MINES DEPARTMENT. GEOLOGICAL SURVEY BRANCH [TWENTIETH ANNUAL REPORT (NEW SERIES) OF THE].

Appendix to the Journals of the House of Representatives, 1926 Session I, C-02c

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1926. NEW ZEALAND.

MINES DEPARTMENT. GEOLOGICAL SURVEY BRANCH [TWENTIETH ANNUAL REPORT (NEW SERIES) OF THE].

Laid on the Table of the House of Representatives by Leave.

CONTENTS. PAGE PAGE Letter of Transmittal .. .. .. . . ] Special Reports. Director's Report. 1- Motueka Subdivision (J. Henderson and L. I Grange) 4 Summary of Field Operations . . .. .. 2 2 - Mangakahia Subdivision (H. T. Ferrar) .. 6 Progress of Areal Surveys . . . . .. 2 3. Kaitangata - Green Island Subdivision (M. Ongley) 6 Mangakahia Subdivision .. .. 2 4 > Soil Survey, Central Otago (H. T. Ferrar) .. 8 Dargaville-Rodney Subdivision 2 5 _ Wai Napier, and Raukawa West, Hawke's Bay Waiapu bubdivision .. .. .. ..2 D n \ Tongaporutu-Ohura Subdivision .. .. ..2 (I.U.Morgan) .. .. .. ..9 Egmont Subdivision .. .. .. . . 2 6. Upper Urenui Valley, &e., Taranaki (P. G. Morgan) 10 Motueka Subdivision .. . . .. 2 7. Auriferous Drifts, St. Bathans, Central Otago Kaitangata - Green Island Subdivision .. ..2 (P.G.Morgan) .. .. .. 10 PaLo3ogicrrWork tag ° !! !! V. 3 8. Murchison District, Nelson (P. G. Morgan)' .. 11 Publications and Reports .. .. .. 3 Proposed Tunnel-site, Pegleg Gully, and Dam-site, Office-work, &c. .. .. .. 3 Manuherikia Falls, Central Otago (H. T. Ferrar) 12

LETTER OF TRANSMITTAL. Sib, — , Geological Survey Office, Wellington, 15th June, 1926. I have the honour to forward herewith the twentieth annual report of the Geological Survey Branch of the Mines Department. This report covers the work of the Geological Survey for the twelve months ended 31st May, 1926, this date being chosen on account of the season for field-work ending approximately at that time. In addition to the usual general account of the work done during the year, it contains reports on the districts examined in detail by the field geologists, and various other reports (somewhat abridged) supplied during the year. I have, &c., P. G. Morgan, Director, Geological Survey. The Hon. G. J. Anderson, Minister of Mines, Wellington.

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DIRECTOR'S REPORT. Summary of Field Operations. During the field season of 1925-26 detailed topographical and geological surveys were carried out in the following areas : — (1.) Mangakahia Subdivision, North Auckland, by H. T. Ferrar, M.A., F.G.S., Geologist (during the latter part of November and December 1925 only). (2.) Motueka Subdivision, Nelson, by J. Henderson, M.A., D.Sc., 8.E., A.0.5.M., Mining Geologist, and L. I. Grange, M.Sc., A.0.5.M., F.G.S., Assistant Geologist. (3.) Kaitangata - Green Island Subdivision, by M. Ongley, M.A., B.Sc., Geologist. At the beginning of 1926 Mr. Ferrar, who has had experience in soil surveys in Egypt, was transferred to Central Otago, in order to begin a soil survey on behalf of the Public Works Department. This work, however, remains under the control of the Geological Survey. Visits for various purposes were made by me to several parts of Hawke's Bay, Taranaki, Green Island and other localities near Dunedin, Alexandra, St. Bathans, and Murchison. Dr. J. Marwick, Palaeontologist, visited many localities in northern Hawke's Bay and in the Gisborne - East Cape district in order to collect fossils and obtain general geological data. Mr. H. T. Ferrar, Geologist, made special visits to Pegleg Gully and Manuherikia Falls on behalf of the Public Works Department. Progress of Areal Surveys. During the twelve months ended 31st May, 1926, approximately 777 square miles was geologically examined in detail. Of this area 120 square miles is in North Auckland, 530 square miles in Nelson, and 127 square miles in east Otago. In addition a soil survey of roughly 230 square miles was made in. Central Otago. This work requires geological examination not only of the area mapped but also of the surrounding country. Mangakahia Subdivision. The geological examination of the Dargaville-Rodney Subdivision having been completed, Mr. H. T. Ferrar was transferred to the Mangakahia Subdivision, a large tract of unexplored country lying to the west of the Whangarei - Bay of Islands Subdivision and north of the Dargaville-Rodney Subdivision. The progress made by Mr. Ferrar before he was transferred to Central Otago is described in a later part of this report. Dargaville-Rodney Subdivision. Mr. Ferrar's detailed report on the Dargaville-Rodney Subdivision is in course of preparation. Waiapu Subdivision. During the year geological maps of the Waiapu Subdivision have been printed. The detailed report of Messrs. Ongley and Macpherson is being revised, and will shortly be sent to the printer. Tongaporutu-Ohura Subdivision. Mr. L. I. Grange's detailed report on the Tongaporutu-Ohura Subdivision and his geological maps are nearly ready for the printer. Egmont Subdivision. The detailed report on the Egmont Subdivision (Geological Bulletin No. 29), mentioned in last year's annual report, has been completed, and, together with accompanying maps, is in course of publication. Motueka Subdivision. The survey of the Motueka Subdivision has now been finished, and a detailed report is in course of preparation. In this report the marble deposits of the Pikikiruna Range and other localities will be fully described. A summary of the work done during the past season appears on later pages. Kaitangata - Green Island Subdivision. During the past season Mr. M. Ongley completed the survey of the Green Island coalfield and of adjoining areas. Work was also done in Clarendon, Mangatua, and Waipori survey districts, but the greater part of the latter survey district has yet to be examined in detail before the survey of the subdivision can be considered complete. The work done during the past season is described on pages 6-8,

