华南二叠系长兴阶灰岩的碳同位素地层对比

Carbon Isotope Cyclostratigraphic Correlation of the Upper Permian Changhsingian Limestones in South China

以浙江长兴煤山长兴阶层型剖面、江西上高七宝山剖面、陕西汉中梁山剖面为代表的华南长兴阶碳酸盐岩碳同位素地层，清楚地显示出长兴阶顶、底为碳同位素低值区，其中Ｐ－Ｔ界线附近的碳同位素出现强烈负异常事件。在长兴阶内部两次碳同位素低值异常区，将长兴阶碳同位素演化曲线由下至上明显分为３个旋回，其中长兴阶顶，也即Ｐ－Ｔ界线，碳同位素强烈负异常与生物绝灭事件有关，时间短，变化幅度大，是全球界线对比的重要标志。而其它碳同位素负漂移和由此构成的３个旋回，在华南可以追踪对比。上旋回与长兴阶上段煤山段相当；而中、下旋回则与下段葆青段相当，并将其两分。碳同位素地层对比表明江西上高地区长兴组的中、上部可能属长兴阶，而下部厚约９０ｍ的含Ｇａｌｏｗａｙｉｎｅｌａ灰岩可能属吴家坪晚期。

Study of the carbon isotopic stratigraphy of the Upper Permian Changhsingian limestones in the Meishan Section D in Changxing, Zhejiang, the Qibaoshan Section in Shanggao, Jiangxi, and the Liangshan Section in Hanzhong, Shaanxi shows that three cycles of carbon isotope stratigraphy may be recognized in the Changhsingian Stage. Its onset and termination are most likely to be sharp events that provide stratigraphic markers of high precision in the Changhsingian limestones in South China. These are ascendingly: Palaeofusulina minima cycle (the lower Changhsingian), Crurithyris Geinitzina Clarkina subcarinata cycle (the middle Changhsingian) and Palaeofusulina sinensis cycle (the Upper Changhsingian). Carbon isotopic stratigraphic correlation suggested that the middle and upper Changxing Formation in Shanggao, Jiangxi, may be designated to the Changhsingian stage, while the 90 m thick sediments of the lower “Changxing Formation” with Gallowayinella meitienensis is probably of late Wuchiapingian age.