STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 81 



The Fox Hills, Lennep Sandstone, Horsefhief Sandstone. 



In this study the transition beds from the marine Pierre to the 

 fresh-water Laramie are taken to be the Fox Hills. At very many 

 localities, where the higher members of the Cretaceous have escaped 

 erosion, this transition formation is a shore or offshore deposit of 

 more or less coarse materials, with fossils, mostly marine but ac- 

 companied at times by brackish-water forms. Within some basins, 

 coal seams of great economic importance are present, while in others, 

 coal is wanting or in such small quantity as to possess only geological 

 interest. 



Reports on the San Juan Basin to which the writer has access, 

 give no details sufficing to determine whether or not the Fox Hills 

 is present in any considerable part of the Basin ; but a section by 

 J. H. Gardner, cited and discussed by Lee,-*' shows that it exists in 

 the northern part. The Pictured Cliffs sandstone, 394 feet thick, 

 mostly gray sandstone, contains marine fossils to the top. It un- 

 derlies 79 feet of brackish to fresh-water beds, in which coal seams, 

 4 and 12 feet thick were seen at 4 and 57 feet from the base. Lee 

 includes these in the " Laramie," as there appears to be uncertainty 

 respecting the relations of some parts of the column. No coal has 

 been reported from the Pictured Cliffs sandstone. 



The existence of Fox Hills is equally uncertain in the Uinta 

 Basin of western Colorado. Fox Hills conditions recurred at vari- 

 ous horizons in the Pierre of this basin, as they did in central New 

 Mexico, so that the earlier observers recognized both Fox Hills and 

 Laramie in the Pierre beds. But there is no room for doubt that 

 the formation exists in the southeast prong of the Colorado portion 

 of the Green River Basin ; for there Gale*^ found the basal sand- 

 stone of the " Laramie," resting on the Pierre, with a marine fauna. 

 The thick coal bed at Craig apparently belongs in the Fox Hills. 

 About 50 feet of this formation has escaped erosion in North Park, 

 Colorado, where it rests on the great mass of Pierre shale. There 

 Beekly obtained marine shells and the fucoid Halynienites major 

 from this sandstone ; but no coal is present.*'' 



4" W. T. Lee, Bull. Geol. Soc. Amer., Vol. 23, 1912, pp. 587-591. 



48 H. S. Gale, Bull. 341, pp. 287, 295. 



49 A. L. Beekly, Bull. 596, 1915, p. 46. 



