NORTH ISLAND GLACIATION.

Otago Witness, Issue 2892, 18 August 1909, Page 18

NORTH ISLAND GLACIATION.

PROFESSOR PARK'S VIEWS. Professor Park, at a meeting on the 16th inst. of the Otago Institute, said he wished to bring under the notice of the society some important evidence of ancient glaeiation he had recently discovered in the western part of the province of Wellington. He stated that the triangular area lying between the Manawatu River and Wanganui is occupied by a gravel drift, 400 ft or 500 ft thick, which, along its inland border, rests against a series of marine clays of the pliocene age that are horizontal or dip gently towards the sea. These clays along their northern limit skirt the upland plains that wrap around Ruapehii. In a. few places they are intercalated with thin beds of shelly lime6tone or irregular layers of hard calcareous nodules. The gravels comprise the coastal country (highly cultivated), and the cla3 r s are found inland over the hills j and ridges covered with densa forest, and still further inland where there are 40 or 50 miles of undulating grass land. Through this country flowed a number of rivers— Rangirikei, Bautapu, Turakina, and Wangaehu. Beginning at Waiouru, on the inland grass lands, and proceeding east- i ward, the hills are foundi to present the ! smooth, flowing outlines, truncated crests, and terraced slopes characteristic of glaoial erosion. The higher hills are dome-enaped, the lower hummocky and whale-backed in form. At Taihape the hills are beautifully rounded, coned, and domed ; at Mataroa there is a fine example of a U-shaped valley. A large stretch of country,- from Karioi, near, Ruapehu, across the ridges to Hautapu Valley, is covered with a snoet of glacial boulder «lay or till. The till consists of clays, or clajs mixed with andesite blocks, or andesite blocks alone. It is mostly unstratificd. The boulders range from- small blocks up to masses six to eight feet in diameter. The thickness of the till varies from nothing to 60ft, so far as may be seen, and in many places rests on hill summite 300 ft and 400 ft above the floor of the old glacial valley. On the Waiouru plateau amie&it* boulders are present in large number 2660 ft above sea level. Above Taihape blocks are abundant ; below clays predominate. The latter extend down the Hautapu Valley for 26 miles, ending near Uticu at a height of 1220 ft above the sea. The andesite blocks have travelled 45 miles from their source at Ruapehu, and are spread over a width of ground varying so far a3 may be seen, from two to five miles. Thx- andesitic material has been transported over a ridge of hills 600 ft to 900 ft high above- the Karici Flat, from the slopes of Ruapehu to its present position by ICP It would appear that there was a differential movement in the Ruapehu Glacier, the bottom stream going south through the Karioi Basin, and along the Whangaehu Valley, and the upper and greater stream flowing south-east across the divide into Hautapu Valley, carrying a load of andesitic debris. The deeply eroded surface of the marine pliocene clays show its tracks, and the- old glacial valley can be easily traced, from any high point of view. The Rangi-tik-ei Glacier flowed southward from the Kaimanawa Mountains and Ruahine Range, and deflected the Hautapu Glacier westward towards the Turakina. These mountains are . composed of argillite and greywacke : h-ence, until it met the Hautapu Glacier near i Uticu, the Bangitikei Glacier carried only j argillite and greywacke boulriein. ! The Professor pointed out that Ruapehu ! is only one and a-half degrees further north i than Boulder Lake, in Coliingwood, the ! most northerly point at which evidence of ' ancient glaciabion is known in the South I Island. He considered the Hautapu till j too widespread and variable to be regarded as a terminal or lateral moraine ; therefore it must be boulder clay or till formed mainly of inter-glacial debris deposited by the Hautapu Glacier as it retreated on its centre of movement at Ruapehu. The Prof essor then proceeded to argue that this sjiaeial period muet have been in the pleistocene age, which made New Zealand's ice age contemporaneous with that of the Northern- Hemisphere. In this period Ruapehu was a centre of dispersion, from which glaciers radiated * into the

JRa-xi^-itikei. Wangaehu, TLTpper Wanganui, and Upper Waikato, the latter fk&ving into Taupo Basin., through Rangipo Desert. Professor P. Marshal! stated that he did not at all agree with Professor Park's views. The Ruapehu country was country with which he was perfectly familiar. He did not regard its appearance as being due to glacial action : it was, he believed, solely the result of river action- At a conparatively recent geological period it had been on the sea floor. It had been raised up 4000 ft by degrees, and rivers had thereby flowed all over ifc^ depositing the gravels ajKjken of. Proi'e&sor Park spoke of, and no doubt regarded, them as tills. But to the speaker they were nothing more than river gravels, deposited at different times. After referring to certain geographical feature.? of the country, Professor Marshall said that Ruapehu had been examined by many geological students, who had quite failed to discover the de«p scored valleys or any other signs of glaciation. He personally had gone there in his young days, hoping to distinguish him&clf. but he had come away again without having found any proof of glaeiation. He considered that there were no traces of glaeiation in any of the mountain ranges refened to by Professor Park; but that depended, after all, in what way different geologists read certain sign*. He would personally regard the boulder clay, if he looked at it in the same light as Professor Park looked at it, as undoubted proot ot glaeiation at Tongariro. for it was to b» found there. How did Proiessor Park account for the absence of erratics, which should have been present >n the case or such a glacier as had been described l. Vt course they might occur, but had not been described. And surely there wou'd have been a terminal moraine as p.ainly •distinguishable as that at the Taieri, in tne case of a glacier 45 miles long. Professor Marshall concluded by saying that many geologists had given their decisions against the theory of a glacial period in any part of the North Island. Mr G. M. Thomson, M.P.. said that all botanical evidence was dead against the glaeiation theory so far as he Knew. Professor Park, in replying, said that Professor Marshall wae under an entire misapprehension. There was no river gravel or water-worn material in the deposit, which consisted of piles of angular volcanic blocks that were largest and most numeious, at the southern limit— that ife. farthest from their source at Ruaprha, which, of course, would >.ot ho the case with river material.

He was the only geologist who had made a. detailed examination of that country, having spent the summer of 1886-87 making a geological survey of the Main Trunk route- as far as Ruapehu on behalf of tho New Zealand Government. The evidence that he had now brought forward was quite new to geologists, the country over which, the deposit was spread baing covered witH dense forest until quits recently. There was, Professor Park said, no other agency than ice capable of transporting such masses of rock so far from their source and spreading them over hill and dale.