National Geographic : 1893 Jul 10
86 C. D. Walcott-The Geologist at Blue Mountain. that portion of the North American continent then above the sea is thought to have consisted of (1) a large part of what is now the British possessions; (2) a long, broad mountain area (Atlantic) extended southwestward from Newfoundland to the present site of the Gulf of Mexico and it may be the West Indian archipelago, (3) and one or more areas (Pacific) on the western side of the continental plateau, on the line of the present Rocky mountain and Sierra Nevada ranges.* The eastern or Atlantic area and the bed of the interior sea toward the west, in what may be called the Appalachian trough, were then formed of variouss kind of rock, including granite, schists of various kinds, crystalline and unaltered sedimentary rocks and, in some localities, of great masses of volcanic material that had been poured out over the surface in very much the same manner as were the relatively recent lavas found in the vicinity of the Yellowstone National Park and in various parts of the Rocky mountain region. The waves of the interior sea wore away from the western shore of the Atlantic land area various rock materials and depos ited them along with that brought in by the brooks and rivers as layers of sand and gravel on the sea-bed all the way from the present site of the Saint Lawrence river to Alabama. In these deposits fragments of the volcanic rocks, schists, etc, were min gled, and spread out in sheets. At times the supply of ma terial was very fine and formed thin layers of mud that after ward consolidated into shales and slates. After a deposition of several thousand feet of this character of materials the water deepened, probably by the subsidence of the bed of the sea and calcareous muds were deposited during a great interval of time until in places they reached the thickness of several thousand feet. These now form the limestones found in the Cumberland and Shenandoah valleys and their extensions northward to Canada and southward to Alabama. All along this ancient coast line, from Labrador to Alabama, various forms of marine life existed, and their hard parts, such as shells of crustaceans (allied to the living king crab) and other organisms, were buried in the mud and sand. The deposition of sediments in the sea, immediately west of the Atlantic area, continued until from 12,000 to 40,000 feet in thickness were piled over the ancient sea-bottom, layer upon * See article on the North American Continent during Cambrian Time, in Twelfth Ann. Rep. U. S. Geol. Survey, 1892, pp. -.
1894 Jan 31
1893 May 05