. Elements of geology : a text-book for colleges and for the general reader. Geology. THE INTERVAL. 295 Archaean marginal sea-bottom was raised into land, and at the same time crumpled. In c, the same was eroded, so that the edges of strata Arch yean Land. Fig. 267.—Ideal Section, showing how Unconformity was produced on the Canadian Border: S L, sea-level. were exposed. This was during the interval. In d, the land sank again to the primordial shore-line, and the Palaeozoic era commenced. During the Palaeozoic the land gradually rose so as to expose successive sea-bottoms of Cambrian, Silurian
. Elements of geology : a text-book for colleges and for the general reader. Geology. THE INTERVAL. 295 Archaean marginal sea-bottom was raised into land, and at the same time crumpled. In c, the same was eroded, so that the edges of strata Arch yean Land. Fig. 267.—Ideal Section, showing how Unconformity was produced on the Canadian Border: S L, sea-level. were exposed. This was during the interval. In d, the land sank again to the primordial shore-line, and the Palaeozoic era commenced. During the Palaeozoic the land gradually rose so as to expose successive sea-bottoms of Cambrian, Silurian, Devonian, and Carboniferous ages. It has remained substantially in this condition ever since. We have spoken thus far only of the uncomformity of the New York rocks on the Canadian rocks. This phenomenon may be ex- plained, as we have seen, by local oscillations, with increase and decrease of land-area during the lost interval. But, when we remember that the same unconformity is found in the most widely-separated localities, over the whole area of the United States, we are forced to the conclu- sion that the lost interval, as compared with the Silurian, was probably a continental period—a period of widely-extended land composed of Laurentian rocks. The whole of this land disappeared by submergence at the beginning of the Primordial, except the Canadian area, a large area east of the Appalachian, and probably a considerable area in the Basin region, and perhaps a few islands or larger areas in the Primordial seas between, as shown in map, Fig. 266. In all speculations on the origin of the animal kingdom by evolu- tion, it is very necessary to bear in mind this lost interval, for it was evidently of great Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original LeConte, Joseph, 1823-1901. New York : D.
Size: 1951px × 1281px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1892
