Opening up a window into ecosystems with Ediacara-type organisms: preservation of molecular fossils in the Khatyspyt Lagerstatte (Arctic Siberia)
Opening up a window into ecosystems with Ediacara-type organisms: preservation of molecular fossils in the Khatyspyt Lagerstatte (Arctic Siberia)
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DOI：
10.1007/s12542-016-0317-5
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发表时间：
2016-12-01
影响因子：
--
通讯作者：
Grazhdankin, Dmitriy
中科院分区：
文献类型：
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作者：
Duda, Jan-Peter;Thiel, Volker;Grazhdankin, Dmitriy
北极西伯利亚的Khatyspyt组是仅有的两个具有Ediacara型化石的碳酸盐岩环境之一。作为一种潜在的烃源岩，它含有丰富的分子化石，可能有助于扩大我们对这些生态系统的了解。然而，不幸的是，地质材料中的分子化石记录通常会受到次生过程的影响，如热成熟、沥青化合物的迁移或表面污染。在这项研究中，我们评估保存的分子化石样品从Khatyspyt组和阐明其古生物学意义。研究结果表明，有机质未成熟程度明显（油窗成熟度），生物降解作用不明显。岩相学观察，外部/内部实验，以及自由沥青，矿物包裹沥青和干酪根热解物之间的相似性指向分子化石的同生。丰富的藿烷、环己基烷烃和甲基支链烷烃表明有机物质的细菌来源，可能包括蓝藻和厌氧菌。同时，样品顶部的碳质压缩化石和丰富的甾烷表明真核生物的存在。甾烷显示埃迪卡拉纪的典型分布（即，豆甾烷的优势）。由于身体化石、遗迹化石和分子化石的特殊保存，Khatyspyt组可以被认为是化石lagerstatte sensu Seilacher（1970：Begriff und Bedeutung der Fossil-Lagerstatten. Neues Jahrbuch fur Geologie und Palaontologie，Monatshefte：34-39）.沉积相、古生物学（体、痕迹和分子化石）和地球化学的综合分析将提供对埃迪卡拉类化石生态系统的更完整的理解。
The Khatyspyt Formation in Arctic Siberia is one of only two carbonate settings with Ediacara-type fossils. As a potential hydrocarbon source rock, it contains abundant molecular fossils that may help to expand our understanding of these ecosystems. Unfortunately, however, the molecular fossil record in geological materials is commonly biased by secondary processes such as thermal maturation, migration of bitumen compounds or surface contamination. In this study, we evaluate the preservation of molecular fossils in a sample from the Khatyspyt Formation and elucidate their paleobiological meaning. Our results reveal that the organic matter is remarkably immature (oil window maturity) and shows little effect of biodegradation. Petrographic observations, exterior/interior experiments, and the similarity between free bitumen, mineral-occluded bitumen, and kerogen pyrolysate point to the syngeneity of the molecular fossils. Abundant hopanes, cyclohexylalkanes, and methyl-branched alkanes indicate a bacterial source of the organic matter, likely including cyanobacteria and anaerobic bacteria. At the same time, a carbonaceous compression fossil on top of the sample and abundant steranes indicate the presence of eukaryotes. The steranes show typical distributions for the Ediacaran (i.e., dominance of stigmastane). Given the exceptional preservation of the body fossils, trace fossils, and molecular fossils, the Khatyspyt Formation can be considered a fossil lagerstatte sensu Seilacher (1970: Begriff und Bedeutung der Fossil-Lagerstatten. Neues Jahrbuch fur Geologie und Palaontologie, Monatshefte: 34-39). The combined analysis of sedimentary facies, paleontology (body, trace, and molecular fossils), and biogeochemistry will provide a more complete understanding of ecosystems with Ediacara-type fossils.