Speight. — The Intermontane Basin* of Canterbury, 345 



(1.) That land existed in the neighbourhood of the area at the beginning 

 of the period of deposition, and that it also existed subsequently, although 

 on some occasions the sea grew deeper. 



(2.) That the land did not supply coarse sediments, and probably was 

 of low relief. 



(3.) That it was different in form from that now existing. 



(4.) That the rocks of the basin have been subjected to faulting and 

 folding. 



(5.) That the Tertiary sediments are the remains of a once much more 

 widely extended sheet. 



(6.) That the general character of the beds and their structural features 

 are those which might arise if the beds had been laid down on an old pene- 

 plain or plain of marine denudation, and that certain areas had been subject 

 to either faulting or folding movements which depressed them below the 

 level of this old surface, and that when elevation of the land took place 

 these deposits occupied the basins of relatively less height far below the 

 general level of the mountains. 



(7.) This surface has been dissected by stream and glacier action as 

 well as by other denuding agents, and the relatively weaker beds have only 

 been preserved where the form of the ground sheltered them from these 

 destructive agencies. 



Rakaia Vallev. 



In the main Rakaia Valley there are five outliers of the Tertiary beds if we 

 neglect those in the valley of the Cameron River and near Lake Heron, which 

 belong more properly to the Upper Ashburton and Rangitata occurrences. 

 The former include coal-measures at the Acheron River, at Mount Algidus, 

 at the Rakaia Gorge, all of winch are now without limestone. These and 

 the overlying sandy beds with shell-remains, similar to those in the Trelissick 

 basin, are, hoAvever, preserved at Redcliff Gully, where, owing to their position, 

 they have been out of the line of action of the ice-stream which once operated 

 in the Rakaia Valley. Similar beds are also exposed at the Curiosity Shop, 

 where the river has cut through the gravel of the plains about three miles 

 below the gorge itself. These isolated fragments, occurring as they do in 

 widely separated parts of that valley, are probably remnants of a sheet 

 which once occupied it completely. They do not, however, furnish much 

 evidence as to the circumstances of their deposition, the lower exposed 

 members of the series being sands or clays, with the exception that at the 

 Rakaia Gorge there are fairly coarse conglomerates, composed chiefly of 

 fragments of rhyolite, similar to that which lies underneath the Tertiary 

 series and forms the volcanoes of the Rockwood Hills and their various 

 extensions. In the Redcliff Gully the beds have been subjected to faulting 

 and folding of an intensity similar to that in the Trelissick basin. The 

 limestone also has been elevated, till it now exists at a height of 3,700 ft. 

 above the sea. 



Ashbttrton-Raxgi'tata Region. 



There are in this district two areas which may be designated inter- 

 montane basins. These are the Lake Heron Valley, which extends from the 

 vicinity of Lake Heron across the middle course of the South Ashburton 

 River, and is bounded on the north-west by the high country stretching 

 from Mount Arrowsmith, and on the south-east by the range which extends 

 from the Rakaia River towards the Ashburton, and includes the following 



