A multiproxy approach to the climate and marine productivity variations along MIS 5 in SE Brazil: A comparison between major components of calcareous nannofossil assemblages and geochemical records

Abstract

In this study, changes in terrigenous input, based on geochemical elementary ratios (e.g. Fe/Ca, Ti/Ca, Ba/Ca, Fe/K), and on marine primary productivity, based on calcareous nannofossil assemblages, from the southeastern Brazilian continental margin are analyzed for the time interval 140 to 55ka (MIS 6 to MIS 4). Variation in the terrigenous input follows the continental paleoclimate records, based on speleothems from SE Brazil, and the summer insolation curve from low latitudes for the southern hemisphere. In turn, marine productivity shows a high correlation with terrigenous input. Terrigenous input maxima correlate to increased marine productivity during sub-stages 5d and 5b. Both, terrigenous input and marine productivity would be strongly controlled by changes in the Intertropical Convergence Zone and winds associated with the South Atlantic Convergence Zone. Thus, NE winds would have prevailed promoting humidity and precipitation rates over SE Brazil, as well as, an intensified wind-driven upwelling and eddies associated with the Brazil Current, which favored the presence of a shallow nutricline. Our results are consistent with that of different proxies presented in other studies providing estimates of changes on the precipitation rate of SE Brazil and changes on marine productivity in the South Atlantic Ocean during MIS 5.