Park. — On the Geology of North Head, Waikouaiti. 423 



The leaf bed thins out toward the westward, and dis- 

 appears altogether some yards before a point below the trig, 

 is reached. The material composing this bed consists of 

 excessively fine grey pumice sand or silt, in which occur 

 numerous inclusions of grey pumice, occurring in rounded 

 fragments, seldom exceeding 2 in. in diameter, but generally 

 under lin. This is interesting as the first discovery of 

 bedded pumice in any part of the South Island of New Zea- 

 land. 



The leaf-impressions are numerous and not well preserved. 

 They include what appear to be representatives of beech, 

 myrtle, oak, elm, and some ferns. The leaf bed is the lowest 

 member of the series, and is overlain by a bed of coarse 

 gravel of variable thickness, which can be traced continuously 

 from one end of the escarpment to the other. The gravels 

 consist principally of pebbles and boulders of basanite and 

 phonolite. 



The basanite is blackish-green in colour, fine-grained in 

 texture, and shows conspicuous crystals and grains of nephe- 

 line. When examined in polarised light it is found to be 

 principally an aggregate of plagioclase, augite, olivine, and 

 nepheline. The base is greyish-blue in colour, not abundant, 

 and crowded with small laths and microlites of feldspar. The 

 augite and olivine occur in large well-developed phenocrysts. 

 The olivine is generally much altered and serpentinised. The 

 nepheline occurs in large gra.ins and in crystals often imper- 

 fectly developed. A little sanidine, biotite, apatite, and mag- 

 netite are present. In many places the rock is tinged red 

 with iron-peroxide, evidently due to the oxidation of mag- 

 netite. 



About 15 yards south of the trig, station the leaf-bed 

 series and the underlying sandstones are traversed by a 

 fault which hades to the south at an angle of about 45". The 

 vertical displacement of the beds caused by this fault is 

 about 40 ft. 



Two minor faults with a displacement under 10 ft. can be 

 traced indistinctly on the seaward side of the escarpment, 

 near the outer rim of the basalt-flow. 



Basalt-flow. 

 The summit of the hill is occupied by a flow of basalt 

 which is probably a remnant of the flow which crowns the 

 summits of Mount Eoyal, Mount Mackenzie, Mount Watkins, 

 Derdan Hill, and other prominent elevations in the neighbour- 

 hood. These isolated patches are all that now remain of the 

 basalt plateau that formerly extended from the Shag Valley 

 southward to Waitati, and from the schistose mountains on. 

 the west eastward to the sea. 



