Primary productivity in the western tropical Atlantic follows Neogene Amazon River evolution

E. I. Lammertsma*, S. R. Troelstra, J. A. Flores, F. Sangiorgi, F. Chemale, D. A. do Carmo, C. Hoorn

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The Amazon River nutrient-rich plume currently triggers large-scale phytoplankton blooms in the otherwise oligotrophic western tropical Atlantic Ocean. Little is known about the onset and development of this high productivity system, although a direct link to the transcontinental Amazon River evolution can be expected. The Amazon submarine fan, located on the Brazilian Equatorial Margin (BEM), contains a unique sediment archive of the river's history and associated environmental changes in the marine realm. This study represents the first marine microfossil multi-proxy approach applied to any sedimentary record in the submarine fan area for the time interval encompassing the onset and development of the transcontinental Amazon River system. To reconstruct Miocene to Pleistocene changes in surface- and bottom water conditions we analyzed organic-walled dinoflagellate cyst- and benthic foraminiferal assemblages, respectively. Moreover, terrestrial- and freshwater palynomorph abundances were studied to provide a link between fluvial input and marine environmental changes. In addition, a planktonic foraminiferal biostratigraphy is constructed to verify the available calcareous nannofossil-based age model. Our data show that in the early- mid Miocene up to ~13 Ma limited fluvial input reached the BEM and primary productivity was elevated, after which distinctly low productivity conditions prevailed. After the birth of the transcontinental Amazon at ~9 Ma surface water productivity initially increased slightly. Consistently high surface water productivity and decreased bottom water oxygenation followed increasing terrestrial input after the (early) Pliocene. The temporal consistency between records from the Amazon Fan and the more distant Ceará Rise reflects large-scale marine environmental changes followed the development of the Amazon River, likely related to increased climatic variability in the Amazon Basin during the Plio-Pleistocene.

Original languageEnglish
Pages (from-to)12-21
Number of pages10
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume506
Early online date6 Jun 2018
DOIs
Publication statusPublished - 1 Oct 2018

Funding

We acknowledge the Brazilian Oil and Gas Agency (ANP) for allowing us to publish selected 1-BP-3 APS well data (Well 2, following Figueiredo et al., 2009 , and Hoorn et al., 2017 ). Funding: CLIM-AMAZON European Union's Seventh Framework Program ( FP7/2007-2013 ) and the Universidade de Brasília funded E.L. (grant 295091 ) and facilitated this project. We greatly thank Natasja Welters for sample processing, Suzette Flantua for constructing the map, Roberto D'Avila, Emilson Soares, Osman Varol, Stephen Lowe, David Pocknall, Ricardo Pinto, Els van Soelen and Peter Bijl for constructive discussions, and Jorge Figueiredo and Paulus van der Ven for initiating the cooperation Petrobras-UvA.

FundersFunder number
Brazilian Oil and Gas Agency
Natasja Welters
Universidade de Brasília295091
Seventh Framework ProgrammeFP7/2007-2013
Agência Nacional do Petróleo, Gás Natural e Biocombustíveis

    Keywords

    • Amazon Fan
    • Brazilian Equatorial Margin
    • Foraminifera
    • Neogene
    • Organic-walled dinoflagellate cysts

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