618 THE GEOLOGY OF MINNESOTA. 



[Granite and gneiss. 



of Cretaceous shale, exposed in the edge of Dakota, as described on a follow- 

 ing page, are seen along Traverse and Big Stone lakes, or between them. 



One mile below Big Stone lake, a coarse reddish granite begins and thence occupies nearly 

 the whole valley for three miles, lying in Ortonville and the northwest part of Yellow Bank, its 

 highest portions rising 50 to 75 feet above the Minnesota river. 



It again appears in low outcrops two and three miles easterly from the foregoing, in sections 

 30 and 32, T. 121, R. 45, the first of these being in Odessa, on the north side of the river a little 

 west of Stony run, and the second in Yellow Bank, at Mr. Frederick Frankhaus 1 , south of the 

 Minnesota and a half mile west from its ford. At the last named locality this rock has few 

 joints, their distance apart being sometimes ten feet or more. 



Two to six miles farther southeast, in T. 13O, R. 45, which extends from the mouth of 

 Yellow Bank river to Marsh lake, similar granite forms abundant outcrops, mainly on the south- 

 west side of the Minnesota river, in Yellow Bank township, rising 50 to 75 feet in their highest 

 portions. Professor Winchell describes the formation here as follows: " The crystals of feldspar 

 are large and flesh-colored, or red. Yet the granite also varies to a lighter color, in which the 

 feldspar is nearly white. It shows, in the latter case, a perpendicular jointing, the planes being 

 one or two or three inches apart. The whole exposure consists of bare, massive, rounded knobs, 

 cut into angular rhomboidal blocks, by jointing planes, but in no place showing the dip seen 

 lower down the Minnesota river." 



North of the last, two ledges of this rock, small in extent and rising only a few feet from 

 the surface of the drift, but lying at hights 40 or 50 feet above the river, were noted about a 

 mile apart, half way between Odessa and Correll stations, the west one being a little south of the 

 railroad, while the east one is crossed by it. All the foregoing exposures are granite, very hard 

 and durable, but mostly too coarse and variable in grain or texture and too much jointed to 

 promise well for quarrying. From the color of its predominant ingredient, the feldspar, this 

 granite takes its prevailing reddish tint. It is variously intersected by joints, but does not ex- 

 hibit the gneissic lamination which is generally noticeable in the southeastward continuation of 

 these rocks. 



For fifteen miles from the upper part of Marsh lake to the middle of Lac qui Parle we have 

 no observations of ledges. In section 32, T. 1 19, R. 42, an island of rock occurs in Lac qui 

 Parle, and two ledges outcrop on its southwest side. About two miles southeast, or one and a half 

 miles above the foot of the lake, are several small and low exposures of rock, occuring at each 

 side and also as islands. On the northeast side this is gneiss, mostly with N. E. to S. W. strike. 

 The following description of this vicinity, by Prof. Winchell, who examined the Minnesota val- 

 ley in 1873, is taken from the second annual report of this survey. "Near the lower end of Lac 

 qTii Parle lake, granite appears on both sides of the lake. It is usually inaccessible from the 

 prevalence of water; but in the dry months of the year it can be reached on the northeast side 

 without any trouble, except from tall grass and bushes. There are three or four small bare spots 

 on the southwest shore that can be seen, and three or four others that rise up in the midst of the 

 lake. Two of these spots of bare rock also occur on the northeast side, near the foot of the lake. 

 This rock, so far as can be seen on the northeast side, shows very much the same composition as 

 farther down the river. It contains quartz, mica and flesh-colored feldspar, with patches and 

 veins of quartz, some of which are mingled with porphyritic feldspar. The exposed surfaces are 

 annually submerged, or nearly so, and do not exhibit very plainly such markings as indicate sedi- 

 mentation or dip. There seems to be an indistinct arrangement of the mica scales, so as to give 

 the rock a schistose structure, but this, although generally running N. E. and S. W., does not 

 have that direction invariably, and does not at all represent the lamination or bedding seen be- 

 low" [farther southeast along the Minnesota river]. ''In only one small area can there be seen what 

 looks like the same bedding, and there it is but six inches in thickness, the beds being one or two 

 or three inches, with a dip of 75 toward the S. E. Jointing planes divide the whole mass into 

 blocks and rhombs, four or five or six feet in thickness. There is considerable low land about 

 the lake, much of which is flooded at the wet season of the year, but it is stony and bushy, and 

 has the appearance of rock in a great many places near the surface. Such appearances are seen 

 the whole length of the lake, and especially on the northeast side. About three miles above the 



