THE MORRISON FORMA TION OF COLORADO 



547 



-i-i-f-T-i- 







Dakota sandstone. 



25 feet brick-red arenaceous shale, containing bands of hard, fine-grained sandstone. 

 3 to 5 feet reddish limestone having a conchoidal fracture and very brittle. 

 30 feet soft dark clay shale. 



11 feet light brown clay shale. 



6 inches argillaceous limestone. 



7 feet brown shale. 



1 foot concretionary limestone. 



7 feet variegated clay shale; joint structure. 



3 feet fine yellow paper shale. 



6 inches argillaceous limestone, finely laminated. 

 18 inches fine shale. 



2 foot white limestone. 



15 feet variegated clay shale. 



8 inches argillaceous limestone, finely laminated. 



4 feet yellow shale. 



1 foot sandstone containing agate either in concretionary masses half an inch or more in diameter or 



[disseminated generally throughout the mass. 

 8 feet sandstone, easily crumbling; made up of thin layers. 



2 feet massive sandstone, poorly indurated. 

 2 feet fine paper-shale. 



7 feet massive sandstone, poorly indurated. 



12 to 20 feet gypsum interstratified with layers of clay. 



red sandstone (Red Beds). 



P"ig. 3. — Section 2, in Red Rocks Canyon. 



sandstone occurs in places but there seems to be no particular 

 horizon at which this is likely to be found. In Red Rocks 

 Canyon it occurs at the base ; in Plum Canyon, none is found ; 

 in a side gulch east of Plum Canyon a brecciated layer occurs 

 near the top containing angular fragments one quarter inch in 

 diameter; in Chaquaqua Canyon, four miles from the mouth of 

 Plum Creek, a coarse cross-bedded sandstone layer 15 feet in 

 thickness occurs about 50 feet from the top; just across the 

 canyon from this point, perhaps two miles distant, and at the same 

 horizon, about 30 feet of limestone is found in place of the sand- 

 stone. In many places the sandstones are friable and composed 

 of nearly pure quartz. The sand is used as a flux in assaying 

 where pure silica is required. The occurrence of the limestones, 

 most of which are more or less argillaceous, is as eratic as that 



