474 THE CRYSTAL FALLS IROF-BEAEING DISTRICT. 



of the bedding, as is also the direction of the elongation of the pebbles so 

 abundant in the conglomeratic layers. 



From the slight changes in dip observed in the beds, as well as the 

 great width of the formation in some places, it is evident that folding must 

 exist. It is probable that in the wider portions of the area occupied by 

 these rocks there are present two or more folds, so closely appressed that 

 the beds on the opposite limbs can not be correlated. Hence they appear 

 as members of a consecutive series of conformable members with a nearly 

 unifoi'm dip throughout. In the narrower portions of the area it can not 

 be told whether more than one fold is r)resent or not. In any event, the 

 folding is practically isoclinal. 



The ledges of the conglomerates and their associated beds occur in the 

 southern portion of the Sturgeon River tongue throughout its entire extent. 

 No exposures have been found north of the granite areas in the central and 

 western portions of the tongue. 



IMPORTANT EXPOSURES. 



The arkoses, the sericite-schists, and the conglomeratic phases of the 

 series can be best studied at the dam of the Sturgeon River near the north- 

 west comer of sec. 17, T. 42 N., R. 28 W. Here they fonn a continuous 

 ledge of well-bedded layers striking N. 83° E., and dipping 85° S., which 

 measures at least 250 yards in width and 400 yards in length. (See PL LII.) 

 The conglomerates are pink in color. They contain immense numbers of 

 white quartz pebbles and bowlders, fewer and smaller ones of pink granite, 

 and many fragments of red feldspar in a matrix composed of moderately 

 coarse granite ddbris. All the fragments and pebbles in these rocks, as well 

 as their matrix, show plainly the effects of pressure (PL LIII.) The matrix of 

 all specimens is more or less schistose, and the coarse sand grains embedded 

 in it are in many cases elongated in the direction of the schistosity. Most of 

 the pebbles and bowlders in the conglomerate are also flat and parallel to 

 the schistose plane. How far these phenomena are due to mashing, to rota- 

 tion into parallel positions during flattening, and to original sedimentation, 

 respectively, can not be determined in most cases, since the schistosity of 

 the rock and the elongation of the pebbles are both approximately parallel 

 to the bedding — i. e., the pebbles are nearly in the positions assumed by 

 unequidimensional pebbles in a well-bedded conglomerate. In a few 



