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Taphonomy of lacustrine fish fossils of the Parnaiba Basin, northeastern Brazil: Spatial and causative relations of Konservat Lagerstatten in West Gondwana during Jurassic-Cretaceous

Texto completo
Cardoso, Alexandre Ribeiro [1, 2] ; Romero, Guilherme Raffaeli [1] ; Oses, Gabriel Ladeira [3] ; Rodrigues Nogueira, Afonso Cesar [1]
Número total de Autores: 4
Afiliação do(s) autor(es):
[1] Fed Univ Para Ufpa, Inst Geociences, Program Post Grad Geol & Geochem PPGG, Augusto Correa Ave 01, BR-66075110 Belem, Para - Brazil
[2] State Univ Campinas Unicamp, Inst Geosci, Dept Geol & Nat Resources, Carlos Gomes St 250, BR-13083870 Campinas, SP - Brazil
[3] Univ Fed Sao Carlos, Program Postgrad Ecol & Nat Resources PPGERN, Washington Luis SP 310, KM 235, BR-13565905 Sao Carlos, SP - Brazil
Número total de Afiliações: 3
Tipo de documento: Artigo Científico
Citações Web of Science: 0

Fossil bonanzas called Konservat Lagerstatten provide geological windows to the ecology of ancient life communities. These deposits often occur as cluster of fossil localities with similar geographic locations, geological ages and facies, as the fossils were generally preserved during special periods and large-scale events in Earth history within environments with exceptional taphonomic conditions. This work applied petrological and geochemical analyses to evaluate the taphonomic pathway of a Konservat Lagerstatten in the Muzinho Shale, Upper Jurassic-Lower Cretaceous of the Parnaiba Basin, northeastern Brazil. These lacustrine deposits include interbedded limestones and fossiliferous black shales deposited in anoxic, non-euxinic and saline environment. Black shales contain articulated skeletons of fish fossils, characterised by three-dimensional preservation of the skeletal tissue. The polytypical assemblage includes diverse ontogenetic stages and is concentrated in a specific stratigraphic level. Mass mortality was triggered by anoxia probably established by stratified water column, high C flux and thermocline demise. The specimens are encased in kerogen-bearing siliciclastic laminae and cementstone microfacies, both microbially-induced. The fossils were cemented by eodiagenetic poikilotopic calcite that filled the skeletal articulation, including bone trabeculae and voids originally filled by bone marrow. The short distance, similar fossil assemblages, ages and coincident palaeoenvironments suggest that Muzinho Shale (Parnaiba Basin) and Crato Formation (Araripe Basin) compose a cluster of exceptional preservation in West Gondwana. Lava flows and outgassing related to the Central Atlantic Magmatic Province (CAMP) resulted in the subaereal exposure of volcanic plains, acid rains and subsequent CO2 greenhouse crisis. CAMP-magmatism was especially voluminous in northern Brazilian basins, enhancing nutrient-rich waters and lacustrine eutrophication due to intensified chemical weathering in this area. Probably, other Konservat Lagerstatten remain unreported in West Gondwana. Despite similar causative events, the individual taphonomic pathways of Muzinho Shale and Crato Formation are very different, suggesting that in these cases local phenomena affected authigenesis and diagenesis. (AU)

Processo FAPESP: 17/21584-1 - Aspectos geobiológicos e paleoambientais de Corumbella werneri Hahn et al. (1982) e biota associada (Ediacarano, grupo Corumbá)
Beneficiário:Gabriel Ladeira Oses
Linha de fomento: Bolsas no Brasil - Doutorado
Processo FAPESP: 12/18936-0 - Aplicações de Espectroscopia Raman em paleobiologia e astrobiologia
Beneficiário:Setembrino Petri
Linha de fomento: Auxílio à Pesquisa - Regular