424 Transactions. — Geology. 



The rock, it will be seen, is similar in all essentials to that 

 found at Takapuna. (See rock section A, Plate XXII.) 



Note. — The large crystal shown in the section was the 

 only undoubted olivine crystal present. Without this ex- 

 planation the section would seem to belong to a rock rich in 

 olivine. This is not the case. 



The only description of the included fragments of rock in 

 these deposits is that given by Mr. Park, who states that the 

 rock composing the included fragments could not be distin- 

 guished from Mount Eden basalt. It is important to distin- 

 guish at the outset between the megascopic characteristics of 

 the two rocks. The Mount Eden lava is a well-defined basalt, 

 rich in olivine, whereas the rock included in the deposit of 

 grit is an undoubted augite-andesite. In some of the frag- 

 ments from Takapuna ash-beds a very few olivine crystals do 

 occur, but they are much altered, and can only be identified 

 by the aid of the microscope. 



The rocks in the neighbourhood of the grit are much 

 contorted and disturbed. Indeed, this disturbance seems to 

 characterize most of the sedimentary rocks in the immediate 

 vicinity of the volcanic grits. 



The ash-beds here reach a thickness of from 10ft. to 14ft., 

 and can be traced for about 100 yards north. They dip land- 

 wards, or towards the west, at an angle of 15°, and show just 

 before disappearing in the cliff an outcrop approximately hori- 

 zontal. Fine and coarse grits seem to be associated without 

 any obvious method of arrangement, shading into one another 

 without any distinct lines of demarcation. The particles vary 

 from the finest material up to angular or subangular frag- 

 ments 2 in. in diameter. The sandstones and shales here and 

 there thin out and disappear, and the grit shows the irregular 

 arrangement mentioned previously. This thinning-out of the 

 strata is probably another indication of the pressure to which 

 the beds have been subjected. Fossils are here relatively 

 abundant as compared to Cheltenham Beach. 



Both Mr. McKay (I.e.) and Mr. Park (I.e.) assert that 

 these ash-beds are portions of the band seen at Chelten- 

 ham Beach. But no stratigraphical proofs in support 

 of this contention are attempted ; in point of fact, none are 

 available. The Waitemata beds are obviously shallow-water 

 deposits. None of the strata as a rule persist for any great 

 distance. Hence the difficulty of establishing any strati- 

 graphical connection between outcrops separated from each 

 other by a distance of from three to four miles. The proba- 

 bility is, however, that such a connection does exist. 



About a mile further along the beach, at a place called 

 Bed Bluff— the headland being stained by red and brown oxide 

 of iron, suggestive of its volcanic origin — the volcanic grits 



