62 ' SURVEY OP COLOEADO AND NEW MEXICO. 



CHAPTER V. 



FROM FORT UNION TO SANTA Fl5. 



We left the hospitable post of Fort Union with regret and pur- 

 sued our way southward towards Las Vegas. The first eight miles we 

 passed over qnartzose sandstones of No. 1, and then appeared above 

 them a hard bluish limestone, which belongs to No. 2. The sandstones 

 of No. 1 gradually disappear, and the limestones take their place. 

 Several species of Inoceramus occur, and Mrs. General Grier has in her 

 possession an Ammonites that came from this region, which is tubercn- 

 lated like A.percarmatus. All the way to Las Yegas we have a fine view 

 of the country along the base of the mountains. The exposures of the 

 sedimentary rocks are wonderful in their extent along the eastern base of 

 the mountains, from Fort Union to the point below Santa Fe, where the 

 range passes out and is lost in the plains. The belt of npheaved ridges 

 is from four to eight miles wide. All around Las Vegas, in the plains, 

 the blue limestones, passing up into an enormous thickness of the black 

 shales of No. 2, is 'everywhere seen. The little streams cut deep chan- 

 nels through it. 



The finest section of the sedimentary rocks of this region, that I have 

 ever seen, may be found between Las Vegas and the Hot Springs, on 

 Gallinas Creek. The beds from the metamorphic to the cretaceous, 

 inclusive, are so regularly and clearly exposed along this (.'reek that it is 

 not possible to mistake their continuity, and I would call the attention 

 of all travelers visiting this country, who have any interest in the 

 geology, to it. 



The Hot Springs, which have already become so celebrated for their 

 supi)osed curative qualities in certain diseases, are located about five 

 miles northwest of Las Vegas, just at the junction of the carboniferous 

 and the gneissic rocks. The lowest spring issues from the granite just 

 underneath a mass of limestone. The bed of limestone that rests directlj' 

 on the granites is quite hard and cherty, with a dip nearly southeast 40° 

 to 45°. The metamorphic rocks below are rotten gneiss. From this point 

 outward towards the plains I made the following section, passing over 

 the upturned edges as they were exposed with wonderful clearness and 

 consecutiveness to the eye : 



1. Hard grayish cherty limestone, resting, directly on the gneiss. 



2. Micaceous sandstone full of iron, partly a very micaceous rotten 

 shale. 



3. Yellow limestone with less chert, excellent for lime, containing 

 Froductus, two or three species, Spirifera stibtilita. Between the beds of 

 limestone, that vary from four to twenty feet thick, are tNvo beds of 

 rusty clay, each four to six feet thick, tbe whole dix)ping 50°. 



4. Black shale with thin layers of a sort of arenaceous mud, from 

 one-quarter of an inch to four inches in thickness. 



5. himestoneswith Productns, Spirifera, corals and crinoidal stems, pass- 

 ing up into a very cherty limestone, one hundred and fifty feet thick; 

 dip 60° to 75°. Among the layers of limestone are thin seams of shale. 



6. Grayish brown arenaceous limestone passing up into a somewhat 

 micaceous sandstone — 30 feet. 



7. Variegated greenish, reddish, ashen, and yellowish shaly clays — 

 20 feet. 



8. Variegated sands and sandstones of all degrees of fineness. The 

 prevailing color red, varying from bright brick-red to purjile, with some 



