414 REVIEWS 



continental Railway crosses the northern part of the county and this 

 part can be easily reached. 



This area lies within the Laurentian Plateau and is characterized by 

 a remarkable uniform relief but the surface in detail is irregular. The 

 minimum elevation is almost everywhere more than 800 feet, and the 

 maximum less than 2,000 feet; thus the range in elevation is seldom 

 greater than 1,200 feet. The northern part of the county is drained by 

 the Bell and Harricanaw rivers flowing into James Bay, and the south- 

 ern part by the head waters of the Ottawa River flowing into the St. 

 Lawrence River. 



A very widespread base-level represented by the erosion surface 

 between the basal complex and the Cobalt series or other late pre- 

 Cambrian formations is still preserved. So also is the peneplain devel- 

 oped before the advance of the early Paleozoic seas. Since these early 

 Paleozic rocks are approximately horizontal, all the movements of this 

 great area since that time have been due to regional uplift, warping, and 

 faulting. Of these, faulting has been the most important. 



Another very noticeable physiographic feature is the large number of 

 linear valleys, which, when classified according to general direction, fall 

 into three groups striking approximately northwest, north, and north- 

 east. The evidence in favor and against the faulting hypothesis of 

 origin for these valleys is given. The faulting hypothesis most easily 

 accounts for these valleys, and is assumed to be the most reasonable 

 explanation, although very little field evidence of faulting along the 

 valleys has been found. These valleys are post-Silurian and pre-Glacial. 



The rocks occurring in Timiskaming County fall into the following 

 four divisions: (i) the basal complex, (2) the Cobalt series and associated 

 intrusives, (3) the Ordovician and Silurian sediments, and (4) Quaternary 

 Glacial and post-Glacial gravels, sands, and clays. Detailed Uthologic 

 descriptions are given of the many different rock types represented, 

 with notes on the structure and origin of many of the metamorphic 

 types. Based on lithology and origin, the rocks of this region may be 

 grouped into three parallel belts running in a northeasterly direction. 

 Sediments belonging to the Grenville series characterize the south belt; 

 banded gneisses mostly of igneous origin, the central belt; and volcanics 

 and clastic sediments, the Pontiac series, the north belt. In the southern 

 part of Timiskaming County inclusions of Grenville sediments are found 

 along the southern edge of the banded gneiss belt. Because of the many 

 difficulties and uncertainties of long-distance correlation of very intensely 

 metamorphosed pre-Cambrian formations outUned in chapter IV, no 



