*T:^vj>l.-t 



f-r -^ — l^-^^■X- ^^i^V 



HAYDEN'S SUKVEY. 



513 



Uinta Mountains, p. 70). Hence, as it appears, considerable difTerenco 

 of opinion exists as to its age. Mr. S. F. Emmons apparently inclined 

 to regard it as Cambrian (Descriptive Geology, p. 199), while Professor 

 MarsU and Dr. C. A. White thought it j)robablo that it was Siiuriau 

 (Am. Jour. Sci., 1871, (3) L, p. 193 ; Annual Keport, 1876, p. 23). In 

 his Annual Ileport for 1871, (p. 39,) Dr. Haydon remarked : 



" The precious metals, as gold and silver, are found, so far as my observa- 

 tions have extended, entirely in the metanxorphic rocks wlxidi hold a position 

 below all groups of strata that we have been in the liabit of regarding as Pale- 

 ozoic. "Whether they belong to the scries denominated in Canada the Huronian 

 or Ijaurentian, we have no data to decide positively ; but inasmuch as they are 

 all clearly stratified rocks, they are plainly of sedimentary origin." 



In the Report for 1873, Dr. Ilayden stated that 



" the underlying metamorphic rocks [near South Park] are made up in part of 

 quart/itic sandstones, full of rounded pebbles of quartz, which would hidicate 

 that they might belong to the Laurentian series." {I. c, p. 41.) 



In the Eeport for 1874, (pp. 190, 191, 239,) Dr. F. M. Endlich held 

 that the granite and other so-called metamorphic rocks were formed 

 from the metamorphosis of the Siiuriau and Devonian rocks in the dis- 

 trict studied by him.* These rocks appear to be the same as those 

 called Archeoan by the other members of the Survey. (See als-^ Report 

 for 1875, p. 113.) 



In the Annual Renort for 1875, Dr. A. C. Pcalo makes the following 

 statement : — 



" SuIIicient data have not yet been obtained to determine the exact age of the 

 metamorphic series, altlnjugh, as Marvine remarks of those farther east, [An- 

 nual Report, 1873, p. 139,] ' tlie prevalence of siliceous and granitic types recalls 

 the descriptions of Laurentian areas.' In one place the schists are very dis- 

 tinctly Btratified, consisting of dark micaceous schists, with seams of (Quartz 

 and feldspar. These may be of Iluronlau age, although we cannot trace their 

 relations to those of the other Archjean rocks, as they are exposed in an isolated 

 area at the bottom of callons distant from the other outcrops.'" (Z. c, p. 04.) 



::»' 



In tlic Annual Report for 1877, (p. 15G,) Dr. F. M. Endlich, in a 

 tabular view of tlie formations of the Sweetwater district, divides the 

 Azoic rocks into three systems. The oldest of these, called Prozoic, 



consists of massive granite. The third, called Huronian, likewise con- 

 sists of granites, less massive than those of the first system, and con- 



* Tlio area between the meridians of 107" and 108°, and the puralluls of 37° 15' 

 and 38° 15', al the head of the Kio Grande and the Eio Auinjas. 



VOL. VII. — NO. 11. 33 



