GEOLOGICAL REPORTS By the Hon. J. C. CRAWFORD.

Wanganui Chronicle, Volume 7, Issue 335, 19 March 1863, Page 3

GEOLOGICAL REPORTS By the Hon. J. C. CRAWFORD.

Mr. Crawford, as Government Geologis t Jias this summer continued the geological excursions, which he began last year as an amateur. In the Provincial Government Gazette of 2nd March are published a narrative by Mr. Crawford of a journey in the Wamirapa and the East Coast in January and February last, a report by Mr. B. Smith of Melbourne on some specimens of the rocks of the Province sent to him foi examination, and Mr. Crawford’s notes on Mr. Smith's report. From the first and last of these we give the following exrtacts, as couveying the most important infomation these papers contain

In this ecxu.sion coal i. the only mineral .Ar. Crawford seems to have found traces of. l.e says:—“ln these sandstones and mudstones ” (ebtween the mouth of the Wliakatane and Castlepoint), 1 found small seams of coal and numerous impressions of vegetation, but none clear enough to be en (bled to judge of their age, but as the coal-sea ms appear to be lignite, or brown coal, I have little doubt that we may put them down as of tertiary age. In fact, I beleive them to be of the same age and character, as the eoal shales of the Whanganui River, mentioned in my letter of February 17th 18C2 1 proceeded up the bed of the stream behind Castle Point in the hopes

of falling-in with some seams of coal. I went on as far as I could penetrate, perhaps three miles,. finding plenty of plant iuqrressions, but no actual coal seams. Mr. Guthrie informs me that some years ago one of his shepherds, who has since gone to Australia, brought in a handkerchief full of coal, (stating that there was i plenty more where he found it) which, burnt well and seemed of good quality, and which must have been found within three miles of the Castle ; but unfortunately he had neglected to ask him vhei-e he got it. _ The coal question in the East Coast District may be put as follows. My impression is that the mudstones and sandstones of the coast are of tertiary age and therefore if any workable coal seams are found in them, that the mineral will be of inferior quality,, but there aie the little known calcareous rocks that are to be considered Although I have seen no indication of coal among the calcareous rooks of the East Coast, except perhaps at Teawaite, I think we have at all events some reason to expect the possibility of its being found ; and as from the broken nature of the country it might take some years for one individual to explore it thoroughly, I would suggest that a reward for the discovery of the outcrop of workable seams of coal might stimulate the perceptive faculties of shepherds and others, whose dailv avocations lead them through the defiles of these regions You will perceive that we have now established three nearly parallel lines of plutonic or volcanic action in this Province. In the centre, the ancient rocks of the Rimutafca, Tararua, and Ruahine, with tlieii spurs folded and pressed together, and having a general direction of N. N. E. true.. In the East, the calcareous and tertiaty rocks, tilted on a line of about N. N. E. (magnetic) from the ancient rocks of Cape Palliser towards the Province of Hawke’s Bay. In the West r we have part of the volcanic chain of Ruapehu and Tongariro, ending abruptly, however, at the s outhern slope of Ruapehu, and perhaps I might include a fourth line in that neighbourhood, in the Kaimanawa range, but it is hardly in the Province. -From the central chain on both sides tertiary rocks extend East and West I have therefore narrowed the area in which metallic ores may be sought to the main central range above described, the Kaimanawa range in the Taupo country and the Aorangi range at Cape Palliser, save and except the chances of finding gold below, or in, the drift of the Wairarapa and the-West Coast.” In the Notes made by Mr. Crawford on Mr. Smith’s Report he mentions that that the excursions die had made had ■ given him a sufficient knowledge of the leading geological features of the Province, to enable him to limit the search for min- ' erals, with the sole exception of coals, to the main ranges of Rimutaka, Tararua, and Ruahine with their spin's ; the Aorangi I'ange at Cape Palliser, and the Kai Manavra range in the Taupo country. He then goes on as'follows The theoretical proof which I gave in my letter of December 18th, 1861, of the existence of the “ gold constants ” in these ranges is now confirmed by the discovery of granite, combined with the evidence of the ancient character of the bulk of the stratified rocks.

