The Story of the North Wessex Downs A special landscape formed 100 million years ago Shaped by people over the last 6000 A very special place for wildlife
What lies beneath? 3 layers of chalk laid down 145 – 65 million years ago Before the chalk
Early Cretaceous period Upper Greensand and Gault Clay deposits Chalk How was the chalk formed?
Late Cretaceous period Coccolithophores – microscopic plankton - lived in sub-tropical, shallow seas They died and sank and fossilised coccoliths built up into solid chalk Layers of Lower, Middle and Upper Chalk 24 million years
What happened next? (65 – 2.5 million years ago) Alpine orogeny – collision 1,000 km away – sea becomes land Paleogene: Sarsens - Quartz (Siliceous) Sandstone – later exposed through erosion Neogene: the Reading Beds, Bagshot Beds and London Clay Fertile, loamy soils overlying London Clay Nutrient-poor, acid soils on plateau gravels What’s happened in the last 2.5 million years ? Quaternary period Drift deposits of clay with flints over chalk Combe (slope) deposits The Goring Gap Along the northern edge a dramatic chalk scarp formed from erosion of the soft Lower Chalk
How has the geology shaped what we see today? Steep scarp slopes Gently rolling hills Dry valleys Chalk streams Wooded hilltops Flints Sarsen stones (grey wethers) Ancient monuments Building materials: chalk, clay bricks, flints, sarsens
What lies beneath? 3 layers of chalk laid down 145 – 65 million years ago
A landscape formed by chalk and shaped by people Until 6000 years ago hunter gatherers moved through the area After 4000 BC: they settled on chalk uplands, planting, burying their dead and making tools and weapons Neolithic long barrows: West Kennet, Waylands Smithy From 2400 BC: monuments, settlements, farms and forts A landscape formed by chalk and shaped by people Avebury: the world’s largest prehistoric stone circle, made around 4,500 years ago
Silbury Hill : from the same time, the largest prehistoric man- made structure in Europe
Waylands Smithy
Archaeology and History in the North Wessex Downs Written in the Land An interactive website Based on Historic Landscape Characterisation Explore the history of local woods, fields and settlements www.historicnorthwessexdowns.org.uk Supported by the Heritage Lottery Fund Water and the Landscape Chalk soaks up water like a sponge Aquifers deliver clean, sparkling springs Water at constant 10º C Unique ecology National resource: London’s water Water and the Landscape
Winterbourne with intermittent springs Winter Springs water Years table
Summer Decades Chalk Impermeable beds water table
Chalk streams and rivers
80% of the world’s chalk streams are in England Kennet , Lambourn, Pang, Hampshire Avon, Thames and Bourne Winterbournes A delicate ecosystem and a rare habitat - easily upset by fertilisers, chemicals and run-off Invasive non-native species Special Habitats
Chalk grassland Arable farmland Chalk streams & rivers
Woodland Heathland Hedgerows
Richard Hennesey
Mike Rae Matt Cole
This is pure downland, the breasted hills curving as if under the influence of a great melody. It is beautiful, quiet and unrenowned and a most visibly ancient landscape. Edward Thomas 1878-1917
Martinsell Hill Near Pewsey