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Geology of Wren's Nest National Nature Reserve

Declared a National Nature Reserve in 1956, Wren's Nest has exceptional geological and palaeontological features of Silurian age (approximately 420 million years ago). This was the UK's first ever geological national nature reserve.

The area was formerly quarried and mined for two thick layers of pure limestone. This ceased in 1925 and the site was abandoned. Since this time much of the site has been re-vegetated naturally to create a green geological haven and recreational area enjoyed by local residents and visitors alike.

The old rock faces of the quarries provide a unique 'outdoor teaching facility' for field geology and geological research and a number of geological trails have been established at the 100-acre site since 1956. The site provides a definitive section through the Much Wenlock Limestone formation of Britain which are exceptionally rich in marine invertebrate fossils with a host of associated structural and sedimentological features to challenge students of all levels of knowledge.

The site also has a long and very important social history. This includes being the birthplace of Abraham Darby (the so-called father of the industrial revolution), important associations with visiting scientists such as Sir Roderick Murchison and his defining work 'The Silurian System' published in 1839 in which 65% of the Wenlock fossils illustrated were from Dudley, and limestone mining industries features of which including mine entrances occur on the site.

In addition to the geological features of the site, a special limestone fauna and flora has established itself at the site in the years since the mining and quarrying has ceased. This includes many species of plants, invertebrates and several species of bat over winter in the caverns.

To obtain details of the current way marked geological trails, restrictions relating to visits and fossil collecting at the site or to obtain printed information please visit the Dudley Museum at the archives.  For more specific enquiries about the Nature Reserve please contact the Warden service.

Did you know?

  • Wren's Nest was the birthplace of Abraham Darby, the father of the industrial revolution
  • Wren's Nest is nationally important for hibernating bats
  • You can find more than 700 types of fossil at the site
  • Wren's Nest supports many wild flowers that are otherwise rare or absent in the West Midlands

Seven Sisters Mine

The Seven Sisters Mine (Upper Gallery) is thought to be the last remaining surface limestone mine of it’s kind left in Europe and possibly the world, making them a unique and internationally important heritage feature.

These surface entrances are key to understanding the methods of limestone extraction employed at the site in previous centuries. The pillars supporting the mine entrances contain notable patch-reef structures of high palaeontological importance and are a key feature in terms of designation of the National Nature Reserve.

In October 2001 a major roof collapse occurred. Funding from the English Partnerships Land Stabilisation Programme was secured to fill in the lower caverns and to temporarily fill the upper daylight gallery with stone to protect it from further collapse.


Fossils are the remains or traces of ancient life.  Fossils can be mineralised bones, teeth, shells, wood, material from an animal such as fur or eggs, footprints, leaf impressions or burrows.

Types of Fossil found at Wren's Nest

There were many different types of corals in the reef including Favosites and Halysites.

  • Crinoids or sea lilies grew in sheltered areas behind the main reef in patches of sand or soft sediment. Crinoids still live in the seas today but are rarer than they were in Silurian times.
  • Trilobites are probably the most famous fossil found on Wren’s Nest. Calymene blumenbachii was so commonly found by the quarry men in the 19th century that it became known as the ‘Dudley Locust’ or the ‘Dudley Bug’ and was incorporated into the town’s coat-of-arms as a symbol of the limestone mining industry.  Another common trilobite is Dalmanites. Trilobites were arthropods, related to modern crabs and lobsters and probably grazed on plants for food.
  • Some of the easiest fossils to find on Wren’s Nest are brachiopods, such as Atrypa, Strophonella and Leptaena. You can also find bivalves, like Goniophora and Pteronitella.
  • Other animals that lived on the reef included gastropods (sea snails) and Orthoceras, relatives of modern day squids and cuttlefish.

How do I look for Fossils?

Looking for fossils can often be difficult and time consuming. Luckily at Wren’s Nest, there are so many that you will easily find something to take home with you.

Here are some tips of how to look for fossils

  • Take your time and look at the loose material on the ground. Remember do not use hammers or other tools on the rock faces
  • Look for unusual shapes and textures
  • You are likely to only find part of a fossil, so make sure that you download the sheet at the bottom of the page to familiarise yourself with what they might look like
  • Only take a few fossils at any one time – you can always come back!
  • Use the footpaths and do not enter the safety fences
  • Remember to record that your fossils came from Wren’s Nest, Dudley

Murchisons viewpoint

At the southern tip of Wren's Nest Nature Reserve you will find one of its most impressive locations - Murchisons viewpoint, named after renowned geologist, Sir Roderick Murchison.

Murchison was a retired soldier who under the persuasion of his family became interested in Geology.  Murchison defined the period of geological time known as the 'Silurian' and his book 'The Silurian System' published in 1839 was based on the study of Dudley fossils. About 65% of the fossils illustrated and described in the book are from Dudley, and many of the individual specimens used are housed in the collection at Dudley Museum.

Murchisons viewpoint - Graham Worton, Borough Geologist and Keeper of Geology at Dudley Museum.

Ripple Beds - Dudley's very own beach!

The hill was once the bottom of the Silurian sea that stretched across the entire area, 428 million years ago.  The lumps and bumps on the surface are actually underwater ripple marks, similar to the ones you find on the beach today when the tide has gone out.  They formed as a result of massive storms sweeping across the sea, the waves of which penetrated deep into the sand, picking it up and moving it back and forth to create symmetrical ripple marks. 

The rippled surface provided an ideal surface for crinoids (sea lilies) to live on.  At some point after a large amount of mud was washed into the area, burying the crinoids and the ripples they were attached to, preserving them forever. 

25 individual ripple bed layers have been identified in this cliff, each representing a separate storm event. 

How was the hill formed? 

Fast forward a few million years and the continent upon which the Dudley area was part of was being subjected to mighty forces. Continents collided with other continents creating vast mountain chains as a result, this sea bed was forced upwards and creased into folds. These folds and the ripple beds we enjoy today were revealed during the industrial revolution following quarrying and mining of limestone at Wren's Nest.

Want to know more? To find out more information and to learn how to look after your Fossils visit Geology matters.