120 GEOLOGY. 



rather flat surface by agencies capable of distributing sediments with 

 some degree of equality. These beds are frequently unconformable 

 on older formations, including the marine Jurassic. In the Black Hills 

 region, the Morrison beds are overlain by other non-marine beds of 

 Early Cretaceous or Comanchean age, 1 some of which are coal-bearing. 



Farther north, in Montana, Alberta, and Assiniboia, there is a 

 series of beds (the Kootenay and Cascade formations, etc.) 2 similar 

 in character to those just described, but not known to be connected 

 with them. In the area where first described, the Kootenay formation 

 occupies a narrow belt about 140 miles long and 40 miles wide. Simi- 

 lar beds have been discovered farther north. The Kootenay beds 

 are mainly clastic, and are very inconstant in character, both vertically 

 and horizontally. They contain some coal, and the fossils are mostly 

 of plants of Early Cretaceous types. 3 The Kootenay formation is said 

 to attain a maximum thickness of 7000 feet. 



The non-marine Kootenay of these northerly localities rests uncon- 

 formably on marine Lower Cretaceous beds, the fossils 4 of which 

 are so like those of the Early Cretaceous of the Queen Charlotte 

 Islands, as to lead to the belief that the beds in the two regions were 

 contemporaneous and laterally continuous, and therefore that the 

 sea of the northern interior entered from the west. The connection may 

 have been in some such position as that of the late Jurassic (Fig. 348). 



To the Morrison and Kootenay formations a lacustrine origin has 

 usually been assigned. There is perhaps no adequate ground for 

 questioning this conclusion for some parts of the formations, but the 

 character of some of the beds and the nature and distribution of their 

 fossils suggest a fluviatile origin for parts, and perhaps for large parts, 

 of the series. The variations in the character of the beds within short 

 distances is most easily explained as the work of meandering rivers. 



1 Darton and Smith, Edgemont, S. D.-Wyo. folio, and Darton, New Castle, Wyo.- 

 S.D. folio, U. S. Geol. Surv. 



2 See Cascade formation, Fort Benton, Mont, folio, U. S. Geol. Surv. 



3 G. M. Dawson, Am. Jour. Sci., Vol. 38, pp. 120-127. A brief general description 

 of the formation. A fuller statement by the same author is found in Report Geol. 

 Surv. of Canada, 1885. For the corresponding formations in the United States, see: 

 Newberry, Am. Jour. Sci., Vol. XLI, pp. 191-201; Weed, Bull Geol. Soc. Am. Vol 

 III, 1892, pp. 301-23; Weed and Pirsson, 18th Ann. Rept. U. S. Geol. Surv. 

 and Bull. 139, U. S. Geol. Surv.; and Wood, Am. Jour. Sci., Vol. 44, 1892, p. 401. 



4 Whiteaves, Contributions to Canadian Paleontology, Vol. I, Pt. II 



