THE GEOLOGY OF NEW ZEALAND g 



at different times, and the highest beds in one province may not be 

 coeval with those in an adjacent province. There is no need to 

 consider that any unconformities or disconformities of a general 

 nature are present, though local breaks may occur. Thomson 

 has, moreover, suggested the convenient term "Notocene" (the 

 "Southern New" formation) to indicate the whole group of sedi- 

 ments laid down between the Lower Cretaceous orogenic period 

 and that which, occurring possibly at the close of Pliocene time, 

 ushered in the present physiographic cycle. 



The areal work of the ofhcers of the Geological Survey has 

 given rise to the second conception. Block-faulting and tilting 

 of the crust, which was so extensive a process of the post-Notocene 



Fig. 3. — Diagram illustrating the conception of a general but deceptive conformity 

 obscuring an erosion-interval in the deposition of "Notocene" rocks. 



(Pleistocene?) orogeny, was not confined thereto, but occurred 

 at intervals from Middle Cretaceous times onward. The move- 

 ments were chiefly vertical, but along fault-planes the strata may 

 be much crushed or upturned. Erosion proceeded pari passu 

 with elevation, and the beds laid dpwn after such movements may 

 rest with apparently perfect conformity on the undisturbed areas, 

 but with small or great unconformity where lying on the eroded 

 surface of a tilted block, or near a fault-plane, or they may cross, 

 without disturbance a zone of fault-breccias in the underlying 

 Lower Notocene rocks (Fig. 3). If these two conceptions be 

 admissible, we have the explanation of much apparent conflict of 

 evidence seen when we attempt to correlate the stratigraphi- 

 cal succession in various regions. We must also note that such 

 generaHzations as are in the columnar statement on the map 

 herewith must be subject to modification in detailed application 

 to special areas. 



