340 Transactions. 



• 



continued erosion. He makes no statement as regards the condition of 

 deposition from which one could conclude that the land-surface was even 

 approximately resembling that which exists now. 



The strongest supporter of the theory that these beds were laid down 

 in pre-Cretaceous-formed inlets is Captain Hutton, for he nowhere expresses 

 any doubt as to their origin. The only exception to this statement is in 

 connection with the Hanmer Plains, which he attributed to a local sub- 

 sidence, and not due to the erosive action of gla'ciers (Geological Reports 

 lor 1874, p. 54). In the same report he accounted for the formation of 

 the Hurunui Plains by the erosive action of the sea on beds which were 

 relatively weak. He attributed at one time the basins at Wharekuri and 

 at Castle Hill to erosion of glaciers, but he afterwards abandoned this idea. 

 His most definite statements, however, are made in his paper on the " Origin 

 of the New Zealand Fauna and Flora,'' which appeared in the Annals and 

 Magazine of Natural History. He there maintains (page -91) that the erosion 

 of our mountain valleys such as the Rakaia was more profound in pre- 

 Cretaceous times that at present, and that the patches of Tertiary rocks 

 were formed in them when they were inlets of the sea. i\gain (Trans. N.Z. 

 Inst., 1886, p. 411), he attributes the formation of the Trelissick basin to a 

 pre-Cretaceous river, not to glacier erosion, and suggested that the sea 

 entered the basin not by way of the Rakaia and the Acheron River, but 

 by the Waimakariri and Craigieburn. 



In vol. 43 of the ' ; Transactions of the New Zealand Institute " (1911) 

 there is a paper by Henderson on " The Genesis of the Surface Forms and 

 Present Drainage-systems of West Nelson," which has some bearing on 

 the question, since the author refers therein, to the whole mountain region of 

 the South Island. The arguments are somewhat difficult to follow, since 

 all the grounds on which the conclusions are based are not fully stated, 

 but the author evidently regards the Cretaceous and Tertiary deposits of 

 the restricted area which he describes as having been laid down in rift 

 valleys. He says (page 312), " The land seems to have been above sea- 

 level till Tertiarv times, when depression permitted the inroads of the sea 

 into rift valleys which had already been formed. Deposits accumulated 

 in these rift vallejs. . . . When these last [limestones] were formed 

 the land-surface of what is now west Nelson was represented by a series 

 of base-levelled islands ; to the east what is now the long line of the alpine 

 peneplain rose from the shallow sea. Elevation now took place." 



According to this statement, Henderson evidently regarded the lime- 

 stone as laid down in rift valleys, but that the land was gradually reduced 

 to the peneplain form, and the absence of detrital sediments in the lime- 

 stones was due to the low relief of the land. He further suggested that the 

 elevation which succeeded the deposition was differential, that blocks were 

 elevated unevenly, and that the pre-Tertiary lines of fault again became 

 active. 



The question of the origin of these intermontane basins is discussed 

 very briefly by Kitson and Thiele in a contribution to the Geographical 

 Journal of the year 1910, dealing with the origin of the Upper Waitaki 

 basin. Their conclusions are thus stated :— 



The past geological history of the lake region in general of the Soutl 

 Island is probably as follows :~— 



1. Middle Mesozoic alpine folding, accompanied by fracturing,, probably 

 of a radial character. Some faulting along these lines. 



