摘要：

中国西南部云贵交界地区中上三叠统海相地层以拥有丰富的海生爬行动物化石为特色的古生物群落而闻名。近期,笔者在云贵交界地区发现了一个完整的中上三叠统竹杆坡组至上三叠统小凹组剖面,即云南罗平江底剖面。在该剖面中,分别在竹杆坡组纹层灰岩段顶部及小凹组上部发现了典型的兴义动物群及关岭生物群生物组合。为了研究中晚三叠世之交生物群落演化的环境背景,对采集的97件地球化学样品进行了常量、微量及稀土元素测试与分析。微量和稀土元素的分析结果表明,竹杆坡组纹层灰岩段及小凹组处于缺氧环境,产兴义动物群及关岭生物群的地层含氧量相对增加,而两生物群落之间的竹杆坡组瘤状灰岩段主要为贫氧环境。中晚三叠世之交的海水含氧量的变化规律与生物群落的演替较为吻合,说明该时期海水含氧量的变化对生物演替具有一定的控制作用。

关键词: 云南, 贵州, 中上三叠统, 微量元素, 稀土元素, 氧化还原环境, 兴义动物群, 关岭生物群

Abstract:

The Middle-Upper Triassic marine strata in the boundary area of Guizhou and Yunnan Provinces are famous for the well-developed marine reptile fossils and other palaeobiocenoses. In the Jiangdi section found recently by the authors,both Zhuganpo Formation and Xiaowa Formation are successive and well exposed. The representative Xingyi Fauna and Guanling Biota were found at the top of laminated limestone Member in Zhuganpo Formation and in the upper part of Xiaowa Formation,respectively. In order to certify the environment in which the biotic communities were living,97 samples from Jiangdi section were collected for both major and trace elemental analysis. According to the results,the Xiaowa Formation and the laminated limestone of Zhuganpo Formation were deposited in the oxgen-deficient environment. The oxgen content increased in the strata of Xingyi Fauna and Guanling Biota. However,in the interval nodular limestone between the two biotas,the environment might be anoxic. The coincidence of oxygen content change and the biotic communities evolution may indicate that the oxygen content played a certain control role in the biotic succession.

Key words: Yunnan, Guizhou, Middle-Upper Triassic, trace element, REE, redox environment, Xingyi Fauna, Guanling Biota

中图分类号: 

• P595