210 MIOCENE PERIOD. [Ch. XV. 



a sea-cliff, when the whole country stood at a lower level 



No. 53. 

 d 



<t 



Section of Inland cliff at Abesse, near Dax. 

 a, Sand of the Landes. b, Limestone. c, Clay. 



relatively to the sea. But this can no longer be regarded 

 as matter of conjecture. In making excavations recently for 

 the foundation of a building at Abesse, a quantity of loose 

 sand, which formed the slope d, e, was removed, and a perpen- 

 dicular cliff exposed about 50 feet in height. The bottom of 

 this cliff consists of limestone, 6, which contains shells and 

 corals of Miocene species, and is probably a calcareous form of 

 the division c (diagram No. 51, p. 207). Immediately below 

 this limestone is the clay c (probably d, diagram No. 51, p. 207), 

 and above it the usual tertiary sand a of the department 

 of the Landes. At the -base of the precipice are seen large, 

 partially-rounded, masses of rock, evidently detached from 

 the stratum b. The face of the limestone is hollowed out 

 and weathered into such forms as are seen in the calcareous 

 cliffs of the adjoining coast, especially at Biaritz, near Bayonne*. 

 It is evident that, when the country was at a somewhat lower 

 level, the sea advanced along the surface of the argillaceous 

 stratum c, which, by its yielding nature, favoured the waste 

 and undermining of the more solid superincumbent limestone 

 b. Afterwards, when the country had been elevated, part of 

 the sand a fell down, or was drifted by the winds, so as to 

 form the talus d, e, which masked the inland cliff until it was 

 artificially laid open to view. 



The situation of this cliff is interesting, as marking one of 

 the pauses which intervened between the successive movements 

 of elevation whereby the marine tertiary strata of this country 



* This spot was pointed out to me by the proprietor of the lands of Abesse in 

 1830. 



