TY - JOUR
T1 - FTIR microspectroscopy of Ediacaran phosphatized microfossils from the Doushantuo Formation, Weng'an, South China
AU - Igisu, Motoko
AU - Komiya, Tsuyoshi
AU - Kawashima, Mika
AU - Nakashima, Satoru
AU - Ueno, Yuichiro
AU - Han, Jian
AU - Shu, Degan
AU - Li, Yong
AU - Guo, Junfeng
AU - Maruyama, Shigenori
AU - Takai, Ken
N1 - Funding Information:
The major part of this study was conducted at the Japan Agency for Marine-Earth Science & Technology (JAMSTEC). We thank Jasco Co, Ltd. and ThermoFisher Scientific Co. for their technical support with the IR microspectroscopic analyses, and three anonymous reviewers for their constructive comments on the manuscript. This research was partly supported by the 21st Century COE program ‘How to build habitable planets’, Tokyo Institute of Technology, sponsored by the Ministry of Education, Culture, Sports, Technology and Science, Japan . M.I. is supported by MEXT KAKENHI ( 22740351 ) and the Research Fellowship of Japan Society for the Promotion of Science for Young Scientists . T.K. is supported by grants for “Multistep evolution of the Metazoa (No. 23340152)” and by the Mitsubishi Foundation .
PY - 2014/4
Y1 - 2014/4
N2 - Phosphatized microfossils from ca. 580Ma 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 (Megasphaera and Megaclonophycus) were analyzed, together with algal fossils. Transmission IR spectra of the microfossils have absorption bands of around 2960cm-1 and 2925cm-1, indicating the presence of aliphatic hydrocarbon (anti-symmetric aliphatic CH3 and aliphatic CH2), and have an additional band of around 1595cm-1, probably derived from aromatic moieties (aromatic CC). 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/CH2 peak height ratios (R3/2) and aromatic CC/CH2 peak height ratios (RCC/2 values): (1) high-R3/2/low-RCC/2 type (R3/2=~0.2-1.0 and RCC/2~0-2), (2) low-R3/2/medium-RCC/2 type (R3/2=~0.2-0.6 and RCC/2=~1-4); and (3) low-R3/2/high-RCC/2 type (R3/2=~0.2-0.6 and RCC/2~1-8). All three types are contained in both Megasphaera and Megaclonophycus. 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 R3/2 and RCC/2 values 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.
AB - Phosphatized microfossils from ca. 580Ma 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 (Megasphaera and Megaclonophycus) were analyzed, together with algal fossils. Transmission IR spectra of the microfossils have absorption bands of around 2960cm-1 and 2925cm-1, indicating the presence of aliphatic hydrocarbon (anti-symmetric aliphatic CH3 and aliphatic CH2), and have an additional band of around 1595cm-1, probably derived from aromatic moieties (aromatic CC). 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/CH2 peak height ratios (R3/2) and aromatic CC/CH2 peak height ratios (RCC/2 values): (1) high-R3/2/low-RCC/2 type (R3/2=~0.2-1.0 and RCC/2~0-2), (2) low-R3/2/medium-RCC/2 type (R3/2=~0.2-0.6 and RCC/2=~1-4); and (3) low-R3/2/high-RCC/2 type (R3/2=~0.2-0.6 and RCC/2~1-8). All three types are contained in both Megasphaera and Megaclonophycus. 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 R3/2 and RCC/2 values 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.
KW - Algal fossils
KW - Aliphatic hydrocarbon
KW - Doushantuo Formation
KW - Embryo-like fossil
KW - Micro-FTIR
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U2 - 10.1016/j.gr.2013.05.002
DO - 10.1016/j.gr.2013.05.002
M3 - Article
AN - SCOPUS:84893756489
SN - 1342-937X
VL - 25
SP - 1120
EP - 1138
JO - Gondwana Research
JF - Gondwana Research
IS - 3
ER -