云南罗平江边地区中三叠统关岭组二段古环境特征

罗平生物群赋存于中三叠统关岭组二段中部，是二叠纪末生物大灭绝后生物复苏与辐射的典型代表。通过对云南罗平江边村剖面的关岭组二段进行宏观沉积组构、微相分析和元素地球化学分析，重建了罗平生物群赋存层位的沉积环境和古海洋条件。根据沉积相展布和地球化学指标的变化，恢复出四个沉积阶段。阶段Ⅰ主要为局限台地、开阔台地相:Mo_EF、V/Cr较低，U_EF中等，指示氧化—次氧化环境；阶段Ⅱ主要为潮坪、局限台地环境:Mo_EF、U_EF、V/Cr均较低，指示氧化环境；阶段Ⅲ主要为台盆相:表现出Mo_EF、U_EF、V/Cr显著升高，指示缺氧环境；阶段Ⅳ主要为潮坪、浅滩、开阔台地环境:Mo_EF、V/Cr较低，U_EF中等，指示氧化—次氧化环境。罗平生物群主要产于阶段Ⅲ缺氧的台盆环境中，说明缺氧和较为封闭和稳定的盆地环境在罗平生物群化石的特异埋藏过程中，扮演了重要角色。

Paleoenvironment Analyses of the Second Member,Middle Triassic Guanling Formation in Luoping Jiangbian,Yunnan

The Luoping biota has been preserved in the middle of the second member of the Guanling Formation of the Middle Triassic， and is typical of the biological recovery and spreading that took place after the mass extinction at the end of the Permian. The paleoenvironment of the second member of Guanling Formation in the Jiangbian village section， Luoping county， Yunnan province， was analyzed for microfacies and sedimentary geochemical compositions. The diagnosis of the sedimentary facies and a few paleoenvironmental proxies indicated that these strata underwent four sedimentary stages. Stage I mainly comprise restricted platform and open platform facies characterized by low MoEF， V/Cr and medium UEF， indicating an oxic-suboxic environment. Stage II deposits are mainly tidal flats with restricted platform facies， as indicated by relatively low MoEF， UEF and V/Cr typical of an oxic environment. Stage III mainly consists of intraplatform basin facies characterized by significantly high MoEF， UEF， and V/Cr， suggesting an anoxic environment. Stage IV comprises mainly tidal flat deposits with shoal and open platform facies characterized by low MoEF， V/Cr and medium UEF， indicating an oxic-suboxic environment. The Luoping biota was mainly preserved in Stage III， implying that anoxia played an important role in the extraordinarily well-preserved Middle Triassic marine reptiles and other marine fossils.