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doi:10.2204/iodp.proc.331.202.2015

Results

The solid phase Mg from Site C0014 (Fig. F1A) is highly variable, with low values in the uppermost sediment package and higher values between 30 and 40 mbsf. We show here the dissolved Mg profiles from the cores in which we have corresponding solid-phase analyses and which show the expected depletion of Mg relative to the seawater value within the zone of high Mg concentrations (Fig. F1B). The Ca/Al ratios generally show lower values than those expected for average upper continental crust, with the exception of the uppermost samples (Fig. F2A). The K/Al ratios are quite variable, with low values near the zone of high Mg/Al and at slightly shallower depths for some of the samples (Fig. F2B, F2C). Generally speaking, the upper sediment package from core to core can be variable, and this variability was noted for the pore fluid results from this site (Takai et al., 2011). Below ~40 mbsf, K/Al values are slightly enriched relative to average upper continental crust (Fig. F2B). Ba/Al is also generally lower than upper continental crust values, with the exception of the uppermost sediment package and at ~12–15 mbsf (Fig. F2B). Fe/Al is generally enriched in the uppermost 40 mbsf, whereas Fe_R/Fe_T enrichments are generally confined to the upper 20 mbsf (Fig. F3A, F3B). Below these depths, Fe/Al is depleted relative to average upper crust values and the Fe_R/Fe_T ratio approaches zero, meaning that very little of the iron is extractable at these depths. The upper sediment package is depleted in Mn, but a broad elevated Mn/Al maximum is centered between ~30 and 50 mbsf (Fig. F3C, F3D). There is some suggestion of elevated Mn_R/Mn_T in this region, particularly with respect to the upper sediment package; however, much of the data set suggests Mn_R concentrations are ~10% or less of the total Mn.

In contrast to the data from Site C0014, the data from Site C0017 has much smaller variability in the sedimentary Mg contents, with few samples significantly enriched over the value for the upper continental crust (Fig. F4A). This observation is consistent with the dissolved profile, which exhibits little deviation from the ambient seawater value (Fig. F4B). Ca/Al ratios in the upper ~40 m are elevated over the background, and deeper samples have values that hover near the upper continental crust ratio (Fig. F5A). The K to Al ratios are relatively constant, as are the Ba to Al ratios (Fig. F5B, F5C). Fe to Al ratios are generally slightly enriched relative to the upper continental crust value but vary little with depth (Fig. F6A). The Fe_R to Fe_T ratios are higher on average relative to Site C0014, but no particular pattern is apparent in the data (Fig. F6B). Mn to Al ratios also do not vary significantly compared to Site C0014 and generally scatter about the crustal ratio, with the average value slightly below that ratio (Fig. F6C). The Mn_R to Mn_T ratio has a distinct minimum below 50 mbsf with values increasing with depth (Fig. F6D).

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