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

PeerJ

article

Gabriel Ladeira Osés¹  Setembrino Petri²  Bruno Becker-Kerber³  Guilherme Raffaeli Romero⁴  Marcia de Almeida Rizzutto⁵  Fabio Rodrigues⁶  Douglas Galante⁷  Tiago Fiorini da Silva⁵  Jessica F. Curado⁸  Elidiane Cipriano Rangel⁹  Rafael Parra Ribeiro⁹  Mírian Liza Alves Forancelli Pacheco^1,10 

[1] Programa de Pós-graduação em Geoquímica e Geotectônica, Institute of Geosciences, Universidade de São Paulo;Institute of Geosciences, Universidade de São Paulo;Programa de Pós-Graduação em Ecologia e Recursos Naturais, Universidade Federal de São Carlos;Institute of Geosciences, Universidade Federal do Pará;Institute of Physics, Universidade de São Paulo;Department of Fundamental Chemistry/Institute of Chemistry, Universidade de São Paulo;Brazilian Synchrotron Light Laboratory;Department of Physics, Centro Universitário FEI;Laboratory of Technological Plasmas, Universidade Estadual Paulista;Department of Biology, Universidade Federal de São Carlos

关键词: Taphonomy;    Paleometry;    Early Cretaceous;    Araripe Basin;    Crato Member;    Exceptional preservation;    Insects;    Pyrite;   

DOI  :  10.7717/peerj.2756

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Exceptionally well-preserved three-dimensional insects with fine details and even labile tissues are ubiquitous in the Crato Member Konservat Lagerstätte (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.

【 授权许可】

CC BY