Development of the Amazon Valley During the Middle to Late Quaternary: Sedimentological and Climatological Observations

Pleistocene sea-level changes affected the Amazon River as far as 2,500 km inland. This results on one hand with the formation of large floodplains of the Amazon and the lower parts of its tributaries during sea-level heights and on the other hand with a deeply incised river system during low sea-level stages. This was most effective since Mid-Pleistocene when the changes of sea-level got stronger. This could be shown from the deeply incised valleys of Negro and Tapajos Rivers. During Last Glacial Maximum the slope of the Amazon below its junction with Tapajos River increased by the factor 10, resulting probably in a braided River. Paleofactors of sediment cores taken from Central Amazonia lakes and from Tapajos River give no hint for a significant change in climate.