We explored the potential to use the stable isotopic compositions of planktonic foraminifera as a proxy for the position of the Brazil-Malvinas Confluence (BMC) in the Argentine Basin. For this purpose, we measured the oxygen and carbon isotopic compositions of Globigerinoides ruber (pink and white varieties measured separately), Globigerinoides trilobus, Globigerina bulloides, Globorotalia inflata and Globorotalia truncatulinoides (left- and right-coiling forms measured separately) from a latitudinal transect of 56 surface sediment samples from the continental slope off Brazil, Uruguay and Argentina between 20 and 48°S. Lowest oxygen isotopes values were found in G. ruber (pink), followed by G. ruber (white) and G. trilobus reflecting the highly stratified near surface water conditions north of the BMC. Globigerina bulloides was present mainly south of the BMC and records subsurface conditions supporting earlier plankton tow studies. Globorotalia inflata and G. truncatulinoides (left and right) were both available over the whole transect and calcify in the depth level with the steepest temperature change across the BMC. Accordingly, the delta18O of these species depict a sharp gradient of 2‰ at the confluence with remarkably stable values north and south of the BMC. Our data show that the oxygen isotopic composition of G. inflata and G. truncatulinoides (left and right) are the most reliable indicators for the present position of the BMC and can therefore be used to define the past migration of the front if appropriate cores are available.

The abbreviations of the stratigraphy are defined as follows: IS, isotopic stratigraphy; 14C, 14C AMS dating, calibrated calendar age is given in parentheses; and SBF, stained benthic foraminifera. a This study; b Mollenhauer et al. (2006, doi:10.1016/j.dsr.2006.05.005); c Heil et al. (subm.); d Dürkoop (1998); e Harloff and Mackensen (1997, doi:10.1016/S0377-8398(96)00059-X). / Samples were taken from the uppermost centimeter of 54 multicores and 2 boxcores.

Supplement to: Chiessi, Cristiano Mazur; Ulrich, Shannon; Mulitza, Stefan; Pätzold, Jürgen; Wefer, Gerold (2007): Signature of the Brazil-Malvinas Confluence (Argentine Basin) in the isotopic composition of planktonic foraminifera from surface sediments. Marine Micropaleontology, 64(1-2), 52-66