Speight. — The Intermontane Basins of Canterbury. 



343 



where discordance occurred 

 fragments of them should 





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. The limestones are of a resistant nature, and 

 certainly appear in the overlying beds. Their 

 absence furnishes either strong probability 

 of the continuous deposition of sediments 

 in the area or positive proof that the relief 

 of the land relative to the basin was far 

 different from that existing now. So that 

 one at least of Hutton's hypotheses appears 

 to be untenable. 



The structural evidence is also somewhat 

 important. There is definite proof that the 

 rocks of the area have been subjected to 

 decided folding movements, the general result 

 being analogous to what would happen were 

 a layer of plastic clay placed flat on the 

 palm of the hand and the palm closed 

 slightly. The harder and more resistant 

 limestones show this admirably, faulting, 

 both normal and reversed, the latter ex- 

 hibiting decidedly flat fault surfaces, and 

 overturned folds show the intensity of the 

 ^ lateral pressure. This is clearly seen on 

 the western side of the area, between the 

 upper part of Broken River and the Hog's 

 Back Creek, but especially so in the country 

 between the latter and Waterfall Creek. 

 Where the limestone band crosses Broken 

 River, about a mile above the ford on the 

 road, it has been tilted till it stands almost 

 vertically, and a portion has been displaced 

 towards the centre of the basin relatively 

 to the lower member, the plane of rupture 

 being almost horizontal. Farther up the 

 river the line of outcrop of the limestone 

 takes the form of a letter S, and in the deep, 

 narrow, precipitous gorge of Waterfall Creek 

 there are several small faults at points 

 where the strain was probably the greatest 

 when the folding took place. In the Hog's 

 Back Creek the limestone is slightly over- 

 turned, but on following the outcrop north 

 the dip slowly diminishes till it becomes a 

 moderate one to the west when the Water- 

 fall Creek is reached (see accompanying- 

 section). It must be noted that the inter- 

 pretation of the structure, advanced by 

 Hutton on hearsay evidence as to the 

 locality, is not borne out on a closer exami- 

 nation on the spot. Farther south in the 

 basin, in the upper portion of Whitewater 

 Creek, there is a detached mass of lime- 

 stone, dipping to the west, whose presence 

 can only be explained by supposing that 

 a fault has been run along the western 



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