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Large alluvial rivers transport water and sediment across continents and shape lowland landscapes. Repeated glacial cycles have dominated Earth's recent climate, but it is unclear whether these rivers are sensitive to such rapid changes. The Amazon River system, the largest and highest-discharge in the world, features extensive young terraces that demonstrate geologically rapid change temporally correlated with changes in runoff from Quaternary climate cycles. To test the plausibility of a causal relationship, we use a simple model to estimate from empirical measurements how quickly a river profile responds to changes in discharge or sediment supply. Applying this model to data from 30 gauging stations along alluvial rivers throughout the Brazilian Amazon, we find that many rivers of the Amazon basin can respond faster than glacially induced changes in runoff or sediment flux. The Amazon basin is unusually responsive compared to other large river systems due to its high discharge and sediment flux, narrow floodplains, and low slopes. As a result, we predict that the Amazon basin has been highly dynamic during Quaternary glacial cycles, with cyclical aggradation and incision of lowland rivers driving repeated habitat and environmental change throughout the region. This dynamic landscape may have contributed to the exceptional biodiversity of the region and patterns of ancient human settlement. [ABSTRACT FROM AUTHOR]

Abstract: Ancient anthrosols known as Amazonian dark earths or terra preta are part of the human built landscape and often represent valuable landscape capital for modern Amazonian populations in the form of fertile agricultural soils. The fertility, resilience, and large stocks of carbon in terra preta have inspired research on their possible role in soil fertility management and also serve as an example for a growing biochar industry it is claimed will sequester carbon for climate change mitigation. Although there is considerable scientific and public interest in terra preta, there is still much debate and little concrete knowledge of the specific processes and contexts of its formation. Research indicates that the formation of terra preta occurred mainly in midden deposits, themselves patterned around habitation areas, public areas, and routes of movement. Data from topographic mapping, soil analyses, and excavations in three regions of Amazonia demonstrate a widespread pattern of anthrosol formation in ring-shaped mounds surrounding flat terraces that extend across large areas of prehistoric settlements. It is hypothesized that there is a widespread type or types of occupation where the terraces were domestic areas (houses or yards) surrounded by refuse disposal areas in middens which built up into mounds over time, forming large deposits of terra preta and creating what could be called a ‘middenscape’. Initial results support the hypotheses, showing the interrelationship of residential and public areas, anthrosols, routes of movement, and natural resources. The patterning of anthrosols in ancient settlements indicates the use of space and can therefore serve as a basis for comparison of community spatial organization between sites and regions. [Copyright &y& Elsevier]