Title
A mineralogical and organic geochemical overview of the effects of Holocene changes in Amazon River flow on three floodplain lakes
Date Issued
01 December 2014
Access level
open access
Resource Type
journal article
Author(s)
Moreira L.S.
Moreira-Turcq P.
Kim J.H.
Cordeiro R.C.
Caquineau S.
Mandengo-Yogo M.
Sinninghe Damsté J.S.
Research Institute Development
Publisher(s)
Elsevier
Abstract
A synthesis of the impacts of the Amazon River hydrological changes on the sedimentation process of organic matter (OM) in three different floodplain lakes (Santa Ninha, Maracá, and Comprido lakes) is presented in this study. Today the Santa Ninha and Maracá lakes are directly and permanently connected with the main channel of the Amazon River, in contrast to Comprido Lake, which is indirectly and periodically influenced by the Amazon River due to its greater distance from the main channel. All three lake sediment records showed a reduced river inflow due to dry climatic conditions during the early and middle Holocene followed by an increased fluvial input during the wetter late Holocene. In Santa Ninha and Maraca Lakes, the reduced river inflow period was recorded by sediments with a low abundance of smectite (on average ~20wt.%), a clay mineral mainly transported by the fluvial system, high total organic carbon (TOC) contents (on average ~8.2wt.%), and a predominantly acidic soil OM input evidenced by high concentrations (on average 180μggTOC-1) of branched glycerol dialkyl glycerol tetraethers (GDGT). During the late Holocene, a higher smectite abundance (on average ~43 wt.%) and a lower TOC content (on average ~1.4 wt.%) pointed to greater dilution by riverine lithogenic matter. This change was accompanied by a proportional increase in the aquatically produced crenarchaeol, suggesting a higher lake water level. In Comprido Lake, a sedimentation gap occurred during the early and middle Holocene. The wetter late Holocene, since 3000calyears BP, was characterized by high TOC values (on average ~9wt.%) and a sharp increase in soil OM input as recorded by an increase in branched GDGT concentrations (on average ~81μggTOC-1), but the smectite content was low (on average ~14%). This combination suggests that the soil OM input to Comprido Lake from the local catchment area became dominant during the wet-climate late Holocene due to the large distance of the lake from the Amazon River main channel. Consequently, our study shows that the sedimentation processes of OM in Amazonian floodplain lakes were strongly influenced by variations in the hydrodynamic regime of the Amazon River during the Holocene. However, the impacts of the variations on the three floodplain lakes were different depending on the distance of each lake from the main channel of the Amazon River.
Start page
152
End page
164
Volume
415
Language
English
OCDE Knowledge area
Mineralogía
Geoquímica, Geofísica
Subjects
Scopus EID
2-s2.0-84910095052
Source
Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN of the container
00310182
Sponsor(s)
This research was supported by the French Research Institute for Development (IRD) and by the HYBAM Research Program (Hydrology and Geochemistry of the Amazonian Basin, www.mpl.ird.fr/hybam/ ) in the frame of its cooperation agreement with the Brazilian Research Centre (CNPq process nos. 492685/2004–05 and 690139/2003–09 ). This project was also supported by the project INSU Paleo2 — PASCAL (Past climate change impacts on carbon accumulation in Amazonia floodplain lakes (2010–2012)) and by the French project ANR ELPASO 2010 BLANC 608-01 . L. Moreira's work was supported by a CNPq fellowship. The research leading to these results has also received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement no. [ 226600 ]. The authors would like to thank the technical groups of Agência Nacional das Águas from Brazil (ANA) and Companhia de Pesquisa dos Recursos Minerais (CPRM, Manaus) for their help during the cruise as well as J. Ossebaar at NIOZ for analytical support. We are also very grateful to P. A. Meyers and the two anonymous reviewers for their constructive comments that substantially improved the manuscript.
Sources of information:
Directorio de Producción Científica
Scopus