Hydrogeochemical and isotopic evidence for flow paths of karst waters collected in the Heshang Cave, Central China
Hydrogeochemical and isotopic evidence for flow paths of karst waters collected in the Heshang Cave, Central China
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DOI：
10.1007/s12583-015-0522-2
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发表时间：
2015-01
影响因子：
3.3
通讯作者：
Xiang Long;Ziyong Sun;Ai-guo Zhou;Deliang Liu
中科院分区：
文献类型：
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作者：
Xiang Long;Ziyong Sun;Ai-guo Zhou;Deliang Liu
从中国南部广西百色左登剖面二叠系-三叠系界线附近的微闪石沉积中提取了丰富的微螺蠕虫管。用光学显微镜和灵敏电子显微镜(SEM)分别对这些钙质蠕虫管进行了岩相薄片和分离标本的研究。它们被分为两种形态类型：螺旋盘管和平面螺旋盘管，可归类于异常微螺(Microconchus Ababrans)(Hohenstein，1913)和M。Utahesis(Zatoń等人，2013年)。管壁的超微结构以层状泥晶为特征，区别于可比的小型腹足类或螺旋状多毛类，后者的壳层超微结构通常具有晶石结构。微生物岩中绝大多数的微螺都具有平面螺旋盘管。现存的形态趋同的螺旋藻的生活方式表明，这些平面螺旋盘绕的微螺可能定居在一些局部的充氧绿洲中，可能是由缺氧微生物生态系统中的光合作用蓝藻产生的，在那里它们可能在不同个体之间以及与其他相关动物之间的高度竞争中定居，以争夺氧气消耗和食物来源。来自同一剖面的各种地球化学信号也反映了二叠纪-三叠纪生物破裂后不久微生物岩生态系统的有害环境条件。这种有害的栖息地可能不适合大多数后生动物居住，但它有一些当地的含氧绿洲，有利于机会主义分类群栖息。
Abundant microconchid worm tubes were extracted from the microbialites deposit near the Permian-Triassic boundary at the Zuodeng Section, Baise area, Guangxi Zhuang Autonomous Region, South China. These calcareous worm tubes were studied in both petrographic thin sections and isolated specimens using optical microscope and sensitive electronic microscope (SEM), respectively. They are categorized into two morphological types: helically coiled and planispirally coiled tubes, which are assignable toMicroconchus aberrans(Hohenstein, 1913) andM. utahesis(Zatoń et al., 2013), respectively. The tube wall ultrastructure is characterized by laminated micrites, which distinguish the studied microconchids from comparable microgastropods or spirorbid polychaete that usually has shell ultrastructure of spar texture. The overwhelm majority of microconchids from the microbialite possess the planispirally coiled tubes. The lifestyle of extant, morphologically convergent spirorbids suggests that these planispirally coiled microconchids may have colonized in some local oxygenic oases probably produced by photosynthetic cyanobacteria in the oxygen-poor microbialite ecosystem in which they may have settled densely with high competition among various individuals and with other associated animals for oxygen consumption and food soucres. The deleterious environment condition of the microbialite ecosystem immediately after the Permian-Triassic biocrisis is also indicated by various geochemical signals derived from the same section. Such a deleterious habitat may be inhospitable for most metazoans, but it has some local oxygenic oases that was favorable for opportunistic taxa to dwell.