EXPOSURES OF THE KEWEENAWAN 325 



formation ; it is broken into blocks, some of huge dimensions lying in 

 many different directions. They have e.very appearance of being shat- 

 tered by profound crustal movements. 



Farther down the river, particularly in section 35 of this same town- 

 ship, are some well marked bluffs on the east side of the river, formed 

 where the stream cuts into amygdaloid beds in the direction of the strike. 

 The strong east wall is of the crj^stalline compact portion of the flow 

 next above an eroded amygdaloid. A series of benches is noted in places 

 where the direction of the stream has caused a transfer of erosion to the 

 westward from one amygdaloidal layer to another still lower. The dia- 

 bases dip east 40 degrees and more ; the strike is, in general terms, south 

 10 to 15 degrees west, magnetic. 



In sections 10 and 15, township 40, range 20 west, are several low ex- 

 posures. They consist of the two usual varietal phases, massive and 

 amygdaloidal. Their attitude was carefully taken and the average meas- 

 urement is: strike, south 10 degrees west; dip eastward, 50 degrees — an 

 average which shows a steady relation to the exposures farther up the 

 river. If the strike and dip be practically unchanged, this easternmost 

 locality represents a thickness of 5,000 feet from the fault line. 



For several miles the river runs in a southeasterly direction and thus 

 cuts diagonally across the strike. Whenever a flow of more than usual 

 hardness is crossed a reef is found. 



In section 24 of the same township occurs in the banks of the stream 

 a conglomerate. It appears to dip westward at a low angle. We have 

 here probably the first westward dipping Keweenawan met in descend- 

 ing this stream. It lies from li to If miles in a direct line eastward of 

 the strike of the exposures in section 15, which most certainly dip east- 

 ward. The axis of the syncline is therefore located within a few hun- 

 dred paces. 



It would thus appear from the nature of the rocks in evidence that 

 the great thickness of the upper Keweenawan sandstones lying along 

 the Saint Croix river in township ranges 42, 43, and 44 has wholly dis- 

 appeared ! Such must be the inevitable conclusion unless the small 

 exposure of westward dipping conglomerate in section 24 be a remnant. 



In section 19, township 40, range 19 west, occur the Big rapids of the 

 Kettle river. The stream falls many feet within a half mile, tumbling 

 over a succession of westward dipping diabases. At one place favorable 

 for measurement, the strike was north 20 degrees east and dip west 20 

 degrees north at 15 degrees. These rocks, on account of their varying 

 hardness and attitude against the stream, that of a succession of dams, 

 cannot form a single cataract. 



This combined circumstance of rock habit and rock attitude doubtless 



