The road due west
from Fort William to the west coast port of Mallaig
is the culmination of the traditional “Road
to the Isles” through the Scottish Highlands,
and leads to magnificent views (on a clear day!)
of the Hebridean isles. In a geological context,
our route traverses the Caledonian orogen northwest
of the Great Glen fault, and provides a distant
introduction to the rocks of the North Atlantic
Tertiary igneous province, which form the islands.
The objective of the excursion is to examine the
Neoproterozoic Moine metasedimentary rocks forming
the Northern Highlands in a transect from the
west coast to the Great Glen.
Though intensely studied for
over a century, this regionally metamorphosed
and polyphase-deformed sequence is still highly
enigmatic, and potentially of considerable significance
in understanding global paleogeography. It is
presently believed to record the effects of three
major orogenic events at ~830 Ma (Knoydartian,
of uncertain tectonic significance), 470 Ma (Grampian,
arc-continent collision), and 425 Ma (Scandian,
Baltica-Laurentia collision). We will also examine
the pre-tectonic West Highland granite gneiss
intruded at ~870 Ma, perhaps during an early aborted
rifting of the Rodinian supercontinent.
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