Rocks on Rhossili Down – Part 1 – Jessica's Nature Blog

From the beach, I saw what appeared to be a small quarry at the base of the steep scarp which forms the western (seaward-facing) edge of Rhossili Down. It was a short way from the Old Rectory. This house sits on top of the level platform of loosely compacted material that makes up the solifluction terrace. The flat terrace runs along the north-south length of the Down.

I climbed up to have a closer look at the excavated area. I’m not sure whether it was a quarry or a natural feature. I was surprised to see rocks completely different from any I had seen on the beach as boulders or pebbles. The rock was also very unlike anything I had seen on at either end of the bay from beach level. I know that the headland to the south of the bay, from Rhossili village to Worms Head, and the headland to the north of the bay seen as Spaniard Rocks and the island of Burry Holms, are comprised of Carboniferous limestone rocks.

The great mass of Rhossili Down is mostly composed of Old Red Devonian sandstone which is older than the Carboniferous limestone. The characteristic red and pink stone – often mixed with other rock fragments as conglomerates – is found in abundance on the beach. It was these pink and red rocks that I expected to find in the quarry at the junction of the scarp and the solifluction terrace. However, I discovered something new – and I am still not entirely sure what I was looking at

The exposed surface of rock in the quarry revealed very narrow bands of fine grained greenish sedimentary rock that resembled shale. The strata were very steeply inclined, almost vertical in places, and mostly edge-on to the viewer. There seemed to be a diagonal unconformity where less steeply angled layers abutted the near vertical ones. Areas of rock that had presumably been exposed to the elements for some time had weathered to a rusty colour.

I am no geologist but I wish I were. The rocks are fascinating on Gower. I would love to understand exactly what I am looking at. I have been doing a bit of research into the subject. I’m currently reading some accounts of Gower geology in the following publications (there may be more recent editions than quoted) –

Mullard, J. (2006) Gower, New Naturalist Library, Collins, Paperback ISBN-13 978-0-00-716067-4, ISBN-10 0-00-716066-6.

Bridges, E. M. (1997) Classic Landforms of the Gower Coast, Series Editors Rodney Castledean and Christopher Green, The Geographical Association, The British Geomorphological research Group, ISBN 1 899085 50 5.

Neville George, T. (1970) British Regional Geology South Wales, Natural Environment research Council, Institute of Geological Sciences, 3rd Edition, London, HMSO, SBN 11 880084 1.

If you read this post and can tell me more about the rocks and structures featured here, I would really like to have your comments.

In the meantime, I hope readers can still enjoy looking at the rock pictures for their natural geological abstract qualities.