Key Sites - West Oxfordshire
Key geological sites: West Oxfordshire.
These are the geological SSSI sites to be found within the civil administrative boundaries of West Oxfordshire District Council.
The geology of the district youngs south-eastward and comprises rocks of Lower & Upper Jurassic & Quaternary.
There are seven 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.
Ditchley Road (Town Quarry) SP 370 200
Ditchley Road Quarry (12.2 ha) shows a rock succession from the Bajocian Clypeus Grit up to the basal Taynton Limestone (progracilis Zone, Middle Bathonian) and has been designated a SSSI since 1986. Above the fossil-bearing limestones of the Clypeus Grit occurs the best complete (6 metres thick) section of Chipping Norton Limestone in Oxfordshire. The fossil rootlets present in the top of the Chipping Norton Limestone here are significant because they lend support to a proposed 'event correlation' of the Chipping Norton Formation with the extensively rootletted muds and sands of the Stamford Member (Rutland Formation) of Northamptonshire. This exposure of Chipping Norton Limestone is vital for our understanding of the types of environments prevalent across this part of the south Midlands during Lower Bathonian times.
The quarry is also important in interpreting the lateral lithological changes that occur in the stratigraphic level of the Sharp's Hill Formation, since it lies geographically between typelocality and the problematic Stonesfield area.
Horsehay Quarries SP 456273 & SP 456276
The Horsehay Quarries, an 8.2 ha site and SSSI since 1972, show an important rock section of the Middle Jurassic, from the Northampton Sand Formation (Aalenian) up to the Taynton Limestone Formation (Middle Bathonian). The section includes the best exposure of the 'White Sands' facies of north Oxfordshire; these 'sands' were previously assigned to various stratigraphic horizons, but dating using the analysis of fossil pollen from these strata now proves that they belong within the Chipping Norton Formation (late Bajocian to early Bathonian). This exposure is ideally situated for demonstrating facies relationships both within the Chipping Norton Formation and between the formation and the laterally equivalent Stamford Member (Rutland Formation).
The fossiliferous exposures of the whole of the Sharp's Hill Formation are important for exhibiting changes that occur between the type-section to the north and the more southerly exposures at Stonesfield and Charlbury.
Long Hanborough Pit SP 419137
This 4.3 ha site has been a SSSI since 1972 and provides exposures in the gravel of the Pleistocene Hanborough Terrace of the Evenlode Valley, for which it may be considered the type site. The deposits have yielded molluscan fossils indicative of a cold environment and vertebrate remains which suggest warmer conditions. Rare Palaeolithic hand axes have also been found in the Hanborough Terrace gravel. Exceptional examples of ice wedge casts occur, particularly at the northern end of the site.
As the last remaining exposures of the gravels underlying the Long Hanborough area, this site is of considerable scientific importance in studies of the terraces and evolution of the Thames.
Shipton-on-Cherwell & Whitehall Farm quarries SP 478186
This 27.65 ha SSI (since 1986) comprises two quarries. The Shipton-on-Cherwell Quarry currently exposes a section from near the base of the White Limestone (including the type section of the Shipton Member) up to the Lower Cornbrash; it is one of the most important sections in Oxfordshire for displaying the typical local Mid to Upper Bathonian lithostratigraphic succession. The highly fossiliferous Shipton Member of the White Limestone is well displayed at Whitehill Farm Quarry. This quarry in addition displays large-scale cross-bedding in the overlying Ardley Member (not seen at Shipton), formed by storm-moved shelly-oolite shoals in a 'lagoonal' setting. These two localities illustrate the considerable variation in facies within the White Limestone locally, and they have been critical in palaeoecological, sedimentological and general facies studies of the White Limestone of central and eastern England. Shipton may be regarded as the type-section of the laterally extensive Forest Marble, and is undoubtedly the best location in the country for examining the rapid lateral facies changes seen within this formation; elsewhere the complex inter-relationship between oolitic/bioclastic sand-shoals and inter-shoal, slack-water muds which characterises the Forest Marble of the area is inadequately displayed. Some of the Forest Marble at Shipton contains transported elements of the diverse 'Bradfordian' fauna but much of it is unfossiliferous, although the trace fossil Gyrochorte occurs frequently. The Forest Marble here has been the subject of exhaustive sedimentological study. The fossiliferous Lower Cornbrash, thickly developed at Shipton, is characteristic of the Lower Cornbrash of much of Oxfordshire.
The northern corner of Shipton-on-Cherwell Quarry has been well known for its fossil reptiles since 1820. It has yielded fine cranial remains of 5 or more long-snouted crocodiles (Steneosaurus, Teleosaurus) including type material of two species, from the fimbriatus-waltoni beds, and other units near the top of the White Limestone Formation. The type specimen of the dinosaur Dacentrurus vetustus (from the Lower Cornbrash here) is one of the earliest Stegosaurs known. Shipton-on-Cherwell Quarry has yielded the best extant collection of Middle Jurassic crocodiles in the world. It is of international importance as one of the best Upper Bathonian reptile sites known.
