CONTINENTAL TERRESTRIAL SUBMERGENCE. 19 



The first paper read was — 



TERRESTRIAL SUBMERGENCE SOUTHEAST OF THE AMERICAN CONTINENT 



BY J. W. SPENCER 



[Abstract] 



Only an abstract of the paper is offered to the Society for publication, as the 

 author proposes farther investigations before writing on several questions closely 

 related to the principal phenomena bearing upon the problem. This paper is a 

 sequel to "High Continental Elevation preceding the Pleistocene Period," read 

 before the Society August, 1889. At that time, epeirogenic movements of 3,000 

 feet seemed the limit of acceptability, although terrestrial elevation of probably 

 short duration was shown to have reached from 4,500 to 6.000 feet along the conti- 

 nental margins, off the gulfs of Saint Lawrence and Maine and the mouth of the 

 Mississippi river. 



Recent studies of the valleys among the southern Appalachian mountains, of the 

 adjacent Paleozoic table-lands, and of the Cretaceous and Tertiary plains of the south- 

 eastern states have convinced the author that the valleys, whether narrow or a score 

 of miles or more in width, have been directly produced by atmospheric agents and 

 by the erosion of a multiplicity of streams operating during the long periods neces- 

 sary for the decomposition and removal of limestones. Some idea of the length of 

 these periods is obtained when we find that from 100 to 200 feet of residual sandy 

 clays have been left after the removal of the calcareous matter from the impure 

 limestones. These southern valleys are independent of the mountain movements, 

 in so far that they are not troughs of folds but anticlinal valleys. Even at the water- 

 sheds between streams flowing in opposite directions, the width and depth of the 

 valleys are as often great as that between Lookout and Wills creeks or those along 

 the Coosa and Tennessee rivers, where they are from 4 to 20 miles wide. 



The valleys and channels among the greater Antilles and between them and the 

 continent are an exact reproduction of the land valleys of the south. On a larger 

 scale, the Laurentian valley, holding the Great Lakes, is another example, but this 

 has been recently obstructed by the tilting of the earth's crust toward the north 

 and east — the warping movement increasing from zero to two, four, six and prob- 

 ably even ten feet per mile. From the close analogy cited, the author concludes that 

 both the land and the submerged Antillean valleys were of common subaerial origin. 



Of the submerged valleys and channels there are two classes— those cutting across 

 the continental shelf and others parallel to the mountain ridges. Of the former 

 class, the fjord of the Mississippi river reaches to 4,500 feet in the upper platform 

 and in the lower shelf to a depth of 8,000 feet. Cochinos bay, south of Cuba, is 

 one of the most remarkable fjords, being 3,738 feet deep near the head of the bay 

 and increasing in depth to 11,400 feet, with land on one side and shallow water on 

 the other. The Yucatan fjord, entirely submerged, increases from a depth of 4,500 

 feet to 10,000 feet. The Bahaman fjord on the Atlantic margin of the continent is 

 12,000 feet deep. Scores of other examples can be cited, as in Jamaica, Haiti, 

 adjacent to the Virgin islands, etc. (See accompanying map.) 



Of the valleys parallel with the trend of the islands, there may be cited the 

 Haitian channel, more than 500 miles long and reaching to a depth of 14,000 feet. 

 Another example is seen in the channels between Haiti and Cuba, which descend 



