NOATAK BASIN 569 



behind the ice-barrier from tlie tributary valley escaped along the south- 

 ern margin of the ice, and had so intrenched its course before the barrier 

 was removed that it did not resume its course on the disappearance of 

 the ice. Gravels up to an elevation of 700 feet above the Noatak River 

 in the canyon have been observed on the hill slopes and bear witness to 

 the fonner high level of the drainage. 



Farther down the iS^oatak, near the point where it makes the big bend 

 to the east, are deposits and topography that may have been formed by 

 glacial activity. Northwest of this place is a broadly open gap not over 

 500 feet above the sea, that appears to have been formerly the direct 

 course of the Noatak to the Arctic Ocean. Instead, however, of follow- 

 ing this course, the river has abandoned this gravel-filled lowland, has 

 swung southward and then eastward, and transected a range of hills 

 1,500 to 2,000 feet in elevation. On the slopes of the hills to an eleva- 

 tion of at least 700 feet above the river are gravel deposits. Near the 

 bend before mentioned is distinct knob-and-kettle topography. The 

 depressions are now occupied by small ponds from 100 to 200 feet above 

 the Noatak. 



The knob-and-kettle topography, the obstruction of direct westward 

 drainage, the course of the Noatak across the topographic trend, and the 

 presence of high gravels all point to a relatively recent change in topogra- 

 phy, the cause of which is not known. Although unsupported by direct 

 evidence, a possible working hypothesis to explain the diversion of the 

 Noatak and the formation of the high levels is that glacial ice, occupy- 

 ing a part at least of the x4rctic Ocean basin, obstructed the former west<- 

 ward discharge of the Noatak and caused outlets south and east of the 

 ice-front to be utilized. According to this assumption, these outlets were 

 uncovered only after lakes had been formed and their surface level raised 

 many hundred feet. After this drainage had been established and had 

 been intrenched, return to its former course may have been prevented by 

 the glacial outwash deposits that would have accumulated in the old 

 valley. It is also possible that the till reported by Hershey^ near Kot- 

 zebue and the peculiar position and outline of Hotham Peninsula may 

 have been formed at the eastern margin of the ice that obstructed the 

 Noatak, rather than at the western front of a glacier from the Kobuk, 

 for it seems almost certain that ice did not come down the Kobuk below 

 the Kallareechuk. 



It is realized that the above is little more than a speculation and re- 

 quires much more corroborative evidence than is at hand before it can be 



3 O. II. Ilershey : Journal of Geology, vol. 17. pp. 83-91. 



