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Siccar Point

In 1788, James Hutton first understood the significance of the geological structure at Siccar Point. Although not the first unconformity he had observed, it is certainly the most spectacular. The near vertical Llandovery (Silurian) age greywackes and shales younging to the WNW are covered unconformably by gently dipping Upper Devonian or Lower Carboniferous red breccia and sandstones.

The unconformity at Siccar Point.
Image provided by Dr C. Gillen, Edinburgh University.

Playfair wrote of Siccar Point in 1805: "On landing at this point, we found that we actually trode on the primeval rock, which forms alternately the base and the summit of the present land. It is here a micaceous schistus, in beds nearly vertical, highly indurated, and stretching from south-east to north-west. The surface of this rock runs with a moderate ascent from the level of low-water, at which we landed, nearly to that of high-water, where the schistus has a thin covering of red horizontal sandstone laid over it; and this sandstone, at the distance of a few yards farther back, rises into a very high perpendicular cliff. Here, therefore, the immediate contact of the two rocks is not only visible, but is curiously dissected and laid open by the action of waves."