REVIEWS 175 



portions of the area mapped are occupied by Laurentian and Huronian rocks, of 

 which the Laurentian rocks are in the larger areas. They consist of granites and 

 gneisses, some of which are intrusive into the Huronian, and some of which are 

 probably basal to it. Huronian rocks are found in small areas at Cross Lake, at Pipe 

 Lake, and in the large area extending from Wekusko- Lake to Athapapuskow Lake. 

 They consist of conglomerates, quartzites, basic eruptives, and greenstones, and altered 

 schists, similar to rocks of Lawson's Keewatin and Couchiching series. 



A. P. Low. " Report on the Geology and Physical Character of the Nasta- 



poka Islands, Hudson Bay," Annual Report of the Geological Survey of 



Canada for igoo, Vol. XIII, Part DD, 1903. 



Low describes the geology of the Nastapoka Islands, Hudson Bay. The rocks 



forming the islands are in descending order as follows : 



Feet 



1. Rusty-weathering, dark gray siliceous rock containing ankerite (carbonate of iron and mag- 

 nesia, and magnetite --------■------. 20-100 



2. Dark gray siliceous rock containing magnetite, with small quantities of ankerite - - 50-250 



3. Red jaspilyte rich in hematite ore -..-.-...... 10-100 



4. Red jaspilyte poor in hematite ore .-■ 5-20 



5. Purple, or greenish-weathering, dark green, graywacke shales 10-70 



6. Red jaspilyte poor in hematite ore -.-.. . ...... 0-5 



7. Light greenish-gray sandstone and shale ........... 10-300 



8. Fine-grained dolomite .......--....-. 0-50 



There is a general dip toward the westward, or toward the sea, of from 5 ° to 15 ° 

 There are north-and-south faults, the upthrow being almost on the west side, with the 

 result that the rocks appear in north-and-south ridges. The displacement is small and 

 rarely exceeds one hundred feet. Another system of faults lies transverse to the first 

 system. 



Large areas of similar unaltered sedimentary rocks occur throughout the peninsula 

 of Labrador, and are probably the equivalents of certain of the iron-bearing series 

 about Lake Superior and of those to the westward of Hudson Bay, hand specimens 

 from these localities being undistinguishable. On former maps of portions of the 

 peninsula of Labrador, the areas of rocks belonging to this formation have been 

 colored as belonging to the Cambrian formation, and in the earlier .reports on 

 this region the rocks were thought to be a part of that system, owing to their 

 unaltered condition, in contrast with all the other rocks of that vast area that were 

 either crystalline granites and other irrupted rocks, or crystalline schists and 

 gneisses, so completely metamorphosed as to have lost all trace of their original 

 sedimentary nature, if any were sediments. These highly crystalline rocks were 

 classed as Laurentian or Huronian, and were considered to be much older than the 

 unaltered rocks of the so-called Cambrian areas. More extended and closer study of 

 both the unaltered and crystalline rocks, and of their relations to one another, has 

 changed the views of the writer; and he now considers the unaltered, so-called Cam- 

 brian rocks to be the equivalents of many of the gneisses and schists classed as Lau- 

 rentian (Grenville series), and the Huronian areas of the Labrador peninsula to 

 represent a portion of the unaltered rocks and their associated basic eruptives (traps, 

 trap-ash, etc.), altered by the irruption of granite and rendered schistose by pressure 

 The granites which have been classed as typical Laurentian, always cut and alter the 

 bedded rocks wherever seen in direct contact with them, and are consequently newer 

 than the latter. 



