60 SURVEY OF COLORADO AND NEW MEXICO. 



rocks. The sedimentary rocks all incline in the same direction, at varions 

 angles, from five to seven degrees. I cannot see that in this vast series of 

 ridges, any hedslsave been repeated, and, therefore, there must be exj)osed 

 here in a curiously consecutive manner from eight thousand to ten thou- 

 sand feet, at least", of sedimentary rocks. The junction of the unchanged 

 rocks with the gneissic beds is rather obscure, but abed of limestone 

 seems to incline against them. From my observations from Las Vegas 

 to Santa Fe, I am satisfied that all along the mountains the carboniferous 

 limestones rest directly on the granitic rocks. The valley of the Mora, 

 in which the town of that name is situated, is one of the most fertile 

 and beautiful that I have ever seen in the West. It is almost entirely 

 surrounded by mountain ranges, and in the aggregate it forms a high 

 quaquaversal — that is, the rocks seem to incline from all directions 

 toward a common central point. It is about ten miles long from east 

 to west, and two miles wide from north to south. It is in the form of a 

 cross. At the east side is a long valley extending five miles or more 

 in each direction north and south from it. Either one of these valleys, 

 taken separately, would form a synclinal. The whole valley is in part 

 worn out of the gneissic rocks. Mora Creek runs directly through it 

 and every acre of it is under cultivation, and with the rude Mexican 

 style of farming, produces most abundant crops. 



All around this valley the slopes of the mountains show clearly that 

 the metnmorphic rocks incline from it at very high angles; and all 

 around the borders are foot-hills or low ridges, the remnants that are 

 left after erosion, which .^how distinctly the direction of the dip. But 

 the series of gneissic beds on the east side of the valley are very interest- 

 ing, consisting of alternate beds of black banded gneiss, and a 'Coarst' 

 aggregate of feldspar and quartz. Some of the beds are composed pt; 

 mottled gneiss. These beds all incline to the west or northwest, at various 

 angles from twenty degrees to thirty degrees. This series of gneissijc'^ . 

 strata extends nearly half a mile, and is plainly a remnant left after 

 erosiou. They incline in an opposite direction to the unchanged rocks — 

 that is, there is no conformity. This is one of the most interesting points 

 on our route in a geological point of view, and I regretted very much 

 that I could not remain a longer time. 



About northeast from Fort Union there is a small range of mountains 

 of some interest, called Turkey Hills. They seem to form a regular up- 

 heaval with a line of fracture nearly northwest and southeast, and appar- 

 ently independent of the volcanic forces that have once operated all around 

 it. This mountain is well covered with timber, and the highest points rise 

 fifteen hundred to two thousand feet above the level of the plain at Fort 

 Union. Entering the mountains nearly north of the fort, we pass up a sort 

 of anticlinal valley ; the beds inclining in each direction at a small angle. 

 None but the lower cretaceous sandstones and a portion of the upper 

 series of red-beds are exposed anywhere in this range, which is about 

 twenty-five miles long and ten miles wide. Among the red:beds are two 

 or three layers of bluish limestone, and underneath the cretaceous is a 

 bed of fine-grained whitish sandstone, which I am inclined to regard as 

 Jurassic. From the summits of these mountains we can see the Spanish 

 Peaks, Eaton Mountains, and, indeed, the whole country round about 

 for a radius of one hundred to one hundred and fifty miles. About nine 

 miles east of Fort Union there is an old volcanic crater of great interest. 

 This is the nearest ajjproach to recent volcanic indications that I have 

 ever seen, or known on the east side of the mountains. The rim of 

 the crater is circular and well defined, though the depression is very 

 shallow. Yet, as we ascended the high volcanic mountain, we found the 



