Southern Appalachian Digital Collections

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Report of the Secretary of Agriculture in relation to the forests, rivers, and mountains of the southern Appalachian region

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  • SOUTHERN APPALACHIAN REGION. 119 regard to the moist, warm winds from thoGulf combines with a general altitude unequaled east of the Mississippi to produce a unique and remarkable vegetation. (PI. LXIV.) THE GEOLOGIC FORMATIONS. The geologic formations which underlie this mountain district may be divided into four large groups. Each differs widely from the others in age, and has very distinct features of its own. These broad differences have expressed themselves in such major topographic features as the Appalachian Valley, the Appalachian Mountains, and the Piedmont Plateau. These differences are also largely responsible for the principal variations in the character of the surface in the mountain district itself. The Appalachian Valley is underlain by a series of lime- ^ime»tone stones, shales, and sandstones, mainly of late Cambrian and Silurian age, forming the youngest of the four groups in this region. Small outliers of these formations are included within the area of the mountains near the border of the Appalachian Valley. The second group occupies the northwestern border of gr^Upartzite the mountain district, chiefly northeast of the French Broad River. It consists of a series of quartzites, sandstones, conglomerates, and shales of Lower Cambrian age. A second large area of these rocks occupies the Blue Ridge and adjacent territory, nearly in the center of this district. The third group is of Cambrian age. It occupies the groupnglomerate northwest border of the mountain mass, corresponding in position to the previous group but best developed southwest of the French Broad River in the Smoky and Unaka mountains. The group consists of conglomerates, gray- wackes, sandstones, schists, and slates, and is called the Ocoee group. This and the preceding two groups were composed of the waste from older rocks, which was deposited under water. The thickness of the strata is approximately the same in the Ocoee group and the formations of the Appalachian Valley. The Lower Cambrian quartzites and shales of the second group have only from one- fourth to one-third of the thickness of either of the preceding groups. The fourth group is muclythe largest of all, both in actual Gnei8S gro,,p bulk and area. It consists in the main of formations of
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Object’s are ‘parent’ level descriptions to ‘children’ items, (e.g. a book with pages).