[3] This site is described by Natural England as "important for its excellent exposures of Totternhoe Stone", dating to the mid-Cenomanian stage of the Cretaceous period, around 100 million years ago.

It has yielded many fossils of ammonites from the Lower and Middle Chalk.

Much of the former chalk pit is flooded and now known as Old Kiln Lakes.

In the summer of 2012 the public was warned to stay away and not swim in the lakes.

[5] However, fish including carp and tench have lived in the lake, and since the late 20th century a Chinnor Works Angling Society has had permission to fish the lakes.