64 EXPLOBING EXPEDITION FEOM SANTA FE 



of lignite, which have attracted the attention of all the exploring parties who have 

 entered this region, and have been mentioned in their notes as beds of bituminous coal. 

 The higher table-lands between the San Juan and Little Colorado have an altitude of 

 about 8,000 feet, and are composed of the upper members of the Cretaceous forma- 

 tion, corresponding in all respects with the Mesa Verde north of the San Juan, with 

 which they were at one time undoubtedly continuous; the immense void which now 

 separates them having been removed by erosion. This high table-land the "white 

 mesa" of my former report seems to reach westwardly to and beyond the Great 

 Colorado, but its western boundaries have not been accurately determined. Where 

 this mesa is cut by the Colorado that stream is supposed to have an elevation of less than 

 2,000 feet above the level of the sea. The awfully grand precipices over a mile in 

 height which overhang it, I have described in my former report on the geology of 

 this region. 



On the eastern margin of the Colorado plateau, especially in that part of it which 

 borders Cafion Largo, and forms the western base of the Nacimiento Mountain, a 

 series of variegated gypsiferous strata overlie the Upper Cretaceous beds of the Mesa 

 Verde, and occupy a considerable superficial area. These strata seem to be conform- 

 able to the Cretaceous rocks below, and may form the summit of this sei'ies, or, as I 

 have suggested in another chapter, they may be Tertiary. If so, they belong to an 

 older division of the Tertiary series than the chalky beds of Santa Fe and the plains, 

 and represent a group not elsewhere seen in any part of the Colorado plateau. What- 

 ever their age, these strata form the geological summit of the plateau series of sediments. 



