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 Overview maps
 Locality areas
  Cheddar Gorge
 Charterhouse
 Blackdown
 Burrington Combe
 Shipham & Rowberrow
 Crook Peak & Axbridge
 Banwell to Churchill
 Priddy
 Harptree & Smitham Hill
 Draycott & Westbury-sub
 -Mendip
 Wookey Hole & Ebbor
 Gorge
 Wells
 Great Elm & Vallis Vale
 Mells & the Wadbury Valley
 The Vobster area
 The Whatley area
 Torr Works & Asham Wood
 Beacon Hill
 Stoke St Michael & Oakhill
 Holwell & Nunney
 Shepton Mallet & Maesbury
 Gurney Slade & Emborough
 The Nettlebridge valley
 Geology
 Rocks of Mendips
 Fossils
 Geological timescale
 Ancient environments
 Geological structure
 Minerals and mines
  Minerals and mines
 Industrial archaeology
 Quarrying
  Stone as a resource
 Employment & the economy
 Quarrying & geodiversity
 Quarrying & the environment
 History of quarrying
 Caves and karst
 How caves form
 Dry valleys and gorges
 Dolines and sinkholes
 Mendip caves
 Going caving
 Hydrogeology
 Biodiversity
  Flora and fauna
 Typical Mendip habitats
 Special Mendip habitats
 Horseshoe bats
 Appendix of names
 Biodiversity of western
 Mendip
 Biodiversity of eastern
 Mendip
 External links
 Detailed site information
  Coal mining
  Mendip quarry companies
  East Mendip quarries
 Biodiversity of eastern
 Mendip
  West Mendip quarries
 Biodiversity of western
 Mendip
 Acknowledgements
 Site map
Ancient environments
Silurian l Devonian l Carboniferous l Triassic l Jurassic

The Devonian, 385 – 359 million years ago

Earth movements at the end of the Silurian saw the final closure of the Iapetus Ocean that had separated northern and southern Britain. With the final elimination of the sea from most of the UK, and the creation of mountain chains across Scotland, Wales and Northern England, Britain was now part of a semi-arid continental landmass.

In the Mendips, only the youngest part of the Devonian is represented in the rock succession. The thick sandstones, pebbly sandstones and mudstones of the Portishead Formation were laid down by meandering river systems at the southern margin of a large landmass. The sea covered southern England south of the Mendips.

Portishead
            Formation
  During the Devonian land plants evolved, and the microscopic spores they produced are sometimes found as fossils. Towards the top of the largely unfossiliferous Devonian succession in the Mendips, there are the remains of plants and fish, heralding the dramatic change in environment that occurred across the region at the beginning of the Carboniferous.

The mendip region formed part of a broad coastal plain in the Devonian. Meandering rivers crossing this plain deposited sands, pebble beds and muds.
The Mendip region formed part of a broad coastal plain in the Devonian. Meandering rivers crossing this plain deposited sands, pebble beds and muds.
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