MOOK, STUDY OF THE MORRISON FORMATION 



119 



200-400 feet produced by deposition predominating over erosion, means 

 a much greater time interval tiian the same thickness deposited under 

 conditions of continuous deposition. 



Sudden lithologic changes from one bed to another are very common 

 in the Morrison. Fine clay-shales will be overlain by coarse cross-bedded 

 sandstones and the reverse. These abrupt successions do not necessarily 

 mean breaks or lost time intervals, but rather sudden changes of condi- 

 tions in definite areas. 



Fig. 84. — Red hematitic grit, from the top of the Morrison formation at Garden Park, 

 near Canon City, Colorado. 



The light gi-ains are quartz ; the light patches are holes in the slide r the dark areas arc 

 clay stained with hematite. About 28 X. 



Petrogeaphic Ci-iaracters of the Morrison Formation 



A number of distinct types of sediments occur in the Morrison forma- 

 tion. Broadly speaking, these are: (1) fine red or brown sandstones; 

 (2) clays; (3) calcareous sandstones; (4) limestones; (5) coarse white 

 sandstones. These grade into each other in a rather complex manner, 



