Quaternary geology of the central amazonian lowland area

Erosion of an active fault scarp leads to drainage capture in the Amazon region, Brazil

“…As escarpment denudation has been observed to correlate positively with precipitation amount (Abbühl et al ., ), it is possible that dissection of the Baependi Fault scarp was enhanced by precipitation. Climatic fluctuations to drier periods in the Quaternary (Rossetti et al ., ), and enhanced incision during the last glacial maximum (~20 ka; Irion et al ., , ) have been proposed for this region. Glacial–inter‐glacial pulses of erosion could also have contributed to denudation of the scarp if incision increased at approximately 1.3 Ma (Peizhen et al ., ).…”

“…The elevation difference between the two domains is thought to be a result of Paleogene epeirogenic movement that enhanced the upland relief during regional base‐level fall and rise of the Cretaceous unit along the left margin of the Amazon River (Dantas and Maia, ). Moreover, additional base‐level fall and propagation of 20 to 30 m of incision into the lowest Rio Negro section may have occurred after a 100 m sea‐level drop in the early Pleistocene (Irion et al ., ).…”

“…Generally, Quaternary sediments in the Amazon lowland were deposited in a widespread fresh‐water setting during high sea‐level (Irion et al ., ). However, depositional history since the Plio‐Pleistocene might not have been this simple.…”

Indications of regional scale groundwater flows in the Amazon Basins: Inferences from results of geothermal studies

“…Examples are climate changes produced by advance and retreat of past glaciations. However, unrealistically severe climate changes in the past are required for generating the types of observed perturbations with magnitudes of up to 5 C at depth intervals of 1000e4000 m. In fact, available evidences on evolutionary history of the biosphere and of the vegetation cover in the Amazon region point to near stable climate conditions and rule out the occurrence of severe cooling episodes during quaternary times (see for example, Irion et al, 1994).…”

“…The sediments in the Amazon plain are believed to be derived from the Andean origin, transported over long distances by the fluvial system, the rate of deposition being about one billion tons per year. However, the depositional rates of the suspended sediments are controlled not only by conditions of river transport but also by the interactions of sea level fluctuations on the fluvial system (Irion et al, 1994;Latrubesse et al, 2010).…”