SURVEY OF COLORADO AND NEW MEXICO. 79 



'■- It seems to me tliat these beds are Jurassic, or mucli newer tlian tlie 

 carboniferous, but in the upheaval have fallen clown below the carbon- 

 iferous limestones, which have been lifted far up in the ridge beyond. 

 As we ascend the ridge which forms the- southwestern rim of the South 

 Park, we meet with what appears to be the same black shales and sand- 

 stones on the summit, which we saAV some hundreds of feet lower in the 

 small park. 



The South Park is completely surrounded with gigantic ranges of 

 mountains, and inside of them the sedimentary rocks, when exposed, 

 seem to dip toward the center of the park. Indeed, I should regard the 

 South Park as one immense quaquaversal. 



Around the salt works is a group of laminated sandstones, mostly 

 brown and gray, overlaid by a great thickness of light gray gypsiferous 

 marl with a bed of crystallized gypsum four feet thick. The valley in 

 which the salt springs are located is covered with an efflorescence of 

 what is usually called in this country "alkali." On the east side of the 

 creek which runs past the salt works is a high isolated balsatic butte. 

 About a fourth of a mile east there is a hill composed of the gypsiferous 

 marls, on the surface of which are numerous deposits of calcareous tufa, 

 as if a number of springs had issued from it in former times. 



These salt works are quite extensive and costly. The springs are two in 

 number, but the brine is not abundant or strong. Salt has been manu- 

 factured here in considerable quantities, and a large portion of Colorado 

 has been supplied with it. These springs are very interesting in a geo- 

 logical point of view, though their origin is somewhat obscure to me, 

 yet I believe they belong to the triassic or saliferous sandstones. 



About four miles north of the salt works is a high ridge, inclining 

 northwest twenty degrees, composed of a series of variegated sandstones 

 and shales three hundred to four hundred feet thick. These are, with- 

 out doubt, the grou[> which I have usually called triassic, or red beds. 

 Still further north we find them inclining southeast, with several thin 

 beds of blue, very hard, cherty limestone, which is characteristic of the 

 red beds. JSTear Fairplay the brick-red beds are well shown. It seems, 

 therefore, certain that the principal sedimentary rocks which are found 

 in the South Park are triassic. 



About ten miles south of Fair]^lay several thin beds of blue, close, brit- 

 tle limestone appear, intercalated among the red sandstones, dipping a 

 little east of south, forming a sort of synclinal; that is, the dip is nearly 

 opposite that of the beds near the salt works. These limestones, with 

 the red sandstones, may possibly be of permian age. No fossils could 

 be detected in them. The sandstone is in some cases micaceous, or 

 composed of mica and small crystals of quartz; in others, a fine aggregate 

 of worn pebbles, a sort of fine pudding-stone. These variegated or red 

 beds continue close up to the eruptive ranges for five miles. IsTorth and 

 west from Fairplay we come to a high ridge of sandstone with a reddish 

 tinge and slightly calcareous, the dip being north of east, or nearly east, 

 and the ridge forming a marked line running nearly north or south 

 through the middle of the park, from the mountains nearly to the salt 

 works. Just east of this ridge is another ridge of quartzose sandstone or 

 cretaceous. Then comes a very large thickness of the laminated creta- 

 ceous clays, covering the country for about fifteen miles. Near McLaugh- 

 lin's, twelve miles northeast of Fairplay, the lignite tertiary sandstones 

 and clays overlie the cretaceous and jut up against the mountain side. 

 About a mile north of the ranch Mr. McLaughlin has opened a coal mine. 

 He sunk a shaft eighteen or twenty feet through a bed six to ten feet of 

 very impure coal; some portions of it can be used for fuel. The dip of the 



