342 Transactions. 



Oamaru— 



Limestone. 



Volcanic grit. 



Tufaceous greensands, calcareous tuff. 

 Waipara- — 



Argillaceous limestone. 



Greensands. 



Grey Marl. 



White sandstone. 



Green sandstone with concretions. 



Sandstones, with Ostrea and Conchothyra. 



Sandstone with lignite. 

 The approximate thickness of the Pareora beds is 500 ft., of the Oamaru 

 beds 150 ft.. and of the Waipara beds about 1,600 ft. 



Unconformities have been put in various places by different authorities, 

 but it appears to me that the beds are physically conformable throughout, 

 the only dislocations being those attributable to volcanic action or to fault- 

 ing or folding movements ; in some places, however, obscurities occur, 

 the elucidation of which may ultimately lead to a revision of this state- 

 ment. I have specially in my mind the absence of the upper limestone 

 over considerable areas. The general lithological nature of the beds indicates 

 that the sea of the region gradually became deeper, the maximum being 

 reached during the deposition of the limestones, after which shallowing 

 succeeded, whether by uplift of the bottom or by aggradation has not been 

 determined. This shallowing was followed by a slight deepening towards 

 the close of the period of deposition, and when the land finally emerged 

 at the close of this cycle of deposition it probably remained permanently 

 above the sea. 



The most striking feature of the beds is the absence of coarse sediments 

 such as would occur were the conditions of the surrounding country, or even 

 the height of the land relative to the basin, at all similar to those now exist- 

 ing. The actual presence of land is proved by the sandy beds and by the 

 lignites, the last-named being also noteworthy as they occur at two distinct 

 horizons. This shows that at least on two occasions shore-lines were near 

 the area. A somewhat interesting constituent of the coal-bearing beds in 

 the Craigieburn Gully (which is a small outlier of the basin across a low pass 

 to the north-east) are rolled fragments of rhyolite. Now, no occurrence of 

 rhyolite in situ has been found inside the basin or nearer than the Rakaia 

 Gorge and the Malvern Hills. Between these localities and Craigieburn, 

 which are nearly twenty miles apart, there lies a continuous ring of moun- 

 tains rising at times to a height of 6,000 ft., and it seems impossible, as 

 noted by Hutton, that these pebbles could be transferred under present 

 conditions of relief. In confirmation of the movements of these pebbles 

 I have recently been given a pebble of rhyolite of similar nature picked up 

 in the bed of a small creek near the outlier of coal in the Acheron River 

 in the Rakaia basin, which has been carried in some similar way. It could 

 not have been carried under the present conditions. Hutton was fully 

 aware of this difficulty, as may be seen from a reference to his report on the 

 Trelissick basin. 



Then, again, if we assume, with Hutton and others, that physical breaks 

 occur, we should expect, were the relief the same as now existing, or if it 

 resembled it to some degree even, that basal conglomerates and other relics 

 of the existence of land should occur in some parts of the basin at the points 



