Cronological improvement of the last deglaciation in Brazilian continental margin records

Abstract

The species from Globorotalia menardii plex (Globorotalia menardii menardii; G. menardii flexuosa, G. menardii tumida e G. menardii fimbriata) are one of the principal indicators of glacial and interglacial boundaries through the Atlantic Ocean's Quaternary. The ecological affinity of these species agrees with the transition between these periods, being present during interglacials and rare or absent during glacials. Although, it is still unknown specifically which variable causes this abundance variation on G. menardii plex considering that superficial temperature variations during the last glacial was no greater than 2 ÚC (Berger & Wefer 1996). Since its first observation by Schott (1935) in marine sediments, the boudaries based on theses species have been employed on biozoneaments and its last restablishment is associated to Holocene's onset (~11.000 years ago). The G. menardii plex Atlantic population is drastically reduced during the last glacial and when the ocean conditions become favorable to its development the population is restablished. Preliminar data evidences a diachronous restablishment of G. menardii plex along the brazilian continental margin. The present study intends to compreheend the G. menardii plex restablishment pattern along brazilian continental margin during the last deglaciation to investigate which oceanographic processes act on its distribution through glacial and interglacial periods. (AU)