The location of Site 1087 in the Southern Cape Basin near the external boundary of the Benguela coastal upwelling system and close to the Agulhas Current retroflection regime, offers the opportunity to identify specific events in this area, such as the latitudinal and lateral migrations of the hydrographic fronts and the interconnections between the Indian and Atlantic Oceans. The oxygen and carbon isotope records of four species of planktonic and benthic foraminifers provide new information on the climatic and hydrologic changes during the last 500 k.y. in this part of the South Atlantic.
The oxygen isotope records at Site 1087 show typical G-IG cycles with a few marked differences in the global ocean signature due to the local hydrologic regime. The coldest period corresponds to MIS 12, and the warmest periods occur during MISs 5 and 11, both for surface and deep waters. The variations of the 18O gradients between surface and deep waters are very abrupt and subjected to rapid, high-frequency oscillations; these oscillations are related to sporadic injections of Indian Ocean waters and to important and permanent modifications of the position of frontal boundaries and of the depth of the thermocline.
The carbon isotope records at Site 1087 do not follow the G-IG cycles, but they show abrupt and short-term oscillations associated with long-term trends. The variations in the 13C gradients between surface and deep waters allow us to identify an extended period of high productivity between 260 and 425 ka that is contemporary with the mid-Brunhes carbonate event. In the surface waters, the 13C gradients also display very sharp fluctuations associated with long-term trends that are controlled both by the trophic regime and by the depth of the thermocline.