| Full text | |
| Author(s): |
Caetano-Filho, Sergio
[1]
;
Sansjofre, Pierre
[2]
;
Ader, Magali
[3]
;
Paula-Santos, Gustavo M.
[4]
;
Guacaneme, Cristian
[1]
;
Babinski, Marly
[1]
;
Bedoya-Rueda, Carolina
[1]
;
Kuchenbecker, Matheus
[5]
;
Reis, Humberto L. S.
[6]
;
Trindade, Ricardo I. F.
[7]
Total Authors: 10
|
| Affiliation: | [1] Univ Sao Paulo, Inst Geociencias, Rua Lago 562, BR-05508080 Sao Paulo - Brazil
[2] Sorbonne Univ, MNHN, CNRS, Inst Mineral Phys Mat & Cosmochim, UMR 7590, F-75005 Paris - France
[3] Univ Paris, Inst Phys Globe Paris, CNRS, F-75005 Paris - France
[4] Univ Estadual Campinas, Inst Geociencias, Rua Carlos Gomes 250, BR-13083855 Campinas - Brazil
[5] Univ Fed Vales Jequitinhonha & Mucuri, Inst Ciencia & Tecnol, Lab Estudos Tecton, Rodovia MGT 367, Km 583, BR-39100000 Diamantina - Brazil
[6] Univ Fed Ouro Preto, Escola Minas, Lab Modelagem Tecton, Dept Geol, Campus Morro Cruzeiro, BR-35400000 Ouro Preto - Brazil
[7] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226, BR-05508090 Sao Paulo - Brazil
Total Affiliations: 7
|
| Document type: | Journal article |
| Source: | GEOSCIENCE FRONTIERS; v. 12, n. 1, p. 203-218, JAN 2021. |
| Web of Science Citations: | 3 |
| Abstract | |
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 DIC 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 paired delta C-13(carb) and delta C-13(org) evolution for an increasingly restricted late Ediacaran-Cambrian foreland system in the West Gondwana interior: the basal Barn-bill Group. This succession represents a 1st-order sedimentary sequence and records two major delta C-13(carb) 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 for delta C-13(carb) and delta C-13(org), respectively, resulting in Delta C-13 values lower than 25%o. From the top of the basal sequence upwards, an extremely positive delta C-13(carb) excursion is coupled to delta C-13(org), reaching values of +14 parts per thousand and -14 parts per thousand, respectively. This positive excursion represents a remarkable basin-wide carbon isotope feature of the Barn-bill Group that occurs with only minor changes in Delta C-1(3) 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 methanogenesis, favored by the basin restriction. The drawdown of sulfate reservoir by microbial sulfate reduction in a poorly ventilated and dominantly anoxic basin would have triggered methanogenesis and ultimately methane escape to the atmosphere, resulting in a(13)C-enriched DIC influenced by methanogenic CO2. Isolated basins in the interior of the Gondwana supercontinent may have represented a significant source of methane inputs to the atmosphere, potentially affecting both the global carbon cycle and the climate. (AU) | |
| FAPESP's process: | 16/11496-5 - Sulfur and Carbon biogeochemical cycles in the Ediacaran and their record in Brazilian sedimentary successions |
| Grantee: | Sergio Caetano Filho |
| Support Opportunities: | Scholarships in Brazil - Doctorate |
| FAPESP's process: | 16/06114-6 - The Neoproterozoic Earth System and the rise of biological complexity |
| Grantee: | Ricardo Ivan Ferreira da Trindade |
| Support Opportunities: | Research Projects - Thematic Grants |
| FAPESP's process: | 17/00399-1 - Chemical weathering and nutrient input into late Ediacaran ocean and their relationship to life diversification |
| Grantee: | Gustavo Macedo de Paula Santos |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |