. Elements of geology. Geology. 292 LYELL'S ELEMENTS OF GEOLOGY. Age of the Granite of the Isle of Arran. the Firth of Clyde, on the west coast of Scotland, the four great classes of rocks, the fossiliferous, volcanic, plutonic and meta- morphic, are all conspicuously displayed within a very small area, and with their peculiar characters strongly contrasted. In the north of the island the granite rises to the height of nearly 3000 feet above the sea, terminating in mountainous peaks. On the flanks'of the same mountains are chloritic-schists, blue roof- ing-slate, and other rocks of the metamor
. Elements of geology. Geology. 292 LYELL'S ELEMENTS OF GEOLOGY. Age of the Granite of the Isle of Arran. the Firth of Clyde, on the west coast of Scotland, the four great classes of rocks, the fossiliferous, volcanic, plutonic and meta- morphic, are all conspicuously displayed within a very small area, and with their peculiar characters strongly contrasted. In the north of the island the granite rises to the height of nearly 3000 feet above the sea, terminating in mountainous peaks. On the flanks'of the same mountains are chloritic-schists, blue roof- ing-slate, and other rocks of the metamorphic order (a), into Fig. 293. Section of Arran. B. d d A, Crystalline, or metamorphic schist. e, Granite, c, Conglomerate, sandstone, limestone, and shale. D, Trap. which the granite (b) sends veins. These schists are highly inclined. On their truncated edges rest unconformable beds of conglomerate and sandstone, to which succeed various shales and limestones, containing fossils of the carboniferous period. All these secondary strata (c) are much tilted and inclined near the hypogene rocks ; but are horizontal at a distance from them, as in the south of Arran. Lastly, the volcanic rocks (d), con- sisting of greenstone, pitchstone, claystone, porphyry, and other varieties, traverse all the preceding formations, cutting through the granite in dikes (tZ), as well as through the sandstone ; which last they also overlie in dense masses, from 50 to 700 feet in thickness. Now as the different kinds of trap intersect all the other form- ations, they are certainly the newest rocks in Arran. The red sandstone and other secondary strata are older than the trap, but newer than the metamorphic schists, for the red sandstone conglomerates not only rest unconformably upon the schists, but contain rounded pebbles of those crystalline strata. It is equally certain that the schists are the oldest rocks in the island; they are more ancient than the trap and red sandstone, for reasons already sta
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Keywords: ., bookauthorlyellcharlessir17, bookcentury1800, booksubjectgeology
