Diagenetic Fate of Biogenic Soft and Hard Magnetite in Chemically Stratified Sedimentary Environments of Mamangua Ria, Brazil

Autor(es):Mostrar menos -

Rodelli, D. ^[1] ; Jovane, L. ^[1] ; Giorgioni, M. ^{[1, 2]} ; Rego, E. S. ^{[1, 3]} ; Cornaggia, F. ^[1] ; Benites, M. ^[1] ; Cedraz, P. ^[1] ; Berbel, G. B. B. ^[1] ; Braga, E. S. ^[1] ; Ustra, A. ^[4] ; Abreu, F. ^[5] ; Roberts, A. P. ^[6]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Oceanog, Sao Paulo - Brazil

^[2] Univ Brasilia, Inst Geociencias, Brasilia, DF - Brazil

^[3] Univ Sao Paulo, Inst Geociencias, Sao Paulo - Brazil

^[4] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Sao Paulo - Brazil

^[5] Univ Fed Rio de Janeiro, Inst Microbiol Paulo Goes, Rio De Janeiro - Brazil

^[6] Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT - Australia

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH; v. 124, n. 3, p. 2313-2330, MAR 2019.
• Citações Web of Science: 1

Resumo

Magnetotactic bacteria (MTB) synthesize magnetite and greigite crystals under low oxygen conditions in the water column or uppermost sediment (greigite-producing bacteria are found below the oxic-anoxic transition). Dissolved iron and oxygen contents in local environments are known to be limiting factors for the production and preservation of biogenic magnetite. Understanding the processes that link MTB to their living environments is fundamental to reconstructing past chemical variations in the water column and sediment, and for using the magnetic properties of biogenic magnetite as environmental proxy indicators. Previous studies have suggested that the frequently identified biogenic soft (BS) and biogenic hard (BH) magnetite types are associated with equant and more elongated morphologies, respectively, and that their abundance varies in accordance with sedimentary oxygen content, where MTB that produce the BH component live in less oxygenated environments. We test this hypothesis in a high-resolution integrated environmental magnetic and geochemical study of surface sediments from Mamangua Ria, SE Brazil. Based on magnetic and pore water profiles, we demonstrate that both the BS and BH components occur within microaerobic environments and that as sediment oxygen content decreases with depth, the BS component disappears before the BH component. With continued burial into the sulfidic diagenetic zone, both components undergo progressive dissolution, but the BH component is more resistant to dissolution than the BS component. Our observations confirm previous inferences about the relative stability of these phases and provide a firmer basis for use of these two types of biogenic magnetite as paleoenvironmental proxies. (AU)

• Processo FAPESP: 11/22018-3 - Avaliação da produtividade primária marinha através do estudo das bactérias magnetotáticas em sedimentos
• Beneficiário: Luigi Jovane
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Jovens Pesquisadores