With respect to the littoral deposits of the Quaternary period, they are of very limited extent, except in a few localities. They are found on the western coast of Norway, and on the coasts of England. In France, an extensive bed of Quaternary formation is seen on the shores of the ancient Guienne, and on other parts of the coast, where it is sometimes concealed by trees and shrubs, or by blown sand, as at Dax in the Landes, where a steep bank may be traced about twelve miles inland, and parallel with the present coast, which falls suddenly about fifty feet from a higher platform of the land, to a lower one extending to the sea. In making some excavations for the foundations of a building at Abesse, in 1830, it was discovered that this fall consisted of drift-sand, filling up a steep perpendicular cliff about fifty feet high, consisting of a bed of Tertiary clay extending to the sea, a bed of limestone with Tertiary shells and corals, and, at the summit, the Tertiary sand of the Landes. The marine beds, together with the alluvium of the rivers, have given rise to those deposits which occur more especially near the mouths of rivers and watercourses.
Fig. 201.—Shell of Planorbis corneus.
[98] H. Woodward, Geological Magazine, vol. viii., p. 193.
[99] “Darwin’s Journal,” p. 130.
[100] “Journal of Researches,” &c., 2nd ed., p. 133. Charles Darwin.
[101] “Journal of Researches,” &c., by Charles Darwin, p. 81.
[102] “Journal of Researches,” &c., by Charles Darwin, 2nd ed., p. 81.