Carbon-14 Dating Shown Reliable

Press, Volume CIII, Issue 30419, 18 April 1964, Page 12

Carbon-14 Dating Shown Reliable

The reliability of the Car-bon-14 method of determining the age of archaeological samples was demonstrated recently when a second post from the Canterbury Museum workings at Moa-bone Point Cave, Redcliffs, was tested by the Institute of Nuclear Science, Wellington, the director of the Canterbury Museum (Dr R. S. Duff) reported to the Museum Trust Board.

The sample was a butt of a 9in diameter totara post recovered from the Moa-bone site in 1962. Although the post could not be fitted into the plan of the main 40ft by 12ft structure found by Julius von Haast in 1862, its relation to the accompanying layers of the cave suggested that it was erected at the same period, said Dr. Duff. A similar post taken from the site and tested in 1962 had returned an age of 780 A.D. The director of the Institute (Mr T. A. Rafter) therefore was surprised when the recently submitted samples returned an age of 1310 A.I). —5OO years later, Dr. Duff said.

Checking back over the records of the earlier testing in an attempt to explain this Mr Rafter had found that through a clerical error in his report of 1962, the date of 780 A.D. referred to a sample of charcoal from a Moa hunter oven on the property of Miss Philipa Hamilton, which had been submitted together with the first post, which had in turn given a reading of 1310 A.D.

The two posts were then demonstrated to be respectively 1304 A.D. and 1310 A.D which in terms of radio carbon meant that they could have been erected at the same time, he said.

The same result from the second post tested several years after the first, proved the reliability of the Carbon dating process, Dr Duff said. The date of 780 A.D. for the oven of the Redcliffs flat property thus became the oldest reliable date for Polynesian occupation in New Zealand. Less Reliable After several years’ experience in analysing timber and Moa bone samples found at the same level in archaeological sites from the museum’s operations at Redcliffs, Mr Rafter had concluded that Moa bone was less reliable for dating than timber, as it tended to give a result several hundred years later in each case, Dr. Duff said. Mr Rafter has also told Dr. Duff that the first carbon-14 date from a sample of shell from the Moa-Hunter site at the mouth of the Heaphy river on the West coast demonstrated that the small Anomalopteryx moa was probably hunted as late as 1518 by a community still using adzes, fish hooks and ornaments of MoaHunter type. A charcoal sample mixed with Moa midden bones, taken from a site at Paramata, near Wellington, by Mr E. D. Sinclair, of Wellington, and submitted to the institute through the Canterbury Museum, had indicated that moa-hunting was still active In the area in 1436 A.D., said Dr Duff.