THE GEOLOGY OF SOUTHLAND.

Southland Times, Issue 1540, 20 February 1872, Page 3

THE GEOLOGY OF SOUTHLAND.

Captain Hutton's lecture on the abovenamed subject enables us to supplement our report on the coal deposits of Southland. The lecture was delivered on the evening of Friday, 16th inst. , in aid of the funds of the Athenaeum. The attendance was not so large as might have been expected. The observations of the lecturer were listened to with marked attention, and without advancing extraordinary claims to be regarded as a public lecturer, Captain Hutton succeeded, in endowing the subject with quite a new interest. The number of references that were made to geological charts and tracings, together with the diagram sketches adduced in support of the premises, renders it impossible to give an intelligible report of the lecture as delivered. We have therefore fallen back upon the account of the expedition conducted by Captain Hutton, bringing the information contained in the lecture to bear upon the narrative of his researches. THK FORMATION Or THE DISTEICT. In treating upon the general result of his observations, the lecturer described the geological formation of Southland as a trough, in which the secondary and tertiary formations were deposited. The edge of the trough or basin, as indicated by the primary formation, cropped up at the Bluff Harbor Point, Steep Head, New Biver, from thence across the roadstead to Howeli's Point, following the direction of the Longwood range to within a very few miles of Scott's Gap. At this point, an interruption took place, and the primary rock was lost until the west side of the Waiau was reached, from whence it recrossed the river in the vicinity of Blackmount, following the range ot the Takitimo and Eyre Mountains. At Lowther, it follows a circuit across the country, coming down close by the east bank of the Mataura, and running out towards the coast line in the neighborhood of Fortification. The coal deposit is of the true brownformation, commencing at Taylor's Creek on the west side of the Takitimos, and terminating at Mount Nightcap, so far as traced. From Mount Nightcap and extending eastward, taking in the base of the elevated lands lying ' in that direction, including those of the Hokanui mountains, terminating at the Mataura, it is of the true • •econdary formation ; the remainder '

