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doi:10.2204/iodp.proc.320321.206.2013

Results

The results are represented in Figure F1. A total of 364 measurements were conducted on samples from between 4.2 and 258.8 meters below seafloor (mbsf) (Table T1). According to the ship-based stratigraphic model, this interval extends from the latest middle Miocene to the latest Pleistocene (Pälike et al., 2010). The data show relatively large variability: biogenic silica contents across all samples vary between 1.9 and 69.5 wt% (average = 16.0 wt%) (Table T1).

Fine-scale variability occurs throughout the studied interval. Although measurements between the uppermost part of the sediment column at Site U1337 downhole to ~260 mbsf are not completely continuous, some general trends are recognized. Highest contents occur between 228 and 185 mbsf (uppermost interval of the late Miocene) and 108 and 93 mbsf (corresponding to the Miocene–Pliocene transition). Both intervals of highest biogenic silica content match the occurrence of diatom-rich laminations at Site U1337 (Pälike et al., 2010) (Fig. F1). Following the low values between 170 and 165 mbsf, biogenic silica content increases uphole until 110 mbsf. The upper half of the lower Pliocene contains more biogenic silica in than during the lower half, and the range of biogenic silica during the Pleistocene resembles that of the uppermost Pliocene. The lowest biogenic silica contents occur in the uppermost middle Miocene (254–240 mbsf).

Future work on Site U1337 will include filling the gaps (Fig. F1), extending the measurements downhole to the lowermost Neogene, applying an age model, calculating the mass accumulation rate of biogenic silica, and evaluating the spectral evolution. Additionally, we will compare our results to other records from Site U1337, and from high latitudes, in order to establish possible interhemispheric connections.