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[en] Strontium isotopic and stratigraphic data collected from the Darai Limestone of Papua New Guinea clearly demonstrate a systematic relationship between bulk 87 Sr/86 Sr ratio and index foraminiferal composition that closely reflects the relative stratigraphical range of the foraminifera in this region. A graphic correlation of stratigraphic, strontium isotopic and age ranges of the major index taxa permits direct evaluation of limestone age and isotopic composition in the Darai Limestone. The age of the Tf 1/Tf 2 boundary (∼ 12.2 Ma) is significantly younger than the accepted estimate of∼ 15.0 Ma (plankton Zone N9) and the Te/Tf boundary (∼ 20.3 Ma) is older than the generally accepted age of∼ l 8.5 Ma (plankton Zone N6)