ABSTRACT REPORT ON THE PROGRESS OF THE GEOLOGICAL SURVEY OF NEW ZEALAND DURING 1866-7.
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PROGRESS OF THE GEOLOGICAL SURVEY OF NEW ZEALAND DURING 1866-7.
THE field work of the first season ofhe survey in 1865-6 embraced a superficial examination of the district lying to the north of the City of Auckland, with a special view of ascertaining the value and extent of the Coal Fields at Wangarei and the Bay of Islands.
The results of this examination were, in part, furnished in the form of Maps and Memoranda to the Provincial Government of Auckland, and a geological map of the above district was published in November last.
The natural sections available for ascertaining the succession of the strata were found to be so imperfect, that no satisfactory classification could be proposed until the same formations had been studied under more favorable circumstances in other parts of the Colony.
During the same season, an opportunity was also afforded me, through the kindness of His Excellency the Governor, of visiting a portion of the Southern Districts of the Province of Auckland, examined by Dr. Hochstetter in 1860, which enabled me, by comparison, to apply the results obtained by that eminent geologist to the investigation of the structure of other parts of the Islands.
During the past year, the classification of the newer formations in the Waikato District, as originally proposed by Dr. Hochstetter, has been modified by the investigations of Captain Hutton, F.G.S. who was employed by the Provincial Government to report on the extent of the Coal Fields in the Lower Waikato basin. (See Report dated 3rd June, 1867.)
Notwithstanding that considerable progress has been made towards correlating the results obtained by independent geological observers in different parts of the Colony, so much uncertainty of nomenclature still prevails, that until a thorough comparison of
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the collections from different localities is made, the geological classification must still remain arbitrary in respect to all but the greater divisions.
During the past season the following reconnoissance surveys have been made by this department.
1st. Portion of the Province of Taranaki, by myself in October, and by Mr. Buchanan in March.
2nd. The Western districts of the Provinces of Nelson and Canterbury, from Cape Farewell to Milford Sound, which occupied me for a period of six months, from November till April.
3rd. The Kaikoura District was examined, and a large collection of fossils obtained by Mr. Buchanan; and, in returning from the south by the eastern side of the Spencer Mountains, I also visited the interior part of the same district.
The notes and specimens which have been accumulated in the course of these surveys will require a considerable time for publication; therefore, in making the following abstract, only general results and conclusions, having an immediate and practical bearing on questions of economic geology, are given, the detailed Reports, which have been reserved for future communication, being already in an advanced state of preparation.
LEAVING Wellington on the 23rd of October, 1866, I first visited the Province of Taranaki, and examined the formation in which the petroleum oil occurs. The geology of this interesting locality can only be understood by following the natural section shewn along the sea coast for thirty miles to the north of New Plymouth, as shewn in Section No. 1 which gives the succession of the strata from the White Cliffs to the Waitara River.
The White Cliffs (600 to 700 feet high) are composed of older tertiary marls, containing a few marine shells and corals and marked by lines of calcareous septaria dipping to the southwest and visible along the coast as the lower part of the sea cliffs as far south as Oneira, which is five miles north of the Waitara River. At this point they are overlaid unconformably by newer tertiary clays, the junction being marked by a stratum of rolled septaria derived from the older marls, intermixed with quartz gravel and broken shells. As the overlying clays differ only very slightly from the older marls, if this conglomerate bed were
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not present it would be very difficult to detect that a different and newer formation had been entered upon (see Section No. 2).
The newer clays (pliocene tertiary) rest horizontally on the bed of conglomerate, and in the course of a few miles from where they first appear, they acquire a brecciated structure from the presence in them of angular fragments of volcanic rocks, indicating that the deposition of these clays was contemporaneous with volcanic eruptions in the neighbourhood, which, judging from the interposition among the angular breccias of beds of rolled conglomerate, were evidently of an intermitted character. Section 3 of the headland at Titirangi Pa shows the mode in which these formations occur exposed in the sea cliffs. South of the Waitara River this clay breccia passes into a tufaceous agglomerate in which both the matrix and embedded fragments are of volcanic origin, probably indicating a near approach to the centre from which the eruptions took place.
At the Sugar Loaf Point a break occurs in the section, owing to the intrusion of a dyke-like-mass of trachyte porphyry. This dyke, which is 300 feet wide, lies in the magnetic meridian, and forms the main Sugar Loaf and the Island of Moturoa. It appears to be of earlier date than the tufaceous agglomerates, having probably stood as an island ridge in the sea in which the latter were deposited. South of the Sugar Loaf the agglomerates again prevail, but at Fort George they form only the lower part of the cliff, being overlaid by newer volcanic tufas from the Mount Egmont centre, which are probably the equivalents in that locality of the beds next to be described.
These are pleistocene deposits consisting of stratified gravels and sand rock (not hard enough to be termed sandstone) with beds of lignite. This formation, which corresponds in age and stratigraphical position with certain of the auriferous gravels in the South Island, is highly charged with oxide of iron, and is readily distinguishable, forming the upper part of all the cliffs along the coast north of the Waitara, by its deep red colour. These gravels do not extend far inland nor to a greater altitude above the sea than 150 feet, so that they must be regarded as in some way connected with an ancient coast line, and from the circumstance that at the base of this formation in many places, and underneath the lignite seams, there is a layer of rolled broken shells of existing species, we may infer that these gravels have been deposited in lagoons parallel with the coast line during a gradual elevation of the land, and that
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they have been overtaken, as it were, by the encroachment of the sea, and exposed in the sea cliffs after they are 80 to 100 feet above the present level of the tide. As, during the interval which must have elapsed, there was time for the formation of beds of lignite 8 to 10 feet thick, we thus have an indication of the extreme slowness with which changes of level are taking place, even in an area of such marked volcanic action as that around Mount Egmont.
Section 4 of the Fishing Cliff at Fort Clifton, shows the manner in which this formation has been exposed by the destructive action of the sea on the tough miocene marl.
The only other formations observed are superficial deposits still in progress, such as a rich brown loam in the district around Mount Egmont, derived from the decomposition of volcanic tufas and the sand dunes along the coast, which latter are sometimes extremely consolidated by the infiltration of iron as to resemble a sandstone formation of much higher antiquity.
In the foregoing section we may safely conclude, owing to the disposition of the strata, that we have somewhat the same succession of formations which would be encountered in a vertical line in the Sugar Loaves, namely--
(a). Volcanic breccia ...... 250 to 350 feet
(b). Newer tertiary clays .... 400 "
(c). Conglomerate and quartz cement 1 100 "
(d). Older tertiary marlstones .... 900 "
The above estimates of the thickness of the strata to be passed through are taken from the coast sections and are therefore only very approximate.
The rock in which the borings for petroleum is in progress is the breccia a in the above section.
This breccia or agglomerate consists of a variety of trachyte and basaltic fragments, cemented by a tufaceous clay and calcareous marl or ash of various shades of red, yellow, and green colours, but sometimes there occurs a thick bed of tufaceous clay of green tint with but few included fragments.
Between the innermost island and the north headland the fragments from this breccia, where the stratum has been denuded by the sea, form a natural causeway, which is dry at low water, and it is on this causeway principally, but also round the shore of the headland, that the indications of the presence of petroleum are
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POSITION OF THE BORINGS FOR PETROLEUM AT SUGAR LOAF POINT TARANAKI.
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found. Masses and seams of a ferruginous tufa or clay ironstone, which intersects the tufaceous clay in the neighbourhood of the great dyke, yield oil when broken, but whether these indicate the outlet of fissures which are vents by which the oil escapes from a deep seated source or whether they are merely masses of bituminous ironstone, had not been ascertained.
At the time of my visit borings were in progress at three places, and in Section No. 5 their relative position and depth is represented.
Close to the main Sugar Loaf and to the foot of the cliffs is the Taranaki Company's bore, No. 1 (A in Section), which has been sunk with much trouble to a depth of 300 feet. The derrick stands at 10 feet above high water, and for some time the water level in the bore maintained this level, but after a time it sunk suddenly to 32 feet, which would appear to indicate the existence of subterranean channels communicating with chambers where there is less than the external atmospheric pressure, owing perhaps to the condensation of oil vapours. At 254 feet a patch of the grey ferruginous tufa, like those seen at the surface, was passed through, charged with oil, which was the only result.
In this bore some patches of hard basaltic rock was encountered, but in the whole there was no decided change in the character of the agglomerate.
The Taranaki Company's bore, No. 2 (C in Section), is on the island off the north headland, and is commenced on a shelf 20 feet above the water level.
This island consists of ferruginous sand 50 feet, false-bedded like the sand dunes at New Plymouth, and resting on 40 feet of red tufaceous sand, which again rests on the agglomerate.
In the section which is shown in the lower part of the cliffs of this island, the agglomerate is seen to be very distinctly inter-stratified with beds of indurated tufa and water-worn fragments of rock. The bore was, in October, sunk to a depth of 145 feet, being 10 feet in the sandstone, 95 feet in the agglomerate breccia, 30 feet in consolidated tufa, and a few feet more into the agglomerate again. A few oil patches have been passed through, but no appreciable quantity has been obtained.
The third bore is that of the Alpha Company, which is situated a short distance from the north headland (see B in Section 5). It is from this locality the most of the oil which has been chemically examined has been obtained. At 10 feet above high water, and close to the boulder-covered shore, into a high
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sandy cliff, a shaft was sunk for 60 feet in the agglomerate, from the sides of which, at 44 feet from the surface, oil was found to ooze.
This shaft was continued by a bore hole to a depth of 180 feet, oil being got at 80 feet, and again at the extreme depth.
When allowed to stand at rest, a considerable quantity of oil collected both on the surface of the water in the well, and also in the bore tube, accompanied by the escape of gas. This oil was pumped into a tub along with the water, from the surface of which it was afterwards skimmed off. Recently, the well has been pumped more regularly, and yields, I am informed by the Directors, about fifty gallons a week.
The escape of gas in large quantities from under the sea at various spots among the islands, would seem to indicate that the oil described as occurring in the ironstone seams is only a secondary deposit, and as we now know, from what has been observed respecting the occurrence of bituminous products on the East Coast, that the inflammable gas and oil escape from the surface in localities where the most superficial bed is the marlstone (d. in the section), we must conclude that its source is from some more deep-seated stratum than any that have been described, and that its reaching the surface at the Sugar Loaf Point through the superincumbent formations, must be dependent in some way upon the dislocations in the neighbourhood of the great igneous dyke.
As there is every appearance of the formations a, b, and c, being more recent than the eruption of the dyke and therefore not dislocated by it, it is just possible that the oil and gas may have escaped upwards as far as the base of these formations, when in that case it would be collected in reservoirs at a depth, I should surmise, of from 500 to 700 feet below the surface, although by following fissures such as those marked by the ironstone veins, it may rise in small quantities to a much higher level and even to the surface.
What I would wish to impress with regard to these oil wells, as I did in my former report on the subject, is, that there is no indication in the Taranaki District of the occurrence near the surface of the regular alternations of sandstone and shales which characterizes the best oil-bearing formations. 2
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Under the marlstone formation, judging from analogy with other parts of the Colony, there probably occurs a thick group of ferruginous clay and sandstone, which again rest on the same coal formation as on the West Coast of Nelson. Great interest will therefore attach to the investigation of the geology of the Mokau District, and of the country lying between the range of hills terminating on the coast at the White Cliffs, as in that area the underlying formations may be expected to occur, and I think it very probable that among them extensive carbonaceous strata will be discovered.
