Sam
12 Jul 2025
I was invited to run a field trip for the Royal Geological Society of Cornwall to Loe Bar in July.
On July 12th I was invited by the fabulous Royal Geological Society of Cornwall to run a field trip to the spectacular Loe Bar. This is the second trip I have ran for the RGSC, and I thoroughly enjoy any opportunity to take this fantastic, enthusiastic community to look at the amazing geology around Cornwall.
The Royal Geological Society of Cornwall was founded in 1814 in Penzance to promote the study of the geology of Cornwall. It is the second oldest geological society in the world, after the Geological Society of London. It also has the longest run of publications of any geological society, the Transactions of the Royal Geological Society of Cornwall.
Today the society is open to anyone to join who has an interest and passion about the geology of Cornwall. They regularly hold field trips like this one, and lots of talks either in person or on Zoom. It is definitely worth checking out, and for a very reasonable annual subscription you can become a member today!
I mentioned this is the second trip I have done for RGSC (the first being to Carn Galver back in 2022). The weather this time round could not have been more different than the first, from wild wind and rain in February 2022 to blazing sunshine and +30°C! I am getting a bit of a reputation for running these trips in extreme weathers! In spite of the sweltering conditions, we had a great time.
Working from Loe Bar southwards towards Blue Rocks, I introduced the group to the beautiful turbidite sequences of interbedded mudstones and sandstones that make up the Portscatho Formation, the geological unit that crops out along this stretch of coast. These formed around 380 million years ago in the Upper Devonian, on a continental slope. Their sediment was sourced from the south; as two tectonic plates collided the upper plate shed sediment down in to a closing ocean.
Given this stretch of coast is famed for its structural geology, I thought it best to give the group a bit of a structural geology 101 just so they know what to look for and how to understand these complex structures in the rocks. How to recognise folds, faults, fractures and foliations. What do their shapes and orientations mean. All of this allowed them to spot these subtle structures hidden in the rock and deduce how they formed and what this tells us about the broader tectonic picture of south Cornwall.
Thank you to all of those members of RGSC who came along on the trip, it was great to see you all. A big thank you to Prof. Frances Wall from the Camborne School of Mines, and president of the RGSC for inviting me along to give the trip, and for helping with the organising along with Beatrice Kerno.
If you would like to explore the wonders of the geology along the coast around Loe Bar, well you can! Have a look at www.cornwallgeologist.co.uk/guided-walks and look for the Loe Bar Geowalks, and you can book your places on a walk.
Photo credit: Roeland de Greef