Vibrational spectroscopy and X‐ray diffraction applied to the study of Cretaceous fish fossils from Araripe Basin, Northeast of Brazil

Abstract

In this work, we investigate fossils of the fish coelacanth belonging to the Cretaceous Period from two different formations belonging to Araripe Basin (Brejo Santo and Romualdo Formations), in Northeast of Brazil, through Raman and infrared spectroscopy and X‐ray diffraction. The coelacanth processes of fossilization have occurred of different manners as a consequence of the different environment surrounding the fossils. The results obtained by different techniques showed that the matrix found in the Romualdo Formation is composed of calcite and quartz, whereas the matrix found in the Brejo Santo Formation is comprised of calcite, quartz, and albite. On the other hand, the presence of (PO4)−3 units in the fossils of coelacanth was proved clearly from the Raman spectroscopic analysis, supporting the results furnished by X‐ray diffraction measurements. The fossil from Brejo Santo Formation is well preserved, presenting mainly the hydroxyapatite and the fossil from the Romualdo Formation that is partially substituted by calcite, indicating the occurrence of a substitution process. Copyright © 2014 John Wiley & Sons, Ltd.

Spectroscopic Characterization of Eoholocene Bones Found in a Cave in Northeast Brazil

“…Specifically, the bands centered at 467 and 557 cm −1 are associated with antisymmetric deformation of PO 3− 4 ion, while the bands around 1020 cm −1 are related to the antisymmetric stretching of PO 3− 4 . Furthermore, calcite bands at 875 cm −1 correspond to symmetric deformations of CO 2− 3 , and bands at 1419 and 1460 cm −1 due to symmetric stretchings of CO 2− 3 were observed [2][3][4]. IR results were synergistic with the XRF and XRD analysis, suggesting together the presences of crystalline calcium, carbonate, and phosphate phases.…”

“…e IR spectra ( Figures 5 and 6) showed characteristic bands of hydroxyapatite [2][3][4]. Specifically, the bands centered at 467 and 557 cm −1 are associated with antisymmetric deformation of PO 3− 4 ion, while the bands around 1020 cm −1 are related to the antisymmetric stretching of PO 3− 4 .…”

“…Geochemical investigations and physical characterizations were performed to determine the composition of a fossil provide both taphonomic and ecologic data. Mineralogical composition of fossils can be adequately studied using physicochemical and mineralogical techniques such as X-ray fluorescence, X-ray diffraction, and infrared spectroscopy [2][3][4].…”

Recent advances in linear and non‐linear Raman spectroscopy. Part IX

“…Freire and co‐workers used IR and Raman spectroscopy and XRD to the study of Cretaceous fish fossils from Araripe Basin of Northeast of Brazil. The results obtained by these techniques showed that the matrix found in the Romualdo Formation is composed of calcite and quartz, whereas the matrix found in the Brejo Santo Formation is comprised of calcite, quartz and albite . Jersek and Kamar used Raman microspectroscopy to identify gemstones from a chalice made in 1732 containing 456 embedded gemstones, one of the most richly decorated chalices in Slovenia.…”

Applications of Raman spectroscopy in art and archaeology

“…Coelacanth fossils from the Romualdo and Brejo Santo Geological formations in Brazil were studied by Freire et al . By utilisation of Raman, IR and XRD measurements, it was found that the coelacanth processes of fossilisation occurred in different manners depending on the environmental conditions the fossils were exposed to.…”