Respecting the prospect of gold occurring in the Province of Taranaki, concerning which many inquiries were addressed to me, I am not able to give much encouragement. If it does occur, it will be in some area where older rocks than any I saw are superficial, or where such rocks form high and steep ranges, as on the West Coast of the South Island, where the streams have been enabled by their rapid fall to shed the auriferous drifts over the surface of the marine tertiary rocks, which lie at the base of the mountains. I do not know enough of the interior and northern districts of the Province to judge whether such conditions exist, but the analogy to the western district of the Nelson Province enables me to say that were the thick coating of tertiary and volcanic rocks removed, the underlying palaeozoic rocks would be more likely to prove auriferous than any other slate ranges of the eastern part of the North Island. The North Island must always be considered, as compared with the South Island, to be at the present epoch depressed, probably to the extent of several thousand feet, the level of the land being brought up above the sea by formations almost wholly wanting in the South Island, so that the chance of finding drift deposits formed of the detritus of the deep-seated auriferous rocks, is much diminished.
I had not an opportunity of visiting Mount Egmont, but in February last, my assistant, Mr. Buchanan, visiting it principally with the view of examining its botany, also collected information respecting its geological features in the course of the ascent.
From his notes and specimens I gather that the surface of the cone is deeply grooved or fluted in radiating lines, and that in following up one of these grooves that the party encountered great difficulties in the ascent owing to the loose debris.
This groove was confined by precipitous cliffs 150 feet in height, which entirely prevented any ascent on the crest of the
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spurs, so that if any vegetation grows on these rocky ridges it must escape notice.
He describes the sections afforded in these cliffs as showing in the lower part of the cone a parallel disposition of lava floes, coinciding with the slope of the mountain, which is inclined at an angle of 37 deg. to the horizon.
The specimens of these parallel floes prove to be a close grained trachyte, speckled with a few minute crystals of hornblende, or augite. Above these hornblendic rocks, in his particular line of ascent, for more than 1,000 feet, the rock is massive grey trachyte or greystone, which he describes as several hundred feet thick, and having a tabular structure with numerous horizontal rents. This rock is continually falling away in large masses which, thundering down the side of the cone, are rather alarming to travellers, especially when, as is often the case, they become enveloped in dense fogs.
The rock, from the summit, is porous trachyte, of a yellow and reddish colour, but without any approach to the structure of pumice.
The rocks of the outer range appear to be similar to those at the Sugar Loaves, which are compact trachytes, rendered porphyritic by crystals of hornblende, which, sometimes mixed with glassy felspar, form crystalline aggregations of large size.
Mr. Buchanan was disappointed with the results of his expedition, as to the number and variety of the forms of vegetation, but before it is concluded that Mount Egmont is so much less interesting than had been anticipated, it will be necessary to make a thorough examination of the south-east or shady side of the cone also, as it is there that the conditions most favourable to plant life may be expected to prevail.
The account of Mr. Buchanan's trip, and the botanic results he obtained, will be found in a separate Report.
The following Report on the Petroleum of Taranaki is reprinted from the New Zealand Gazette of the 29th June, 1866:--
In the vicinity of Taranaki it appears that an exhalation of gas, and bubbles of bituminous matter, have been observed since the earliest days of the settlement, at about half a mile from high water mark, between the main-land and Moturoa, the highest of the Sugar Loaf Islands; and, according to Dieffenbach, "was whimsically attributed by the Maoris to the decomposition of an atua, or spirit, who was drowned there."
It was not, however, until November last, that any attempt appears to have been made to search for this oil, by boring or sinking wells on land, and as these
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experiments have to a certain degree proved successful, much attention has been recently attracted to this natural production, which it is hoped may yet prove a valuable and important article for export.
The petroleum is described as oozing in small drops from cracks and fissures in the rock that forms the Sugar Loaf promontory, but it does not appear that the solid rock itself contains any appreciable traces of oil.
All the rock specimens which have been transmitted for examination are either of the common superficial sand beds of the coast, or of a hard grey rock that proves to be the same trachytic breccia which forms the Sugar Loaves, and which can be traced only a short distance inland towards Mount Egmont. This rock, of volcanic origin, is composed of fragments of still older igneous rocks, ejected under the sea in the tertiary period, and cemented together by the felspathic mud which usually accompanies such eruptions.
Trachytic breccia of similar character is of frequent occurrence in other parts of New Zealand, either encircling districts where energetic volcanic action once prevailed, as rudely stratified masses of immense thickness, which overlie the marine deposits that were forming at the time of the eruption, or forming massive dykes that pierced through and consolidated among the sedimentary strata.
When the nature of this rock is taken into consideration, it is evident that the petroleum it contains can only be accidentally present, and must be originally derived from some distant source, and the most probable conclusion is that this rock only acted as a condenser and absorber of gaseous vapour produced by the natural distillation of deep-seated strata of carbonaceous matter.
It should be remarked that among the recent superficial deposits along the same coast, there are found considerable beds of lignite and decomposing vegetable matter, and though such deposits cannot account for the dissemination of the oil in the rock to a depth of 115 feet (at which depth I understand decided indications of its presence have been obtained), still it is well to bear in mind the existence of such superficial deposits, as it is quite possible that they may give rise to small quantities of bituminous oil, and to other indications that might tend to mislead explorers in searching for true oil wells.
The true source of the oil is most probably to be looked for in the coal seams that belong to the brown coal formation that is believed to form the base of the series of tertiary strata that extends under Mount Egmont, and the valleys of the Wanganui and other rivers which enter the sea along the coast between Mokau and Otaki.
This coal formation, which is probably not a continuous sheet, but occupies isolated depressions in the palaeozoic rocks, is overlaid by marine strata of various kinds, comprising clay shales, sandstones, and limestones, that were accumulated during a gradual depression of the land beneath the sea.
The volcanic eruptions seemed to have commenced at the period of the greatest depression, most probably with the eruption of the trachytic breccia that now yields the petroleum.
The volcanic action, at first submarine, was continued with the re-emergence of the land, becoming gradually more feeble and more localized, until the great cone of Mount Egmont was piled up in the atmosphere.
The total thickness of the submarine strata which in the deepest part of the basin overlie the brown coal formation, cannot be less than 2,000 feet, and to this must be added at least an equal thickness of submarine volcanic formations, above which rises the true volcanic cone of Mount Egmont to a height of 8,270 feet, composed principally of lavas and scoria beds of recent date.
Under this immense accumulation any brown coal beds that exist in the deeper part of the basin must have been subject throughout a lengthened period of time to the combined action of heat from the frequent injection of igneous dykes, and
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moisture from the percolation of water to supply that which was carried off in the form of steam during the volcanic eruptions; and one of the most probable results of the chemical action produced would be the formation of bituminous vapours that would ascend through the strata along lines occupied by dykes and fissures until they reached rocks sufficiently cool to cause their condensation into the form of oil.
In the foregoing endeavour to account for the remarkable fact of the presence of petroleum in the volcanic rock at Taranaki, it has been necessary to rely greatly on the analogy of geological structure which may reasonably be expected to exist between the district in question and other parts of New Zealand where similar superficial features prevail, as the information which has been derived from actual observation of the district is yet very limited.
It must be distinctly understood that there is no similarity between the mode of occurrence of the rock oil, so far as it has yet been found at Taranaki, to that which prevails in the oil-bearing districts in the United States of America and Canada; for although it is held by some geologists that in these countries the oil has also been produced by destructive distillation of coal seams, which are now represented by seams of anthracite coal, or have been wholly removed by denudation; still the nature and arrangement of the condensing rock has been very different, and this, of course, will completely alter the case so far as the practical search for petroleum is concerned.
In the United States the wells are sunk principally in very ancient strata--older, perhaps, than many of the slate rocks of New Zealand, but lying in an undisturbed and nearly horizontal manner over immense areas.
In Oil Creek Valley, according to Professor Draper, these strata consist of clay shale in beds of about one hundred feet in thickness, separated by layers of sandstone of twenty to thirty feet.
The borings are carried through alternate beds of this description to a depth of 400 feet before the oil is obtained plentifully, although it also exists in the upper strata in small quantity.
In this case it undoubtedly percolates through the more porous layers of sand rock, so that the process for obtaining it is like ordinary well-sinking, and a continued supply can be calculated on with considerable certainty.
In Canada the oil is also obtained much in the same way by piercing horizontal beds of limestone and shale of Silurian and Devonian age, the oil being found in the cracks and fissures of the former rock.
In that district there are also surface wells sunk in the superficial gravel and clays that have been saturated with the oil rising to the surface by natural springs.
The steady supply of rock oil from the American wells is no doubt due to the great extent and regularity of the porous strata in which it has been accumulated, and through which it percolates in the same manner as water supplying artesian wells.
The petroleum wells of Italy, Asia Minor, and the Crimea, have more resemblance to what may be expected in New Zealand, in so far that the oil escapes from strata of tertiary age and is always more or less distinctly connected with active or extinct volcanic agency.
Professor Ansted, in a recent article on this subject, describes the petroleum in the Crimea as springing from blue clay shales that underlie a crust of marine limestone of recent tertiary formation.
The petroleum wells up in the bottom of valleys that have been eroded through the limestone and so exposed the shales, and evidence of deep-seated chemical action is indicated by mud volcanos from which liquid mud accompanied with an escape of gas, slowly oozes and forms conical mounds and hillocks.
In these tertiary strata we have a marked resemblance to the older tertiary
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rocks of New Zealand which overlie the brown coal formation, and as I have already described, underlie the eruptive rocks of such volcanic centres as Mount Egmont; and I am inclined to think that the proper place to expect petroleum to occur in large quantities may be in connection with lines of dislocation at some distance from the centre of disturbance, and where the older tertiary rocks come up to the surface.
In the Taranaki district this would be to the north of New Plymouth, and in localities where perhaps there might be no surface indications excepting those which everywhere mark dislocations of the strata.
From the above considerations it is probable that in the neighbourhood of Sugar Loaf Point, where these explorations are being made, the boring will have to be carried to a very great depth before a constant or abundant supply of oil can be looked for, unless, as is extremely probable, when sinking through a rock which appears to be in parts saturated with oil, an open cavity or fissure be accidentally struck in which a large quantity of oil has been accumulated.
Such natural cavities are frequently struck when boring in the sandstone in America, the result being a sudden and forcible discharge of gas, oil, or water, according to whether the upper, lower, or middle part of the cavity be first tapped; but before long this spontaneous overflow always ceases, and then the ordinary method of pumping has to be resorted to.
If, however, the oil has been condensed in the fissures that traverse the trachyte breccia at Taranaki, from the form of vapour, and if it does not percolate freely through the substance of the rock, as it does between the layers of sandstone and shale in America, I fear that the pumping will not be of much avail.
The specimens of petroleum submitted have been carefully analyzed in the laboratory of this department, by Mr. Skey, and from the result of his examination it would appear that the nature and value in relation to other petroleum oils of the samples as yet obtained, has been somewhat over-estimated, and that they must only be looked upon as a good indication that really valuable oils may exist in the neighbourhood.
All the various samples which have been submitted have the same physical characters, having a dirty green colour by reflected light and being opaque except in thin films, when it has a deep red colour by transmitted light.
At 60 deg. Fah. it is quite limpid, and though at lower temperature it has considerable consistency, yet when reduced to 25 deg. Fah. it does not become solid.
It has a mawkish but not unpleasant odour, being very different in this respect from most rock oil, and is especially free from all traces of sulphuretted hydrogen gas.
Minute flakes of a white substance, probably allied to paraffin, float in the oil, and are gradually deposited, when it is allowed to remain quiet at a low temperature, nearly the whole of this solid substance becoming dissolved when the oil is gently heated.
The temperature at which the oil boils is 340 deg. Fah., and it does not appear to evaporate at ordinary temperature, for when exposed to the air it remains unchanged, neither thickening nor acquiring a skin on the surface.
