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doi:10.2204/iodp.proc.303306.209.2009

Results

Sites U1302 and U1303

Downcore variations of rock magnetic parameters are shown in Figure F2. NRM variations show similar trends with χ, χ_ARM, Mr, Ms, and HFMS. Decreases of NRM, χ, and χ_ARM values are found below 115 meters composite depth (mcd). The lithology changes from nannofossil silty clay to matrix-supported intraclast conglomerate downward (Tables T1, T2). Hcr/Hc and Ms/Mr ratios suggest that most magnetic grains in the samples are in the pseudosingle-domain (PSD) region (Day et al., 1977). At 59 and 78–83 mcd, a decrease in these ratios is found and lithology changes from clayey silt nannofossil ooze to slity clay (Table T2).

Site U1304

Rock magnetic parameters are shown in Figure F3. NRM, χ, χ_ARM, Ms, and HFMS values fluctuate considerably and show similar downcore patterns. Extremely low values of NRM, χ, and χ_ARM are observed at 46–47, 57–58, and 95–105 mcd. The Hcr/Hc ratio is characterized by two maxima, and minima of Mr/Ms are recognized at these intervals. These values show that magnetic grains are possibly in the multidomain region. Except for these depths, Hcr/Hc and Ms/Mr ratios indicate that magnetic grains in the samples are in the PSD region (Day et al., 1977). The laminated diatom ooze is recognized in these intervals (Tables T1, T2).

Site U1308

Downcore rock magnetic parameters are shown in Figure F4. NRM shows that relatively high values are found between 140 and 145 mcd. However, no notable change is observed in lithology at that depth interval (Tables T1, T2). The value of χ gradually increases downhole and is similar in overall trends to χ_ARM and Mr. The lithology gradually changes from nannofossil ooze silty clay to nannofossil ooze with depth (Tables T1, T2). Hcr/Hc and Mr/Ms values show that most magnetic grains in the samples are in the PSD region (Day et al., 1977).

Thermomagnetometry

Low-temperature magnetometry results are shown in Figure F5. Samples were mainly selected from the upper sediments. The Verwey transition suggesting the presence of magnetite (110–120 K) (Verwey, 1939) is clear in Site U1302 and U1303 samples (Fig. F5A–F5E). Low-temperature magnetometry results from Site U1304 sediments are shown in Figure F5F–F5I. We can observe the unclear Verwey transition, which is indicative of the occurrence of maghemitization (Özdermir et al., 1993).

The thermomagnetic curve of the topmost sediments from Site U1308 is shown in Figure F6. The Curie point of magnetite (at 580°C) is not clearly defined in the heating curve; it only appears on the cooling curve. In low-temperature magnetometry results for Site U1308 samples, the shape of the Verwey transition of Figure F5J–F5M is much more pronounced compared to that in Figure F5N. Verwey transitions are invisible above 7.5 mcd (Fig. F5J–F5K), but they are slightly evident below 11.0 mcd (Fig. F5L–F5N).

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