148 Transactions 



A striking character of the area is the arrangement of parallel valleys 

 which lie in between the Craigieburn Range and the forest-covered moun- 

 tains to the north of the Waimakariri. These are, starting from the north 

 — (1) The main Waimakariri Valley ; (2) the valley in which lies Lake Sarah, 

 and which continues down Sloven's Creek ; and (3) the valley in which lie 

 Lakes Grasmere and Pearson, with an extension down Winding Creek 

 towards Broken Eiver. It is probable that these valleys are of structural 

 origin, and are formed by faults VN'hich run in a N.W.-S.E. direction. It 

 is certain that the lower portions of Sloven's Creek and Winding Creek 

 have their directions determined in this way; but it is quite uncertain how 

 far these movements extended to the north, and they may have died out 

 before the heads of the valleys were reached, and therefore in their upper 

 portions the formation of the valleys may be attributable almost entirely 

 to water-action. There does not appear to be any evidence that faulting 

 determined the initial location of the Waimakariri Valley, although it may 

 have done so. 



We may take it, then, that before the commencement of the glaciation 

 the drainage directions were as follows : First, there was the main Wai- 

 makariri Valley, bounded on the south by the interrupted range of hills 

 of which the Sugarloaf and the ridge stretching behind the present Craigie- 

 burn Station are parts. Secondly, there was the valley in which lie the 

 biological station itself. Lake Sarah, the St. Bernard Saddle (where it is 

 partially blocked by moraine), and the upper part of Sloven'-s Creek. This 

 valley is bounded on iho. west by the somewhat discontinuous ridges 

 extending from the vicinity of the Cass Railway-station in a southerly 

 direction towards Mount St. Bernard, and continued after a break 

 towards Broken River through the No Man's Land. Thirdly, there is 

 the valley farther west, which contains Lakes Grasmere and Pearson; the 

 valley in which Winding Creek lies may be regarded as an extension 

 of this. In my opinion, then, before the country was glaciated these 

 represented the main drainage-directions. In all probability the ridge 

 extending through Mounts Misery and Horrible, between the heads of 

 the latter two valleys and the Waimakariri Valley towards the Bealey, 

 was in a much more complete condition, and there was no gap through 

 which the present Cass River flows towards the main river ; and the 

 Cass River did not' exist as siich, but probably only as a small stream 

 which rose somewhere near its present site and ran past the Grasmere 

 Station directly into the Grasmere-Pearson Valley. The existing valley 

 of the Cass is, therefore, of more recent formation, and represents the 

 captured headwaters of the streams which discharged into the two westerly 

 of the valleys. The reason for this capture will be given later. The remark- 

 able straight alignment of the sides of the Upper Cass Valley to the west of 

 the Grasmere Station suggests a fault origin for it, but it is more likely due 

 to the erosive action of the ice straightening the walls by the removal of 

 projecting spurs, the marked contrast between a stream-valley with its 

 overlapping spurs and the glaciated portion without them being excellently 

 illustrated by a comparison between the lower levels just above the river 

 and th.Q upper debris-covered slopes. Whatever the reason for the straight 

 alignment of the upper slopes, the actual channel of the river has been 

 determined by water erosion alone. (See Plate XV, fig. L) 



The changes in the direction of drainage in this locality can be attributed 

 almost entirely to the disturbing effects of glaciation, and it may be useful 

 to summarize at this stage the evidence for the former presence of glaciers. 



