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

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...

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Bibliographic Details
Authors: Oses, Gabriel Ladeira, Petri, Setembrino, Becker-Kerber, Bruno, Romero, Guilherme Raffaeli, Rizzutto, Marcia de Almeida, Rodrigues, Fabio, Galante, Douglas, Silva, Tiago Fiorini da, Curado, Jessica F., Rangel, Elidiane Cipriano [UNESP], Ribeiro, Rafael Parra [UNESP], Alves Forancelli Pacheco, Mirian Liza
Format: article
Status:Published version
Publication Date:2016
Country:Brasil
Institution:Universidade Estadual Paulista (UNESP)
Repository:Repositório Institucional da UNESP
Language:English
OAI Identifier:oai:repositorio.unesp.br:11449/165416
Online Access:http://dx.doi.org/10.7717/peerj.2756
http://hdl.handle.net/11449/165416
Access Level:Open access
Keyword:Taphonomy
Paleometry
Early Cretaceous
Araripe Basin
Crato Member
Exceptional preservation
Insects
Pyrite
Description
Summary: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.

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