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Petitor, MaidencombeDesignations: Proposed CGS/RIGS The site exposes section of both the Middle and Upper Devonina with Permain deposits resting unconformably on the Upper Devonian. Marbles quarried from here were very much in demand during the Victorian era. GCR block / key theme: Associated SSSI: Not applicable Geological / geomorphological features: [Provisional] Marine Devonian: The site includes the disused Petit Tor Quarry and adjacent coastal exposures dominated by pale stromatoporoid-rich limestones of the Walls Hill Member of the Torquay Limestone Formation (Givetian), overlain to the north by reddish shales of the Saltern Cove Formation (Frasnian). The limestones also yield a scattered fauna of rugose and tabulate corals and a middle varcus Biozone conodont fauna, have a solution cavities in their upper surface which occasionally contain pale-pink flinty or slaty limestones or slates. The latter have been interpreted as an Upper Devonian infill and have been reported to have formerly yielded orthocone cephalopods. The overlying mudstones of the Saltern Formation show deformation but apparently include a basal red nodular limestone level with Frasnian conodonts and very rare ammonoids; they are in turn overlain, unconformably, by a limestone breccia at the base of the Watcombe Formation, the Petit Tor Member. Permian: The area shows a virtually unbroken sequence through the upper sequence of Permian deposits in the area, belonging to the Watcombe, Oddicombe and Teignmouth Breccia Formations. The sequence rests unconformably on Upper Devonian Saltern Cove Formation, the contact being marked by the coarse limestone breccias of the Petit Tor Member, at its type locality. This unit includes limestone blocks up to several metres across in a pebbly and sandy matrix; it is interpreted as a local talus deposit. Higher levels in the formation include muddy siltstone with sand and fine breccia below with mudstone and siltsone above - these relatively soft lithologies give rise to large landslip systems immediately north of Petit Tor. The succeeding Oddicombe Breccia Formation includes rounded clasts dominated by Devonian limestone with some Carboniferous sandstone and other rocks in a silty-sand matrix and passes laterally, northwards into the Teignmouth Breccia Formation. Reasons for proposal as a CGS / RIGS sites: Marine Devonian: The Petit Tor area shows the final stages of evolution of the Middle Devonian ‘Torquay High', with the apparent development of palaeo-karstic surfaces at the top of the Torquay Limestone Formation, infilled with Frasnian sediments. Stratigraphical evidence also supports an intra-Devonian non-sequence, with the Barton Member being absent and the Saltern Cove Formation apparently resting directly on the Wall's Hill Member of the Torquay Limestone Formation. The area is of potential educational value. Permian: The site shows the lowest part of the upper Permian sequence of Torbay, separated by a non-sequence from the distinct Torbay Breccia Formation sequence below. It includes the stratotype of the Watcombe Formation, with the Petit Tor Member at its base, and key exposures of the conformable passage into the Oddicombe Breccia Formation above. Exposures are in places readily accessible and therefore have educational potential. [Exeter Group: Watcombe Formation (including Petit Tor Member), Oddicombe Breccia Formation, Teignmouth Breccia Formation] |