CHAPTER X. 



DEVONIAN AND CARBONIFEROUS CORRELATIONS IN THE WEST- 

 ERN AND NORTHERN PROVINCES. 



In the Rocky Mountain region and the western part of the United 

 States and in British North America are large tracts of territory which 

 have been roughly surveyed, and in places with sufficient detail for the 

 correlation of the grand geological divisions; but in little of this region 

 have the details of either the stratigraphy or the paleontology been 

 worked out with sufficient minuteness to permit of fuller correlations than 

 with the systems of other parts of the world or their upper or lower 

 parts without precise reference to limits. The literature concerning these 

 correlations will be reviewed chronologically in the present chapter, be- 

 ginning with the Hayden reports of 1868, prior to which date little of 

 interest for this essay can be gleaned. 



In 1868, Mr. F. V. Hayden, in the American Journal of Science, 1 gave 

 a brief report of the results of his examinations of the geology of the 

 Rocky Mountains, in which some generalizations are made based upon 

 his wide knowledge of the region. The object of this paper was to 

 show that quite marked lithological and paleontological changes occur 

 in the rocks of the Rocky Mountains as we proceed from the north 

 southward. The nucleus of the mountains at any one point along the 

 eastern range is composed of massive granite rocks; then follows a series 

 of metamorphic rocks. Upon these the Silurian period is represented 

 by the Potsdam sandstone; the Devonian is wanting; then follow the 

 Carboniferous, Red Beds, Jurassic, Cretaceous, Tertiary. 



There is no marked change in the Tertiary from the North to the 

 Arkansas River, but many changes were observed in the Cretaceous. 

 The Jurassic thins out to the southward, as do the Red Beds or sup- 

 posed Triassic. In the far north the Carboniferous rocks are often 500 

 to 1,500 feet in thickness, and from 500 to 1,000 feet thick as far south 

 as the Red Buttes, and are quite distinct from the Red Beds, but the 

 latter prevail farther south. The Carboniferous rocks become of a red 

 arenaceous character, with a few layers, from two to ten feet in thick- 

 ness, of a whitish or yellowish limestone. Dr. Hayden could find no 

 break to separate the Red Beds from the Carboniferous, and concluded 

 they might possibly all be of that formation. The Potsdam sandstone 



1 Hayden, F. V. : Remarks on the geological formations along the eastern margins of the Rocky- 

 Mountains'. Am. Jour. Sci., vol. 45, 1868, pp. 322-326. 



