for both 
13C and 18O.
Sediment samples from Holes 1220B and 1221C were taken at 5-cm intervals and were allowed to dry overnight in a Memmert Wisconsin oven at 50°C. The samples were homogenized by grinding with a mortar and pestle and were weighed on a Mettler Toledo MX5 microbalance with a precision of ~1 µg. Sample size varied depending on the carbonate content of the interval, published in the Leg 199 Initial Reports volume (Lyle, Wilson, Janecek, et al., 2002). About 500 µg of sediment was analyzed in samples with high carbonate content, whereas ~1000 µg of sediment was analyzed in samples with low CaCO3 content. Carbon and oxygen isotopic composition of these sediments were measured at Scripps Institution of Oceanography (SIO; USA) using an automated common acid bath carbonate preparation device (Fairbanks device) attached to a Finnigan MAT252 mass spectrometer. NBS-19 was used as a standard, with 7 standard analyses per run of 40 unknowns. The average instrument error is <0.1 for both 13C and 18O.
Sediment samples with volumes of ~10 cm3 were taken at 5-cm intervals in Hole 1220B through the Paleocene/Eocene Thermal Maximum (PETM) interval. These samples were allowed to dry overnight at 50°C before being washed with deionized water through a 38-µm sieve. Samples from Hole 1221C were those used for a study of phosphorous chemistry and were processed using similar methods to ours at University of California, Santa Cruz (USA), by Christina Faul. Her sample set consisted of 20-cm3 core pieces taken at 2-cm spacing through the core of the PETM and at 5-cm intervals above and below the excursion interval. In both Holes 1220B and 1221C, the benthic foraminifers Nuttalides truempyi and Cibicidoides spp. were picked from the >250-µm fraction for isotopic analyses. Approximately 10–15 individuals of each genus or species were selected so that an average signature for the interval was obtained. Carbon and oxygen isotopic composition of these benthic foraminifers were measured at SIO with the same methodology reported for bulk carbonate.
The P/E boundary interval in both Holes 1220B and 1221C consists of a series of colorful beds in what is otherwise a foraminifer-nannofossil ooze. The boundary is identified partly by the last appearance of Paleocene benthic foraminifers at 199.68 meters below seafloor (mbsf) in Hole 1220B and at 154.31 mbsf in Hole 1221C. In addition, the P/E boundary in Hole 1220B is marked by the occurrence of the "excursion fauna" of planktonic foraminifers (Lyle, Wilson, Janecek, et al., 2002). In both holes, the boundary beds change upsection from yellow dolomite-rich sediments to rose-pink, black, dark brown, and, eventually, tan calcareous ooze in the interval spanned by the most negative benthic foraminifer 13C ratios. These multicolored beds, representing the core of the P/E boundary interval, have low carbonate content.
The coarse (>38 µm) fraction in samples from Holes 1220B and 1221C are dominated by benthic foraminifers because of the dissolution of most planktonic forms. Planktonic foraminifers are sparse but occur throughout most of the section in Hole 1220B, whereas Hole 1221C is nearly devoid of them. Benthic foraminifers are abundant at both sites except within a carbonate dissolution horizon occurring between 199.40 and 199.70 mbsf in Hole 1220B and between 154.10 and 154.30 mbsf in Hole 1221C. Foraminifers are generally well preserved in Hole 1220B, particularly within and above the PETM, but typically display a coarse, sugary coating in Hole 1221C. Below the carbonate dissolution horizon, benthic foraminifers in both holes commonly have a sugary surface texture, and both planktonic and benthic foraminifers in Hole 1220B are occasionally overgrown by glassy, yellow dolomite rhombs. In some intervals of both sites, particularly below the P/E boundary, dolomite rhombs compose a significant portion of the fine fraction. Benthic foraminifers containing dolomite rhombs on their surface were not selected for isotope analysis.
Carbonate preservation is distinctly worse in Hole 1221C than it is in Hole 1220B. The different quality of preservation between the sites may reflect a slightly deeper paleodepth for Hole 1221C than Hole 1220B because we expect that differences in the actual age of the seafloor beneath these sites and bottom roughness might account for differences as great as several hundred meters in their actual paleodepths. The two sites also differ in paleolatitude, with the area around Hole 1220 having crossed the equator about the time of the P/E boundary, whereas Hole 1221C was nearly 200 km to the north (Lyle, Wilson, Janecek, et al., 2002). Hence, Hole 1221C may have been farther from the belt of equatorial carbonate accumulation at the P/E boundary and in an area with a shallower carbonate compensation depth than Hole 1220B.
