410 Transactions. 



DIASTROPHIC HISTORY OF THE EAST COAST OF THE SOUTH ISLAND. 



Althougli my proposal of the term *' Notocene " was made before all 

 the facts brought out in this paper were known to me, the reasons which 

 I advanced for this grouping of, the yomiger rocks were stated in terms 

 sufficiently general to admit of considerable latitude in detail, and the new 

 facts do not in any way invalidate the usefulness of the grouping. All 

 the Notocene rocks in the three provinces in the eastern part of the South 

 Island Vere deposited between the two eras of major (mountain-building) 

 diastrophism, the post-Hokonui (early Cretaceous) and Kaikoura (late 

 Pliocene or pleistocene) orogenic movements. That the intervening period, 

 during which the Notocene rocks were deposited, was one of relative 

 crustal stability is proved by the general accordance of the Notocene rocks 

 and the absence of planes of acute angular unconformity. Not only was it 

 not claimed that there were no unconformities or disconformities, or that 

 there were not minor diastrophic movements during this period of relative 

 stability, but the existence of the latter, in combination with differential 

 movements of sea-level, was postulated to explain the stratigraphical 

 diversity of the various provinces. • 



An attempt may now be made to analyse more closely the succession 

 of events which gave rise to the main elements of the stratigraphy of 

 the three provinces. That there were world-wide transgressions and 

 regressions of the sea during the period from middle Cretaceous to the 

 present day cannot be doubted, and these must have left their trace in 

 New Zealand. The areas affected by these eustatic movements; however, 

 are . not the same for each movement, consequently there must have been 

 also differential movements of the lithosphere in the Notocene. Moreover, 

 there seems to have been a tendency, up to the close of the Oamaruian 

 at least, for the sea to keep, possession of the area it gained from the land, 

 suggesting that the area was prepared for the transgression by a down- 

 warping movement which continued in the same area from one transgression 

 to another. 



The first transgression, the " Cenomanian overlap," covered' only a part 

 of east Marlborough, now occupied by Clarentian rocks. A subsequent 

 regression is perhaps indicated by the thinning-out of the Amuri limestone 

 towards the old shore-line in the neighbourhood of the Bluff Kiver and 

 Herring River, but in the Coverham area deposition appears to have gone 

 on uninterruptedly ruitil the upper Oamaruian. I formerly suggested 

 that the Clarentian sea gradually enlarged its borders and that the basal 

 Notocene beds in the Puhipuhi Mountains would prove to be intermediate 

 between Clarentian and Piripauan. This hypothesis has not yet been 

 tested. The next transgression, the Piripauan (Senonian), affected a large 

 area between Kaikoura Peninsula and the Rakaia River, attaining its 

 greatest penetration of the present land in the latter neighbourhood. 

 That the surface at this time was still fairly diversified seems to be proved 

 by the overlap of the various Piripauan beds in the Waipara district. 

 The Piripauan sea still covered the area of the Clarentian transgression, 

 there depositing the basal beds of the Amuri limestone, but the^ fresh area 

 gained from the land was considerable. 



The Piripauan rocks are succeeded, apparently without any strati- 

 graphical break, by the Amuri limestone, the deposition of which demands 

 a clear sea of considerable depth. The area occupied by this limestone is, 

 however, closely restricted within that occupied by the Piripauan beds, 

 and there is no overlap over the Piripauan recorded except for the very 

 slight one I have described east of the Weka Pass. Indeed, the Amuri 