Stanton Harcourt SP 414051
The gravel deposits, near Stanton Harcourt, represent the Pleistocene Summertown-Radley Terrace of the UpperThames. Important evidence of periglacial conditions has been demonstrated in these deposits, including large and complex ice wedge casts and a widespread cryoturbated horizon. Silt lenses within the gravels have yielded molluscs indicative of cold conditions. However, beneath these cold-climate deposits, an extremely important and localised interglacial deposit has been uncovered, occupying a channel cut into the Oxford Clay bedrock. The channel contains clastic and organic sediments which have yielded a varied vertebrate fauna, wood and other plant remains, and a rich molluscan fauna of warm climatic affinities. The relationship between these interglacial sediments and other warm climate deposits in the upper levels of the Summertown-Radley Terrace nearby is by no means clear, although it has been suggested that a hitherto unrecognised stage is represented at Stanton Harcourt. The 0.68 ha site thus provides a major reserve of this terrace and its fossiliferous deposits, on which further work is needed, and for which the deposits here are of prime importance and has been a SSI since 1990.
Stonesfield Slate Mines SP 392172, 388168, 379173 & 387171
The old mines situated at four localities around the village of Stonesfield (cited as SSSI since 1955) form the type-locality of the Stonesfield Slates, which are now generally believed to be developed within, and probably towards, the base of the Taynton Formation in a limited area around Stonesfield. They represent a localised facies, consisting of variably oolitic, very fine quartzose sand, which was probably deposited in a shallow marine environment during the early stages of the Taynton Limestone transgression. Besides yielding important Bathonian floras and invertebrate faunas, the Stonesfield Slates have also provided bio-stratographers with a number of ammonites, generally extremely rare at this stratigraphic level on the 'Cotswold Shelf'; these include large perisphinctids, the earliest British Clydoniceras and Micromphalites micromphalus. The Progracilis Zone was, in part, based upon the Stonesfield ammonites, the fauna from here being richer in numbers of species and genera than comparable faunas from the Cotswold Slates of Eyford.
The mines are one of the world's most famous vertebrate fossil sites. They have yielded abundant remains of plesiosaurs, marine crocodiles, dinosaurs, pterosaurs, turtles and mammal-like reptiles (ictidosaurs). These occur as well preserved teeth, scutes, limb elements and vertebrae. The remains of the dinosaurs Megalosaurus (type specimen) and Iliosuchus (type specimen), the crocodile Steneosaurus, the pterosaur Rhamphocephalus and the ictidosaur Stereognathus (type specimen) are particularly important. Historically, this is the richest Middle Jurassic reptile site in Britain, and the locality where William Buckland obtained the first dinosaur, Megalosaurus Bucklandii, ever to be recognised and described.
The Stonesfield Slate here also yielded in 1812 the first known pre-Tertiary mammals. Buckland's realisation that these mammals were the contemporaries of the dinosaurs was the cause of a major controversy in the early 19th century. Two species of triconodont and one eupanthothere have been recorded.
This locality is one of the classic sites for studies of fossil insects. One particularly famous specimen from here was originally described as the earliest butterfly. This is now known to be a bug, and a member of an extinct group of insects present in Jurassic and Cretaceous rocks. Other insects present include large beetles and important dragonflies.
A diverse flora of over 20 species has been found here. It is dominated by Pteridospermales, Cycadales and Bennettitales, with some Coniferales and Ginkgoales. There is also the enigmatic 'Phyllites sp.', which looks remarkably like an angiosperm leaf. If confirmed this would be the oldest angiosperm fossil (other than pollen) known from anywhere in the world. The overall composition of the flora compares broadly with the well-known Yorkshire floras of the same age, but there are several forms unique to Stonesfield, such as Sphenozamites belli and Podozamitaaes stonesfieldensis. This is clearly a site of considerable importance for Middle Jurassic palaeobotany.
Wychwood SP 332158
A 530.5 ha site, Wychwood Forest occupies a limestone plateau dissected by an easterly flowing tributary of the River Evenlode, which has cut through a sequence of Jurassic rocks. The valley floor rests upon Upper Lias Clays, obscured by a cover of recent alluvium. In the valley sides the clays are overlain by oolitic marls and limestones of the Inferior Oolite Series; springs emerge at the junction of these two rocks. Above this lies the sandy and marly limestone of the Great Oolite which forms much of the plateau. Despite the complex geology the formations vary little in lithology, and have eroded to produce a remarkably uniform soil of the Elmton 1 series, consisting of well-drained, brashy, calcareous, fine loams, with only minor extents of shallow and gleyed variants.
There are four shallow marl ponds, spring-fed from underlying limestones and with cold, clear water rich in dissolved lime. Such pools are nationally rare and these are the only substantial water bodies on the southern Jurassic limestone.
Wychwood was SSSI notified in 1975 for its geological and biological interest.