FTIR microspectroscopy of Ediacaran phosphatized microfossils from the Doushantuo Formation, Weng'an, South China
FTIR microspectroscopy of Ediacaran phosphatized microfossils from the Doushantuo Formation, Weng'an, South China
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DOI：
10.1016/j.gr.2013.05.002
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发表时间：
2014-04
影响因子：
6.1
通讯作者：
M. Igisu;T. Komiya;M. Kawashima;S. Nakashima;Y. Ueno;Jian Han;D. Shu;Yong Li;Junfeng Guo
中科院分区：
文献类型：
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作者：
M. Igisu;T. Komiya;M. Kawashima;S. Nakashima;Y. Ueno;Jian Han;D. Shu;Yong Li;Junfeng Guo
化石来源于钙磷酸化微体化石。利用傅里叶变换红外光谱（FTIR）技术对中国南方瓮安地区陡山沱组580 Ma的岩石进行了显微化学特征分析。本文分析了两种形态类型的磷酸盐化类胚化石（Megasphaera和Megaclonophycus）以及藻类化石。微体化石的透射红外光谱在2960 cm− 1和2925 cm− 1附近有吸收带，表明存在脂肪烃（反对称脂肪CH 3和脂肪CH 2），在1595 cm− 1附近有一个额外的吸收带，可能来自芳香部分（芳香C双键C）。此外，红外显微图谱显示，胚状化石内部分布有脂肪烃和芳烃。胚胎样化石的CH 3/CH 2峰高比（R3/2）和芳香C双键C/CH 2峰高比有三种类型（RC双键C/2值）：（1）高R3/2/低RC双键C/2型（2）低R3/2/中RC双键C/2型（3）低R_3/2/高RC双键C/2型（R_3/2 =~ 0.2 - 0.6，RC双键C/2= ~ 1-8）。所有这三种类型都包含在Megasphaera和Megaclonophycus中。岩石样品中碳质物质的拉曼光谱显示出相似程度的热蚀变，表明有机物在热成熟之前就被原位嵌入。红外光谱的差异可能反映了微生物的原始有机成分的差异，和/或立即死后的变化。这表明磷酸盐化的胚胎状化石的起源比以前根据其形态学认识到的更多样化。通过与藻类化石和现存微生物的R ~（3/2）和RC双键C ~（2/2）值的比较，提出了一种可能的解释，即这些类胚化石中有些是动物胚胎，有些是藻类，但没有一种是细菌。
Phosphatized microfossils from ca. 580 Ma from the Doushantuo Formation in the Weng'an region of South China were analyzed by Fourier transform infrared (FTIR) microspectroscopy for their chemical characterization. Two morpho-types of phosphatized embryo-like fossils (MegasphaeraandMegaclonophycus) were analyzed, together with algal fossils. Transmission IR spectra of the microfossils have absorption bands of around 2960 cm− 1and 2925 cm− 1, indicating the presence of aliphatic hydrocarbon (anti-symmetric aliphatic CH3and aliphatic CH2), and have an additional band of around 1595 cm− 1, probably derived from aromatic moieties (aromatic Cdouble bondC). In addition, IR microscopic mapping shows that aliphatic hydrocarbon and aromatics are distributed inside the embryo-like fossils. The embryo-like fossils appear to show three types of CH3/CH2peak height ratios (R3/2) and aromatic Cdouble bondC/CH2peak height ratios (RCdouble bondC/2values): (1) high-R3/2/low-RCdouble bondC/2type (R3/2= ~ 0.2–1.0 and RCdouble bondC/2~ 0–2), (2) low-R3/2/medium-RCdouble bondC/2type (R3/2= ~ 0.2–0.6 and RCdouble bondC/2= ~ 1–4); and (3) low-R3/2/high-RCdouble bondC/2type (R3/2= ~ 0.2–0.6 and RCdouble bondC/2~ 1–8). All three types are contained in bothMegasphaeraandMegaclonophycus. Raman spectra for the carbonaceous matter within the rock sample show a similar degree of thermal alteration, indicating that the organics were embedded in situ prior to thermal maturation. The IR spectroscopic differences might reflect differences in original organic compositions of microorganisms, and/or immediate post-mortem alteration. This suggests that the origins of phosphatized embryo-like fossils are more diverse than was previously recognized on the basis of their morphology. A comparison of R3/2and RCdouble bondC/2values in the embryo-like fossils with those of the algal fossils and the extant microorganisms indicates the possible interpretation that some of the embryo-like fossils belong to animal embryo, others are algae, but none of them originate from bacteria.