Barium Increasing Prior to Opal during the Last Termination of Glacial Ages in the Okhotsk Sea Sediments |
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Authors: | Masayasu M Sato Hisashi Narita Shizuo Tsunogai |
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Institution: | (1) Marine and Atmospheric Geochemistry Lab., Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan |
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Abstract: | Ba and Ti in a sediment core (10 m long) from the Okhotsk Sea, covering the last 120 kyrs, were measured. The authigenic Ba
(Baex) contents were calculated and compared with the opal. The correlation coefficient between Baex and opal was quite small (r = 0.34), but it greatly grew larger (r = 0.90), if the Baex contents were multiplied by a simple function increasing with depth, except for two intervals. This may be due to the gradual
change in the sedimentation environment during the glacial ages. One of the exceptional interval is found at 60–170 cm in
depth, corresponding to 10–17 calendar kyr ago, the last termination period of glacial ages, where the Baex began to increase prior to opal. Since the calcium carbonate contents similarly increased prior to the opal increase, the
Baex may be also related to calcareous organisms besides siliceous ones. The other is the last interglacial period around 120
kyr ago when the opal contents were high, but those of the Baex were not increased. This can be explained, if the Baex was reduced to sulfide and dissolved away in a strongly anoxic environment during the biologically productive period. During
the glacial ages, the mass accumulation rate (MAR) of lithogenic Ti was about twice the amount of that during the interglacial
ages. For opal, however, the contrast between the glacial and interglacial ages was more remarkable in its MAR than in its
concentration in sediments, due to the larger variation in the bulk sedimentation rates.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Ba sediment paleoproductivity Okhotsk Sea opal calcium carbonate last termination glacial ages Ti mass accumulation rate (MAR) |
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