238 , W. H. HOBBS ORIGIN OF OCEAN BASINS 



area of the intercontinental sea, we find Barbados, a small isolated block 

 with deep-sea radiolarian ooze resting on sandstone, clay, and coal of 

 Tertiary age and indicating a change of level since Tertiary time of about 

 6,000 feet.* 



Symmetry about the North Atlantic 



It is also quite recently that Suess has expressed the view that the 

 North Atlantic was formed as the result of depression on lines of dis- 

 location along its borders. His earlier studies on interrupted zones of 

 folding! had shown that three great folded arcs may be traced from east 

 to west across Europe, though they are now present in isolated fault- 

 bounded remnants only (such, for example, as the Black forest, Vogesen, 

 Thuringian forest, Morvan) — the Caledonian, Armorican, and Alpine 

 arcs. These studies were in 1898 extended^ so as to include the Amer- 

 ican as well as the European side of the Atlantic. It is shown that in 

 Europe the Armorican folds and the Hebrides, composed of ancient 

 crystalline rocks, appear to be but the eastern ends of much larger 

 masses, and it is suggested that under the northern portion of the Atlan- 

 tic ocean an Archean region is buried, and farther south a folded arc on 

 which the Upper Carboniferous rests unconformably. 



"It is a very remarkable fact that the east coast of North America actually 

 corresponds to these assumptions. Here, with the exception of some possibly 

 Caledonian stretches, there appear but two tectonic elements, and they possess 

 essentially the properties characteristic of d (Armorican folds, Ed.) and / 

 (Hebrides, Ed.). They are separated by the straits of Belle isle and the lower 

 course of the Saint Lawrence. 



"To the north lies the broad Laurentian Archean mass, the Canadian shield, 

 which extends beneath the horizontal Paleozoic sediments of the Arctic- 

 American archipelago, probably far toward the pole and reaching over also to 

 Greenland. 



"To the south of it, in the Rias coasts of Newfoundland, Nova Scotia, and 

 New Brunswick, rises a folded range with discordantly transgressing Upper 

 Carboniferous, which carries the marks of the western continuation of a great 

 folded zone with the same clearness that in Europe the Armorican zone bears 

 of an eastern end." 



James Perrin Smith has called attention to the fact that in Cretaceous 

 and Eocene time the Atlantic shore American fauna had many species, 



* W. T. Blanford : Anniversary address of the President of the Geological Society of 

 London. Quart. Jour. Geol. Soc, vol. 46, 1890, pp. 59-110. 



t Ed. Suess : Ueber unterbrochene Gebirgsfaltung. Sitzungsb. d. k. Akad. d. Wlss. z. 

 Wien, vol. 94, 1886, Abth. I, pp. 111-117. 



t Ed. Suess : Ueber die Asymetrie der nordlichen Halbkugel, ibid., vol. 107, 1898, 

 Abth, J, pp, 89-X02. 



