Radiolarian record to paleoecological environment change events over the past 1.2 MaBP in the southern South China Sea

This note studies the Radiolarian fossil groups since 1.2 MaBP in ODP leg 184 site 1143, the southern South China Sea (SCS). The result shows that radiolarian abundance experienced a significant variation: before 0.9 MaBP it remained at the extremely low level, but increased with low extent between 0.9–0.65 Ma, which corresponded to the Mid-Pleistocene Transition stage, and it increased rapidly after 0.65 MaBP. During the whole process, the average abundance became higher and higher in each stage, and showed regularly periodic fluctuations. The obvious increase after 0.65 MaBP is inferred to result from the enhanced upwelling in this region, which was induced by the intensified monsoon circulation after the “Mid-Pleistocene Transition”. An outstanding result of the spectral analyses is that a long oscillation of ∼ 0.2 Ma cycle was found in the records of radiolarian abundance and complex diversity, which corresponds well to the result of other paleoceanographic indexes. This probably indicated a special cycle characteristic of paleoecological environment evolution in this area. In addition, all of the radiolarian indexes show an obvious boundary in about 0.47 MaBP, indicating the abrupt variation of the community structure and radiolarian abundance level before and after 0.47 MaBP. So we suppose that there existed a distinct change event of oceanic ecology environment during that period.     

The genesis and environmental significance of red and black sedimentary interlayers in coral reef of well Nanyong 2

The results of paleogeomagnetics and geochemistry of the coral reef in well Nanyong 2 of Nansha Islands showed that the bottom of the black sedimentary interlayer corresponds to the conversion boundary line between Brunhes Postive Polarity and Matuyama Reversed Polarity (B/M) and the cold/warm (19/20) climatic conversion bounds on δ¹⁸O curve, 0.78 Ma ago; and the red sedimentary interlayer corresponds to the ReunionⅠpolarity excursion (reversion) of the geomagnetic field, 2.01—2.04 Ma ago. Comparing with the normal light-coloured coral reef rock, the magnetic susceptibility (c), residual magnetization intensity (Mr) and the content of MnO and Fe₂O₃ of the black sedimentary layer appeared obviously positive abnormity. The magnetic susceptibility (c), residual magnetization intensity (Mr) and the content of Fe₂O₃ of the red sedimentary layer also appeared positive abnormity. Combining with the analyzing results of paleontology, we hold that this pair of special and typical sedimentary interlayers was relative to the sudden change of paleoclimate, i.e. the global climatic change and its incidental polarity reversal of the geomagnetic field directly affected the living environment of the paleontological species as well as the dispersion and enrichment of some chemical elements, especially the elements sensitive to redox such as Fe and Mn. For example, the elements Fe and Mn concentrated in the glacial period would be largely oxidized and diluted when the climate warmed up suddenly, and the originally oxidized high valence Fe would be condensed again when the climate cooled suddenly. This is possibly one of the important reasons of appearing and disappearing of the red and black sedimentary events of coral reef in well Nanyong 2.     

Evolution of the South China Sea and monsoon history revealed in deep-sea records

As the third summary report of ODP Leg 184 to the South China Sea (SCS), this paper discusses the evolution of the East Asian monsoon and the SCS basin. A multi-proxy approach, involving geochemistry, micropale-ontology, pollen and other analyses, was adopted for reconstructing the evolutionary history of the East Asian monsoon, which was characterized by a series of paleo-climate events especially at 8, 3.2, 2.2 and 0.4 Ma. The new record indicates similar stages in the development of the East and South Asian monsoons, with an enhanced winter monsoon over East Asia being the major difference. The rich spectrums of monsoon variability from the southern SCS also reveal other characteristic features of the low latitude ocean. Evidence for the evolution of the SCS includes the hemipelagic Oligocene sediments, implying the existence of deep water environments during the early seafloor spreading stage of the SCS basin. The four major unconformities and some remarkabl ediagenetic features in upper Oligocene deposits indicate the strongest tectonic events in the region. From a careful comparison of lithologies and sedimentation rates, we conclude that the prominent differences in sedimentary environments between the southern and northern SCS were established only by ～3 Ma.     

