-,i> S. P. EMMON OROGRAPHIC MOVEMENTS. 



I' \ Hills — representatives of the Laramie Dot yel haviug been definitely 

 recognized, possibly through having been eroded away. 



Unconformably below these beds come a series of marine 1>«-«1> of lower 

 Cretaceous age, known as the Comanche Beries, which have been traced 

 through Texas southward into Mexico, the base of which is formed by the 

 Trinity beds, or Dinosaur .-amis, which resemble the AUantosaurus beds of 

 the Rocky Mountain region. These rest unconformably upon the underly- 

 ing beds, which in most cases thus far observed arc found to be of Carbonif- 

 erous ;i 



N representatives of the Comanche beds have yet been found in the 

 Rocky Mountain region nor in the Plateau province; but from near the 

 international boundary, in about longitude 115°, the Canadian geologists 

 have traced a Beries of marine Cretaceous beds stretching northward into 

 British Columbia, known as the ECootanie beds, which are lower than the 

 Dakota Cretaceous. From the plant ami molluscan remains found in these 

 beds Mr. George M. Dawson* regards them as equivalents of the Comanche 

 series (though perhaps not reaching quite as far hack in geological time), 

 and of those developed on the Pacific coast in Queen Charlotte's island, and 

 considers that they were once connected with the latter north <>t' the 54th 

 parallel. 



Th <ir>'ii Plains. — As early as 1877, Dr. Whitef called attention to the 

 probability of a post-Jurassic subsidence which carried the eastern shore-line 

 of the interior M - / lie ocean eastward across the < rreat Plains and permitted 

 the deposition of Dakota beds in central Iowa, which subsidence continued 

 through Fort Kenton and Niobrara times, causing a Btill further eastward 

 extension of the shore-line and a corresponding change in the character of 

 the sediment- from diallow to deep water. 



Since that time evidence has Keen found at various point- throughout the 

 area of elevation, folding and erosion of the underlying beds previous to 

 this subsidence. 



r n the Raton mountains, some sixty miles east of Trinidad, Cretaceous 

 lied- reel unconformably on steeply upturned Triassic -ami-tone-. North of 

 this, at Fort Lyons, on the Arkansas river, an artesian boring disclosed a 

 tit thickness of Jurassic beds interposed between the Trias ami Creta- 

 Further east and north, through Kansas and Nebraska, the Dakota 

 Cretaceous rests in places on Trias, at other- on Permian or Carboniferous 

 beds. The chalk beds, which in Texas correspond to the lime-tune- of the 

 Niobrara along the foot-hills of the mountains, have also been found in 

 eastern Kansas, and recently in Nebraska as I'm- west a- the L03rd meridian. 



General Conch -The present distribution of Mesozoic Bediments in 



\m JOUI I . V., I. WW III, 1880, !•. 1-". 



; ii • • • for i-TT, p. jsu. 



