Marshall and Murdoch. — Tertiary Rocks near Hawera. 89 



on any such correlation. On the other hand, the Oastlecliff series contains 

 a fauna with such a high percentage of Recent species that it is in all 

 probability more or less equivalent to the Upper Pliocene of Europe. 

 While we think that the extreme faunas show as great a difference as is 

 indicated by these periods, we also think that, divergent as they are, a 

 complete transition occurs in the strata between them from the one fauna 

 to the other. 



This opinion as to the continuity of the rock -series is also strongly 

 supported by stratigraphical evidence ; which may be summarized under 

 three heads : — 



(a.) We can nowhere find an important stratigraphical break in the 

 line of cliffs, which is almost continuous throughout the distance. There 

 is, of course, a great deal of irregularity in the stratification, due to 

 tidal scour and to current-bedding, but the cause and nature of this is 

 at once apparent. The only place where we have found anything more 

 important is at a locality about two miles and a half to the north of Kai Iwi. 

 In this place, as mentioned in a previous paper, there is clearly an old land- 

 surface, which is indicated by a thin deposit of beach-worn pebbles, a layer 

 of carbonaceous matter, strata penetrated by roots, and borings of littoral 

 mollusca. On the other hand, this structure is not associated with any 

 distinct change in the species of mollusca, and it must, in our opinion, be 

 regarded as due to a merely temporary and local emergence of a coast- 

 line that was otherwise undergoing a submergence about as rapid as the 

 accumulation of sediment for a long period of time. 



(b.) We have found no sudden change of dip and strike that has 

 extended through a thickness of more than 100 ft. of sediment. Through- 

 out the strata that are exposed on the coast-line the strike and dip are 

 remarkably constant. The strike swings round gradually from 85° at 

 Castlecliff to 125° near Whakino, but, except for a few local variations, 

 there is no sudden change. Perhaps the most marked of these sudden 

 variations is that which occurs at the mouth of the Waipipi Stream, but 

 in a few hundred yards along the beach the normal strike is restored. 



(c.) Lithologically the sediments are very similar throughout. In 

 those few localities where there are embedded pebbles they are always 

 fragments of submetamorphic rocks of the nature of greywackes. Where 

 the sediments are of a finer nature they are always bluish-grey in colour, 

 and contain a great abundance of quartz and of muscovite mica. The 

 lithological nature of this fine sediment is so similar throughout that there 

 is little doubt that it has all been derived from one and the same source. 

 This conclusion points to the probability that the sediments were all 

 deposited while the areas of land and sea remained approximately the 

 same, and consequently there is a presumption that all the sediments were 

 deposited during the same geological period. 



It may therefore be taken as a fact that palaeontological, stratigraphical, 

 and lithological evidence alike support the belief that the series of rocks 

 exposed on the coast-line between Wanganui and Hawera represents a period 

 of continuous sedimentation which in New Zealand geology may be said 

 to belong to the upper part of that great geological system which we, by 

 somewhat extending the classification of Captain Hutton. have called the 

 Oamaru system. We are of opinion that the Wanganui system must 

 now be regarded as having lost its individuality, and that it must in future 

 be looked upon as the upper strata of the great Oamaru system. We 

 consider it possible that the period of deposition of these rocks extended 



