58 ANNALS NEW YORK ACADEMY OF SCIENCES 



is not differentiated sharply from the underlying Red Beds. There is 

 often a transition from Eed Beds into gypsum. The change from the 

 gypsum to the lower members of the Morrison is abrupt, and the gypsum 

 often decreases in thickness where the Morrison is thick, and the reverse. 

 "It is possible, therefore, that the gypsum beds were exposed and slightly 

 eroded previous to the deposition of the shales" (Lee, 1901, 7). 



The following sections of the Morrison in this area are given by Lee 

 (1901, 7) : 



Section near Mouth of Plum Canyon 



Feet Inches 

 Dakota (Purgatoire). Two massive sandstone layers separated by 

 a soft sliale of varying thickness ; leaf 

 impressions near the top of the upper 



division 140 



Morrison, Greenwich clay shale, soft and fine grained 11 



Dull red clay shale, soft and fine grained 12 



Brown to yellow shale 10 



Argillaceous limestone ; numerous fine dark lamin^^e 6 



Buff-colored shale 18 



Argillaceous limestone ; numerous fine dark lamina? 6 



Variegated joint clay IS 



Argillaceous limestone, fine grained and hard, with con- 

 torted laminae 2 



Variegated shales ; ^ery soft and easily eroded 30 



Red Beds, Dark shales containing irregular masses of gypsum .... 15 



Gypsum containing streaks of clay 18 



Variegated shale containing nodular-like masses of gyp- 

 sum which vary in size from grains to masses a foot 

 or more in diameter. About one third of the mass is 



gypsum 8 



Gypsum in well-defined layers. Often separated by 



layers of clay 25 



Massive gypsum 5 



Red gypsif erous shales, soft and regularly bedded .. 30 to 40 

 Red calcareous sandstone, oolitic, cross-bedded. Indi- 

 vidual layers variable in thickness and character. 

 Near the top it becomes shaly and passes gradually 



into the gypsif erous shales above 60 



Red sandstone, massive, cross-bedded 175 to 200 



Red arenaceous shale 6 



Red sandstone 1 



Fine red shale 4 



Even-bedded red sandstone 9 



Red arenaceous shale 2 



Red sandstone, cross-bedded ; the individual layers thin 



out laterally 40 



Poorly cemented red sandstone alternating with layers 

 of shale 15 