Its temperature requires to be raised to 260 deg. Fah. before its vapour inflames; and even with a wick it does not burn so freely as common animal oils.
The specific gravity is very high as compared with other hydro-carbons, being no less than 962 (water being 1.000) or 14 1/2 degrees of Gesner's hydrometer scale.
There does not appear to be any instance on record of a rock oil having so high a specific gravity, the usual range being from .814 to .930 for crude oil.
It may be explained that all the varieties of petroleum are composed of carbon and hydrogen, and only differ in their quality according to the proportion which these two elements bear to one another, the heavier and inferior oils for illuminating purposes having the larger proportion of carbon.
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There is, therefore, no test of the quality of the oil which is so reliable and so easy of application as that of the specific gravity, and the above results are quite sufficient to show that the samples of oil examined have a much larger proportion of carbon in their composition than the common petroleum from which the kerosene of commerce is manufactured. This was still further proved by the examination of the oil by distillation, as in the production of kerosene.
A measured quantity of the crude oil was distilled with a very gentle heat which was gradually raised until 80 per cent. of the original quantity was obtained in the receiver, which is about the average proportion of kerosene obtained from the American petroleum.
The oil obtained, which had a faint yellow colour and pleasant odour, was of specific gravity .930, which is denser than the commercial proof that has been fixed for heavy lubricating oils (.927).
As the lighter oil would distill over first and at a lower temperature, the experiment was repeated, and the process stopped when 25 per cent. of the original quantity operated on had been obtained in the condenser.
The distilled oil obtained on this occasion had a specific gravity of .889, or slightly over the proof fixed for light lubricating oils (.881).
By further experiments it was found that the lightest oils that could be drawn over had the specific gravity of .874, and of this quality only 1/4 oz. could be obtained from 12 oz. of the crude oil after it had been carefully purified by filtration.
The next 1 1/4 oz. obtained had a specific gravity of .893, and the next ounce .9l7, which would give to the remainder of the 80 per cent. of distilled oil obtained in the first experiment a specific gravity of .941.
The first two samples were quite clear and colourless, but the last had a pale yellow tinge.
The average specific gravity of the 2 1/2 oz. thus obtained from the original quantity of 12 oz. was .900, or that of a lubricating oil of medium quality, while the oil left in the retort had a consistency of tar.
The ordinary density of the kerosene of commerce should be .819 (although it is often made lighter, in order to improve its colour, which, however, renders it liable to explode), and it has been found impossible to obtain oil of this low density from Taranaki petroleum.
The lightest distilled oil which was obtained burns freely with a wick, but has a lurid flame, and though not adapted for use in the ordinary kerosene lamp, might possibly be used in a lamp suitable for paraffine oil.
The residuum left in the retort when 80 per cent. of oil was drawn over was a hard brittle pitch, which can be obtained from the crude oil in the proportion of 73 grs. to the fluid ounce.
This pitch when further examined gave 28 per cent. of hydro-carbon evolved at a high temperature, and 62 per cent. of a lustrous vesicular coke, which contains 7.77 per cent. of ferruginous ash.
The general results of these results of these experiments may be tabulated as follows:--
One hundred parts of the crude oil, as obtained from the wells, having a specific gravity of .962, gives--
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It may perhaps be considered premature to form an opinion as to the prospect of these wells from the result of the analyses of the small samples yet obtained, which I understand are only collected as drippings from the boring rods and pumps; but it must be remembered that it is usual to strike the lightest oils first when boring, and it may be expected with more certainty in this case the oil has been condensed in the rock from a state of vapour, that the lightest and most valuable oils should be met with nearest the surface.
It, however, occasionally happens that petroleum obtained in one part of an oil-bearing district is much denser than in others, and sometimes even passes gradually into a semi-solid bitumen, so that the occurrence of this heavy oil at Taranaki does not necessarily indicate the total absence of the finer oils, but only that the locality in which the borings have been made may not be the most favourable.
A remarkable instance of this gradual change of the quality of the oil occurs at Baku, on the shores of the Caspian Sea, where the petroleum is obtained over a tract of country twelve square miles in extent, the strata being a porous argillaceous sandstone, full of fossil shells of the tertiary period.
The oil obtained from the centre of this district is very light and colourless, and accompanied by quantities of inflammable vapour; while towards the sides of the district it becomes darker in colour and more dense, and gradually passes into asphaltum.
In concluding these remarks, I would remind explorers for oil wells in New Zealand that petroleum is to be found in nearly all parts of the world, and has been recognized and worked from time immemorial for illuminating purposes.
The only novelty in connection with it in the present age is the discovery of large natural reservoirs, that seem to yield an inexhaustible supply, of a quality that can be purified by an inexpensive process, in districts where its presence had not been previously expected. The occurrence of mineral oil in New Zealand must not, therefore, be looked upon as an exceptional and uncommon phenomenon, but as one of the productions natural to a country where extensive deposits of carbonaceous matter have been involved in volcanic disturbances.
Whether mineral oil of fine quality has been accumulated in accessible positions and in sufficient quantity to exert a marked influence on the future prosperity of this country, is the problem now being solved, and even if the boring now carried on at Taranaki should not prove successful, the question will not be set at rest.
The presence of petroleum has been reported, and may be expected in many other parts of New Zealand; and now that attention has been directed to the subject I have no doubt it will be found, at least in small quantities, throughout both islands, wherever volcanic disturbances have affected deep basins containing tertiary strata overlying the brown coal formation.
Mention should not be omitted, however, of the circumstance that in the lower secondary rocks of New Zealand, which consist of sandstones and shales that have undergone great mechanical disturbance and chemical change, there are thin seams of graphite and anthracitic coal, and probably from these also there has been produced a certain amount of bituminous oils.
These beds, as yet discovered, are of very insignificant extent, and cannot have yielded a large quantity of oil in their conversion to their present state.
WEST COAST OF THE SOUTH ISLAND.
After my visit to Taranaki, the remainder of the season was devoted to the geological survey of the western districts of the Provinces of Nelson and Canterbury, principally with the view of
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tracing the distribution and extent of the auriferous and coal deposits.
The great extent of the area, and the natural difficulties which attended its examination permitted only of the most cursory investigation of these points being made in the short period at my disposal but the results obtained are sufficient to indicate the direction future exact survey should take.
Before proceeding to describe the principal points which have been established, I will briefly indicate the order in which the different districts were examined and the journeys which were made.
After a short exploration of the mineral ranges lying to the east of Nelson, I proceeded by Motueka and the Takaka Valley to Motupipi and Collingwood, where I examined the now almost abandoned Gold Fields, which, although the first worked in New Zealand, I consider by no means yet exhausted. This work, and the examination of the West Coast from Cape Farewell south to Kikurangi Point, including the West Wanganui and Pakawau Coal districts, occupied the months of November and December, after which I proceeded by Mackay's track up the Aorere River to the West Coast at the month of the Whakapohai or Heaphy River, crossing by a pass having an altitude of 3,000 feet.
This track was cut many years ago by the Government, and with very little additional expense might then have been made available for horses, but to do this now would involve a large additional expenditure. The natural facilities are, however, so great that it is certain sooner or later to be re-opened as a line of communication with the West Coast. The principal requirements are a few rough bridges over steep banked tributaries of the Aorere, a little side cutting on the ascent to the Pass, and the cutting of a track down the valley of the Heaphy River, which latter would require the largest outlay of any part of the road. After making the coast, a few difficulties would again have to be overcome before reaching the Kohaihai River, and also for a few miles where a track would require to be cut through the bush between the south end of the Karamea Plain and the Mokihinui River; but with these exceptions, there are no difficulties now remaining which prevent horses passing, I may almost say, from Bruce Bay to Collingwood, a stretch of coast equal in extent to that from Timaru to Blenheim on the East side of the Island.
While I crossed to the West Coast by the above-mentioned route, Mr. Hacket, who was engaged to assist me during the summer,
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after surveying the Plumbago Mines near Pakawau, returned by way of Motueka to the Wangapeka River, there to await till I returned to the east side of the mountains by following up the Karamea River. Inclement weather and the flooded state of the rivers prevented my doing so, and I was constrained to follow down the coast to the Buller River. Seeing no prospect of an abatement of the floods, on the 10th of January, 1867, I returned by steamer to Nelson, and from thence rejoined Mr. Hacket at the appointed rendezvous on the Wangapeka River.
The examination of the Mount Arthur Ranges, and the sources of the Wangapeka, Batten, and Karamea Rivers occupied three weeks. Having examined the features of this district with considerable care, I may take this opportunity of stating with regard to the supposed existence of easy passes through the ranges at this point to the West Coast--which I understand has recently excited some controversy in the Province of Nelson--that the reports of Mr. John Rochfort on this subject, published in 1863, convey a clear and accurate account of the country in question. I do not know of any pass by which an easy or inexpensive road could be made from either the Batten or Wangapeka Rivers to the Karamea, for although there are several spurs of easy ascent from the eastward, the descent to the valley of the Karamea is everywhere extremely difficult.
The most useful track for the diggers, although it would be only available in the summer, would be one leading round the north flank of Mount Arthur to what is known as the Salisbury Plateau, where there is some prospect of a gold field, and from which a descent might be effected to the north branch of the Karamea without much difficulty. For the purpose of reaching the south branch of the Karamea, the track marked out by Mr. Rochfort from the head of the Wangapeka is undoubtedly the best, and has been frequently travelled by prospectors during the past summer.
At the source of the Karamea I again separated from Mr. Hacket, who returned to Nelson, and thence by steamer to Grey-mouth, while I crossed to the source of the Mokihinui River and followed it to the coast. This was a line of route attempted by Mr. Rochfort when searching for a pass to the Lyell River in 1863, but he abandoned it a few miles from the source of the Mokihinui.
I thus passed through one of the most rugged and impracticable districts I have examined in New Zealand, and though
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a very short route, and opening up some good land, and, I think, auriferous patches of country, it would require too large an expenditure to render it available even for foot travellers; especially as those portions of the valley which will probably attract diggers can be reached with greater facility from the Karamea Plains and source of the Little Wanganui River.
An accident which disabled me at this stage of my explorations, caused a considerable loss of time, so that I was seventeen days in reaching the Buller River from the source of the Mokihinui; and it was not till the 7th of March that I had completed the examination of the Mount Rochfort Coal Field and the surrounding districts--including the gold diggings at Pakihis and Fox's--(Charlestown and Brighton). The time devoted to this examination, though quite disproportionate to the interests which will be involved in the future development of this district, was sufficient to enable me to form a confident opinion respecting the importance of its resources.
From the Buller I travelled to Greymouth, and from there visited the surrounding districts as far interior as the source of the Little Grey. The survey of the Davy Mountains occupied a long period, but the district is so extensive, and the geology so complicated that the result was merely a preliminary examination of the coal formation.
In the month of April, through the courtesy of His Honor the Superintendent of Canterbury, I joined the party of the "Westland Commission," and had an opportunity of seeing the coast, and touching at various points as far south as Milford Sound. A great part of the coast thus visited can only be examined in this manner, as a traveller along the beach would acquire no correct idea of the features of the narrow strip of country which lies between the sea and the crest of the mountains.
After visiting the various gold diggings on the West Coast I crossed by the mail road to Christchurch, and thence overland by the inland route between the Kaikoura and Spencer Mountains to Blenheim and Picton, and returned to Wellington on the 23rd May, after an absence in the field of eight months.
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MARLBOROUGH AND EASTERN NELSON.
In November last Mr. Buchanan was instructed to proceed to the Kaikoura Mountains and the East Coast of the Province of Marlborough, for the purpose of collecting specimens of fossils, rocks, and plants, from those portions of this district which have hitherto received hardly any attention from observers.
