216 THE DEVONIAN AND CARBONIFEROUS. Ibull.80. 



Section IX. Aubrey Cliff, at Canon Creek, north Arizona. — Rocks consist of alter- 

 nating sandstones, limestones, and shales. Total thickness, 2,3G0 feet. 



Section X. Carrizo Creek, north Arizona. — Rocks consist of yellow sandstone and 

 dark gray fossiliferous limestones. Total thickness, 1,420 feet. 



Section XI. North fr^m and near Camp Apache, Arizona. — Physical characters simi- 

 lar. Total thickness, 2,260 feet. 



Section XII. Spring Mountain, Nevada. — Total thickness, 2,395 feet. 



Section XIII. Ophir City.— Fossils numerous. Thickness, 1,975 feet. 



The occurrence of Lower Carboniferous and Devonian rocks is some- 

 what questionable, except at Ophir City. The author also reported the 

 discovery at the top of the "Aubrey limestone" of a few fossils suggest- 

 ing the Pernio- Carboniferous of the Mississippi Valley. 



The Carboniferous formations of northern Arizona and in the Grand 

 Caiion were classified as follows : 



Feet. 



Aubrey limestone — Aubrey Valley, north Arizona. 820 



Auhrey sandstone — (no fossils except in an intercalated limestone helow the 



middle — a few Coal Measure fossils) 1,000 



Red Wall limestone — named from the red appearance of escarpments in Grand 



Cafion 2,500 



The above names were proposed by Mr. Gilbert and Mr. Marvine. 



The middle of the Ked Wall limestone furnished fossils which Mr. 

 Meek doubtfully referred to Lower Carboniferous. The upper portion, 

 by its fossils, was correlated with the Coal Measures. 



It is stated that Mr. Marcou, in the Geology of North America, had 

 called the Aubrey limestone " Permian," the sandstone " Coal Meas- 

 ures," and the Eed Wall limestone "Carboniferous limestone or Mount- 

 ain limestone." Mr. Gilbert referred to the local character of the sed- 

 imentation in the Grand Canon ; that 75 miles westward he was unable 

 to correlate the series in detail. Mr. A. E. Marvine, in the same vol- 

 ume, reported the identification of beds between the Black Mesa and 

 the Sunset tanks as " ? Permo-Carboniferous." x 



Mr. A. J. Brown reported in Pancake Mountain a vein of coal which 

 was regarded by the author as probably the first carboniferous coal 

 discovered west of the Bocky Mountains, unless some of the Utah coals 

 belong to this age. This vein is worked at the north end of this range 

 of hills, about 14 miles west of Hamilton. It has a thickness of from 

 5 to 6 feet, with a dip of 40° to the west. 2 



In 1876, Mr. J. W. Powell presented a classification of the sediment- 

 ary rocks of the Plateau Provinces. 3 



In this classification the Aubrey group of Mr. Gilbert is divided into 

 the upper and the lower Aubrey groups. The upper Aubrey group 

 consists of sandstone and cherty limestone of 1,000 feet thickness, seen 



1 Report on the geology of route from St. George, Utah, to Gila River, Arizona, examined in 1871, 

 by A. R. Marvine, pp. 189-225. 



2 Carboniferous coal in Nevada, by A. J. Brown, Trans. Am. Inst. Mining Eng., vol. 3, 1875, pp. 31-33. 

 'Department of the Interior. IT. S. Geol. and Geogr. survey of the Territories, 2d division. J. W. 



Powell, geologist in charge. Report on the geology of the eastern portion of the Uinta : Mountains 

 and a region of country adjacent thereto, by J. W. Powell. Washington. 187C. 





