68 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



allied to Laramie forms. The authors suggest that, at least in part, 

 the Patoot may be a transition formation ; no unconformity was ob- 

 served between Cretaceous and Tertiary ; all conditions indicate that 

 sedimentation was continuous. Near Patoot, at 1,170 feet above the 

 base of this division, there are occasional bands, ferruginous, con- 

 taining ferns, conifers, and dicotyledons, with erect stumps and 

 abundance of silicified wood. 



North America. 



Cretaceous deposits are present on the Atlantic and the northern 

 Gulf coasts of the United States, but they contain no coal and the 

 occurrences of lignite have interest only for the paleobotanist. The 

 important area is in the west-central region, where the deposits 

 originally extended from the 95th meridian westward for not far 

 from 1,000 niiles, and from Lat. 25° in Mexico northward for not 

 less than 2,100 miles, in all not less than 2,000,000 square miles. 

 These figures are merely approximations and the area of greatest 

 extent may have been considerably larger. The continuity of these 

 deposits was destroyed by post-Cretaceous erosion, following the 

 Rocky-Mountain revolution. 



Belief that Cretaceous deposits were practically continuous 

 throughout this vast area is of comparatively recent data. The 

 prevalent conception until within little more than 20 years, was that 

 the Rocky Mountains had existed during Cretaceous time. There 

 seems to be little room for doubting the general accuracy of conclu- 

 sions that those mountains mark lines of successive foldings but proof 

 of their existence as elevated areas is wanting. Willis-- thought that 

 the earliest Cretaceous deposits of his district were laid down on a 

 surface of Carboniferous and Algonkian rocks, which was a plane, 

 primarily a peneplain and afterwards a surface of marine planation. 

 The first period of compression may not have begun until after 

 close of the Cretaceous. Incidental reference to the conditions 

 indicates similar conception on the part of some later observers ; 

 but the first clear analysis of the evidence, known to the writer, is 

 that by Lee.-^ who has discussed the phenomena observed by him- 



22 B. Willis, " Stratigraphy and Structure. Lewis and Livingston Ranges, 

 Montana," Bull. Geol. Soc. Amer., Vol. 13, 1902, pp. 338, 339. 



-3 W. T. Lee, U. S. Geol. Survey, Prof. Paper, 95-C, 191 5, pp. 56-58. 



