Tuesday, 20 September 2011

The Remains Of An Ancient Coral Reef In The Arctic

Devon Island's place within the Arctic Circle
Today, the Earth is divided into many distinct biomes. Deserts, jungles and savannah form a patchwork that covers the rocky surface of the Earth. When we look upon the world, it is hard sometimes to believe that a cloudy little area of Scotland was once a prehistoric swamp teeming with all manner of evolutionary marvels. That parts of the world were once very different. One such place is the cold, white expanse of the Arctic.

Such a place is seemingly unchanging. If it was said that millions of years ago, part of the Arctic was once a warm tropical reef, this might be considered madness. However Devon Island, a small piece of land close to the expanse of Canada was once exactly that. The bedrock of Devon island is part of one of the oldest landmasses on Earth, the Canadian Shield which dates to over 2.5 billion years old. Parts of this ancient geological structure exist on the surface of Devon Island today.
A view of Devon Island's limestone Rocks sculpted by multiple ice ages

There is a large gap in its geological record until 600 million years ago. During this time, the first complex animals rose and began to develop calcium carbonate shells. This was of great geological importance as calcium carbonate allows for the formation of limestone, a rock type that has dominated the last 500 million years of prehistory. This rock covers vast swaths of Devon Island and ranges in date from 600 to 350 million years ago and, although the study is incomplete, it preserves within it the first half of animal life on Earth.

Everything from the mysterious, soft- bodied Ediacarans to the hard-shelled, predatory nautiloids of the Palaeozoic can be found within the limestone rocks. A team of palaeontologists and geologists studied a section which dated from 450 million year ago, the boundary of two time periods known as the Ordovician and the Silurian, the Silurian is the younger. Apart from small scales and vertebrae which indicate the presence of some of the first ever fish on Earth, the limestone was composed of regular geometric shapes, tell-tale signs that the bulk of the limestone came from coral.

The entire formation was once a vast tropical reef. This discovery is very recent and the sheer range of geological time preserved within the rock makes the site a scientific marvel. Generally, reefs do not form in the Arctic Circle. This provides yet another piece in the puzzle as to how the continents moved around the surface of the Earth. If we are lucky, many new species of arthropod and vertebrate might be discovered at Devon Island.