Dune whitening and inter-dune freshwater ponds in NE Brazil

Noam Levin*, Haim Tsoar, Luis P. Maia, Vanda Claudino Sales, Hans Herrmann

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

The changes in color of sand dunes from white to yellow or red is often interpreted to signify their age or their source materials. In this study we demonstrate the effect seasonal inter-dune freshwater ponds have on the bleaching of the color of sand dunes by iron reduction in the anaerobic conditions they create. By combining spectral measurements of field samples of dune sand together with the analysis of satellite images covering three dune fields in NE Brazil (Lençóis Maranhenses, Jericoacoara and Canoa Quebrada) we demonstrate its existence in the field. In areas where ponds cover 41% of the dune field (as in Lençóis Maranhenses) an almost total bleaching in the color of the sand occurs after which the dunes remain white with no relation to distance from the coastline. In areas with less ponds (e.g. Jericoacoara or Canoa Quebrada) dune whitening is less active, and there are areas where dune rubification occurs. As this process may have occurred in other dune fields during past climate conditions that may have been different from current ones, interpretations of dunes age based on their color should be handled with care.

Original languageAmerican English
Pages (from-to)1-15
Number of pages15
JournalCatena
Volume70
Issue number1
DOIs
StatePublished - 1 Jun 2007
Externally publishedYes

Bibliographical note

Funding Information:
We thank Dan G. Blumberg from the Department of Geography and Environmental Development for the use of the ASD for the spectral measurements. We would like to thank Juliana Cristina Fukuda and Erika Fernandes Pinto from the IBAMA headquarters of the Lençóis Maranhenses national park of Brazil for their help in fieldwork during summer 2005. We also thank Hans Herrmann from the Swiss Federal Institute of Technology in Zurich (ETHZ) and Vanda Claudino Sales from the Federal University of Ceará for their comments on an earlier version of this paper. We appreciate the remarks made by the anonymous referees, and thank them for their contribution to the improvement of this manuscript. This study has been funded by the Volkswagen Foundation (Volkswagen-Stiftung) ( http://www.volkswagen-stiftung.de/ ), as part of the following research: “The palaeoclimate and environmental implications of the aeolian sand encroachments into the coast of Ceará State, NE Brazil”. The Kreitman Fellowship Foundation has supported Noam Levin in his post-doctoral research.

Keywords

  • Coastal dunes
  • Iron oxides
  • Ponds
  • Reduction
  • Remote sensing
  • Rubification

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