42 SURVEY OF COLORADO AND NEW MEXICO. 



what I have called an abrupt anticlinal ; that is, only the abrupt side of 

 the western slope appears here. The eastern side has either been worD 

 away or was never elevated to a great height, and is now concealed 

 by the recent deposits. The summit of the metamorphic ridge projects 

 far over the base of the mountains, and the western side of the monocli- 

 nal shows a gentle slope. That this eastern portion of the metamori)hic 

 anticlinal may have been elevated and then fell back, or may not have 

 been elevated at all and still exists beneath, is shown from the fact that 

 the sedimentary ridges or "hog-backs" gradually diminish in dip to the 

 point of concealment. 



The little streams which flow into Monument Creek, as well as the 

 creek itself, cut through a coarse material of various colors with irregu- 

 lar layers of deposition. Sometimes a layer is hardened into a coarse 

 sandstone, and then comes a thin layer of ironstone or impure limonite, 

 but the whole is a quartzose material and rather coarse. There are now 

 and then thin seams of fine sand or clay. ISTear the stage station there, 

 is a bluff of rather massive whitish sandstone, with some thin beds of 

 clay at intervals. There is much iron in these rocks, and this aggregates 

 in the form of a rusty layer, quite hard. The light-colored sandstones 

 below are weathered into most singular columnar or monument-like 

 forms, with this layer of rusty sandstone as a cap protecting the summits. 

 There are some dark bands of arenaceous clay, and in the sandstone a 

 few rounded concretions. 



About six miles north of Colorado City the upheaved ridges or "hog- 

 backs" reappear from beneath the quartzose sandstones of the Monu- 

 ment Creek group. The white massive sandstones of the lower creta- 

 ceous lie high on the mountain side. The first ridge that we pass through 

 along the road is a whitish brown, rather yielding sandstone, with rusty 

 yellow portions, with very irregular laminae of deposition. The strike 

 is southNvest and northeast, and the dip 32°. This is a bed of the lig- 

 nite tertiary. 



High up on the sides of the mountains, for ten miles or more about 

 the Soda Springs, there is a great thickness of red porphyritic granite, 

 inclining from the mountains in well-defined ridges, like sandstone. 

 From their very deep rusty-red color, I regarded them as sandstones 

 until I made a close examination of them. They have a well-marked dip 

 of forty-five to fifty degrees, somewhat less than the massive granite 

 rocks which form the nucleus. All these ridges rise like steps toward the 

 range of which Pike's Peak forms a part, with the sloping sides toward 

 the northeast and the summits leaning over toward the axis of elevation. 



These very red granitoid rocks have formed a very conspicuous fea- 

 ture on the eastern side of the mountains for thirty miles or more north 

 of Colorado City; and, as they readily decompose, the hills and roads 

 are jiaved with the crystals of feldspar and quartz. The constituent 

 which predominates is feldspar, which gives the red color. This rock is 

 composed of a coarse aggregate of quartz and feldspar with a little black 

 mica, and now and then a little pencil-like crystal of hornblende. The 

 rock itself does not seem to be so red, but the debris has a dull rusty- 

 red color in the distance. Upon the summits of the mountains about 

 Pike's Peak are columns of massive granite — immense rounded masses, 

 standing one upon the other, giving a most picturesque appearance to 

 the scenery, and affording fine illustrations of the style of weathering. 



The unchanged rocks are here seen resting directly upon these dull 

 reddish granites. The lower beds are composed of a more or less fine- 

 grained sandstone, with some small pebbles, variegated in color, passing 

 up into rocks of a semi-crystalline textiu^e. Most of the rocks apj)ear aa 



