210 THE VERMILION IRON-BEARING DISTRICT. 



attention was paid to the contact between the iron formation and the green- 

 stone, but very careful search showed no indication of any clastic material 

 between them. Neai'ly everywhere this greenstone is perfectly massive ; in 

 a few places it shows a slight schistosity parallel to the contact, probably 

 the result of the shearing caused by the close folding. The iron formation 

 is closely infolded in the syncline in the greenstone. The broadest part of 

 the syncline — that is, the place where the jasper has its greatest width — is 

 at the to]) of the hill. From this point down to the lake shore the descent 

 is at a rather sharp angle, and the fold has here been beveled off. As a 

 result of this beveling a subordinate anticline is first brought to the surface 

 as an oval area near the center of the main syncline, and as we come still 

 farther south the deeper truncation of the fold has separated the main 

 syncline into two subordinate synclines occurring in very narrow belts 

 separated by the intermediate greenstone area, as shown in fig. 7, from a 

 sketch made in the field. 



On the portage between Big Rock Lake and Emerald Lake, north of 

 the international boundary, a mass of iron formation was seen which was 

 estimated to be about 100 feet across, north and south. Its contact with 

 the greenstone south of the trail was found, and is here knife-like in its 

 sharpness, there being absolutely no clastic material between the greenstone 

 and the jasper. The jasper is much broken, has very fine jointing, and 

 the brilliant red variety makes up the greater portion of the formation. 

 Some of the bands of the bright-red jasper are 6 inches across. Bands of 

 white chert are infrequent, although present, and the iron ore in narrow 

 bands makes up the remainder of the formation. 



INTRICATE FOLDING OF SOUDAN FORINIATION. 



The intricate folding of the iron formation can be well seen at a 

 number of places just north of the international boundary; for example, 

 on Emerald Lake, where it is most beautifully and curiously folded. On 

 the west side of the largest island, which is about in the center of the 

 lake, bands of the jasper are bent into fan-shaped folds and curious 

 interlockings, a description of which Avould be almost incredible. The 

 jasper, although so rigid, has evidently obeyed the law of flowage in filling 

 up every chink and corner throughout the complexly deformed mass. 

 How far these rocks were folded before complete jasperization took place 

 is questionable. At this ledge the Inroad jasper bands turn around and 