The granite is found in the ridge behind Mr. J. Brown’s, in the Upper Hutt, which bounds oil that side the Mungaroa swamp ; and I have also found it on the Mungaroa hill. It is very fine grained, and may easily be mistaken for a sandstone. It will doubtless be found nearer Wellington, and may come into use as a building stone. Near it is sandstone with- quartz veins, ami mudstones of two kinds, but I cannot yet say in wlnit sequence. -x- * X Quartz lodes and other mineral veins seem principally exjxxsed in the fractures of the anticlinal axes, which bears out my original impression that minerals will be found to lie deep, and this view will also affect the argument as to the locality of alluvial gold diggings*. If gold lies deep in the rocks while “ in situ” the wearing away of these rocks (particularly as here in deep and st.'ep valleys) will deposit it in the lower valleys only, and it may be plentiful there, while entirely absent from the higher ground.

Mr. Brough Smith’s remarks with regard to gold seeking show a masterly grasp of the subject. A reference to my letter to you of October 21st, 1862, will show that I have most faith in gold being found, in the North Island, in the continuation of a line from the Middle Island Gold Fields to Coromandel, and that the present evidence is in favor of mieacious and talcose schists as the best gold bearing rocks of New Zealand ; but I have also strong reasons to show why the search for drift gold in this Province should not be hastily abandoned. I will first of all dispose of Barraud’s well. This well is sunk for a few feet only through a sandstone aud a felspatho -siliceous rock. These rocks were said to he intersected by a vein stone, which was covered with rubbish when I visited the well, and unfortunately on the following clay it was bricked up. There is neither drift nor alluvium above the rock, and only an inch or two of soil.

I must now make some small corrections as to Mr. Brough Smyth’s idea of our mountain chains. His view is, naturally enough, that our main ranges throw off spurs east and west, spreading across the country, whereas the remarkable feature is 'this, that the mountain ranges of the liimutaka, Taraiua, and Ruahine, including all the mountainous country in this neighbourhood, pass like a wall to the the spurs keeping on the

whole the same direction as the main ranges. Of course one does hot speak of a wall as built by a stonemason, a rigid line, nor do all the spurs and ridges adhere to a strictly N.N.E. course, but subh is the main direction. The main |trike of the rocks. being, I should say, about North (magnetic), with however mUny exceptions. Most of the maps give an erroneous impression, by marking a range, curving from theßualiine N.N.W. towards Taupo, winch range does not exist, although the broken tertiary plateau may tliere reach an elevation of 2000 feet.

In its broadest part, from the coast opposite Man a to the Whirarapa, the main range does not appear to exceed twenty-three miles wide. At the gorge of the Manawatu the breadth, following the curves of the river, is only about seven lifiHes. These mountains have assumed their form less from upheaval than from lateral pressure. The strata are accordingly bent and folded upon each other, and the ranges are separated into a succession of sharp and nearly parallel ridges, culminating in height towards one or more central axes , but. high and abrupt also at both sides, where the sea or the tertiary rocks meet them in a horizontal, or nearly horizontal line.

One consequence of this conformation is that the rivers, while within the ranges, run in ravines, l’arely, as in the instance qf the Hutt, expanding into valleys.

The only rock which I can venture to call lava in this main range, is the red rock of the Bimutaka (on the authority of the Bev, W. B. Clarke), but where it is found, and elsewhere in these ranges, there are no signs of volcanic vents. The stratified rocks, sandstones, mudstones, slates, &c., seem to, and I think will' be found to continue to, occupy the main part of the ranges. The accumulations of drift on the eastern side of the ranges are fully equal to those on the west, and the tertiary rocks may be said, witb some exceptions, to be of the same character and thickness on both sides of the main range. Mr. Brough Smyth suggests, as particularly worthy, of immediate attention, the basins of the Hutt, the Waikanae, the Otaki, the Manawatu, the Eangitikei, and the Whanganui, I would omit the word immediate in reference to. the three last named of these rivers, and substitute for their names those of. the Buamahunga, and its tributaries on the right bank, the Waipoa, the Wai Ngawa, the Waioliine, and the Tauliere Nikau (perhaps this last cannot be called a tributary). Although I should like to see the head waters of the Wanganui prospected, yet, even supposing the natives would consent, the expence of a party would be enormous In proportion to the work done. I only found about tivo yards of the ancient-rocks during a journey of some hundreds of miles in that direction, and then in the bed of the Waipare, a tributary of the Wanganui, with the hills, formed I believe of tertiary rocks, rising at an angle of 4 5° or thereabouts, on both sides, to a height of say 700 feet above the bed of the stream. I consider that Upper Wanganui must wait the progress of development of the gold fields from Coromandel through the Waikato country, which may throw sufficient light upon the subject. The same remarks will apply to the Bangitikei river, and those rivers lying between it and the Wanganui. The heads of these rivers would answer Mr. Brough Smyth’s idea of searching towards the sources of the streams, but a prospecting party to explore them must be fitted out and kept supplied at great expense and must be prepared for very deep sinking, and as yet there is no road. With regard to the Manawatu, although old drifts may. He beneath the tertiaries on its banks, and may eventually be worth sinking, for, if we had any reasons to warrant the outlay the river itself is most. Unlikely for gold. It presents the curious feature of rising in the tertiaries of the East Coast, bursting through the main range, and thence again passing through tei’tiaries to the sea. The whole course of the river through the ancient rocks does not exceed seven miles, and its stream there occupies the whole breadth of the channel.

