ON THE NORTHWEST SHORE OF LAKE SUPERIOR. 393 



It is believed, however, that the confusion in the beds at this place has been the 

 result of more than one disturbance, perhaps of several. Beyond this, the trap 

 ridge, which passes back of Bitobigungk Bay, is seen about half a mile north of the 

 shore. Occasional exposures of a north-10°-east dike (No. 036), which begins in 

 the second large bay below Bitobigungk, are seen rising above the water at the 

 bottoms of the bays, and forming small pockets ; and about the centre of the large 

 bay just named, is a narrow, prismatic dike, bearing north 30° east. The sedimen- 

 tary rocks in the neighbourhood of these dikes are very much altered. In the 

 large bay between this and Bitobigungk, the rocks lying between the ridge already 

 mentioned as forming Bitobigungk Point, and the one passing back of the bay, are 

 shown in the following section. At one point these rocks are traversed by a trap 



a, a. Greenstone. 



b. Shales. 



r. Metamorphosed shale 

 (/. Altered sandstone. 



dike, bearing northeast and southwest, which is not shown in the section above. 

 At the junction of the dike with the sedimentary rock (No. 93), it is very much 

 altered, and for a foot or more is slightly brecciated. The dip of the rock, which 

 is southeast 14°, is not such as to indicate that much violence was done it at the 

 time the fissure was filled with the matter of the dike ; and in this respect it re- 

 sembles the slate walls of many of the narrow dikes in the neighbourhood of Pigeon 

 River. The subjoined figure shows the junction on one side of the dike : 



d. Joint, filled with caleite and zeolites, 



and fragments of greenstone. 



e. Joint, filled with decomposing chlorite. 



a i! c d b 



Next the trap is a seam of fragments, separating it from a joint, six inches wide, 

 filled with decomposed chlorite ; and between that and the sedimentary rock, is a 

 narrow seam, containing calcite and some zeolites. 



The exposure here is mural, and from ten to fifteen feet in height. It is a shale 

 (No. 635), in beds, from one to six inches thick, and near the trap dikes is changed 

 into a hard, firm quartzite, in which numerous crystals are developed. The colour 

 is also changed, for the distance of a few feet, to a purplish red. Between the two 

 north-30°-east dikes, which occur in the bottom of the bay, one hundred and twenty 

 yards apart, the rock has a baked appearance, and in many of the layers, crystals 

 of felspar and quartz have been developed, so as to give it a porphyritic aspect. 

 Near the northwest dike, druses have been formed in the altered rock, containing 

 crystals. The colour is also changed to a deep red. At some places, however, it 

 loses its red character entirely, and resembles a drab-coloured hornstone. Many of 

 these beds are very similar in appearance to the Palisade rocks. 



50 



