Abstract

A Cretaceous arkosic sandstone from southwestern New Caledonia contains detrital zircon most of which is clear and euhedral. However, about 1 percent is rounded colored grains. The uranium-lead and thorium-lead data for the bulk zircon concentrate indicate discordant Cretaceous ages. The Pb207/Pb206 age is 670 ± 30 m.y. Reasonable arguments for the use of 65 m.y., the minimum age of sedimentation, for the lower intercept of this data point on a concordia diagram extrapolate to a minimum age of 1,000 m.y. for the oldest zircon component. The likely source of these zircons is the Lord Howe Rise which is proposed to be a submerged continental link between New Zealand and Australia.

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