北西太平洋における海洋古環境の観測タワーとしての孤立海山の利用とその検証

这项工作的目的是重建末次冰期以来海洋环境的变化。为此，使用位于温带地区(32*，1580*；深度2680英寸)的孤立海山之一的Shaisky隆起顶端附近的活塞取样器获得了一个沉积物岩芯。由北海道大学的奥巴博士测量的氧同位素曲线确定了该岩心的年龄。最深处295 cm处的年龄估计约为260ka B.P.。化学分析表明，碳酸钙、蛋白石二氧化硅和有机碳是生物量变化的代用品，铁、铝、钛、锰、铜、钒、钡和磷是风尘通量的代用品，钍同位素(Th-230和Th-232)是水柱中颗粒降雨率的代用品，铀同位素(U-238和U-234)是氧化还原条件下的代用品。钛和钒在堆芯中含量很少。元素与铝的比例相当恒定。这些发现表明，这些元素与地表水中的生物过程无关。生物碳酸钙、蛋白石二氧化硅和有机碳的含量在暖期相对较高，为120ka B.P.过剩的钍-230也在与冰川后时代相对应的地层中得到了富含。因此，我们可以认为暖期的地表水生物量比冰期的要高得多。

The object of this work is to reconstruct the change of ocean environment after the last glacial age. For this purpose, one sediment core was obtained using a piston corer near the summit of Shaisky Rise, one of isolated sea mounts located in the temperate region (32*, 1580* ; the depth of 2680 in). The age of this core was determined by the oxygen isotope curve measured by Dr. Oba of Hokkaido Univ. The age of the deepest layer, at the depth of 295 cm, was estimated to be ca. 260 ka B.P.The chemical analysis was performed for calcium carbonate, opaline silica and organic carbon as the proxy of the change of biomass production, iron, aluminum, titanium, manganese, copper, vanadium, barium and phosphorus as that of the aeorian dust flux, thorium isotopes (Th-230 and Th-232) as that of particle rain rate in the water column, and uranium isotopes (U-238 and U-234) as that of redox condition in the sedimentary environment.The concentration changes of lithogenic elements as iron, aluminum, titanium and vanadium are little in the core. The elemental ratios to aluminum are fairly constant. These findings show that these elements are not concerned in the biological process in the surface water. The concentrations of biogenic calcium carbonate, opaline silica and organic carbon are relatively high in the warm ages, at 120 ka B.P.and the present time. The excess thorium-230 is also enriched in the layers corresponded to the post-glacial age. Consequently, we can suggest that the surface water biomass production in the warm age is rather higher than in the glacial age.