When I visited Dunraven at Southerndown on Christmas Day (see blog post here) I did say I would tell you some more about the cliffs of the Heritage Coast itself. So here goes.
Dunraven Castle is on a headland between two beaches. The tip of the headland is called Witches Point. The beach on one side is hard to reach, but looks good in pictures taken from the Dunraven viewing point, while the other is a popular beach for families, dog walkers – and BBC TV filming.
These Southerndown cliffs are made up of layers of sedimentary rocks, laid down as the calcium skeletons of marine creatures, mud silt and sand at the bottom of ancient seas. Over millions of years they solidified into limestone, shale and pebbly conglomerate.
The oldest rocks here are hard, grey Carboniferous limestones, now found at sea level. These were laid down in a warm, shallow sea 300 million years ago when what is now Wales was just south of the equator.
This crust was folded, fractured and eroded over the next 100 million years during the Variscan orogeny, a time when the southern land mass of Gondwana slowly collided with the northern land mass of Laurussia to create the supercontinent of Pangea.
Coming back over the headland you reach the main Southerndown beach, an area called Dunraven Bay. There is car parking here.
Around 200 million years ago, in the Triassic and early Jurassic periods, this area again lay underneath a warm, shallow, equatorial sea.
New deposits included a red Triassic conglomerate and a creamy white Jurassic limestone known as Sutton stone. Overlying these, the “Southerndown beds” consist of blue/grey limestones with thin shale partings in between.
The beach doubled as Bad Wolf Bay (in Norway) in Doctor Who – the place where the Doctor and Rose said goodbye in the episode Doomsday. I cried! If you want to watch the parting again it’s on YouTube.
At low tide, Triassic deposits dated at 250 million years, can be seen extending for 300 metres out to sea.
Away from the sea you can see the clear layers in the cliffs, but don’t get too close as they are crumbling…
Most of these rocks have been known as “Blue Lias“, a particular geological formation of a certain date with thick beds of limestone and thin layers of shale between. Lias is an old word for limestone. The Jurassic cliffs around Lyme Regis in Dorset are also “Blue Lias”.
Minerals such as lead sulphide and barium sulphate were deposited in the limestone layers around 200 million years ago – and I wonder if that is why there is a yellow tinge to the cliffs?
This part of the beach was used for another Doctor Who setting. The 11th Doctor, Matt Smith, was here with Amy Pond (Karen Gillan) and River Song (Alex Kingston) in episodes The Time of Angels and Flesh and Stone…
The Jurassic rocks are rich in fossils. Shells of bivalves and ammonites, fragments of crinoids, corals and pieces of carbonised fossil wood are quite common. There is now a display to show people what to look for…
There’s still life on the beach…
And so we return to the present day at Southerndown – but with 300 million years of life on Earth on display, what better setting could there be for a Time Lord like the Doctor and his companions…