36-4 DYKAMICAL GEOLOGY. 



Denver, first by Marvine (1873), is of the Laramide system; and it is con- 

 tinued south through Huerfano County, into New Mexico along by the Raton 

 coal-field (C. S. Hills). Still farther south upturned Cretaceous beds extend 

 along the trans-Pecos region of western Texas, and thence into Mexico. But 

 the limits of the several ranges and their relation to the Laramide system 

 need further study. 



The sketch in Fig. 337, from the west slope of the Elk Mountains, in 

 Central Colorado, shows a sigmoid twist in the stratification of the 

 rocks, the highest in the series being the Cretaceous ; the warping of the 

 strata is strikingly exhibited. W. H. Holmes has sections of flexures and 

 flexure faults of the Elk Mountains in the Hay den Expedition Report for 

 1874, two of which are closely like the form obtained by Daubree in his 

 experiments (Fig. 326, page 351). 



337. 



Hafjai.-iMi 



Upturned strata of the west slope of the Elk Mountains, Colorado. The light-shaded stratum, Jura-Trias; 

 that to the right of it, Carboniferous; that to the left, Cretaceous. Hayden's Report. 



Igneous ejections attended the mountain-making in many parts of the 

 upturned region, from Wyoming southward, and some volcanoes may date 

 from this epoch. 



4. Tertiary Orographic Movements along the Pacific Mountain border. 



1. The great geanticline. — At the close of the Cretaceous period the 

 latest beds lay at or near the sea level; and after the making of the 

 Laramide mountain-chain the region was still but little above this level. 

 During the Tertiary era following, especially after the Miocene period, a 

 gradual elevation of the mountain region went forward ; and now, as the 

 result, the same Cretaceous strata in some parts of Colorado are 10,000 to 

 11,000 feet above the sea. From this level the height slowly diminishes to 

 4000 feet and less near the Arctic coast and to twice this in Mexico. 



The region thus placed these thousands of feet above the sea level 

 probably included the whole of the Pacific mountain border, from, the line of 

 the Mississippi Valley to the Pacific coast line, and outside of this line for one 

 or more scores of miles. The vast geanticline was made without correspond- 

 ing flexures of the rocks ; there were only minor local bendings, upturnings, 

 and faults. It was a very slow movement upward, continuing probably into 

 the Quaternary. That it made little progress in Eocene time is proved by 



