434: H. E. Gregory — Shinarump Conglomerate. 



Paleontological evidence indicating Upper Triassic age of 

 the strata overlying the Shinarump conglomerate rests on 

 fossils collected by Ward and Brown near Tanners Crossings,* 

 described by Lucas ; f by Gane at Clay Hill on the Lower San 

 Juan, $ fossils described by Lucas ; § by Walcott in the Kanab 

 valley, fossils described by Eastman and Shimer ; | by Wood- 

 ruff in the San Juan Oil Field,!" fossils identified by Stanton 

 and Gilmore. Among other collections from these beds, and 

 all exhibiting Triassic affinities, are bones and teeth found at 

 several localities on the Navajo reservation during the field 

 seasons 1909-1911. Fossils found at Oljato in the Shinarump 

 conglomerate itself are too fragmentary for identification. 



The list of fossils from the localities mentioned includes the 

 following : 



From Tanners Crossing, Arizona — Heterodontosuchus ganei 

 Lucas, Episcoposaurus Cope, Metoposaurus fraasi Lucas, 

 Palceoctonus Cope, Placerias hestemus Lucas ; from Clay 

 Hill, Utah — Heterodontosuchus ganei Lucas; from Kanab, 

 Utah and Arizona — Vertebrates, Pholidophorus, several 

 Zepidotus-]ike forms : Invertebrates, ammonitoid fragment, 

 Candona (1) Rogersii Jones, Estheria ovata Lea ; from San 

 Juan Oil Field, Utah — TJnio oristonensis Meek (?), Viviparus 

 (?) sp., fragments of reptilian bone. 



(2) The beds below the Shinarump conglomerate, while 

 varying greatly in massiveness and relative proportions of shale 

 and sandstone, have been recognized by all observers as equiva- 

 lents throughout the extent of the Plateau Province. At nearly 

 all localities where I have observed these beds they are shales 

 and shaly sandstones of characteristic color, composition, and 

 type of stratification, and the sections at Shinarump Cliffs, 

 Utah, Little Colorado Valley, Arizona, G-ypsum Creek, Utah, 

 and Bonito Valley, Arizona, might be interchanged without 

 detection so far as general features are concerned ; but at other 

 localities, especially Canyon de Chelly, the upper shales at 

 least are replaced by massive, cross-bedded sandstone.** 

 This change of character is fortunately not confusing so far 

 as stratigraphic position is concerned, for the top of the 



*U. S. Geol. Surv., Monograph XLVIII, p. 15. 



f Science, vol. xiv, p. 376, 1901; U. S. Nat. Mus., Proc, vol. xxvii, 

 pp. 193-95, 1904. 



X Cross, Jour. Geol., vol. xvi, p. 116, 1908. 



§ This Journal, vol. vi, pp. 399-400, 1898. 



1 Cross, Jour. Geol., xvi, p. 107, 1908. 



If Geology of the San Juan Oil Field, U. S. Geol. Surv., Bulletin No. 471, 

 pt. ii, p. 85, 1910. 



**Dutton: Zuni Plateau, p. 136-7; and Barton, Bulletin 435, U. S. Geol. 

 Surv., plate IV, are in error in assuming that the massive walls and com- 

 manding towers of Canyon de Chelly and Canyon del Muerto are cut in 

 Wingate (Triassic ? or Jurassic) sandstone. 



