218 ANNUAL REPOET SMITHSONIAN INSTITUTION, 19 3 2 



Carboniferous, or at least Permo- Carboniferous, rocks occur also in 

 Bear Island and Spitsbergen. 



From the Carboniferous onward there is evidence that very little in 

 the way of first-hand sediment was derived from what may be termed 

 outside sources. It has been shown that the Carboniferous Rocks 

 supplied the greater part of the breccias and sandstones of Permian 

 age in the north of England, while in the Midlands the material was 

 largely derived from local sources. 



The conditions of the Trias were very similar, except that, as Dr. 

 H. H. Thomas has shown, the land lying to the south of the British 

 Isles was an important contributor. 



Messrs. Greenwood and Travis, who made a detailed mineralogical 

 examination of the Trias of the Wirral district, concluded that the 

 Bunter had previously formed part of an earlier arenaceous deposit 

 of granitic character, while the Keuper was derived at first hand from 

 igneous granitoid rock situated near the site of the present Wirral 

 Peninsula, 



The Jurassic sediments have not as yet been the subject of detailed 

 study, though there appears little evidence of far-derived material in 

 the investigations that have so far been made. 



In Northeastern America there is also no evidence that there was 

 any great accession of freshly derived sediment from the Atlantic 

 region after Carboniferous times. 



The North Atlantic region, either by reason of its peneplanation 

 or its subsidence, had ceased to play an active part in the supply 

 of material for building up new lands on its periphery, though 

 the shore lines traceable in the Scottish area through the Mesozoic 

 period indicate that land still lay to the north and northwest. 

 It is of some interest to note that every transgression of the British 

 area by marine waters came from the south and the southeast, the 

 two most notable instances, of course, being at the beginning of 

 Mesozoic time with the Rhaetic and the still more complete Ceno- 

 manian transgression. 



VII. THE CHARACTER OF THE LAND MASS: ITS SIZE AND POSITION 



It has been shown that in the three great epochs, Torridonian. 

 Old Red Sandstone, and Carboniferous, when the interpretation of 

 the sediments has led me to infer renewed uplifts of the land mass 

 from which the fresh sediments of these periods were derived, the 

 mineralogical contents of these sediments are of granitic type 

 (crushed and metamorphosed in places) with fresh and unaltered 

 feldspars, principally microcline, microcline-microperthite, and oligo- 

 clase, and the heavy minerals confirm this conclusion. Basic rocks 



