,534 KANSAS CITY RE VIE IV OF SC/EA'CE. 



GEOLOGY. 



JURA-TRIAS. 



G. C. BROADHEAD. 



In 1880 we observed the geological structure around Las Vegas, New Mexi- 

 co, and in 1881 similar rocks were observed in Southern Wyoming. 



Hayden (Colorado and New Mexico, 1869,) speaks of the granites and 

 gneisses of Las Vegas; above these the carboniferous with fifty feet of red sand- 

 stone still above and free from fossils which he calls Triassic, and still above he 

 assigns over 300 feet of red and gray sandstone to the Jurassic; from the latter 

 he obtained only a Mytalus. Still above this, geologically, is the well known 

 " Hog back ' of light colored sandstone assigned by Hayden to No. i Cretaceous. 



I observed the following : Up the canon of Gallinas Creek above the Hot 

 Springs, the archasan red granite forming the mountain nucleus arises in bold es- 

 carpments for over 500 feet, and still further back reaches still higher in the 

 mountains. Nearer the Springs we find darkly banded gray gneisses. 



On the south side of the valley the carboniferous limestones rise up for sev- 

 eral hundred feet. Their texture and general appearance and fossils are those of 

 the lower coal measures of Missouri. Among the fossils I observed Fusulina 

 Cylindrica, Chcztetes Milleporaceus, Lophophylliim proliferum, Athysis subtilita, Spirifer 

 cameratus, Productiis longispinus. Higher up on the mountain side, north, I ob- 

 tained a fragment of a species of Lepidodendron from a: coarse sandstone, resem- 

 bling a species from lower coal measures of southwest Missouri. 



Passing down the valley of Gallinas Creek we observe red beds similar to those 

 Hayden describes, but I obtained no fossils. So I would be slow in offering an 

 opinion as to their geological age, but they are certainly of more recent age than 

 those carboniferous rocks above named. 



Nearly a half mile below the Springs a beautiful red sandstone very promi- 

 nently obstructs the course of the stream. This rock affords the fine building 

 stone used extensively at the Springs in constructing the hotel, baths, etc. Pass- 

 ing a half mile or more east of the Springs we ascend the famous "Hogback" 

 formed of nearly white sandstone on edge and almost obstructing the entrance to 

 the valley of the Springs. Eastwardly the rocks gradually become horizontal 

 and are certainly cretaceous. The crest of the "Hogback," for some distance, 

 seems Hke a marked out road with walls on each side, and from the top a very 

 fine view can be obtained of the valley extending toward the old town of Las 

 Vegas and beyond, as well as Upper Las Vegas and the Atchison, Topeka & 



