. Elements of geology. Geology. 198 LYELL'S ELEMENTS OF GEOLOGY. Different character of Chalk in South of Europe. formation, although still exhibiting some of the , ame mineralo- gical peculiarities, is nevertheless greatly changed. Its calca- reous division consists for the most part of compact crystalline marble, often full of nummulites (see Fig. 180.), and those por- Fig. J\rummulite limestone; Peyrehorade, Pyrenees. a External surface of one of the nummulites, of which longitudinal sections are seen in the limestone. b Transverse section of same. tions which may be imagined to repre
. Elements of geology. Geology. 198 LYELL'S ELEMENTS OF GEOLOGY. Different character of Chalk in South of Europe. formation, although still exhibiting some of the , ame mineralo- gical peculiarities, is nevertheless greatly changed. Its calca- reous division consists for the most part of compact crystalline marble, often full of nummulites (see Fig. 180.), and those por- Fig. J\rummulite limestone; Peyrehorade, Pyrenees. a External surface of one of the nummulites, of which longitudinal sections are seen in the limestone. b Transverse section of same. tions which may be imagined to represent the green-sand, are composed of shales, grits, and micaceous sand-stone, containing impressions of marine plants, together with lignite and coal. There are also beds of red sandstone and conglomerate, belong- ing to the same group. These rocks ascend gradually into the highest part of the Pyrenees, and cross over into Spain, where the cretaceous system assumes a character still more unlike that of northern Europe. Here, as on the north side of the Pyrenees, the most conspicu- ous fossils are hippurites, sphserulites, and nummulites. The last-mentioned fossil, so called from its resemblance to a piece of money, is a genus of mollusca, very abundant in the tertiary strata of Northern Europe; but only met with in chalk in the South of Europe. So many species and genera of shells now wanting in our northern seas, are frequent in the Mediterranean, that we need not be surprised, when following from north to south the deposits of the old cretaceous sea, at finding similar modifications in or- ganic forms. The cretaceous rocks in the Alps, Italy, Greece, and Asia Minor, are distinct in like manner from the type of that forma- tion in the North of Europe; yet their age in most of these countries can be clearly ascertained, partly by following them continuously from the north in the manner above described; and partly by their position below the tertiary, and above the oolitic strat
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Keywords: ., bookauthorlyellcharlessir17, bookcentury1800, booksubjectgeology
