Devon County Geological Site

Site reference no. SX55SE5 Name: New England Quarry

District: South Hams Parish: Yealmpton

National grid ref: 598543 (entrance) OS sheets: 1:50k 202 1:25k 1356 1:10k SX55SE GS 1:50k 349 GridRef x y Lat Long SX595545 259500 54500 50.373575 -3.977174

Locality description (address): New England Quarry, Popples Bridge, Yealmpton.

Nature of site: Quarry medium/large, dormant at time of assessment.

Geological / geomorphological features: Gabbro intrusion into Middle Devonian Slate. The gabbro has undergone limited deformation in the interior of the mass and original ophitic and ophimottled igneous textures and mineralogy are preserved in parts. movement within the mass has been concentrated along or near joints often with the production of slickensides. Metasomatic alteration tends to be concentrated along the joints and tension gashes. Epidote, fibrous tremolite with some calcite and dolomite are commonly present with some patchy replacement by epidote in the mass of the rock. Bluish platy films may be serpentine minerals. Shearing, particularly at the contact, and locally within the mass of the rock has produced a foliation, seen striking 0570 and dipping 720 SE, with alteration of mafic minerals to chlorite. Exposures of the contact, between gabbro and slate are seen on the stripped surface west of the quarry. The main northern contact, lying closely parallel to the cleavage in the slate, strikes 0500 and dips steeply, it may be slightly faulted. The contact is complex in detail with the gabbro interfingering with the slate. The zone of contact alteration about 0.75m wide is indicated by bleaching of the slate, crinoid ossicles in this zone are replaced by chlorite. Along part of the western edge of the stripped surface the cleavage in the light grey slates strikes about 0400 with a steep dip SSE. They are also fossiliferous with brachiopods crinoid stem fragments and isolated ossicles and bryzoans. Where less weathered, the crinoids still consist of calcite. Faults cutting the intrusion include; a low angle, SSW dipping fault strikes across the second level on the west side of the quarry. It is displaced by a steep fault zone trending c.1350 , possibly with multiple movement, up to 0.3m wide associated with quartz, hematitic films and an ankeritic carbonate cemented breccia. The fault is associated with a wide zone of intense ferruginous weathering and alteration on the upper level of the quarry. Some other steeply dipping, orange weathering, ankeritic carbonate veins cut the gabbro. The top of the gabbro is spheroidally-weathered to a depth of 10m and possibly 20m in places.

Reasons for registration as a Regionally Important Geological / Geomorphological Site: The quarry provides an excellent demonstration of the response of a massive gabbro intrusion to regional tectonism and low grade regional metamorphism. It also shows the a good example of a weathering profile on gabbro.

Site sensitivity: None. Features currently visible are subject to future quarry development.

Safety: Quarry regulations apply. An indemnity will be required and safety helmets and suitable footwear are a necessity. There is loose rock on the quarry faces which must be avoided. Care is needed on loose rock lying on the quarry benches. The lowest level is flooded.

Interest groups: Schools. Years 5-11: Years 12-16: Years 17-18. University. Undergraduate - Research Professional geologists - Amateur geological groups - General public.

Access and Parking: Access on foot from quarry entrance. Parking for all types of vehicles at quarry.

Date of assessment (V = visited) : V 19th October 1995 R T Taylor

Site owner : CAMAS Aggregates Ltd., For access contact: The Quarries Manager, CAMAS Aggregates, Moorecroft, Billacombe, Plymouth, Devon. PL9 8AJ

Other comments: Although the quarry is likely to continue to be worked, the range of excellent geological features displayed qualifies the site for registration as a County Geological Site. Conservation of geological interest should be considered in any ongoing or final planning process for the site. There may be some need to modify existing plans for restoration of the site.