Plymouth Sound, Shores and Cliffs

Coordinates: 50°20′46″N 4°07′19″W / 50.3461°N 4.12208°W

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Plymouth Sound Shores and Cliffs
Site of Special Scientific Interest

Location within Devon
Location	Devon Cornwall
Coordinates	50°20′46″N 4°07′19″W / 50.3461°N 4.12208°W / 50.3461; -4.12208
Interest	Geological
Area	44.3 hectares (0.443 km²; 0.171 sq mi)
Notification	1997 (1997)
Natural England website

Plymouth Sound, Shores and Cliffs is a Site of Special Scientific Interest (SSSI) around the Plymouth Sound, a large area of water where the River Plym and Tamar meet. It stretches across the two ceremonial counties of Devon and Cornwall and the unitary authority area of Plymouth. It contains fossils of plants and sea creatures and its cliffs show a timeline of the Middle to Early Devonian period hundreds of millions of years ago

Geology

Lower to early Middle Devonian units of rock are visible from sections through the coastal cliffs and intertidal zones, which were laid down 417–354 million years ago.^[1] There are fossil remains of corals, brachiopods, bryozoa, gastropods, rare orthoconic nautiloids, ostracods, trilobites, phacopids), crinoids, ostracoderm and acanthodian fish.^[2]

Jennycliff Bay has steeply inclined folds, which flexure into open recumbent folds — some with chevron form. The folds have developed cleavage in the slate and in the siltstones and sandstones, although it is more widely spaced throughout the silt and sandstones. To the south, the cleavage dips at moderate low angles and the strata, which become overturned in places, dip steeply. The original direction of the strata can be established using the graded and cross-bedding of sedimentary structures. It demonstrates that the section is situated on the overturned, steep or northern limb of the Dartmouth Antiform, which can be traced from Newquay to Dartmouth.^[2] This is evidence a period of tectonic plate collision between 330 and 300 million years ago, which exerted pressure on the rock.^[1] Folds of three generations with cleavages are visible through the section in Bovisand Bay. Generally, the first generation folds have gently southern dipping limbs which are overturned or steep. The cleavage consistently dips about 40 degrees south. This indicates that this section has the Dartmouth Antiform passing through it.^[2] The far south consists of red and green slates with sandstones that were deposited in rivers and lakes.^[1]

On the western flank (Cornwall), there are harder rocks such as Staddon Grit, which form a headland from Staddon Point. There are also deposits of sandstones in the shape of marine sand bars. Along most of the coast dramatic faults and folds in the rocks can be seen and, in some places, a chevron pattern is visible.^[1]

References

^ ^a ^b ^c ^d "Geology to see in Southern Devon". Devon County Council. Retrieved 27 November 2008.
^ ^a ^b ^c "Plymouth Sound Shores and Cliffs" (pdf). english-nature.org. Retrieved 27 November 2008.

Wikimedia Commons has media related to Plymouth Sound, Shores And Cliffs.

v t e Biological Sites of Special Scientific Interest in Cornwall and the Isles of Scilly
Summary	Summarised data for all sites (biological and geological)
Cornwall	Aire Point to Carrick Du Amble Marshes Baulk Head to Mullion Bedruthan Steps and Park Head Boconnoc Park and Woods Bodmin Moor, North Borlasevath and Retallack Moor Boscastle to Widemouth Brendonmoor Breney Common Bude Coast Cabilla Manor Wood Caerthillian to Kennack Carnkief Pond Carrick Heaths Carricknath Point to Porthbean Beach Carrine Common & Penwethers Chyenhal Moor Cligga Head Coombe Mill Coverack to Porthoustock Crow's Nest Crowhill Valley Dozmary Pool Draynes Wood East Lizard Heathlands Eglarooze Cliff Gerrans Bay to Camels Cove Godrevy Head to St Agnes Goonhilly Downs Goss and Tregoss Moors Greenamoor Greenscoombe Wood, Luckett Grimscott Gwithian to Mexico Towans Hayle Estuary & Carrack Gladden Kelsey Head Kennack to Coverack Kernick and Ottery Meadows Loe Pool Loggans Moor Lower Bostraze and Leswidden Lower Fal & Helford Intertidal Lymsworthy Meadows Lynher Estuary Malpas Estuary Marazion Marsh Meddon Moor Meneage Coastal Section Merthen Wood Minster Church Mullion Cliff to Predannack Cliff Nance Wood Newlyn Downs Ottery Valley Park Wood Penhale Dunes Pentire Peninsula Phoenix United Mine Plymouth Sound Shores And Cliffs Polruan to Polperro Polyne Quarry Porthgwarra to Pordenack Point Rame Head & Whitsand Bay Red Moor Redlake Meadows & Hoggs Moor Retire Common River Camel Valley and Tributaries Rock Dunes Rosemullion Rosenannon Bog and Downs St Austell Clay Pits St John's Lake St Nectan's Glen Steeple Point to Marsland Mouth Swanpool Sylvia's Meadow Talland Barton Tamar–Tavy Estuary Tintagel Cliffs Treen Cliff Tregonetha & Belowda Downs Tregonning Hill Trehane Barton Trelow Downs Trevose Head and Constantine Bay Upper Fal Estuary and Woods Upper Fowey Valley Ventongimps Moor West Cornwall Bryophytes West Lizard
Isles of Scilly	Annet Big Pool and Browarth Point Castle Down (Tresco) Chapel Down Eastern Isles Great Pool Gugh Higher Moors and Porth Hellick Pool Lower Moors Norrard Rocks Peninnis Head Pentle Bay, Merrick And Round Islands Plains and Great Bay Pool Of Bryher & Popplestone Bank Rushy Bay and Heathy Hill Samson Shipman Head & Shipman Down St Helen's St Martin's Sedimentary Shore Teän Western Rocks White Island Wingletang Down
Neighbouring areas Sites of Special Scientific Interest in Devon Sites of Special Scientific Interest in Somerset

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