REPORT OF THE DIRECTOR igi2 137 



channel as the gulf lands rose. It is not to be conceived that this 

 channel through the gulf is as ancient as the channel between the 

 shores of Gaspe and the Quebec Labrador. The lands which the 

 lower channel cuts are of later birth than those at the north and in 

 its earlier stages we may believe that the river debouched into a 

 shallow sea much as it does today into the gulf. The student of the 

 chart will observe that there is a branch channel leading off in the 

 direction of the Strait of Belle Isle but it is a shallower trough than 

 that to the southeast. The line of deepest water is in the southeast 

 channel and there is a difference in maximums of depth between 

 the two of 155 fathoms, the greatest depth in the northwest trough 

 being 145 fathoms and in the southwest 300 fathoms. 



The southeast channel drops quite steeply 1700 feet below the 

 broad 100 fathom plateau and this is twice the depth of the north- 

 east course. 



It would seem that the northeast course was a river valley of 

 earlier date than the southern part of the southeast channel, that the 

 river abandoned it for sufficient cause, possibly change in submarine 

 level or blockage by a heavy ice sheet, and then continued to erode 

 its present buried channel to still greater depths. 



The courses of existing submarine currents over this region are 

 not yet sufficiently determined to permit us to speak definitely re- 

 garding the outpush of the waters through the southeast channel 

 and yet it is practically certain that this is the predominant trend of 

 the major deep water movements of the gulf. 



The Gulf of St Lawrence thus owes its existence chiefly to two 

 determinant factors of very ancient date : the breakdown of the 

 rocks which produced " Logan's fault " ; and the curvature of the 

 northern orogenic axis which effected a syntaxis or a protrusion of 

 the northern against the southern Appalachian folds. The broken 

 down basin between is a natural and resultant area of rock weakness 

 which has had its short periods of low elevation above the sea, but 

 longer periods of depression. 



