The Nature Column.

Digger (Invercargill RSA), Issue 32, 22 October 1920, Page 6

The Nature Column.

(By "Student.")

("Student" will be pleased to receive notes on any braiach of Natural Historv Observations on birds, insects, plants, etc., will be equally welcome. ff using a peil-name, will correspondents please enclose rfeal name and address. ) Dear Student.— Where did the gravel come from? This subject the town bore has again brought to light. Of course it is natural to take the existing conditions and argue that the deposits have their origin from some river or rivers coming from the north or north-east. Now, gir in your theory regarding the Mataura river being the medium by which this deposit has reached its present position, does it not seem rather incongruous that this translucent quartz should come by a river having its aource in a country void of quartz, also the whole distance from there to its mouth runs through country where little if any quartz exists. The only theory which seems feasible in transit by the Mataura or Oreti must have been in the period long before the glacier in the Wakatipu valley blocKed its outlet by the moraine now existing at the Kingston end of the lake. Probably at a time ages ago the glacier would bring down quartz from out the Routeburn Dart or around the Earnslaw district, and the terminal end may not have been more than 60 miles from here. This could be possible to account for a vast deposit under the Southland plain. It would, however, in that case have come through the air gap straight through the Oreti. Ihe second theory advocated sets one thinkirig, and is perhaps the more probable one. Now at Awarua Bay' this gravel outcrops all along the beach nearer to the surface thi£n here, the fall apparent this way. That of course could have been altered by a warping of the land surface, but when cut in the Bluff line and at pits here and there, there does not seem any great faulting. The lay is from the south instead of from the north-east. According to Hutton, the Southland plain is Mana-

pouri pleistocene. Well, sir, if so, and it has every evidence of being so, how could it have come from the north-east where no Manapouri a.ge exists. The only possible land theory according to this is one that may have an origin in the Te Anau- Manapouri district long before the Takatimos were upflung a.nd may have come through north or west. It may be . advisable to- wait unt.il you have completed your little discourse promised next week. I think your subject is both interesting and instructive, and as the railway-advises one to iknow their own country first, one often wishes he did know it a little better. However, we do know something of the surface contour, but that is only to-day. What was yesterday? — I am, etc., NORLAND, Invercargill, October 20, 1920.

Those who maintain that the waterbearing gravels come to th© sea about the New River mouth, offer no evidence in support- beyond the fact that the Etrata seems to rise at Kew, and no water was got there. They further maintain that the white quartz gravels showing right dowm to Awarua Bay are only the upper layers of the strata overlying the water bearing gravels. But this gravel at Awarua Bay ig if anything several feet lower than the outerop at Gladstone. It must be conceded also that the gravels In question were transported to Awarua Bay by water, and seeing that they are abundant there, the river must have fiowed past the Bluff. The ancient river had a bend in it, and in ilowing past the Bluff would conform to the general rule that rivers flow along the strike of the rocks. The Bluff rock is of a granitic typo called norite. Rocks of a similiar type seem to run through Greenhills. From Greenhills to Riverton the water is shallow and the ground, in mariner's parlance in foul, or in other words rocky. Various rocky islets are scattered between the two points. Also as before stated rock outcrops at West Plains and is apparently of plutonic origin. From Riverton through the Longwoods granitic rocks occur and norite is found at Round Hill. Cont'muing in the same line a rock believed to be uorite occurs at the south arm of Manapouri, and up the Grebe Valley to Monowai. It seems fairly plain that a great ridge of plutonic rocks runs from Ruapuke to Lake Manapouri. The strike of these rocks is nearly at right angles to the supposed outlet of our underground water supply. Rivers sometimes do cut across the strike of the rocks, but in this qase, there is no evidence in support of such a presumption, while the fact that the white quartz gravels are found right down to the sea on the south, is strong presumptive evidence that the water passed in that direction. At any rate the

river must have fioweTZT^ in order to deposit the ^ To return to the grav^q stones are small and Well '1J \ there is a large amount 0f 4 derived from the same s evi(iewk gravel. Quartz is a very T*' ** % I and does not break up or 'r' I] nearly so easily as the 0thef II therefore follows that thtoe ft II travelled a great distance | at the Watenvorts ia gold b,,"! "«k A noteable feature about J round the Waterworks is the j || in several inst-ances trees wer! 401 ^ I in tlie lower strata, The WooT preserved, and this must be du' " | preservative agent in the water' I is present in the water and n v ^ |l certain amount of silica in 8ol.,n Uj » 1! present. These ar, I Ahove the trees are two seams of I] It seems strange that the later v 1 matter should have been converiT^' I lignite and the more deeplv ^ I be preserved. This, however is r ^ I together a singular occurrence \ / 1 Zealanff, as similar conditions [,(V 7* I met with in the Nort-h Island I wood taken from the latest'bore J ^ I been positively identified, but a I anist hazarded the opinion a few da« || that the tree had been a white pin?\? || wood iB now a deep reddieh brovvn ],, I] very fibrous and curly. Another I man of experience could not place { 2 I any timber now growing k Southland. i II piece of this wood is to be placed ,uu I museum along with the seetion 0| 2 I old tuai bore shown there. deep bore was put down a tree wmJ | with at 550 feet. - This wood on bafa! I exposed to the atmosphere, rapidly cW I j ed and became more like lignite. I j to last many thousands 0f years I have been rapidly covered to a ^ 1 Ot-herwi.se the agencies which now rapidly I di-spose of organio matter would havfl V destroyed or changed ita character. 8om» I of the wood which came out of the lat«t 1] bore had traces of the bark stili adhering | though worn and ruhl>ed as if it J I -been subject to abrasion such as would b» |1 csiiSicd by floatlng down. river I