Key Sites-Vale of White Horse
Key geological sites: Vale of White Horse.
These are the geological SSSI sites to be found within the civil administrative boundaries of Vale of White Horse District Council.
The geology of the district youngs south-eastward and comprises rocks of Upper Jurassic, Lower Cretaceous, Upper Cretaceous, Palaeogene & Quaternary.
There are eight sites in the district designated as Sites of Special Scientific Interest (SSSI).
Please note that listing on this page does not imply that public access is freely available or has been given. Most sites are not accessible because they are on private land or they may be unsafe. Permission must be sought from the landowner before a visit.
Cumnor (Bradley Farm or Rockley) Quarry SP 604 0325-4618 0324
This Late Jurassic, 0.2 ha locality exposes an attenuated Corallian succession spanning the complex Lower and Middle Oxfordian cordatum-tenuiserratum zone time interval and has been a SSSI since 1990. The sequence exposes the Lower Calcareous Grit and the Natica Band, which are overlain non-sequentially by the Osmington Oolite including the Pebble Bed, Third Trigonia Bed and Coral Rag.
This site is remarkable for the absence of any part of the Highworth Formation, and consequently shows the greatest observed attenuation of that formation (Lower Trigonia Bed-Highworth Grit) anywhere in south-west Oxfordshire. The locality is also of key palaeogeographic value as one of the few remaining outcrops in the (tenuiserratum zone) Coral Rag of the Cumnor Reef. A rich ammonite fauna has been collected here, especially from the Natica Band and condensed Pebble Bed. A total of seven ammonite species of the genera Perisphinctes, Aspidoceras, Goliathiceras and Cardioceras have been recorded here including the Middle Oxfordian zonal index Cardioceras densiplicatum and the holotypes of Perisphinctes cumnorensis and Goliathiceras titan. This is an outstanding site demonstrating the complex biostratigraphy and palaeogeography of the Oxfordshire Corallian.
Dry Sandford (Cothill Quarry) Pit SU467995
This site 4 ha site has been a SSSI since 1950 and is now a BBOWT nature reserve. The exposures at Dry Sandford Pit are of Middle Oxfordian Stage (Late Jurassic) deposited circa 140 million years ago, in shallow coastal waters close to coral reefs. The Oxfordian succession seen here comprises two main units:
The Stanford Formation (Coral Rag Formation)
The Kingston Formation (Beckley Sands Member)
The upper units of the Highworth Grit Formation (the upper Trigonia Bed, Pusey Flags and Highworth Grit and Clay) are missing at Dry Sandford, indicating that a major period of erosion took place in this area during the deposition of the Oxfordshire Corallian Beds. With the exception of the Urchin Marl and the Coral Rag, these beds contain a rich and important fauna of fossil ammonites.
The middle Oxfordian Stage is sub-divided into two ammonite time zones, each defined by the occurrence of a diagnostic species. One zone is characterised by Cardioceras densiplicatum and the other zone by Cardioceras tenuiserratum. As both ammonite zones are represented at Dry Sandford Pit the site is regarded as scientifically invaluable, local and national middle Oxfordian reference section.
Dry Sandford Pit is accessible to the public.
BBOWT nature reserve.
The site is well-managed and a reasonable expanse of the exposure is free of vegetation.
The exposures are prone to failure & collapse.
Hurst Hill SP477043
This 20.6 ha site has been a SSI since 1950. The old brickpits which lie to the west of Hurst Hill summit have yielded a typical Kimmeridgian selection of marine reptiles, such as ichthyosaurs (2 species), plesiosaurs (remains possibly relating to 2 species) and pliosaurs (2 species). In addition, the very fine skeleton of the ornithopod dinosaur Cumnoria prestwichii came from Chawley. The discovery and taphonomy of the specimen have been described in detail. C. prestwichii is the only valid European species of this typically North African genus and provides important evidence for the existence of land links across the narrow proto-Atlantic in the late Jurassic period. C. prestwichii is one of only two known Upper Jurassic ornithopod skeletons from Europe, and the Chawley site is clearly a unique reptile locality in the European Jurassic.
