Gilbert. — Geology of Waikato Heads District. 99 



miles farther south, and classed the beds containing them as Neocomian. 

 The sand-dune area was briefly described by him, and the structure illus- 

 trated by a section across the sand-dunes near the northern end. 



Park (1910) alludes to the dune formation of the sandhills, and further 

 calls attention to the oxidation of the ironsand into hard bands of limonite. 



Cox in 1876 journeyed south along the coast from the mouth of the 

 Waikato River, but so hurriedly that he appears to have failed to observe 

 a conspicuous unconformity in the Tertiary strata at the Kawa Stream 

 (fig. 11) and a less noticeable one at the Waikawau Stream (fig. 9), though 

 in his report he expressed the conviction that an unconformity existed 

 at the base of the beds he called the " Cardita beds," and classed as 

 lowest Eocene in age. 



Hutton (1867) had reported on the same district, and would seem to 

 be misunderstood by Cox (1877, p. 16) when the latter quotes him as 

 classing the Cardita beds with the Waitematas, in which he distinctly 

 says he could find no fossils (1867, p. 16). Cox's report is somewhat 

 confusing. 



One of the most valuable contributions to the knowledge of the geology 

 of Port Waikato district is that by the late E. A. Newell Arber (1917), 

 who allocated the plant-beds of the Mesozoic sequence to the Neocomian. 

 A feature of particular interest is his discovery of leaves of the angio- 

 sperms Artocarpidium Arberi Laur. and Phyllites sp., thought by him to be 

 amongst the earliest dicotyledons yet discovered, and, as Dr. L. Laurent 

 says, " it is hardly possible to attach too much importance to the 

 discoveries." 



Bartrum (1919b) described a fossiliferous bed at the Kawa Creek, some 

 fourteen miles south of Waikato Heads. He published a list of fossils col- 

 lected from the bed, and described six new species discovered there by 

 him (Bartrum, 1919a). 



Almost the only other reference of any importance to the geology of 

 the area studied is one by Bartrum (1917) to the discovery of several 

 types of volcanic rocks in pebbles of conglomerates in the Mesozoic strata.* 



The Coastal Area between Manukau Entrance and Waikato River. 



From the Manukau Harbour to the Waikato River, in a belt averaging 

 five to six miles in width, stretch now deforested hills, which for twenty 

 miles form a straight coast-line of almost continuous cliffs averaging 

 500 ft. to 600 ft. in height, broken only by the narrow valleys of a few 

 streams draining to the west. Immediately behind these hills is a belt 

 of low country bordering the Waiuku Creek, and forming the Akaaka 

 Swamp in the south. East from this belt the land rises gently, forming 

 undulating country of subdued topography, the highest point being the 

 volcanic cone of Pukekohe Hill, some 710 ft. high. 



The characteristic cross-bedding of wind-deposited sands is conspicuous 

 from top to bottom along the fine of cliffs facing the sea (Plate XX, fig. 1). 

 The beds vary in texture from a fine to a fairly coarse sand, and many 

 consist of a large proportion of magnetite with grains of feldspar and some 

 quartz. Certain very fine beds appear to be pumiceous. The contained 

 magnetite has been oxidized to the brownish hydrated oxide of iron 



* Whilst this was in press reference to the geology of the district appeared in 

 a report by Dr. J. Henderson on the Huntly Subdivision, which was published in 

 14th Ann. Rep. N.Z. Geol. Surv., 1920, and distributed early in 1921. 



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