A large epeiric methanogenic Bambuí sea in the core of Gondwana supercontinent?  

作　　者：Sergio Caetano-Filho Pierre Sansjofre Magali Ader Gustavo M.Paula-Santos Cristian Guacaneme Marly Babinski Carolina Bedoya-Rueda Matheus Kuchenbecker Humberto L.S.Reis Ricardo I.F.Trindade 

机构地区：[1]Universidade de Sao Paulo,Instituto de Geociencias,Rua do Lago,562-Sao Paulo,05508-080,Brazil [2]MNHN,Sorbonne Universite,CNRS UMR 7590,Institut de Mineralogie,de Physique des Materiaux et de Cosmochimie,75005,Paris,France [3]Universite de Paris,Institut de Physique du Globe de Paris,CNRS,F-75005,Paris,France [4]Universidade Estadual de Campinas,Instituto de Geociencias,Rua Carlos Gomes,250-Campinas,13083-855,Brazil [5]Universidade Federal dos Vales do Jequitinhonha e Mucuri,Instituto de Ciencia e Tecnologia,Laboratorio de Estudos Tectonicos,Rodovia MGT 367,Km 583-Diamantina,39100-000,Brazil [6]Universidade Federal de Ouro Preto,Departamento de Geologia-Escola de Minas,Laboratiorio de Modelagem Tectonica,Campus Morro do Cruzeiro-Ouro Preto,35400-000,Brazil [7]Universidade de Sao Paulo,Instituto de Astronomia,Geofísica e Ciencias Atmosfericas,Rua do Matao,1226-Sao Paulo,05508-090,Brazil

出　　处：《Geoscience Frontiers》2021年第1期203-218,共16页地学前缘（英文版）

基　　金：funded by the S~ao Paulo Research Foundation(FAPESP)thematic project grant#2016/06114-6;Brazilian Research Council project grant#400764/2016-4。

摘　　要：Carbon isotope compositions of both sedimentary carbonate and organic matter can be used as key proxies of the global carbon cycle and of its evolution through time,as long as they are acquired from waters where the dissolved inorganic carbon(DIC)is in isotope equilibrium with the atmospheric CO2.However,in shallow water platforms and epeiric settings,the influence of local to regional parameters on carbon cycling may lead to DIG isotope variations unrelated to the global carbon cycle.This may be especially true for the terminal Neoproterozoic,when Gondwana assembly isolated waters masses from the global ocean,and extreme positive and negative carbon isotope excursions are recorded,potentially decoupled from global signals.To improve our understanding on the type of information recorded by these excursions,we investigate the pairedδ^13Ccarb andδ^13Corg evolution for an increasingly restricted late Ediacaran-Cambrian foreland system in the West Gondwana interior:the basal Bambui Group.This succession represents a 1~(st)-order sedimentary sequence and records two majorδ^13Ccarb excursions in its two lowermost lower-rank sequences.The basal cap carbonate interval at the base of the first sequence,deposited when the basin was connected to the ocean,hosts antithetical negative and positive excursions forδ^13Ccarb andδ^13Corg,respectively,resulting inΔ^13C values lower than 25‰.From the top of the basal sequence upwards,an extremely positiveδ^13Ccarb excursion is coupled toδ^13Corg,reaching values of+14‰and-14‰,respectively.This positive excursion represents a remarkable basin-wide carbon isotope feature of the Bambui Group that occurs with only minor changes inΔ^13C values,suggesting change in the DIC isotope composition.We argue that this regional isotopic excursion is related to a disconnection between the intrabasinal and the global carbon cycles.This extreme carbon isotope excursion may have been a product of a disequilibria between the basin DIC and atmospheric CO2 induced by an active methanogenes

关 键 词：METHANOGENESIS EDIACARAN CAMBRIAN Carbon isotopes Sao Francisco Basin Bambui Group 

分 类 号：P59[天文地球—地球化学] P532[天文地球—地质学]