Little Colorado Valley, Arizona. 497 



by an erosional unconformity, and the probability of finding 

 this erosion surface in the lower Little Colorado led to an 

 examination of the position of the Moencopie with reference 

 to adjacent formations. About three miles below the recently 

 constructed suspension bridge the entire Moencopie section 

 was found displayed, rising above the Kaibab limestone and 

 capped by the Shinarump conglomerate. 



A section measured by Mr. K. C. Heald, combined with one 

 measured by the writer, shows the following arrangement : 



Section in wall of the Little Colorado Canyon, 5 ± miles below 

 Tanner's Crossing. 

 Strike K 15° W. Dip KE. Z 2° 



1. Shinarump conglomerate ; grey or yellow-grey with 

 patches of black, red and yellow ; bottom few inches 

 black sands ; consists of partially rounded pebbles 

 0-2 inches in diameter of white (90 per cent), yel- 

 low, red, and black quartz, reddish quartzite, chunks 

 of calcareous shale one inch and less in long diameter, 

 and petrified wood. Cement in part calcareous. 

 About equal amounts of coarse sandstone and of 

 conglomerate. Stratum cross-bedded and lenticular. 



2. Unconformity ; marked by sudden transition shale 

 to conglomerate, and by wavy, irregular contact 

 including pockets in shale filled with sandstone and 

 conglomerate. 



Moencopie formation : 



3. Shale, red ; bleached white at top ; compact, hard, 



of microscopic fineness ; weathers into rounded 



disks . ._ _ _ 3 feet 



4. Shale, red-brown, argillaceous _. 25 



5. Shale, red-brown, and thin sandstones ; abundant 

 plant impressions like grass or stems of reeds 

 arranged in masses 16 



6. Sandstone 3 



7. Shale _ 2 



8. Sandstone '_._ 2 



9. Shale, arenaceous ; tiny veins of gypsum __ 11 



10. Sandstone ._ 3 



11. Shale 8 



12. Sandstone, thin-bedded at top. Forms bench 6 



13. Shales, arenaceous, argillaceous and calcareous ; 

 banded red and grey-green 26 



14. Sandstone, thin-bedded, ripple-marked 1 



15. Shale 20 



16. Sandstone, red-brown, thin-bedded, cross-bedded, 

 marked by ripples, mud cracks, worm casts, and 

 plant impressions. Muscovite on bedding planes. _ 2 



