246 THE PENOKEE IRON-BEAKlNd SEUIES. 



there aiiv indicntiou of a tragniental character. Occasionally, it is true, in 

 narrow transition bands between the iron-bearing and the fragmental belts, 

 there is mingled with the nonfragniental material a small quantity of frag- 

 mental ([UJirtz and feldspar. Also at the eastern extremity of the distinct 

 clastic and nonclastic sedimentation have alternated to some extent. How- 

 ever, this very a)>iic;n-Mnce of fragmental material but more strongly empha- 

 sizes the fact of the nonfragmental character of the belt as a whole, by 

 brino-ino- into the same thin sections clastic and nonclastic material. The 

 clastic particles are recognized at a glance as entirely different from the 

 mass of the tinelv crystalline or partly amori)hous completely interlock- 

 ing material which composes the rocks of the Iron-bearing member. (PI. 

 XXXV, Fig. 1.) 



(•2) The rocks of the Iron-bearing member are laminated. Through 

 large parts of its area the lamination is as perfect and minute as is })ossil)le 

 in any sedimentary stratified rock. These regularly laminated portions 

 are found at all horizons, and nowhere is a fair degree of regularity of 

 stratification absent. The most perfectly laminated parts of the belt are 

 of the first typ(* of rock — the chert)' ii'on carbonates. As the lamination 

 becomes less regular, rocks of the second and third types — the ferruginous 

 cherts anil the actinolltic slates — appear. 



(3) There have been observed at many i)laces actual stratigraphical 

 transitions of the regularly bedded carbonates into the remaining rocks of 

 the belt. This gradation sometimes occurs in passing from east to west, as, 

 for instance, the chei'ty carbonates and tlie ferruginous cherts grade into the 

 actinolitic " slates, or the gradation maybe a transverse one ; that is, the 

 chertv iron cai-bonatcs at a higher li(.)rizon grade into the ferruginous cherts 

 at lower horizons. This sti-atigraphical grad;ition of the three types of 

 rock into each other is alone suflicient to make very ])robable for all of 

 them a conunon origin. The gradation is repeated in thin sections, nearly 

 all stages of the various transitions being clearly \vork(-d out. 



Tlic orif/iiKil roi-k. — 'i'he foregoing facts all point unmistakably in the 

 same direction; tliat is, to the conclusion that these rocks at one time were 

 cherty iron carl)onates. 'Hiere maybe differences of opinion as to whether 

 at some earlier staye thev did not have anotlier form ; there may be diffex'- 



