The Pamphlet Collection of Sir Robert Stout: Volume 68
"Ancient Glacier Deposits
"Ancient Glacier Deposits.
* "Transactions New Zealand Institute," v. p. 384.
"Seated on the top of the saddle that divides Monro's from Gabriel's Gully is a deep, cup-shaped hollow in the schist rocks, which has been filled up, much higher than the present lips of the cup, by gravels cemented into a hard blue conglomerate. This is the Blue Spur, famous for the immense quantities of gold that have been derived from it. On close inspection, this hollow is seen to have been an old mountain tarn with smooth polished sides, which have, however, now decomposed into blue clay to a variable depth of from two to six inches Although I could detect no striae on the sides of the hollow, I have no doubt but that it was excavated by a glacier. This old rock basin is filled up with beds of conglomerate that dip to the east, and, as a rulepage 15 the stones in the conglomerates get smaller towards the east, which, together with the direction of the dip, prove that the old tarn was filled up from the west. The conglomerates consist in great part of pebbles and sub-angular blocks of green quartzite and a dark purple jasperoid slate with quartz veins, which rocks do not exist nearer than the Tapanui Mountains, west of the Clutha River, south-east of Lawrence; also, several other patches of conglomerates are found at the Blue Lead, Waitahuna, at Manuka Creek, &c., all of which probably mark the position of an old valley which extended from the Tapanui Mountains through the Blue Spur to Kaitangata. No appearance of such a valley can, however, be seen at present, and its supposed course is now crossed at right angles by the Clutha, and by the Tuapeka and Waitahuna Rivers. Consequently, this old valley must date back to a time previous to the formation of the present rivers, and, as we have already seen that the Clutha received the drainage of the pliocene glaciers of Maniototo, ldaburn, and the Manuherikia, we must place the existence of the Blue Spur glacier during a still earlier upheaval—that is to say, we must refer it to the Eocene Period."* Note.—I pointed out to a settler that there would probably be gold in the neighbourhood, running over to Brighton, and he tells me this is so. It might pay for hydraulicing, and is worth prospecting.
—Hutton, page 93.
I shall only quote one more authority—Dr. Archibald Geikie, L.L.D., F.R.S., in his "Class Book on Geology," page 458:—"From this kind of evidence it has been ascertained that the whole of Northern Europe, amounting in all to probably not less than 770,000 square miles, was buried under one vast expanse of snow and ice. The ice-sheet was thickest in the north and west, whence it thinned away Southward and eastward. Upon Scandanavia it was not improbably between 6,000 and 7,000ft. thick. It has left its mark at heights of more than 3,000ft. in the Scottish Highlands, and over North-Western Scotland it was probably not less than 5,000ft. thick. Where it abutted upon the range of the Hartz Mountains, it appears to have been still not far short of 1500ft. in thickness."
Ft. | In. | |
---|---|---|
Surface | 5 | 10 |
Lignite | 4 | 6 |
Coarse Sand | 1 | 4 |
Lignite | 3 | 6 |
Clay | 3 | 0 |
Sand | 2 | 0 |
Lignite | 1 | 4 |
Clay and Sand | 2 | 0 |
Sand | 4 | 6 |
Soft Lignite | 0 | 6 |
Clay | 2 | 0 |
Sand | 4 | 0 |
Dark Clay | 3 | 0 |
Sandy Clay | 1 | 0 |
Coarse Sand | 4 | 0 |
Lignite | 2 | 6 |
Clay | 3 | 9 |
White Clay | 2 | 0 |
Sand | 2 | 6 |
Fine Cl. y | 2 | 4 |
Black Sand | 4 | 0 |
Clay | 2 | 0 |
Coarse Sand | 10 | 0 |
Fine Sand | 4 | 0 |
Sand and Clay | 2 | 0 |
Sand | 17 | 6 |
Sand and Cement | 0 | 2½ |
Sand and Fireclay | 4 | 0 |
Sand | 5 | 0 |
Lignite | 2 | 9 |
Dark Clay | 4 | 6 |
Sandy Clay | 5 | 0 |
Sand | 5 | 9 |
Fine Sand | 48 | 6 |
Coarse Sand | 3 | 0 |
Light Solid Clay | 4 | 0 |
Hard Light Clay, with beds of sand | 12 | 10 |
Sandstone and Fireclay in beds | 4 | 8 |
Clay in beds of Sand-stone | 26 | 6½ |
Sandstone | 7 | 5 |
Hard Clay | 4 | 1 |
Now, the same state of things which would produce lignite seams, would produce leads of gold along the courses of streams, while during the heavier floods the stone would be more broken up that produced them, but the leads would be more concentrated at points where some hard bar or obstacle temporarily arrested the heavy rush of water and caught the gold in hollows. This, no doubt, was the case at Blue Spur. At Ross Flat, West Coast, six successive leads at different depths were found on sinking the main shaft down to 360 feet. I think, however, some mistakes have been made in predicting where leads would probably be found. No doubt, where a stream tipped its contents over into a lake, a catch would be established, and the free gold would not be carried far out towards the centre of the lake; but it page 17 must be remembered that besides the tree gold large quantities of slate and stones containing gold were carried forward, and gradually filled up the lake bed, and these, by their decay, have dropped their precious freight long after their deposit. Thus, as at Ross Flat, considerable quantities of gold may be found at successive levels over a large area of ground, and where a "face" can be got at a sufficient elevation to get a fall for the tailings, such ground will pay well for hydraulic sluicing on a large scale, as even a few grains to the load would leave a handsome result. There is room for much engineering skill in dealing with these various deposits, and much research by the practical geologist in determining the probable whereabouts of the best and most economically-worked ground. The young mining engineer of ability has a great future before him in this country, especially if he possesses, as he ought to possess, some knowledge of geology, mineralogy, and mechanics.
Generally speaking, Southland is a depression filled up in this way. Hence my belief that there is gold under your feet; where and how much can only be established by judicious and systematic prospecting and boring. But, generally, we may say that if the existing creeks and rivers contain gold, the terraces at their sides and the old river beds below will contain as much or more. There is here a field for a new department of the great science of geology. I may be permitted to coin, and call it "Glaciology." I admit that there is much for the geologist, and the mineralogist, and the chemist to do in other branches of historic and descriptive geology, but I think some men of ability among us should devote themselves specially to Glaciology, and I am sure its careful study would be fruitful of results, and principles knight be laid down of immense value to the hydraulic miner of the future. At present we can only deal with the poorer drifts by the use of immense quantities of water, and the creation of a vast quantity of waste material known as "sludge," which requires expensive channels I to carry it off. I am not at all certain that our present rough-and-ready system—which undoubtedly loses a great deal of gold—cannot be improved upon so as to economise water, and by mechanical appliances to keep the larger stones out of the channels—perhaps to crush them. The only limit at present to this class of mining is the water and the outlet fall, and Mr. Perry has, by his ingenious system, already overcome some of the difficulties of the latter by using water pressure to lift the materials to be washed to a considerable height. One good feature of hydraulic mining is that it is a steady industry, going on from year to year with few sensational results, but with a good return for capital and labour; and there is an immense field for it in Otago and parts of Southland. The use of thin steel plates for pipes is a great improvement.
And now I come to answer the question—