Castle Bank: Wales’ answer to the Burgess Shales? by Dr. Joe Botting

At the last Meeting Dr.Joe Botting brought us all up to date with the new and exciting discovery of Burgess Shale type fauna in a quarry in mid-Wales. As often occurs, an exciting and important discovery comes just as work in an area is coming to an end. So it was with Joe and his wife Dr. Lucy Muir. They had been undertaking work in this area for 8 years but just as their work in this quarry was almost done they decided to take a last look at a very thin section they had not looked at previously. It was in this section that they made their highly important discovery.

Joe went on to explain that the middle Cambrian Burgess Shales as being one of the most important sites in the world in which many soft bodied animals are preserved, as carbon films, in very fine detail. In some cases not only is the soft tissue preserved but also internal structures, for example, neural tissue.This area and some other sites around the world, for example, The Chengjiang Biota have shown by how much life had evolved by the middle Cambrian. Not only do these sites show the fine details of the fauna but have also shown how markedly similar the fauna from all the sites actually is. It is from the Burgess Shale type formations that have shed light onto the Cambrian Explosion and the diversification of life. The end of the Cambrian sees little further diversification but is followed by the Great Ordovician Biodiversification Event leading to a large increase in biodiversity at the Family,Genus and Species level.

Fossil preserved as carbon film from Castle Bank By Joe Botting

He further explained that there are Ordovician Exceptional Fossil sites around the world but they are quite limited in one way or another when compared to the Burgess Shales, although there are two Ordovician Burgess Shale type areas, one at Afon Gam in north Wales and another at Fezouata in Morocco both from the early Ordovician. In contrast the Castle Bank fauna are from the middle Ordovician.

Castle Bank is situated within the northern part of the Builth Inlier. The stratigraphy here ranges from the Camnant mudstones through the Builth Volcanic Group to the Llanfawr Mudstones Formation. With fossils being found throughout.The area around Castle Bank is already well known for the fossil trilobites that can be found with the first trilobites being described from the area. Castle Bank itself is like any other farm quarry that can be found in the area with graptolitic shales and a few volcanic ash beds. But one section in this quarry was the one in which the soft bodied fauna was found. Like other fossils of the Burgess Shale type the fossils are preserved as carbon films and are very small!! The finds range from algae, hemichordates, sponges and many soft bodied animals that are still being identified. Joe and Lucy are working collaboratively with groups from other institutions on this task.

So in conclusion how good is castle Bank? Well, Joe suggests the following:

  1. At least 20 phyla (probably) - similar to Chengjiang.
  2. Nearly 200 species so far - similar to the Burgess Shales.
  3. Preservation of entire range of benthic organisms down to larger meiofauna.
  4. Some internal organ preservation and a lot of very soft and very fine tissue.
  5. Almost everything is new unlike the Cambrian Burgess Shale Type faunas which are similar to each other.
  6. Several major groups are the only fossil examples.

A fascinating talk on an equally fascinating discovery.