Rock Edge (Crossroads or Windmill Quarry)
The clay layer has eroded back, so the limestone layer above juts out
It was formerly known as the Crossroads Pit, as it stood at the important junction where Old Road (the main route to London until the late eighteenth century) crossed the road from the village of Cowley to that of Old Headington. It was also sometimes called the Windmill Quarry, as it was just to the south of Headington's main windmill.
The two maps below show how the land around the quarry was built up between 1876 and 1939.
The “New Headington and Headington Stone Quarry” belonging to Messrs. George and John Snow that was advertised for sale by auction in Jackson's Oxford Journal on 21 June 1856 is likely to be this pit, as no other quarries were in the New Headington area.
Geology of Rock Edge
The cliff of the pit at Rock Edge has exposures of Upper Jurassic limestone, laid down about 160 million years ago. This pit is thought to have been a former boundary between a coral reef and the surrounding shallow sea, and therre are many fragments of coral and fossils including sea urchins.
South end of the exposure (closer Old Road): The limestone here is Coral Rag, made up of coarse fragments that broke off the reef: it is very rubbly and contains many coral and shell fossils.
North end of the exposure (closest to York Road): The limestone here is Wheatley limestone, made up of material that washed off the reef, and the fossils are smaller and more fragmented.
Right A fine coral head at Rock Edge. Coral heads consist of accumulations of individual animals called polyps, arranged in diverse shapes. The coral reef at Headington would have been a patch reef, which is comparatively small reef outcrop
Below: Isastraea coral at Rock Edge
Other corals to be found at Rock Edge include Thamnastria, Thecosmilia, and pecten shells (scallops).
Friends of Lye Valley and the conservation of Rock Edge
The Friends of Lye Valley work with Oxford City Council in the management of Rock Edge, and run joint conservation work parties and family fossil events in conjunction with the Oxfordshire Geology Trust: