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利用海绿石４０Ａｒ－３９Ａｒ年龄校正公式，通过测量海绿石中的可膨胀层含量ｎ以及中子活化过程中３９Ａｒ的丢失率，求出海绿石的年龄。经测定，京津地区铁岭组、景儿峪组海绿石中可膨胀层含量为５％～６％，中子活化中３９Ａｒ丢失率为１７％～１９％。由校正后的海绿石年龄推测出铁岭组年龄界限范围是１０７０±１０Ｍａ～１１７５±１０Ｍａ，景儿峪组为８１０±１０Ｍａ～９００±１０Ｍａ。
Using the 40Ar-39Ar age correction formula of glauconite, the age of glauconite was obtained by measuring the expansive layer content n in glauconite and the loss rate of 39Ar during neutron activation. It has been determined that the content of expansive layer in glauconite of Tieling Formation and Jing’eryu Formation in Beijing-Tianjin area is 5% -6%, and the loss rate of 39Ar in neutron activation is 17% -19%. The age range of Tieling Formation is 1070 ± 10Ma ~ 1175 ± 10Ma, and the JingErY Formation is 810 ± 10Ma ~ 900 ± 10Ma.