Tectonically-induced strontium isotope changes in ancient restricted seas: The case of the Ediacaran-Cambrian Bambui foreland basin system, east Brazil

Autor(es)

Guacaneme, Cristian ^[1] ; Babinski, Marly ^[1] ; Bedoya-Rueda, Carolina ^[1] ; Paula-Santos, Gustavo M. ^{[2, 3, 4]} ; Caetano-Filho, Sergio ^[1] ; Kuchenbecker, Matheus ^{[5, 6]} ; Reis, Humberto L. S. ^[7] ; Trindade, Ricardo I. F. ^[8]

Afiliação do(s) autor(es)

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

^[2] Univ Bremen, MARUM Ctr Marine Environm Sci, Leobener Str 8, D-28359 Bremen - Germany

^[3] Univ Bremen, Fac Geosci, Leobener Str 8, D-28359 Bremen - Germany

^[4] Univ Estadual Campinas, Inst Geociencias, Rua Carlos Gomes 255, BR-13083855 Campinas - Brazil

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

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

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

^[8] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226, BR-05508090 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: GONDWANA RESEARCH; v. 93, p. 275-290, MAY 2021.
• Citações Web of Science: 0

Resumo

The Bambui Group is a marine sedimentary record of an intracratonic foreland basin developed at the terminal Ediacaran and early Cambrian during the assembly of West Gondwana. Here we present a basin-scale highresolution Sr isotope stratigraphy for the basal Bambui Group, aiming to understand the spatial and temporal variations of the Sr-87/Sr-86 ratios and to explore the controls over the Sr isotope system in intracontinental marine environments. Assessment of the stratigraphic evolution of both Sr concentrations and Sr isotopes shows a major increase in Sr/Ca ratios (up to 0.004) and a decrease in the Sr-87/Sr-86 ratios from 0.7086 to 0.7076 in the high stand system tract of the basal 2nd-order sequence. These changes precede a large positive delta C-13 excursion typically found across the basin in themiddle Bambui Group. The high variability of both Sr-87/Sr-86 and Sr/Ca ratios was not caused by globally uniform changes in isotopic compositions of seawater, but rather likely reflect marine restriction and paleogeographic changes of the depositional environments at basin scale. This would result from the tectonic uplift of Neoproterozoic orogenic belts around the Sao Francisco craton, which generated an isolated foreland marine basin. Compared to the global ocean, such a smaller intracontinental reservoir would be more sensitive to the Sr isotope composition from the different rock sources. We suggest that changes on the balance between carbonate production and accommodation associated with tectonically-related flexural subsidence progressively modified the continental drainage patterns, sedimentary sources and the chemical weathering regimes, altering the strontium influxes and isotopic compositions of the seawater in the early Bambui basin cycle. Similar anomalies in the strontium isotope record are also recorded in coevalmarine basins acrossWest Gondwana and suggest that tectonicsmight have played an important role on seawater chemistry at the Neoproterozoic-Paleozoic transition. (C) 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. (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
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• 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
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 16/06114-6 - O Sistema Terra e a evolução da vida durante o Neoproterozoico
• Beneficiário: Ricardo Ivan Ferreira da Trindade
• Modalidade de apoio: Auxílio à Pesquisa - Temático