The role of microbial mats in the exquisite preservation of Aptian insect fossils from the Crato Lagerstätte, Brazil

Dias, Jaime Joaquim; Carvalho, Ismar de Souza

doi:10.1016/j.cretres.2021.105068

Cited by 15 publications

(10 citation statements)

References 66 publications

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“…The formation of pyrite replacements and their direct involvement in the replication of insect morphology are intrinsically associated with the time the fossils spent in the bacterial sulfate reduction zone of the sediment (Schiffbauer et al 2014). The taphonomic pathways of pyritized insects during the early diagenesis of the Crato Formation have been well documented in previous studies (Barling et al 2015, 2020; Osés et al 2016; Bezerra et al 2020; Dias & Carvalho, 2020, 2021). Nonetheless, the scattered distribution of the aggregate particles and the variety of their arrangements indicates a complex oxidation process with several probable stages.…”

Section: Discussionsupporting

confidence: 65%

“…The presence of microcracks in the insect cuticles of the Crato Formation has been frequently reported (Delgado et al 2014; Barling et al 2015, 2020; Osés et al 2016; Bezerra et al 2020, 2021; Dias & Carvalho, 2020, 2021; Prado et al 2021). Crato insects with iron-oxide overgrowths show intricate zones of microcracks associated with compact cuticular surfaces without individualized crystals (Fig.…”

Section: Resultsmentioning

confidence: 92%

“…A consequence of this exceptional preservation is that the majority of studies on the Crato palaeoentomofauna are focused on taxonomic and evolutionary issues. However, an increasing number of investigations have analysed the general insect taphonomy, with a focus on early-diagenetic issues (Delgado et al 2014; Barling et al 2015, 2020, 2021; Osés et al 2016; Bezerra et al 2018, 2020, 2021; Dias & Carvalho, 2020, 2021; Prado et al 2021). These authors briefly mentioned the effect of weathering.…”

Section: Introductionmentioning

confidence: 99%

“…These authors briefly mentioned the effect of weathering. The high degree of fidelity of the Crato insects was achieved during early-mesodiagenesis under reducing conditions mediated by microbial mats (Osés et al 2016; Varejão et al 2019; Dias & Carvalho, 2021). After final burial, ions and sulfate-reducing bacteria favour the formation of framboidal pyrite, which replaces cuticle and labile tissues and prevents the total collapse of the carcass.…”

Section: Introductionmentioning

confidence: 99%

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Effects of chemical weathering on the exceptional preservation of mineralized insects from the Crato Formation, Cretaceous of Brazil: implications for late diagenesis of fine-grained Lagerstätten deposits

Bezerra

Silva²,

Agressot³

et al. 2023

Geol. Mag.

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Many studies have improved our understanding of the mode of preservation at the Crato fossil Lagerstätte. The high degree of preservation of the Crato mineralized insects is thought to be a consequence of the diffusion of ions through carcasses and envelopment by bacteria that, in turn, created microenvironmental conditions that led to mineralization, mainly pyritization. Pyritized insects have been oxidized by in situ weathering to more stable oxide/hydroxy minerals during Quaternary time. This transformation is essential to maintain the palaeontological information acquired during microbially induced pyritization in an oxidizing atmosphere. However, intense weathering can diminish or obscure the morphological fidelity, and little attention has been paid to the post-diagenetic processes experienced by these fossils. Here, we aim to determine the degree of alteration undergone by Crato pyritized insects using the following combination of analytical tools: scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared and Raman spectroscopy. Our results show that well-preserved insects are preferentially replaced by haematite and poorly preserved fossils are replaced by goethite. In addition, we recorded three types of post-diagenetic alteration: insects with iron-oxide overgrowths; insects associated with black coatings, sometimes with the formation of dendrites; and insects preserved as an impression, where only the outline of the body remains. All of these alterations have the potential to distort or tarnish palaeontological information. Here, we measured the effects of such telodiagenetic alterations at macro and micro scales. Therefore, this taphonomic approach has wide applicability wherever fine-grained deposits bearing mineralized insects are found.

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Section: Discussionsupporting

confidence: 65%

Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of chemical weathering on the exceptional preservation of mineralized insects from the Crato Formation, Cretaceous of Brazil: implications for late diagenesis of fine-grained Lagerstätten deposits

Bezerra

Silva²,

Agressot³

et al. 2023

Geol. Mag.

View full text Add to dashboard Cite

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“…The age of the Crato Formation is considered to be upper Aptian (early Cretaceous) (Pons et al 1991;Heimhofer and Hochuli 2010;Varejão et al 2021). Dias and Carvalho (2022) recently demonstrated the role of the microbial mats in the preservation of the insects in the Crato Formation.…”

Section: Methodsmentioning

confidence: 99%

The third aeschnidiid dragonfly genus and species from the Lower Cretaceous Crato Formation (Odonata, Anisoptera)

2022

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Cratoaeschnidium martinsnetoi gen. et sp. nov., third genus and species of Aeschnidiidae from the Crato Formation (Brazil), is described and illustrated based on one well-preserved forewing.It can be differentiated from the other genera in the family, inter alia, because of its discoidal triangle very narrow with only one row of cells; three rows of cells between Mspl and MAa, and between Rspl and IR2; one row of cells between CuAa and MP in basal part; three rows of cells between RP3/4 and MAa. This new genus and species confirms that much can be expected in regard to discovering the Odonata in the Crato Formation.

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The Cretaceous Araripe Basin Dinosaur Tracks and Their Paleoenvironmental Meaning

de Souza Carvalho,

Leonardi,

Dias

2024

Dinosaur Tracks of Mesozoic Basins in Brazil

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The role of microbial mats in the exquisite preservation of Aptian insect fossils from the Crato Lagerstätte, Brazil

Cited by 15 publications

References 66 publications

Effects of chemical weathering on the exceptional preservation of mineralized insects from the Crato Formation, Cretaceous of Brazil: implications for late diagenesis of fine-grained Lagerstätten deposits

Effects of chemical weathering on the exceptional preservation of mineralized insects from the Crato Formation, Cretaceous of Brazil: implications for late diagenesis of fine-grained Lagerstätten deposits

The third aeschnidiid dragonfly genus and species from the Lower Cretaceous Crato Formation (Odonata, Anisoptera)

The Cretaceous Araripe Basin Dinosaur Tracks and Their Paleoenvironmental Meaning

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