Berry Head to Sharkham point

Designations: SSSI, Proposed CGS/RIGS

Massively quarried limestone headland, a National Nature Reserve, stands 60 metres (200foot) above sea level guarding the Bay. High sea levels during the Quaternary cut this high level marine platform whilst later extensive marine caves developed. Within the quarry sandstone filled fissures (dykes) cut into the limestone evidence of deposition in the Permian. The site provides an excellent viewpoint from which to view Torbay.

GCR block / key theme: Marine Devonian, Mineralogy, Variscan structures of southwest England, Quaternary of south-west England, Caves and Karst.

Associated SSSI: Berry Head to Sharkham Point SSSI

Geological / geomorphological features: [Provisional] Marine Devonian: The coastline and adjacent disused quarries between Sharkham Point and Shoalstone Point on the north-west side of Berry Head, show a key section through the changing facies of the Middle Devonian ‘Brixham High', including stratotypes for the Sharkham Point and Berry Head members of the Brixham Limestone Formation and the St. Mary's Bay Member of the Nordon Formation. The Sharkham Point Member (early mid Eifelian) at its type locality includes slaty mudstones with thin beds of shelly crinoidal limestone below, passing upwards through levels with interbedded tuff to thin bedded limestones with abundant stromatoporoids. The Berry Head limestone sequence is then interrupted by a wedge of dark slaty mudrocks of the St. Mary's Bay Member of the Nordon Formation (late Eifelian-late Givetian), which at its type locality - St. Mary's Bay itself - includes thin seams and lenticles of limestone with a shelly fauna including brachiopods, small solitary corals and rare trilobites and cephalopods. Carbonate sedimentation resumes with the Berry Head Member of the Brixham Limestone Formation, well exposed around the Berry Head itself, its type locality, which, although locally showing signs of tectonic distortion, includes a range of facies including bioclastic and stromatoporoid rich levels indicating a reeflike biogenic bank complex.

Structural geology: The cliffs on the south side of Berry Head show spectacular structures in the Middle Devonian, Berry Head Member of the Brixham Limestone Formation, revealing several phases of deformation. These include gently inclined, northward verging, tight D1folds refolded by steeply inclined D2 folds.

Quaternary of south-west England,Caves and Karst: The Devonian limestones of Berry Head include a remarkably sequence of caves with associated deposits, some of which lie below present sea-level, ranging form -15 OD to +29 OD. The caves provide a unique record of marine transgression with 3 levels of horizontal passage development, at -2 to +2 m, +5 to 9 m and 22 to 29 m OD, clearly related to former sea level stands. The morphology of the caves is also typical of passage development at the boundary between fresh and saline waters. Cave sediments are extensive and speleothems have been dated using Uranium series methods, indicating ages between around 107,000 and 332,000 years for the caves.

Shoalstone Beach, to the west of Berry Head Quarry, where most of the caves have been recorded, includes a raised beach platform at +8.5 m O.D., clearly related to the intermediate level of cave development on Berry Head. The beach is marked by a cobble deposit suggesting an ancient storm deposit.

Reasons for proposal as a RIGS sites: Marine Devonian: The area is of prime importance for Middle Devonian stratigraphy and sedimentology, showing the development of carbonate facies associated with the ‘Brixham High'. It includes stratotypes for the Brixham Limestone Formation and three lithostratigraphical members: The Sharkham Point Member and Berry Head Member of the former formation and the St. Mary's Bay Member of the Nordon Formation. Accessible exposures, in particular in St Mary's Bay and around Shoalstone Point give the site a high educational value in addition to its scientific importance. [Brixham High: Brixham Limestone Formation, including Sharkham Point Member and Berry Head Member; Nordon Formation, St. Mary's Bay Member]

Structural geology: Although not easily accessible, these spectacular folds can be viewed from the south side of the Berry Head Fort, although binoculars are recommended. In this way the site can be incorporated into educational visits to the headland. The features exposed, however, are some of the most dramatic and important structural features in the district.

Quaternary of south-west England,Caves and Karst: The site is unique in the region, and similar features related to cave development under the influence of changes in sea-level in the Plymouth limestone are either inaccessible or have now been largely destroyed by development. The scientific value of the site is potentially national, although educational use is limited by health and safety considerations too viewing openings form a safe distance.