RESUME OF LITERATURE. 79 



and the Tenmile folio, as is well kuown, are the work of the same geologist. The 

 geologic section in the Leadville district ma}' be condensed as follows (p. 58 et seq.): 



Section in Leadville district. 



CARBOKIFEROUS. 



Feet. 



Upper Coal Measures: Base taken at the Robinson limestone. Consists of alternating calcare- 

 ous and siliceous beds, which at the base are like those of the Weber grits and at the top like 

 those of the Trias 



Weber grits: The typical rock a coarse -svhite sandstone, passing into conglomerate, with 



which are mingled quartzose shale and mica-schists 2, 500 



Weber shale: Extremely variable. A transition series of argillaceous and calcareous shale, 



alternating with quartzitic sandstone 150-300 



Blue limestone: Dolomitic, deep grayish-blue in color, often nearly black near the top, while 

 some of the lower beds are lighter. Upper strata marked by chert concretions containing 

 fossils 200 



SILURIAN.' 



Parting quartzite : White quartzite i 40-70 



White limestone: Light-colored, more or less siliceous dolomitic limestone 120-160 



CUMBRIAN. 



Lower quartzite: Below, thin-bedded, white, saccharoidal quartzites, conglomeritic at the 

 base. The upper 50 feet are shaly and calcareous, passing gradually into the siliceous 

 limestone of the Silurian 150-200 



ARCHEAX. 



Granite, gneisses, and schists. 



The section obtained from the Leadville monograph calls for but little comment, 

 as it differs from that given in the Tenmile folio, whose relation with the other 

 sections in central Colorado has already been discussed, chieiiy in its nomenclature. 

 From the different formations, and especially from those belonging to the 

 Carboniferous, more or less extensive faunas are cited. The faunal evidence, which 

 will be discussed more at length in the section devoted to paleontology, shows that 

 the Leadville limestone is of Lower Carboniferous age and that the rest of the beds 

 belong to the Upper Carboniferous. There is nothing to suggest the pi'esence of 

 Permian. 



The Paleozoic section throughout the South Park area seems to be in the main 

 uniform and similar to that of the Grand River area, and the section described in 

 the Leadville monograph is in a general wa}' representative of the entire region. 



Aside from the Leadville monograph but little of importance has been written 

 regarding the geology of this narrow strip of Paleozoic outcrop, and that little also 

 deals chieti}' with its northern portion. Peale described the geology and gave some 

 sections, for the most part of the Leadville region, and Endlich described the 

 geolog}' of the southern portion in a way which it is difficult to understand and 

 which does not inspire confidence as to his accuracy. 



