Title
Marine sediments from southeastern Brazilian continental shelf: A 1200year record of upwelling productivity
Date Issued
01 January 2011
Access level
open access
Resource Type
journal article
Author(s)
Souto D.
de Oliveira Lessa D.
Albuquerque A.
Barbosa C.
Research Institute Development
Universidad Federal Fluminense
Abstract
A sediment core from the Cabo Frio coastal shelf (-23.19S, -41.8W; 117m depth), was analyzed for TOC, C/N ratio, organic petrography and planktonic foraminiferal content to evaluate variations in local productivity caused by changes in upwelling intensity and its relation to regional and global climatic variations during the last millennium. The Cabo Frio core recorded the last 1200years of sedimentation, with rates varying from 0.11 to 0.32mmyr-1. Foraminiferal and organic geochemical analyses indicate the occurrence of three distinct periods of productivity. From 850AD until 1070AD, foraminifera fluxes consisting primarily of Turborotalita quinqueloba indicate stronger South Atlantic Central Water (SACW) transport onto the shelf, which induced high biological productivity that was also recorded by high TOC and marine palynomorphs content and a low C/N atomic ratio. This period coincided with a northward displacement of the atmospheric Intertropical Convergence Zone (ITCZ) and South Atlantic High (SAH) systems driven by positive temperature anomalies in the North Atlantic Ocean during the Medieval Climate Anomaly (MCA). From 1070 until 1500AD, low TOC flux and planktonic foraminifera fluxes and high C/N atomic ratios suggest a reduction in marine productivity, probably driven by reduced transport of SACW associated with the southward displacement of the SAH and weakening of northeasterly winds. The period between 1500 and 1830AD, which corresponds to the Little Ice Age, is marked by increased fluxes of planktonic foraminifera, principally of Globigerina bulloides and Globigerinita glutinata. These species mark an increase in productivity linked to SACW upwelling, supported by the enhancement of northeasterly winds and southward displacement of the ITCZ and SAH. © 2010 Elsevier B.V.
Start page
49
End page
55
Volume
299
Issue
February 1
Language
English
OCDE Knowledge area
Geociencias, Multidisciplinar Química orgánica
Scopus EID
2-s2.0-78650615329
Source
Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN of the container
00310182
Sponsor(s)
The authors thank the Instituto de Estudos do Mar Almirante Paulo Moreira (IEAPM) and the crew of Av.Pq. Oc. Diadorim, from the Brazilian Navy, for the logistical support during sediment coring. We also would like to thank the CLIMPAST Project (CNPq / IRD-France - N. 490735/2006-1 ), Geochemistry Network of PETROBRAS R&D and the Brazilian National Petroleum and Biofuels Agency (ANP) for the financial support to this project. This paper is also a contribution to the ESCARCEL project funded by French National Agency of Research (Program VMC, Project ANR-06-VULN-010) .
Sources of information: Directorio de Producción Científica Scopus