•563 C. SCHUCHERT PALEOGEOGRAPHY OF NORTH AMERICA 



plicatus, Chonetes granulifer, Hustedia mormoni, Dielasma oovidens, 

 Chcenomya leavemvorthensis, etcetera. 



To the writer, the Hermosa appears to be best correlated with the Upper 

 Missourian. Girty, however, correlates the Weber and the Lower Maroon 

 'of northwestern Colorado with the Hermosa. The Weber conglomerate 

 and sandstone represent, according to Hague, 188 "one of the most persist- 

 ent and well defined horizons over wide areas of the Cordillera, stretching 

 westward all the way from the Front Eange in Colorado to the Eureka 

 mountains." In the Eureka district the ^thickness is estimated at about 

 2,000 feet" (8,000 in the Oquirrh mountains). No fossils occur here. 

 In Nevada, above the Weber, follow the "Upper Coal Measures" lime- 

 stones, attaining a depth of nearly 2,000 feet. The fauna is essentially 

 "the same as that of the Missourian of the Mississippi valley. In Nevada 

 ihe series is terminated by limestones nearly 2,000 feet thick, bearing the 

 same fauna, and with a few lignite seams up to 18 inches in thickness. 



Upon the Hermosa, in southwestern Colorado, is laid down conform- 

 ably the Eico formation of sandstones and conglomerates, with interca- 

 lated shales and thin fossiliferous limestones. The thickness is about 300 

 feet. Girty 189 reports some of the fossils to be : Productus cora, Com- 

 posiia subtilita, Limipecten occidentalism Myalina Wyoming ensis, Pseudo-- 

 monotis hawni, P. equistriata, P. Jcansasensis, Pleurophorus subcostatus, 

 Naticopsis monilifera, etcetera. These species indicate the Permo-Car- 

 boniferous beds of the Kansas section and they show the fauna to be that 

 of the Mississippian sea. Cross and Howe 190 state : 



"The Hermosa formation appears to occupy the same stratigraphic position 

 as the Aubrey of Utah and Arizona. Further investigations are necessary, 

 however, to explain certain faunal differences or dissimilarities noted by pale- 

 ontologists between the formations." 



The Aubrey fauna is clearly of the western or Pacific realm. 



Apparently the Eico equivalent also occurs in the Wahsatch moun- 

 tains, here consisting of argillaceous and calcareous shales, with muddy 

 marls 650 feet in thickness. The fauna includes Pseudomonotis hawni. 191 



Above the Eico and Hermosa, in southwestern Colorado, are the unf os- 

 siferous "Eed Beds" forming the Cutler deposits. According to Cross, 192 

 their thickness is not less than 2,000 feet. Above is an erosion interval 

 followed by the Dolores formation of Upper Triassic age. The Cutler 



188 Hague: Monograph 20, U. S. Geological Survey, 1892, pp. 91-92. 



189 Girty in Cross : Folio 130, U. S. Geological Survey, 1905. 



190 Cross and Howe : Bull. Geological Society of America, vol. 16, 1905. 



10 * King : TJ. S. Geological Survey of the 40th Parallel, vol. 1, 1878, pp. 164, 173, 245. 

 192 Cross : Folios 120, 130, 141, and 153, U. S. Geological Survey, 1907. 



