Stonesfield Slate Mines

Also within

Oxfordshire County Cotswolds Scenic Area

Condition (Natural England)

Geology & landscape

Geological Period: Cretaceous, Jurassic · Rock Type: Limestone, Slate

Description

Area, 0.76 hectares 1.88 ac Description The old mines situated at four localities around the village of Stonesfield 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, the richest Middle Jurassic reptile site in Britain and the locality where William Buckland obtained the first dinosaur, Megalosaurus, 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.