Deciphering the preservation of fossil insects: a case study from the Crato Member, Early Cretaceous of Brazil

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Oses, Gabriel Ladeira ; Petri, Setembrino ; Becker-Kerber, Bruno ; Romero, Guilherme Raffaeli ; Rizzutto, Marcia de Almeida ; Rodrigues, Fabio ; Galante, Douglas ; da Silva, Tiago Fiorini ; Curado, Jessica F. ; Rangel, Elidiane Cipriano ; Ribeiro, Rafael Parra ; Alves Forancelli Pacheco, Mirian Liza

• Tipo de documento: Artigo Científico
• Fonte: PeerJ; v. 4, DEC 21 2016.
• Citações Web of Science: 5

Resumo

Exceptionally well-preserved three-dimensional insects with fine details and even labile tissues are ubiquitous in the Crato Member Konservat Lagerstatte (northeastern Brazil). Here we investigate the preservational pathways which yielded such specimens. We employed high resolution techniques (EDXRF, SR-SXS, SEM, EDS, micro Raman, and PIXE) to understand their fossilisation on mineralogical and geochemical grounds. Pseudomorphs of framboidal pyrite, the dominant fossil microfabric, display size variation when comparing cuticle with inner areas or soft tissues, which we interpret as the result of the balance between ion diffusion rates and nucleation rates of pyrite through the originally decaying carcasses. Furthermore, the mineral fabrics are associated with structures that can be the remains of extracellular polymeric substances (EPS). Geochemical data also point to a concentration of Fe, Zn, and Cu in the fossils in comparison to the embedding rock. Therefore, we consider that biofilms of sulphate reducing bacteria (SRB) had a central role in insect decay and mineralisation. Therefore, we shed light on exceptional preservation of fossils by pyritisation in a Cretaceous limestone lacustrine palaeoenvironment. (AU)

• Processo FAPESP: 12/18936-0 - Aplicações de Espectroscopia Raman em paleobiologia e astrobiologia
• Beneficiário: Setembrino Petri
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 12/00202-0 - Investigações científicas nos museus paulistas
• Beneficiário: Márcia de Almeida Rizzutto
• Modalidade de apoio: Auxílio à Pesquisa - Regular