Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/176

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In the middle of the Sangatte series a line of chalk boulders, deposited at an angle of 12°, is shown in some places. At about half a mile from this point Mr. Prestwich found, just above high-water mark, abundance of freshwater shells of living species in a fine tranquilly deposited marl covered by 50 feet of gravel, continuous with the upper 30 ft. of the gravel shown in fig. 15. The slope of the covering bed of gravel(e) is not more than 1° or 2°. There is very high ground at the back of this section (which is near Cape Blancnez), from which the chalk and gravel were derived and thrown over the ancient chalk-cliff 80 feet high.

Near the village of Sangatte the covering gravel reaches high-water mark, and the whole of the middle series intercalated between the basement gravel and the covering gravel is seen.

While the materials of the gravel at Sangatte are principally brought over the cliff from the high land, they are interstratified with an ordinary beach and with a lacustrine deposit formed at the same time within a few feet of the present level of high water.

A similar beach, or a similar lacustrine deposit, might be formed