II E. Gregory — Shinarump Conglomerate. 429 



a correlation " is a procedure requiring clear justification by 

 facts not to be found in Ward's paper." Unfortunately detailed 

 measured sections are not published by Ward nor to be found 

 in his field notebooks on file in the Survey office. A knowledge 

 of the exact position, extent and character of beds other than 

 the conglomerate in his " Lithodendron member" cannot there- 

 fore be obtained. That the Shinarump frequently becomes a 

 sandstone traversed by lines of pebbles, and that small lenses 

 of clay shale occur in the midst of the conglomerate at one or 

 two localities and even immediately at the lower contact, are 

 facts of field observation. This shale, however, wherever 

 observed, is unlike that forming the beds below the conglom- 

 erate, but resembles in essential particulars the beds occurring 

 anywhere from one foot to 500 feet above the Shinarump con- 

 glomerate and even in the midst of the formation containing 

 limestone conglomerate (Dolores of Cross ; Leroux, in part, of 

 Ward). In any case the line used by Ward to divide his " Lith- 

 odendron member" from his "Leroux beds" is arbitrarily 

 drawn, and it seems better to limit the Shinarump conglomer- 

 ate to the siliceous stratum or strata immediately above the 

 chocolate shales and sandstones (Moencopie). 



It is to be remembered, however, that the exact localities 

 studied by Ward have not been examined in detail by other 

 observers. The following statement of Darton, however, bears 

 on this point : 



" I found this conglomerate at the base of the ' Lithodendron 

 formation,' well exposed five miles northeast of Win slow, associ- 

 ated with two beds of sandstone and containing a large amount 

 of petrified wood. It was traced along the north side of the 

 Little Colorado Valley to Holbrook and thence up the Rio Puerco 

 to a point considerably beyond Adamana. I did not notice that 

 the conglomerate occurs at various horizons, as stated by Ward, 

 h\\\ made no careful observations in that connection." — (Bulletin 

 435, U. S. Geol. Surv., p. 40.) 



The Shinarump conglomerate, wherever observed, is wholly 

 siliceous and gray to white, rarely brown, in tone. It varies in 

 texture from conglomerate with pebbles two inches or so in 

 diameter to coarse sandstone ; rarely to fine sandstone. The 

 coarser phases are well exposed at Fort Defiance, where pebbles 

 of red, black, and yellow quartz (rarely chert) are mingled with 

 fragments of silicified wood. All the larger pebbles (1/4 7 ' to 

 1" ; occasionally 2") except those of wood are well rounded, 

 and the smaller wood particles exhibit the same character. 

 The matrix is identical in composition with the embedded 

 pebbles and cobbles. In places the rock consists of a solid 

 mass of pebbles ; elsewhere a large pebble is set in a cubic 



