662 GEOLOGY 



Colorado and perhaps at other points, there is an unconformity 

 at the top of the Permian. 1 The presence of Permian in New 

 Mexico, 2 northern Arizona 3 and the Wasatch Mountains, sugg< 

 that the Permian sea perhaps extended west from Texas as far 

 as the Great Basin for a part of the period; but if so, the continuity 

 of the beds has since been interrupted by erosion. A very consider- 

 able thickness of marine Permian (3,800 feet) is reported from 

 Utah. 4 The Permian deposits of the far west, as well as some of 

 those in the longitude of Texas and Kansas are often red. This 

 color so often characterizes formations known to have been made 

 in inclosed basins, that the connection can hardly be fortuitous. 



Thickness. In the Appalachian region, the Lower Permian 

 beds, sandstone and shale with thin seams of coal, have a thicknc 

 of about 1,000 feet. The Upper Permian is wanting. In Kansas 

 the thickness is twice as great, while in Texas it reaches 7,000 feet. 



Correlation. In the region east of the Mississippi, the Permian 

 is so closely associated with the Coal Measures that the two were 

 formerly classed together. Were this region only considered, 

 this classification would appear to be satisfactory. In the western 

 part of the continent, on the other hand, the separation of the Per- 

 mian from the Carboniferous will probably prove to be more distinct, 

 when details have been worked out, and its relation with the Trias 

 close. The Permian period is best looked upon as a transition 

 period from the Carboniferous to the Trias, and so from the Paleo- 

 zoic to the Mesozoic. Its close relationship to the underlying system 

 in some places, and to the overlying system in others, is therefore 

 to be expected. 



THE FOREIGN PERMIAN 



Europe 



In Europe, as in America, the Carboniferous period was brought. 

 to a close by very considerable changes, for much of the area which 



1 Cross, and Cross and Howe, Bull. G. S. A., XVI, 447; Silverton Folio, 

 U. S. Geol. Surv., and Jour, of Geol., Vol. XV, p. (>:;i. 



2 Herrick, Jour. Geol., Vol. VIII, pp. 112-125; and Am. Geol., Vol. X X X I, 

 p. 76. 



3 Walcott, Am. Jour. Sci., Vol. XX, 1880, p. 221. 



4 Boutwell, Jour. Geol. XV, p. 434. 



