RESUME OF LITERATURE. 83 



The so-called San Luis district which Endlich surveyed in 1873 " included the 

 southern portion of the South Park region and. the northern portion of the Sangre de 

 Cristo region. As these outcrops are practically continuous, and as Endlich did not 

 divide his discussion geographically, it will be less confusing in abstracting his 

 report to pursue the same course. Therefore his account of the geology of that 

 portion of the South Park region included in the San Luis district will be discussed 

 in connection with the Sangre de Cristo region. The same is true of Stevenson's 

 account of the geology of the South Park and Sangre de Cristo ' regions, which, 

 as it is brief and more general in character, less readily yields to 'Consideration in 

 different sections. 



SANGRE DE CRISTO REGION. 



Endlich's report upon the geologj' of the San Luis district is one of the most 

 unsatisfactory with which I have had to deal. The omission in the majority of cases 

 of the thickness of the beds whose succession he describes greatly enhances the 

 uncertainties involved in a comparison of different sections, while his failure to indi- 

 cate upon the map many of the numbered stations with reference to which his obser 

 vations are located is deserving of criticism. The presentation of his matter is 

 obscure, so that with the defects already mentioned and other omissions and incon- 

 sistencies, it is a laborious task to effect a comprehension of what he has written. 

 While some of the horizons of the Leadville and Crested Butte sections can be rec- 

 ognized with reasonable certainty in those described b}' Endlich, there is evidence of 

 considerable change in constitution from their occurrence to the north and west. 

 There is also ground for suspicion that Endlich has in some cases misinterpi-eted the 

 mutual attitude of the beds and has possibly reversed their real succession. 



There being in the Sangre de Cristo region no detailed section of the Paleozoic 

 rocks similar to those of the several monographic works dealing with central Colo- 

 rado, 1 have had to employ the latter as a basis of comparison in this region also. 



The area included in the San Luis district is "bordered on the north by a 

 line running east to west 6 miles south of Pike's Peak, on the west by the one 

 hundred and seventh meridian, on the south by a line running east to west 12 miles 

 south of Saguache, and on the east by the eastern slope of the Front Range." 

 (Page 305.) Of the Carboniferous this area includes a strip along the Front Kange 

 (more correctly along the Colorado Range and the Wet Mountains) consisting chiefly 

 of the series mapped as Triassic; of a somewhat branching body of outcrop, the 

 northern portion of the Sangre de Cristo Range, the farthest extremity of which 

 in the Park Range all but connects with the Carboniferous area reaching south from 



aV. S. Geol. Geog. Surv. Terr., [Seventh] Ann. Rept., for 1873, 1874, pp. 306-351. 

 6 U. S. Geog. Geol. Surv. W. 100th Mer., Kept., vol. 3, 1875, pp. 307-601. 



