Article,
Raman and infrared spectroscopy investigation of the root fossil (rhizoliths) from the Carboniferous period, Piaui Formation, Parnaiba Sedimentary Basin, Northeast Brazil
VIBRATIONAL SPECTROSCOPY, (2019)
DOI: 10.1016/j.vibspec.2018.11.007
Abstract
The Upper Carboniferous Sandstone at Sao Goncalo do Gurgueia,
Northeastern of the Brazil, is notable for its large number of preserved
root-like structures. Among these structures it is found rhizoliths,
fossils of a root system, containing the original cellular material and
mineral impregnation and/or mineral replacement. Furthermore, the fossil
can present characteristics of preserved anatomical features of the
root. The present study shows the physico-chemical characterization
results of the mineralized rhizolith (PIC 073.15) from Piaui Formation.
This fossil was investigated through X-ray diffraction, X-ray
fluorescence, Fourier transform infrared and Raman spectroscopy. The
analysis showed that the SiO2 is the main component found in the sample,
as demonstrated by the presence of quartz and clay minerals. However,
there is also the presence of iron oxides (goethite and hematite) whose
content increases from the inner to the outer part. The iron
accumulation in PIC 073.15 suggests alternated oxidizing and reduction
cycles, indicating humidity's variation of the Piaui Formation
environment. The measurements suggest that the first mineralization of
the rhizolith occurred through silification process followed by
ferruginous precipitations (pos diagenetic process).
