Field Trip to Wren S Nest and Dudley Limestone Caverns, 28 April 2012

Field trip to Wren’s Nest and Dudley Limestone Caverns, 28 April 2012. Sandra Morgan On 28 April, 22 participants arrived for this field trip, which was in two parts: in the morning we had an excellent walk around Wren’s Nest nature reserve led by Graham Worton, Keeper of Geology at Dudley Museum and Art Gallery, and in the afternoon we took an interesting canal boat trip run by Dudley Canal Trust into the Dudley limestone caverns.

Wren's Nest became the UK’s first National Nature Reserve for geology in 1956, in recognition of its exceptional geological and palaeontological features. It was also recognised as a Site of Special Scientific Interest in 1990. Graham talked about the challenges of conservation (not preservation). He also emphasised the need to work with the local community, and showed us a mosaic made by local children to represent their experience of Wren’s Nest as part of the Wren’s Nest 50th Anniversary celebrations.

Wren’s Nest is composed of Wenlock limestone deposited in the Silurian period when a warm shallow sea covered the area. It is rich in fossils – over 700 types of fossil have been found on the site, the most famous being the “Dudley Bug” trilobite.

Wren’s Nest coral reef where many examples of fossils are found

Although Wren’s Nest is most famous for trilobite fossils, there are many other interesting geological features. Right, Graham points out a layer of yellow volcanic ash. It is likely that this ash travelled 50-100 miles from a “nearby” volcano which may have been located in the Cheltenham area.

Graham shows us a layer of volcanic ash

Wren’s Nest also has an excellent example of ripple beds. Now tilted almost vertical, these two layers of ripple beds show ripples of different heights and wavelengths.

Ripple beds We learned a little about the wildlife of the area (seven different species of bat hibernate in the underground caverns), and finished our visit to Wren’s Nest with a little fossil hunting. We found many fossils, including brachiopods, crinoids, corals and bryozoans, but trilobites proved more elusive!

Some fossil finds from Wren’s Nest

The afternoon session began at Dudley Canal Basin, where we boarded our barge for a trip which took us under the area we had earlier explored on foot. The 45 minute trip took us through tunnels and through caverns excavated during limestone mining. The earliest part of the canal, Lord Ward’s tunnel, was constructed in the late 18th century to transport the limestone to Lord Ward’s colliery and lime works at Tipton. This early tunnel eventually collapsed and was bypassed by a Victorian tunnel, and two additional tunnels were opened in 1989.

Entrance to Dudley canal tunnel

We experienced both the Victorian and the modern tunnels and were informed about the history of the site by the knowledgeable boat skipper, along with some audio visual displays. We marvelled at the workmanship of the Victorian tunnels, and were impressed by the great size of the caverns. The tunnels in contrast were narrow, with no towpath. The early barges therefore could not be pulled by horses, but had to be moved along the tunnels by “legging”. Today, diesel engines are not allowed in the tunnels because of the lack of ventilation, so barges must either use electric engines, or employ the traditional method of “legging”. From time to time in the older tunnels we could see calcite deposits, and at one point, a rare treat – a beautiful calcite curtain covered the wall.

Altogether this was an excellent field trip. The two parts of the day complemented each other well, providing two very different views of the same area, and our thanks go to Graham Worton, and to Dudley Canal Trust and staff for making our visits so interesting and informative.

Calcite curtain in Dudley canal tunnel