10Be and barium concentrations of sediment core GeoB1008-3

Particle reactive elements are scavenged to a higher degree at ocean margins than in the open ocean due to higher fluxes of biogenic and terrigenous particles. In order to determine the influence of these processes on the depositional fluxes of 10Be and barium we have performed high-resolution measurements on sediment core GeoB1008-3 from the Congo Fan. Because the core is dominated by terrigenous matter supplied by the Congo River, it has a high average mass accumulation rate of 6.5 cm/kyr. Biogenic 10Be and Ba concentrations were calculated from total concentrations by subtracting the terrigenous components of10Be and Ba, which are assumed to be proportional to the flux of Al2O3. The mean Ba/Al weight ratio of the terrigenous component was determined to be 0.0045. The unusualy high terrigenous 10Be concentrations of 9.1 * 10**9 atoms/g Al2O3 are either due to input of particles with high10Be content by the Congo River or due to scavenging of oceanic 10Be by riverine particles. The maxima of biogenic 10Be and Ba concentrations coincide with maxima of the paleoproductivity rates. Time series analysis of the 10Be and of Ba concentration profiles reveals a strong dominance of the precessional period of 24 kyr, which also controls the rates of paleoproductivity in this core. During the maxima of productivity the flux of biogenic Ba is enhanced to a larger extent than that of biogenic 10Be. Applying a model for coastal scavenging, we ascribe the observed higher sensitivity of Ba to biogenic particle fluxes to the fact that the ocean residence time of Ba is approximately 10 times longer than that of 10Be.

(Table 1, page 119) 10Be and 9Be concentrations in manganese nodules of the Pacific Ocean

The usefulness of cosmogenic beryllium-10 (half life = 2.5 Ma) for studying the rates of accumulation of ferromanganese nodules is reported based on its measured depth distribution in the top 20 mm of these deposits. Accumulation rates have been obtained in the range of 1 to 4 mm/Ma, which are in good agreement with rates determined using the 230Th method on the same nodules. The use of 10Be offers promise in extending the dating to the outer few cm of the nodules. This contrasts with conventional methods using 230Th and 231Pa isotopes which, due to their comparatively short half lives, are limited to a few mm at the surface of the nodules. Detailed studies of 10Be in the manganese deposits coupled with other trace element analyses should prove valuable in understanding the processes of formation of these deposits and the chronology of events recorded by them.

东菲律宾海铁锰结壳（核）成因与古海洋环境响应

本文以东菲律宾海沉积物表层新型深水铁锰结壳、铁锰结核及结壳下伏沉积物为研究对象，通过对其显微结构构造、矿物组成、元素组分的分析、元素赋存状态的系统研究、铀系和10Be同位素年代学测试，结合结壳（核）成矿背景和控矿要素分析，研究和恢复了研究区深水铁锰结壳（核）的成因与古海洋环境响应。这一结果填补了深海沉积物表层新型深水铁锰结壳系统研究的空白，深化了对铁锰结壳（核）分布规律、成因和形成过程及其古海洋环境记录作用的认识，充实了海底金属成矿理论，为铁锰结壳（核）的勘探与开采提供了理论基础和支持，同时也为研究区晚中新世以来一直不甚明了的构造演化提供了新的研究载体和资料。 通过研究，得出如下结论：（1）研究区铁锰结壳（核）的成矿背景主要受控于南极底流强弱及物源供给的变化；（2）证实铁锰结壳（核）主要为水成成因，同时其物质组成也受一定程度的火山和陆源物质的影响；结壳（核）自形成以来没有遭受到明显的磷酸盐化等成岩后期改造和元素再迁移，具有重要的古海洋学意义；（3）通过新型铁锰结壳及下伏沉积物元素赋存状态的研究，认为生物作用对研究区结壳的形成并没有很大的直接影响，其物质成分主要来自于结壳中铁锰氧化物（氢氧化物）的吸附作用；（4）在控矿要素的研究中，归纳出了地质与海洋两大类结壳（核）控矿要素；（5）根据结壳成分长周期变化趋势，结合铀系和10Be测年结果，将研究区结壳的形成过程划分为三个主要阶段（5.6~2.8 Ma，2.8~2.7 Ma和2.7 Ma以来），并确定了晚中新世以来研究区南极底流的活动情况、火山和大陆来源（风尘）物质输入量的变化。

东北四海龙湾玛珥湖啊1500年来长链烯酮不饱和度温标与古水温重建

The alkenone unsaturation paleothermometer is an important proxy to reconstruct water temperature, and is widely applied to reconstructing sea surface temperature in most oceanographic settings. Recent research indicates that long chain alkenone is preserved in lacustrine sediments, and the alkenone unsaturation has good relationship with mean annual temperature in studied lakes. Thus, the alkenone unsaturation could be used as a temperature proxy to reconstruct temperature in limnic systems. In this study, we analyzed long chain alkenone from the varved sediments in Lake Sihailongwan, northeastern China. Based on the counting varves, we established time scale during the past 1500 years. The distribution pattern in the sediment is similar with the previous study in lacustrine environment. The ratio of C37:4 methyl ketone to the sum of C37 alkenones is high. Based on the published temperature- alkenone unsaturation equation, we reconstructed the mean air temperature and July water temperature during the past 1500 years. Three major cold periods are in AD560-950, AD 1540-1600 and AD1800-1920. Three major warm periods are AD450-550, AD 950-1400 and AD 1600-1800. The Medieval Warm Period was a significant warm periods. However, the traditional “Little Ice Age” was not a persistent cold period, and interrupted by relative longer warm period. The temperature variations in this study show a general similar pattern with the summer temperature reconstruction from Shihua Cave and the winter temperature from historical documents. The temperature variations from long chain alknone record show a good agreement with solar activity (10Be data from ice core and sunspot number from tree rings). It may suggest that solar activity is most important forcing in the studied area.