Middle Pleistocene sea surface temperature in the Brazil-Malvinas Confluence Zone: Paleoceanographic implications based on panktonic foraminIfera

CECILIA LAPRIDA; NATALIA GARCÍA CHAPORI; CRISTIANO CHIESSI; ROBERTO A. VIOLANTE; SILVIA WATANABE; VIOLETA TOTAH

MICROPALEONTOLOGY

MICROPALEONTOLOGY PRESS

Año: 2011 vol. 57 p. 183 - 195

0026-2803

We reconstructed the surface hydrography in the western South Atlantic during the Middle Pleistocene based on faunal and oxygen isotope analyses of planktonic foraminifera. Planktonic foraminiferal assemblages, modern analog technique estimates of sea surface temperature (SST) and isotopic ratios of core SP1251 (38º29,7´S - 53º40,7´W / 3400 m water depth) record a glacial interval that occurred during the Middle Pleistocene. Sediments were deposited between 0.3 and 0.12 Ma during MIS6 or 8, due to the presence of Globorotalia truncatulinoides and the paucity of Globorotalia crassaformis. Estimates of winter and summer SSTs suggest that the western South Atlantic at 38ºS was 4-6ºC colder than at present. High relative abundances of subantarctic taxa and particularly the dominance of the planktonic foraminifera Neogloboquadrina pachyderma(left)support lower than present SSTs throughout the recorded period. The oxygen isotopic composition of G. truncatulinoides suggests a northward shift of the Brazil-Malvinas Confluence Zone and of the associated mid-latitude frontal system during this Middle Pleistocene cold period. The northward migration of the confluence generated a stronger than present influence of subantarctic waters at the core site during the recorded Middle Pleistocene glacial.