Williams.) RICHARDSON, GILBERT. 215 



thein to Zaphrentis and Syringopora, one species of the latter and two of 

 the former. They were the first fossils of the Upper Helderberg period 

 brought to light from the range of the Wahsatch. 



Mr. James Richardson, 1 in 1874, reported a few fossils from, and gave 

 a section, of Ballinac Island, consisting mainly of epidotic rocks, diorite, 

 and reddish limestones, carrying well preserved fossils of encrinites, 

 corals, and brachiopods. He considered that the " age of these rocks 

 is either Carboniferous or Permian, most probably the former." 



In the third volume of the report upon the geographical and geologi- 

 cal explorations and survey west of the 100th meridian, Mr. GL K. Gil- 

 bert reported identifications of sections made in the canons and other 

 regions west of the Rocky Mountains. 2 



In southern Nevada, the rocks of the Spring Mountain Range consist 

 of fossiliferous limestones, with bands of sandstone of Carboniferous 

 age. The strata seem to be conformable throughout the whole vertical 

 range. Again, in the Black Hills, Arizona, sedimentary rocks of Car- 

 boniferous aspect were seen overlying a crystalline series similar to those 

 noted in Bowlder Caiion. In Arizona the plateaus consist of Carbon- 

 iferous limestone (Aubrey limestone, Red Wall limestone). The adja- 

 cent ranges show the Tonto sandstones. The exploration of the Colo- 

 rado plateau system showed that the rocks which compose it range 

 from Eocene Tertiary to the Tonto group, which underlies the Carbon- 

 iferous rock of the Grand Caiion of Colorado. The next bench below 

 that, named by Powell the u Shinarump Mesa," is capped by a Carbon- 

 iferous limestone extending from Paria Creek southwest to Aubrey 

 Valley. Through this section the Grand and Marble Cations have cut 

 their way. After giving a general topographical description, and at the 

 same time referring to the geologic age of the rocks in general, the author 

 adds a series of twenty-one vertical sections, indicating physical char- 

 acters and thickness, together with fossil remains. These sections are 

 finally correlated in tabular forms, thus giving a view of the whole 

 vertical range. Of the twenty-one sections given, Upper Carboniferous 

 rocks occur in the following : 



Section V. Jacob's Pool. — The rocks consisting of massive sandstones, alternating 

 with gypsiferous cherty clay-shale and chocolate shale and cherty limestones, con- 

 taining Product™ Meekella, Pseudomonotis, Hemipronitis,- Aviculopecten, etc. Total 

 thickness, 3,750 feet. 



Section VI. Kanab Creek.— Physical character of rocks similar to those of Section 

 V; additional fossils in cherty limestone. Fenestella (?) Spirifera lineatus, Orthis, 

 Chonetcs, etc. Total thickness, 4,200 feet. 



Section VII. Grand Canon. — Kocks similar to those of Section VI. Total thick- 

 ness, 4,825 feet. 



Section VIIL Aubrey Cliff, 15 miles southeast of Bill Williams Mountain, Arizona.— 

 Rocks, limestones and yellow-red friable sandstones. Total thickness, 2,100 feet. 



1 Richardson, James : Report on geological explorations in British Columhia. Geol. Survey Canada ; 

 Report of Progress for 1873-74. 1874, pp. 94-102. 



2 Report on the geology of portions of Nevada, Utah, California, and Arizona, examined in the years 

 1871 and 1872, hy G. K. Gilbert, A. M., pp. 17-187 of report upon the geographical and geological explora- 

 tions and survey west of tho one hundredth meridian. 1875. 



