Genesis of textural contrasts in subsurface soil horizons in the Northern Pantanal-Brazil

Abstract

SUMMARYThe Pantanal region can be characterized as a quaternary floodplain with predominant sedimentation in the form of alluvial fans. In the geomorphologic and sedimentary evolution, the avulsion process is inherent to this depositional system and its dynamics, together with surface water floods, influence soil sedimentation on this plain. The knowledge and differentiation of these two events can contribute to a better understanding of the variability of soil properties and distribution under the influence of these sedimentation processes. Therefore, this study investigated the genesis of soils in the Northern Pantanal with textural contrasts in deeper horizons and their relationship with the depositional system dynamics. We analyzed four soil profiles in the region of Barão de Melgaço, Mato Grosso State, Brazil (RPPN SESC Pantanal). Two profiles were sampled near the Rio Cuiabá (AP1 and AP4) and two near the Rio São Lourenço (AP10 and AP11). In AP11, the horizons contrast in particle size between the profile basis and the surface. In AP1, AP4 and AP10, the horizons overlaying the sand layer have similar particle size properties, mainly in terms of sand distribution. In the first case, floods (surface water) seem to have originated the horizons and layers with contrasting texture. In the second case, avulsion is the most pronounced process. Therefore, the two modes can form soils with contrasting texture that are discriminable by soil morphology, based on the distinct features associated to the specific sedimentation processes.Index terms: alluvial soils, hydromorphic soils, fluvial deposition system, alluvial fans, avulsion.(

Spatial distribution of iron and manganese exchangeable wetland soils

“…Essa é uma tendência dos solos da subregião do Pantanal de Poconé (COUTO et al, 2002) e são resultados da deposição de sedimentos em um ambiente lêntico. Já o solo da área 1 apresenta menor teor de argila, por ocorrer em um antigo dique fluvial, cuja sedimentação desses ambientes ocorreram com maior energia,elevando a deposição de areia (TÖRNQVIST e BRIDGE, 2002;NASCIMENTO et al, 2013).…”

Origin of mounds in the Pantanal wetlands: An integrated approach between geomorphology, pedogenesis, ecology and soil micromorphology

“…Clear or abrupt transitions between A and B-horizons, concomitant to sand of different sizes/shapes between horizons, provides evidence of sedimentary processes [14]. Thus, we can assume that higher parts of the landscape are inherited from paleolevees.…”

Flooding effect on mineralogical and geochemical changes in alkaline‐sodic soil system of northern Pantanal wetlands, Brazil

“…These layers are in contact with the boundaries of soil horizons (up to 2 m deep), differentiated by pedogenic processes. In the São Lourenço River fan, where this study was performed, the layers overlying soil horizons were dated at 31,000–47,000 years BP and are essentially coarse textured at the base of soils developed over palaeochannels, palaeolevees and mounds, the most common geomorphic features of the area (Nascimento et al, ).…”

“…At the highest altitudes (palaeolevees), Natrustalfs, with a Bt horizon and high exchangeable sodium percentage (ESP) values, prevail; in the lowest altitudes (floodable areas) Plinthaquults are more common, whereas Quatzipsamments occur in the palaeochannels (Nascimento et al, ; Oliveira Junior, Beirigo, et al, ; Oliveira Junior, Chiapini, et al, ). Soils with high ESP and carbonate precipitates have been observed in the highest ground (approximately 3 m above the floodplain) that originated from these elongated palaeolevees (Nascimento et al, ; Oliveira Junior, Beirigo, et al, ; Oliveira Junior, Chiapini, et al, ), but little is known about their mineralogical characteristics.…”