294 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 2 8 



Turning now to a more recent and still wider exhibition of basic 

 extrusions, during the early Oligocene basaltic lavas and ashes were 

 poured out on Scotland and Ireland, the Faroe Islands, Iceland, 

 and the eastern and western coast of Greenland. In the detrital 

 beds accumulated between the lava flows, fossil leaves of forest 

 trees are preserved, testifying to a warm temperate climate at that 

 time in Greenland; they also indicate a close relationship between 

 the lands, suggesting connection at that time. Geikie estimates the 

 thickness of the basaltic series in Iceland at 10,000 feet, and in 

 northwestern Greenland at 4,000 feet. The flows are scattered over 

 a distance of 1,800 miles and their superposed sheets underlie sepa- 

 rate plateaus whose edges face the ocean in steep scarps. It would 

 appear, therefore, as if the oceanward continuations of these lava 

 plateaus had foundered. Between these widely separated regions 

 it seems probable that still larger areas of basalt must occur, which 

 are now at the sea bottom. 



These basalt-covered lands are portions of the ancient continent 

 Eria, which connected northeastern Canada and northwestern Europe. 

 Let us note first what the paleontologists have to say as to the date 

 of its foundering, drawing their evidence from the fossil mammals 

 found on the two sides of the ocean, and without considering the 

 basaltic magmas as a cause for the separation of the lands. Schuchert 

 states : ^* 



Greeuland and the region eastward across Norway, Sweden, and Finland 

 (Fennoscandia) were subject to great block faultings or warpings previous to 

 the Pliocene, developing not only great rifts or graben but broad sinking areas 

 as well, with a general trend to the northwest and southeast. This was the 

 time when Eria was broken through, separating Laurentia from Baltiea. 

 Previous to the Middle Miocene this land was the bridge that enabled the 

 mammals of Europe and North America to intermigrate. Periodically, but 

 more especially during the Oligocene and Miocene [late Eocene and Oligocene], 

 lava flowed widely through fissures over all these lands, the Faroe Islands, 

 Scotland, and northern Ireland (Giant's Causeway). This foundering of the 

 crust where the Norwegian sea now is, permitted the triumphant spread of the 

 Atlantic into the Arctic Ocean. 



The sea bottom between Greenland, Scotland, and Scandinavia is 

 less than 6,000 feet deep, and therefore only about one-half the mean 

 depth of the ocean. Assume a mean subsidence of 6,000 feet due to 

 the intrusion of rocks which after solidification were 10 per cent 

 heavier than the rocks which they displaced. This would require the 

 intrusion of a mean thickness of 60,000 feet. The extrusions would 

 be but a fraction of this, as judged by other regions where abyssal 

 rocks are exposed, the extrusions serving only as an index of the 

 greater masses below. The intrusions would presumably cover as 



" Charles Schuchert, Pt. II of the Piersson-Schuchert Textbook of Geology, pp. 923, 

 924. 1915. 



