Abstract The Crato Formation Lagerstatte of NE Brazil is well known for the exceptional preservation of its fossil assemblage. A wide variety of plants and animals are preserved with a high degree of fidelity, revealing structures of labile tissues at the micron scale, or even smaller. Chemical analyses and descriptions of replacement fabrics observed in insect fossils from the formation are here re-evaluated. Two mineral phases with three distinct fabrics are identified replacing soft tissues: 1) nano-crystalline high-fidelity pyrite replacements of insect epicuticle (pseudomorphed in goethite); 2) pyrite framboids and pseudoframboids obliterating original insect morphology (pseudomorphed in goethite); 3) globular replacements and encrustations of internal labile tissues in calcium phosphate. A revised taphonomic and geochemical model is presented that accounts for both the high fidelity of preservation and the micro-fabrics observed. In addition, we consider aspects of the depositional environment, including substrate consistency, water depth and light penetration. We conclude that the water depth was likely in excess of 50 m, but within the photic zone, and the sediment was bound by stratified microbial communities.

中文翻译：

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巴西克拉托组（下白垩纪）昆虫保存地球化学模型

摘要 巴西东北部拉格施塔特的克拉托地层以其化石组合的特殊保存而闻名。各种各样的植物和动物被高度保真保存，揭示了微米级甚至更小的不稳定组织的结构。此处重新评估了在地层昆虫化石中观察到的替代织物的化学分析和描述。鉴定出具有三种不同织物的两种矿物相替代软组织：1) 纳米晶高保真黄铁矿替代昆虫上表皮（针铁矿中的假晶）；2) 黄铁矿 framboids 和pseudoframboids 消除了原始昆虫形态（针铁矿中的伪形）；3) 磷酸钙中内部不稳定组织的球状置换和结壳。提出了一个修订的埋藏学和地球化学模型，该模型解释了保存的高保真度和观察到的微结构。此外，我们还考虑了沉积环境的各个方面，包括基材的一致性、水深和光线穿透。我们得出结论，水深可能超过 50 m，但在透光区内，沉积物被分层微生物群落束缚。