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The Geology of Torbay

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Many trips are made every year to this area to study its rich geological history. This article has been written to help visitors understand what happened here millions of years ago. Torbay has the most interesting geology in the miles around it. The Jurassic Coast offers length and lots of fossils. Still, Torbay has been used by universities studying geology for many years because of the greater age of its rocks and the fascinating way they lie in relation to one another.

Saltern Cove Geology (image above)

The oldest rocks in Torbay are red/ brown weathered slates and grits. These rocks are not seen much at the surface, although there are one or two outcrops along the beaches, e.g. the small headland separating Goodrington North and South Sands. In some places, they became so rotten that they were reduced to clay, the material they initially made, deep on an ocean floor. At one time, this clay was the raw material for brickworks in Paignton, at Clayland Cross, which is still in place today on Ring Road. Interestingly, many houses in Paignton are built from bricks from 380 million-year-old ocean mud. These rocks belong to the lower part of the Middle Devonian period. Middle Devonian refers not to the place but to the age. The Devonian period lasted from about 395 to 345 million years ago. It is called Devonian because Devon was the first place where these rocks were studied in detail.


Limestones are amongst the oldest rocks in Torbay. They, too, belong to the Middle Devonian period but are slightly younger than the slates and grits described above; this limestone is a hard grey rock which is resistant to erosion and forms the two arms of the bay at Torquay and Brixham ( Berry Head). It is about 360 million years old and started as coral growing in a shallow tropical sea. Gradually, the sea got more profound; the corals died, and more corals grew on top until their remains became thicker. Gradually, the corals' calcium carbonate became dissolved and cemented with other chemicals to form solid rock. This rock is now hundreds of feet thick. Despite this dissolving process, there are many places around the coast where the erosion of the sea has picked out the outline of the fossil corals, such as the headland between Broadsands and Elberry Cove.

Limestone is full of joints or cracks. Even in times past, rain was acidic and dissolved the limestone around the cracks it ran through. Over tens of thousands of years, these cracks became huge caverns, which during the Ice Ages became the home to many prehistoric animals and early humans. A trip to Kent's Cavern is a must to see the prehistoric discoveries and giant caves. There are also well-known caves at Brixham and Buckfastleigh.


The limestone contains surprises, such as a small deposit of gold and "umber" that was discovered in the lower cliff at the western end of Meadfoot Beach; numerous iron ore deposits lie in pockets within the limestone. Iron ore in the form of Haematite was worked at Sharkham Point Brixham, and the produce was sent to South Wales for smelting. The umber was the raw material for high-quality protective industrial paints manufactured at Brixham in the late nineteenth century. The Tor Bay Paint Co. commenced manufacturing at Freshwater Quarry, Brixham, in 1895 and amongst other contracts, the paint was used on the Victoria Falls bridge in Africa. Umber is a rich yellow/brown mineral and a type of iron ore.

The coral sea where the limestone was deposited was dotted with volcanic islands. There are small quarries, particularly around Totnes, where rugged volcanic (igneous) rocks have been extracted for road building. In addition, there are places where you can see where volcanic ash has been incorporated into the seafloor mud, such as the northern arm of Saltern Cove at Paignton.


Gradually, the sea deepened, the corals died out, and mud was laid on top, eventually becoming Upper Devonian slate.
To understand more about our local geology, you must understand that rocks move around over the globe's surface, pushed around by convection currents of hot semi-fluid rocks rising and falling deep within the earth's interior. The Devonian rocks were originally in the tropics of the southern hemisphere, so you can imagine tropical islands with warm azure waters with water getting deeper as you went south and getting shallower towards a desert shore as you went north.

More rocks were laid on top of the Devonian (the Carboniferous rocks, which you can see in North Devon and South Wales), but all these rocks became forced up into mountain chains as the Earth's crust was crumpled as one part collided with another. The mountains may well have been higher than the Himalayas, and it was during this time that the granite of Dartmoor welled up from beneath as a molten rock and formed a core rather like the root of a tooth.


