Article,
Spectroscopic analysis and X-ray diffraction of trunk fossils from the Parnaiba Basin, Northeast Brazil
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, (2015)
DOI: 10.1016/j.saa.2014.08.005
Abstract
The Parnaiba Sedimentary Basin is of the Paleozoic age and is located in
Northeast Brazil, covering the states of Piaui, Maranhao and Tocantins
and a small part of Ceara and Para. In this work we applied several
chemical analytical techniques to characterize trunk fossils found in
the Parnaiba 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. (C) 2014 Elsevier B.V. All rights reserved.
