COTTONWOOD AND JACKSON COUNTIES. 5Q1 



Potsdam quartzyte.] 



a ravine tributary to the Watonwan river. No other outcrops were learned of upon the head- 

 streams of this river farther eastward in Delton. 



A ledge of this rock, very remarkably striated, as described on a following page,, and bear- 

 ing rude Indian inscriptions, is found on the ridge about a mile north-northeast from the Little 

 Cottonwood falls and quarry, being in the north part of the N. W. J of section 9, Delton. It has 

 an area about twenty rods long from east to west, and four to eight rods wide. The dip of its 

 stratification was not distinctly seen, but is believed to be about five degrees southward, which 

 is the slope of the surface. Numerous figures are pecked on this rock, representing animals, ar- 

 rows, etc., similar to those inscribed by the Indians on the quarlzyte beside the boulders called 

 the Three Maidens, near the Pipestone quarry. From this ledge westward the same typical 

 quartzyte frequently outcrops upon the higher part of this ridge and on its northern slope through 

 the northwest part of Delton, northern Amboy and northeastern Storden. 



In the S. W. \ of section 2, Amboy, a ravine ten to fifteen feet deep extends east-northeast 

 in a straight course about forty rods, varying from two to three rods in width, bordered by verti- 

 cal walls, ten to fifteen feet high, of rough, thick-bedded quartzyte, of red or reddish gray color, 

 nearly level in stratification, mostly much divided by joints. The eastern half of this ravine 

 holds a long pool, ten to twenty feet wide, and five to eight feet deep. At the top of the wall of 

 rock south of the west part of this pool, the much jointed, deep red, striated surface is in many 

 places soft and like pipestone to the depth of an eighth of an inch; but within, these small jointed 

 masses are gritty and hard, the pipestone being only a thin coating at the bedding-planes. At 

 the western end of this ravine, on its north side, eight feet above the rivulet that flows east into 

 the pool, this rock encloses a layer, nearly level, varying from four inches to a foot in thickness, 

 somewhat like the pipestone of the famous quarry in Pipestone county, having nearly the same 

 very fine texture and dark red color, but not so hard, and at this place, through its extent of 

 twenty feet exposed to view, easily divisible into small flakes and fragments because of joints, 

 and therefore not seen in any solid mass. The edge of this layer has been mostly removed by 

 weathering to a depth of two to six feet into the wall of tough, reddish gray quartzyte, which 

 overhangs and underlies it. The divisions of this very fine-grained bed from the coarse quartz- 

 yte are not definite lines, but these unlike sediments are more or less blended and interstratified 

 through one to six inches. Both above and below, the quartzyte in some portions contains peb- 

 bles up to a third or half of an inch in diameter, and is quite variable in texture, but is nowhere 

 finely laminated. At a few places the pipestone also is found to contain these small gravel 

 stones; and a few fragments of pipestone up to three inches in diameter are seen enclosed in the 

 quartzyte within one to two feet above the pipestone layer. 



Picturesque falls are produced by this formation in the N. E. \ of section 36, Germantown. 

 The rock here is mostly a very coarse-grained, thick-bedded sandstone, slightly iron rusty or red- 

 dish in color. Nearly all of it is somewhat friable, being thus unlike the other exposures of this 

 formation in this county. In some portions, however, it is here very hard and compact, and then 

 usually has a deeper red hue. Its dip is about 5 S. 10 E. Besides this general dip, the beds 

 often show oblique lamination. This rock is in some places slightly conglomerate, holding peb- 

 bles of white quartz, and less frequently of red felsyte, or possibly jasper, the largest seen being 

 an inch long. These falls are about two miles northeast from the gorge last described, being on a 

 lower part of the same stream, which is one of the sources of Mound creek. Along its intervening 

 course and within short distances from it on each side this formation has frequent outcrops, 

 notably for a quarter of a mile south and southwest from the falls. The stream descends thirty 

 feet in a succession of little cascades, within a distance of twenty rods; next below which is a basin 

 some six rods long and four rods wide, bordered by vertical or overhanging walls of rock, about 

 thirty feet high. At its east end this basin is so contracted that for a distance of about twenty 

 feet these walls of rock are only eight to fifteen feet apart. Below, for the next twenty-five rods, 

 the gorge is four to six rods wide, bordered by vertical walls of reddish sandstone or quartzyte, 

 which decline from thirty to twenty and ten feet in hight. The same rock is seen thence neaily 

 all the way for a half mile east, mostly forming cliffs fifteen to twenty feet high at the south side 

 of this creek, to the junction of another stream from the south in section 31, Stately, Brown 

 county, which also has an interesting fall formed by the quartzyte. 



The most western exposure of this rock learned of in Cottonwood county is in the N. W. J 

 of section 28, Storden, on land of C. P. Carlson. Typical quartzyte, very compsct and tough, 

 varying in color from dull red to slightly reddish gray, is here exposed in the bed of a stream 



