88 IOWA ACADEMY OF SCIENCE' 



small valleys are V-shaped, often canyon like; the slopes from the 

 divides are usually steep and broken by many gulches. 



The largest stream is Bering River, which takes its rise in the lakes at 

 the margin of Bering glacier. Its chief tributaries receive their waters 

 from the abundant rainfall and from the melting snows of Martin Eiver 

 glacier and its lobes. The tributary Canyon Creek, flows from beneath 

 the margin of the glacier; Stillwater and She,pherd creeks drain lakes 

 Kushtaka and Charlotte respectively. Both of these lakes are of glacial 

 origin. 



The precipitation of the region is probably in excess of 130 inches 

 annually. The snowfall is very heavy. Above an elevation of 1,500 

 feet considerable snow is present even during the summer months. 



The climate is not severe, the coldest weather recorded being 2° F. 

 above zero. The average winter temperature is about freezing point, 

 the average summer temperature between 50° and 55° F. 



The slopes are usually timbered with spruce and hemlock to an eleva- 

 tion of more than 1,000 feet. 



The Geology of the Region. 



The chief rocks of the coal field consist of indurated sediments of 

 Tertiary age, and of unconsolidated stream deposits, abandoned beaches, 

 and morainal material of Quarternary age. Associated with the Ter- 

 tiary sediments in the northeastern part of the fields are narrow dikes 

 and sills of diabase and basalt, which are either Tertiary or post-Ter- 

 tiary in age. The morainal deposits extend only a few miles beyond 

 the present limits of glaciation. 



The Tertiary sediments have been divided by Dr. IMartin into three 

 formations, the StillM^ater, the Kushtaka, and the Tokun. The Still- 

 water is the oldest formation and consists chiefly of sandstone and shale 

 with a thickness of about 1,000 feet. The Kushtaka overlies the Stillwater 

 conformbly and is that part o fthe Tertiary which contains the beds of 

 coal. It has a thickness of about 2,000 feet, made up of coarse arkose, sand- 

 stone, shale, and beds of coal. Complete sections of the formation are 

 not well exposed, and hence the number of seams of coal is not well 

 known. The evidence suggests more than a dozen seams varying in 

 thickness from 6 inches to more than 35 feet. The Tokun formation 

 overlies the Kushtaka conformably, and consists of about 2,500 feet, 

 chiefly of sandy shales, but containing also, sandstone and a subordinate 

 amount of limestone. All the evidence thus far found indicates that 

 the Stillwater formation is marine, the Kushtaka non-marine and the 

 Tokun marine. 



