ANCIENT ROCKS OF SOUTHLAND

Southland Times, Issue 23827, 26 May 1939, Page 3

ANCIENT ROCKS OF SOUTHLAND

DISCOVERIES MADE AT PRESERVATION TALK TO ROYAL SOCIETY BY PROFESSOR BENSON The geology of Southland and Stewart Island was the subject of an illustrated address by Professor W. N. Benson, professor of geology at Otago University, at a meeting of the Southland branch of the Royal Society last night. Dr G. H. Uttley presided over a good attendance. Dr Uttley said Professor Benson was a distinguished geologist whose reputation had extended far beyond the shores of New Zealand. The great work he had done had been recognized in London, where he had been awarded the Lyell Medal by the Geological Society. Professor Benson said there was still a great deal to learn about Southland, and there was not much literature on the subject. He explained the means by which geological ages were determined, saying that the geologist could adopt time scales much in the same way as the historian could deal with things ! n periods. All the geologist wanted to know was the relative order in which things occurred. By how many years they preceded one another and the rate at - ’hich things happened were of less importance. Things which carried the same lot or species of fossils were more or less contemporaneous, because the rate of accumulation of fairly deep sea sediments was so slow that the organisms in it could migrate for long distances. Time, as a geologist had to deal with it, stretched over a period of roughly 2,000,000,000 years and it had been estimated that man had lived on the earth for 1,000,000 years. The oldest rocks in New Zealand were in the Preservation Inlet area, where a series of fossils of the ordovician period had been discovered. The whole of the Preservation area was once an open sea area, and not an area of mountain and fiord. It was a shallow sea, full .of weed which had decomposed, and a black, shiny mud. was laid down. Professor Benson described, with the aid of lantern slides, several of the graptolitc forms found at Preservation Inlet and at Cape Providence. Delicate ripple marks on rocks indicated impressions made when the rocks were being formed on the sea bed 400,000,000 years ago.

The speaker described certain geological features in the Greenhills quarry in the Bluff area where, he said, there was an old volcanic ash. Along the coast of Stewart Island were the same sort of rocks that would be found at Bluff—a hybrid material with granite injected into it. Stewart Island represented the same sort of material that might be expected in the middle part of the fiord district. It was, indeed, a fragment of Fiordland in that it had dropped a bit of its “roof” down on itself. Professor Benson showed many slides of fossil forms, rock formation at Preservation Inlet and the effect of glaciation in the fiord district. At the conclusion of the address Mr F. M. Corkill moved a hearty vote of thanks, which was carried enthusiastically.