PURPOSE OF INVESTIGATION 



573 



the gap. Furthermore, assuming, as is often done, that the first great 

 uplift of the mountains occurred at the end of Cretaceous time, the 

 post-Cretaceous unconformity found in the Raton Mesa region should be 

 recognizable on the western slope and the post-Cretaceous formations 

 east of the mountains sliould have recognizable counterparts on tlie 

 western slope. 



Figure 1. — Map of Part of Xew Mea-ico, shoiring Location of Coal Fields 



The type of locality of the Mesaverde formation and the Lewis shale 

 is in southwest Colorado, in the northern part of the San Juan Basin, 

 where the Mesaverde is known to lie above shale that contains marine 

 fossils of Pierre age, but relatively little has heretofore been known of 

 the fossils contained in the Mesaverde, the Lewis, or the "Laramie" of 

 'this basin. In order, therefore, to correlate the formations east of the 

 mountains, where good collections of botli leaves and shells had been 



