Bucks Earth Heritage Group

Oxford Clay

The Oxford Clay has long been known for its reptiles such as plesiosaurs and ichthyosaurs, but also for its abundant ammonites and the distinctive shells of Gryphaea, also known as the 'Devil's Toenail'. Exposure of this clay was excellent in the brick pits of the mid-northern part of the county. The Oxford Clay represents a deepening sea of around 160 million years ago.

The Devil's toenail, otherwise known as Gryphaea. This genus evolved over the Oxfordian period to assume difference shapes.

This Gryphaea has acquired serpulid worm tubes

An Oxford Clay belemnite (see the Gault for a reconstruction)

Oxford Clay ammonite with shell wearing through to show the internal sutures

Oxford Clay ammonites embedded in the clay

Oxford Clay paddle bone from a Plesiosaur