After an expedition extending over nine weeks, in the course of which he ascended the Lookers-on or seaward Kaikouras, and examined the valleys and coast line as far south as Motunau, in the Province of Canterbury; he returned with a large number of valuable specimens which are deposited in the Museum.
From an examination of these specimens I find the following formations to be represented in this district:--
1. Post Tertiary, sands and gravels, forming terraces along the courses of the rivers, and fringing the coast. Occasionally these gravels cover ancient forests, which, in some cases, are shown by sections on the sea coast to be submerged below the present sea level.
2. Pliocene.--(A.) Newer great terrace drift formation. (B.) Older blue clays of marine origin containing abundant fossil remains of mollusca and cetaceans, many of the former being of species still living in the neighbouring seas.
3. Miocene.--(A.) Red and white crag limestone, fossiliferous. (B.) Clay marls and green sands. These are marine formations, characterized by a proportion of fossils, mostly of forms now extinct. (C.) In certain districts the above are underlaid by the brown coal formation.
4. Cretaceo-Tertiary.--(A.) Chalk marls, evidently of marine origin, but containing few fossils. These marls pass into pure chalk, and even crystalline limestones in some cases. (B.) Ferruginous clays, with septaria, containing upper secondary fossils (the Amuri beds). (C.) Sandstone and grit with plants, representing the West Coast Coal Fields, are present probably at Motunau.
5. Lower Secondary.--Indurated green and brown sandstone and shales (corresponding to the Richmond series near Nelson). These form lower ranges, flanking the Kaikouras; no fossils were obtained, but the marked lithological character of the beds leave no doubt as to their presence.
6. Schistose rocks of various ages, from the Maitai slates to the foliated mica schist.
6. Hornblendic rocks, associated with serpentine bands.
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Mr. Buchanan's notes on the geology of the district he examined are appended to this Report.
COAL FIELDS. 3
The Coal Fields of mesozoic age on the West Coast of the South Island, which were examined during the past summer, will be described under the following groups:--
1. Pakawau Field.
2. Buller, or Mount Rochfort Field.
3. Grey River and Mount Davy Field.
4. Karamea and Lyell Mountains.
Without the assistance of illustrative sections and diagrams, it is impossible to convey more than a general impression of the extent and value of the Coal Fields, and of the exceedingly anomalous circumstances under which they occur.
So named from the locality where the first attempts were made to open Coal Mines, in a gorge that cuts through the range of hills that run out to Cape Farewell. At this place, various drives have been made, shafts and borings sunk, and a tramway constructed for several miles, but without any successful results.
The gorge or valley where these works are situated, lead to the head of West Wanganui Inlet, which is an extensive but shallow harbour, opening on the West Coast, and where the coal has also been worked to a limited extent.
The coal-seams exposed at what is known as the "Collingwood Mine," are the latest discovered, and belong to the same formation as those which have been partially worked at West Wanganui Inlet and Pakawau. Extending from the hills above the Aorere Valley to the West Coast, and from Cape Farewell as far South as the Patarau River, this formation has a superficial area of about 30 square miles; but it is interrupted by an island-like mass of granite, which rises through it to a height of 1,700 feet above the sea-level at House-roof Hill.
Its thickness is about 1,500 feet, consisting of beds of clay marl, sandstone and conglomerate, with traces of fossil vegetation in the form of leaves and stems of plants, and carbonaceous shales,
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SECTIONS SHEWING THE RELATIVE POSITION OF THE MOTUPIPI AORERE AND WEST WANGANUI COAL FORMATIONS.
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which occasionally pass into coal seams. The fossil flora is the same as that found at the Buller and Grey River Coal Fields; and there is no doubt that the extensive, though detached Coal Fields on the West Coast, all represent nearly the same geological period.
The chief peculiarity of the formation in this particular district, is the remarkable tendency which the strata have to change suddenly in their mineral character by what is termed false bedding; the same stratum frequently passing, in the distance of a few yards, from a sandstone into a clay shale or a coarse conglomerate. This is a sure indication that the deposits have been formed through the agency of powerful but, intermittent currents, and renders it probable that the coal was derived from drift wood originally. In this respect the coal formation of this district resembles that at Cape Patterson, in Victoria, in which many unsuccessful attempts have been made to discover workable seams.
The base of the formation, or where it rests on the older slate and granite rocks of the district, has only been observed at the Collingwood Mine, where coarse conglomerates are exposed at 800 feet above the sea, resting on mica schist rocks, and dipping at 12 deg. to the westward, or into the face of the hills, the upper part of which, to an additional height of 1,500 feet, are composed of the coal formation.
Following round the scarp of the hills to the south, in the Kaituna Valley, the outcrop is at a still higher level, the dip being in a N.W. direction. If the same hills are followed to the North the coal-bearing strata are found to reach the sea level in the Pakawau Gorge, but at that place they are much faulted and broken up so that it is difficult to make out their exact position.
Round the cliffs of West Wanganui Inlet the upper part of this formation is well exposed in a series of low cliffs and in the coast range and also at Cape Farewell it is seen to dip under the limestone of Miocene tertiary age.
At West Wanganui the base of the formation is below the sea level, but the strata are denuded to a sufficient depth to expose the coal beds, which I believe to be the lowest 300 feet of the formation. No coal seams have yet been discovered in this field of greater thickness than 3 feet, as will be seen from the sections observed at four distinct localities which are from 4 to 6 miles apart.
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First: Collingwood Mine.--In the hills on the west side of the Aorere River at 1,000 feet above the sea level:--
Conglomerate with carbonaceous markings 30 feet 9 inches.
Giving 6 feet of coal in a thickness of 90 feet of strata.
Second: Pakawau.--In the gorge leading to the head of the Wanganui Inlet. The strata are very much disturbed in this locality, and so imperfectly exposed that the section must only be considered a rough approximation. There appears to be 5 seams, giving a thickness of 7 feet 6 inches of coal in 102 feet of strata, viz.:--
Third: West Wanganui Mine.--The coal in this locality is exposed in the mud flats at low water, and dips rapidly below the sea level under the range of hills that separates the inlet from the sea coast:--
Being 6 feet of coal in 19 feet 4 inches of strata.
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Fourth: At the left arm of the West Wanganui Inlet the following seams are visible, rising into the hill to the eastward at an angle of 10 deg.:--
Being 5 feet 6 inches of coal in 66 feet 4 inches of strata. From the comparison of these sections it will be observed that while there is a very great diversity in the arrangement and relative thickness of the coal seams in different parts of the field, there is a general agreement in the total amount of the carbonaceous matter present in each case.
The most accessible portion of this Coal Field, and where there is best chance of finding workable seams, is certainly in the face of the hills south of Pakawau Gorge, where the base of the formation can be examined.
Taking the great band of conglomerate as a guide, it would be easy by a careful search to trace the outcrop of the coal seams in each successive gully from the Collingwood Mine to Pakawau, and probably still further to the northward, and thus to discover the most suitable portion for opening a mine.
I fear the position of the coal at the Collingwood Mine is too inaccessible, and that the first expenditure required for the works necessary is not warranted by the present indications, as nothing under a five feet seam would yield the coal at a sufficiently low cost to be remunerative under such circumstances.
Where the attempts have been made to open mines in the Pakawau Gorge, at which place the position, with reference to deep water and access by easy gradients, is all that can be desired, the strata are, unfortunately, very much disturbed by slips and faults which cause great irregularity in the distribution of the seams.
Were the search conducted on the hill-slope, at the entrance to the valley on the South side, I consider it would lead to better results, as not only will the seams be less disturbed in that locality, but if found, will be in a position that will not require them to be
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worked by shafts and machinery, which extra expense would be required in the Gorge, as there the seams would be found dipping below the water level.
At West Wanganui Inlet the coal is found in many places besides those already mentioned, but has only been worked at the mine at the South arm, where it is excavated from the outcrop of the seam in the mud flat at low water, only in sufficient quantity to supply vessels when they come for a cargo. No stock being kept on hand great delay frequently ensues, as, if a favourable wind for leaving the harbour is lost, a vessel may be detained for many weeks. Although only four men are engaged in mining, a large part of their time is necessarily unemployed owing to this system of working.
To work the coal on the side of the Inlet where the present mine is situated, a shaft and pumping engine will be required after preliminary borings have satisfactorily proved the existence of the seam to a sufficient extent; but such works, I believe, will be found to involve an outlay disproportionate to the value of the seams.
On the opposite side of the Inlet, where the beds are rising into the hill, prospecting for coal-seams is only a matter involving a diligent and prolonged search. Even with the very limited time at my disposal, I found several places where the indications are equally as good as those at the place where the coal is at present mined.
Without entering for the present into further details as to the best method of prospecting this Coal Field I may state, as a general result of my examination, that although much inferior in extent and value to the Coal Fields further to the South, this district is capable of yielding a large quantity of valuable coal, and if opened up with caution and economy, will afford profitable employment to labour at a future period.
BULLER OR MOUNT ROCHFORT COAL FIELD.
The next coal-bearing area on the West Coast, South of the Pakawau Field, is that occupying a narrow strip from the Karamea Plains to within a few miles of the Buller River, having a length of about forty miles by about seven miles in width. The coal occurs within this district at different altitudes from the sea level,--as at the Mokihinui and Pakawau Rivers--up to an elevation of 3,000 feet, as in Mount William and Mount Rochfort. The coal-
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seams in the latter position were first discovered in 1860 and reported on by Dr. Haast and Mr. James Burnett, the latter gentleman having prepared a series of maps of the district, which were placed at my disposal, for incorporation with the Geological maps, by the Nelson Government.
In the Mount Rochfort District the coal is associated with a formation of quartzose gravels and grits, having a thickness of from 200 to 300 feet. Several seams of coal have been described, but I could not satisfy myself of the existence of more than one main seam of from six to ten feet in thickness. The formation rests on a very irregular surface of the slate and granite rocks, the irregularities having been produced by dislocations subsequent to the deposit of the coal. Notwithstanding that these dislocations or "faults" are of great extent and magnitude, the vertical displacement in some instances being as much as 1,200 feet, it is most probable that they are due rather to the local subsidence of portions of a formation that had been raised in mass, than to an unequal exercise of the, elevating force in the first instance.
It is obvious this consideration is one of primary importance in tracing the extension of these Coal Fields and discovering the occurrence of workable seams at low elevations; and, from what I observed, I am inclined to expect that, under a formation of brown sandy shale and septaria clays which skirts the seaward base of Mount Rochfort, the coal seam may probably occur as that on the summit of the range though it may be deteriorated in character.
The manner in which the coal is exposed in Coalbrook Dale has been so frequently and well described, that I need not for the present state that I am able to confirm what has been said respecting its purity and value. Its extent has perhaps been over-estimated, as it is not very clearly demonstrated that it extends over the whole area of the Mount Rochfort Plateau, as has been stated by Mr. Burnett as the basis of his calculations in his Report to the Provincial Government of Nelson.
Besides a few excavations in this seam at Coalbrook Dale, the only work performed in this district is the boring which was attempted at the western limit of the plateau, but which did not lead to any useful result, principally owing to the position selected for the trial not being favourable. If any further trials by boring are performed I should be inclined to recommend a position at a lower altitude by several hundred feet, and a few miles nearer the
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Buller River, as there is an evident disposition in the plateau to form a trough-like extension in that direction, in which the coal may be expected to occur at the lowest level.
The only obstacle to the working of the valuable coal in this district is the long and expensive land carriage that would be required between the localities where the coal is at present known, and the shipping place at Westport; but the Buller River is so much superior as a port to any other place on the North-west Coast of the Island, that I think a considerable expenditure in exploration for valuable seams within reach is. in this instance warranted.
