HuTTON. — Geology of the Trelissick Basin. 411 



crosses, close to faults ; or else in places where landslips have 

 evidently taken place. There is no stratigraphical evidence of 

 folding by lateral pressure of a general character, involving the 

 palfBOzoic rocks ; and if the tertiary rocks had been folded by 

 compression they would have been to some extent altered by 

 the heat and pressure, as are the eocene and miocene rocks of 

 the Swiss Alps and the Himalaya. Here, however, the tertiary 

 rocks are quite like their equivalents on the plains and at 

 Oamaru. 



With the Waipara System some folding may have occurred, 

 but I think the evidence is not much in favour of it. The steep 

 dips at Parapet Rock and in the Broken River near Sugarloaf 

 are no doubt due to the fault which crosses at both places. In 

 the lower part of Whitewater Creek we find dips varying from 

 45° to 70°, but these may be owing to subsidence of the volcano 

 which burst through them in the Oamaru period. At the Hog's 

 Back true folding may have occurred ; although even here the 

 steep syncline at the south end may have been formed in con- 

 nection with the fault ; indeed, it looks much as if it had 

 been squeezed together between two faults (PI. XXV., fig. 2). 

 But this movement, whatever may have been its cause, took 

 place before the deposition of the Pareora System, which rests 

 at a slight angle upon the upturned edges of the Amuri hme- 

 stone. 



The valley in which the Trelissick Basin lies evidently owes 

 its origin to a pre-cretaceous river, which ran in a northerly 

 direction from Coleridge Creek to Craigieburu, and joined the 

 Waimakariri. But the question arises : Was the present rock- 

 basin, in which the Waipara and younger rocks lie, hollowed 

 out by a glacier ? Or is it due to unequal movements of lava ? 

 I was formerly of opinion that it had been hollowed out by a 

 pre-tertiary glacier coming from the Waimakariri and emptying 

 down the Acheron into the Rakaia ; but I have now abandoned 

 this idea, partly because of the great fall between Craigieburn 

 Saddle and Lake Pearson, but chiefly on account of the discovery 

 of pebbles of liparite at Craigieburn, which could hardly have 

 been brought from the Malvern Hills if a lake had lain in the 

 way. It now seems to me more probable that the northern 

 part of the valley was elevated more than the southern part, 

 during the elevation that followed the deposition of the Pareora 

 marine strata ; for such an unequal elevation would account for 

 all three rock systems being now found at higher elevations in 

 the northern than in the southern end of the basin, notwith- 

 standing the northerly downthrow of two of the faults. This 

 greater elevation of the northern or lower part of the valley 

 would throw the drainage of the basin over the low eastern rim, 

 and the present gorge of the Broken River would then be cut. 

 This would have occurred during, or after, the last great glacier 



