SNAKE RIVER VALLEY EXPOSURE 353 



an enlargement of Snake river, clue to the obstruction presented by the 

 remarkable series of lava flows of Keweenawan diabases, diabase amyg- 

 daloids, tuffs, and associated conglomerate beds which begins at the foot 

 of Cross lake and extends down the river for nearly 2 miles. Along the 

 north side of the lake the modified till is capped by an unusuall}^ deep 

 and wide exposure of dune sand. 



The exposure is a typical one. The loess-sand at the top is from 2 to 

 4 feet thick along a vertical front facing the lake for hundreds of feet. It 

 is of fine texture, brownish gray in color, and non-stratified and furnishes 

 a subsoil through which roots of trees, shrubs, and grasses readily make 

 their way. The color and texture are the same as at other localities. 

 Below this cap of wind-deposited material is a fine evenly textured strat- 

 ified sand. This modified drift is somewhat argillaceous and holds 

 water more tenaciously than the dune sand above it, thus producing 

 zones of springs. It extends downward at least to the water, thus mak- 

 ing a minimum thickness from 8 to 10 feet. The color and composition 

 of the sand are nearly identical with those of the overlying eolian drift, 

 but the distinction of stratification in the former is sharp and clear. 



Other localities in Snake River valley. — At the mouth of Snake river, in 

 section 36, township 39, range 20 west, and section 31, township 39 

 range 19 west, lie extensive exposures of an eolian sand plain. The 

 glacial drift consists of a fine pink cla5'ey sand somewhat stratified ; the 

 water deposit is a bed of modified boulder till lying upon the former. 

 The most conspicuous exposure of the wind deposits of the locality lie 

 above these near the junction of the Snake and Saint Croix rivers. A 

 high ridge of modified drift lies somewhat parallel to the Saint Croix 

 river and one-fourth mile distant; this has been cut squarely through 

 by the Snake. To the east of this drift extends an eolian sand plain, 

 nearly level and occupying the entire triangle between the ridge and 

 the two rivers. The dune sand composing this eolian deposit is from 15 

 inches to 3 feet in thickness, and is covered with a heavy vegetation. 



KETTLE RIVER VALLEY 



Along Kettle river are several interesting exposures of eolian sands. 

 From them a plain in section 32, township 40, range 19 west, is selected 

 as particularly interesting. Its extent could not be determined, owing 

 to its lying in a forest region, but it is estimated to be several miles long 

 and stretches northward and southward on the east side of the river. In 

 the south part of the section the river in its southward course strikes a 

 mass of hardened Keweenawan diabasic tuff and is deflected squarely 

 to the east. Soon a stretch of the river is reached where for nearly half 

 a mile the north bank has been freshly cut by floods, and there stands 



