REPORT OF THE SECRETARY. 53 



for the purpose of establishing with greater accuracy the natural series 

 of geological formations. A small party was organized for this purpose, 

 and was led by Professor Powell himself The main party under Prof. 

 A. H. Thompson, geographer of the division, continued the work daring 

 the past season in the Territory of Utah, over an area of nearly ten thou- 

 sand square miles, stretching from the Henry Mountains, on the north, 

 to the Kai-par-o-wits Plateau on the south, and from the Colorado River, 

 on the east, to the Aquarius Plateau, on the west. 



It was found that of the lands surveyed the past season, one-fourth 

 of 1 per cent, can be utilized by irrigation ; about 50 per cent, are pas- 

 ture-lands; about 9 per cent, are of timber; 4 per cent, mineral-lauds; 

 and the remainder desert. 



Mr. G. K. Gilbert studied the structural geology of the country, and 

 collected the materials for a geological map. 



A second and closely allied subject of study has been the eruptions that 

 produced the Henry Mountains, a third has been the erosion by which 

 the structure has been laid bare, and a fourth, the Salina Creek un- 

 conformity. The investigation at Salina Creek was of a special nature, 

 and its bearings cannot be briefly stated. Its results establish a single 

 point of geological history, namely, that an epoch of mountain-growth, 

 of which evidences are found in the Sevier and Sanpete Valleys, and in 

 the Pahvan Mountains, occurred at about the end of the Cretaceous 

 period. 



The stratified rocks examined range in age from Carboniferous to 

 Tertiary. Upon the geological map the combined Trias and Jura will 

 cover half the space. The volcauic area will come next in size, and after 

 that the Cretaceous. The excellence of the topographic work will 

 enable a very thorough delineation of their boundaries. 



Fossils were found in numerous localities, but no large collections 

 were made. 



Coal of cretaceous age was seen, but no other valuable minerals. 



Captain C. E. Dutton was engaged m the examination of a large tract 

 consisting of igneous rocks. It lies in Southern Utah, its northern 

 boundary being about one hundred and fifty miles south of Salt Lake 

 City, extending thence southward about eighty -five miles, and having 

 a breadth of about sixty miles. It consists of a series of long, narrow 

 tables with intervening valleys, and is structurally a repetition of those 

 features described by Professor Powell as characteristic of the whole of 

 Southern Utah and Northern Arizona, and which have led him to call it 

 the Plateau Province. The tables are cut from the platforms of the val- 

 leys by immense faults and uplifted from 2,000 to 5,500 feet above the 

 valley-plains, presenting nearly vertical walls, fringed at their base by 

 rugged foot-hills. The plateaus are composed of thick beds of igneous 

 rocks well stratified and nearly horizontal; the foot-hills, on the con- 

 trary, are composed of beds much broken and disturbed and intermixed 

 with lava. The southern portions are overlaid by a conglomerate which 



