Diatom slides were prepared using either of the following methods. In order to quantify the number of diatom valves deposited per gram of sediment, diatom slides were prepared according to the method described in Scherer (1994). This method allows for a direct comparison of diatom accumulation in the sediments between samples. Samples prepared in this way include data about the mass of sample prepared, transit length examined, and the area of the beaker used for settling. Qualitative slides were prepared as simple smear slides by suspending sediment in less than 5 ml deionized water, transferring a drop of this solution to a cover slip, and allowing the cover slip to air dry. In both cases, cover slips were mounted on cleaned microscope slides using hyrax in toulene (refractive index: 1.7135). At least 300 diatom valves were identified in at least three random transects across each slide using a light microscope at magnifications from 1000x to 1250x (see Armand et al., 2005; Sancetta, 1979; Sancetta and Silvestri, 1986; Scherer, 1994). The portion of the slide that was examined was measured using a stage micrometer. Partial valves were counted according to the methods of Schrader and Gersonde (1978). All diatoms were identified to the species level when possible following published taxonomic descriptions. On the table attached, diatom counts are presented either as raw counts or transformed into relative percent abundances. Absolute abundances (diatoms per gram sediment) can be calculated following the methods of Scherer (1994) for quantitatively prepared slides.

Grain size labeled, "Coulter" was measured on samples collected in 2006 using the Coulter LS200 laser diffraction particle analyzer. Grain size labeled, Malvern was measured on samples collected in 2006 and 2007 using the Malvern Mastersizer 3000 with the Hydro MV automated wet dispersion unit. Pretreatment of sediments to remove organics, carbonates, biogenic opal, and to disperse clay particles follows Sakamoto (2005); however, samples were not centrifuged between chemical treatments to avoid losing very fine sediments. Instead chemical volumes were adjusted so that each treatment was neutralized before the next chemical was added. Both laser diffraction grain size analyzers return the weight percent of particles. The Coulter uses 92 bins ranging from 0.375 to 1822 μm and the Malvern Mastersizer uses 100 bins ranging from 0.01 to 3500 μm. In addition, we report the Dx10, Dx50 (median), Dx90 grain size, laser obscuration, and % clay, % silt, and % sand in each sample measured on the Malvern Mastersizer.

Lead and Cesium isotopes were measured down the length of HLY 0702 DBSB/164. Sediments were dried on an 80° C oven, homogenized, and crushed using a mortar and pestle. A Canberra GL2020R low-energy Germanium gamma well detector with low-background cryostats was used to measure lead and cesium isotopes in each sample. Count times averaged 2-3 days until the standard error was appropriately small. Pb-214 was assumed to be in secular equilibrium, and so was used as a proxy for supported 210Pb. Unsupported (atmosphere-derived) 210Pb was calculated as the difference between 210Pb and 214Pb. Initially, samples were chosen every 3 cm down core. After a small 137Cs peak was located, the core was resampled at 1 cm intervals above and below this peak and analyzed using an identical protocol.

All subsampled HAPS cores collected during Healy 0601 were split along the core axis and x-rayed at the UMass Amherst University Health Services to determine sediment density. Cores were laid 101 cm from the beam and x-rays were taken using 60-70 kV and 5 mAs beam characteristics. X-radiographs were scanned at 2400 dpi to create digital images of the cores. Magnetic susceptibility was measured in 0.5 cm intervals using a Bartington Magnetic Susceptibility Meter Model MS2 on these same cores.

Diatoms.csv: This sheet has species names as column headers. The data are reported as raw counts. Percent_Diatoms.csv: This sheet has species names as column headers. The data are reported as percents. Grain_Size_Coulter.csv: columns 1-4 are self explanatory; columns 5-97 are grain size measured in microns. Values are reported as weight percent for each grain size. Grain_Size_Malvern.csv: columns 1-8 are self-explanatory; columns 9-109 are grain size measured in microns. Values are reported as weight percent for each grain size. PbCs.csv: This data is only for the core: Healy 0702 DBSB/164. MS.csv: column 1 is depth in (cm) downcore. Columns 2-8 are samples. Data is listed by depth and reported in SI units.