Sediment samples were submitted to the National Ocean Sciences AMS Facility (NOSAMS) at the Woods Hole Oceanographic Institution (Table T1). To determine if there was a difference in source area and a potential age difference between the fine and coarse fraction, grain size splits were made. Separate dates from the fine fraction (<63 µm), total bulk sediment, and bulk sand-sized fraction were obtained. AMS dates were calculated using 5568 yr as a half-life of radiocarbon and are presented without reservoir corrections or calibration to calender years. Radiocarbon dates provided by A. Holbourn (pers. comm.) were obtained from benthic foraminifers, and those dates provided by James et al. (2000) were obtained from species-specific bryozoans (Celleporaria sp.). Sediment accumulation rates were calculated using dates from the <63-µm bulk sediment fraction, the bulk sand fraction, and the bulk sediment fraction (Table T2).
Based upon the radiocarbon dating, 20-cm3 samples at ~1 m intervals were obtained from the upper 20 meters below seafloor (mbsf) or less from Sites 1132, 1130, and 1134 (western transect) (Figs. F2, F3, F4; Tables T3, T4, T5) and from Sites 1129, 1131, and 1128 (eastern transect) (Figs. F5, F6, F7; Tables T5, T6, T7). Grain size distributions were measured for the coarse fraction (>63 µm) using the settling tube method (Gibbs, 1974) and for the fine fraction (<63 µm) using the pipette method (Folk, 1965).
Acid leaching (Milliman, 1974) was used to determine calcium carbonate content.
Using the insoluble residue from the calcium carbonate analysis, total organic carbon content was determined through the loss on ignition (LOI) method (Dean, 1974). Approximately 1 g of sample residue (weighed to four decimal places in a crucible of known weight) was placed in a 550°C furnace for 4 hr, cooled, and reweighed. Resulting weights from the before and after difference were entered into an equation that related to the original sample before calcium carbonate analysis.
Carbonate mineralogy was
determined through powder X-ray diffraction (XRD) using a Scintag XDS 2000 
/
goniometer with a 2.2-kW sealed copper X-ray source. Bulk carbonate analyses
were performed on all samples, which were ground and prepared using the glass
slide method and dried at room temperature (Moore and Reynolds, 1997).
Quantitative carbonate mineralogy was determined using a calibration of the
ratio of aragonite, dolomite, and high-Mg calcite (HMC) to the sum of low-Mg
calcite (LMC) and HMC. See Swart
et al. (this volume) for additional details.
