MOOK, STUDY OF THE MORRISON FORMATION 65 



iact really represents the whole time indicated by the unconformity be- 

 tween the Eed Beds and the Exeter sandstone and the time required to 

 form the Exeter sandstone, besides the possible period between the deposi- 

 tion of the Exeter and that of the shales" (1902, 5). 



The Morrison formation is exposed in the canyon of the Canadian 

 Eiver. This river flows in a narrow gorge for fifty miles or so, then in a 

 broad valley bordered by high escarpments. The thickness of the forma- 

 tion is approximately 300 feet. The beds are composed mainly of varie- 

 gated clay-shales and friable sandstones. Limestones also occur in lim- 

 ited extent. In some localities the limestone layers are all near the top, 

 and at others they are differently distributed. In no two sections do the 

 limestones occur at the same horizon. The sandstones comprise a con- 

 siderable part of the formation, perhaps one-third. The separate beds 

 are in some cases firm and in others very friable. They grade from sands 

 of pure silica to nearly pure clay. A slightly cross-bedded sandstone of 

 considerable persistence may be seen in places near the middle of the 

 formation. The shales contain red, brown and green members. 



The contact with the overlying Purgatoire is abrupt, but without defi- 

 nite evidence of disconformity. A coarse, massive, pink sandstone occurs 

 at the base. The contact with the underlying beds is sharp, but without 

 distinct disconformity (Lee, 1902, 5). 



The following section was measured by Lee, north of Bell Ranch : 



Section at the Escarpment north of Bell Ranch 



Feet 



Dakota (Purgatoire). Sandstone, coarse, massive and quartzitic 250 



Shales (Morrison). Variegated sliale containing numerous thin bands of 



limestone and sandstone 50 



Argillaceous fissile .sandstone ' 10 



Coarse sandstone 13 



Rluish-green shale with a few bands of sandstone and im- 

 pure limestone 45 



Coarse massive sandstone 15 



Variegated clay shale 12 



White sandy shale 5 



Coarse white sandstone, cross-bedded in places 13 



Colored sandy shale. 15 



Argillaceous sandstone 6 



Coarse sandstone containing lime concretions in places 15 



Variegated shale containing thin layers of sandstone 36 



Red and green shales 12 



Poorly exposed. Shale seen at intervals 65 



Rusty brown to red sandstone with bands of red clay . . 10 to 50 

 ? Sandstone. Massive pink to white sandstone. Forms a persistent clifC. 50 to 100 

 Red Beds. Friable sandstones and shales in thin layers, red to deep pur- 

 ple in color 



