Evolution of the Western Amazon Lowland Relief: impact of Andean foreland dynamics

The congruency in the depositional origin and age of the uppermost sedimentary strata forming non-flooded rainforest ground (terra firme) in the western and central Amazon lowlands is a much debated subject. Here we conclude from the study of remote sensing imagery that active Andean foreland dynamics have played a major role in the evolution of the Plio-Pleistocene fluvial landscape in the western Amazon. Foreland dynamics have resulted in a terra firme composed of late Tertiary alluvium and younger alluvial terraces and plains. In Peru, thermoluminescence and C-14 dating show local aggradation of this younger alluvium between 180 and 30 ka. The documented high age heterogeneity of the terra firme has implications for considerations of the biogeography of the Amazon forest.