HAYDEX.] 



GEOLOGY COLORADO RANGE. 31 



of Bear Creek and its branches tliese lower conglomerate-beds fit into 

 tbe irregularities of the surface of the Metamorphic rocks in a marked 

 manner. Little streams flowing from the mountain-sides have cut excel- 

 lent cross-sections, showing the original deposition of the Triassic (?) 

 sandstones in deep depressions of the granite nucleus. We may say here 

 that the coarseness of the sediments of the lower beds of the Eed group 

 is not the only evidence of the disturbed condition of the waters that 

 deposited them ; all through the group are quite remarkable illustrations 

 of irregular and obliquelamination. These examples are shown onagrand 

 scale immediately after the Saint Vrain emerges from the granites. There 

 is a considerable valley between the coarse, reddish, feldspathic granites 

 and the first principal ridge of sandstone which has been worn out by the 

 water, but remnants of the conglomerate have beenleft, filling up the irreg- 

 ular granitic surface. The Saint Yraiu here runs southward parallel with 

 the ridges for about three miles, and then turns to the east and cuts 

 through the ridges at right angles, and flows into the plains past Long- 

 mont. Just south of the point where the creek cuts through the belt 

 of sandstones, the parallel valley closes up and the ridges lie close up 

 on the sides of the mountain. Here the group of sandstones which we 

 have usually classed as Triassic exhibits a great variety of structure. 

 The conglomerates rest on the coarse feldspathic granites, and the 

 basset edges of the sandstones rise like a wall on the east side of the 

 creek. There are alternate beds of sandstone of various degrees of 

 firmness as well as hardness to resist the atmosphere, and softer layers 

 of sandy clay. The beds of sandstone thicken or thin out at remarka- 

 bly short distances. At one locality on the east side of the creek, the 

 most important bed of sandstone expands within a distance of 200 

 yards from 50 to 250 feet in thickness, and affords some of the most 

 remarkable examples of oblique lamination, the lamina inclining 10° to 

 17<^. Here we have quite a broad interval for several miles or more be- 

 tween the granite foot-hills and the uplifted sedimentary ridges, pro- 

 duced bj^ the excavation for the drainage of the Saint Vrain. Soon the 

 ridges lie close on the sides of the granite, and continue more or less 

 closely to Clear Creek, South of Clear Creek narrow intervals occur 

 again to a point about five miles south of the caiion of the South Platte. 

 Just south of the Big Boulder the red sandstones seem to have been 

 partially changed by heat, and the ridges rise in lofty walls 1,500 to 

 2,000 feet above the plain, presenting a front which has no parallel in 

 any other locality along the eastern flanks of the mountains, from the 

 northern boundary to New Mexico. 



About five miles south of the South Platte Caiion we come to the 

 divide between the drainage of the main Platte and Plum Creek, where 

 the sedimentary rocks jut up against the sides of the mountain so that 

 the slope is continuous from the tops of the granite foot-hills down into 

 the valley. This divide is quite narrow, and southward we soon descend 

 into an interval again between the granite foot-hills and the sedimentary 

 region. Between the Platte Caiion and this divide there seems to have 

 been an unusual hardening of the Eed group, and the action of the eroding 

 agencies must have been peculiar, for the sandstones present a more 

 picturesque appearance than at any other locality, not excepting the 

 "Garden of the Gods'- at Colorado Springs. The "main ridges seem to 

 have split up into a multitude of irregular ones, and the fragments now 

 stand up inclining eastward 30^ to 50° in the shape of leaning columns 

 and spires, the ragged upper edges presenting almost every variety of 

 form which the meteoric forces could produce. These fragmentary 

 forms rise out of the grass and bushes which grow abundant all around 



