18 MESOZOIC FLORAS OF UNITED STATES. 



TEE MOENCOPIE FORMATION. 



These occupy tli.e lowest portion of the group, having a maximum 

 observed thickness of between 600 and 700 feet. The}^ present several 

 distinct phases, but the greatest part of them consists of dark-reddish 

 brown, soft, laminated, argillaceous shales, nearly destitute of silica, 

 highly charged with salt" and gypsum, tending on exposure to assume 

 the character of nearly homogeneous marls and to form low ridges, but- 

 tresses, and even isolated knolls or buttes, at the bases of cliffs and in 

 eroded valleys. The gypsum often forms thin sheets which appear as 

 fine white lines and which do not follow the planes of stratification, but 

 cross the beds irregularly and also cross one another, giving the exposures 

 a peculiar striped appearance. 



Between these beds of shale there occur, usually at more than one 

 horizon, brown sandstones. These are more or less argillaceous and their 



geological structure of the Painted Desert prevail over a wide belt of countrj' bordering the Little Colorado 

 on the east, and extending at least as far northward as our camp 73." This camp appears from the very 

 imperfect map accompanying the report to have been about on the latitude of Tanners Crossing, but far to 

 the westward. On this map the Painted Desert is represented as occupying all that region lying along the 

 southwestern base of the painted cliffs from the line of their route through the gap at Blue Peaks and Pottery - 

 HiU northwestward to an indefinite distance. On the latest Land Office maps, however, it seems to be restricted 

 to that portion of the desert lying north of the Moencopie Wash and along the base of Echo Cliffs. There 

 seems to be no good reason for thus restricting it. 



"An artesian well was bored at Adamana, on the Santa Fe Pacific Railroad, 8 miles north of the Petrified 

 Forest and in the vaUey of the Rio Puerco. At a depth of 305 feet water was struck which had sufficient 

 force to rise 19 feet above the surface and discharge 25 gallons per minute. The water was very salt, reported 

 at 3 per cent chloride of sodium, so as to be wholly unfit for any use. Mr. James Swainson, in charge of the 

 work, which was done by the American Well Works of Aurora, 111., was good enough to send me the log, which 

 is as follows: 



Record of well boring at Adamana, A>i:. 



Feet. 



Surface sand and adobe 55 



Sandstone 3 



Cement gravel -.,..- - 1 



Sandstone 29 



(Water at 88 feet only slightly salt.) 



Sandstone 20 



Brown shale. '. . - 43 



Red shale 49 



Hard brown and blue shale 5 



Red shale - 70 



Sandstone - - 10 



Hard brown shale 20 



(Intensely salt water. ) 



Total - 305 



The lower 200 feet of this section clearly belong to the Moencopie beds. 