Original component of grain size index in core sediment from southwestern slope of the South China Sea and its paleoenvironmental implication

Traditional grain size analysis was basically used to discriminate sediment type based on its particle dimension for sedimentary naming[1,2] and to analyze the dynamic feature of transport medium, including water current and wind strength[3―5]. Recently, some patency advances havebeen made by using different methods to separate different grain sizes in various original composition from sediments for searching a new way of paleoenvironmental study[6―8]. Grain size analysis is even playing an …     

从陆架泥质沉积中寻找高分辨率的全新世东亚季风记录

当前对全新世东亚季风的研究,一是重造了不同地区的季风气候与环境特点,分析、划分了不同的阶段并总结了各阶段的特点;二是通过高分辨率的气候代用指标进一步开展定量古气候研究,揭示其变化与周期,探讨其驱动机制.已有的研究主要来自陆地,而利用海洋沉积物研究季风则集中在深海;且主要体现的是气候整体变化特征或侧重于夏季风,而专门论述全新世东亚冬季风的报道则较少;尚未在短时间尺度上有效地确定全新世东亚冬、夏季风的关系及其驱动机制.该文指出,可以利用中国边缘海陆架泥质沉积开展全新世高分辨率的东亚古季风研究,其粒度和Rb/Sr比值等元素地球化学指标可分别作为高分辨率的东亚冬、夏季风演化的替代性指标.     

Radiolarian transfer function for paleo-primary productivity in the South China Sea

Basic data of radiolarian group and primary productivity were from 46 investigation stations of the South China Sea. The factor analysis of principal component and the least squares estimation in both linear regression and nonlinear estimation were applied to establishing the radiolarian transfer function for paleo-primary productivity in this sea area. The results show that the transfer function of nonlinear regression analysis for the radiolarian assemblage and primary productivity has much better parameters. Factors analysis has accumulating variance of 83.6% and communalities of more than 0.940347. Nonlinear regression analysis gives multiple correlation coefficient as 0.84888 and explained variance as 72.059%. The equation of transfer function is with an average estimated error of about 53.778 mg · C/m² · d, which is 14.69% in average observed values. Calculation accuracy is 85.31% for the system of transfer function.     

Simulation study of discharge processes in thunderstorm

The discharge characteristics in thunderstorm have been calculated by using a numerical cloud model. The results indicate that discharge processes occur when simulated thunderstorm developed at the stage of 30-45 min and initial locations of discharge mainly distributes between 4.4-4.8 km and 6.4-6.8 km above the ground (corresponding to ambient temperature of - 10℃ and -25℃. In simulated thunderstorm with a tripole electric structure, 10% of discharges occur between upper positive charge area and middle negative charge area and propagate upwards (from middle negative charge area to upper positive charge area); while, 90% of discharges occur between lower positive charge area and middle negative charge area and propagate downwards (from negative charge area to lower positive charge area). There is a positive correlation between updraft and discharge. The occurrence of discharge process needs hydrometer with a specified concentration and size in cloud (corresponding to ≥ 5 mm/h for precipitation on the ground). The maximum value of precipitation lags the peak of discharge number by a period of about several minutes. The discharge and its variation in thunderstorm are an important factor for monitoring and forecasting thunderstorm.     

中小型办公室网络的Internet／Intranet解决方案

本文阐述了关于用Linux组建中小型网络的方法,用一台或几台计算机组成服务器,达到低成本高效率的要求,可完成WWW、FTP、MAIL、DATABASE以及和Windows98相连的SMB的服务。     

雹暴云发展演变规律的回波特征参量和结构模型

介绍了用平凉地区观测到的大量强对流雷暴云回波资料,分析研究了雹暴云发展演变过程各回波的特征参量随反射率强度的变化和结构模型,及不同冰雹云回波云高与环境温度的关系。