Analytical methods
Planktonic foraminiferaThe ooze samples of Site U1348-Core 2R (10 cm-spacing; 15 levels) were weighed for 1.0 g, soaked in 3% H 2 O 2 solution for a few hours, gently spray-washed on a 63 µm-opening screen, and oven-dried at <50 °C. To preclude any possibility of carbonate dissolution or mechanical fragmentation through sample processing, water for dilution of H 2 O 2 and washing was adjusted to pH = ~10 with a small amount of NH 4 OH solution, and an ultrasonic bath not used for cleaning. Each washed sample was dried, sieved on a 125 µm-opening screen, and split accurately using an Otto-splitter if necessary. It was then picked and counted for total foraminifera with c. 200-400 individuals of planktonic foraminifera. Identification of planktonic foraminifera was at species-level based on multiple literature sources, in particular Smith & Pessagno (1973), Robaszynski et al. (1984), Nederbragt (1991), and Petrizzo et al. (2011). Scanning electron microscopic study was performed using a Philips XL-30 ESEM at the National Museum of Natural History, Smithsonian Institution. Unabbreviated names and IODP sample IDs of specimens in Figure 1 are as follows: -Interval (i), top-left to clockwise: Sigalia deflaensis rugocostata (U1348-2R-CC, 23-24 cm); Ventilabrella eggeri (U1348-2R-CC, 10-11 cm); Hendersonites carinatus (U1348-2R-CC, 3-4 cm); Marginotruncana undulata (U1348-2R-CC, 23-24 cm); Marginotruncana sinuosa (U1348-2R-CC, 23-24 cm); Dicarinella concavata (U1348-2R-CC, 27-30 cm); Dicarinella asymetrica (U1348-2R-CC, 23-24 cm).-Interval (ii), left to right: Globotruncanita elevata (U1348-2R-1, 90-91 cm); Contusotruncana plummerae (U1348-2R-1, 91-92 cm).-Interval (iii), top-left to clockwise: Globotruncanita stuarti (U1348-2R-1, 20-21cm); Globotruncanita subspinosa (U1348-2R-1, 11-12 cm); Pseudoguembelina costulata (U1348-2R-1, 11-12 cm).-Interval (ii)-(iii), top to bottom: Globotruncana stephensoni (U1348-2R-1, 90-91 cm); Globotruncanita atlantica (U1348-2R-1, 51-52 cm); Globotruncana arca (U1348-2R-1, 90-91 cm); Globotruncana bulloides U1348-2R-1, 91-92 cm).
NannofossilsCalcareous nannofossils were examined in smear slides prepared from raw sediment samples. The slides were observed using standard light microscope techniques, under crossed polarizers, transmitted light, and phase contrast at 1000× magnification. The nannofossil taxonomy and zonation scheme followed Bown
