226 Pumpelly and Van, Hise — Observations upon 



series which contains them as detritus is of later age. The exist- 

 ence of jasper fragments in the Red Jasper Conglomerate 

 was interpreted by Logan as "showing their derivation from a 

 more ancient stratified rock." 



Thus, so far as evidence was found by us, it bears in the 

 same direction as the facts cited by Dr. Winchell, except that 

 we would place the unconformity in the Huronian above the 

 lower limestone member, whereas he places it below this for- 

 mation. The Lower Huronian series would then comprise, in 

 ascending order, Logan and Murray's ISTos. 1 to 4 inclusive, the 

 whole being according to these authorities about 5000 feet 

 thick ; while the upper series would comprise Nos. 5 to IS 

 inclusive, the whole being about 13,000 feet thick.* 



Relations of Loioer Huronian to the Basal Complex, 



Contact near Garden River. — On the left side of the road 

 leading from the Canadian Sault Ste. Marie, to Garden River, 

 is a huge bluff of lower slate-conglomerate which has a north 

 and south extent of at least an eighth of a mile. This con- 

 glomerate has all of the features heretofore described, that is, 

 a vertical bedding, cleavages in various directions, and a semi- 

 crystalline character. In passing from south to north the con- 

 tained fragments as a whole increase in magnitude, although 

 even after the exposure becomes strongly conglomeratic other 

 layers lower down may be found which are nearly or wholly 

 free from coarse detritus. When the north end of the exposure 

 is reached the rock has become a magnificent basal conglomer- 

 ate, consisting almost wholly of granite fragments set closely 

 together and forming a stucco. The sparse fine-grained mat- 

 rix is here composed of materials largely indentical with the 

 coarse fragments. Mingled with the numerous great bowlders 

 some of which are several feet in diameter are other bowlders 

 of intermediate sizes. In the passage from south to north 

 along the bluff there is also noticed a tendency for the bowl- 

 ders to become angular. Turning now around the northwest 

 corner of the ledge, and following along its foot to the east, 

 there appears just north of a sharp ravine not more than 100 

 steps from the conglomerate a great bluff of massive red gran- 

 ite (the syenite of the early Canadian geologists). On the 

 talus slope of this bluff were found numerous angular blocks 

 which are a genuine recomposed granite. These on their 

 freshly broken surfaces so closely resembled the solid ledge 

 that they can not be discriminated from it, but on the weath- 

 ered surface their complex character is readily recognized since 

 the discrete fragments of which they are composed stand out 



* Geology of Canada, 1863, pp. 55-57. 



