C URRENT PRE- CA MBRIA N LI TERA TURE 4 I 7 



The Laurentian rocks in general resemble the Grenville series, 

 which belong to the upper division of the Laurentian. They consist of 

 red and gray mica and hornblende-gneisses in beds which can be 

 traced with regularity for considerable distances, together with coarse 

 hornblende and mica-schists and bands of quartz-rock with schistose 

 partings. No limestones have yet been found among those rocks 

 within the boundaries of the sheet, but in the Parry Sound district to 

 the eastward, among similar strata, the writer has traced five bands of 

 crystalline limestone like those of the Grenville series. The gneisses 

 are distinctively stratified and regularly arranged in anticlinal and 

 synclinal forms, according to the structural laws governing stratified 

 rocks ; the average angles of dip are not steep, and in general, so far 

 as their texture is concerned, the gneisses have the characters of 

 altered sedimentary deposits. Cutting the granites are greenstone 

 dikes, with an east and west direction. 



The Laurentian rocks northwest of the Huronian area, outside of 

 the area of the sheet, are considered to belong to the older division of 

 the system. 



The Huronian rocks comprise quartzites, sericite-, chlorite , horn- 

 blende-, and arkose-schists, clay-slates, graywackds, and dolomites. They 

 have a general synclinal structure. The quartzites of the ridges north- 

 west of Killarney form the southern side of the basin, and those of 

 the Cloche mountains the northern side. Along the southern side of 

 the major syncline are several subordinate folds. Associated green- 

 stones are less conspicuous than in the Huronian rocks on the Sudbury 

 sheet to the north. Those present are more largely developed in the 

 tract on the south side of Lake Panache than elsewhere. 



In the space between the Cloche mountains and the range which 

 runs eastward from McGregor Point to Sturgeon Lake, including Bay 

 of Is'ands, McGregor Bay, and the land thence eastward to the junc- 

 tion of the two chains, the rocks belong to a local division of the 

 Huronian which may, for present convenience, be called the arkose 

 series, with its associated rocks. Structurally this area would appear 

 to occupy the central part of the synclinal area between the above- 

 mentioned conspicuous quartzite ranges. Although various forms of 

 arkose or graywacke are the prevailing rocks within this space, there 

 are in different parts of it considerable quantities of gray quartzites and 

 fine quartz-conglomerates, mixed agglomerates and breccias, sericitic 

 and micaceous schists, impure dolomites and eruptive greenstones. 