of the district is of alluvial formation, which extends down through the valleys of the Aparima, Oreti, and Mataura, in narrow belts, until reaching the neighborhood of Forest Hill and the Oreti Hundreds, when it opens out into the entire breadth of the country, from the confines of Jacob's "Riveron the one side to the east bank of the Mataura on the other. Although the subject was carefully eschewed by the lecturer, no one at all acquainted with the theory of deepsinking, could have listened to his remarks without being impressed upon the point. The primary formation, or, as it is denominated in digging parlance, the bed-rock, must at one period have been the by-wash of the surrounding district, a district which has already proved itself to be richly auriferous in , the alluvium. No theory in the recurrence of gold is better understood than that the metal finds its specific gravity, so that in the sedimentary formation of the country, heavier deposits would of necessity sink down to the primary or bed-rock. Reflections of this kind open up a very wide field for speculation— speculation that is well calculated to stimulate the exertions that have from time to time been made to apply a practical test to the deep-lead theory of Southland. Before dismissing this view of the ques tion, it is right to observe that Captain Hutton's remarks on the geological formation harmonise with the opinion so long entertained that Southland was the original outlet for the Wakatip, and;in all probability the Wanaka, Hawea, and I certainly the Shotover. The channel through which this drainage passed, now loßt to sight, must of necessity form a gigantic gutter, and the strong probabilities are, nay more, the certain conclusion is, that it must be rich in auriferous wealth. THE EAST BATTK OF THE MATAFRA. As stated in a previous report, the enst bank of the Mataura was the first district visited by Captain Hutton in prosecuting his search for coal. The party proceeded to Mr Bruoton's ho me- station, and examined a seam which has been wrought for station use for some time past. The outcrop was found in the face of a hill, near to its base. The seam, which measures 2 feet 6 inches in thickness, is a bituminous coal, mixed with shale bands. The percentage of shale is large, consequently the commercial value of the article is greatly impaired. In burning, it leaves a heavy slug, and bears other traces of impurity in the vegetable deposit of which it is composed. The scientific explanation of this defect is that the grit initseomponentpartswas much too coarse, so that the vegetable substances were cut up into such fine particles as to cause them to mix freely with the clay sediment. The seam, which is supposed to run right through the centre of the hill, has been opened up by two drives, the one twenty and the other thirty yards in. "With the view of striking the seam at a 'lower level, a shaft was put down at the mouth of one of the drives. After sinking through 90 feet of sandstone, the shaft has been abandoned, without any trace of coal having been found. Both drives are supposed to have struck the one seam. Q-enerally speaking, the prospects were not encouraging ; and from Mr Brunton's run the party proceeded up the banks of the Mataura, and examined outcrops at the Falls, ECuapdale, and Waimea plains, each of which was pronounced to be pure lignite, although of superior quality. MOUNT HAMILTON. The Mount Hamilton coal, about which some excitement was created a few months ago, was rather humorously disposed of by the lecturer. The outcrop was examined at an elevation of 2,500 feet above the level of the adjoining plain, and some 3,500 feet above the sea. The whole extent does not exceed more than 10 or at most 15 acres. There were, the lecturer said, two or three seams of it, the largest not exceeding ten inches in thickness. If the whole lot of the Mount Hamilton coal could have been got out free of cost, it would not nearly pay the expense of constructing a tramway. There was not the slightest chance of this place being profitably worked. It might be that other little patches would be found lying about the flanks of the mountains, but nothing that would ever warrant an expensive undertaking. Indeed the Mount Hamilton coal would afford specimens long after many other seams had been wrought out (laughter.) The formation is different from that of the coal found at Brunton's or the Hokanuis. What little existed was found to correspond in age with that of the Greymouth coal, but not the slightest inducement existed to warrant the opinion that it would ever be worked advantageously. THE BEOWN COAL was designated by Capt. Hutton as the most important discovery he had made in this part of the island. The first outcrop examined was situated in a place known a 8 Taylor's. Creek, at the base of the Takitimos. The seam was six feet thick. The same formation was traced round the base of the Takitimos to a point named Linton Creek, where two outcrops were found. Following the valley round towards Mount Beaumont, no fewer than seven outcrops were met in with, eight feet and upwards in thickness. From Morley Creek, a part of Mount Beaumont, the party proceeded on to the Nightcap mountains, where an outcrop was also found. This being the nearest and most accessible to the Wintou terminus of the railway, very naturally became the chief point of attraction. At a rough estimate, the entire extent of coal-bearing country indicated above, is not less than 26 miles ! in extent, and when we remember that the exploration was only casual, and therefore imperfect, it is not by any means certain that that is the limit of the discovery. The outcrop is situated on the western side of the spur, so that the first question that suggests itself as,

