36 EXPLOBING EXPEDITION FBOM SANTA FK 



C H A. P T K R I I . 



GEOLOGY OF THE VICINITY OF SANTA FK. 



General geological features— Santa Fe Mountains— Granite— Its character and 

 contained biinrrals— Relations of the Santa Pe Mountains— Placer .Mountains — 

 Cretaceous and Triassic rooks— Oretaoeous lignite converted into anthracite 

 ijv an outburst of trap— Gold of the Placer Mountains — Copper— Iron — The 

 Cerrillos — Gold— Silver— Lead— Copper— Iron— Turquoise — ancient Ohalohuitl 

 Minks— The Sandia Mountain— The Valles— Stratified rooks— Carboniferous 



FORMATION — SANTA FE SECTION— SECTION AT PECOS VILLAGE— PERMO-CARBONIFEROUS 



beds— Gypsum formation— Section at San Jose— Fossil plants— Cretaceous forma- 

 tion — Subdivision of the system— Yellow sandstones of Oanon Blanco Creta- 

 ceous—Sections at Gallisteo and Pope's Well — Tertiary beds of fresh-water 



ORIGIN. 



The region about Santa rY has occupied the attention of several geologists who 

 have visited New .Mexico, among whom .Messrs. Wislizenus, Marcou, and Blake have 

 given full reports of their observations upon it. I also was able to devote a short time 



to its study while connected with the party of Lieutenant Ives in 1858, a rfewmA of 

 the observations then made being given in my report to that officer. It might, there- 

 fore, be supposed that this subject was by this time freed from all obscurity, and, per- 

 haps, exhausted of all interest. This is, however, far from being true, as may be show n 

 in few words. The geological structure of that region is complicated by several distinct 

 lines of upheaval, which have been classed together in the so-called Rocky Mountain 

 system; and vet the relations of these groups and chains of mountains are far from 

 being fully understood, or at least demonstrated. They have been regarded, perhaps 

 justly, as of the same age, but, as will be seen, when we come to speak of them more 

 in detail, evidence of complete synchronism is yet wanting, while there arc some facts 

 which seem to point to a contrary conclusion. 



Aside from the obscurity which hangs over the erupted rocks, an obscurity that 

 cannot be dissipated without much careful study in the field as well as in the labora- 

 tory, the splendid exposures of the three great groups of sedimentary strata, the Car- 

 boniferous, the Triassic, and the Cretaceous — to say nothing of the Tertiary beds 

 largely developed, bu1 without fossils — deserve and demand for their full analysis more 

 time than has vet been devoted to them. The three months spent in the vicinity of 

 Santa Fe during the past season by our party have, I trust, not been entirely without 



