III.—A Miniature Illustration of Normal Faulting

Extract

When examining the Glacial drift at Nevin, Carnarvonshire, I observed in a banded silty clay occupying the top of the cliff of drift at a point between Porth Nevin and Porth Bodeilias, an excellent illustration of my theory of Normal Faulting.

The bed in question consisted of an extremely finely laminated silty clay, sometimes called book-leaf clay, the laminations being grouped in ribands about half an inch wide and six inches apart, of lighter and darker colours, presenting a striped appearance very conspicuous from the shore. In the upper part of the bed the bands were continuous, though a little wavy : the lower part of the bed, as far as it was visible above the talus of sand, was faulted as shown in the accompanying diagram (Fig. 1). These faults simulated in a remarkable manner sections of faulted coal-fields which have been drawn from actual mining exploration and measurement.