Paleoceanography reconstruction and paleoclimate inferences on Brazilian equatorial margin in Mid- and Late Holocene

Author(s)

Nancy Kazumi Taniguchi

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto Oceanográfico (IO/DIDC)
• Defense date: 2015-08-05

Examining board members

Silvia Helena de Mello e Sousa; Francisco William da Cruz Júnior; Michel Michaelovitch de Mahiques

• Advisor: Silvia Helena de Mello e Sousa

Abstract

Sedimentological and geochemical analyzes on sedimentary record GeoB 16204-2 (01°9.75 \'S, 42°20:30\'W, 1210 m depth) allowed to recognize three periods with different paleoceanographic settings and paleoclimatic over the last 8100 years for the Brazilian equatorial margin . The first period (8100 - 5000 cal yr BP) was characterized by more intense hydrodynamic conditions, lower marine influence and greater continental contribution, evidenced by lower values of sortable silt, higher percentage of sand fraction, lower CaCO3 content and higher values of the Ti / Ca and Fe / Ca ratios. The second period (5000 - 2500 cal yr BP) showed greater fluctuations in the intensity of bottom currents and decreased continental contribution indicated by variations of sortable silt, poorly defined mode in the particle size distribution (PSD) and decrease trend of the Ti / Ca and Fe / Ca ratios. The third period (2500 cal yr BP - present), was dominated by less intense hydrodynamic conditions and less continental contribution indicated by for mode PSD about 7 Φ and lower values of Fe/Ca and Ti/Ca ratios. Over the 8100 years there has been a weakening of North Brazilian Current, probably associated with a weakening of the Atlantic Meridional Overturning Circulation (AMOC) and also the southward migration of the Intertropical Convergence Zone (ITCZ). Besides influencing ocean currents the migration of the ITCZ also contributed to changes atmospheric conditions, favoring drier conditions in the study area during the Late Holocene. Sea surface temperature ans salinity show little change in the last 5000 years, with values close to the current climatological average, 26.4 ° C and 36.5. (AU)

• FAPESP's process: 13/10676-1 - Reconstitution of sea surface temperature and salinity in the equatorial Brazilian in Late Holocene: paleoclimate inferences
• Grantee: Nancy Kazumi Taniguchi
• Support Opportunities: Scholarships in Brazil - Master