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

Autor(es)

Monteiro, H. S. ; Vasconcelos, P. M. ; Farley, K. A. ; Mello, C. L. ; Conceicao, F. T.

• Tipo de documento: Artigo Científico
• Fonte: PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY; v. 601, p. 18-pg., 2022-07-09.

Resumo

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 Espirito 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 biologi-cally 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 Espirito Santo since the Pliocene. (AU)

• Processo FAPESP: 17/23577-2 - Geocronologia 40Ar/39Ar e (U-Th)/He em minerais supérgenos e evolução geomorfológica no sudeste do Estado de Goiás
• Beneficiário: Fabiano Tomazini da Conceição
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 18/00102-1 - A história de intemperismo, deposição e re-intemperismo dos sedimentos da Formação Barreiras nos estados do Rio de Janeiro e Espiríto Santo, Brasil
• Beneficiário: Hevelyn da Silva Monteiro
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado