PUBLIC PARKS OF IOWA 135 



was deposited about all the sand particles, frequently the quantity was 

 not sufficient to fill all of the spaces between the grains. As a result, 

 a sandstone easily crumbled was produced. Throughout the quartzite 

 this condition exists. In close proximity to quartzite and in the same 

 beds the rock shades off into firable sandstone and even into uncemented 

 sand. These softer layers are generally thin and quickly give place 

 to the normal quartzite. Well drillings that have penetrated the quartzite 

 show that in the midst of the harder rock there are at times several 

 feet of sand. An example of this sort is found in the well of the B. C. R. 

 & N. railroad at Ellsworth, Minn., one mile north of the Lyon county line, 

 where the quartzite was encountered under 180 feet of drift and fifty 

 feet of shale. It was penetrated to a depth of 315 feet, and frequently 

 sand layers of considerable thickness were found. The color of the rocks 

 varies from pink to purple, red being most prevalent. The coloring matter 

 is oxide of iron, which forms a thin coating around the quartz grains. 

 Near the upper surface and along joints leaching has evidently taken 

 place, for the colors are dull. As determined by the Minnesota survey 

 the rock is composed almost wholly of quartz"; 85.52 per cent consisting 

 of that material. 



On the surface the quartzite is found in but two sections of a single 

 township in Lyon county, and is nowhere exposed in Sioux county. 

 These sections are 7 in Tp. 100, N., R. XLVIII, W., and 11 in Tp. 100, N., R. 

 XLIX W. The first named exposure is found in the north central part 

 of the section and may be seen from the road on the state line. The 

 outcrop is in the bottom of a small valley and is perhaps fifty feet 

 wide with a total length of half a mile. Erosion has removed the drift 

 over this limited area exposing the quartzite which, doubtless, underlies 

 it throughout this corner of the county. Thirty miles to the west it is 

 known that the Benton shale intervenes. Section 11 of range XLIX is 

 in the bottom lands of the Big Sioux. The quartzite here exposed is in 

 the form of a ridge 100 yards wide and 400 yards long, rising to a height 

 of twenty feet. In the bluffs just across the river an exposure of quar.z- 

 ite, evidently a part of this same ridge, rises to a height of fifty feet. The 

 dip of the rock at both the Iowa exposures is six degrees north. Its 

 characteristics are those common to the quartzite in other localities. The 

 metamorphism is general but not universal. Occasionally the rock is 

 soft enough to crumble between the fingers. The joint planes are in 

 two sets at right angles to each other and from two to ten inches apart. 

 Infection 7 there is a beautiful example of oblique lamination. On the 

 same exposure are remarkable glacial striae and grooves. Apparently 

 the drift has but lately been removed from the surface. The maximum 

 depth of the grooves is eight inches, which is considerable when the 

 hardness of the rock is taken into account. There are two distinct seLs 

 of striae, one evidently more recent than the other, since in places one 

 is erased by the other. The corrected readings for these striae are S. 30 

 degrees E. and S. 5 degrees W. It is not necessary to suppose that they 

 represent two ice sheets. The second set was probably formed by the 

 same ice sheet that was responsible for the first, the change in direction 

 indicating the direction of the ice movement during its recesson. 



