jj^YPEN.] GEOLOGY ELK MOUNTAINS. 63 



texture, though all evidently of igneous origin. The jointage is in many 

 cases vertical, separating the mass into blocks varying in size from a 

 few inches to 2 or 3 feet cube. This vertical jointage gives a sort 

 of columnar appearance to the sides of the peak in the distance. 

 The sides are also deeply furrowed. There are three sets of master- 

 joints, with a multitude of smaller ones. The consequence is that the 

 sides of the mountain and the several amphitheaters are covered with 

 immense quantities of debris. The whole mass is filled with water 

 and ice during the winter, and in the spring, as the ice and snow melt, 

 it moves down the declivities slowly, like a glacier. Sometimes cavities 

 or reservoirs are made, and the melted snows form beautiful little lakes. 

 From the summit of Whiterock Mountain, which rises 13,563 feet 

 above sea-level, the eye sweeps over a scene of apparent chaos on every 

 side. There is a' wilderness of high peaks with deep gorges extending 

 out in every direction, 2,000 to 3,000 feet deep. The entire range is 

 composed of what may be called upthrusts of igneous granite; that is, 

 the granite is thrown up most irregularly, at various elevations, from 

 beneath the overlying sedimentary beds ; sometimes carrying i)ortions 

 to the summits, or tilting them from the sides at various angles, or leav- 

 ing them 2,000 or 3.000 feet below. While there are numerous points 

 of upthrow in this region, there seem to be a number of foci of greatest 

 X)Ower. The Snow Mass group and Whiterock Peak may be regarded 

 as illustrations of tremendous upward force. From the summit of White- 

 rock Peak the deep gorges with nearly vertical walls for 2,000 or 3,000 

 feet in depth, showing sections of the rocks as perfect as if cut down by 

 human agency, can be seen on every side. We can see the junction of 

 the stratified sedimentary beds with the granitic core. The variety of 

 coloring to these groups is due to the different degrees of heat to which, 

 they have been subjected. The lowest group of sedimentary beds, 

 although exhibiting all the stages of metamorphism, is usually of a 

 yellowish-brown color, and made up of quartzites and impure lime- 

 stones. I regard them as of Silurian age, and most probably Lower 

 Silurian 5 500 to 800 feet are shown in this vicinity, but the aggregate 

 thickness must be much greater. Then above this group there is a 

 series of maroon or deep puri)lish-brown sandstones, quartzites, and con- 

 glomerates. These vary much in color, from a light brick-red to a 

 purplish-brown or maroon color. They reach a thickness of at least 

 1,500 feet, and probably more. This group is probably of carbonif- 

 erous age. Ii may be found capping the highest peaks of Elk Moun- 

 tains, over 14,000, feet above sea-level, and is weathered into unique 

 forms of cones, pyramids, &c. The third series is a bright brick- 

 red, and is probably of Triassic age. No one has, as yet, found 

 any organic remains in any of these beds, and therefore we can only 

 express a belief in regard to their age, strengthened by observations in 

 adjacent portions of the district. From the summit of Whiterock 

 Mountain the view on every side is most remarkable, presenting the 

 aspect of chaos, as if the entire group of stratified rocks, which, origi- 

 nally covered the area now occupied by the Elk Mountains, had rested 

 on a vast pasty mass of the granite, but which, by forces generated, iu 

 this pasty mass, had been lifted up and tossed, as it were, in every direc- 

 tion. The faults are very numerous and of huge dimensions. Some- 

 times a group of strata is broken off, so that one portion is from 100 

 feet to 2,000 feet above the other portion. Sometime's 1,000 to 2,000 

 feet will be elevated by a force acting very nearly vertically, so that 

 some of the loftiest peaks, as Maroon Peak, 14,000 feet ; Black Pyramid, 

 13,000, and many others nearly as high, are composed entirely of strati- 



