Much of southern Warwickshire is underlain by layers of clay, limestone, sandstone and ironstone dating back to the Jurassic Period. The rock beds are occasionally seen in quarries, road cuttings and other excavations. Harder rocks such as limestones and ironstones tend to cap hills and ridges. Examples include the Burton Dassett Hills and Edge Hill. Limestones can be seen at Cross Hands Quarry. The softer clays form lowlands.
| 
Ammonite fossil from
Shipston on Stour
| Warwickshire's Jurassic rocks formed between about 200 and 170 million years ago as layers of mud and sand in warm, shallow seas. These covered much of central England at that time. The fossils found in the Jurassic rocks are the remains of creatures that lived in the ancient seas. The shells of ammonites and other sea-creatures including Devils' toenails are the most familiar. Bullet-like belemnites represent the internal shell of extinct squid-like animals. |
Belemnite fossils in
Jurassic ironstone
at Edge Hill
(pen for scale).
Geologists refer to
these fossil beds as
'belemnite battlefields' | Clay and limestone beds, termed 'Blue Lias', are still quarried for Rugby Cement at Southam. In the past these beds yielded the skeletons of ichthyosaurs and plesiosaurs - real Jurassic sea-dragons. The Hornton Stone is slightly younger than the Blue Lias. It is a bed of rusty ironstone, quarried for building stone around Edge Hill. We now know that this rock formed as iron-rich sand in a shallow current-swept coastal area. The iron appears to indicate the former presence of rusty-coloured tropical soil on nearby Jurassic islands. | |