Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/175

Rh There is a bed of marl on the 6 feet of solid chalk, shown in fig. 13, and also continuous bands of flints. We can thus accurately observe the marks of the movement which has taken place in the upper surface of the denuded chalk. The bed of tabular flints, about 1 inch thick, touching the upper part of the artificial opening marked cave, is fractured and contorted, while the traces of a still higher band of large detached flints are visible in the gravel above the top of the cave, where it ends. Then comes a coarse ochreous flint-gravel 7 feet thick, with veins of sands and some chalk fragments. This is eaten into by the covering dark bed of sand with flints. The middle portion of this section is chalky, and must have been more altered by chemical than by mechanical action, as the flint-veins have been so little disturbed. At p. 113 of the last volume of this journal I gave some illustrations of the destruction of chalk in situ by some kind of chemical action, which was probably contemporaneous, if not identical, with that which has eroded the surface of the chalk, and formed pipes over such large areas.

Fig. 14, representing the highly-inclined chalk with flint veins 200 yards east of Freshwater Gate, Isle of Wight, is given for comparison. The covering bed is nearly horizontal, as usual. The character of the chalk and the disposition of the gravel closely resemble those at Rottingdean; and the latter is about the same height, from 25 to 30 feet. Mammalian remains have been found in this bed close by Freshwater Gate.

Fig. 15, Sangatte Cliff, near Calais, is given for comparison with these Brighton sections. The escarpment of the chalk, near the upper part is 43°, then it reaches 55°, and descends to 43°. The Sangatte raised beach is just above the level of high water at this point, and is composed of large flints and pieces of chalk, as at Brighton.