112 Transactions. 



Kawa pumice-bed, above which all the beds are subaerial deposits. (See 

 Cussen, 1889, p. 413.) 



4. It might be suggested that wave transport may have brought the 

 pumice from far-distant localities ; but the nature of the material and its 

 bedding negative such a suggestion. 



It may be mentioned that Mr. Bartrum (1919a, p. 104) similarly is 

 inclined to ascribe the origin of this pumice-bed to the Waikato River. 



Structural Plateau near the Coast. 



The Notopleistocene formations along the coast form a structural plateau 

 governed by the bedding of the horizontal sheet of limonitized sands forming 

 the uppermost beds and now acutely dissected by the westerly streams. 

 The residual ridges between these streams are all about the same height, and, 

 seen from the northerly geodetic station, Waihonui, they are remarkably 

 uniform. These divides are sometimes, as at Waihouni and Opura, small 

 tablelands, remnants of the old platform. 



Slipped Country above Waiwiri Beach. 



For a quarter of a mile back from the Waiwiri beach the country 

 has slipped along parallel lines, presenting seaward-facing scarps 10 ft. to 

 30 ft. or 40 ft. high. The whole area between these scarps and the sea- cliffs 

 is tossed into hummocky mounds. Only the upper or sandy beds appear 

 to be affected, and these are being slowly pushed over the cliffs on to the 

 beach. The scarps form a rude semicircle facing the sea for a distance of 

 over a mile. They are said to be as fresh-looking to-day as they were forty- 

 five years ago. The scarps reveal cross-bedding everywhere. 



The composition of these beds is a light, dull, black sand, the blackness 

 not being due to grains of magnetite, which is not abundant, but to dull, 

 light grains of material probably owing its origin to the erosion of shale-beds 

 of the Mesozoics. They are unlike any of the other beds north or south 

 that occupy a higher horizon than the Cardita beds or tabular limestone. 

 The Cardita beds appear to have formed the base of a plain of marine 

 denudation in this locality, possibly contemporaneous with that at the 

 Kawa, or perhaps more recent, when the yellow and brown sands, &c, 

 were removed by wave-action. 



Sinkholes. 



Close to the ridge above the great area of slipped country are several 

 sinkholes, or swallow-holes, vertical cavities formed by the internal running 

 of the sands beneath the surface, which then subsided. Similar sinkholes 

 can be observed in the pumice lands near Hamilton. One at Pa Brown, 

 due to solution of the limestone beneath the surface, is of much larger 

 dimensions than those between the Ruahine and Kawa Streams. 



Microscopic Characters of some of the Rocks. 



The Kawa Basalt. — In a noncrystalline pilotaxitic groundmass consist- 

 ing of long microlites of feldspar, showing good flow-structure, with less 

 prominent prisms and grains of augite and olivine and very numerous fine 

 specks of magnetite, occur separate phenocrysts of augite and olivine, and 

 some glomero-porphyritic phenocrysts of olivine and augite with associated 

 chlorite. The augite is usually colourless, but sometimes has a pink border. 

 The olivine phenocrysts show the mesh-structure characteristic of alteration 

 to serpentine along lines of fracture and around the edges. A secondary 

 fibrous mineral, chlorite, is formed in numerous cavities. Large olivine 

 nodules, up to 2 in. in diameter, are numerous in this basalt. 



