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Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ, UK
At the time it was written, Kennedy’s paper on the Great Glen Fault had clear evidence for a known lateral displacement, and the evidence was so well presented that it convinced a sceptical geological world that such movements were possible. The acceptance of large scaled lateral movements led to the concept of great fundamental fractures and, with the advent of plate tectonics and a climate of mobilistic thinking, many of these great fractures were later recognized as plate or terrane boundaries.
Along with this thinking, new criteria evolved for recognizing those fractures that had been involved in major displacements—in fact the concept of throw became replaced by the concept of role. Role was identified from the history of the blocks on either side of the fracture, and where that history was incompatible with them being together, then a large role was possible for the fault itself.
Taking a new look at the Great Glen Fault in these terms, it becomes clear that there are insufficient data on the rocks on either side to allow any conclusions about the nature and timing of its role to be deduced. If the later, displacements, which are at present the main concern of researchers, are the sum of the movements on the fracture then it is ironically the least significant of the four NE-SW fractures in Scotland.
