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MILLSTONE GRIT
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MILLSTONE GRIT , in See also:geology, a See also:series of massive sandstones, grits and conglomerates with alternate shales, the whole resting directly upon the Carboniferous See also:Limestone or upon intervening shales (Yoredale, Limestone Shales), usually in stratigraphical continuity. Its occasional See also:coal-seams show that conditions of coal-formation had already begun. In See also:Great See also:Britain its outcrop extends from the See also:Bristol Coalfield through See also:South and See also:North See also:Wales to its fullest development in the north-midland counties, See also:Lancashire and See also:Yorkshire, and thence to See also:Scotland, where the Roslin See also:Sandstone of the Lothians and the See also:Moor See also:Rock of See also:Lanark and See also:Stirling are considered its equivalents. Characterized by grits and sandstones of the same See also:general type, though individually variable, as sandbanks formed on the shoaling of the Carboniferous See also:sea, yet often persistent over wide areas, the formation, estimated as 5000 ft. thick in Lancashire, contains typically the following grits in descending See also:order: First, or Rough Rock; second, or See also:Haslingden Flags (Lancashire); third, or See also:Chatsworth Grit (the last two being the See also:Middle Grits of Yorkshire); See also:fourth and fifth, or Kinderscout Grits and the Shale Grits. The first and third, the most persistent, are often coarse and pebbly, like the Kinderscout Grits. In the north of See also:England these grits lose their identity. In South Wales the Millstone Grit, immediately succeeding the Carboniferous Limestone, consists of 450 ft. of grit and shale, its upper member being the massive pebbly Farewell Rock. It extends into the Bristol Coalfield, though not recognized in the See also:Devonshire See also:Culm. In See also:Ireland certain See also:grey grits and flags are assigned to it. In See also:northern See also:France and See also:Belgium it loses its individuality and is merged in the Coal-See also:measures. It reappears See also:east of the See also:Rhine, but is unrecognizable in the somewhat different Carboniferous See also:succession of eastern See also:Europe. In See also:America the See also:Pottsville See also:Conglomerate, 1500 ft. thick in the south Appalachians, with workable coals, and widely unconformable upon the Mississippian, introduces the Pennsylvanian (Upper Carboniferous) See also:system, and approximately represents the Millstone Grit of western Europe, as does the red conglomerate of Nova See also:Scotia. The shales of the Millstone Grit include thin beds of marine goniatites (Glyphioceras bilingue, Gastrioceras carbonarium), Pterinopecten papyraceus, and Lingula mytiloides, while the grits contain Lepidodendron, Stigmaria and calamites. In Scotland See also:plants and estuarine fishes differ markedly above and below the Roslin Sandstone. The See also:English Millstone Grit produces a characteristic scenery of See also:wild moorland plateaux, or alternations of shale-valleys and rugged grit-ridges. The grits furnish valuable See also:building-stones ,and grindstones. They also afford an excellent See also:water See also:supply. (C. B. Additional information and CommentsThere are no comments yet for this article.
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