Steps in the intensification of Benguela upwelling over the Walvis Ridge during Miocene and Pliocene

摘要: Upwelling is a significant part of the ocean circulation controlling largely transport nutrient-rich cold waters to surface and therefore influencing productivity global climate. The Benguela upwelling system (BUS) one major areas in world. Previous reconstructions BUS mainly focused on onset intensification southern central parts, but changes northern have been rarely investigated detail. Using Late Miocene Pliocene organic-walled dinoflagellate cyst record ODP Site 1081, we reconstruct discuss early history over Walvis Ridge with special focus movement Angola-Benguela Front (ABF). We suggest that during Angola Current flowed southwards more frequently than today because ABF was probably located further south as result weaker meridional temperature gradient. A possible strengthening gradient latest combination uplift south-western Africa intensified along coast increased upwelling’s filaments Ridge. An intermediate period from 6.2 5.5 Ma shown by dominance Habibacysta tectata, cysts cool-tolerant known Atlantic, indicating changing oceanic conditions contemporaneous Messinian Salinity Crisis. From 4.3 on, signal got stronger again were well-mixed nutrient-rich. Our results indicate northward migration 7 initial stepwise BUS.