Immediate explorations of tlie Hutt, the Waikanae, and the Otaki, with the Eastern rivers previously named, I particularly concur, in, for reasons which I shall presently show. This brings me to the main point of jny argument, which is, —if gold exists, where is it to be found as drift and alluvial gold 1 I have endeavoured to show the character of the mountain range, and from this it will be seen that in general the rivers, while confined to the range, run in very narrow and perpendicular channels.

If we then consider the great denudation which lias removed the rock from these valleys, say in the glacial epoch, we may ask where has the material gone to 1 The answer is obvious. It does not lie, or only to a small extent, within the hills, but has been swept ip to. jbhe Wairarapa country on the east, into the basin between Kapiti and the main range on the west, and into the Hutt valley on the sou th-south-west.

If these rocks contained gold, most, if potj all of it, would follow the same route. I therefore would suggest that, in a search for drift gold, attention should be first directed to a careful examination of the Valley of the Hutt; and also, what I have already hinted fit, that the question of grappling with deep sinking in the Wairarapa, and perhaps also on the West coast, should be considered, cpmbined with an investigation of the river beds previously mentioned a,s far as practicable.

As Mr. Brough Smyth also suggests that gold may be looked for in unexpected formations, I would not omit the blue clay. Although it is a fqssiliferous rock it has a great appearanco of being a drift formation, and I submit the following theory of its deposit, say to the eastward of the Bimutaka and Tararua.

The gold question will not be set at rest until the Wairarapa and the West coast plains are bottomed at several points. Now that I have acquired a general knowledge of the rocks of the province, I quite agree with Mr. Brough Smyth, that my attention should be directed to a minute investigation of some limited district. What I should now propose, with regard to the Geological Survey and apart from a search for gold, would be to make a detailed survey of the rocks of this range from east to west, mapping them and collecting specimens of every stratum, taking for the purpose the only lines on which anything like a complete detailed survey can be made, namely, the scarped ends of the ranges from Terawiti to the Wairarapa and the next section further north, from the sea beyond Porirua up the line of road to this harbour, and thence over the Bimutaka to. Pea-. therston.

These traverses are absolutely necessary tq shqw the sequence of the rocks and form a basis tor further explorations, and as I find fresh mineral veins every time I cross the Bimutaka, we might expect to make some valuable discoveries. But I should like first to know the views of the Government as to the duty of the Government Geologist in a search for gold.

The ti’averse and survey of the rocks which I propose to make from the West coast to the Wairarapa, by the line of l’oad, would be a necessary preliminary to the search for coal. I have discovered a black mineral at various points on the Bimutaka hill, but its character is not yet determined.

I have proved the “ gold constants,” and I have obtained strong evidence in favour of the probability of finding gold. But should the “ gold constants ” prove inconstant, and the precious metal elude our search, there is no reason to despair of making discoveries of other valuable metals. I liave every reason to think that these ranges-are full of mineral veins, and at the present moment I await reports on the character of those already found ; but at the same time I suspect that our mineral wealth lies deep, and will require an expenditui’e of skill, capital, and patience for its development. I have the honour to be, sir, Your most obedient servant, James Crawford, Government Geologist.