Mulgan. — The Waitemata Series. 



423 



Waitemata series. At this point, however, they present the 

 curious appearance indicated hy the accompanying section 

 (fig. 5). Portions of the volcanic grit outcrop in irregular 

 patches and detached bands on the weathered surface of the 

 cliff in such a way as to suggest at first sight a number of 

 different layers. After a careful investigation of the locality, 

 I am of opinion that only one bed is to be seen, and that 

 the appearance of different bands has resulted from portions 

 of the grit being squeezed in between the softer sandstones 

 and shales. The appearance has been produced subsequent to 

 deposit. This belief is further strengthened by the fact that 

 in places the shales between the grit are arranged in lenticular 

 masses, thinning out and disappearing in the course of 50 or 

 60 vards or even less. 



Fig. 5. 



30' 

 ro 

 4'0 



I SHMfS 



s o Tvj?A r fine /wo 



4 0" "'■'•lUCO/lftit CfilTS 

 V ,6" IS36S COW/Kjr GRIT. 



.5 ) fine c/fiT 



SHALfS 

 COARSE CHIT 

 J>/INDSTON£S 



Appearance of cliff : a. Layers of grit apparently separated by sandstones 

 and shales, b. Grit continuous. Sandstones and shales thinning 

 out. c. Grit appearing in detached masses through softer strata. 



The grit here presents much the same appearance as chat 

 at Parnell and Point Erin, except that in places there are 

 coarser layers with fragments up to f in. in diameter. Scat- 

 tered through the ash-beds are angular and subangular 

 volcanic fragments, some of them being upwards of 12 in. in 

 diameter. These consist of a vesicular lava of augire-andesite 

 showing large augite crystals and numerous amygdules of 

 calcite and the zeolite chabazite. A section made from one 

 of these blocks showed under the microscope a microcrystal- 

 line ground- mass similar to that seen in the Cheltenham 

 Beach section, except that a good deal of it was composed of 

 an altered product— probably chlorite. As in the case of the 

 other section, the porphyritic constituent consisted of large 

 crystals of andesine, ohgoclase, and augite, and a small 

 amount of altered olivine. The feldspars showed broad as 

 well as fine lamellae, and contained numerous inclusions of 

 augite and magnetite. In some of the crystals the curious 

 phenomenon appeared of the direction of extinction being 

 different in different parts of the crystal. The edges and 

 central portions extinguished at different angles, owing to the 

 outer zone being less basic in character. Large and small 

 augite crystals were numerous, and many of the former 

 showed well-marked crystalline form. Specific gravity, 2-7. 



