Speight. — Physiography of the Cass District. 149 



The following features are indicative of the former presence of ice : — ■ 



(1.) Morainic Accumulations. — These are well seen on the top of Cass 

 Saddle, in the vicinity of the road ; on the slopes of the hill facing the 

 saddle and leading round to the Waimakariri ; on St. Bernard Saddle ; 

 and at the east end of Lake Sarah, where they are specially well exposed 

 in the railway and road cuttings. There are decided morainic heaps 

 between Lakes Grasmere and Pearson and at the lower end of the latter 

 lake, in this case forming dams behind which the water is ponded, 

 and in the former causing a diversion of drainage. Similar accumula- 

 tions occur on all the down country in the angle between the Broken and 

 Waimakariri Rivers, especially opposite, the mouth of the Esk River. 

 Near St. Bernard Saddle these accumulations have the nature of a 

 boulder-clay, for fine material is mixed with hard tenacious clay, and 

 the angular fragments are frequently striated, gi^^ng the deposit the 

 character of a ground moraine. 



(2.) Scratched Surfaces. — These are well seen on the hard rocks on the 

 faces fronting the Waimakariri ; on the top of Cass Saddle, where the 

 surfaces have recently been swept clean of the protective covering of loamy 

 clay; on the northern slopes of the Sugarloaf, facing the Cass River, im- 

 mediately above the railway. Disrupted striated pavements can be seen 

 in many places where the rocks have been exposed for considerable time 

 to weathering agencies. 



(3.) Roches Moutomiees.— Almost all the rock ridges in the vicinity of 

 the station exhibit this character. They are elongated in the direction of 

 the movement of the ice-streams, and reduced to elevations with flowing 

 outlines ; some, too, have had their cross-sections narrowed by the lateral 

 corrasion of the streams of ice mo\'ing along them and attacking their 

 sides. As a result of this they frequently present the appearance of a 

 sugarloaf when viewed end-on and of a long ridge when looked at side- 

 ways. Smaller elevations related in character to roches vioutonnees occur 

 on Cass Saddle, where they form a characteristic dimpled surface. An 

 excellent example of a roche moutonnee is the moimd (called Romulus on 

 the map) lying close to the Grasmere homestead. 



(4.) The cross-sections of the vaUeys enumerated above are also evidence 

 of the presence of glaciers. Their features are to be seen most perfectlv 

 in the main valley. We have the even alignment of their sides, rising at 

 a steady angle from the broad flat floor to about the grass-line, and then 

 sloping back at gentler grade ; the absence of overlapping spurs ; the 

 truncation or semi-truncation of spur-ends, such as those on the down- 

 stream side of the Bealey and Hawdon Rivers and Cass Saddle itself ; 

 hanging valleys, such as that in which Andrews Stream lies : all these 

 features, as well as others, indicate clearly that the land suffered a severe 

 glaciation. 



We must regard the area, therefore, as covered with a great sheet of 

 ice, formed from snow in the great collecting-basins at the head of the 

 Waimakariri and its tributaries, and moving down the valley to the east, 

 spreading over the undulating country in the triangle between the Wai- 

 makariri and Broken Rivers, while through it projected as " nunataks " 

 the summits of the Sugarloaf and Mount St. Bernard. 



The volume of this flow may be judged from the size of the cross- 

 section of the main Waimakariri Valley above its junction with the 

 Hawdon and the Cass. Half-way between this point and the Bealey Town- 

 ship the floor is over two miles in width, and this breadth is continued 



