peale.] GEOLOGY JURASSIC STRATA IN ARIZONA. 127 



Thickness. 

 Ft. In. 



7. Yellow siliceous sandstone 2 



8. Soft green sandstones and argillaceous shales - 



9. Space covered where the section was made, but as seen from a distance 



lower down the river filled with beds similar to those of No. 8 . . . . 40 to 50 



Top. 

 Total thickness about 242 7 



Above layer No. 9 is a massive siliceous sandstone, which I have taken 

 as the base of the Dakota group, for reasons that will be given when I 

 describe the Dakota group at this locality. Below the section are piuk 

 sandstones, resting on the red sandstones, referred to the Triassic. 



The colors of these layers gives a unique and striking appearance to 

 the canon-walls. Farther south and west this variegated appearance 

 seems to be more marked. 



In the Painted Desert in Arizona, Newberry* gives the following sec- 

 tion of the beds : 



Variegated marls. 



Thickness. 

 Ft. In. 



1. Light orange marl - - • - 15 



2. Green and purple magnesian limestone, containing worm-like concretions 



of calcareous spar 5 



3. Pinkish-purple marl 22 



4. Brown shelly sandstone .--- 8 



5. Purple marl with silicified wood 16 



6. Purplish green cherty magnesian limestone, in several layers, alternat- 



ing with bands of marl 8 



7. Purple aud cream-colored marls 30 



8. Greenish magDesian limestone in thin layers, with bands of marl 12 



9. Yellow, red, and purple marls 40 



10. Greeu limestone, similar to No. 8 3 



11. Red, purple, pink, green, lilac, brown, and blue marls with silicified 



wood 350 



Marcouf refers these beds to the Trias, regarding them the equivalent 

 of the Marnes Irisees of France and of the Keuper of Germany. He 

 says, "The third division or upper group of the Trias is subdivided 

 again into two parts. The lower is formed of thick beds of whitish- 

 gray sandstone, often rose-colored and even red ; and the upper con- 

 sists of beds of sandy calcareous clay, of very brilliant colors, violet, 

 red, yellow, and white — in a word of variegated marls. This upper por- 

 tion presents a striking resemblance, as to the rocks, with the Marnes 

 Irisees of France, or the variegated marls of Europe." 



Above the section (No. 9) I made on the Gunnison is a bed of massive 

 sandstone succeeded by shaly aud marly beds, in the upper portion oi 

 which is a lignitic layer. 



Above the variegated marls of the section given above, Newberry $ 

 found a bed of lignite which he considered to be of Jurassic age. 

 Whether this is identical with the lignite in sections Nos. 12, 13, and 14, 

 I cannot positively determine, but I think it improbable, as the beds 

 below do not seem to be identical. If they are identical, I place the 

 lower limit of the Dakota group lower than he did. The reasons for 

 so doing will be stated hereafter. Newberry, in his sections of what 

 he considers the base of the Lower Cretaceous, also finds a lignitic bed, 

 which is probably the one I have included. 



Newberry§, in speaking of the lignite, says : " The sandstone shales 

 and limestones lying above also include many beds of lignite closely 



*Ives's Colorado Exploring Expedition, Geological Report, page 79. . 

 t Geology of North America, page 13. 



t Ives's Colorado Exploring Expedition, Geological Report, page 81. 

 § Ives's Colorado Exploring Expedition, Geological Report, page 83. 



