Boussafir M. auteur aut IRD Sifeddine Abdelfettah auteur aut IRD Jacob J. auteur aut IRD Foudi M. auteur aut IRD Cordeiro R. C. auteur aut IRD Albuquerque A. L. S. auteur aut IRD Abrao J. J. auteur aut IRD Turcq Bruno auteur aut IRD text journalArticle eng text/pdf born digital access Lagoa do Caco is an equatorial lake in northeast Brazil, where the Inter-Tropical Convergence Zone (ITCZ) enters the South American continent, and so at a key position for deciphering Quaternary climatic variation. Preliminary results have shown that the sedimentary organic matter (OM) in the lake records the shifts in the ITCZ since the Last Glacial Maximum. The nature and fate of the OM have been determined by studying surface sediments and potential OM sources. We present here the results of organic petrographic and Rock-Eval pyrolysis assessments of the biological origin and preservation state of the OM in modern sediments from two deep transects of the lake. The results led us to understand how an oligotrophic lake has accumulated 6 m of OM-rich sediment during the last 20 kyr. Palaeoenvironmental studies have shown that the lake level fluctuated during this time. Our results explain the influence of lake bathymetric variation on early diagenesis and enable interpretation of the corresponding sedimentary OM record, which is dependent on the bathymetric variation. specialized 064 47 88-98 2012 0146-6380 https://www.documentation.ird.fr/hor/fdi:010055945 10.1016/j.orggeochem.2012.03.013 0146-6380 [F B010055945] https://www.documentation.ird.fr/hor/fdi:010055945 https://www.documentation.ird.fr/intranet/publi/2012/07/010055945.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2012-07-24 2017-08-23 fdi:010055945 fre