Geological Walk at Penwyllt and Ogof Ffynnon Ddu – Geologists' Association

This is some additional information and pictures to support the geology walk at Penwyllt and the Ogof Ffynnon Ddu Nature Reserve. Take a look at the descriptions under each picture to see more information

Map of the Penwyllt and and Ogof Ffynnon Ddu area

The Localities mentioned on this post relate to the map which is included in the leaflet PDF and is repeated here to make this page easier to read. For more information and descriptions of all the localities and the start point, parking etc. please see the leaflet

To download and print this walk, please open / download the PDF version here

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Cwm Dwr Quarry, the walk starts in the car park here and you first start with a view of the cave entrances in this old Quarry (Locality 1) , be careful near quarry faces

Cwm Dwr Quarry and the Twrch Sandstone ridge beyond — View across Cwm Dwr Quarry to the Twrch Sandstone ridge beyond at the Car park

Craig-y-nos Station at Locality 2 on the walk

South is to the right of this picture of the quarry face at **Locality 3** The limestone dips in this direction.

View into the Modern Quarry — From **Locality 4** you have a view past Craig-y-nos station into the Modern Quarry. Although now also disused this quarry is not open for visits and should only be viewed from this hillside as an appropriate vantage point

The chert in the limestone at **Locality 6**

The wall of Penwyllt Bricks at the old Brickyard (**Locality 7**) should not be disturned or climbed on

At the old brick Kilns at **Locality 7** you can find the glassy surfaces where the inside of the kilns melted

Below is a slideshow of pictures of the cave passages inside the "Top Entrance" of the cave seen at Locality 8

Click on the images to se elarger versions or manually drive the slideshow or just let it run

The view across the valley from **Locality 10** to Fan Hir with the glacial morraines at the foot of the escarpment

A useful addition to your walk is the BGS Geology Viewer which is a free smartphone app to view geological maps of Britain wherever you go https://www.bgs.ac.uk/technologies/apps/igeology-app/

We hope you enjoyed this short tour of Penwyllt and Ogof Ffynnon Ddu. If you’d like to learn more about our local geology, take a look at other pages on the South Wales Geologists’ Association website: www.swga.org.uk