1G2 GEOLOGICAL SURVEY OF THE TERRITOKIES. 



CHAPTER Y 

 FROM FORT UNION TO SANTA FlS. 



We left the hospitable post of Fort Union v/itlr regret and pur- 

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

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

 them a hard bluish limestone, which belongs to jSTo. 2. The sandstones 

 o : No. 1 gradually disappear, and the limestones talie their place. 

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

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

 lated like A.percarinatus. All the v^ay to Las Vegas 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, Vt'here the 

 range passes out and is lost in the plains. The belt of upheaved 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 ISTo. 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 creek that it is 

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

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

 geology, to it. 



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

 supposed 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 directly 

 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 

 Productus, two or three species, Spirifera suhtilita. Between the beds of 

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

 rusty clay, each four to six feet thick, the whole dipping 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. Limestones with Productus^ Spirifera^ corals and crinoidal stems, pass- 

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

 dip 00° 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 purple, with some 



