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Published September 1, 2022 | Supplemental Material
Journal Article Open

Long-term vegetation-induced goethite and hematite dissolution-reprecipitation along the Brazilian Atlantic margin

Abstract

Distinctive sediments containing mostly quartz, kaolinite, and both detrital and authigenic hematite and goethite blanket ~5000 km of the Atlantic coast of Brazil from Rio de Janeiro all the way to the mouth of the Amazon River. The sediments represent a significant period of continental erosion followed by renewed weathering. Here we present (U-Th)/He ages of detrital and authigenic goethites and hematites collected from six weathering profiles in Espírito Santo, southeastern Brazil. Detrital goethites are as old as ~26 Ma and the oldest authigenic hematite is ~20 Ma, suggesting that erosion, transportation, and deposition of the sediments occurred in the 26–20 Ma period. Intense post-depositional weathering and ferruginization of the sediments suggest that precipitation-dissolution-reprecipitation of iron oxides and oxyhydroxides were strongly controlled by biologically driven weathering reactions. (U-Th)/He geochronology of 158 grains of authigenic goethite and hematite precipitated during biologically mediated water-rock interaction yield 137 results in the 5–0.6 Ma period, suggesting that tropical climate and abundant vegetation dominated the coast of Espírito Santo since the Pliocene.

Additional Information

© 2022 Elsevier. Received 23 November 2021, Revised 27 June 2022, Accepted 29 June 2022, Available online 2 July 2022. This project was funded by the Australian Research Council (ARC Discovery DP160104988) grant to Paulo Vasconcelos and Kenneth Farley, National Science Foundation grant to KF, the São Paulo Research Foundation grant (Process n°: 2017/23577-2) to Fabiano Conceição, and the São Paulo Research Foundation scholarship (Process n°: 2018/00102-1) to Hevelyn Monteiro. We thank Cécile Gautheron and an anonymous reviewer for their constructive comments and suggestions. CRediT author statement. Hevelyn Monteiro: Conceptualization, Methodology, Investigation, Visualization, Writing – Original Draft; Paulo Vasconcelos: Conceptualization, Methodology, Funding acquisition, Resources, Writing – Review and Editing; Kenneth Farley: Methodology, Funding acquisition, Resources, Writing – Review and Editing; Claudio Mello: Resources, Writing – Review and Editing; Fabiano Conceição: Funding acquisition Resources, Writing – Review and Editing. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Additional details

Created:
August 22, 2023
Modified:
October 24, 2023