Trace Element Proxies of Carbon Flux and Bottom Water Oxygen Concentration

[401138]铀在化学还原沉淀物中通过沉淀从海洋中除去。在这里，我们提出了来自南大西洋亚南极的初步结果，表明在冰川时代沉积物中自生U沉积率很高。在现代远洋沉积物中，没有类似的自生铀沉积速率如此之高。观测到的铀埋藏表明，冰川海洋中存在两种条件之一：要么环极深水的氧含量大大降低（与现代水平相比，氧含量超过200微摩尔），要么亚南极表层水的生物生产力大大提高。这两种情况都代表了冰川海洋中碳循环的一个重要特征。我们的假设是，亚南极沉积物保存着关键的记录，这将导致人们长期寻求的对冰期大气中二氧化碳浓度较低的解释。我们的目标不仅是验证这一假设，而且要获得冰河时期海洋生产力和深海氧含量的定量信息。

9401138 ARCHER Uranium is removed from the ocean by precipitation in chemically- reducing sediments. Here, we present preliminary results from the subantarctic South Atlantic showing high rates of authigenic U deposition in glacial-age sediments. There is no analog for such high rates of authigenic U deposition in modern pelagic sediments. The observed burial of uranium implies that one of two conditions existed in the glacial ocean: either greatly-reduced oxygen content of Circumpolar Deep Water (compared to modern levels in excess of 200 micromolar), or greatly-enhanced biological productivity of subantarctic surface waters. Either condition would represent a significant feature of the carbon cycle in the glacial ocean. Our hypothesis is that subantarctic sediments hold the key record which will lead to the long-sought explanation for lower atmospheric CO2 concentrations during the ice ages. Our goals are not only to test this hypothesis, but to derive quantitative information about ice-age ocean productivity and deep- sea O2 content.