252 F. C. SCHRADER GEOI.OGICAL SECTION IN NORTHERN ALASKA 



flats and bars at the coast. Inland, these abandoned flats are probably 

 underlain, in part at least, by the lower beds of the Colville series ; but 

 where their edges form the banks of the river at 10 to 20 miles from the 

 coast they seem to be composed of dark muck and ground ice for a 

 depth of 10 or 15 feet below the surface. 



