

Gault Clay: This grey clay lies beneath a vale of farmland and villages from Stanbridge to Stotfold. Pale-coloured bricks were made at Arlsey, and in small quantities elsewhere, and may be seen in villages including Toddington and Shillington.

Chalk: This white limestone forms the Chilterns from Dunstable Downs to Pegsdon Hills. Chalk was once quarried at Houghton Regis and Sundon for making lime & cement. A hard, grey layer called Tottenhoe Stone and black, glassy flints that formed in the chalk are used in many churches.

Are you interested in finding out more about the geology of Greensand Country? Join Bedfordshire Geology Group and meet others who are interested in geology and the impact it has on our surroundings. Members enjoy field trips, walks, talks and workshops. The group records and interprets sites of geological interest and works with museums, schools and others. Find out more at www.bedfordshiregeologygroup.org.uk