10:2 E. Sims — Paleogeography of North America. 



by folding, of which both halves or sides form parts of the 

 same tectonic unity. This is not the case with the great "syn- 

 clinoria" in front of the mountain chains, the "Vortiefen" or 

 "fore-depths" [see ibid., IV; 626]. 



The great Pacific fore-depths of 7,000 to more than 9,000'" 

 are evidently not caused by folding, as one side is formed by 

 the foreland (mostly covered by the ocean here) while the 

 other is the front of a folded chain. This is clearly visible 

 wherever such a fore-depth enters the continent, as for exam- 

 ple in the valley of the Ganges, where one side is the Penin- 

 sula (=Gond\vana land), and the other the Himalaya, or the 

 valley of Guadalquivir in Spain between the old foreland of 

 the ]VIeseta in the north and the young folded cordillera (Betic) 

 in the south. It is clear that the Pacific Asiatic volcanoes 

 have nothing to do with these depths; they always remain 

 inside the more or less arched chain of mountains. The folds 

 of the cordilleras advance towards the depths and seem to 

 reach them. Sometimes the depths are filled with very thick 

 masses of terrestrial sediments, coming from the new-born 

 cordilleras, sometimes with deep-sea sediments having Badio- 

 laria, as in front of the Carpathians and parts of the Eastern 

 Alps. I regard the thousands of feet of Carboniferous sedi- 

 ments, partly marine and partly continental, which accompany 

 the front of our pre-Permian chains extending from Silesia to 

 southern England as the filling of such a fore-depth. Marcel 

 Eertrand was right in drawing a line from the Bretagne to 

 Newfoundland and in regarding the Appalachian coal fields as 

 the continuation of those of southern England, Belgium, etc. 

 All this is in harmony with the remarkable words of Dana on 

 the existence of a greater trough or deeper channel on either 

 side of the Azoic nucleus and perhaps also gives a hint as to 

 the northern limit of your Poseidon ocean. But this trough 

 is no synclinorium and no anticlinorium exists.* 



It will be too great a digression for me to describe here the 

 great Asiatic depths and I prefer to write briefly of the diffi- 

 culty which arises from the fact, that a transgressing sea enters 

 a fore-depth in one case and an extended river valley in an- 

 other. Then, too, the contour may be very similar, but the 

 thickness of the deposits is by far greater in the fore-depth. 

 The Cretaceous Flysch with Fucoides and Inoceramus has 



* "The region toward the Atlantic border, afterward raised into the Appa- 

 lachians, was already then, even before the Lower Silurian era closed, the 

 higher part of the land" (319). "We hence learn that in the evolution of 

 the continental germ, after the appearance of the Azoic nucleus, there were 

 two prominent lines of development, one along the Appalachian region, the 

 other along the Rocky Mountain region— one, therefore, parallel with either 

 ocean. Landward, beyond each of these developing areas, there was a great 

 trough or channel of deeper ocean waters, separating either from the Azoic 

 area " (344). Dana, this Journal, vol.'xxii, 1856. 



