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Dynamics and chronology of eolian depositional systems in Amazonia: implications for quaternary evolution of open vegetation ecosystems

Grant number: 18/12472-8
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): October 01, 2018
Effective date (End): December 31, 2020
Field of knowledge:Physical Sciences and Mathematics - Geosciences
Principal Investigator:André Oliveira Sawakuchi
Grantee:Fernanda Costa Gonçalves Rodrigues
Home Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The Amazonia is known worldwide for its high biodiversity and large transcontinental river system. Changes in the physical landscape, like drainage expansion and precipitation variation, are recognized as an important driver of biota diversification. Previous studies have focused on the role of rivers for the Amazonian biota diversification. However, some regions of Amazonia host unique eolian paleodune fields within amid tropical forest, suggesting drier phases, with lower plant cover density for development of eolian dunes through reworking of fluvial sediments. This comprises paleodunes developed during the Last Glacial Maximum (LGM) (23-19 ka), which are associated to several patches of open vegetation, including white-sand ecosystems, savanna and cerrado. Such open forest ecosystems also play a significant role for biota diversification and host endemic and specialist species. Some of those patches develop on sandy substrates, with surface fluvial and/or eolian depositional morphologies. The study of the sedimentary dynamics and controlling factors of the Amazonian eolian systems would provide better understanding about the development of open forest ecosystems as well as the response of the Amazon forests to climate changes. Despite its relevance as a record for climate and vegetation changes, few studies focused on the Amazonian eolian systems when compared to fluvial systems. Within this context, this project intends to characterize the spatial distribution, chronology and stabilization/activation phases of the Amazonian eolian dunes. Thus, it is expected to understand the relationship among climate change, eolian sedimentation and expansion, stabilization and retraction of open vegetation ecosystems in Amazonia. To reach this goal, surface depositional eolian features will be recognized and mapped through remote sensing for comparison with open vegetation ecosystems distribution. Specific eolian deposits, identified through remote sensing, were chosen for stratigraphic, sedimentological (composition and texture) and geochronological studies. The chronology of build up and stabilization of eolian deposits will be determined using Optically Stimulated Luminescence (OSL) dating. Proxies of dune activation and stabilization based on textural (grain size) and compositional (environmental magnetism and elemental ratios) properties of sediment will allow to reconstruct climate variations in specific areas for comparison with Late Quaternary climate changes from other paleoclimate archives, especially marine sediment cores and speolthem that record precipitation changes in the South America Monsoon System. Phylogeographic studies, conducted by the project co-supervisor research group, will enable to track the demographic history of open vegetation ecosystems biota and its comparison to abiotic changes recorded in the eolian deposits. Thus, it is expected that this project will contribute with part of the understanding of the complex relationship between landscape changes and biota diversification in Amazonia. (AU)