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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Origin, transport and deposition of leaf-wax biomarkers in the Amazon Basin and the adjacent Atlantic

Texto completo
Autor(es):
Haeggi, Christoph ; Sawakuchi, Andre O. ; Chiessi, Cristiano M. ; Mulitza, Stefan ; Mollenhauer, Gesine ; Sawakuchi, Henrique O. ; Baker, Paul A. ; Zabel, Matthias ; Schefuss, Enno
Número total de Autores: 9
Tipo de documento: Artigo Científico
Fonte: GEOCHIMICA ET COSMOCHIMICA ACTA; v. 192, p. 149-165, NOV 2016.
Citações Web of Science: 3
Resumo

Paleoenvironmental studies based on terrigenous biomarker proxies from sediment cores collected close to the mouth of large river systems rely on a proper understanding of the processes controlling origin, transport and deposition of biomarkers. Here, we contribute to the understanding of these processes by analyzing long-chain n-alkanes from the Amazon River system. We use the delta D composition of long-chain n-alkanes from river bed sediments from the Amazon River and its major tributaries, as well as marine core-top samples collected off northeastern South America as tracers for different source areas. The delta C-13 composition of the same compounds is used to differentiate between long-chain n-alkanes from modern forest vegetation and petrogenic organic matter. Our delta C-13 results show depleted delta C-13 values (-33 to -36%) in most samples, indicating a modern forest source for most of the samples. Enriched values (-31 to -33%) are only found in a few samples poor in organic carbon indicating minor contributions from a fossil petrogenic source. Long-chain n-alkane delta D analyses show more depleted values for the western tributaries, the Madeira and Solimoes Rivers (-152 to -168%), while n-alkanes from the lowland tributaries, the Negro, Xingu and Tocantins Rivers (-142 to -154%), yield more enriched values. The n-alkane delta D values thus reflect the mean annual isotopic composition of precipitation, which is most deuterium-depleted in the western Amazon Basin and more enriched in the eastern sector of the basin. Samples from the Amazon estuary show a mixed long-chain n-alkane delta D signal from both eastern lowland and western tributaries. Marine core-top samples underlying the Amazon freshwater plume yield delta D values similar to those from the Amazon estuary, while core-top samples from outside the plume showed more enriched values. Although the variability in the river bed data precludes quantitative assessment of relative contributions, our results indicate that long-chain n-alkanes from the Amazon estuary and plume represent an integrated signal of different regions of the onshore basin. Our results also imply that n-alkanes are not extensively remineralized during transport and that the signal at the Amazon estuary and plume includes refractory compounds derived from the western sector of the Basin. These findings will aid in the interpretation of plant wax-based records of marine sediment cores collected from the adjacent ocean. (C) 2016 Elsevier Ltd. All rights reserved. (AU)

Processo FAPESP: 11/06609-1 - Proveniência, transporte e estocagem de sedimentos nos rios amazônicos
Beneficiário:André Oliveira Sawakuchi
Linha de fomento: Auxílio à Pesquisa - Regular
Processo FAPESP: 11/14502-2 - Fatores reguladores da emissão de metano (CH4) em ambientes deposicionais dos Rios Negro, Tapajós, Xingu e Amazonas
Beneficiário:Henrique Oliveira Sawakuchi
Linha de fomento: Bolsas no Brasil - Doutorado
Processo FAPESP: 12/17517-3 - Resposta da porção oeste do Oceano Atlântico às mudanças na circulação meridional do Atlântico: variabilidade milenar a sazonal
Beneficiário:Cristiano Mazur Chiessi
Linha de fomento: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Jovens Pesquisadores