108 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



Teton County is very near the western boundary of Cretaceous 

 deposition in Montana. It reaches the border of Alberta and the 

 coal-bearing area is between meridians 112° 30' and 113°. Steb- 

 inger's^^ report on this area and his general discussion of the ]^Ion- 

 tana Cretaceous have done much to solve serious problems in cor- 

 relation. The succession in the Teton coal field is St. Mary River 

 formation, correlated with the Laramie ; Horsethief sandstone, 225 

 to 275 feet, which Stebinger has shown to be same as the Lennep 

 sandstone and the Fox Hills ; Bearpaw shale, with characteristic 

 features of the formation, 490 feet; Two-Medicine formation, 1,950 

 feet, gray to greenish gray and whitish clay Shales, with some sand- 

 stones, which are important in the basal 250 feet ; Judith River 

 leaves, mollusks and bones of reptiles are present ; it is apparently 

 continental in origin, there being evidence of only one marine inva- 

 sion, and that is at about 200 feet from the base. The formation 

 includes Judith River, Claggett and the upper or coal-bearing por- 

 tion of the Eagle. The marine deposit near the base contains the 

 Claggett-Fox Hills fauna, indicating deposition in a retreating sea. 

 Within the disturbed region on the western side of the county, one 

 finds it difficult to distinguish this formation from the St. Mary ; 

 the conditions during deposition must have been very similar in 

 both. Virgelle sandstone, 220 feet, the basal sandstone of the 

 Eagle, is gray to buff, coarse, cross-bedded sandstone, becoming 

 slabby to shaly in the lower half. 



Two-Medicine and Virgelle, traced northward into xA.lberta, prove 

 to be the Belly River formation, described by G. M. Dawson. The 

 Two-Medicine is characterized by extreme irregularity of the beds ; 

 sections only a few hundred feet apart are wholly dissimilar. Fos- 

 sil wood is distributed throughout the formation, knots and entire 

 sections of compressed trunks of trees are of common occurrence. 

 The continental deposits, except the Fox Hills, become thinner to- 

 w^ard the east, so that in the Black Hills of northeastern Wyoming 

 the Pierre is represented only by marine shales. 



No coal aside from petty lenses was seen in the Virgelle ; the 

 Two-Medicine has three coal zones, one at the base, another at 250 



'>^E. Stebinger, Bull. 621-K, 1916, pp. 126, 127, 131, 140, 144; Prof. Paper 

 go-G, 1914, pp. 61-68. 



