Late Holocene paleoenvironmental changes in northeast brazil recorded by lacustrine sediments of lake boqueirão.

• Main Authors: Turcq, Bruno, Zocatelli, Renata, Lima Da Costa, Renata, Boussafir, Mohammed, Cordeiro, Renato Campello, Sifeddine, Abdelfettah
• Other Authors: Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences de la Terre d'Orléans (ISTO), Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Université de Tours (UT)-Centre National de la Recherche Scientifique (CNRS), Departamento Geoquimica, Departamento de Geoquímica, Universidade Federal Fluminense Rio de Janeiro (UFF)
• Format: Other/Unknown Material
• Language: English
• Published: HAL CCSD 2011
• Subjects: Late Holocene; Nordeste; Lacustrine sediments; geo; envir; Lower Lake; North Atlantic
• Online Access: https://hal-insu.archives-ouvertes.fr/insu-00843291/file/2011_ABEQUA_Turcq.pdf; https://hal-insu.archives-ouvertes.fr/insu-00843291

International audience Lake Boqueirão is located at 5°S latitude, on the Brazilian Atlantic coast, a region where the climate is directly influenced by the Intertropical Convergence Zone (ITCZ) displacements. A short (1m) core "Boqc0701" was collected at 7.5m water depth based on a seismic survey. Granulometry, Total Organic Carbon, Organic matter Rock Eval (Hydrogen Index (HI), Oxygen Index (OI)) allowed us discriminating five sedimentary intervals through the last 3000 cal yrs BP. Phase E (3000 to 2050 cal yr BP) presents the largest Granulometry, TOC, HI and OI fluctuations of the entire core. The most probable cause of these variations is a great instability of the lake level during this period. Phase D (2050 to 1830 cal yr BP) is marked by an increase in sedimentation rate and a higher contribution of a well preserved OM, of algal origin, that this interpreted as a higher and more stable lake level. During phase C (1830 to 1550 cal yrs BP), low HI and high OI indicate the input of more oxidized, degraded and detrital OM, reflecting a lower lake level. In phase B (1550 to 1470 cal yr BP) OM quality and quantity (HI and TOC) indicates an algal contribution. During phase A the high stability of Rock Eval proxies contrasts with variations of TOC and Granulometry. These changes in lake level can be compared with other tropical South America high resolution records. It seems that there is a correspondence between phases of low ENSO, cool North Atlantic Ocean and Boqueirão wet phases. A prolonged dryness occurred in Lake Boqueirão since 570 cal yrs BP, till the last decades. This phase corresponds to the Little Ice Age characterized by a cooler North Atlantic Ocean (Mann et al., 2009). These data indicate that the teleconnection pattern between tropical Atlantic, ENSO and Northeast Brazil rainfalls has changed in the past 3000 years.