Measurements were taken on Sites 1095 (325 samples), 1096 (407 samples), and 1101 (145 samples). One sample per section was used as a sample interval. Total carbon (TC) and TOC were determined using a LECO CS-125 analyzer. After drying two subsamples of approximately 30 mg for each bulk sample, TC was directly measured in the first subsample, whereas TOC was measured in the second subsample following treatment with 0.25-N HCl to remove inorganic carbon. Inorganic carbon (IC) was calculated and converted to weight percent CaCO3 by using equations 1 and 2:
where 8.333 is the stoichiometric calculation factor for CaCO3. The precision of the TC and TOC measurements is within ±0.25% (Wolf, 1991).
On the same sample sets as mentioned above, the weight percent of the bulk parameter >63 µm (coarse fraction), which is used as a further proxy for ice-rafted debris (IRD), was measured. All bulk samples were dry frozen, and the total mass of the bulk sample was determined. There was no further disaggregation procedure used. In a second step, >63-µm content was determined after wet sieving an 8-cm3 bulk sample into the <63-µm fine fraction and the >6-µm coarse fraction. The >63-µm fraction was subsequently dried, and the mass was determined by weighing the sample split.
The >63-µm fraction samples from Cores 178-1095A-1H through 10H were analyzed at a microscope to define quantitatively the composition of the coarse-fraction components. The >63-µm samples were dry sieved into five subsamples (63-125 µm, 125-250 µm, 250-500 µm, 500-1000 µm, and >1000 µm) using an AMT Sonic Sifter. Coarse-fraction compositional analysis was limited to the 125- to 500-µm interval. After a further subdivision by microsplitting into representative subsamples of countable grain amounts, 300 to 500 grains from each sample were analyzed microscopically, counted, and distinguished as follows:
The component grain percent was calculated by referring the counts of each component to the total counts of a sample as equal to 100%.