Vegetation Change in Southwestern Amazonia (Brazil) and Relationship to the Late Pleistocene and Holocene Climate

The Late Quaternary climate in Amazonia is an issue still open to debate, with hypotheses varying from alternate dry and wet episodes to stable climate with undisturbed rainforest. We approach this question using δ 13 C, C/N, and, to a lesser extent, δ 15 N from deposits derived from four cores, with the results combined with published pollen data from two of these cores. These data were analyzed within the context of radiocarbon dating, which revealed ages ranging from 42.8–41.8 to 2.3–2.2 cal ka BP. Fluvial channel and floodplain deposits with freshwater phytoplankton recorded a trend of wet climate with dry episodes before ~40 cal ka BP, followed by humid and cold climate until the Last Glacial Maximum, with intensified aridity towards the end of the Late Pleistocene. Peaks of increased contributions in C 4 land plants in the mid- to late Holocene were not synchronous and have no correspondence with Amazonian Holocene dry episodes, being due to sedimentary processes related to fluvial dynamics during the establishment of herbaceous fields on abandoned depositional sites. Thus, the climate remained wet in the Holocene, which would have favored the expansion of the Amazonian rainforest as we see today

Amazon rainforest · Climate change · Fluvial · Geography · Glacial period · Holocene · Last Glacial Maximum · Physical geography · Pleistocene · Quaternary · Radiocarbon dating · Rainforest · Structural basin · Fish biology, ecology, and behavior · Geology and Paleoclimatology Research · Isotope Analysis in Ecology · Ecology · Geology · Oceanography · Paleontology

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