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Soil Survey, Central Otago. On a later page Mr. Ferrar gives an account of the work done since the soil survey of the areas included in the Public Works irrigation schemes for Central Otago was begun last January. In some localities harmful salts, chiefly sulphates, tend to accumulate on the surface of the soil. So far as my observations went these areas are very small, and confined to places where drainage is bad, or irrigation water has been injudiciously applied. There need be no difficulty in dealing with these areas. Exact measurements of the water supplied to the lands being irrigated, and careful records of the results are very desirable. These matters are no doubt being kept in sight by the irrigation engineers. Work. Dr. J. Marwick, Palaeontologist, reports as follows : —- " During the past year I continued work on the Cretaceous and Tertiary mollusca. Collections made by the field staff were examined and identified, the chief localities being in the Nelson and Taranaki districts. The building-up of a representative collection of foreign mollusca for comparative purposes has been continued. In exchange for New Zealand fossils, the following collections were obtained : Miocene and Pliocene mollusca from Vienna Basin ; Tertiary and Recent Veneridse from the United States ; Recent mollusca from New South Wales. " In November last I visited Wairoa, northern Hawke's Bay, and collected fossils from the seacliffs about a mile west of the river-mouth. The mollusca showed that the rocks here are of Upper Miocene age, and perhaps the equivalent of the Urenui beds of Taranaki. The argillaceous sandstones and shell-beds of the Tongoio and Arapawanui valleys also provided extensive collections. The fauna is the same as that of the Petane-Ngaruroro sandstone, probably of Middle Pliocene age. " I spent five weeks of February and March in the Gisborne district, where the Taranaki Oilfields Company kindly provided travelling facilities. Attention was directed mainly to the Tertiary rocks, and a large number of fossils was collected from them. The chief localities examined were Morere, north end of Mahia Peninsula, Waingake, Waimata, Waipaoa River, Tolaga Bay, Tauwhareparae, Waiau River, and Tokomaru Bay." Publications and Reports. During the year the following official publications were issued : — " Nineteenth Annual Report (New Series) of the Geological Survey " (parliamentary paper C.-2c, 1925). Geological Bulletin No. 27 : " The Geology of the Whangarei - Bay of Islands Subdivision, Kaipara Division," by 11. T. Ferrar. Geological Bulletin No. 28 (" The Geology of the Huntly-Kawhia Subdivision, Pirongia Division "), by J. Henderson and L. I. Grange, is ready to appear, and the printing of Pateontological Bulletins Nos. 11 and 12 is in an advanced state. Geological Bulletin No. 29, " The Geology of the Egmont Subdivision, Taranaki," is also in the press. Several paleeontological papers by Dr. J. Marwick will appear in volume 56 of the " Transactions of the New Zealand Institute," which will very shortly be published. These papers are : " Tertiary and Recent Yolutidse of New Zealand " (pp. 259-303) ; " Myalinidse from the Jurassic of New Zealand " (pp. 304-6) ; " Molluscan Fauna of the Waiarekan Stage of the Oamaru Series " (pp. 307-16) ; and " New Tertiary Mollusca from North Taranaki " (pp. 317-31). " Petroliferous Areas of New Zealand," by P. G. Morgan, was published in the New Zealand Journal of Science and Technology, vol. 7, pp. 287-90 (1925). Several papers on New Zealand geology by the same writer appear in " Proceedings of the Pan-Pacific Science Congress (Australia), 1923," and descriptions of coal-measure sections in the Huntly and Kaitangata districts by J. Henderson and M. Ongley appear in " Proceedings of the Dominion Mining Conference, Dunedin, 1926." Office-work, etc. Throughout the winter and early spring of 1925 the various professional members of the Geological Survey staff were occupied in the preparation of detailed reports and studies connected therewith. During the year numerous requests for geological and other information related to the work of the Geological Survey were answered, and many samples of rocks, minerals, and fossils were examined and identified. Among specimens of interest received were diatomaceous earth from near Kamo, stibnite from Cape Brett district, vivianite from Kawakawa district, manganese ore from Ruapekapeka, inflammable gas from Raukawa West (Hawke's Bay), and phosphatic concretions from Burnside marl-pit. The draughting staff drew six maps (each covering a survey district) and one sheet of sections for photo-lithographic reproduction, besides making numerous additions and corrections to twenty-one other maps drawn in previous years. Twenty field-sheets, fourteen pantagraph reductions, and a number of tracings and small maps were made. The drawing of geological maps of the North and South Islands of New Zealand for the New Zealand and South Seas Exhibition, Dunedin, 1925-26, occupied considerable time. A fault map of New Zealand was also partly prepared. Numerous map-proofs were corrected and coloured, and many other small matters attended to.

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SPECIAL REPORTS. 1. MOTUEKA SUBDIVISION. (By J. Henderson and L. I. Grange.) Introduction. The third season's field-work in the Motueka Subdivision was begun on the 11th November, 1925, and ended on the 29th April, 1926. In all 530 square miles was examined, including the whole of Totaranui, Takaka, Kaiteriteri, and Moutere survey districts, together with parts of Waingaro, Harapaki, Flora, Mount Arthur, Motueka, and Wai-iti survey districts. The season was exceptionally favourable for field-work, and the rugged highlands drained by the Takaka River and its main branch were explored with unexpected despatch. In this part of the work Mr. S. J. H. Sylvester, of Canterbury College, gave able assistance. Physiography and Structure. A great fracture-zone, the Motueka fault of McKay, crosses the subdivision in a north-north-east direction, separating a western relatively elevated crust-block from an eastern depressed area, the northern portion of which is covered by the sea and the southern by gravels. Some of the component faults of this fracture-zone strike north-east, others nearly north. The faults of the uplifted area strike similarly —those of the northern part of the subdivision mostly north, and those farther south mostly north-east. The lower Takaka valley is a narrow trough extending north and south between the Pikikiruna Range on the east and an extensive group of extremely rugged mountains on the west. It is fifteen miles long and from two to four miles wide. The Pikikiruna Range, the broad highland lying between the Takaka trough and Tasman Bay, is an uplifted warped earth-block, the southern portion of which is tilted gently east-south-east and the northern portion east-north-east. The ranges west of the Takaka trough have been carved from a massive plateau tilted east. At its southern end the trough narrows, so that the lower edge of the western plateau approaches the Pikikiruna block and finally abuts against it. The Pikikiruna Range ends in this locality, but the highland continues south-west as the Mount Arthur Range. A prominent fault-angle extends south-west from the southern end of the trough for twenty miles or more along the north-west side of this range. The plateau is warped: the northern part slopes east and the southern part south-east. In several localities its ancient surface is well preserved over considerable areas near the fault, and above it the crests of the Mount Arthur Range rise in abrupt slopes 2,000 ft. to 3,000 ft. or more. Other faults, usually striking north or north-east, traverse the highlands. These, though important, are not so well marked physiographically as the great fracture above described (McKay's Karamea fault). The chief streams of the Pikikiruna Range flow eastward to Tasman Bay, but along the western edge, where calcareous rocks prevail, much water from this range reaches the Takaka trough by way of underground streams. The larger part of the area examined during the. season was in the basin of Takaka River, a stream of which the upper part is in or near the Karamea fault-angle and the lower in the Takaka trough. Its principal tributaries are the Cobb, Waingaro, and Anatoki rivers, flowing from the west. They are consequent streams, their direction having been determined by the initial tilt of the ancient plateau. The headwaters of all are strongly glaciated ; now, though snow-drifts persist at many points through summer and autumn, none of the peaks is above the line of permanent snow. General Geology. Three of the four great series of Palaeozoic sediments mentioned in last annual report as forming a large part of the western highlands occur in the northern part of the subdivision. They are strongly folded, distinctly metamorphosed, and intruded by large masses and dykes of acid and basic igneous rock. They form broad bands which in this part of the subdivision strike north and a little west of north. The beds as a whole dip steeply to the east. In the Pikikiruna Range, where only the rocks of the uppermost of the three series are seen, the structure is irregular. The oldest strata examined during the season outcrop at the heads of the Cobb, Waingaro, and Burgoo rivers, the last a branch of Aorere River. The rocks consist of dark and light-grey phyllites, quartzose greywackes, and quartzites, together with minor bands of dark carbonaceous phyllites, some of which contain graptolites, indicating a Lower Ordovician age. Marble is not present in the section examined, though it occurs in large lenses a little to the south, associated with the carbonaceous phyllites. The beds strike nearly north and south, and dip vertically or a few degrees from the vertical and then predominantly east. These rocks form the upper part of what in the two preceding annual reports was termed the Aorere Series, a name that cannot be consistently used if the view of the stratigraphical succession now held is correct, and must therefore be discarded. Lying to the east of the above-mentioned strata is a vast mass of sedimentary and igneous rocks that extends east for eight miles to the Cobb-Takaka junction. It consists chiefly of quartzites, green greywackes, fine and coarse breccias, breccia-conglomerates and conglomerates, light and dark phyllites containing marble lenses, and chloritic phyllites and schist, these last probably altered fragmental volcanic rocks. Of the numerous outcrops of basic igneous rocks some are intrusive, but many are probably contemporaneous flow rocks. The whole, which constitutes the Haupiri Series of Middle (?) Ordovician age, extends as a broad belt north and south through the western part of Flora and Takaka survey districts and the eastern part of Harapaki and Waingaro survey districts. The beds strike north, and dip in general steeply east. They are strongly folded and much metamorphosed. Their eastern boundary, where resistant schistose greywackes are in contact with the

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weak dark phyllites of the overlying Mount Arthur Series, is along a fault which extends north and north-north-west for at least fourteen miles. The rocks of the Mount Arthur Series, in ascending order, consist of dark phyllites, massive quartzites, and thick bands of marble passing upward into black siliceous phyllites and quartzites. The somewhat poor graptolites found in the phyllites have not yet been examined by any expert, but provisionally the Mount Arthur Series is considered to be of Upper Ordovician age. The west boundary of the series is the simple slightly curved fa'ult above mentioned, and its eastern an intricate contact with intrusive rocks lying eight to twelve miles to the east. The structure of the Mount Arthur beds is extremely irregular, and on the whole they dip much less steeply than the other Palaeozoic rocks. The Tertiary (Oamaruian) strata of the northern part of the subdivision occrr as patches that have escaped denudation along the Karamea fault-angle and in small areas exposed below the gravels in the Takaka trough. Tata Islands and Taupo Peninsula, on the northern shore of Totaranui Survey District, are also formed of Tertiary rocks. In this part of the subdivision the lowest bed is usually a massive limestone that grades upward into a calcareous mudstone followed by argillaceous sandstone and massive sandstone. The limestone rests on a gently undulating surface of Palaeozoic rocks, and at many points contains in its lowest layers rounded pebbles and cobbles of quartzite and siliceous greywacke. Thick arkositic grits with bands of carbonacous shale and a seam or seams of brown coal occur beneath the limestone at Motupipi and in the Takaka Valley not far north of the subdivision. Except close to faults the strata are nearly flat or dip gently. The Moutere gravels form a vast mass of river-gravels occupying the depressed eastern portion of the subdivision. They were deposited after the fault-movements usually regarded as marking the close of the Tertiary had ceased. On the other hand, they are well consolidated and deeply weathered, facts that suggest they belong to the Tertiary rather than to the Pleistocene. The only fossils observed in them were a few silicified tree-trunks exposed in the cliffs on the coast south of Moutere Inlet. The terrace and flood-plain gravels of the Takaka and other streams are the chief younger Pleistocene and Recent deposits of the area examined. There are a few square miles of gravel country at Canaan, on the Pikikiruna highland, some 2,400 ft. above sea-level. This area, which is entirely surrounded by hills of igneous rock or marble, is drained by subterranean streams to the Takaka. Other Pleistocene deposits are the moraines of the mountain-valleys and the much-denuded remnants of a gigantic slip and scree deposit from the marble scarp of the Pikikiruna Range that rests on Tertiary beds near the southern end of the Takaka trough. A great mass of basic igneous rock intruding Mount Arthur sediments extends from the lower valley of Riwaka River south-west for more than twelve miles to the Graham Valley. It varies from a mile and a half to three miles across, and consists for the most part of gabbro grading in places to pyroxenite and in places to basic diorite. Numerous diabase and gabbro dykes at the southern end of the Pikikiruna Range suggest that the igneous mass extends farther north-east but is there concealed by a cap of Palaeozoic rocks. Two large masses of gabbro and hornblende rock intrude the marble in Rameka Creek, at the northern end of the same range. Another large body of basic rock lies in and between the valleys of the Cobb and upper Takaka. It extends north and south about five miles, and is from a mile to a mile and a half wide. Pyroxenites and more basic rocks occur in large amount, and are in part serpentinized. Granite covers large areas in Totaranui, Kaiteriteri, and Motueka survey districts. Along the shore of Tasman Bay the rock is a biotite granite, at many points containing large crystals of orthoclase. Westward these phenocrysts disappear and hornblende tends to take the place of biotite. In many localities near the contact with the Palaeozoic marbles sphene is a prominent constituent. Numerous dykes of basic and acid rocks intrude the ancient sediments at many widely scattered points. In several localities granite dykes were observed to cut the basic rocks, whereas basic dykes are nowhere known to intrude granite. Economic Geology. Alluvial gold was formerly won from the beds and terraces of the Takaka, Waingaro, and Anatoki rivers and their tributaries. These diggings, which began in the late " fifties," were worked for many years, though at no time did they maintain a large number of miners. A few years ago coarse alluvial gold was obtained from a small branch of Rameka Creek, and recently shallow gravels have been sluiced for gold at Canaan. Grains of platinum or of alloys of the platinum metals occur with the alluvial gold of Takaka River and Waitui Stream. Quartz veins carrying gold and various base metals are known in several localities ; some have been superficially prospected, but none is being worked at present. The serpentine masses in the upper part of the Takaka Valley contain many veins of chrysotileasbestos. The asbestos deposits have been known for many years, but are in barren rugged country far from any road, difficulties that have prevented them from being thoroughly explored or commercially worked. Building-stones occur in large amount in that part of the subdivision examined last season. The most valuable are the marbles, which outcrop over many square miles on the southern end of the Pikikiruna Range and along both sides of the Takaka trough. The rock has been quarried at various points, and a considerable amount used in building. There are large quantities of high-grade stone in many pleasing shades of light and dark grey. Granite was formerly quarried at Tonga Bay. The rock, a medium-grained grey granite, is deeply weathered, and fresh rock was not exposed in the quarries. The dark basic rocks of the Riwaka and Rameka valleys could be reached from existing roads without much expense. Pulverized limestone for agricultural use is produced from the marble of the Riwaka Valley. The Tertiary limestone of the lower Takaka Valley has been quarried to supply local kilns and kilns in Nelson. Unworked deposits of soft travertine containing several hundreds of tons occur at the southern end of the Takaka trough.

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2. MANGAKAHIA SUBDIVISION. (By H. T. Ferrar.) Field-work began in Mangakahia Survey District on the 23rd November, 1925, and ceased on the 10th January, 1926, owing to the field party being transferred to Central Otago for the purpose of carrying out a soil survey of irrigation areas for the Public Works Department. During this short period the greater part of Mangakahia Survey District was examined, and the work was carried into Motatau Survey District. The area surveyed was about 120 square miles. Messrs. F. J. Turner, M.Sc., and W. E. La Roche, B.Sc., both of Auckland University College, acted as geological assistants. Mr. Turner, who was in charge during the last fortnight, left the work in such a state that it can be readily continued. Physiography and Culture. The country examined lies mainly at the southern end of Mangakahia Valley, where plains and low hills, 400 ft. to 500 ft. above sea-level, are almost surrounded by steep bush-clad hills, some of which attain to heights of more than 2,000 ft. The drainage of the district is effected mainly by the Mangakahia River, a tributary of the Northern Wairoa, and its affluents. The survey, however, was carried into the Ramarama Valley, which drains into the Bay of Islands. The settlers of the district, mostly dairy-farmers, occupy the alluvial flats, but by degrees they are spreading to the bush-clad hill-country and transforming it into pasture-land. The low hills mentioned above are mostly unoccupied except for parties of kauri-gum diggers. The hydro-electric power-house of Wilson's (N.Z.) Portland Cement (Limited) is situated near the south-east corner of Mangakahia Survey District. General Geology. No geological work in the area under review has been carried out since Sir James Hector, over sixty years ago, journeyed down the Mangakahia Valley : his hand-coloured geological map of North Auckland, dated September, 1866, forms a basis for the detailed survey now begun. Most of the igneous and sedimentary rock series described in previous annual reports dealing with the geology of North Auckland, and in Geological Bulletin No. 27, occur in the present area. The oldest rocks are the shattered non-fossiliferous greywackes and argillites of supposed Hokanuian or Trias-Jura age. These form a low ridge on the eastern side of the district near Aponga. Next in order of age are the tilted and faulted beds of sandstone and claystone (with greensand in places) of Waiparan or Upper Cretaceous age. Fragments of the fossil bivalve Inoceramus were found well down in this series in the bed of the Hikurangi Stream to the east of Te Horo Church. Altered dolerites and other basic igneous rocks form the high bush-clad hills. These igneous rocks overlie the Cretaceous claystones and sandstones, and, like the ultrabasic intrusions of Rodney Subdivision, are of approximately Eocene age. Comparatively undisturbed micaceous sandstones, which are extensions of the Whangarei Formation from the adjacent subdivisions, and therefore of Oamaruian or Oligocene-Miocene age, overlie the Eocene igneous rocks. Locally gravel-beds of Pliocene age overlie the Oamaruian (Whangarei) sandstones unconformably, and are followed by basalt-flows belonging to the Kerikeri Series of former reports. The basalts cover a triangular area bounded by the Titoki-Poroti Road on the north, the Wairua Stream on the east, and the Mangakahia River on the west. They are of late Pliocene or early Pleistocene age. Carbonaceous sands of Pleistocene age and Recent alluvium and swamps cover small areas. Economic Geology. Coaly partings in the younger sandstone series in Mangakahia Survey District, and the presence of workable coal in this series elsewhere, have led to the belief that buried coal-seams will be found in the district. Geologic study shows that this belief is erroneous. Limestones suitable for cementmaking or of use in agriculture are absent. There are, however, clays of economic worth, and the vast quantities of roadmaking material that can be furnished by the igneous rocks are a valuable asset. The lithological map which is being made is of value in connection with land-classification and the economic development of lands at present unoccupied. 3. KAITANGATA - GREEN ISLAND SUBDIVISION. (By M. Ongley.) Owing to the survey of the Kaitangata coalfield and adjoining districts having been extended to include the Green Island coalfield, the name " Kaitangata Subdivision," used in the last two annual reports, has been altered to " Kaitangata - Green Island Subdivision." From November, 1925, to May, 1926, the writer continued the geological survey of the Kaitangata - Green Island Subdivision, and for a month had the assistance of Mr. T. C. Hewitt, M.Sc., of Otago University. The country about Brighton, Saddle Hill, Green Island, Boulder Hill, and Whare Flat was mapped, and the coal-measures and sedimentary rocks were followed into the Dunedin volcanic area, on which.Dr, W. N. Benson, Professor of Geology at Otago University, is working. The schist areas in Clarendon, Maungatua, and Waipori survey districts were partly examined, and the mining areas near Waipori were briefly inspected.

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Topography. Along the coast are sandy beaches and rock platforms (below high-water level), and raised beaches 20 ft. and 50 ft. above sea-level. From the lower ground near the coast a tilted block, in part covered with Cretaceous and Tertiary sedimentary rocks and in part exposing an old eroded surface of Palaeozoic schist, rises gently inland. The crest is 600 ft. high, and on it are the volcanic peaks Saddle Hill (1,565 ft.), Jeffrey's Hill (1,414 ft.),"and Scroggs Hill (1,162 ft.). From it there is a steep descent to the Taieri Plain. The plain rises from 2 ft. above sea-level at Taieri Ferry, Henley, &c., to 60 ft. at Mosgiel (twelve miles from Taieri Gorge), and to 100 ft. at the north end (three miles beyond Mosgiel). North-east of the Taieri Plain rise the volcanic hills about Dunedin, and west of it are the steep eastern slope of Maungatua (a dissected fault-scarp) and the gently rising slopes near Clarendon dotted with volcanic peaks. West of this lies a plateau about 2,000 ft. above sea-level, formed of schistose rocks. General Geology. The rocks of the district are similar to those examined in 1923-25, and can be classified as in last year's report in the table here reproduced with slight alterations : —

Economic Geology. The magnetite rock mentioned in last year's report as occurring in a bed in the Jurassic greywacke at Dromedary Hill, Lochindorb Station, Warepa Survey District, has been analysed by the Dominion Analyst and found to contain over 70 per cent, of iron oxides and 8-62 per cent, of titanium dioxide. The analysis supports the view that the magnetite rock is of sedimentary origin. According to Mr. D. Finlayson, of Lochindorb Station, the coal which two dowsers asserted occurred in the Jurassic greywacke at Awatea, Catlins district, has been further searched for, but only thin streaks of coaly material have been found. The coal opened in 1925 in the New Mosgiel Colliery, Saddle Hill, has been found to be cut off by old workings, and mining there has ceased. The Willowbank Colliery has continued working its seam on the west of Jeffrey's Hill, and Mr. Scurr, the owner, has trenched other coal outcrops near at hand. There is a small plug of basalt on the hill close ahead of the dip, which will soon be struck in the mine. Over the hill, half a mile south of the mine and 100 ft. lower, occur boulders of conglomerate formed of schistose pebbles, the Kaitangata conglomerate, with pieces of coal 6 in. thick, like the Kaitangata coal. As this conglomerate occurs on tlie low slopes on the north-west of Saddle Hill below any of the coal worked there, that part should be further prospected by boring to the underlying schist. In the winter of 1925 a huge slip in Hut Creek, on the north of Boulder Hill (Trig. Station L., Dunedin and East Taieri Survey District), exposed a better outcrop of the lower part of the quartzconglomerate coal-measures than can be seen elsewhere in the vicinity. At 120 ft. above the underlying schist there is a prominent cliff containing crushed coal (Ift.), dark mudstone with streaks of coal (6 ft.), coal (3 in.), dark mudstone with streaks of coal (5 ft.), fine quartz sandstone with streaks of coal (10 ft.), and dark mudstone (3 ft.). Similar outcrops in different parts of the hill have been opened ; but no payable seam has been found, the best being the one near Salisbury mentioned in last year's report.

Strata. Thickness. Approximate Age. Clay, lignite, and gravel .. .. .. .. .. .. 100 ft. Pleistocene and Recent. (Erosion interval.) Agglomerate, basalt, &c. . . .. .. .. .. .. Varies. (Erosion interval.) Grey sandstone .. .. .. .. .. .. .. 60 ft. \ * Greensand, sandstone, and limestone .. .. .. .. 300 ft. f wamoan ' (Erosion interval.) Greensand and marl .. .. .. .. .. .. 200 ft. I\ n , , Fine quartz conglomerate and sand (tuffaceous) .. .. .. 200 ft. / 0 arai1, (Erosion interval.) Grey sandstone .. .. .. .. .. • .. .. 30 ft. Glauconitic sandstone and mud3tone .. .. .. .. 200-300 ft. Grey sandstone .. .. .. .. .. .. .. 50 ft. Lower Tertiary. Fossiliferous sandstone near Wangaloa and Boulder Hill .. .. 1-10 ft. Fine conglomerate of quartz pebbles .. .. .. .. 400-900 ft. (Erosion interval.) Pebbly shell-rock with belemnites at Brighton .. .. .. 30 ft. \ TT . p , + Fine conglomerate of quartz pebbles with finer beds and coal-seams .. 60 ft. / Aejaceous - (Angular unconformity.) Coarse conglomerate of greywacke and schist pebbles with finer beds and 500 ft. Upper Cretaceous, coal-seams (Strong angular unconformity.) Sandstone with plant-remains and thin coal .. .. .. .. \ T ura s i Argillaceous greywacke and argillite with Jurassic fossils .. .. / ' ' ' massic - Arenaceous greywacke and argillite with Upper Triassic fossils .. .. j Greywacke and argillite, non-fossiliferous (thick) .. .. .. i J> 4.500 ft. Triassic. Coarse conglomerate of greywacke, diorite, &c. .. .. .. | J (Erosion interval.) Greywacke and argillite with a bed of Carboniferous or Permian fossils .. 1 r AAA £ , TT T n J i Z c t j. n > 5.000 ft. Upper Palaeozoic. Coarse conglomerate or greywacke, diorite, &c. .. .. .. J x r ( Erosion interval.) Greywacke in places intruded by diorite, &c. (very thick) .. • • \ \r , T , r. J , A i*i / ,v. , x ' v ' > Very great Middle or Lower Palaeozoic. Quartz and mica schists (very thick) .. .. .. .. j J &

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The same beds with similar coal-seams extend along the west of Flagstaff and Trig. Station Q and continue north-east towards Wait.ati. The finer material in the quartz conglomerates is being quarried in two sandpits, the Jubilee sandpit at Fairfield, ten chains north of the shaft of the old Walton Park Coal-mine, and Shiel's sandpit, on the site of Loudon's Coal-mine, west of Trig. Station 82, Block 7, Dunedin and East Taieri Survey District. In both places the sand is quarried below the level of the railway, and in both the cover is getting thicker as the quarries are being extended. Similiar material lies above the railway-line and extends to the top of Ferny Hill, Trig. Station G, Dunedin and East Taieri Survey District. The homestead at Macgregor's farm, Block 14, East Taieri Survey District, is built of sandstone quarried there in 186]. The stone is soft and easily broken ; but in the house the blocks, which were cut thick and laid with the bedding flat, are not pitted or weathered. Calcareous mudstone (Burnside marl) is being quarried at Burnside at the rate of 40 tons a day, and used in making cement. It extends north past the reservoir, and south across the railway, under the east of Green Island township, but affords no better quarrying-place than at the present pit. At the top of the marl exposed in the quarry and in the Kaikorai Stream is a bed, 3 ft. thick, of pebbly greensandstone containing phosphatized pebbles and concretions. A sample of these has been analysed by the Dominion Analyst, and found to contain : CaO, 42-92 per cent ; P 2 0 5 , 16-68 per cent. ; and C0 2 , 8-40 per cent. The Pomahaka clay mentioned in last year's report has been analysed and tested by the Dominion Analyst, who reports that " the clay is suitable for the manufacture of the coarser kinds of stoneware, and possibly electric insulators. It would no doubt be improved by washing. It withstands a temperature of 1,580° C. without softening, and hence complies with the requirements for a second-grade British fireclay. The laboratory has no means of testing it at a higher temperature to ascertain whether it would comply with the requirements of a first-class fireclay." At the Abbotsford Tileries the residual clay on the glauconitic mudstone is being quarried and mixed with a small proportion of other clay to make tiles, the output of which is from twenty-four to forty railway trucks a day. At odd seasons bricks are made. At Wingatui the Wingatui Brick and Tile Company is quarrying the residual clay on the low schist slopes of the Chain Hills and turning out seventeen thousand bricks daily. 4. SOIL SURVEY, CENTRAL OTAGO. (By H. T. Ferrar.) Introduction. At the request of the Hon. the Minister of Public Works, the North Auckland Geological Survey field-party was transferred to Central Otago for the purpose of constructing a soil map of the lands now being irrigated or proposed as irrigation areas. The survey was commenced on the 14th January, 1926, and was suspended for the winter at the end of the month of May. During this time Messrs. F. J. Turner, W. E. La Roche, and N. 11. Taylor acted as field assistants for various periods. The average rate of survey has been about 1,000 acres a day. Camps were placed successively at convenient spots in the irrigated areas of Ida Valley, the Manuherikia Valley, and the Molyneux (Clutha) Valley, and the survey was extended into unirrigated areas as far as seemed necessary. By this means Ida Valley was mapped from its southern end northeastward to Ida Valley Railway-station, and the Manuherikia Valley from Omakau to Clyde and Alexandra. The following isolated areas —namely, Olrig, Galloway, Earnscleugh, Little Valley, Fruitlands (Bald Hill Flat), Roxburgh, Commissioner's Flat, Teviot (Anderson's Flat), Ettrick (Moa Flat), and Miller's Flat —were also mapped. Methods op Mapping. The first requirement of a soil survey is a method of cartographically representing different soiltypes, for a soil map is designed primarily to show the geographic position and extent of soil-types, however they may be differentiated. Various methods applicable to New Zealand conditions have been proposed, notably by B. C. Aston, H. T. Ferrar, and L. J. Wild, for differentiating the soils, whilst L. Cockayne, P. G. Morgan, and others have indicated possible means of undertaking a soil survey. In practice, a lithological map is the basis used by most countries that have undertaken soilsurvey work. The topographical map forming the framework upon which the lithological map is built shows the situation and aspect of each soil-group or soil-type, differentiated by means of some easily recognizable symbol. By including climatic data and other desirable information upon which the productivity of the various soils depend the value of this map will be greatly increased. In Central Otago the greater part of the irrigable land is covered by one type of soil, an seolian silt, derived from the mica-schist and other Palaeozoic rocks forming the mountain-ranges of the region. Smaller areas are covered by gravels of varying texture and depth, also derived from these ancient rocks, or by sands derived from much younger sedimentary rocks. Since the productivity of these soils depends more upon the supply of irrigation water than upon the character or chemical composition of the soil itself, the topographical map becomes of more importance than the lithological. The map in course of preparation consists of field-sheets, on a scale of 1 inch to 20 chains, upon which are drawn data supplied by the Lands and Survey Department. Additional topographical detail is obtained by means of prismatic-compass bearings and paced traverses. Notes upon the nature of the soil, upon the vegetation, and upon other pedological characters that are observed during the course of the work are also added to the field-sheets.

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Laboratory Work. Soil and water samples collected systematically are being analysed in the Dominion Laboratory in order to determine their " potential plant-food " content and the presence or absence of substances that may be harmful to plant-growth. These determinations will be continued periodically, and will yield data of permanent value in connection with the complicated subject of irrigation and its consequences. In most countries where land is brought under irrigation certain deleterious effects sooner or later become manifest. Central Otago is no exception, though naturally the harmful effects of irrigation water are not so great as in countries where evaporation is greater and rainfall less. In portions of some irrigated areas in Central Otago soluble sulphates inhibit the growth of pasture grasses, whilst in other places excess or deficiency of water itself has a deleterious effect upon the soil. The degree to which these harmful factors operate depends upon the quantity and manner of application of irrigation water, upon the quantity of soluble salts naturally present in the soil and subsoil, and upon the general porosity of the land. The work now being done portrays the present state of the land, and any chemical changes that may take place in the future will be easily recognized. Collateral Work. Geological advice, as detailed in another report, was given to the Public Works Department with regard to rock-structures. As opportunities presented themselves, data were collected with regard to the occurrence of gold, lignite, and other mineral products of the district. These will be discussed at some future time, when more observations are available from a wider field than has been covered during the past field season. 5. WAIROA, NAPIER, AND RAUKAWA WEST, HAWKE'S BAY. (By P. G. Morgan.) From the 19th to the 25th August, 1925, I was in the Hawke's Bay Land District, and during this time made visits from Napier to Wairoa and Raukawa West. While at Wairoa (formerly called Clyde) I examined a small part of the coast-line south-west of the mouth of the Wairoa River, and also a small area north-east of Wairoa, on the east side of the river. The rocks in these localities, other than Recent deposits, are mainly rather poorly fossiliferous claystones, either nearly horizontal or dipping to the south-east or south-south-east at angles varying from 1° or 2° to 10° or more. On the Napier Road, between Wairoa and the Waikare River, the rocks are mainly claystones, and in various places show dips to the south-east similar to those seen near Wairoa. The fossils found in the Wairoa claystones, according to Dr. J. Marwick, indicate an Upper Miocene age. Hitherto the oldest rocks near Wairoa and along the coast south-westward have usually been regarded as of Pliocene age. Several reports and papers on the geology of the Napier district have been written, but as yet exact agreement regarding the stratigraphical position of the limestones and other calcareous rocks forming Blufi Hill (Scinde Island) has not been reached. Lately, near Napier Breakwater, on the advice of a water-diviner (or dowser), a bore was drilled in search of oil to a depth of 360 ft. This, I understand, penetrated blue claystone and similar rocks. No oil was found. On the western side of Blufi Hill the strata dip westward at angles which may reach 15° ; on the eastern side near the bore they are nearly flat. Hence there is a structure not unfavourable to the accumulation of oil, if it is present in the strata. On the 24th August Raukawa West, some miles south of Maraekakaho, and about twelve miles south-west of Hastings, was visited. Here, on the property of Mr. W. Macfa.rlane, is a bore which, on the advice of the dowser referred to above, was drilled to a depth of 691 ft. in search of natural gas. Only a little gas —not enough to be of any use —was encountered. When the cap on the casing was removed the accumulated gas, on being lit, burned for a few seconds. The lower part of the bore had probably collapsed, otherwise the flow of gas might have been a little greater. The bore is said to have been drilled through blue papa (claystone), sandy in the lower part. A small flow of water with a slight taste of mineral salts and a faint smell of sulphuretted hydrogen escapes from it. About a quarter of a mile to the north, on the west side of Waikerenui Creek, there is a strong emanation of inflammable gas. The gas escapes with a considerable flow of salty water. Both gas and water have been previously analysed. A sample of the gas taken by me on the 24th August last contained 91-9 per cent, of methane and 2-6 per cent, of ethane (Dominion Laboratory No. Q 2366). Near the gas spring, in a rill draining to the Waikerenui, fine-grained fossiliferous calcareous sandstone is exposed. The overlying and underlying beds are probably claystones. About 300 ft. above, near the top of the higher ridges on both sides of the Waikerenui Valley, a band of shelly limestone outcrops. This lies nearly horizontal, and is at almost the same level on either side of the valley. Thus probably no fault traverses the strata of the Waikerenui Valley, as has been supposed. North of the gas-emanation described above there are, as I was informed, other gas springs. Oil and Gas Prospects, Hawke's Bay. East of the Ruahine Mountain's nearly the whole of Hawke's Bay is covered by Upper Tertiary strata. In some parts Upper Cretaceous beds appear on the surface. These Tertiary and Cretaceous rocks are of marine origin, and not unreasonably may be expected to contain petroleum in places where the structure is favourable. Detailed geological survey is necessary in order to locate possible oilbearing structures and to estimate the chance of success if drilling is undertaken. Gas-emanations are not uncommon in Hawke's Bay—for instance, in the Nuhaka-Morere district; at Raukawa West, as described above ; near Weber, &c. Probably, therefore, considerable supplies of natural gas could be obtained in these and other districts by drilling in the right places.

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6. UPPER URENUI VALLEY, ETC., TARANAKI. (Summary of report by P. G. Morgan.) At the end of December, 1925, and again in March, 1926, I visited various localities in Taranaki, chiefly in order to form an opinion concerning the validity of an anticlinal structure in the upper part of the Urenui Valley which Taranaki Oilfields (Limited) was considering as a possible source of oil. The greater part of the Upper Urenui Valley was examined by Mr. E. de C. Clarke about 1910, as part of the survey of the New Plymouth Subdivision. The results of Mr. Clarke's work were published as N.Z. Geol. Surv. Bull. No. 14 ; 1912. In late years that part of the Urenui Valley which is in Upper Waitara Survey District has been geologically surveyed by Mr. L. I. Grange as part of the Tongaporutu-Ohura Subdivision, and a detailed report dealing with that subdivision has been prepared, but is not yet published. Westerly dips of the strata are the rule throughout the Urenui Valley and adjoining areas, but from near. Okoke south-south-westward to near the head of the Urenui many easterly dips exist, mostly on the east side of the Urenui Valley. A few of these were mapped by Mr. Clarke and Mr. Grange, and the remainder were found by the geologists attached to Taranaki Oilfields. On the whole the dips indicate a gentle anticline, with a domal portion near the middle part of its known course. The suggestion has been made, however, that the easterly dips were due solely to current-bedding, not to tectonic movement, and therefore that the Upper Urenui " anticline " was a pseudo-structure. In the Lower Pliocene and Miocene strata of Taranaki current-bedding is widespread, and not less so in the Urenui Valley than elsewhere. Some of the observations of easterly dips, as well as dips in other directions, are vitiated or rendered very dubious by current-bedding, and in one or two cases by probable slumping during consolidation. I cannot, however, hold with the hypothesis that over the greater part of Taranaki the Tertiary strata dip only in directions with a westerly component, and that practically no easterly or " reverse " dips are to be found. In order that this hypothesis should hold good the current-bedding would have to be on a gigantic and hitherto unheard-of scale. In order definitely to prove or disprove it a large amount of highly detailed field-work is needed. In the meantime I regard the structure of the Tertiary strata in the Upper Urenui Valley as truly anticlinal. At the east end of the sec.ond road-tunnel on Whangamomona Road, some miles south-east of Whangamomona, thinly-bedded fine-grained sandstone and sandy claystone, dipping eastward at fully 20°, rest upon nearly horizontal beds of brown sandstone. The separating surface was formed by erosion, and, except for small irregularities, is parallel to the upper beds. The dip of the upper beds can be explained reasonably only by current-bedding. The occurrence as a whole may be regarded as a good example of what is termed contemporaneous erosion, or it may be a case of unconformity —a peculiar one, such as that noted in the fifth paragraph on page 44 of N.Z. Geol. Surv. Bull. No. 24. Two miles or less south-east of the locality just, mentioned nearly horizontal strata form the lower few feet of a high steep road-cutting. Above, at the east end, beds of sandstone, wedging out westward, dip at 8° or more to the west, while at the west end the upper beds dip eastward. A view from a little distance thus gives a deceptive appearance of a syncline, whereas a close view suggests an infilled channel. Some of the lower beds on the west side seem to be cut of! by erosion. The inclined upper beds perhaps represent foreset beds in a delta formed by the spilling-over "ot the material from two different points. On the coast-line north of Pukearuhe, just to the south of Waikaramarama Creek, the sea-cliffs show very fine current-bedding (in Urenui beds). This, however, is of normal type, indicating shallowwater conditions during deposition. Northward the strata (mainly sandstone) exposed in the cliffs show here and there a rather mild current-bedding, which causes small variations in the dip of the beds, here on an average about 5° to the south-west. A mile to the north of Waikaramarama Creek a persistent nearly horizontal surface represented by a line in the cliffs separates two sets of beds dipping at slightly different angles. This surface seems to indicate true unconformity rather than contemporaneous erosion, and according to Mr. L. I. Grange it separates Urenui beds (above) from Tongaporutu beds (below). 7. AURIFEROUS DRIFTS, St. BATHANS, CENTRAL OTAGO. (Report by P. G. Morgan, slightly abridged.) In February, and again in April, 1919, I made visits to St. Bathans, Central Otago. Only brief reports on these visits were supplied, but some geological data will be found in a paper by me, " The Tertiary Beds of Central Otago" {N.Z. Journal of Science and Technology, vol. 3, No. 1, pp. 29-33, 1920): in A. McKay's "Report on the Older Auriferous Drifts of Central Otago" (Parliamentary Paper C.-4, 1894 ; second edition 1897) ; and in other publications listed in my 1920 paper. On the 13th and 14th April, 1926, I again visited St. Bathans and made some further observations in this interesting locality. Much work remains to be done before a detailed geological report, can be written. The preparation of such a report involves the examination of many localities distant from St. Bathans where Tertiary quartz-drifts occur ; it also involves a large amount of research. Several baffling and difficult problems must, if possible, be solved. The gold-workings at St. Bathans are in a thick series of quartzose gravels, grits, and sands, interbedded to some extent with lignite and brown (carbonaceous) and light-coloured clays, overlain by a thick stratum of greenish fossiliferous clay of fresh-water origin. The quartz drifts are also of fresh-water origin : they appear to have been formed on or near the shore of an ancient lake, the water-level of which was slowly rising. Ultimately in the St. Bathans locality the lake became deep, and muds were deposited above the gravels and sands. These beds at St. Bathans strike between north-west and north. Their dip is generally about 45° to the south-west, but in places is nearly vertical ; in places a good deal less. According to a rough estimate the thickness of the quartz drifts and associated beds exceeds 500 ft. ; the overlying clays are at least 400 ft. thick.

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Gold is distributed thinly through the quartz drifts, but the Kildare lead, which is a gravel typically from 3 ft. to 8 ft. thick, traceable for 900 ft., or more, is very rich, and gives prospects equal to an ounce of gold or more per cubic yard. In places the gold content is probably several ounces per cubic yard. For 150 ft. or more (180 ft.) below the original surface the Kildare lead and the adjoining quartz drifts have been worked by hydraulic sluicing and elevating, and an enormous hollow, " glory hole," or " gorge," has thus been formed. Lately the St. Bathans Gold-mining Company has been formed in order to work the Kildare lead at deeper levels by ordinary mining methods. To this end the company has sunk a main shaft west of the " glory hole " to a depth of about 120 ft., but here quicksand caused difficulty, and work on the shaft was suspended. An adit driven from the bottom of the " glory hole " towards the line of the shaft encountered quicksand also. A small shaft was sunk to a depth of 52 ft. or 53 ft. at a point near the bottom of the " glory hole " and north of the Kildare lead. From it at 50 ft. down a level was driven south-eastward, and from this crosscuts towards the Kildare lead were driven. Running sand was encountered close to the lead, but this was ultimately tapped and gave a rich prospect, said to be equal to 2 oz. per cubic yard. Several of the sandy layers in the St. Bathans quartz drifts have thus been found to have the properties of quicksands, and therefore the exploitation of the Kildare lead becomes a problem of great difficulty. These sands, if dry, stand up well, but if wet have undesirable physical properties.. On examination they are found to consist of small angular particles of quartz, mixed with a large proportion of very fine particles. When dry, a sample of these sands, owing to the so-called force of adhesion between its particles, is comparatively firm and solid, but on being wetted it becomes a slippery, greasy, and mudlike wet sand. To some extent the coarser beds in the quartz drifts, owing to their containing much fine sand, when wet behave similarly, but they are not likely to cause much trouble to the miner. The successful working of the Kildare lead below drainage level, and probably of similar deposits elsewhere in Otago, depends upon the successful draining of the auriferous leads in advance of actual mining. The problem thus presented will have to be solved by special methods of working. The Kildare lead consists of a gravel with many well-rounded quartz pebbles larger than those ordinarily found in the quartz drifts : there is also much sand, formed almost wholly of angular and subangular quartz particles. Numerous small grains of dull-coloured pyrite or marcasite are present. Examination of the sand under the microscope shows that tourmaline and monazite occur, but only in very small amount. Zircon seems to be absent. Tourmaline was found also in the sand layer tjiat occurs at the mouth of the adit driven from the " glory hole " towards the main shaft. The gold in the Kilclare lead is mainly in somewhat large, heavy " colours," and forms what is termed a " good sample." The St. Bathans gold is nearly free from impurities, and accordingly is worth more than the gold from most other Otago localities. 8. MURCHISON DISTRICT, NELSON. (By P. G. Morgan.) In accordance with instructions I visited Murchison on the 19th and 20th May, 1926, in order to make a general examination of the district with a view to obtaining some idea of its oil possibilities. Mr. J. F. Downey, Inspector of Mines at Reefton, kindly accompanied me, and took me to many points of interest in his motor-car. Thus I was able to see more of the country than would generally be possible in such a short time. At the outset I ought to explain that the detailed examination of the whole of the Murchison district would occupy a geologist for several months, and therefore this report must necessarily be of a highly incomplete nature. Although several geological reports dealing more or less with the Murchison district have been made, its geology, and more especially its structure, are still poorly known. Reports bearing on the geology of the Murchison district are as follow : — 1861. Julius von Haast: Report of a Topographical and Geological Exploration of the Western Districts of the Nelson Province, New Zealand. (See pp. 10-21, 95-99, 122, 125-127. 130.) 1884. S. H. Cox : On the District between the Maruia and Buller Rivers. Rep, Geol. Explor. during 1883-84, No. 16, pp. 1-10. 1888. James Park : On the Geology of the Owen and Wangapeka Goldfields. Rep. Geol. Explor. during 1887-88, No. 19, pp. 74-78. 1895. Alexander McKay : Geology of the South-west Part of Nelson and the Northern Part of the Westland District. C.-13, in Mines Reports, 1895. (See pp. 3, 4-6, 16-17, 19, 25 et seq., and map.) Republished in pamphlet form, 1897. 1896. H. A. Gordon and Alex. McKay : Mining Reserves, Westland and Nelson. C.-9, in Mines Reports, 1896. (See p. 3, 12-13, and map.) Mostly republished in pamphlet form, 1897. 1915. J. Henderson : Notes on the Geology of the Warwick Valley. Ninth Ann. Rep. N.Z. Geol, Sum., C.-2, pp. 102-103. 1917. J. Henderson : Notes on the Geology of the Murchison District (Summary of Report). Eleventh Ann. Rep. N.Z. Geol. Surv., C.-2b, p. 7, with map at end. 1918. J. Henderson : Notes on the Geology of the Murchison District. N.Z. Jour. Sci. & Tech,, vol. 1, No. 2, pp. 108-112. Early in 1922 Dr. L. A. Cotton, now Professor of Geology at Sydney University, visited the Murchison district on behalf of Mr. James Burns, of Sydney, and reported to him on the oil prospects near Warwick Saddle, and at the Mangles River a short distance above the Blackwater Stream junction. No two of the reports mentioned above exactly agree as to the sequence of the Tertiary rocks in the Murchison district, and the management of the Murchison Oil Company has still another view. Nor did what I saw during my visit enable me to agree fully with any previous observer. It is

