Speight. — The Older Gravels of North Canterhunj. 281 



Therefore if an unconformity can be proved between the Kowai series and 

 an}" member of the lower series it will be unconformable to all. As the pre- 

 sence of included fragments of limestone in the gravel beds of the Kowai 

 demonstrates the existence of a clear unconformity between the gravels and 

 the limestones, and the undoubted erosion-surface in the Grey River demon- 

 strates the presence of one at a higher level still, we may therefore infer that 

 the gravels of the Kowai series must be of Pleistocene age. If, however, the 

 Cretaceo-Tertiary series is broken up eventually into subordinate unconform- 

 able elements, then this argument fails, and the matter will depend on the 

 relation of the Kowai series to the fossiliferous marine beds of the lower 

 Waipara and the Northern Kowai, as being the highest beds on which the 

 Kowai series undoubtedly rests. The relation of the two sets of beds is 

 somewhat obscure, though, judging from the evidence in the latter locality, 

 probably unconformable. Therefore all that can be definitely stated is 

 that the Kowai series overlies undoubted upper Pliocene beds and must be 

 of a later age, and is most probably Pleistocene. 



This must be earlier than the gravels forming the Canterbury Plains, for 

 these have suffered no deformation by folding movements, whereas the 

 gravels of the KoAvai series are at times folded somewhat acutely. They 

 would therefore antedate the last period of giaciation to which the region had 

 been subjected. 



A point which bears on the conformity of the Tertiary sequence should 

 be noted — viz., that in neither of the two branches of the Grey River are 

 the typical Mount Brown beds developed, thus suggesting an unconformity 

 between the Motunau series, or the Kowai series, and the Mount Brown beds 

 in case the absence is due to erosion, or between the Mount Brown beds and 

 the "grey marls " in case the overlying beds, together with the Mount Brown 

 beds, are part of a conformable series. As there appears to be no evidence 

 of unconformity between the Mount Brown beds and the " grey marls " in 

 the typical locality, whereas there is some evidence of an unconformity 

 between the Motunau series and the Mount Brown beds, it seems more likely 

 that the absence of the Mount Brown facies in the Grey River is due to erosion 

 of these beds after deposition. This, however, is a point which requires 

 further investigation. 



Bibliography. 



Haast, J. VON, 1879. Geology of Canterbury and Westland. 



HtJTTON, F. W., 1877. Re2h Geol. Explor.' during 1873-74, jjp. 27-58. 



1885. Sketch of the Geology of New Zealand, Quart. Journ. Geol. Soc, vol. 41, 



pp. 191-220. 

 McKay, A., 1877. Rep. Geol. Explor. during 1874-76, pp. 172-84. 

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 Speight, R., 1912. A Preliminarv Account of the Lower Waipara Gorge, Trans. 



N.Z. Inst., vol. 44, pp. 221-33. 

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Inst., vol. 46, p. 300. 



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Pass Stone and the Amuri Limestone, Trans. N.Z. Inst., vol. 50, pp. 65-93. 

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