Life Under the Silurian Sea The history behind the formation of the very rare Grey Whitstone found in Kelly's quarry is truly ancient. The Imperial College of Science, Technology and Medicine took an interest in the Kelly's Fantane quarry and Dr. Jamie Wilkinson who is a lecturer in Mineral Deposit Studies provided a very interesting anecdotal piece about the site. You can read the full article below. Click on the image to enlarge.
"The grey rock which can be seen in Kelly's Quarry was laid down in an ancient ocean about 400 million years ago, in a period known as the Silurian. It's hard to imagine now that once upon a time much of Ireland was covered by this sea. The area of Wicklow may have been the closest land at that time, forming a chain of island volcanoes. Sand and mud, carried by large rivers from land to the northwest and southeast settled out on the bottom of the sea and was gradually buried over many millions of years, eventually turning into the layered grey rock you can see today.
At that time, most of the life on the planet lived in the seas, including our ancestors! The picture shows an artist's reconstruction of what the Silurian Sea might have looked like, including some of the animal life. Some of the creatures look similar to animals still living in the sea at the present day, others are long since extinct and still others have gradually changed, evolved into different shapes, so that we can now hardly recognise them.
At the back of the picture you can see animals which looks like plants. These are called crinoids. They have a long stem with a cup at the top which has five movable arms. These are distant relatives of modern animals like sea urchins and starfish.
The large disc-shaped objects resting on the sea bed are some of the earliest corals. These are tiny creatures which live in colonies, building up a large, hard structure made of calcium carbonate in which they live. There is another type of coral on the left of the picture which forms conical structures with waving arms at the top. Descendents of these corals are common in today's oceans, especially in tropical seas as they like warm water. They form long reefs where lots of animals and fish like to live that's why reefs are so good for snorkelling and diving!
In the bottom left of the picture you can see animals called trilobites. These are one of the most distinctive creatures of the Silurian sea, living on the seabed. They are now extinct, but they are in fact distantly related to insects, and do look a bit like woodlice! They had large compound eyes, like flies, and could see all around to watch out for danger.
The two large creatures with long shells and tentacles in the front of the picture are called cephalopods. They look a bit like octopuses. These animals were carnivorous, preying on the other animals living near the seabed.
Partly buried in the sand are the empty spiral shells of gastropods. Perhaps they were eaten by the cephalopods! These are the ancestors of many similar creatures which live in the modern seas and also on land. You may have seen shells like these at the beach or in the garden - snails are gastropods!
Finally, at the front on the right are a group of brachiopods. These are shellfish like the gastropods, but live in shells with two halves. Similar animals still live in today's oceans - it's amazing to think that they've been living in the world's oceans for over 400 million years!
One other thing that can be seen in the Quarry are white veins cutting through the rock. These are veins containing minerals called calcite, dolomite and quartz. These minerals were formed from hot solutions flowing through rock broken and split during earthquakes in the Carboniferous period, about 350 million years ago.
It was these hot waters that carried the metals zinc and lead to form the world famous zinc and lead ores of Ireland. These ores are important to the economy of the Irish Republic and are currently being mined at Navan (Co. Meath), Galmoy (Co. Kilkenny) and Lisheen (Co. Tipperary).
It is the job of geologists to understand how rocks and minerals formed and to use fossils preserved within rocks to work out the sorts of animals and plants which used to live on our planet in the distant past."
Dr Jamie Wilkinson
Lecturer at the Department of Geology, Royal School of Mines, Imperial College, London, UK.