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SEDIMENTOLOGY AND EVOLUTION OF A LATE PLEISTOCENE-HOLOCENE HUMID MEGAFAN IN NORTHERN BRAZIL

This study focuses on the sedimentology and evolution of a megafan in Northern Brazil, exploring its morphology, chronology, and the tectonic and climatic factors that contributed to its formation. The research highlights the widespread occurrence of similar fan-like morphologies in the Amazonian wetlands and provides insight into the origin and characteristics of these unique depositional environments.

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SEDIMENTOLOGY AND EVOLUTION OF A LATE PLEISTOCENE-HOLOCENE HUMID MEGAFAN IN NORTHERN BRAZIL

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  1. SEDIMENTOLOGY AND EVOLUTION OF A LATE PLEISTOCENE-HOLOCENE HUMID MEGAFAN IN NORTHERN BRAZIL Dilce F. Rossetti Hiran Zani Marcelo C. L. Cohen Édipo H. Cremon

  2. 1 MEGAFAN MODEL Okavango Megafan (Gumbricht & McCarthy, 2001) Nichols & Fisher 2007 Taquari (Assine, 2005) Tectono and climatic setting for the formation of megafans (Nichols & Fisher, 2007) Kosi (Chakraborty et al. 2010)

  3. 1 Fan-shaped deposits of the Pantanal Setentrional Basin Escudo das Guianas Viruá

  4. 1 Morphology of the Viruá megafan

  5. 1 Morphology of the Viruá megafan

  6. 1 Chronology of the Viruá megafan

  7. Viruá megafan 1

  8. Viruá megafan 1

  9. Viruá megafan 1

  10. MODEL FOR A MEGAFAN IN A HUMID TROPICAL REGION 1 AMAZONIAN REGION • Modern tributaries • Tropical areas with high • temperature and high • precipitation

  11. MEGAFANS IN THE PANTANAL SENTENTRIONAL BASIN 1

  12. 1 TECTONIC INFLUENCE IN THE PANTANAL SENTENTRIONAL BASIN

  13. ORIGIN OF THE VIRUÁ MEGAFAN 1

  14. VIRUÁ MEGAFAN- TECTONIC INFLUENCE 1

  15. VIRUÁ MEGAFAN: TECTONICS + MONSOONAL-LIKE CLIMATE Assine 2005

  16. CONCLUSIONS 1 • Late Pleistocene-Holocene deposits are much more widespread in • the Amazonian wetlands than previously recognized; • They occur as numerous, large, fan-like morphologies in the PSB, with • the Viruá fan in Roraima being one of them; • This feature displays morphological (i.e., large-scale fan geometry, • divergent drainage networks, gently-dipping slopes, concave-up and • convex-up longitudinal and transversal profiles) and sedimentological • (dominantly sandy lithologies and fining and coarsening upward units • related to active channels, overbank sand/sheets and terminal fan lobe, • abandoned channel, floodplain, debris flow deposits and lake/pond muds) characteristics compatible with residual deposits of a megafan; • -The establishment of a megafan in this humid tropical region was • probably the due to the creation of new space for sediment • accommodation by tectonic reactivation added to a favorable, • monsoonal-like climate, with high summer temperatures and drought contrasting with high water discharge during wet winters.

  17. 1 THANKS!

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