Thomsox. — Flint-lifds axaoriafed irifli Ainiiri L/iufxfnne. 57 



difficult to formulate any other hypothesis for theii- origin, while there 

 are other groups of rocks the formation of which can also most easily be 

 explained by the adoption of such an hypothesis. The Amuri limestone 

 itself appears to be in large part a chemical deposit, and its silica-content 

 and its poverty in fossils becomes then easily explicable. The Senonian 

 sulphur sands and mudstones of Amuri Blufi and the Waipara district are 

 certainly the kind of deposits to be expected not far from the margins of 

 a sea with a foul bottom. 



It is quite possible that the sea in which the Amuri limestone and the 

 underlying rocks were deposited was more or less enclosed, for although 

 Marshall, Speight, and Cotton (1911) considered that after the close of the 

 post- Jurassic folding a shore-line ran in a north-east direction from New- 

 Zealand to New Caledonia, recent work by Cotton and by the officers of 

 the Geological Survey on the West Coast has abundantly demonstrated 

 that the present trend of the mountains of the north part of the South 

 Island is due not to original folding in the directions of their present trends, 

 mainly north-east and south-west, but to post-Oamaruian block-faulting. 

 Older rocks similar to those forming these ranges outcrop in the Chatham 

 Islands, and the presence of Oamaruian sediments in these islands suggests 

 that there was a land surface close at hand during Oamaruian times to 

 furnish material for the sediments. Upper Cretaceous rocks have not 

 been recorded from the Chatham Islands, and, should their absence under 

 the Oamaruian rocks be proved, it will establish a considerable degree of 

 probability that there was a land surface there during the Upper Cretaceous. 

 Should this be established, east and west coasts to the Amuri sea will be 

 known to exist. The sediments that mark the northern and southern 

 coasts, if any, are unfortunately below the waters of the ocean. It is not 

 necessary, however, to have an entirely closed sea for the existence of 

 sulphur bacteria in c^uantity, for these are known in foul bottoms in 

 sheltered fiords in Norway and in the Bay of Kiel (Schuchert, 1915). It 

 is, indeed, quite possible that foul bottoms exist in deeps of the open 

 ocean that are cut off from the currents of oxygenating cold polar waters 

 by submarine ridges, and on such bottoms, if they exist, rocks resembling 

 the Amuri limestone must be in course of formation. 



According to the hypothesis here put forward, the sequence of events 

 was somewhat as follows : The Amuri sea was at first restricted in extent 

 so far as the present New Zealand area is concerned, and on its margins 

 it received terrigenous deposits (conglomerates, sandstones, and mudstones) 

 in Cenomanian times. One point of the margin at this epoch is fixed by 

 the coal-beds and fresh-water fossils of Quail Flat, at the upper end of 

 the Middle Clarence Valley. As depression extended the margins, the area 

 of original deposition passed beyond the range of the terrigenous deposits, 

 and the precipitation of flint and dolomite, together with the shower of 

 tests of Foraminifera, built up the lower layers of the Amuri limestone in 

 the area of which Coverham is the centre. During this period — possibly 

 the Turonian — the terrigenous sediments presumably continued on the sea- 

 margins, and should be found, as indicated above, in the Puhipuhi Moun- 

 tains. With further depression the area covered by the limestone increased, 

 but for some reason the deposition of flint, and probably also of dolomite, 

 ceased. During the Senonian the area south of Kaikoura Peninsula ap- 

 parently came under similar conditions, during which the peculiar sulphur 

 sands and mudstones were deposited. Still further depression removed 

 this area also beyond the range of terrigenous deposits, and the limestone 

 between Kaikoura and Oxford was formed between the Senonian and some 



