(Table 1) Age model of DSDP Site 72-516, supplement to: Pagani, Mark; Arthur, Michael A; Freeman, Katherine H (2000): Variations in Miocene phytoplankton growth rates in the southwest Atlantic: Evidence for changes in ocean circulation. Paleoceanography, 15(5), 486-496

• Main Authors: Pagani, Mark, Arthur, Michael A, Freeman, Katherine H
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2000
• Subjects: Event label; Ageprofile Datum Description; DEPTH, sediment/rock; Age model; Drilling/drill rig; Age model, paleomag, Berggren et al 1985; Leg72; Glomar Challenger; Deep Sea Drilling Project DSDP; Antarctic; Southern Ocean; The Antarctic; Drake Passage; East Antarctic Ice Sheet; Antarc*; Ice Sheet; Planktonic foraminifera
• Online Access: https://dx.doi.org/10.1594/pangaea.848096; https://doi.pangaea.de/10.1594/PANGAEA.848096

Changes in ocean circulation are often credited as the primary control on large-scale climate change during the Miocene. This study investigates the latest Oligocene to middle Miocene evolution of Southern Ocean circulation by evaluating stable isotopic trends of shallow- and deep-dwelling planktonic foraminifera, as well as epsilon-p records reconstructed from the carbon isotopic composition of diunsaturated alkenones in the southwestern Altantic Ocean (Deep Sea Drilling Project site 516). Changes in epsilon-p at site 516 closely paralleled the opening and deepening of the Drake Passage as inferred from seafloor magnetic anomalies. A large negative shift in epsilon-p at ~20.3 Ma is interpreted to reflect an increase in upper water column nutrient concentrations, caused by the onset or strengthening of the Antarctic Circumpolar Current (ACC). Measurable alkenone concentrations disappear by ~17 Ma, prior to a collapse in surface-to-thermocline d18O and d13C gradients. This is interpreted as reflecting a severe decrease in mixed layer nutrient concentrations and reduced proto-Antarctic Intermediate Water influence. The d18O gradient was reestablished by 14.5 Ma, coincident with the hypothesized East Antarctic ice sheet expansion, suggesting a direct relationship between increased strength of the ACC and the largest climate shift of the middle Miocene.