Geology

Dudley Zoo and Castle sit atop a unique and fascinating geological feature. The limestone of Castle Hill, and its sister, Wrens Nest Hill, Britain’s first national nature reserve for geology, are composed of a 420 million-year-old prehistoric seabed.

A record-breaking 186 type specimens have been found in Dudley, more than any other site in the British Isles. A type specimen is the fossil from which the original studies and naming of the species came and is an historical artefact in its own right. Dudley has 59 species found nowhere else in the world.

The fossils and rocks come from the Silurian Period when the Dudley area was a warm shallow tropical sea.

Dudley is a unique carbonate shelf ecosystem, frozen in time. Echinoderm faunas (sea lilies, cystoids and carpoids) like Dudley’s are found nowhere else and are important in the study of evolution. The Dudley specimens are recognised to be among the most perfectly preserved Silurian fossils in the world.

The fossil superstars of Dudley - a group of animals who were the first to develop high definition vision and the only animals the world has ever known to have eyes made of crystal are preserved in microscopic detail in Castle Hill, particularly in the walls of the Castle’s Sharrington Range.

These are the trilobites, a now extinct family distantly related to spiders and scorpions. Some of the best-preserved trilobites in the world are from Dudley and Calymene blumenbachii, is also known as the Dudley Bug.

Stores Cavern, beneath DZG’s chairlift, has in its roof a piece of seabed which records a terrible catastrophe when thousands of animals were buried under silt.

Among them was one of the world’s largest trilobites Trimerus delphinocephalus, the dolphin-headed trilobite, which has been found nowhere else in the world. In the cavern they are buried in shoals telling us that they were colonial animals like their namesakes, the dolphins, today.

The mines came close to the surface in areas and these eventually collapsed as crown-holes or crown-ins; 30 metre wide circular craters in the ground. These were used to create the animal enclosures when DZG was built in 1937.