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‘Gneiss’ Rocks

Thu 10 December 2015

Category: Geology, Gneiss Rocks, Membership

Hutton’s Unconformity – Isle of Arran

Although not as obvious as unconformities that he identified later (Siccar Point, for example), the exposed unconformity on the Isle of Arran is arguably where the science of modern Geology began.  James Hutton’s field work on Arran (and other places) led to his Theory of the Earth which he presented as a paper at a meeting of the Royal Society of Edinburgh in 1785 and which he published as a book in 1788.

Hutton found this, his first unconformity, to the north of Newton Point near Lochranza on the Isle of Arran.  It occurs where near-vertically dipping  Precambrian Dalradian schists are overlain by more recent Lower Carboniferous sandstones with an obvious difference in dip between the two rock layers.  The older pre-Cambrian rocks in the photograph are in the foreground, dipping downward to the left; the overlying Carboniferous sandstones dip towards the sea in the background.

From Ian Relf, Seismic Experts Company Limited

Hutton's Unconformity, Newton Point, Isle of Arran

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