H.—34.

SPECIAL REPORTS. 1. TE KUITI SUBDIVISION. (By H. T. Feebae.) Introduction. During the past field season the geological survey of the Te Kuiti Subdivision was continued in such a way as to link up districts, that previously had been mapped, with the isolated areas east of the railway specially surveyed last season on account of the Mineral Content of Pastures Research Committee (see last year's annual report). As soon as these special areas had been connected with earlier work the survey was continued systematically. Field-work was resumed on the 11th November, 1930, near Waimiha, at the north-east corner of the Tongaporutu-Ohura Subdivision (see N.Z. Geol. Survey Bull. No. 31), and was carried northward over Pahi, Pakaumanu, and Mangaorongo Survey Districts to the southern boundary of the already mapped Puniu Survey District of the HuntlyKawhia Subdivision (see Bull. No. 28). Work at Otorohanga was suspended on the 31st May, 1931, after 335 square miles had been mapped. GrENEBAL GrEOLOGY. The area surveyed contains three distinct rock-formations—namely, distorted conglomerate, sandstone, and claystone beds of Triassic age; almost horizontally bedded limestones and sandstones of Tertiary age ; and a thick but dissected sheet of consolidated rhyolitic tuff erupted in late Pliocene or early Pleistocene times. The Triassic rocks are littoral deposits that occur as fault-blocks uplifted independently of their internal structure. These rocks so resemble the oft-described greywackes that form the elongate mountain-ranges of the Dominion that no further description is necessary here. The Tertiary sediments are likewise marine deposits which rest with marked unconformity on the greywackes. They are an extension eastward of the Te Kuiti, Mahoenui, and Mokau beds described in former reports on adjacent areas. The occurrence of infaulted Tertiary beds in the Owawenga valley in Pakaumanu Survey District shows that an important line of structural weakness passes through the district. During late Pliocene and Pleistocene times earth-movements caused fissures to open in the basement rocks, through which vast quantities of rhyolitic tuff were ejected. At Ngahape there is a small flow of basalt. The rhyolitic material, like that ejected at Katmai in Alaska, shows no distinct craters, and was probably erupted through a number of vents, not one of which has as yet been located. The now consolidated material forms tablelands, fills depressions between block mountains and spreads out on the Waikato lowlands. The tuff usually contains angular fragments of obsidian and pumice, which, being hot and sticky when ejected, adhered to form a massive rock. In some places the tuff is bedded and contains waterworn boulders of pumice and occasionally of greywacke, as if deposited from an aqueous slurry ; in other places it has given rise to lacustrine clays. In some places it is an incoherent sand that, when deposited, was warm enough to slide off hillsides and " flow " along valleys ; in other places there is abundant dune material. Normal terrestrial conditions followed the eruption of the tuff. The once uniform sheet was dissected, and gravels, sands, and clays derived from it were deposited in patches. Subsequent disintegration and weathering of rhyolitic material has given rise to white, yellow, and brown earths of inconstant thickness, above which a thin covering of recent pumiceous ash (Taupo pumice) is conspicuous. Synopsis oe Mineeal Resources. The district under review has been subjected to igneous activity and earth-movements which are usually the immediate prelude to primary mineralization, but in the present case no minerals of high intrinsic value have made their appearance, although the presence of gold and mineral oil has been reported from time to time. Vulcanism, however, has supplied vast quantities of rhyolitic tuff suitable for constructional purposes, and of white pumice sands that can be used for making pumice concrete should such material bo required for towns liable to earthquake shocks. The rhyolitic tuff is easily quarried, and there are great masses of this rock close to the railway between Waimiha and Puketutu railway-stations. Coal-seams were found in three localities, but only one —namely, that near Tahaia —is worth working ; its prospective value is small. High-grade limestone is scarce in the area just surveyed. Soil and subsoil profiles were examined in order to establish a basis for their classification in terms of full profile, and an attempt was made to trace a connection between the soils and the incidence of debility in stock. 2. EKETAHUNA SUBDIVISION. (By M. Ongley and J. H. Williamson.) The Eketahuna Subdivision extends along the east coast of the North Island from eight miles north of Cape Turnagain to four miles south of Castle Point and reaches inland fifty miles to the Tararua Range. Inflammable gas issues from the ground in several places, and some of the rocks smell of oil, indicating that payable oil may occur. Much money has been spent, without success, in trying to produce oil, and it is expected that a geological examination will help.

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