Geology and Geomorphology of the Pantanal Basin

Abstract

What is an inlier sedimentary basin? What are the main mechanisms of sedimentary infilling? How do the depositional systems behave? And last, but certainly not the least, what geological events occurred in the last million years and continue to take place in the Pantanal area today? These issues are considered in this chapter, based on available geological, geomorphological, and geochronological datasets. The Pantanal is an active sedimentary basin with numerous faults and associated earthquakes. Movements along these faults cause subsidence on blocks within the basin, generating depressions that are highly susceptible to flooding, and also create accommodation space for sediment storage. One hypothesis on the origin of the Pantanal Basin relates the processes of subsidence with tectonic activity in the Andean orogen and foreland system during the Quaternary. Alternatively, the lack of geochronological data leaves open the possibility that the basin formed much earlier, perhaps during an interval of widespread tectonism in Brazil during the Eocene. The modern Pantanal depositional tract is composed of the Paraguay River trunk system, numerous fluvial megafans and interfan floodplains, and thousands of lakes, many of them integral to the Nhecolândia landscape. The Pantanal's geomorphology is most likely the product of climatic fluctuations and environmental changes that have been occurring since the Late Pleistocene.

Avulsive Rivers in the Hydrology of the Pantanal Wetland

“…9; see [15]). Accordingly, the drainage system is very complex due to the coexistence and interaction of these different systems.…”

“…The Pantanal is a large subsiding sedimentary basin that continuously creates accommodation space for deposition [15]. The rivers deposit sediments carried from the catchment-source area, filling portions of the basin, whereas other areas remain starved.…”

“…The Paraguay River plain has geomorphologic heterogeneity in consequence of its geologic position on the western faulted border of the sedimentary basin [15]. The river-mainstem plain comprises five distinct fluvial floodplain compartments, each one presenting different morphologic characteristics, channel pattern, and hydrologic functioning (Fig.…”

“…The distributary drainage network and the dimensions of the alluvial systems of the Pantanal Basin [22][23][24] are typical of fluvial megafans [15]. The Taquari megafan is unquestionably the most studied of them and the largest distributary fluvial system in the basin with~50,000 km 2 [25][26][27][28].…”

Late Quaternary climate variability and terrestrial carbon cycling in tropical South America

“…The landscape of the basin mostly consists of large fluvial fans deposited by a number of rivers that flow from upland regions to the western side of the basin, eventually converging with the north-south flowing Paraguay River (Assine et al, 2015). Laguna La Gaiba (LLG, 17.75°S, 57.58°W) is a large, shallow lake (maximum area and depth of ~100 km 2 and 4-6 m, respectively) located along the upper Paraguay River (Figure 2).…”