It is very probable that as there is now a large number of gold diggers engaged in prospecting this district accident may lead to the discovery of a locality where the coal can be worked with greater advantage than any at present known.
Twenty miles North from Westport the coal is found at the sea level at a distance of half a mile from the mouth of the Nakawau River, and in a very accessible position for land carriage. The seam is at least nine feet thick and lies conveniently for being worked, but having acquired its present position as portion of a large landslip, involving an extent of at least 30 acres, the coal is of the friable sooty description usually found on faulted ground. However as there as is no doubt that it is the same as that on the plateau above, it may improve in quality on being worked, and a considerable quantity of valuable coal be obtained.
The coal mine which was opened some years since at seven miles from the mouth of the Mokihinui River is also in a very favourable position as regards level, but involves a long land carriage to a port only available for very small-sized vessels as compared with those that can enter the Buller River. The quality of the seam is reported to be good, but owing to the flooded state of the river at the time of my visit I was unable to inspect it.
GREY RIVER AND MOUNT DAVY FIELD.
The Coal Fields already mentioned have more a prospective than an immediate value in the present state of the West Coast District; but the development of the Mount Davy Coal Field will have a practical influence on the resources of the country at the present time.
The area occupied by the Coal Mountain in this instance is not so great as that of either the Pakawau or Mount Rochfort Fields; but the value and accessibility of the coal-seam gives it a
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superior importance. The best coal appears to be in one main seam, associated with micaceous sandstone and grits containing plant impressions, and small carbonaceous layers. It is best seen at the Brunner Mine, in which the coal has been followed on the level for 700 feet, and likewise explored to the outcrop; the total length of the galleries and chambers, from a survey which I made, being nearly 3,000 feet.
The thickness of the seam varies from fifteen to twenty-three feet, and is contained between a roof and floor of solid grit, which enables it to be worked with facility, timbers being required for the support of the roof only in a few places where it had a tendency to flake.
The coal formation rises, at an angle of 12 deg., in an easterly direction from the water level to an altitude of at least 2,000 feet in the Mount Davy Mountains, and extends to the North for a distance of seven miles, intersecting the coast about twelve miles North of the Grey River. Any coal within this area can, of course, be worked "level free," as in the case of the present mine, which system involves the least possible working expense, all excavations being in marketable coal, and no outlay being required for hauling the coal or draining the mine.
Westward from the mine the coal dips under strata of sandstone and septaria clays, which are again overlaid by indurated chalk marls, with fossils characteristic of the upper secondary period, principally Echinodermata (Sea-urchins), ten species of which have already been distinguished and figured. Under a considerable portion of this area, coal will hereafter be worked by shafts; but the coal above the water level will be the first to deserve attention.
To the eastward, we find the coal formation cut off suddenly by a great break, or fault, similar to that which limits the extension in the same direction of the Pakawau and Mount Rochfort coal seams.
The coal is not, therefore, likely to occur in the valley of the Grey River above the present coal mine; notwithstanding that from the manner in which the river has cut its channel, a series of slips have given rise to a local easterly dip of the strata, as seen in the section on the South bank; but that this is only apparent, is proved by the abrupt replacement of the coal formation by the palaeozoic slates on the same side of the river, half a mile above the mine.
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The facilities for working the coal on the South, or Canterbury side, are not so great as those at the present mine, but the southern extension of the field in that Province is not yet ascertained, and it is probable that even a larger area will prove available for working by shafts on the South than on the North side of the river. It is, therefore, most desirable that a careful survey should be made, with the view of testing this point, as the trials hitherto have only been short drives into what is evidently faulted ground, and throw no light whatever on the subject.
The Brunner Mine is not at present worked with that confidence and energy which I think it deserves from the indications which it affords of proving a successful adventure.
The output of the coal is not equal to the present demand at the port, being controlled by the defective system of transport from the mine by barges. In the ordinary state of the river, the barges can only take a very small quantity of coal, rarely delivering more than 40 to 50 tons a day, and involving a very large expenditure of labour. A survey has been made for a railway from the port to the mine, a distance of seven miles; and, from the favourable nature of the country, if constructed with economy, the line should not cost more than £20,000, which is a very small outlay, considering that it is the only heavy expenditure required to secure the regular supply of coal.
Although I have great confidence in the persistence of this. coal seam, before expending even this small sum I should like to see the heading of the main drive carried far enough to pass under the brow of a precipitous cliff which rises at a distance of three or four hundred yards behind the mine, as this cliff may possibly mark a fault in the strata and thereby limit the extension of the coal, or at least reduce the facilities for working, in a large portion of the leasehold of the Company.
Provided that no such fault occurs, I see no reason for doubting that on the most moderate computation this property should yield 5,000,000 tons of coal.
The expenses of working the mine are so small that the coal should be delivered at Greymouth at a very moderate price, if the working were carried on more extensively, and a steady market for the coal established.
The seam of coal is pure and homogeneous, and possesses the property of caking with such facility that the whole quantity excavated can be utilized, so that no labour is unproductive, as is
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the case in mines where stone bands, shales, and other worthless matter have to be excavated along with the coal. As the associated strata of sandstone and shale have a regular stratification unlike those at Pakawau, we may expect the valuable quality of purity in the coal seam to be persistent over a large area in this district.
It is necessary, at the same time, to be guarded in acting on this conclusion; for although we can determine the extension of the coal formation by superficial geological survey, the extent and quality of the actual coal seams is only a matter of inference.
I attach great importance to the successful working of the Brunner Mine as bearing on the future development of the coal trade in the Colony, and may state the following points in its favour, as being in my opinion sufficiently established:--
That the coal is a very valuable description of fuel, adapted both for steam and household purposes.
That its purity and good quality is maintained throughout a seam of very unusual thickness as compared with coal seams mined in other parts of the world.
That the position of the mine enables it to be worked at a minimum outlay.
That the cost of transport to the Port involves a very small expenditure in comparison with the value of the property.
The only disadvantage under which the coal will be brought to the market arises from the nature of the bar at the mouth of the Grey River, which will limit the carrying of coal to vessels of very small size, and thereby greatly increasing the cost of freight. Notwithstanding this expense, I think that from the other conditions being so favourable that this valuable coal should be delivered, say, in Cook Strait at from 20s. to 25s. per ton.
KARAMEA AND LYELL MOUNTAINS COAL FIELD.
This is a large and imperfectly examined coal-bearing area in the interior of the western district of Nelson. Extending South from the Buller River it is found in detached trough-like depressions among the mountains towards the source of the Wangapeka, Karamea, and Mokihinui Rivers. It then rises to the south-west and forms the summit of the grassy flat-topped ranges known as the Merino and Lyell Mountains. It is separated from the coal fields nearer the coast by mountains of granite and slate. The formation consists of four groups of strata, and was best seen in a vertical section of a mountain at the source of the Mokihinui River. The summit of this mountain is 4,700 feet
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above the sea, and the section showed the structure for 1,800 feet from the summit. The upper beds are indurated chalk marls, like those at Greymouth Gorge, but in them no fossils were detected. Under the marls is a group of grits and sandstones, which again rest on a thick series of septaria clays, in which I found mesozoic fossils. The lowest member reached is a group of brown sandstones containing seams of coal. Sometimes the above-mentioned marlstone is replaced by the pure crystalline limestone, as at the source of Rolling River.
At the Batten River the formation presents pretty much the same succession as that which prevails in Mount Davy Field. At this place there are several seams of coal, but the quality is very inferior one sample having on analysis proved to consist of 27 per cent. of oxide of iron, combined principally with bituminous matter. No important seams have been found as yet in this field, but this is easily accounted for by the difficulty and inaccessibility of the country which it occupies, while the abundance of fossil plants at the base of the formation and the distinct manner in which the sandstone, clays, and grits appear, in most cases, to have been separately deposited, argues well for the existence of good coal seams.
As the access to the field will be by valleys draining to Blind Bay, the discovery of available seams will be a great benefit to the older settled districts of the Nelson Province and to the Port of Nelson.
The above sketch of the principal coal-bearing districts of the Western Districts of Nelson is only intended to show the confidence I have in their capability of future development; but, as I have already pointed out, it is impossible to convey a clear idea of the complicated manner in which the strata are distributed without the aid of sections.
The distribution of the gold-bearing alluvium on the West Coast is very different from the manner in which it occurs in the Gold Fields of the Province of Otago 4 where it rests in the hollows in the surface of schistose rock, which is either the auriferous matrix or belonging to a still older rock formation. On the other hand, the gold drifts on the West Coast, in the majority of
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instances, rest on the surface of the most recent marine tertiary rocks in New Zealand, having, in fact, being carried out from the mountains by the rivers, and deposited on a gradually changing coast line. They thus have a general distribution parallel to what was the western shore of the island at the epoch of their deposit; and by tracing the successive lines of elevation, and allowing for the consequent changes which have occurred in the direction of the drainage channels of the country, we are enabled to form an opinion as to the extent and position of the auriferous "leads."
The distribution of these gold drifts has already been treated by Dr. Haast, in his Reports on the West Coast Gold Fields, published in 1865; and the development of the diggings since that date has completely borne out the general correctness of the views he then suggested. These have not yet been practically applied to assist the miners in their search for new auriferous "leads;" but there will be no difficulty in preparing a map founded on the careful topographical surveys at present being made by the Survey Department at Westland, which map should show, not only the existing workings, but also the direction of their probable future development.
The auriferous alluvium on the West Coast may be classed under four groups:--
First: The earliest formed and most elevated of these drifts rests on terraces composed of the marine tertiary strata, where they have escaped denudation by the streams descending from the mountains. Extending in a north-easterly direction, parallel with the main chain of the mountains, "leads" of this class pass into the Province of Nelson; and have been traced as far as the high terrace land at the source of the Little Grey. The gold from these "leads" has a coarse scaly character, and is found at a varying depth from the surface in red earthy gravels, resting on a denuded surface of the marine clays. These "leads" have not an uniform level, but increase rapidly in altitude above the sea as they are followed to the North, and may be looked on as the first formed drifts in the great valley which extends through the country South from Blind Bay, and is cut off obliquely by the sea coast between the Teramakau and Okarita.
Second: The second group of gold diggings are those in the beds and alluvial terraces of streams which intersect the first-mentioned "leads," and, by a natural sluicing operation, have re-deposited the gold in a concentrated form by removing a large
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proportion of the lighter materials. The diggings at Ross and Kanieri are the best examples of diggings of this class which as yet have been worked.
Third: The third class are the beach terraces, which extend to an altitude of 220 feet, and mark several changes in the level of the shore line within a comparatively recent geological period. In this group also must be classed the gold deposits forming on the present coast line by the action of the surf and currents, which distribute along the shore the fine gold brought down by the rivers.
Fourth: The gold alluvium of the fourth class is that formed by the erosive action of running streams on the auriferous rocks, and affords what are termed sluicing diggings. These are of two kinds, according to the nature of the matrix from which the gold has been derived. On the Otago Gold Fields I believe that most of the gold has been derived from schistose rock which has undergone mechanical and chemical metamorphism. Similar schistose rock occurs along the western slope of the mountain range of Canterbury, and it is an important point in considering the future discovery of gold deposits, that the continuation of this range must be looked for in the Spencer Mountains and mountains that trend towards the Pelorus Sound, rather than in the mountains in the north-west part of the Province of Nelson, as the latter are altogether detached in a geological sense from the central chain. In the district lying West of the main range thus defined, there is a great diversity of geological formations, such as granite, slates, schistose rock, palaeozoic and mesozoic sandstone, intermixed with plutonic rocks, both basic and siliceous in character.
A district having this geological structure is peculiarly favourable to the development of mineral "lodes," and several have already been discovered yielding copper, lead, silver, chrome, antimony, and gold.
The "lodes" which are associated with a felspathic and quartzose rock, and a basic rock containing varieties of the hornblende minerals, combined with mundic or iron pyrites, appear to be those which are auriferous, and thin irregular veins of quartz accompanying such "lodes" constitute the second form of auriferous matrix which has been found in New Zealand. These "lodes" occur in detached localities, especially in the range of mountains extending from the North side of the Grey River to Cape Farewell, and each of these localities may be expected to
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form a centre from which gold in greater or less quantities has been distributed in the alluvium. From this cause the diggings in the north-west district of Nelson have a peculiar and capricious distribution, there being no connected system of auriferous drifts, or similarity in the conditions under which the gold is found.
Nearly all the diggings North-west of the Grey River belong to the fourth class, or sluicing diggings, where the miners have to work in the beds and terraces of streams; of the principal exceptions are Collingwood, where there appears to be a local development of the older gold drift like that in Otago; the Sherry River Diggings, near Whangapeka; and the Canoe Creek terraces, seventeen miles North of the Grey River; in both of which the "bottom" is the same marine clay as at Hokitika, and the fine or "drift gold" diggings in the Pakihis, extending along the West Coast as far as the Karamea. Sluicing diggings cannot be expected to support a concentrated population like the more steady "leads" along the western flank of the main range; but there is no doubt that they will yield a large return of gold to the enterprising diggers who are able to prospect such a rough and difficult country.
I do not think that gold diggings are likely to be discovered to the North of the Grey River which can be worked to advantage by large bodies of men, unless in the valley of the Buller River, or between that river and the Spencer Mountains, where there is a large district not yet prospected lying in a direct line extended from the best "leads" further South.
Latterly the diggers have been diverted from following this line by attractions offered by the fine gold "leads," as at Fox's and Pakihis; but,--except at Canoe Creek, where there is a patch of old terrace drift with coarse gold, and at Waimongaroa, twelve miles North of the Buller, where the stream cuts through a patch of rich "lode" ground underlying the coal formation, and where a considerable quantity of rough nugget gold has been obtained, and, lastly, the small quantity of rough gold obtained at an immense cost of labour, and time by sluicing the beds of such rivers as the Karamea and Mokihinui,--there has been no indication of the occurrence of anything but fine drift gold along the coast North of the Grey River.
The immense quantity of fine gold, the extraction of which is at present employing a mining population of at least six thousand persons on the Pakihis along the coast north and south of the Buller, is, however, suggestive of the existence in the
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interior of a large quantity of coarse gold, as an equivalent to the proportion of gold in fine particles.
These Pakihis are depressions in the shingle flats once occupied by lagoons or river courses, but are now covered by peaty matter carrying a poor heathy vegetation. The gold in these Pakihis is obtained from layers of well-washed shingle, such as is seen along the banks of existing rivers, and also from the vegetable soil on the surface, in positions where it might have been deposited during freshets. It is exceedingly fine in the grain, and is easily suspended by water in motion; and, notwithstanding the great physical changes which would apparently be required to account for such an alteration in the drainage system of the country, I believe that this fine gold must have been deposited by the Buller and other rivers, and that it is not due to the extension up the coast of the surf-carried gold derived from the "leads" along the main range in the South.
The Buller River, and its tributaries, have cut through a very large area of terrace country, and if the fine gold of the Pakihis has been derived from the natural sluicing of these terraces there must be some very rich diggings of the second class awaiting the miners in the district in question.
The similarity in the chemical nature of some of the "lode" rocks at Waimongaroa, Batten River, and other places in the north-western ranges, to the auriferous rocks at Coromandel and the East side of the Thames Valley, and also near Cape Terawiti, in the North Island, leads to the expectation that gold may be found associated with the pyritous "lodes" in a continuous line throughout the North Island. I think there is no doubt that these "lodes" have their origin in the escape of the thermal waters, as the constant association of sulphurets in the "lodes," and the manner in which the superficial strata have been silicified, the deep-seated strata deprived of their silica, points clearly to their agency.
The view that thermal springs are the vehicles for the translation of the gold agrees with views recently advanced in the transactions of the Royal Society of Victoria, and if the experiments originally made by Mr. Daintree, and lately verified by Mr. Wilkinson, are correct with respect to the deposit of gold from solution by contact with organic matter, it is quite comprehensible how gold would only be deposited when the waters reached near enough to the surface to be within reach, of the
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necessary organic matter, and might fail to be reduced if the thermal waters escaped under the sea, or beneath marine tertiary limestone, or other rock possessing a different chemical nature or free from organic matter.
If this view be correct it may explain the relation which frequently appears to occur between the plentiful occurrence of gold in the alluvium derived from areas where the brown coal has been denuded from the schistose rock, notwithstanding that there is no gold in quartz gravel apparently derived from the same rock, but associated with the brown coal in a manner proving that they are of contemporaneous formation, thus indicating perhaps that the brown coal, or solutions derived from it, took part in the subsequent deposit of the gold in the interstices of the underlying rock.
The absence of gold from quarts reefs of miocene age, as has been demonstrated by Mr. Selwyn, Director of the Geological Survey of Victoria, may be due to the prevalence of marine conditions up to that period, and the absence of the necessary re-agent for the reduction of the gold in the form of an abundant supply of decomposing organic matter consequent on terrestrial conditions.
I would have it clearly understood, however, that these views only affect the distribution of the gold in the second or pyritous form of matrix of New Zealand, which appears to be common to districts in both Islands, where, in most cases, thermal waters are still escaping. I assume that the action of the hot springs is merely to translate the gold and other minerals to more superficial portions of the crust of the earth; and this hypothesis would require modification before it could be applied to such gold fields as those of Otago, where we have a great area of metamorphic rock apparently more or less auriferous throughout.
The discussion of these views must be reserved until the facts I have in support of them can be more fully advanced, but sufficient has been stated to indicate that although the richest gold fields of New Zealand may have already been discovered and worked, there still remains a large area of unexamined auriferous ground. If the present mining population were more equally distributed over the various gold fields, the yield of gold, which has fallen off considerably, would probably again for a time reach its maximum. There is no doubt that the time lost in changing from place to place in the hope of securing good claims at new "rushes," is the principal cause of the fluctuation in the yield of gold. The
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inducements for this continual migration are rapidly becoming fewer, and unless some great attraction arises in other parts of the world to take the miners from this Colony, in a few years the gold fields will have acquired a permanent population, scattered throughout auriferous districts of Otago and the West Coast, combining mining with other pursuits; and though the miners be individually content with a smaller return than at present for their mining labour, there will be produced at least an equal yield of gold for the Colony as a whole.
BY J. BUCHANAN.
In communicating the following notes, I must premise that many of the names of rocks and rock formations are to be considered as provisional, until the collections have been examined at the Museum.
The long continuance of wet weather prevented much time being taken up with Botanical collecting, and more attention was paid to working out geological sections wherever it could be done, and the purpose of the following notes is to explain the sections and accompanying map.
The geology of Marlborough appears to be very simple. To the East of the Wairau Valley and South to the Conway River there will be found a great development of palaeozoic diorite schists rising like islands from the marine tertiaries along the coast. South of the Conway River, passing through Nelson into Canterbury, the brown coal formation begins to appear, between the old schists and the marine tertiaries, adding more interest to the study of the district.
The sequence of the different formations is shown in vertical section No. I. (See Map.)
The diorite and clay schists, which form the higher land of the district, occupy the greater part of the surface area. The strike of these rocks is generally N.W., with a westerly dip of about 75 deg., but near Squally Point the strike is N.E., with a westerly dip of 80 deg. In Taylor's Pass again, where there is apparently an anticlinal line of fault, they dip both to the S.W. and S.E. 75 deg., and also in the valley between Blenheim and Picton there is another anticlinal line of fault, with the dip at the Blenheim end N.W. and S.E. 45 deg., whilst at the Picton end the
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dip is S.W. and S.E. 50 deg. to 75 deg.; in this case, and probably also in Taylor's Pass the fault is much wider at one end than at the other.
To the South of the Wairau Valley, the greater part of these older rocks are dioritic sandstones and slates alternating; but in some localities, such as the vicinity of Blairoch Creek on the Awatere River, a variety of rocks are found, such as felstone, serpentine, and green jasper, along with fine specimens of actinolite and hornblende. 5 Higher up the Awatere, a great band of variegated diorite intersects Mount Mouat, taking in the whole of the Stephen Mountains, then crossing the Awatere, probably taking in the highest Kaikouras, it trends southwards. This band never crosses the Clarence River to the East, but to determine its exact boundaries would require a long period of good weather.
Both on the Awatere and in Taylor's Pass a highly ferruginous rock is found in abundance, of which specimens have been collected. It is reported that Dr. Haast found copper on Blairoch Creek at the time Dr. Hochstetter was in the country, but he lost the specimen, and wrote to Mr. McCrea, urging him to look for more, which he did, but found none, and the creek was also searched carefully by me without success.
Several reports of coal having been found at different places being given, the localities were examined, but the supposed coal always proved to be a black shale, which, when exposed to the weather, crumbles down into a substance like coal dross (serpentinous shale).
The older rock formation to the North of the Wairau Valley appears to be different altogether from that to the South, as laminated slates prevail, having fine veins of quartz ramifying through their mass.
A very puzzling formation is found between the dioritic schists and the marine tertiaries. This is a soft but tough blue marlstone, having the same strike and dip as the older rocks, and always forming a series of low rounded hills which bear a strong resemblance to the hills of the older tertiaries, intermingling so much with them that they are difficult to distinguish at a distance. In many cases also the marine tertiaries rest on these marl hills in such a way as almost to make it impossible to
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distinguish the line of junction. At many parts of the coast this soft blue marl forms reefs of a very durable nature, the action of the waves having less degrading power on them than on the harder limestone or primary rocks. 6
Along the course of the Awatere River where the marine tertiaries rest on the slates, the water from rains rushing down the steep slopes of these hard primary spurs, impinges at the line of junction on the gravels and sandstones of the softer tertiaries, producing a series of transverse troughs which are called earthquake rents. These troughs or watercourses are always shallowest on the bulge of the spur, deepening by the accumulation of water as they lengthen their course.
These so-called earthquake rents are found on other rivers than the Awatere, wherever the tertiaries rest on steep hard rocks, and though there may be on the Awatere Valley and other places true earthquake faults, as hereafter mentioned, these rents are certainly fissures produced by the action of water.
Anticlinal Coast Line of Fault.
From near Cape Campbell south to the Waiau River a great anticlinal fault can be traced, as shown on the accompanying map. Before the deposition of the brown coal and marine tertiary formations, this upheaval tilted the primary rocks to a considerable angle on both sides of the line East and West. Near Squally Point and at Amuri Bluff they have an easterly dip of 80 deg.; in other places it is westerly, the general dip of the inland ranges. On the tilted primary rocks the coal and older marine tertiaries were deposited, but before the deposition of the newer tertiary terraces another upheaval took place on the same line, producing on the former a dip from 15 deg. to 45 deg. East and West. Probably the same line takes a curve from near the Halidon hills, proceeding through Taylor's Pass, (which is an anticlinal valley,) and thence across the Wairau Valley, passing up the Tuamarina Valley, which is another line of fault, to Picton (see Section). These two valleys may, however, be distinct lines of fault from that of the coast line.
The coast and older marine tertiaries on the East Coast show the opposite dips of this anticlinal line in more places than the primary rocks. Beginning at Cape Campbell, the dip as far
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as the Ure River is 25 deg. to 30 deg. easterly; between Flag's River and Kikarangi, dip 15 deg. to 45 deg. westerly; Clarence River, dip 30 deg. to 45 deg. westerly; Amuri Bluff, dip 25 deg. easterly; mouth of the Conway River, dip 30 deg. westerly; Kaikoura Peninsula, dip 45 deg. easterly; between the Conway and Waiau rivers, dip 20 deg. westerly, and probably a reef at sea near Motunau dips westerly.
II.--BROWN COAL FORMATION.
This formation rests unconformably on the primary schists. Assuming the existence of extensive level valleys, much swampy ground, and a luxuriant vegetation during the formation, there is no reason to suppose a warmer climate than the present, as the climate of New Zealand is quite capable of producing a most luxuriant vegetation under circumstances of abundant moisture; in fact, cold is, in my opinion, more favourable to the production of coal material than heat, if the latter is excessive, as it is derived chiefly from the growth of bogs and the lower class of cryptogamic plants which thrive best with a low temperature. Nothing could be more favourable to the production of this material than the great swampy valleys which must have existed before the deposition of the marine tertiaries,--though no doubt, on the soil produced from the decayed vegetation of the lower class of plants, flowering shrubs and trees also flourished; but there is abundant evidence that the different coal seams must have been formed under a gradual sinking of the land, inter-stratifying them with clays.
The easterly coal formation of the Province of Marlborough is very small, it crops out at places along the coast with a dip to the East, but it hardly appears inland at all, except at the Amuri Bluff, where a few yards of coal may be found.
The evidence is pretty conclusive that a large coal formation exists under the sea along the coast between Cape Campbell and Bank's Peninsula, or if these brown coals are only found in small isolated basins, several may exist along this line.
Amuri Bluff is the most northerly point where the coal sandstone actually shows on land. It rises beneath the limestone with a dip of 25 deg. S.E., and for two miles South it only shows a line rising along the beach above high-water.
This sandstone is fossiliferous, containing Vermetus Dentalium, Pecten, angular jointed stalks like Encrinites, and Cidarite spines.
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Coal is said to have been found in a creek at Amuri Bluff, but it never can be of much importance, as the formation crops out within half-a-mile of the coast, or perhaps somewhat more, at a point immediately behind the Bluff. One mile South of the Bluff, the fossiliferous sandstone is tilted up sufficiently to produce a dip of 80 deg. East. It has at this place been thrust up through septaria clays, and at the line of junction the clay beds have the same dip as the sandstone, as shown in the sections of the Amuri Bluff.
If, as reported, petroleum rises to the surface at sea, one mile off Squally Point, it is probably further evidence of coal seams existing under water along the coast. The presence of submerged coal seams along the coast is a strong argument in favour of the existence of a former line of valleys to the East of the present land during the deposition of the marine tertiaries, to be afterwards noticed.
Between the Conway and the Waiau rivers, all to the East of the anticlinal fault is now under water, and the newer tertiary terraces rest on the primative rocks of the coast range. These terraces are here in some places over 100 feet high in their scarps of sand and gravel. Whether coal may be found to the West of the coast range, in the Waiau basin, will be difficult to say from the unbroken nature of the hills and the thick covering of newer tertiary gravels. Boulders of a soft sandstone are seen on the low hills between Cheviot Station and the Hurunui River, but whether these hills are themselves sandstone, cannot be seen. This sandstone may, very probably, be that above the limestone, as it did not appear to have fossils, in which case it may have no connection with the coal, as these older tertiaries often rest in this district on the primative rocks.
There is a strong probability from the swampy nature of the Waiau basin in former times, that lignite seams rest above the older tertiaries, perhaps at a considerable depth; but it is only to the South of the Hurunui River that the brown coal formation assumes any importance. At the Motunau Creek the beds extend four miles from the sea. Coal is also reported to have been found at Stonyhurst, and such may probably be the case, but the Motunau basin is entirely cut off from any that may be there by a ridge of primary hills.
On one of the branches of the Motunau Creek, close to the base of the Black Hills, an outcrop of the coal is seen in the bed of the creek (see Section); it clips S.E. 15 deg. to 20 deg.
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SECTION OF SUBMERGED FOREST NEAR CONWAY RIVER. NELSON. EAST COAST.
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On sinking a hole the seam was proved to be three feet thick; the hole was sunk one foot further into a whitish-grey clay, but imperfect tools and water prevented anything further being done. The same seam lower down the creek is a superior coal, burning with a clear bright flame, and easily ignited; it seems to be a coal well adapted for the manufacture of gas. 7
These formations occupy a large area in the surface geology of the district; they rest unconformably round the base of the mountains, in some places to a considerable altitude, and may be divided into two distinct periods--an older and newer tertiary.
The first or older tertiary period includes the great limestone and conglomerate or cemented gravels and sandstone hills. At one place a mountain (Ben More), composed of Crag Limestone, 8 attains the altitude of 4,360 feet. In many places they have suffered great denudation during the elevation of the land, and have supplied a large amount of material towards the formation of the newer tertiary terraces. These limestones appear to be non-fossiliferous, excepting in a few species of Foraminifera.
The limestone varies much in structure, it being sometimes crystalline, at other times smooth-grained, with crystalline veins traversing the mass. It is often found drab, flesh or pink colored, and also laminated in thin plates or contorted both in structure and stratification. It has now been used for building purposes for some time, and from the Amuri Bluff a large quantity is shipped for Christchurch. The stone here is free from flints, the presence of which has got it into bad repute at the Kaikoura Peninsula; no doubt there will be plenty found along the coast free from silica.
These older tertiaries are in some places much disturbed, but in general they have a strike north-east, with an easterly dip of 15 deg. to 20 deg., but sometimes as much as 45 deg.
Since their formation, owing to repeated changes in the level of the land, these older tertiaries have suffered great denudation. In some places they have been entirely removed, and the newer tertiaries rest on the primary schists.
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In many places on the ranges near the Waiau may be found patches of white limestone, the only remains of a once extensive formation. Its brittle nature has also a tendency to crumble down when scarped, which must facilitate its removal by rivers.
In some places there is evidence of a subsidence of the land, as great plains appear to have existed in valleys such as the Waiau, now filled by the newer tertiary terraces. The forests of the period still exist, showing Totara stumps erect, and the wood fresh as yesterday. Between the Conway and Waiau rivers an ancient depressed forest is now being laid bare by the action of the waves. (See Section.)
This forest is covered by a terrace of gravels and sands of at least 100 feet, underlaid by a tough blue clay embedding the stumps. The stems are prostrate above the stumps as if strong currents had passed over the plains, depositing the shingle of the terrace, and broke the trees off two or three feet above ground.
Erect stumps are also exposed inland eight miles on the banks of the Eden River, and no doubt in several other places where the rivers cut away the blue clay terraces.
It is very probable that during the last changes of the surface features of the country, some of the estuaries with narrow entrances may have had barriers strong enough to retain their waters at a higher elevation than the sea, the consequence of which would be the formation of fresh-water lakes, and it is possible that some of the fossils found on the Eden River may prove the existence of a great lake at one time between the Conway and the Hurunui rivers, including the valley of the Waiau-ua.
The massive marl blue-clay tertiary formation appears to have suffered considerable denudation before the deposition of the terraces, as isolated hills, such as Star Hill on the Awatere show this. (See Section.) It has also been much disturbed in some places. On the Awatere Valley faults are seen with a tilt of 45 deg. These faults occur sometimes at regular distances as if earthquakes had passed along the valley, producing them in an upward curve.
The fossiliferous blue clay forms a distinct tertiary formation from the limestone and conglomerate, while the marlstone along with the coal and fossiliferous sandstone is probably upper secondary. This arrangement agrees with both the succession in the Waitaki Valley, and at Wanganui in the North Island.
The idea which has been suggested, that in proceeding
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from the sea up river valleys older fossils are found, is a mistake, for wherever the blue clay occurs it contains the same fossils. Certain species are found in greater abundance in some localities than in others, as for instance, Crepidula incurva is abundant twenty miles up the Awatere River, and on the sea coast South of the Hurunui River Cucullaea singularis again is found everywhere in the blue clay, but in certain localities both on the sea coast and inland more abundant; so it is with Struthiolaria canaliculata, S. cingulata, Crassatella ampla, Dentalium Mantelli, Dosinia Greyi, Pectunculus laticostatus, and many others. It is probable that the position they occupy in the formation relatively to their abundance may distinguish a difference in age, but this comparison cannot go beyond the blue clay.
The fossils of the newer tertiaries are found in the sands sometimes stratified in thin seams. They are of the commonest and most abundant of existing species, such as Tellina, Myodora, Mytilus, Trochus, Trochita, &c.
Dr. Hochstetter's theory of the elevating power being a gradually diminishing force from the elevation of the first terrace, to the last cannot be very clearly made out. On the Eden River, where eight terraces may be seen, four of them are nearly the same thickness, and although the highest terrace is generally the thickest, it is more probable that this was caused by barrier basins lowering the waters by breaking away the barriers at intervals, than that it was an elevating power. There is nothing to prove that the whole terrace formation was not formed by this means. In the Awatere Valley none of the terraces have a fossil to prove their marine origin, the numerous fossils found there being confined to the blue clay underlying the terraces. It follows, that till these latter tertiary terraces can be proved by these fossils to have a marine origin, the theory of lake basins breaking away their barriers at intervals and lowering the waters will offer a more reasonable theory of the formation of terraces than elevating throes of the earth.
In connection with this it may be mentioned, that marine fossils are found in the sands of terraces on the sea coast, but generally in such cases there is only one deep terrace, anything like a series being absent; but it is in accordance with existing appearances that a series of Estuary basins, formed by a barrier of land now under water, once existed more to the East than the Lacustrine basins of terraces now mentioned, which would explain the presence of marine fossils.
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NOTES ON THE COAST AND HARBOURS FROM MILFORD SOUND TO HOKITIKA.
Milford Sound 9 is about eight miles in length, with an average width of one mile. The greater part of the Sound is completely land locked; but owing to the great depth of water and the precipitous character of the shores, there are only two places where anchorage ground can be obtained--Anita Bay, under the south headland, and exposed to the north-west, and Fresh-water Basin, a small but safe cove, with 3 1/2 fathoms at the upper end of the Sound. There is about 1000 acres of available land at the head of the Sound, formed by the Cleddau and Arthur Rivers, and there is also room for a few houses and cultivations at Anita Bay.
The position of this Sound, the facility with which it may be entered with the prevailing winds, and the complete shelter it affords in the heaviest weather, would make it a valuable harbour of refuge.
For this purpose a small settlement might be encouraged, and moorings provided by ring-bolts secured to the precipitous cliffs, as in the Norwegian Fijords.
There is no access to any part of the shore of the Sound by land; but by mooring hulks alongside the rocks, if it were desirable, goods could be transferred from vessels of the largest size to small craft able to enter the bar rivers to the northward.
In Milford Sound, building stone of the most durable and handsome kind, can be obtained with great facility, comprising granites, gneiss, and other crystalline rocks. There are, also, good indications of the existence of a fine quality of white marble, and also mineral lodes, which have not yet been sufficiently investigated.
Coast to north of Milford Sound.--The lofty mountains, which southward form the coast line, trend inland to the north of Milford Bay, and being some distance from the coast, leave a belt of land more or less available for settlement, varying from five to twelve miles in width.
From the Sound to Jackson's Bay (a distance of 60 miles) the country, as seen from the sea, consists of rounded hills, wooded to their summits, being composed partly of clay slate and mica schist; but also of sandstones, shales, limestones, and brecciated rocks, belonging to the coal formation, and tertiary rocks which overlie it.
