@Article{RossettiMoliCrem:2016:GeLaAm,
author = "Rossetti, Dilce de F{\'a}tima and Molina, Eder Cassola and
Cremon, {\'E}dipo Henrique",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and
{Universidade de S{\~a}o Paulo (USP)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)}",
title = "Genesis of the largest Amazonian wetland in northern Brazil
inferred by morphology and gravity anomalies",
journal = "Journal of South American Earth Sciences",
year = "2016",
volume = "69",
pages = "1--10",
month = "Aug.",
keywords = "Gravity anomaly, Morphology, Northern Amazonia,
Pleistocene-Holocene, Sedimentary basin.",
abstract = "The Pantanal Setentrional (PS) is the second largest wetland in
Brazil, occurring in a region of northern Amazonia previously
regarded as part of the intracratonic Solim{\~o}es Basin.
However, while Paleozoic to Neogene strata are recorded in this
basin, the PS constitutes a broad region with an expressive record
of only Late Pleistocene and Holocene deposits. The hypothesis
investigated in the present work is if these younger deposits were
formed within a sedimentary basin having a geological history
separated from the Solim{\~o}es Basin. Due to the location in a
remote region of low accessibility, the sedimentary fill of the PS
wetland remains largely unknown in subsurface. In the present
work, we combine geomorphological and gravity data acquired on a
global basis by several satellite gravity missions to approach the
geological context of this region. The results revealed a wetland
characterized in surface by a low-lying terrain with wedge shape
and concave-up geometry that is in sharp contact with highland
areas of Precambrian rocks of the Guiana Shield. Such contact is
defined by a series of mainly NE- or NW-trending straight
lineaments that eventually extend into both the Guiana Shield and
the PS wetland. Also of relevance is that a great part of the PS
wetland sedimentary cover consists of dominantly sandy deposits
preserved as residual paleo-landforms with triangular shapes
previously related to megafan depositional systems. These are
distributed radially at the northern margin of the PS, with axis
toward basement rocks and fringes toward the wetland's center, the
latter containing the largest megafan landform. The analysis of
gravity anomaly data revealed a main NNE-trending chain ~500 km in
length defined by high gravity values (i.e., up to 60 mGal); these
are bounded by negative anomalies as low as -90 mGal. The chain
with positive gravity anomaly marks the center of a subsiding area
having a geological evolution that differs from the adjacent
intracratonic Solim{\~o}es Basin. Deep rifting associated with
the rise of high-density material from the mantle in replacement
of low-density continental crust is hypothesized as the most
likely load-driving mechanism responsible for the subsidence of
the PS sedimentary basin. Alternatively, this might be a shallow
basin formed during the Late Quaternary due to mild subsidence of
a high-density basement. This process would have been caused by
tectonic reactivations of NE-trending strike-slip faults along a
zone of low elastic thickness of the lithosphere that
characterizes this region of South American platform.",
doi = "10.1016/j.jsames.2016.03.006",
url = "http://dx.doi.org/10.1016/j.jsames.2016.03.006",
issn = "0895-9811",
language = "en",
targetfile = "Rossetti_genesis.pdf",
urlaccessdate = "27 abr. 2024"
}