VIII. The Shore Section at Portincross, Ayrshire

Abstract

There is probably not a more interesting section anywhere in the West of Scotland than that exposed along half a mile of the shore at Portincross, on the Ayrshire coast, opposite the Lesser Cumbrae. The coast line, from the place in question, to the neighbourhood of Ardrossan, is occupied by a series of soft red sandstones belonging to the Lower Calciferous series, dipping, at low angles, generally in a southerly direction. On the west shore of Ardneil Bay these rocks are seen to be suddenly truncated by a fault ranging towards the south (A in diagram on next page). West of this fault comes a series of red, mottled, and grey sandstones, and deep red mudstones, standing on edge and striking parallel with the fault. Crossing it in a westerly direction is a dolerite dyke, 25 feet in thickness, which, at the fault, is inclined towards the north, at an angle of 10 degrees from the perpendicular, which increases to 25 degrees as it disappears below low-water mark. This is the same dyke which runs through the village of West Kilbride, two miles distant, where it has a thickness of 60 feet, and is vertical. Passing on over the edges of the vertical sandstones for a distance of 200 yards, we come to another fault (B) which ranges parallel to A, and beyond it appears a series of neutral-tinted strata, also standing on edge, and so severely crushed and contorted that most of the beds assume quite a lenticular aspect. This 250-word extract was created in the absence of an abstract