regards the working of the seam is the probability of its being- traced through the bill to the eastern side. The average dip of the rocks in the vicinity is from three to five degrees, a fact which encourages the belief that the seam would be got on the eastern side at no great distance from the surface. On this (the eastern side) the ranges fall down into the valley of Jacob's River, which attains a level eonsiderablv lower than that of the situation in which the outcrop is found on the opposite side of the hill. These facts favor the opinion that the seam could be opened up without much trouble at the point of the range most accessible to the railway line at the Winton terminus, j The practical opinions we have brought to bear upon the subject agree in stating that the most advisable course would in , the first instance be to get trenches cut ] at right angles at the outcrop of coal to i ascertain the dips, afterwards to follow I them to the east side, and then to put a shaft or bores down for working at the lowest level. This could be done at very little expense. Iv the event of the seam not being found, the configuration of the country is such that no great obstacle presents itself to the coal being wrought from the western side. Mount Nightcap, at the place indicated, is a terminating spur, and a tramway formed round its base from the eastern side of the valley to the ascertained position of the outcrop on the western side would not exceed more than two or three miles. The entire distance from thence to Winton is about 15 miles. The heaviest part of the work would be the bridging of Jacob's River and the New River, neither of which presents very serious obstacles. On the other hand Heddon Bush is so situated that a supply 'of timber at a convenient distance is ensured. Besides working the coal, the tramway would penetrate an extensive tract of country suited for agricultural pursuits, and also communicate with still more extensive tracts on the western side of the range, the whole being estimated at an area of 40 miles in length by an average of 20 miles broad. With the exception of a few patches sold to the runholders, the country remains unalienated from the Crown. From the port of Riverton, the outcrop is distant about 40 miles. Commenting upon the quality of the coal, Captain Hutton remarked that he had no hesitation in saying that it was quite sufficient for all practical purposes. For ocean-going steamers it was rather too bulky. It burned away too rapidly. But for coasting steamers, steam engines, locomotives, &c, it was perfectly suitable. It produced an intense red beat, quite sufficient for sharpening tools, although not perhaps strong enough for welding purposes. For household purposes, however, as also the general purposes of colonial consutnpt, it would be found admirably suited. It was much superior to the coal found in and about Dunedin, where it would be sure to find a ready market. It ia also to be noted that ironstone and pottery clay have been obtained in the vicinity of Mount Nightcap. The latter has been experimented upon for the making of pipes, with results that are reported to bs highly encouraging. We may add that the existence of brown coal at this place has been known for many years past. In a report by Dr Hector to the Provincial Government of [ Otaso, dated October, 1863, after desj cribing the strata, he goes on to ! say—" I am informed that brown coal has been discovered among the ranges, so that it is very probable that we have here the same succession of formation as occurs from the Kakanui mountains N.W. towards the coast of Moeraki." At a still later date, a quantity of this coal was brought into Invercargil], and tested in firing the locomotives on the Bluff line. The construction of the fire-boxes prevented the test from being fairly applied, some trifling alteration in the bars being necessary to prevent the fire escaping. The coal, however, proved itself a powerful combustible, and with the alterations referred to above, it would have been quite sufficient for the purposes of the line. OREPTTKI. The geological formation of this place is singular. It is of the secondary class, forming an isolated bight in the base of the Longwood range, which, as stated above, forms the edge of the trough on the western side. The occurrence of gold ia equally singular with that of the formation. Close to the base of the hill, a heavy sample of coarse nugjgetty gold is I obtained. Towards the coast-line, the gold becomes finer. That found on the beach is finer still. In fact, it becomes what is generally known aa gold dust. Tewaiwai Bay, on the edge of which Orepuki is situated, is known to be subject to constant landslips. The sea is observed to be making continual inroads upon its banks, hence, the probability is, that while the heavier gold is washed down from the range, the fine particles deposited on the beach are washed in by the action of the waves out of the debris carried away by the landslips. The coal deposits are of the true brown character, differing from that of the Takitimos only in a higher rate of the sulphuric acid. No real out-crop was found. What was examined by Captain Hutton was got exposed at the bottom of the diggers' races. The dislocated nature of the country prevented any effort being made to trace its dip. The opinion formed was, that it was of no commercial value, i and so firmly was that opinion enter- | tamed, that the lecturer did not hold out any encouragement whatever to go to the trouble and expense of prospecting for it. OTAPEEI OBEEK. At Otaperi Creek, in the Hokanuis, a good bituminous black coal was found, quite capable of competing for the trade of the ocean-going steamers with any English coal in the market. Three out- \ crops were examined at the base of the ' Hokanuis, the thickest and purest being situated on the south-east slopes, about 12 I

miles from the township of Winton. The extent of coal-bearing formation, of which these out-cropa form a part, is estimated at 14 miles. In treating upon this point of the subject, Captain Hutton strongly recommended that the district should be prospected. By prospecting, he explained that he meant surface search. Boring, on the other hand, as a preliminary part of the inquiry, was wholly condemned.