on the Navajo Reservation. 109 



by hundreds. Two bowlders of porphyritic granite, 14 x 8 

 feet and 5x3 feet respectively, stand isolated on the dune- 

 covered flat fully a mile from their nearest companions. The 

 field entirely or in part mantled by these materials is about 1*2 

 square miles, but individual fragments are much more widely 

 scattered. The size and mode of distribution of these erratics 

 are illustrated in figures 3, 4 and 5. 



Specimens collected from the drift include the following : 

 sandstone, shale, limestone, biotite granite, garnetiferous dio- 



Fig. 5. 



Fig. o. Granite bowlders, Garnet Eidge. 



rite, diabase (?), minette, granite gneiss, porphyritic granite 

 gneiss, garnetiferous diorite gneiss, muscovite schist, chlorite 

 schist, slate, hornstone, quartzite, garnet, peridot, lustrous feld- 

 spar, quartz, chalcedony, augite, diopside, epidote, soapstone, 

 tremolite, asbestos. None of the igneous and metamorphic 

 rocks included in the list are found in place within 100 miles 

 of this area, and the nearest outcrop of Pennsylvanian lime- 

 stone occurs in the bed of the San Juan river 20 miles north. 

 It thus appears that this deposit is local and that its position 

 and character are peculiar. 



Features suggesting glaciation. — The photographs (figs. 3 

 and 6) bear out the statement of Sterrett, "The general 



