Geology and Mineralogy. 7 



Lone Cone the sandstones of t'.e Dakota group or No. 1 Crett 

 ceous are nearly horizontal, forming a plateau which on approacl 

 ing (lie mountains has a capping of Cretaceous shales. 



Beyond the bend, the San Miguel flows in a monoclinal valle 

 in which the canon walls are of the same description as in th 

 upper part of its course. As the mouth is approached the Re 

 Beds appear. Between this portion of the course of the San liigw 

 and the almost paralled course of the Dolores, which is in a sim 



valleys parallel to each other. They are all occupied l>v bVanehe 

 of the Dolores. Lower Cretaceous; Jurassic and Triage strat; 



he fully 'considered in the report oiMhe district. The Dolore 

 river comes from a high plateau in a zigzag course, flowing some 

 times with the strike and sometimes with the dip of the strata 



to northwest again to its juixt 

 cafiou the greater part of its course. 



In the region of country north of Grand River, the geological 

 formations < \t, n 1 mint rruph dlv from the Red Beds exposed ,„, 

 Grand River to the White Tertiary cliffs forming the su mm: of 

 of the "Roan Mountains" or Book Cliffs. The <, rand is generally 

 in a canon in the Red Beds. On the north side the X o. I Cre- 

 taceous sandstones form a hogback sloping toward the cliffs. 

 U.-rwcen th ct-est of thi> 1 _' ck id th , f>, there is a broad 

 valley formed by the erosion of the soft Cretaceous shahs which 

 extend to the base of the cliffs and in some places form their 



The cliffs are composed mainly of Cretaceous beds, rising one 

 above anotl. "elevation of about s.ooO feet is 



reached. The summit is the edge of a plateau, sloping to N.VK. 

 This plateau is cut by the drainage flowing into the White River 

 from the south. These streams' rarely cut through the Tertiary 



Coal of poor quality is found in the sandstones of the Dakota 

 group and also in the sandstones above the middle Cretaceous 

 beds. Wherever noticed it was in thin seams and of little 



The White* River division was directed by G. B. Chittenden as 

 topographer, accompained bv F. M. Endlich as geologist. 



The district assigned to this party as their field for e\ 

 during the season" of 1876, commenced from the eastward at 

 longitude 107° 30', joining on to the work previously done and 



boundary was X latitude 39° 30', while the White River formed 



In order to complete the work to im- 

 possible advantage in the shortest time that could be 



- .; -, ,.- - .■■ , -.\ ■ . - \. 



and in two trips from there complete the work. About 3,800 

 square miles comprised the area surveyed. 



