A multiproxy approach to reconstruct hydrological changes in Eastern Amazonia during the late Holocene;

Abstract

Deciphering hydroclimatic imbalances in the Lower Amazon River Basin is challenging. Speleothem records show a consistent increase in precipitation over western Amazonia from the mid- to late Holocene, but other parts of the basin appear to have responded differently. Previous literature has regarded the contrasting difference in Amazonian precipitation as a dipole response to orbital-scale insolation variability. However, variations in eastern Amazonian speleothem records seem to be weakly correlated with precession cycles. To reconstruct regional hydroclimate variability in eastern Amazonia, we will investigate two sediment cores collected from the Tapajós Ria. We propose analyzing the hydrogen and stable carbon isotope compositions of long-chain n-alkanes to infer changes in paleoprecipitation and vegetation. Additionally, we will use major element distributions, luminescence sensitivity signals, and neodymium isotopes to reconstruct changes in the relative influx of Amazon River sediments into the Tapajós Ria.