At the Geo of Litlaland oceanic rocks were left perched atop the remains of a long vanished mountain chain as ocean floor was thrust onto the edge of an ancient continent.
Between 480 and 390 million years ago an ocean called Iapetus closed and the continents on either side collided to form a huge mountain chain. Some of the crust beneath the ocean was forced up over continental rocks over thousands of years in two major thrust sheets called nappes. Remains of both nappes can be seen on Fetlar. We call this exposed oceanic crust an ophiolite. Between the nappes is a chaotic area of highly deformed metamorphic rocks that came from the first nappe and from the continent beneath it as the mountains eroded. This area, called mélange, includes conglomerate - cobbles of differing rock types ‘cemented’ together in a fine grained matrix.
The Geo of Litlaland is the point of contact where the second nappe lies on top of the mélange. Towards this point the conglomerate becomes more deformed and then gives way to phyllite – metamorphosed muddy sand.
On top of the phyllite is gabbro – a thin sliver from the top of the lower nappe that was caught up and dragged along beneath the upper nappe as it was emplaced. The serpentinite cliffs beyond are the base of the upper nappe proper, most of which has eroded away.
