162 Hausman — Glacial Modification of Drainage 



Creek Terminal Moraine at I (fig. 2) cannot be less than 

 100 feet. There is warrant for concluding, as will be 

 shown later, that the slope of the rock floor from Van 

 Pelt's to the region of the abrupt turning point of West 

 Sixmile (D, fig. 2) is downwards. If this be true the 

 depth of the Moss Creek Terminal Moraine must be taken 

 to be much greater than has been postulated above. 

 Half a mile due south of the point where the road reaches 

 its greatest elevation on the summit of the Moss Creek 

 Moraine there lies a small swamp (E, fig. 2). Near this 

 point Gravel Creek has penetrated to its greatest depth 

 into the drift filling of the valley, a depth of approxi- 

 mately 80 feet, without arriving at bed rock. Neither 

 here nor in any other part of its course has this stream 

 been able to remove the moraine to a depth sufficient to 

 disclose the rock bottom of the old preglacial valley. It 

 is apparently a creek that has come into possession of a 

 valley in the early mature stage of development (the 

 product of erosion by a much larger and more vigorous 

 stream) obstructed by a complexus of glacial moraine 

 fillings. 



The position of the moraines, ridges, and loops in the 

 Gravel Creek and Sixmile Valleys indicates that the ice 

 front at its earliest and longest halt in this region stood 

 in the position indicated in fig. 8. Evidence that the ice 

 occupied this position is furnished by the uppermost 

 series of marginal channels on the southern slopes of 

 Davies Hill (N, X, and Y, fig. 3), described by Rich, 

 and it is possible that these served as outlets for the 

 escape of the water of East and West Sixmile Creeks 

 which at that time no doubt flowed against the ice barrier 

 from the north. 



It was apparently only after the ice front had retreated 

 to a position just to the south of the present course of 

 West Sixmile that the creek discovered the lowest por- 

 tion of the Moss Creek Moraine and began to erode its 

 present channel into it. In some localities the course of 

 this early stream across the irregularities of the moraine 

 may have been determined by the position of the ice 

 front, which, forming one of its banks, forced it to 

 become, locally and temporarily, a marginal stream. Its 

 volume may have been much greater then than now, for 

 it seems not unreasonable to suppose that it was aug- 

 mented by water from the melting ice toward the north, 



