COTTONWOOD AND JACKSON COUNTIES. 503 



Glacial striae.] 



Fifteen miles south-southwest from the rock outcrops of Dale and Amo, this Potsdam 

 formation is reached in the railroad well at Heron Lake at a depth of 186 feet, its first 34 feet, to 

 a total depth of 220, being a reddish quartzyte or sandstone, underlain by a whitish gray quartzyte. 

 This is the only well in Jackson county which goes through the drift, and no wells were learned 

 of in southenv-or western Cottonwood county that penetrate to the bed-rock. 



It does not seem certain that the Heron Lake well encounters anything but drift deposits 

 above the Potsdam quartzyte; but its section from 115 to 186 feet may be through Cretaceous 

 beds, which, however, were learned of in no other well in these counties. The order of deposits 

 found was soil, 2 feet; yellow till, 13; blue till, 100; yellow clay, 10; dark, very hard and dry, fine 

 silt, like dried mud, 16 feet; light gray clay, free from gravel, 24; and interstratified sand and fine 

 gravel, 21 feet, being in total 186 feet, to the Potsdam rocks before described. 



Drift and contour. 



The surface of the Potsdam quartzyte in many places shows distinct 

 glacial markings, notes of which are presented in the following table. 

 These bearings are referred to the true meridian, from which the magnetic 

 needle here has a variation of about ten degrees to the east. 



Courses of glacial striae, in Cottonwood county. 







Selma, N. E. } of sec. 25 S. 20 E. 



Selma, S. E. \ of sec. 23 S. 20 E., 



and varying from this two or three degrees on each side. 



Delton, S. E. } of sec. 30 S. 15 E. 



Delton, S. W. } of sec. 18 S. 15 E. 



Delton, N. W. \ of sec. 18 S. 25 E. 



Delton, N. W. \ of sec. 9 mostly S. 25 to 40 E.; 



also all courses from S. to S. 80 E., intersecting upon the 



same surface. 

 Amboy, south part of sec. 2, near (north of) a school house. . , mostly S. 40* E.; 



and, within a distance of one rod from striae of this course, 



also S. 45 and 55 E. 



Amboy, S. W. J of sec. 2, at the pipestone locality, about a 



quarter of a mile northwest from the last S. 35 to 50 E., 



and rarely deflected to S. 70 E. , all intersecting on the same 



surface. 

 Germantown, N. E. J of sec. 36, about thirty rods southwest 



from the falls S. 30 E. and S. 70 E. (fig. 35) 



Five rods east from the last, stria? were noted at different 



spots within a space of about one rod square of nearly level 



rock, bearing S. 30, 50 and 70 E. 



Generally here these marks have been effaced, and none could 



be found on the ledge described in the N. W. J of sec. 28, 



Storden. 



Dale, S. W. } of sec. 6 S. 20 to 25 E. 



Dale, south part of sec. 7 S. 34 E. 



Amo, east part of sec. 12 S. 30 to 32 E. 



Near the Little Cottonwood falls, in the S. E. J of section 8, Delton, and at points on the 

 north side of the quartzyte ridge in the northwest part of this township, the ar.gles of projecting 

 ledges of this rock were observed to be rounded off by glaciation. 



The most remarkable deflections and intercrossing of glacial striae ever seen by the writer, 

 were found at the locality mentioned in the N. W. } of section 9, Delton. It is on the southern 

 slope of the rid^e formed by this quartzyte, as already described. This ridge is elevated about 

 300 feet above the lowland, which, from its base two or three miles farther north, extends north- 

 ward more than fifty miles, across the basin of the Minnesota river; but its bight above the aver- 



