Thomson. — Diastrophic Correlation and Districts in the Notocene. 407 



present to go so far until the principle has been recognized, nor is it neces- 

 sary. For all practical purposes Marshall's Wanganui series is equivalent 

 to Wanganuian, and his Waitaki series to Oamaruian, the types of which 

 are defined. The Wangaloa series is discussed more fully below. 



As regards nomenclature, I have given in my former paper an account 

 of the principles which seem to be necessary for attaining finality in this 

 respect. The earliest-used name for a geological division should be retained 

 if possible. In any case, a name once used should not be later taken up 

 in a different sense. The rocks intended to be covered under a given name 

 should be fully developed in the district from which the name is chosen, 

 although it is not necessary that all the recks developed in the district should 

 be embraced by the name. The last two of these principles are violated by 

 Marshall's use of the term " Oamaru system." This name was previously 

 used in a different sense by Hutton, and is therefore preoccupied. In any 

 case, it is made by Marshall to include large and important series of rocks 

 which are not developed near Oamaru at all. His use of the term is there- 

 fore open to very grave objections, and must be rejected. The names sug- 

 gested by him for his series are not open to such serious objection, but two 

 of them nevertheless violate the principle of priority without any compen- 

 sating advantage. The " Waitaki series " is a new name not before used 

 in any different sense, but the same beds originally were given the name 

 of " Oamaru series " by Hector in 1864, and if the unity of the series is esta- 

 blished this name should be revived. Marshall would no doubt have used 

 it if it had not coincided with the name he had given to the whole system. 

 " Wangaloa series " is a new name, but the same beds have been termed the 

 " Kaitangata series " by Park (1912). " Wanganui series " is presumably 

 equivalent to Hutton's " Wanganui system " and Park's " Wanganuian." 



III. An Age Name foe the " Covering Strata " or " Younger 

 Kock- series" of New Zealand. 



As stated above, there is a succession of beds in different parts of New 

 Zealand which, apart from the controversial question of their conformity 

 or unconformity, have a certain diastrophic unity in that they were laid 

 down between two epochs of major diastrophism. It is desirable for many 

 purposes in New Zealand geology to have a name which will embrace them 

 all, a name which will replace the earlier name of " marginal rocks " used 

 by Park and myself, and the physiographic and structural term of " cover- 

 ing strata," when an age significance is intended. Marshall's name of 

 " Oamaru system " is undesirable for the reason stated above, and for 

 similar reasons it is impossible to find any local name that' is suitable. This 

 is owing to the development of minor diastrophic districts within New 

 Zealand. In the Clarence Valley the rocks in question commence with the 

 Middle Cretaceous and end with some stage of the Oamaruian. In the 

 Waipara district they commence with the Upper Cretaceous and end with 

 the Motunau beds, probably Waitotaran. At Oamaru they are entirely 

 comprehended within the Oamaruian, and at Maharahara within the 

 Wanganuian, and so on. There is no district where the complete sequence 

 is developed. Hence no local name is suitable. 



The systems of the stratigraphical record as established in the Old World 

 are now known to correspond approximately to major diastrophic cycles. 

 Had these divisions been first worked out in New Zealand there is no 

 doubt that the break roughly corresponding to that between the Mesozoic 

 and Tertiary in Europe would have been placed between the Hokonui 

 and the younger rocks, and that corresponding roughly to the break 



