THE EASTERN AREA. 427 



an erosion before tlie beginning;- of Keweenawan time. We would thus 

 have tlie siniple monocline of the Penokee succession to the west passing 

 into a folded series in the Eastern area. This liypothesis has, however, 

 some serious difficulties to contend Avith: (I) Tlie rocks on the north and 

 the south sides of the synclinal are quite ditfercnt in chai'iicter. (2) Some 

 explanation nnist Ix' furnished for the northern di|)s referred to> in the 

 north fragmental l)elt. (3) The high and variable southern ilips of the 

 greenstone-conglomerates throughout theii- whole thickness and close to 

 the northern dips of tlie rocks of the iron-bearing and fragmental belts to 

 the south nmst be explained. (4) It would seem that if the Penokee 

 monocline passes into a folde<l series more definite evidence would be 

 found of the change as the supposed folded part of the are;i was approached. 



If the position is taken that the apparent southern dips represent 

 cleavage rather tlian bedding the difficulties largeh' disappear. (1) '^Fhe 

 rocks in which the inclinations have most value — that is, al' the rocks 

 which belong to the Iron-bearing member or are very ferruginous and 

 banded and consequent!}' take on a slatj' cleavage with greater diffi- 

 culty — have northern dips whether they occur north or south of tlie 

 greenstone-conglomerates, and these northern dijjs var}- within narrow 

 limits. (2) All the rocks south of the Iron-bearing member, like the 

 quartz-slate of the main Penokee area, have northern di])s, and these dips 

 eoiTespond to the inclination of the overlying iron-bearing belt. (3) The 

 considerable variation in strike and the great variation in tlie apparent 

 southern dips of the clay-slates and greenstone-conglomerates iit once lose 

 significance if regarded as cleavage. (4) By reg'arding the pnrt of the 

 Eastern area wdiich has the southern dips as a simple series it becomes tlie 

 natural link between the rocks of the Penokee series to the west and those 

 to the east which have only northern dips. (5) By regarding this Eastern 

 area as a simple succession we have the same orderly arrangement between 

 the three great series of rocks which obtains to the ^^'estward. 



That slaty cleavage shoiild be found in the Eastern area and nowhere 

 else in the Penokee succession is not at all strange, for the slates here are 

 much finer grained and more clayey than those elsewhere found. Sorby 

 has shown that such material is particularly likely to take on a slaty 