Lamb and Flag Quarry SU380974
At this 0.16 ha site, a section is present through the Highworth Formation from the Pebble Bed to the Pusey Flags, overlying the Lower Calcareous Grit. A particularly rich perisphinctid ammonite faunal assemblage (especially in the Trigonia bed) are important in the correlation of the middle Oxfordian. This is a key site noteworthy for its Cardioceras densiplicatum zone ammonites which are vital in any stratigraphic analysis of the complex Wiltshire-Oxfordshire Corallian outcrops. This site was designated a SSSI in 1986.
Shellingford Crossroads Quarry SU326942
This SSSI (since 1954) within its 2.6 ha is an outstanding extensive section in Corrallian rocks of Oxfordian age spanning the Highworth Grit, Third Trigonia Bed, Urchin Marls and Coral Rag. The latter unit is well known for its abundant in situ coral growths and reef-dwelling bivalves, but the site is equally important for its illustration of the complexities of Oxfordian stratigraphy in the Oxford area, and in showing the best available section through the Highworth Grit-Coral Rag rock interval. The pebble bed immediately above the Grit marks a significant and widespread regional non-sequence pre-dating a period of oolitic limestone deposition which can be correlated with the Osmington Oolite of Dorset.
Sugworth SP 513008
This 0.6 ha site at Sugworth has been a SSSI since 1986. Sections here have revealed an early Middle Pleistocene interglacial section of very great importance. A Pleistocene fluvial channel cut into the much older Jurassic Kimmeridge Clay contains sediments in which vertebrates, ostracods, molluscs, beetles, plant remains and pollen have all been preserved. These interglacial sediments have been attributed to the Cromerian Interglacial, although this dating has been the subject of recent controversy, and some reassessment may be required. Early interglacial deposits of this type are extremely rare inland in Britain. Sugworth is at present the only presumed Cromerian site associated with Thames deposits, and it is therefore a locality of major significance.
White Horse Hill SU 302868
The 103.2 ha White Horse Hill has been a SSSI since 1954 for its geographical, geomorphological and biological interest. The site covers the deep coombe of the Manger cut into the scarp face of the chalk escarpment where it rises to a crest at Whitehorse Hill and is representative of so many chalk coombes in the south of England.
The scarp face below Whitehorse Hill is formed of Lower and Middle Chalk overlying the thin Upper Greensand, with Gault Clay flooring the valley to the north. The steep chalk slope is scored along much of its length by dry coombes, and one of the most spectacular is The Manger which is on a fine example of the most distinctive landform of English chalk karst. The Manger coombe is a rounded, totally dry valley 500 m long and over 50m deep. Its western side is scored by more than 10 tributary coombes each incised about 5 m into the main coombe slope.
Within The Manger bedrock is overlain by chalk silts and rubble up to 5 m thick, capped by brown humic chalk silts up to 3 m thick, with an upper layer of topsoil supporting sheepwalk grassland. Though there is no surviving evidence of pre-Devensian erosion, the scale of the coombe and the known Devensian sediments provide evidence of solifluction excavation during at least one cold stage of the Pleistocene. The existing dry coombe is evidence of the karstic fossilisation, by underground drainage, of a landform excavated under contrasting climatic conditions.
Wicklesham & Coxwell Pits SP 513008
The area covered by this SSSI (first cited in 1950) is 12.79 ha in area. The active quarry and disused pits within this site provide good exposures through the Faringdon Sponge gravels of Lower Cretaceous (Aptian) age. The gravels, laid down under marine conditions some 110 million years ago, are unique to the Faringdon area, and were deposited in an unusual and very localised near-shore sedimentary environment. They contain a very rich and unusual assemblage of fossil sponges, bryozoa, brachiopods and echinoids, with over 150 different species having been found here; many of these are known to occur only at Faringdon. In addition, the Faringdon Sponge Gravels have yielded bones from several different kinds of fossil reptiles (including turtles, ichthyosaurs, plesiosaurs and crocodiles) and Wicklesham Pit is of particular significance as a source of such material. This site is of great historical importance, and is one of Britain's richest palaeontological localities.