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The sulfur isotopic consequence of seawater sulfate distillation preserved in the Neoproterozoic Sete Lagoas post-glacial carbonate, eastern Brazil

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Author(s):
Okubo, Juliana ; Kaufman, Alan J. ; Warren, Lucas, V ; Evans, Michael N. ; Marroquin, Selva ; Varni, Michael A. ; Misi, Aroldo ; Bahniuk, Anelize M. ; Xiao, Shuhai
Total Authors: 9
Document type: Journal article
Source: JOURNAL OF THE GEOLOGICAL SOCIETY; v. N/A, p. 23-pg., 2022-02-28.
Abstract

Since the report of tubular structures interpreted as Cloudina from the Neoproterozoic Sete Lagoas Formation (SLF) in the Bambui basin of eastern Brazil, this stratigraphic unit has become a focus of numerous geochemical, palaeomagnetic, geochronological and sequence stratigraphic studies. Geochemical data from the SLF have been used to infer palaeoenvironmental conditions in the Bambui basin and to study the C-13 enrichment reported in this and overlying units. To further address depositional environments of the SLF, we present high-resolution delta C-13 and delta S-34 data from the SLF in the Januaria and Sete Lagoas regions. We report the presence of superheavy pyrite with delta S-34 value greater than carbonate-associated sulfate (CAS) and observe a decrease in CAS abundance coupled with a delta S-34 change from c. +20 to near +50 parts per thousand. These data are interpreted as evidence for distillation of sulfate through CAS and pyrite removal from the epeiric Bambui basin. These changes are qualitatively consistent with quantitative simulations of isotopic distillation over a period of c. 10 myr of a seawater sulfate reservoir comparable with modern concentration. Considering that Neoproterozoic seawater sulfate concentrations were probably much lower than in modern oceans, the distillation time interval was probably much shorter than 10 myr. (AU)

FAPESP's process: 17/19023-1 - Bulk sulfur isotopic data and proxy minerals from the Sete Lagoas Formation (Bambuí Group)
Grantee:Juliana Okubo
Support Opportunities: Scholarships abroad - Research Internship - Doctorate
FAPESP's process: 18/26230-6 - 10 million years that changed the planet: paleoenvironmental context of the evolution of the first animals with skeleton in the Terminal Ediacaran Period
Grantee:Lucas Verissimo Warren
Support Opportunities: Regular Research Grants
FAPESP's process: 15/07391-0 - Sedimentary evolution of the Sete Lagoas formation (Bambuí group, northern Minas Gerais State) in the context of the upper Ediacaran sedimentary basins
Grantee:Juliana Okubo
Support Opportunities: Scholarships in Brazil - Doctorate