Moinian

This view, espoused particularly by Roderick Murchison, a geologist known as the "Master of the Silurian", was opposed by James Nicol, who thought that the contact (or "zone of complication" as he called it) was tectonic in nature and that the metamorphic rocks were older and not in stratigraphic sequence with those below.

This difference of opinion led to the Highlands controversy, which pitted groups of geologists against each other, particularly between the Geological Survey and academic researchers.

[3] Eventually these rocks, now generally known as the "Moine Series" were mapped all the way to the Great Glen Fault in areas not covered by the Old Red Sandstone.

[4] The Moine was not subdivided in a regional way until 1969, when three units were proposed; the Morar, Glenfinnan and Loch Eil divisions.

Detrital zircon geochronology, combined with the dating of igneous intrusions and metamorphic events, has supported the Torridon to Morar correlation.