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therefore evident that the geology of the Murehison district is by no means simple, and only by means of a careful and detailed survey made by experienced geologists can the true succession of the rocks ■and their structure be made out. The following remarks should be read in conjunction with Dr. J. Henderson's report published in volume 1 of the Journal of Science and Technology. (See also sketch-map in 11th Ann. Rep. Geol. Surv.) The pre-Tertiary rocks of the Murehison district and surrounding areas consist mainly of granite, •greywacke, and argillite of Palaeozoic age. These rocks are of no interest in connection with the oil possibilities, and need not be described. Resting upon them is a belt of Lower and Middle Tertiary strata, in plan shaped like an elongated diamond, extending northward from the Sheriff River, thirty miles south of Murehison, to the upper Wangapeka Valley, nearly twenty miles north of Murehison. In its middle part this belt is over twenty miles wide. It therefore covers a large area. The Tertiary rocks are mainly conglomerates, sandstones, mudstones, and limestones. The total thickness of these strata is great, possibly over 10,000 ft. According to all the geologists who have reported on the district, the limestone part of the succession is the youngest, but opinions differ as to whether conglomerates or arkositic sandstones form the lowest part. The management of the "Murehison Oil Company, however, believes that the limestones are the oldest beds, and that they are succeeded by calcareous sandstones, and these by the conglomerates. Probably the exact opposite is the true order ; but in the section from Doughboy Stream eastward through Murehison to the Mangles River the apparent succession is certainly from limestone upward to sandstone and to •conglomerate, as stated by the Murehison Oil Company. The rocks dip at high angles eastward from Doughboy Creek to the Mangles-Buller junction, and are much disturbed by strike-faults. If the faults are reverse faults, then the apparent order of the strata could be opposite to the true order, and this is my present opinion. From a little above the mouth of the Mangles to Blue Duck Creek the rocks seen are conglomerates (with interbedded sandstone, &c.) that clip at high angles to the north of west. East of Blue Duck Creek sandstones dipping in the same direction appear. Towards the mouth of Blackwater Stream the sandstones flatten in dip, and half a mile to the east, at the oil-seepages, are said to be dipping steeply eastward. Sandstones continue for perhaps two miles to the east. Their strike as observed by me is north-north-east (32°), and their dip 40° to 45° to the south of east. These observations, taken as they stand, would indicate that between Doughboy Creek (west of Murehison) and Blue Duck Creek (several miles east of Murehison) there is a huge syncline, which is followed eastward by an anticline, with its crest near the mouth of Blackwater Stream. The complicating effects of faults on the structure, however, have to be taken into account. When this is done the syncline disappears, and the anticline, as a possible oil-bearing structure, is shorn of much ■of its significance. Petroleum Prospects, etc. In the bed of the Mangles River, less than half a mile east of the mouth of Blackwater Stream, :small amounts of oil and inflammable gas are constantly escaping. Gas also rises from the bed of Blackwater Stream, just below the road-bridge. Elsewhere in the Murehison district several gasescapes are known. Near "Warwick Saddle, many miles south of Murehison, four oil-seepages have been found. Inflammable gas is stated to exude from mudstones in the Owen River district. These facts indicate clearly enough that the Tertiary rocks of the Murehison district are petroliferous, but they are far from indicating that petroleum is present in quantity sufficient to repay the oil-driller.' Encouraged by the oil and gas seepages, and by what seems to be an anticlinal structure, the Murehison Oil Company has begun to bore close to the Mangles River, about a quarter of a mile above the mouth of Blackwater Stream. At the time of my visit this bore was 376 ft. deep, and was partly lined with 10 in. casing. Work had been suspended for a few days on account of several lengths of the casing on hand being defective, and therefore requiring reconditioning, work that had to be done at Nelson. The rocks penetrated in the bore consisted mainly of somewhat calcareous sandstones, with bands of sandy limestone, shale, &c. ■9. PROPOSED TUNNEL-SITE, PEGLEG GULLY, AND DAM-SITE, MANUHERIKIA FALLS, CENTRAL OTAGO. (Summary of reports by H. T. Ferrar.) On the 23rd April, at the request of the District Engineer, Public Works Department, Dunedin, a geological examination was made of the site and surroundings of a proposed irrigation-water tunnel through a ridge near Pegleg Gully, at the upper end of Manuherikia Valley. The object of the examination was to ascertain if any unforeseen difficulties would be encountered when tunnelling is undertaken, and to determine how far slipping of the hillside above the tunnel-entrance would endanger the tunnel when excavated. It was found that the proposed tunnel would pierce schistose greywacke for the greater part of its length. This rock is much jointed, and will probably require timbering during excavation, and parts at least of the bottom and sides will probably need to be lined with concrete to prevent leakage of water. The slip material above the proposed tunnel-entrance on north side of the ridge will need to be supported, and it was recommended that trial drives be made at two points in order to gain .some idea of its dimensions. Advice was also sought by the Public Works Department with regard to the structure (faults, joints, &c.) of the rocks on which the proposed Manuherikia Falls Dam is to be placed, and the rigidity of its foundation. The rock is jointed greywacke, the structure lines being directed approximately west-north-west and east-south-east and at right angles to the river-gorge. The joint-planes of the greywacke dip at high angles towards the north. Hence the foundations of the dam wheu completed will be seated on, and the wings will be supported by, one and the same hard band of rock.

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