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Show 170 OLDER PLIOCENE PERIOD. [Ch. XII. but it may originally have been 3000 feet deep, as. it is now c1 o se to t h e s1 1 ore a t Nl'ce · Here ' therefore, a forma. tion resem. bling that of the Magnan above described may be m progress. The time required for the accumulation of su~h a mass of cong1 o mera t e a s we have J. ust considered must be Immense: on l d Sw 1at groun uch formations have been fr.e quently referred to diluvial waves and to periods ·of great disturbance, we could never understand, for the causes now in diurnal action at the foot of the Maritime Alps and other analogous situations seem to us quite sufficient to explain their origin. Tertiary st·rata at the eastern ext·remity of the Pyrenees.W e shall conclude this chapter with one more example derived from a region not far distant. On the borders of the Mediterranean at the eastern extremity of the Pyrenees, in the South of France, a considerable thickness of tertiary strata are seen in the valleys of the rivers Tech, Tet, and Gly. They bear much resemblance to those already described, consisting partly of a O'reat thickness of conglomerate, and partly of clay and sand, :ith subordinate beds of lignite. 'l'hey abut against the primary formation of the Pyrenees, which here ~onsists of mica-schist. Between Ceret and Boulon these tertiary strata are seen inclined at an angle of between 20° and 30°. The shells which I procured from several localities were recognized by M. Deshayes as agreeing with Subapennine fossils. . Spain-Morea. -It appears from the recent observ.attons of Colonel Silvertop, that marine strata of the older Pliocene period occur in patches at Malaga, and in Granada, in Sp.ain. They have also been discovered by MM. Boblaye and Vulet in the Morea, and the names of many of the shells brought from thence are given in the Appendix No. I. CHAPTER XIII. Crag of Norfolk and Suffol~-Sbown by its fossil contents to beloug to the older Pliocene period-Heterogeneous in its composition-Superincumbent lacustrine deposits-Relative position of the crag-Forms of stratification-Strata com· posed of groups of oblique layers-Cause of this arrangement-Dislocations in the crag produced by subterranean movements-Protruded masses of chalkPassage of marine crag' into alluvium-Recent shells in a deposit at Sheppey, Ramsgate, and Brighton. CRAG OF NORFOLK AND SUFFOLK. TnE older Pliocene strata, described in the last chapter, are all situated in countries bordering the Mediterranean, but we shall now consider a group in our own island, which belongs to the same era. We have already alluded to this deposit under the provincial name of crag*, and pointed out its superposition to the London clay, a tertiary formation of much higher antiquity t. The crag is chiefly developed in the eastern parts of Norfolk and Suffolk, from whence it extends into Essex. Its relative age.-A collection of the shells of the c crag' beds, which I formed in 1829, together with a much larger number sent me by my friend, Mr. Mantell of Lewes, were careful1y examined by M. Deshayes, and compared to the tertiary species in his cabinet. This comparison gave the following result: out of 111 species, 66 were extinct ot· unknown, and 45 recent, the last, with one exception ( Voluta Lamberti, Sow.), being now inhabitants of the German ocean. Such being the p.roportion of recent and extinct species, we may conclude, accordmg to the rules before laid down t, that the crag belongs to the older Pliocene period . . Mineral composition.-So heterogeneous is this deposit in ~meral ~haracter, that we can scarcely convey any correct no~ Ions of I.ts appearance, without describing the beds separately m the different localities where they occur. In general, they • Chap. ii. p. 19. · t S~:e above, Diagram No.4, :P· 21. ~Page 54. |