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Permian Triassic Systems and Their Mutual Boundary — Memoir 2, 1973
Permian-Triassic Radiometric Time Scale
Philip O. Banks
Radiometric ages published since 1964 indicate that the boundaries of the Triassic Period are somewhat older than previously believed. A conservative estimate places the Triassic-Jurassic boundary at 200-205 m.y. and the Permian-Triassic boundary at about 235 m.y., although some authors have suggested even greater ages. The currently accepted age of 280 m.y. for the Carboniferous-Permian boundary remains unchanged but should probably be considered a minimum value.
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