Changes in the water column structure and paleoproductivity in the western South Atlantic Ocean since the middle Pleistocene: Evidence from benthic and planktonic foraminifera

摘要

Based on an integrated approach (planktonic and benthic foraminifera and stable isotopes) carried out in two cores collected on continental slope of Santos Basin (central Brazil), the paleoceanographic oscillations of the last ～570 ka are documented. Benthic foraminiferal isotopic records coupled with foraminiferal assemblages analyses show ～100 ky long-term oscillation in the superficial productivity along the Middle Pleistocene. These long-term oscillations are interrupted by ～30 ky short-term changes that mark the transition periods of higher productivity (～425-400 ka and ～190-160 ka), and lower (～290-260 ka). The planktonic foraminifera species allowed the recognition of changes in the water column structure and in the superficial productivity observed in the area. Those changes in the superficial waters promoting different organic matter export to the sea floor might have resulted in changes on the more abundant and phytodetritus/opportunist benthic taxa (Epistominella exigua and Alabaminella weddellensis).