TRACING PAST CIRCULATION CHANGES IN THE WESTERN SOUTH ATLANTIC BASED ON PLANKTONIC FORAMINIFERA

TitleTRACING PAST CIRCULATION CHANGES IN THE WESTERN SOUTH ATLANTIC BASED ON PLANKTONIC FORAMINIFERA
Publication TypeJournal Article
Year of Publication2008
AuthorsToledo, FAL, Costa, KB, Pivel, MAG, Campos, E
JournalRevista Brasileira de Paleontologia
Volume11
Issue3
Pagination169-178
Abstract

In this study, we traced past oceanographic changes in the southeastern Brazilian Continental Margin based on the ratio between two planktonic foraminifera species (Globigerina bulloides and Globigerinoides ruber), along a core located close to the transition between the tropical and subtropical biogeographic provinces. Each species is representative of a biogeographic province and has excluding ecological preferences. According to our interpretation, periods of low G. bulloides/G. ruber values would characterize a stronger influence of the warm, oligotrophic tropical water and, conversely, periods of high G. bulloides/G. ruber values correspond to a stronger influence of colder and nutrient-richer waters. Changes in the relative influence of the different water masses are strongly dependent on the regional wind field which affects the upper-level circulation mostly by the latitudinal displacement of the bifurcation of the South Equatorial Current which, in turn, has strong impacts on the Brazil Current’s strength and on the intensity of the upwelling regime in the study area. The analysis of the last 30 kyr record, suggests that productivity was highly increased both around the Last Glacial Maximum and the Younger Dryas event. In between these events, the record suggests that productivity was severely decreased during deglaciation. Also, our record suggests a gradual decrease in productivity from 11 kyr BP through the Holocene which can be explained by a progressively stronger Brazil Current resulting from a southward displacement of the Intertropical Convergence Zone. Our results are consistent with other studies providing estimates of changes in trade wind strength and in the extent of the climatic belts through time.

DOI10.4072/rbp.2008.3.03