Organic compositions of the embryo-bearing lowermost Cambrian Kuanchuanpu formation on the northern Yangtze platform, China
Organic compositions of the embryo-bearing lowermost Cambrian Kuanchuanpu formation on the northern Yangtze platform, China
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DOI：
10.1016/j.palaeo.2009.07.002
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发表时间：
2009-09
期刊：
影响因子：
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通讯作者：
Yoko Kunimitsu;T. Togo;Y. Sampei;A. Kano;K. Yasui
中科院分区：
文献类型：
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作者：
Yoko Kunimitsu;T. Togo;Y. Sampei;A. Kano;K. Yasui
我们从沉积相、化石形态测量和有机地球化学（包括生物标志物组成）方面研究了中国陕西省寒武纪最下部宽川铺组的有机质起源和古海洋条件。结果表明，丰富的藻类和真核浮游植物为包括刺胞动物和小贝壳化石在内的多样化生态系统提供了燃料。水柱含有足够的氧气，可以为Olivooides等底栖刺胞动物提供栖息地。另一方面，低植烷/植烷比率、角鲨烷和藿烷成分的检测表明沉积物内的还原条件，并且氧化还原前沿可能靠近水-沉积物界面。黄铁矿和重晶石的常见存在表明硫物质的氧化还原反应在水-沉积物界面处被激活。这种情况和环境水中的高磷酸盐浓度可能让人想起促进动物胚胎磷酸化的硫氧化细菌的存在，正如新元古代陡山沱组中所暗示的那样。氮是初级生产力的限制性养分，海洋中高浓度的磷酸盐促进了动物胚胎在还原性水-沉积物界面处的磷酸化。
We investigated the origin of organic matter and paleoceanographic conditions of the embryo-bearing lowermost Cambrian Kuanchuanpu Formation in Shaanxi Province, China, in terms of sedimentary facies, fossil morphometry, and organic geochemistry, including biomarker compositions. The results indicated the abundance of algae and eukaryotic phytoplankton that fueled a diverse ecosystem including cnidarians and small shelly fossils. The water column contained enough oxygen to provide habitat for benthic cnidarians such as Olivooides. On the other hand, low pristane/phytane ratios, detection of squalane, and hopane composition indicate reductive conditions within the sediments, and that the redox front was likely near the water-sediment interface. Common occurrences of pyrite and barite indicate that redox reactions of sulfur species were activated at the water-sediment interface. Such circumstances and the high phosphate concentration in ambient water may recall the presence of sulfur-oxidizing bacteria that promoted the phosphatization of animal embryos, as suggested for in the Neoproterozoic Doushantuo Formation. Nitrogen was the limiting nutrient for primary productivity, and the high phosphate concentration in the ocean promoted the phosphatization of animal embryos at the reductive water–sediment interface.