Page:The American Cyclopædia (1879) Volume XVI.djvu/140

series to the top of the coal, embracing various massive sandstones and conglomerates. As the combined result of these disturbances and the subsequent erosion of the surface, the whole region has been converted into a mountainous belt of parallel ridges, extending along the N. W. side of the great Appalachian valley from the Catskill mountains of New York throughout all its length, and constituting the Alleghany mountain belt, of which the Kittatinny may be considered as the eastern limit. In this disturbed region occur the anthracite and semi-bituminous coal basins of Pennsylvania, Maryland, and Virginia, and the dislocations just alluded to are in repeated instances so great as to bring up the base of the palæozoic series on the N. W. side of the detached areas of coal. To the westward these disturbances become less and less marked, and the Devonian and carboniferous rocks are seen comparatively undisturbed. Further to the west we reach the Cincinnati axis, which is traced from Lake Ontario to N. Alabama, and brings up on a gentle anticlinal the upper Cambrian beds, known in this region as the Cincinnati group, from Cincinnati with some interruptions to Nashville, Tenn. Further southward it sinks beneath the coal formation of Alabama. To the east of this great dividing line extends the Appalachian coal field from Alabama through E. Tennessee, Kentucky, and Ohio, including West Virginia and the W. half of Pennsylvania; while to the west of it are three other palæozoic coal fields, that of Michigan, that of Illinois, including parts of Indiana and western Kentucky, and that west of the Mississippi, extending from Iowa, through Missouri, Kansas, and Arkansas, into Texas. (See Coal.) To the westward of this last coal field are great areas of newer rocks of triassic, Jurassic, cretaceous, and tertiary periods, which extend to the base of the Rocky mountains and beyond. The cretaceous and tertiary strata, after stretching southward through Texas, reach up the Mississippi valley as far as the mouth of the Ohio, eastward along the gulf of Mexico, and thence northward to the coast of Massachusetts, in a belt of gradually diminishing breadth, including Long Island and a part of Martha's Vineyard. The valley of the Mississippi, with the greater part of Florida and a border of varying width along the seaboard, is overlaid with deposits which are regarded as post-tertiary. The whole of these newer strata along the Atlantic region rest in a nearly horizontal attitude on the eozoic and palæozoic rocks. The cretaceous strata are in many parts concealed, but are recognized along the N. portion of Long Island, and pass across New Jersey and N. Delaware to the head of Chesapeake bay. Thence they are exposed at a few points in E. Virginia, the Carolinas, and Georgia, till in the W. part of this state they appeal in a broad belt extending through central Alabama and curving northward through N. Mississippi and E. Tennessee. These newer rocks along the Atlantic coast form the tide-water region, and are nowhere affected by the movements which have disturbed the older rocks. What has been called the new red sandstone formation of the Atlantic belt extends in a narrow line from N. Massachusetts along the Connecticut valley to New Haven. It is again continued from the Hudson across New Jersey and Pennsylvania into Virginia, and is found in smaller areas in S. E. Virginia and in North Carolina. From its organic remains this sandstone is regarded as lower mesozoic, probably including the triassic and Jurassic periods. In Virginia and in North Carolina it includes beds of workable coal, which rest upon the eozoic crystalline rocks. In a similar relation there is a considerable area of coal-bearing rocks in Rhode Island and Massachusetts, which are however of palæozoic age like the coals of the Appalachian field. Small areas of fossiliferous lower Cambrian, Silurian, and Devonian are found in various localities among the crystalline rocks of New England. Over the N. E. portions of the United States is widely spread the so-called drift formation or diluvium of post-pliocene ago (see Diluvium), consisting of unstratified bowlder drift and modified or stratified drift. The southern limit of these deposits and of the marks of glaciation is about lat. 40° N. The crystalline rocks to the north of them present hard, smoothly worn, or striated surfaces, except in some protected localities; but further southward they are generally decayed or softened to a greater or less depth, sometimes 100 ft. or more, from a process of chemical change. The great elevated western or Rocky mountain region differs widely in general features from that just described. Upon the broad area of crystalline rocks, which reproduce on a grand scale the characteristics of the Appalachian belt, are found all the members of the palæozoic series, overlaid for the most part by older mesozoic rocks and by a great thickness of cretaceous and tertiary strata, in which each one of the three great divisions of the latter is well represented. These newer rocks constitute vast arid plains, and in the cretaceous and eocene or lower tertiary strata the great coal deposits of this region are found. These strata have been disturbed by great faults, penetrated and overflowed by vast volumes of eruptive rocks, and subjected to erosion on a grand scale. The crystalline rocks which bound the great palæozoic basin of the United States to the east and the north are rich in ores of iron, and include also gold, copper, lead, nickel, and chrome. The native copper of the S. shore of Lake Superior belongs to a peculiar group of strata, unknown elsewhere, lying at the very base of the palæozoic series. Various horizons in the palæozoic rocks, up to the coal inclusive, abound in ores of iron, and in the Mississippi valley in lead, zinc, and copper; while salt and petroleum occur at several horizons in the palæozoic series in different parts of the