Over many millions of years, these mountains were worn away by the weather, and deserts formed around them. One of the most fascinating aspects of the geology of Torbay is the rock laid down on the desert floor. You have to understand that by this time, Torbay, as we know it, was at about the latitude of the Sahara and very hot. Periodically, flash floods brought down vast quantities of mountain rock debris.

This debris was washed out across the desert floor through valleys today called desert wadis. This was the era of the early dinosaurs, and geologists call it the Permian period (270 to 225 million years ago). It is doubtful whether the giant reptiles ventured far into the desert, and indeed, none of their remains has been discovered in the rocks of Torbay. However, we know that most of these desert rocks today cover South Devon, some of it dunes and some of its rock debris, which we call Breccia (pronounced ‘Brechia’).

You might wonder how we know this since there isn’t much left! Well, one of the things you are almost bound to have noticed driving around South Devon is how red the soil is. This colouration is due to iron chemicals only found in deserts. The chemicals were leached out of the overlying desert rocks and passed down into the Devonian rocks beneath, staining them red. Eventually, most of the Permian rocks were worn away, exposing the stained Devonian rocks. The Devonian slates weathered to become the red soil (You may have noticed that ordinarily white sheep become pink grazing in the fields around Torbay!!). Paignton is built on a desert, although thankfully, the climate is not as hot as it was when the rocks were originally laid down.

I recommend you go and look at the breccia of Roundham Headland the North of Goodrington Sands. You can see the desert sands enclosing sharp pebbles of Middle Devonian limestone washed down from the mountains. By studying the tilt of the pebbles, we can work out the direction taken by the flash floods as they tore across the desert landscape. Go to the small cove just north of Saltern Cove at Waterside between Paignton and Churston. You will be able to put your hand on the original desert floor because here there is what geologists call an unconformity where the desert rocks are lying directly on the Devonian rocks underneath, separated from them by a period of about a hundred million years.


Torbay has suffered thousands of earthquakes throughout its long geological history, some tearing the rocks apart by tens of metres. Today, earthquakes are rare and very minor. There is a big tear in the crust running from North Devon through Bovey Tracey and out into Torbay near Tore Abbey Sands, but it only moves a tiny bit and then only on average about every ten years, so you’re pretty safe! However, the scars of these earthquakes are all over Torbay, making the study enjoyable for the geologist. The tears or faults, as they are called, mainly within the Devonian, cause great complexity within the rock structure. When one rock shears past another, the rocks often become highly distorted, and sometimes their chemicals recrystallise as new minerals such as calcite. You will see a lot of evidence of this between Broadsands and Saltern Cove.

Sea level rise is no new phenomenon. It has happened countless times, and the sea level has been falling. Only tens of thousands of years ago (a very short time in the history of the Earth), Torbay had no sea in it at all, and the coast was way beyond Berry Head. Torbay was a wooded valley reaching down to the coast.

You can see the remains of the prehistoric woods at Goodrington at shallow tides when the stumps of these fossilised trees become visible at North Sands. Fossils of fossil corals are the most common types of fossils in Torbay. The Upper Devonian slates do sometimes yield small shell fossils. Very primitive fish have also been discovered as fossils in the Lower Devonian.
 

Torquay Museum has a worthy collection of fossils and prehistoric remains recovered from the district's limestone caves by a notable local Victorian collector, William Pengelly.
 

Author and Copyright. Robert Vaughton. All rights reserved.

Torquay is part of the Global Geopark Network, and the whole of Torbay was designated a Geopark in 2007 by UNESCO.

While many of the 195 UNESCO Global Geoparks worldwide are in remoter areas, often away from towns and cities, the English Riviera Geopark is unique in that it also encompasses one of the UK’s most popular seaside resorts. It is one of only two ‘urban’ parks in the UK, covering 62.4 km2 of land and 41.5 km2 of the marine area of Torbay.

GEOPARK WEBSITE

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