Spectroscopic analysis and X-ray diffraction of trunk fossils from the Parnaíba Basin, Northeast Brazil

[Display omitted] •Brazilian trunk fossils were studied by analytical techniques.•The main crystalline phases of the fossils were identified.•The main fossilization process (silicification) could be inferred by the analytical measurements.•Some carbon amount was found and may be related to the kerog...

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Published in:Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2015-01, Vol.135, p.1052-1058
Main Authors: Alencar, Wemerson J., Santos, F. Eroni P., Cisneros, Juan C., da Silva, João H., Freire, Paulo T.C., Viana, Bartolomeu C.
Format: Article
Language:English
Subjects:
Parnaíba Basin
Silicification
Trunk fossils
Vibrational spectroscopies
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Summary:[Display omitted] •Brazilian trunk fossils were studied by analytical techniques.•The main crystalline phases of the fossils were identified.•The main fossilization process (silicification) could be inferred by the analytical measurements.•Some carbon amount was found and may be related to the kerogen presence. The Parnaiba Sedimentary Basin is of the Paleozoic age and is located in Northeast Brazil, covering the states of Piauí, Maranhão and Tocantins and a small part of Ceará and Pará. In this work we applied several chemical analytical techniques to characterize trunk fossils found in the Parnaíba Sedimentary Basin, collected from four different sites, and discuss their fossilization process. We performed a study of the trunk fossils through X-ray diffraction, energy dispersive spectroscopy, infrared and Raman spectroscopy. The analysis allow us to identify the different compositions which are present in the trunk fossils: kaolinite (Al2Si2O5(OH)4), hematite (Fe2O3) and quartz (SiO2). Based in these results we were able to identify that the main fossilization mechanism of the trunk fossil was silicification. Furthermore, through Raman spectroscopy, we have observed the presence of carbonaceous materials in the Permian fossils, as evidenced by the D and G Raman bands. The relative intensities and bandwidths of the D and G bands indicated that the carbon has a low crystallinity. Thus, most of trunk fossils analyzed were permineralized and not petrified, because there is the presence of carbon that characterizes the partial decomposition of the organic matter in some trunks.
ISSN:1386-1425
DOI:10.1016/j.saa.2014.08.005