502 THE GEOLOGY OP MINNESOTA. 



[Potsdam quartzytc, 



tributary to Highwater creek, along a distance of fifteen rods or more from north to south, with a 

 width of two to four rods. Its dip is about five degrees to the southeast or S. 60 E. It is much 

 divided by joints and is thereby somewhat fractured into rhomboidal pieces. Ripple-marks were 

 seen in several places, the undulations being two to three inches wide. Fragments of red pipe- 

 stone up to two inches in diameter occur rarely in this rock. 



Another outcrop is reported one mile northeast from the last, on the N. E. } of section 21, 

 Storden, in a ravine; and others occur a half mile southeast of Carlson's, near the center of section 

 27, in the bed of small ponds through which the brook flows. 



The west part of the S.W. J of section 6, Dale, has considerable exposures of quartzyte, scarcely 

 rising, however, above the general surface of the till, along a distance of twenty rods and more 

 from north to south, on a westward slope, about a mile east from the east end of lake Augusta. 

 These ledges are owned and have been slightly quarried by Peter Schmith. The stone varies in 

 color from yellowish gray to a dull red, is much jointed, and has a dip at the quarry of about five 

 degrees northeast. Laminae of pipestone from a fourth to a third of an inch thick, deep red, 

 traversed by whitish veins, in their predominant red color and soft slaty texture closely like the 

 pipestone of Pipestone quarry, were noted here upon the surface about fifteen feet east of the 

 quarried excavations, occurring at bedding planes along an extent of about two rods. Here, also, 

 fragments of this deep red pipestone, up to one or two inches in diameter, are enclosed in the 

 quartzyte, which is mostly of a more grayish red color. 



Several other outcrops of this rock, similar in extent and character, occur within a distance 

 of a mile to the south and southwest through section 7, Dale, and in the east edge of section 12, 

 and perhaps also of section 1, Amo. These most southern exposures of this area of quartzyte 

 were examined by Prof. Winchell in 1873, and have been described on pages 159 and 160 of the 

 second annual report. The dip at one place near the east line of section 12, Amo, is recorded to 

 be "4 or 5 N. 10 W. The stone is very hard, but banded with light and red beds, evident on 

 the planed surface and on the fractured side." 



The observations of dip recorded in the foregoing pages indicate that 

 these Potsdam strata in Selma, Delton, Stately and Germantown are mono- 

 clinal, dipping generally about five degrees southward; and that probably 

 farther west in Germantown, Amboy, Storden, Dale and Amo, where a 

 greater width is exposed, they are synclinal, on the north dipping about 

 five degrees toward the south, and on the southwest dipping an equal 

 amount toward the northeast and north. From the Little Cottonwood 

 falls in Delton along the distance of three miles northerly to the falls in 

 section 36, Germantown, Prof. Winchell in a recent reconnoissance found 

 numerous outcrops of the rock with a nearly uniform southward dip of 

 about five degrees, from which he computes the thickness of the formation 

 exposed between those points to be approximately 1380 feet. Stratigraph- 

 ically, the lowest of the beds thus observed are at the falls on Mound creek 

 in Germantown, where outcrops extending twelve hundred feet from north 

 to south, with a dip of five degrees toward the south, give a thickness of 

 100 feet for the friable sandstone seen at that place. This forms the base 

 of the strata measured, lying below beds of very hard and compact quartz- 

 yte, which are almost a quarter of a mile thick.* 



*See an instructive paper, by Prof. R. D. Irving, on the nature of the induration of sandstones and quartzytes in 

 Wisconsin, probably of the same kind with the induration of this quartzyte, American Journal oj Science, (3), vol. xxv, 

 pp. 401-411, June, 1883'. 



