430 H. E. Gregory — Shinarump Conglomerate. * 



foot of sandstone. Frequently a line of pebbles is seen trav- 

 ersing the sandstone for a distance of several feet. In places 

 the sandstone is loosely cemented ; generally it is firm, and 

 occasionally becomes a glistening, hard quartzite conglomerate. 

 At Oak Springs, Arizona, the constituents are pebbles of black, 

 white and red quartz and chalcedony, all well rounded and 

 attaining a size of one-half inch to two inches. At Oljato 

 subangular clay pellets two inches or less in diameter are em- 

 bedded with white, dark red, greenish, and black quartz and 

 chalcedony. Fragments of wood several inches to several feet 

 in length are present at every locality visited. Frequently the 

 wood is present as logs ; rarely it occurs as charcoal. At Oljato 

 some chips are impregnated with copper ; and at Leeds, Dutton 

 reports that horn silver occurs in the wood. The universal 

 presence of fossil wood constitutes the unique feature of the 

 Shinarump conglomerate, and attracted the interest of Indians 

 long before the coming of the white man. To the Piutes, the 

 broken fossil logs are weapons of Shinarav, the Wolf god, a 

 sort of Hercules, and Shinarav Mukwankunt, as pointed out 

 by Powell, is the original native name of the Shinarump cliffs. 

 Navajos and Hopis explain the presence of wood in a similar 

 manner. It may be remarked, in passing, that fossil wood is 

 not confined to the Shinarump conglomerate, but occurs at sev- 

 eral horizons above. In fact two extensive accumulations of 

 wood on the J^avajo Reservation, not yet described, occur 

 200-400 feet above the conglomerate. So far no fossil wood 

 has been definitely assigned to beds below the Shinarump con- 

 glomerate. Wherever observed the Shinarump conglomerate 

 is lenticular, cross-bedded, often excessively so, and variations 

 in structure and texture both vertical and horizontal are char- 

 acteristic. 



The descriptions of the Shinarump conglomerate by Ives, 

 Marcou, Newberry, Simpson, Powell, Dutton, Howell, Mar- 

 vine, Ward, and other observers in the Plateau Province differ 

 in no essential from that given above, and leave no doubt that 

 all are speaking of the same stratum. 



Origin of the Conglomerate. 



A discussion of the conditions affecting the deposition of the 

 Shinarump conglomerate is reserved for another time, since it 

 seems desirable to limit the present paper to stratigraphic con- 

 siderations. Suffice it to say that the conglomerate is sub- 

 aerial in origin, was influenced in deposition by fluctuating 

 climatic control, and that the source of the constituent pebbles 

 has not been satisfactorily determined. 



Stratigraphic Position. 



The Shinarump conglomerate, together with the shales 



