Physicochemical investigation of shrimp fossils from the Romualdo and Ipubi formations (Araripe Basin)

Abstract

The Ipubi and Romualdo Formations are Cretaceous units of the Araripe Basin (Santana Group). The first and most ancient was deposited in a lake environment, and some fossils were preserved in shales deposited under blackish conditions. The second was deposited in a marine environment, preserving a rich paleontological content in calcareous concretions. Considering that these two environments preserved their fossils under different processes, in this work we investigated the chemical composition of two fossilized specimens, one from each of the studied stratigraphic units, and compared them using vibrational spectroscopy techniques (Raman and IR), X-ray diffraction and large-field energy-dispersive X-ray spectroscopy (EDS) mappings. Calcite was observed as the dominant phase and carbon was observed in the fossils as a byproduct of the decomposition. The preservation of hydroxide calcium phosphate (Ca10(PO4)6(OH)2, hydroxyapatite) was observed in both fossils. In addition, it was observed that there was a smaller amount of pyrite (pyritization) in the Romualdo Formation sample than in the Ipubi one. Large-field EDS measurements showed the major presence of the chemical elements calcium, oxygen, iron, aluminum and fluoride in the Ipubi fossil, indicating a greater influence of inorganic processes in its fossilization. Our results also suggest that the Romualdo Formation fossilization process involved the substitution of the hydroxyl group by fluorine, providing durability to the fossils.

Chimera of fossil biomolecules found in Pleistocene fossil in tropical cave: Fossil biofilm characterization by micro Raman spectroscopy

“…Our observations are consistent with reports of organic signature on fossil samples [20][21][22][23] . Piga et al…”

“…The rst has a weak intensity at ~ 1681 cm -1 , and the second has moderated intensity at ~ 1717 cm -1 . These two peaks were attributed to peptide or C = O stretch and C-C respectively 22,24 . All spectra show the same pattern.…”

“…A couple studies on fossilization process with a diverse fossil's age and environmental conditions using Raman spectroscopy report the presence of a several bands between 1200 to 1800 cm − 1 related to organic compounds 18,[20][21][22][23] . Raman spectroscopy is a non-destructive technique that relies on the inelastic scattering of light.…”

Petrological Meaning of Ethnostratigraphic Units: Laminated Limestone of the Crato Formation, Araripe Basin, NE Brazil

“…The laminites of the Nova Olinda Member are attributed to a lacustrine system deposited under microbial influence (Catto et al, 2016;Warren et al 2017). The excellent preservation of Crato fossils have been made it known worldwide as a Fossil Konservat-Lagerstätte (Wilby & Martill, 1992;Kellner, 1996;Pinheiro et al, 2012;Barros et al, 2019;Bezerra et al, 2020).…”

O Estudo de Camarões Fósseis no Brasil

“…Neste caso, detalhes anatômicos mais delicados normalmente são perdidos ou ficam mal preservados, dificultando a identificação dos táxons (Garassino & Teruzzi 1996). Por isso, nos locais onde há registro fossilífero de camarões, condições muito raras e especiais de fossilização no momento da sedimentação, como anoxia e fosfato amorfo para substituir a matéria orgânica, foram atuantes e podem acrescentar dados esclarecedores sobre a paleoecologia desses animais (Barros et al 2019;Oliveira et al 2015).…”