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They cover nearly the whole of the Little Cumbrae, where they give rise to marked terraced features and are arranged in a gentle synclinal fold.

The coal-field is synclinal in structure, Port Seton being about the centre; it contains ten seams of coal, and the area covered by it is some 30 sq. m.

Section of anticlinal valleys and synclinal mountains 78 17.

Where they dip away from the axis of movement the structure is termed an anticline or anticlinal fold; where they dip towards the axis, it is a syncline or synclinal fold.

North and south of the great anticline of the Weald of Kent and Sussex are two synclinal troughs known as the London and Hampshire basins.