REPORT OF THE STATE GEOLOGIST. lxxxvii 



have no such evidence in the way of springs to prove their value, and 

 no boring has been carried far enough to test the matter, although pre- 

 parations are now under way to do so. No rocks of similar age have 

 been observed in the Guadaloupes. We must therefore conclude that 

 while the artesian conditions of the Central Basin are not unfavorable, 

 the probabilities are against securing an adequate supply of water suffi- 

 ciently free from mineral matter to be of use for general purposes (un- 

 less it be from the sandstones of the Guadaloupe Mountains, which 

 would require sinking to impracticable depths in most places). All ex- 

 ceptions will be of purely local extent and will require much local topo- 

 graphic and geological work for their designation. 



There still remains the area of the Staked Plains formation to be dis- 

 cussed, but our knowledge of its geology is too limited to permit any- 

 thing but the most general statement. The upper portion of these plains 

 is composed of strata of later Tertiary or possibly Quaternary age, under- 

 laid by a conglomerate and sandstone of earlier date than the Trinity 

 Sands, dipping southeast. It^isthis bed that furnishes the surface water 

 of the Plains, and from it gush the headwaters that form the Colorado, 

 Brazos, and Eed rivers. The beds underlying this are probably Per- 

 mian on the southern border, but newer formations may intervene to- 

 wards the north. It is possible that this conglomerate bed may yield 

 artesian water near the western border of the State, and I understand 

 that one such well has been secured. It is my opinion, however, based 

 on such knowledge as I can obtain, that the probabilities of artesian 

 water on the Plains are rather unfavorable than otherwise. 



It will require a considerable amount of work in western New Mexico 

 to decide the matter finally. 



The well at Pecos City most probably belongs to the series newer 

 than that described under the Grand Prairie Region, and therefore 

 gives us no clue to the area north of it. 



The Trans-Pecos mountain district from the Guadaloupe Mountains 

 to the Rio Grande consists of numerous mountain ranges and detached 

 peaks which rise from comparatively level plains. These plains are 

 composed of loose material which has been derived from the erosion of 

 the mountains and sometimes has a thickness of over a thousand feet, 

 as is proved by the wells along the Texas Pacific and Southern Pacific 

 railways. The geologic formations of the mountains themselves con- 

 sist of granites, sandstones, schists, and quartzites and Silurian, Car- 

 boniferous, and Cretaceous limestones. The whole area is faulted, 



