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
Jan 19, 2016
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
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MEGAFAN MODEL
Okavango Megafan (Gumbricht & McCarthy, 2001)
Tectono and climatic setting for the formation of megafans (Nichols & Fisher, 2007)
Nichols & Fisher 2007
Taquari (Assine, 2005)
Kosi (Chakraborty et al. 2010)
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Escudo das Guianas
Fan-shaped deposits of the Pantanal Setentrional Basin
Viruá
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Morphology of the Viruá megafan
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Morphology of the Viruá megafan
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Chronology of the Viruá megafan
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Viruá megafan
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Viruá megafan
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Viruá megafan
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MODEL FOR A MEGAFAN IN A HUMID TROPICAL REGION
- Tropical areas with high temperature and high precipitation
-Modern tributaries
AMAZONIAN REGION
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MEGAFANS IN THE PANTANAL SENTENTRIONAL BASIN
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TECTONIC INFLUENCE IN THE PANTANAL SENTENTRIONAL BASIN
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ORIGIN OF THE VIRUÁ MEGAFAN
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VIRUÁ MEGAFAN- TECTONIC INFLUENCE
VIRUÁ MEGAFAN: TECTONICS + MONSOONAL-LIKE CLIMATE
Assine 2005
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- Late Pleistocene-Holocene deposits are much more widespread inthe 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 wasprobably 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.
CONCLUSIONS
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