1897-98]- HIGH PLATEAU AND SUBMARINE ANTILLEAN VALLEYS. .159 



RESEMBLANCES BETWEEN THE DECLIVITIES OF HIGH 



PLATEAU AND THOSE OF SUBMARINE 



ANTILLEAN VALLEYS. 



By J. W. Spencer, M.A., Ph.B. 



(Read February 5, i8g8). 



In the " Reconstruction of the Antillean Continent,"* the writer 

 brought together a vast number of data showing that everywhere 

 crossing the southeastern coastal plains of North America, the rivers 

 flow over deeply-buried ancient channels before entering the sea, 

 thus indicating a submergence of the land. The direction of these 

 rivers is mostly transverse to the mountain range as well as to the 

 coast lines. Beyond the sea shores, and amongst the West Indian 

 Islands, there are extensive submarine plateaus, regarded as Mio- 

 Pliocene plains, now submerged at various depths between 2,500 and 

 5,000 feet. These are dissected by fjords, or drowned valleys, of great 

 depth, which are found to be continuations of the land valleys. They 

 are traceable to depths of more than two miles, and receive tributaries 

 converging from all possible directions. These submerged river systems 

 are recognizable in all portions of the Antillean basins, and the more 

 important of them are described in the " Reconstruction of the Antillean 

 Continent." They are shown upon the accompanying map. 



In the previous paper on " Late Formations and Great Changes 

 of Level in Jamaica,"f the drowned plateaus adjacent to that island, 

 and their dissection by the deep channels, are described. The 

 phenomena show the recent extension of continental lands so as to 

 include the Jamaican mass, as illustrated on the accompanying map. 

 The dissection of these plateaus is of much more recent date than the 

 formation of the drowned plains. Upon the adjacent lands these 

 channels dissect the Lafayette formation of America, the Matanzas of 

 Cuba, and the Layton of Jamaica, which appear to be local equivalents 

 of widespread accumulations, resting unconformably upon the old Mio- 

 Pliocene land surfaces ; consequently, these drowned canyons and deep 



* Bull. Geol. Soc. Am., vol. vi., pp. 103-140. 1894. 

 t Trans. Can. Inst., vol. v., pp. 32S-3S7. i8q8. 



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