Thomson. — Geology of Middle Waipara and WeJca Pass District. 407 



He considered that from the Middle Miocene to the Pleistocene differen- 

 tial movements in some part or another of New Zealand were almost 

 constantly in progress, and consequently that a series of local strati 

 graphical breaks exists, no two of which are exactly synchronous, but that 

 in all parts of New Zealand there is a decided unconformity at the base of 

 Hutton's Oamaru system, or series. So far as the facts under discussion are 

 concerned no serious criticism of this scheme can be made, except that the 

 rocks he terms " Lower Miocene," which include the base of the Oamaruian, 

 are probable Eocene. 



Woods (1917) has not proposed any general classification of the yoxmger 

 rocks other than Cretaceous, but speaks of the " Cenomanian overlap " in 

 the Clarentian, and the Senonian transgression in the Piripauan, correlating 

 these two periods of local sea-advance in New Zealand with world-wide 

 transgressions. If these transgressions were considered to result solely from 

 difEerential movements of sea-level their localization in parts of the New 

 Zealand area would have to be ascribed to original differences in relief. As 

 a matter of fact, Woods also admits differential movements of the land- 

 surface, for he postulates an uplift in east Marlborough after the Lower 

 Utatiir (Clarentian) period, since the Middle Utatur beds are not known to 

 be represented there. Woods considers the Amuri limestone as probably 

 Eocene and unconformable to the Cretaceous, and therefore presumably the 

 result of a third transgression. There is, however, no stratigraphical evidence 

 for unconformity below the Amuri limestone either in the Waipara or at 

 Coverham, and the much greater thickness of this rock at Coverham receives 

 no explanation. 



Marshall's Classification. 



Marshall has successfully demonstrated the general fact that the younger 

 rocks in most localities form an accordant series, without important angular 

 unconformities between the various beds, and, further, that the beds in any 

 one locality are those of a sedimentary cycle with progressive characters of 

 depth of deposition towardsthe middle limestone members. He claims for 

 these that they are not merely general facts but universal facts for the New 

 Zealand area ; that there were no differential land-movements during the 

 deposition of the beds ; that the lack of angular unconformities proves the 

 absence of palaeontological disconformities ; that there is only one main 

 limestone in the series in any one locality ; that it was deposited at the 

 period of maximum submergence, and consequently that the limestones are 

 correlative in all areas ; and that the localization of the various beds, or, in 

 other words, the differences between the provinces I have defined above, can 

 be explained solely by overlap on a^surfjace of high relief. All this is claimed 

 in support of his classification of all the yoimger rocks as a completely 

 conformable ensemble in the Oamaru system, ranging in age from Senonian 

 to Pliocene. 



Most of these claims are open to serious criticism! Angular unconformities 

 are rarely seen, but are nevertheless not absent ; while palaeontological 

 disconformities are also present. For instance, in the Kaiwhata River, 

 east Wellington, there is a conglomerate containing boulders of Cretaceous 

 sandstones, greensands, and basalts, similar to those outcropping near by, 

 and also boulders of shell-rock, apparently derived, containing Oamaruian 

 fossils, including Pecten huttoni. The conglomerate has a mudstone matrix 

 and passes up into mudstones. There is obviously an unconformity here 

 between two members of the younger rock-series. Morgan and Henderson 

 have described unconformities in numerous places, and it cannot reasonably 



