38 COLORADO FORMATION AND ITS INVERTEBRATE FAUNA, [bull.106. 



expressed concerning the correlation of these beds were repeated in 

 subsequent publications. 1 



Messrs. King and Emmons 2 assigned the Cretaceous strata at Coal- 

 ville to the Colorado, Fox Hills, and Laramie formations, and so mapped 

 them in the atlas accompanying their report. The principal (lower) 

 coal bed is included in the Colorado formation and upper one in the 

 Fox Hills, the line between these two formations being drawn in the 

 second ridge above the lower coal bed. It should be remembered that 

 the Colorado formation was then made to include the Fort Pierre 

 division. 



Dr. C. A. White studied the section in 1877, and after discussing the 

 fossils collected in it he states 3 that it is impracticable to refer the 

 strata to any one or more of the established Cretaceous groups with 

 certainty, but he thinks there is no reason to doubt that the greater 

 part of the series at least is referable to the Fox Hills. 



The entire series at Coalville is characterized by heavy beds of light- 

 gray and yellowish sandstones alternating with clay shales and other 

 soft strata. Consequently, as the beds have a considerable dip, the 

 sandstones form prominent ridges, and these were numbered in Prof. 

 Meek's section, beginning with the first one above the lower coal bed. 

 There are several faults in the area, one series nearly parallel with the 

 strike and another almost at right angles with it, but they do not com- 

 plicate the section greatly since the prominent sandstones are all fossil 

 iferous and therefore easily identified. The following somewhat gener- 

 alized description will serve to show the range of the fossils and the 

 reasons for the correlation that follows: 



CreiaccouH section at Ccalville, Vtali. 



Feet, 



1. -Interstratmed sandstones and shales, with heavy bed of coal at the top. 



The underlying beds are cut off by a fault. Several of the sandstone 



layers are very fossiliferous. (See list below.) Estimated thickness. 500-600 



2. Gray sandstones 30 feet thick forming roof of coal bed, overlain by 



dark clay shales with numerous specimens of Inoceramus laViatus 795 



3. Cray and yellowish hard sandstone forming the first and second ridges, 



with numerous fossils, many of which are identical with species of the 

 Pngnellus sandstone in Huerfano park, Colorado. (See list below). .. 100 



4. Clays, with thin beds of sandstone 1G5 



5. Massive conglomerate 60 



6. Mostly covered, but showing soft clay shales and thin beds of coarse 



sandstone where exposed 8 15 



7. Clay shales interstratified with thin bands of sandstone and two or three 



thin seams of coal (including the Carleton bed) of noeconomic import- 

 ance, near the base. Fossils abundant, including marine, brackish 

 and fresh water invertebrates, and plants. (See list below) 110 



» U. S. Geol. Sur. Terr. Vol. ix, p. xxx ; TJ. S. Geol. Expl. Fortieth Parallel, Vol. iv, p. 1 1 , footnote. 

 2 U. S. Geol. Expl. Fortieth Parallel, Vol. I, pp. 31G-31U, 327-330, and Vol. II. pp. 330-337. 

 a Ami. Rept. U. S. Geol. Sur. Terr, for 1877, p. 239. 



