中文摘要：

剖面研究揭示，重庆老龙洞地区二叠系一三叠系界线上下地层中发育厚约3m的微生物岩。该微生物岩的上部发育树枝状构造，下部具斑点状构造，因此被明显的分为上下两部分；其上部岩层顶面发育有侵蚀面，下部岩层顶面发育干裂缝。根据微生物岩上下岩层的沉积相分析和相关资料的对比研究表明，研究区在二叠纪-三叠纪之交，经历了暴露和侵蚀过程。研究结果为深入探讨这一重要地质时期的海平面变化提供了新的资料。

英文摘要：

This paper refers to a 3 m thick microbialite in the Permian-Triassic boundary section in Laolongdong, Chongqing. The microbialite comprises a dendroid upper part and a specked lower part. An erosional surface is found at the top of the upper part of the microbialite. Some dessication cracks occurred on the top surface of the lower part of the microbialite. Study on depositional environment of the microbialite indicates that the microbialite was emerged to the earth surface and eroded during the Permian-Triassic interval, which provides new data for the sea level changes across the Permian-Triassic boundary, an important geological epoch.