of the Paleozoic Outlier of Lake Timiskaming. 297 



to the east. North of the lake, at a higher elevation Pre- 

 cambrian rocks outcrop to the west of the fault-line, while 

 Silurian occurs to the east, so that the faulting relation- 

 ships are clearly evident. The scarp decreases in eleva- 

 tion to the north, due to the irregularities of the surface 

 having been completely obliterated by the later deposits 

 of post-glacial clay. South of Percy island, near Hailey- 

 bury, no Paleozoic rocks are found on the western side of 

 the lake. On the contrary, the lake is here bounded by 

 Precambrian rocks in high cliffs which are in line with 

 the fault-scarp shown in the Paleozoic rocks farther north. 



In regard to the northeast and southwest fracture sys- 

 tem, which includes the northeast extension of Lake Tim- 

 iskaming at the northern end and its continuation south- 

 west in a line through Cobalt lake and the Montreal river 

 between Latchford and Gillies, it is known that a fault is 

 present at Cobalt. This fault has a displacement of 400- 

 500 feet, the downthrow side being to the northwest. A 

 depression of the surface, which the railway follows, ex- 

 tends from Cobalt to Lake Timiskaming, and no Paleozoic 

 rocks are found south of this line on the western side of 

 the lake. On Mann island the rocks are Silurian, showing 

 varying dips, mostly to the north and west. On Brisseau 

 and Bryson islands to the south, Ordovician rocks occur, 

 the sequence suggesting a northerly dip for the strata in 

 this part of the lake. On Wabi peninsula the rocks have 

 a southerly component to the dip, so that between Mann 

 island and Wabi point there is at least a downwarped por- 

 tion under the lake and faulting is not improbable. 



Age of faulting. — Since the Silurian rocks have been 

 broken by the faulting, and glacial and post-glacial mate- 

 rials are undisturbed, it is obvious that the faulting is 

 post-Silurian and pre-glacial. The presence of a fault- 

 line scarp, now over 150 feet high, which was over 400 feet 

 high before the depression at its base was partly filled 

 with post-glacial clay, is in favor of a date for faulting 

 much nearer the Pleistocene than the Silurian. The 

 fault-scarp is relatively slightly dissected by stream 

 action, so that it is believed it could not have been earlier 

 than the Cenozoic, and the probability is that it is late 

 Tertiary, perhaps connected with the widespread crustal 

 instability and accompanying earth movements which 

 took place in Pliocene time. 



The relationships of the northeast and southwest line 



