Detrital zircon from a Timiskaming conglomerate near Kirkland Lake, Ontario, gives a uranium-lead age of 2,700 m.y.+ or -3 percent and muscovite from the same rock gives a potassium-argon (metamorphic) age of 2,410+ or -50 m.y. In Hastings conglomerate near Madoc, Ontario, detrital zircon age of crystallization is 1,140 m.y.+ or -3 percent and the potassium-argon ratio of muscovite indicates metamorphism at 898+ or -20 m.y. These results may be interpreted as suggesting that the conglomerates have been derived from source rocks which formed in the same geological cycle, without the intervention of a major orogeny prior to sedimentation and final folding and metamorphism of the conglomerates.

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