With St Patrick's day approaching and with it everything associated with the Emerald Isle being celebrated, our thoughts turn to a geological puzzle that can mystify the uninitiated. The United Kingdom and Ireland are geographically close together, for vertebrate palaeontologists in search of dinosaur fossils southern England can prove to be a rich hunting ground for dinosaur remains. However, Britain's neighbour - Ireland, is virtually devoid of all Dinosauria, there are no dinosaur fossils to all intents and purposes. Ironically, if you are looking for monstrous reptiles, parts of the south coast of England are a good place to look, but on the island which constitutes Ireland and Northern Ireland, it is the very far north of that particular landmass that you must visit if you wish to go hunting for Mesozoic vertebrates.
Many people are familiar with story of St Patrick, the patron saint of Ireland whose life and work is celebrated on the 17th of March each year. Of all the saints days in the United Kingdom, it is St Patrick's that tends to get celebrated the most, at least in our experience. We suspect that this is perhaps more to do with marketing agencies keen to find an event to help sell goods and services that sits nicely between Valentines day and Mothers day rather than any particular reference to his piety.
However, as all things Irish are celebrated, it gives us the opportunity to discuss one of the questions that we often get asked by our Irish customers, why are they dinosaur fossils to be found in the United Kingdom, whilst there are none to be dug up across the Irish Sea in Ireland?
Did St Patrick Drive Out all the Dinosaur Fossils as Well as the Serpents?
One of the stories associated with St. Patrick is that he was responsible for driving out all snakes from Ireland. The serpent (snake) is regarded as an evil creature, its role in Genesis has led to this particular member of the Squamata being cast as the villain in many western civilisations. Despite the apocryphal nature of this tale, it is true there are no native species of snake associated with the "Emerald Isle". However, an understanding of climate change and the impact of glaciation provides a more likely explanation as to why there are no native snake species. Snakes, of which there are relatively few species in northern Europe, simply did not return to Ireland after an Ice Age event, but why are there no dinosaur fossils? Bizarre, as the lack of snakes in Ireland can be partially explained by there being only three species native to the UK but many genera of dinosaurs have been discovered in the United Kingdom - Iguanodon, Hylaeosaurus, Lexovisaurus, Hypsilophodon, Scelidosaurus to name but a handful. To the best of our knowledge no dinosaur genus or species has ever been found in Ireland.
Why are there no Dinosaur Fossils in Ireland?
The answer to the question lies beneath your feet, it is all to do with geology. It is a question of understanding the types of exposed strata and their ages that can be found in Ireland and comparing these features to those found in the United Kingdom.
Ireland and the United Kingdom have been closely associated with each other for a substantial portion of geological time. However, in reality the geology of Ireland is much more closely associated with the very north of England and Scotland, indicating that these land masses share an affinity in terms of the geological processes that have shaped their bedrock.
There is another factor to consider, when it comes to looking for dinosaur fossils. Dinosaurs, as far as the known fossil record reveals, were entirely terrestrial animals - they were adapted to a life on land. For much of the Mesozoic (the age of reptiles), the landmass referred to as Ireland today was submerged, covered by seawater so no dinosaurs lived there.
Take for example, the Late Cretaceous. Sea levels had been rising for much of the Cretaceous Period and whilst in the western United States famous dinosaurs such as T. rex and Triceratops stomped around, approximately 98% of Ireland was covered by a shallow sea. Only a tiny portion of the landmass we know as Ireland today was above the water surface, a small, remote island situated on what would eventually become the eastern part of the county of Wicklow. The British Isles during this period was also largely submerged, hence the formation of such well-known geological features as the white cliffs of Dover. These are formed by marine deposits of tiny organisms, mostly phytoplankton and their tiny calcified plates called coccoliths.
Ireland both Northern Ireland and Eire have their share of important fossil locations. The majority of the geological map of Ireland is dominated by sedimentary rock. Limestones, shales, mudstones and coal seams that were laid down during the Carboniferous, a geological period that occurred long before the dinosaurs evolved. There are a number of significant locations in Ireland where invertebrate and primitive plant and fish fossils can be found. However, other types of vertebrate fossil are much, much rarer.
Contrast this with central and southern England where sedimentary strata dating from the Mesozoic is more readily exposed providing scientists with the opportunity to explore and discovery dinosaur fossils within these exposed Jurassic and early Cretaceous rocks.
Ireland's geology is much more closely related to the geology to be found in the very north of England and Scotland, where very few outcrops of rocks laid down in the age of reptiles are exposed on the surface. In the very north of the landmass that makes up Ireland and Northern Ireland there are many outcrops of metaphorphic rocks and igneous rocks including basalts laid down as a result of violent volcanic eruptions. This is testament to the immense forces that this part of the Earth's crust experienced as recently as 65 million years ago when the area was dominated by sea mounts and other volcanoes. A visit to the famous geological feature known as the "Giants Causeway" in County Antrim is proof enough of this part of Ireland's violent geological recent past.
Under these conditions, even if some dinosaur or other Mesozoic vertebrate's remains had been preserved they would have been destroyed as a result of these geological processes. However, there are some dinosaur and marine reptile fossils associated with Ireland. One of our members of staff is certain that they once read about a dinosaur trackway being found on a coastal site in the north of the island. Some fragmentary dinosaur fossilised remains have been found in Lower Jurassic strata in County Antrim.
As for marine reptiles, leviathans of the age of reptiles like the Plesiosaurs and Ichthyosaurs some fossil material has been found, again associated with localities on the coast of County Antrim, but these fossils are extremely fragmentary and very rare.
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