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本文研究了贵州望谟乐康深水槽谷相二叠／三叠系界线剖面的有机碳同位素记录。研究结果表明，乐康剖面上二叠统δ13Corg值的变化幅度不大，越过第34层进入第35层以后，在WL－16号样品层位上，δ13Corg值突然从WL－15号样品的-25．419‰降低到-28．235‰，衰减幅度达到近3‰；其后δ13Corg值逐渐回升，并进入下三叠统。根据δ13Corg值的突然衰减正好发生在第34，35层的界线过渡层内这一事实，我们认为乐康剖面的P／T界线应划在第35层的WL－16号样品层位上。由于沉积有机物的碳同位素组成与海洋生物原始生产率（primaryproductivity）密切相关，因此，贵州乐康二叠／三叠系界线剖面的有机碳同位素变化曲线，不仅可以作为精确划分地层界线的一种新的有效手段，而且反映了海洋原始生产率的变化情况。
In this paper, the organic carbon isotope records of the Permian-Triassic boundary line in the Lekang deep sink in Wangmo, Guizhou Province, are studied. The results show that the δ13Corg value of the Permian section of the LeKang section is not greatly changed. After entering the 35th layer beyond the 34th layer, the δ13Corg value of WL-16 layer suddenly rises from the WL- 25.419 ‰ reduced to -28.235 ‰, the attenuation reached nearly 3 ‰; δ13Corg values gradually rebounded and entered the Lower Triassic. Based on the fact that the abrupt decay of the δ13Corg occurs exactly in the boundary transition layers of the 34th and 35th layers, we believe that the P / T boundary of the LeKang section should be located on the 35th layer of the WL-16 sample horizon. Because the composition of carbon isotopes of sedimentary organic matter is closely related to the primary productivity of marine organisms, the organic carbon isotopic variation curves of the Permian / Triassic boundary sections of LeKang not only serve as a new effective method for accurately dividing the stratigraphic boundaries Means, but also reflect changes in the original productivity of the oceans.