Sequence stratigraphy and chemostratigraphy of an Ediacaran-Cambrian foreland-related carbonate ramp (Bambui Group, Brazil)

Autor(es):Mostrar menos -

Caetano-Filho, Sergio ^[1] ; Paula-Santos, Gustavo M. ^[2] ; Guacaneme, Cristian ^[1] ; Babinski, Marly ^[1] ; Bedoya-Rueda, Carolina ^[1] ; Peloso, Marilia ^[1] ; Amorim, Kamilla ^{[3, 4]} ; Afonso, Jhon ^[3] ; Kuchenbecker, Matheus ^{[5, 6]} ; Reis, Humberto L. S. ^[7] ; Trindade, Ricardo I. F. ^[3]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508080 Sao Paulo - Brazil

^[2] Univ Estadual Campinas, Inst Geociencias, Rua Carlos Gomes, BR-13083855 Campinas, SP - Brazil

^[3] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226, BR-05508090 Sao Paulo - Brazil

^[4] Univ Fed Mato Grosso, Fac Geociencias, Av Fernando Correa da Costa 2367, BR-78060900 Cuiaba - Brazil

^[5] Univ Fed Vales Jequitinhonha & Mucuri, Inst Ciencia & Tecnol, Rodovia MGT 367, Km 583, BR-39100000 Diamantina - Brazil

^[6] Univ Fed Minas Gerais, Ctr Pesquisas Prof Manoel Teixeira da Costa, Av Antonio Carlos 6627, BR-31270901 Belo Horizonte, MG - Brazil

^[7] Univ Fed Ouro Preto, Dept Geol Escola Minas, Lab Modelagem Tecton LabMod, Campus Morro do Cruzeiro, BR-35400000 Ouro Preto, MG - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Precambrian Research; v. 331, SEP 1 2019.
• Citações Web of Science: 2

Resumo

In the terminal Neoproterozoic, drastic climate changes associated with biological innovations are coupled to isotope and elemental geochemical anomalies. However, lateral variability and local depositional controls may affect global geochemical signals, which can only be tracked through a proper stratigraphic/paleogeographic assessment. Here, we investigate the sequence stratigraphy and chemostratigraphy of the basal units of the Bambui Group, central-east Brazil. This stratigraphic unit records a foreland basin system developed during the Ediacaran-Cambrian West Gondwana assembly and represents a 1st-order sequence, in which the two lowermost 2nd-order sequences record major geochemical disturbances. The first 2nd-order sequence started with the deposition of a transgresive systems tract, possibly in a postglacial scenario, which accompanies a negative-topositive delta C-13(carb) excursion. The early highstand systems tract represents the establishment of a marine carbonate ramp throughout the basin. In terms of chemostratigraphy, it corresponds to a delta C-13(carb) plateau close to 0 parts per thousand and Sr/Ca ratios around 0.001. The late highstand stage coincides with a remarkable increase in Sr content and Sr/Ca ratios at basinal scale. Occurrences of the CloudMa sp. late Ediacaran index fossil were reported in this stage. An erosional unconformity associated with a dolomitic interval, locally including subaerial exposure features, marks the top of the first 2nd-order sequence. This sequence boundary heralds an abrupt increase in delta C-13(carb) values, up to + 14 parts per thousand. These extremely high delta C-13(carb) values and high Sr/Ca ratios persist throughout the overlying sequence, as a result of progressive and enhanced restriction of the foreland basin system. Basin restriction at this stage has implications for the paleontological and chemostratigraphic record of epicontinental basins of the West Gondwana in the terminal Ediacaran. Late Ediacaran Sr-rich intervals in these basins show unusually nonradiogenic Sr-87/Sr-86 ratios, which may represent local depositional controls and deviations from the modern oceanographic models. Physiographic barriers and stressful conditions likely represented extreme environments for metazoan colonization. (AU)

• Processo FAPESP: 16/11496-5 - Ciclos biogeoquímicos de enxofre e carbono no Ediacarano e seu registro em sucessões sedimentares brasileiras
• Beneficiário: Sergio Caetano Filho
• Linha de fomento: Bolsas no Brasil - Doutorado
• Processo FAPESP: 16/06114-6 - O Sistema Terra e a evolução da vida durante o Neoproterozoico
• Beneficiário: Ricardo Ivan Ferreira da Trindade
• Linha de fomento: Auxílio à Pesquisa - Temático
• Processo FAPESP: 17/00399-1 - Intemperismo químico e fluxo de nutrientes para o oceano no Ediacarano superior e suas relações com a diversificação da vida
• Beneficiário: Gustavo Macedo de Paula Santos
• Linha de fomento: Bolsas no Brasil - Pós-Doutorado