Where did Scotland come from?

Sunday 21 October 2001

Scottish geologists studying one of the major fractures in the Earth’s crust may be able to prove once and for all the origins of the pieces of the Earth’s crust which make up Scotland.

In a study of the rocks on each side of the Great Glen Fault, an international collaboration headed by experts at the University of St Andrews, will determine whether or not pieces of Scotland originated from Canada, Greenland, Scandinavia or elsewhere, by examining rock samples from the Highlands using high-precision dating techniques.

The results may paint a somewhat different picture of the map of Scotland, through a new reconstruction of the land on either side of the Fault.

Backed by the Carnegie Trust, the study is co-ordinated by Dr Grahame Oliver of the University’s School of Geography and Geosciences, and involves the collaboration of his colleagues of the Crustal Geodynamics Group at St Andrews and fellow geologists and geoscientists based in Glasgow, Inverness, Nottingham and Munich.

Scotland contains the most studied and perhaps the most controversial rocks in the World. It is known that Scotland is made up of small pieces (or terranes) of the Earth’s crust, assembled and broken by plate tectonic processes at various times starting 3 billion years ago. The Great Glen is an obvious tectonic lineament (fault) that cuts right across the landscape of the Scottish Highlands. It’s significance and importance is still hotly debated.

“The study of Scotland’s geology is important because it is a natural field laboratory in which to study how the Earth’s crust has evolved. Many modern theories about Earth processes were initiated in Scotland,” said Dr Grahame Oliver, Co-ordinator of the study.

Because the scale of the Great Glen is so great, it is assumed that there are two sides to it – the Northern Highlands terrane to the north and the Central Highlands Grampian terrane to the south. Although some geoscientists believe that the rocks on the two sides of the fault are of dissimilar ages and have dissimilar histories, Dr Oliver and his group believe that this is not necessarily the case. With this study, they aim to challenge the commonly accepted 25- year old theories and prove that each side of the fault has a similar geological history. It would follow that the Great Glen Fault is not such a big fault after all.

By studying rock samples containing garnet and zircon from the Highlands, the group will be able to determine not only the age but also the conditions of formation. They aim to investigate how and when the various rock units came together and where they came from. Once this is known, they will compare their samples with similar rocks from Canada, Greenland and Scandinavia, before conclusions can be drawn about their true origins.

The St Andrews geoscientists have been collecting rocks from the Great Glen Fault area all summer, and will return at six month periods. The rocks are being crushed, prepared and characterised by technicians at the St Andrews lab, before being sent to NERC Isotope Geoscience Labs in Nottingham and the Institute for Mineralogy, Petrology and Geochemistry in Germany for sophisticated isotopic age dating. Experts at these labs will apply new high precision uranium lead and samarium neodynium techniques which can date rocks over 1,000 million years old, with a margin of error of just 1%.

The study of geology in Scotland has recently experienced something of a renaissance in that the application of new methods of age dating the rocks has shown that old accepted “facts” can no longer be taken for granted. By 2003, the group should have a clear idea of whether their working hypothesis can be proved, and ultimately, find out where Scotland came from.



Issued by Beattie Media On behalf of the University of St Andrews Contact Gayle Cook on 01334 467227, mobile 07900 050103, or email [email protected]

View the latest University news at http://www.st- andrews.ac.uk/extrel/press.htm

22nd October, 2001

Category Research

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