on the Navajo Reservation. Ill 



with tillites, but as suggested elsewhere* the shape of pebbles 

 is of little significance especially in small outcrops. 



Disregarding the possibility of an igneous origin of the 

 peculiar conglomerate interbedded with the sediments, the 

 assumption of glaciation during Mesozoic time is directly 

 opposed to the physiographic, evidence. The color, composi- 

 tion, texture and structure of the sediments indicate a warm, 

 arid climate, and uninterrupted sedimentation. Under such 

 conditions the presence of vigorous glaciers is not to be 

 expected. It is believed by the writer that the demonstration 

 of suitable climatic conditions is an essential feature in the 

 recognition of ancient glacial deposits. 



Position of the "glacial" conglomerate in the stratigraphic 

 column. — After confirming the observation of Sterrett that the 

 " glacial " materials not only covered the surface, but were 

 also interstratified with undisturbed sandstones and shales, a 

 section of Garnet Ridge was measured as follows : 



Section of Garnet Ridge, Arizona. 

 Taken on N. 40° W. line Dip of strata, 40° E. / 3° 



Feet 



1. Sandstone, grey to white ; fine, uniform grain, except 



for millet seed grains cemented on bedding planes 

 and cross-bedding laminae; ripple marks and mud 

 cracks present. Grains of clear, round quartz, white 

 with rare red and black individuals, poorly cemented, 

 cross-bedded at low angles rarely tangential. Inter- 

 sected by seams of calcareous sand 1/100-2 inches 

 in width. Prominent joints N. 40° E. and K 40° W. 25 



2. Arenaceous and calcareous shales and sandstone. Light 



red, dark red and brown in alternating bands, 1 to 3 

 feet in thickness. Cross-bedding poorly defined, but 

 bedding planes irregular and wavy and rock 

 traversed by undulating streaks and minute faults 

 and folds - 30 



3. Sandstone, grey, white and variegated ; calcareous, 



friable, irregularly bedded, imbricated and cross 

 bedded 10 



4. Shales, arenaceous and argillaceous, with variable 



amounts of sandstone ; dark red, light red, green- 

 white, ash grey or variegated in color. Within a 

 few feet along strike shale in places replaced by 

 lenses of calcareous sandstone built of overlapping 

 short laminae.. .... 15 



5. Sandstone, light red, white on fresh fracture ; cal- 



careous, irregularly bedded, ripple marked 2 



* Gregory: Note on the Shape of Pebbles, this Journal, xxxix, pp. 300- 

 304. 1915. 



