Dust arriving in the Amazon basin over the past 7,500 years came from diverse sources

Juliana Nogueira,Gilberto Vaz,Marilia H Shimizu,Keila Cristina Aniceto,Renato C Cordeiro,Carla Neto,Heitor Evangelista,Gabriel Martins,Artur Bastos Neto,Cybelli G G Barbosa,Luciane S Moreira,Ricardo H M Godoi,Claudio De Morisson Valeriano,Bruno Turcq,Abdelfettah Sifeddine

doi:10.1038/s43247-020-00071-w

Abstract

A large amount of dust from the Sahara reaches the Amazon Basin, as observed with satellite imagery. This dust is thought to carry micronutrients that could help fertilize the rainforest. However, considering different atmospheric transport conditions, different aridity levels in South America and Africa and active volcanism, it is not clear if the same pathways for dust have occurred throughout the Holocene. Here we present analyses of Sr-Nd isotopic ratios of a lacustrine sediment core from remote Lake Pata in the Amazon region that encompasses the past 7,500 years before present, and compare these ratios to dust signatures from a variety of sources. We find that dust reaching the western Amazon region during the study period had diverse origins, including the Andean region and northern and southern Africa. We suggest that the Sahara Desert was not the dominant source of dust throughout the vast Amazon basin over the past 7,500 years.

Highlights

A large amount of dust from the Sahara reaches the Amazon Basin, as observed with satellite imagery
Since the Amazon rainforest covers a vast area of 5500000 km[2], we investigate whether a Saharan dust signal/fingerprint is measurable in the greatly distant region of the central-western Amazon sector during the Holocene
Our results suggest that the atmospheric deposition of long-range dust material from arid/semi-arid zones occurred during the mid-tolate Holocene in central-western Amazon in measurable amounts

Summary

Introduction

A large amount of dust from the Sahara reaches the Amazon Basin, as observed with satellite imagery. We present analyses of Sr-Nd isotopic ratios of a lacustrine sediment core from remote Lake Pata in the Amazon region that encompasses the past 7,500 years before present, and compare these ratios to dust signatures from a variety of sources. Two ratios are commonly used: 87Sr/86Sr and 143Nd/144Nd, where 87Sr is a decay product of 87Rb, a long-lived radionuclide (half-life = 4.88 × 1010 years) and 143Nd derived from 147Sm (half-life = 1.06 × 1011 years) These nuclides are used as conservative fingerprints of sediment and dust provenance for the Pleistocene[14,40], Holocene[41], and modern

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Conclusion