The generality of preservation of organic remains in body fossils by FTIR spectra

¹College of Life Sciences, National Chung Hsing University, Taichung, Taiwan, China

²DERC and ICFS of Jilin University, Changchun, Jilin 130012, China

³National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, China

⁴Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, L5L 1C6, Canada

^*Correspondence and request for materials should be addressed to  email: timd_huang@yahoo.com.

Abstract

Each chemical bond has unique vibration energy, which yields a certain characteristic peak(s) in Fourier-Transform Infrared Spectroscopy (FTIR). The alkyl (CH_3-, CH_2-) functional group, which exists in almost all organic compounds, will show two or more distinct absorption peaks in the 2800-3000 cm^-1 range. Thus, if a given spectrum shows these peaks, we can safely say that the specimen contains the alkyl structure(s), which means organic compounds. Alkyl peaks can be used as a positive screening indicator without diving into the other IR spectra section. The overtone peaks, shapes, and intensity of carbonates in the 2800-3000cm^-1 range are different from the alkyl group. This paper uses FTIR, including synchrotron radiation sr-FTIR, to examine 63 fossil specimens spanning across a long geological time and different taphonomic conditions and 15 extant specimens and nine matrices for comparisons. Each specimen was FTIR scanned multiple times. A total of 107 spectra were selected from 525 scans. The results indicate that preservation of organic remains in body fossils is a common phenomenon, not a particular case.