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Cascade Point.--For seven miles inland from Cascade Point there appears to be a level plateau rising from 300 to 700 feet altitude above the sea, formed of the last-mentioned rocks, and under which it is possible the coal-seams might be discovered.
Notwithstanding the broken appearance of the above district from the seaward, it is intersected in every direction by valleys that afford a good extent of available land, and between which there is easy communication by low saddles. Lakes frequently occupy portions of those valleys; and the river, having only a small fall, there is easy water communication by boat or canoe for long distances.
The coast from Milford Sound to Martin's Bay is rocky; but there is a Maori track along the beach to the Bay south of Yates' Point. The Natives have occasionally landed at Kaipo Bay with their sealing boats, but there is only a slight shelter in this Bay from the south-west.
Martin's Bay is three miles wide and one mile long from a line between the north and south headlands. It has a small sandy beach at the back of which is the Kaduka River, and a line of swampy lagoons navigable for boats. There is a landing place for boats under the shelter of the south heads.
The Kaduka River enters Martin's Bay close under the north head, the entrance being well sheltered from the N.W., but quite exposed to the southerly swell and winds.
The channel when examined in 1863, carried from 8 to 10 feet on the bar at low water. Its width was 120 feet, but as it curves to the south behind the sandspit and has a broken rocky beach on the north side, it appears more formidable from the seaward than it really is. There are however several rocks well out in the channel which makes it necessary to keep close to the point of the spit, along which within the bar, there used to be 18 feet of water.
The Kaduka River leads up to the McKerrow Kakapo Lake, a distance of 4 miles carrying 12 feet of water, except at one point where there is a snag fall at low water which has caused the formation of a gravel bank with only 6 feet on it at high water.
The tide ebbs and flows to the lake but excepting close to the outlet its waters are fresh. The lower end of the lake, which is 12 miles in length, is shallow with a winding channel, the shore being formed by terraces from 10 to 60 feet above the sea level of gravel and sand resting on strata containing recent marine shells.
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These terraces should be examined for beach gold, as they are similar in character to the auriferous terraces further up the coast.
The upper part of the Kakapo Lake has a depth of 75 fathoms and the shores are nearly as precipitous as those of Milford Sound.
The river, which enters the head of the lake, has two principal branches, the south branch leading by the Greenstone Pass to the Wakatipu Lake, while the north rises close to the sea in Big Bay and flows between the ranges north of the Kakapo Lake expanding in its course into several lakes of considerable size.
Big Bay is immediately north of Martin's Bay, the headland between them (Cape Brown) being a sharp promontory terminating in a reef of rocks. This Bay is four miles across from Cape Brown to Awarua Point, and has about the same depth. It is open to the W.N.W. but owing to its square shape, it affords excellent shelter from all weathers south of west, the anchorage being within a rocky point close to the S.E. corner of the Bay in five fathoms of water and sandy bottom. There is however a good boat landing in southerly weather, one mile within the headland. In the N.E. corner there is moderately good shelter from the N.W. with 5 fathoms soundings and a boat landing place in fine weather. The beach at the head of the Bay is coarse shingle--unlike that of Martin's Bay which is a fine yellow sand; black sand also occurs in Martin's Bay, but is local and only in small quantities.
There is easy communication between the Kaduka River either round the coast or over a low saddle from the head of the Bay to the Okuri River that enters the Kakapo Lake. A direct road might also be carried from this Bay to the Greenstone Pass, avoiding the Kakapo Lake altogether.
There is, also, a moderately easy saddle to the N.E., leading either to the Arawata River, or to rivers entering the sea south of Cascade Point. A little gold has been got in some of the valleys, and gold obtained under large boulders on the beach in Big Bay is represented to be in very rough particles. The oldest rock in this district--with the exception of the crystalline rocks, which have been already mentioned as forming the back ranges--is a blue clay schist much intersected by quartz veins. This rock is broken by dykes of diorite, aphanite, hornblende, and other basic igneous rocks. With this association of rocks, in the northern ports of the Island, there are generally local patches of coarse alluvial gold; but in Otago the same formation, though
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extensively developed and well tested, has not yet proved to be auriferous.
From Big Bay to Barn Bay the coast is again very rocky but still passable, there being an old Maori track over the worst points, and in other places the line cut by Mr. Bain and his survey party in 1863.
The range of hills along the coast is cut by Gorge River a few miles south of Barn Bay, which has a narrow but deep entrance sheltered by extensive reefs from the S.W. This river is represented to be navigable by boats for several miles to a lagoon or lake, and then it opens up a large extent of country.
Barn Bay does not appear to afford any shelter, but at this point the hills recede from the coast in a line straight for Jackson's Bay, leaving a triangular area of land occupied by terrace plateaus and wide valleys, a large proportion of the surface being either open land or covered only by low scrub. South of Cascade Point is a large sized river opening to the S.W., and apparently having a very good width and depth on the bar at low water as far as could be judged from the seaward.
The valley of this river is very extensive, and is reported to contain several lakes and open plains (Pakahis), and, is probably, the country to which Barrington and his party reached from the head of Wakatipu Lake in 1864.
Between Cascade Point and Jackson's Bay the cliffs rise almost perpendicularly from the sea, the track being over the plateau. A landing might be effected in fine weather at the Stafford River or in a little bay immediately south of the headland. Stafford River is reported to have been prospected for gold with but slight success.
Jackson's Bay is an excellent anchorage in 3 to 5 fathoms, well sheltered from all westerly winds but exposed to the N.E. The promontory is composed of carbonaceous sandstone, and is separated from the clay and mica schist rocks by a low neck of land. The beach, from the anchorage to the flat land, which commences at the Arawata, is rocky, and though passable at low water, a road will be required if the Bay is ever used as a shipping place, as there is no room for settlement in the immediate neighbourhood.
The Arawata or Jackson River is a wide shingle river with a double bar marking the size of the river when low and when flooded. When the river is low the outer bar and spits form a bay with two fathoms of water, and temporary shelter may be obtained
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in a lagoon under the south spit. The inner bar has only 6 feet upon it, and that depth is carried up the river for three quarters of a mile, but without any anchorage that would be secure during freshets accompanying heavy weather outside.
This river takes its rise from the glaciers of Mount Aspiring and Mount Ernslaw at the head of the Wakatipu Lake; it has a wide shingle bed and can be easily ascended when low, for 20 to 30 miles.
From the Haast Glacier at the head of the left hand branch the source of the Matakitaki, a tributary to Lake Wanaka, can be reached by crossing over an Alpine col at an elevation of 6,000 feet.
From Jackson's Bay to Arnott Point, a distance of 30 miles, there are no secondary ranges of hills, the mountains rising abruptly from a level plain about 5 miles in width, composed of the alluvial gravels and silts brought down by the rivers Waita, Haast, Okari, Waiatoto, Arawhata. The lower ranges are only represented by several isolated wooded cones such as Mosquito Hill north of the Haast, and Mount Bayer north of Arawata.
The shingle in all these rivers is almost wholly of clay or mica schist, with quartz derived from the veins which intersect these rocks. The isolated hills are, however, composed of granite according to Dr. Haast, who explored the district in 1863.
A great deal of the land in this flat country is very swampy in its present state, but there is a good proportion of the land which is available, being above the level of the highest floods. It grows excellent timber such as Rimu (Dacrydium cupressinum), Yellow Pine (var. of same sp.), White Pine (P. Dacrydioides ap.), Rata, (Metrosideros), and Birch (Fagus), and the undergrowth is light and very easily cleared. The soil is light loam 2 to 6 feet deep, resting on shingle, and is not so ferruginous as the soil further south, nor so tenacious as the subsoil in the neighbourhood of Hokitika. The total area of the above flat country may be estimated at 100,000 acres, of which one half may be considered available.
Gold is got along the beach in greater or less quantity right from Jackson's Bay, northward, to the Waita River to the north of Haast River, being associated with grey quartz sand; but to the south with black iron sand. From the sea the outline of high terraces can be discerned along the spurs of the back ranges, especially at the northern extremity of the flat where the coast ranges again commence, so that it is possible that heavier gold
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may yet be found in this district, that which has as yet been obtained being of the finest grain.
The Waitoto was described by some diggers to be much superior to as a port to the Arawata, both as regards the entrance and the shelter afforded within the river, but it was not examined.
The Okura River has 9 feet at low water on the bar, and is the best bar river examined, its entrance being sheltered by the Open Bay Islands; its only drawback arises from its being rather narrow and having a very sudden turn on entering the lagoon. The lagoon is very extensive and receives three rivers of which the northmost is of largest size being navigable for a few miles at high water.
Haast River is the next in size to the Arawata on this part of the coast; but being like it also--a shingle bed right to the sea--it is inferior as a safe and permanent anchorage. The entrance is good, with seven feet on the bar, where there is one channel; but where there are two channels the depth is, of course, diminished. There is very good temporary anchorage three-quarters of a mile from the mouth, sheltered by an inner bank from the sea, but exposed to freshets. To the head of the south branch of the river, an excellent pass was discovered by Dr. Haast, in 1863, from the Wanaka Lake; and this pass has been recently examined and found to be available for driving stock across from the east to the west side of the mountains.
From Arnott Point to Bruce Bay the coast is bold, with a few sandy bays; the country being similar to that between Milford Sound and Jackson's Bay.
The Paringa River is the only place where a landing can be effected; it enters a bay which is well sheltered from the S.W. The entrance is rocky on the south side, and the bar has three feet at low water. Several coasters have gone into this river, which opens up a good extent of valley land. Gold has been found in this district, but not in remunerative quantity.
In sailing along the coast, a terrace, having an altitude of from 150 to 200 feet, is distinctly visible on the spurs descending from the hills. It is broken through by the river valleys, showing that it must be of earlier date; and, in several respects, resembles the auriferious terraces found along the West Coast of Nelson, north of the Grey River. Natural sections of the terrace occur a few miles south of Bruce Bay, which show that it is composed of 50 feet or more of wash gravel.
Barn Bay is formed by a point running out at right angles to
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the coast. It affords shelter from the S.W.; the anchorage being in three fathoms. There is no good landing place if the sea is at all rough. North of Bruce Bay, the country along the coast assumes quite a different character from any previously described, which it maintains as far south as Abut Head.
The outline presents a series of ridges and hummocks, with deep irregular-shaped valleys between them, and cut by wide shingle-bedded rivers that descend in straight lines from the lofty mountains that cluster round Mount Cook.
The hummocks are moraine accumulations, the sections of them where they form bluffs cut by the sea, showing nothing but huge sub-angular boulders mixed irregularly with sand and clay. Between these moraine bluffs are long sandy beaches, nearly every one of which has yielded gold sometimes in very large quantities. The gold is all fine and intermixed with black sand. It is not improbable that it is from these moraines--the material comprising which is derived by pure mechanical attrition of the auriferous and other rocks--that the sea has re-washed most of the fine gold now scattered along the coast. Their rounded form would suggest that they have been submerged since their formation, in which case the marine abrasion and re-assortment would have been much more extensive than now.
The next navigable river to be mentioned is the Okarita, which has a deep though narrow entrance, with rather a sharp turn and rapid current. It is well sheltered from the S.S.W., so that the bar is generally smooth. The most extensive lagoons on the coast are at this place, in consequence of which the flood tide runs almost as strong as the ebb. There is some fine land in the neighbourhood of easy boat communication, and the picturesque beauty of the scenery in the vicinity of Okarita is not equalled by any place on the coast.
Coarse gold has been obtained at several places in the interior but not in large quantity, its occurrence has, however, a very peculiar interest, as it probably indicates the existence of portions of the Pliocene terrace gravels that have escaped destruction at the time of the formation of the moraine drifts.