kxdiich.] WIND EIVER RANGE CARBONIFEROUS. 75 



"We observed some Spirifers, Orthis, Crinoids, and Orthoceras. In some 

 of the calcareous sandstones indistinct remains of fish-scales were found. 

 From what has been said of the relative position of the strata compos- 

 ing this group, it will be seen that in its horizontal projection it essen- 

 tially follows the western base of the third chain. Extending from the 

 northern border of our district, it remains exposed until hidden from 

 sight by the superincumbent Tertiary beds a short distance southeast of 

 Miners Delight. It again makes its appearance at the Sheep Mountain 

 Group. The recurrence there will be the subject of discussion in subse- 

 quent pages of this chapter. 



Carboniferous. 



Under this head I comprise the middle portions of the formation. The 

 entire series located between the upper limits of the Lower Carboniferous 

 and the beginning of the Permian beds is one of great uuiformity. Blue, 

 massive limestones, exhibiting but few variations, compose the entire 

 mass. Near the base of the series, which is located at about the lower 

 third of the high, outlying hills, we find that some of the strata still 

 retain a slightly dolomitic character. This is of no orographic impor- 

 tance, however, as neither in color nor mode of weathering they show 

 any appreciable difference from beds higher up. Ascending towards the 

 summits of the hills we find that the strata become very massive and are 

 composed of blue, rarely whitish, limestone. Some strata may be found 

 where this is crystalline. Numerous- fossils are inclosed within these 

 rocks, nearly all of them silicified. This style of petrifaction has resulted 

 very disastrously to the preservation of exterior form. Evidently the 

 process by which the substitution of silica for the original material com- 

 posing the shell was effected, is one of infiltration. Had the progress of 

 this replacement been a perfectly regular one, i. <?.,had the removed par- 

 ticles of calcium carbonate been replaced immediately by silica, the re- 

 sult would have been different. Instead of a complete pseudomorph, 

 however, we find but partial ones, rendering the details and often even 

 general form of the fossils very imperfect. 



Throughout the limestones of this group we observe large quantities 

 of siliceous concretions. They occur in numerous shapes. Either nar- 

 row veins, irregular inclusions, geodes lined with brilliant crystals, or 

 seams filiiug systems of small fissures, traverse the entire rock. Flint, 

 jasper, chalcedony, hornstone, basanite, and white or yellow quartz, com- 

 pose these included masses. They may be regarded as typical for this 

 group of -the Carboniferous formations. Although they extend down- 

 ward into the underlying strata, they are not found in the same large 

 quantities, neither are they so persistent in then horizontal and verticle 

 distribution. 



There were but few fossils obtained from this group, owing to their 

 mineralogical character. Among those found were Productus semistria- 

 tm, Spirifer, Orthis, Athyris, Crinoids, and near the base Orthoceras. 



Following the Carboniferous group southeastward from the northern 

 border of our district, we find that it composes the bulk of the outlying 

 hills. Dipping almost uniformly toward the northeast, the angle of in- 

 clination is about 30° to 40°. Toward and on the western slopes of the 

 hills, we find it somewhat larger than farther eastward. As we proceed 

 along the eastern slope of third chain, we find it cut transversely by 

 the various streams of the Wind Eiver drainage. First, we cross the 

 North Foik, Baldwin's Creek, and some smaller tributaries. These pass 

 through open gaps which break the continuity of the hills. Maintaining 



