20 REPORT UNITED STATES GEOLOGICAL SURVEY. 



occasional calcareous layers, the sandstone layers often containing masses a,n(l uodulea 

 of chert. Thickness about 600 feet. 



No. 12. Middle Carboniferous. — Compact, bluish fossiliferous limestone, heavily or 

 thinly bedded, alternating in some places with strata that are sandy and ferruginous. 

 Thickness about 1,000 feet. 



No. 13. Loioer Carboniferous. — Massive layers of limestone alternating with those of 

 sandstone and sandy limestone ; all more or less ferruginous, generally presenting a 

 reddish-brown aspect ; and all usually regularly bedded. Thickness about 1,500 feet. 



No. 14. Uinta sandstone. — Massive or thiuly bedded, brick-red or more usually brown- 

 ish-red sandstones; usually hard and often quartzitic. Thickness, exposed' in this 

 district, only about 400 feet ; but the group reaches a thickness of nearly or quite 15,000 

 feet in the Uinta Mountains only a few miles from this district. 



The districts surrounding the one here reported upon have, within the 

 last few years, been geologically surveyed by different persons. That 

 which adjoins it on the west has been reported upon by Professor Powell 

 in his " Geology of the Uinta Mountains." A geological map of the dis- 

 trict which adjoins this one upon the north has been prepared by Mr. 

 Clarence King during the progress of the United States Geological Sur- 

 vey of the Fortieth Parallel. Keports, to be published sinaultaneously 

 with this, are in course of preparation by the other geologists of the 

 United States Geological Survey of the Territories, on the other districts 

 which adjoin this one. A few copies of Mr. King's map have been dis- 

 tributed to different persons and institutions in advance of a geological 

 report which is no doubt intended to accompany it. An examination of 

 this map shows that the author has, in the main, adopted the classifica- 

 tion of the strata which he finds exposed in that district, which has long 

 been in use by Dr. Hayden in his reports ; but with certain modifica- 

 tions in some cases. As no text yet accompanies Mr. King's map, I am, 

 in some cases, in doubt as to the intended limits of the respective gioups 

 of strata that are there named and represented by colors. Having, how- 

 ever, made some personal examination of a large part of the region rep- 

 resented by that map, I think I do not incorrectly represent its intent 

 in the following table of general sections. A large proportion of the 

 names of the different groups of strata which are used in this report are, 

 by the custom of priority in such cases, adopted from Mr. King's map, 

 which is regarded as having been published in November, 1875. Mr. 

 King's name, " Laramie Group," although it is understood to embrace 

 strata that have previously received other names in different parts of 

 the great Kocky Mountain region, is retained because of its more com- 

 prehensive application as indicating a great period in geological history, 

 which is epochally represented by the Fort Union, Judith Eiver, Lig- 

 niiic, and other series of beds. 



Dr. Hayden's name, "Wasatch Group," has, however, priority of pub- 

 lication over Mr. King's name, "Vermilion Creek Group," and also over 

 Professor Powell's name, " Bitter Creek Group," and 1 therefore adopt 

 the first-mentioned name. I adopt the name "Weber Quartzite" of Mr. 

 King for the great formation that Professor Powell has called the " Uinta 

 Sandstone," but not being in possession of Mr. King's facts, I am not yet 

 prepared to adopt his reference of it to the Carboniferous age. Al- 

 though the typical locality of the Lodore Group, which Professor Powell 

 represents as existing at the base of the Carboniferous series and above 

 the Uinta Quartzite, is near the northern border of the district here re- 

 ported on, it does not occur within its limits. Professor Powell's sec- 

 tion alone, therefore, represents it in the table. 



Although Mr. King has not upon his map recognized the deposit called 

 " Brown's Park Group" by Professor Powell as separate from the Green 

 Eiver Group, north of an east and west line that may be made to pass 

 through the southern base of the great Uinta fold, a careful comparison 



