Biostratigraphic and aminostratigraphic constraints on the age of the Middle Pleistocene glacial succession in north Norfolk,UK

Considerable debate surrounds the age of the Middle Pleistocene glacial succession in East Anglia following some recent stratigraphical reinterpretations. Resolution of the stratigraphy here is important since it not only concerns the glacial history of the region but also has a bearing on our understanding of the earliest human occupation of north‐western Europe. The orthodox consensus that all the tills were emplaced during the Anglian (Marine Isotope Stage (MIS) 12) has recently been challenged by a view assigning each major till to a different glacial stage, before, during and after MIS 12. Between Trimingham and Sidestrand on the north Norfolk coast, datable organic sediments occur immediately below and above the glacial succession. The oldest glacial deposit (Happisburgh Till) directly overlies the ‘Sidestrand Unio‐bed’, here defined as the Sidestrand Hall Member of the Cromer Forest‐bed Formation. Dating of these sediments therefore has a bearing on the maximum age of the glacial sequence. This paper reviews the palaeobotany and describes the faunal assemblages recovered from the Sidestrand Unio‐bed, which accumulated in a fluvial environment in a fully temperate climate with regional deciduous woodland. There are indications from the ostracods for weakly brackish conditions. Significant differences are apparent between the Sidestrand assemblages and those from West Runton, the type site of the Cromerian Stage. These differences do not result from contrasting facies or taphonomy but reflect warmer palaeotemperatures at Sidestrand and a much younger age. This conclusion is suggested by the higher proportion of thermophiles at Sidestrand and the occurrence of a water vole with unrooted molars (Arvicola) rather than its ancestor Mimomys savini with rooted molars. Amino acid racemisation data also indicate that Sidestrand is significantly younger than West Runton. These data further highlight the stratigraphical complexity of the ‘Cromerian Complex’ and support the conventional view that the Happisburgh Till was emplaced during the Anglian rather than the recently advanced view that it dates from MIS 16. Moreover, new evidence from the Trimingham lake bed (Sidestrand Cliff Formation) above the youngest glacial outwash sediments (Briton's Lane Formation) indicates that they also accumulated during a Middle Pleistocene interglacial – probably MIS 11. All of this evidence is consistent with a short chronology placing the glacial deposits within MIS 12, rather than invoking multiple episodes of glaciation envisaged in the ‘new glacial stratigraphy’ during MIS 16, 12, 10 and 6. Copyright © 2009 John Wiley & Sons, Ltd.     

江西永平铜矿区花岗岩热液蚀变与岩石成因:矿物化学、元素地球化学和Sr-Nd-Hf同位素制约

永平铜矿床是位于华南钱塘江-信江断裂坳陷带中的一个大型铜矿床.矿区内出露的岩浆岩主要有似斑状黑云母花岗岩体和少量石英斑岩脉,黑云母花岗岩岩体内及接触带发育斑岩型和矽卡岩型铜钼钨多金属矿化.对岩体中黑云母的电子探针成分分析表明,似斑状黑云母花岗岩中黑云母具有富镁贫铁高钛的特点,Fe/(Fe Mg)为0.21～0.33,TiO2含量为2.12%～4.28%;而石英斑岩脉中黑云母更加富镁贫铁,Fe/(Fe MS)为0.10～0.15,TiO2含量为2.43%～3.86%.黑云母的化学组成表明花岗质岩浆形成时的氧逸度很高,与长江中下游地区其他含铜花岗质岩体相吻合.永平花岗岩体遭受了较强的热液蚀变作用,部分黑云母蚀变为绿泥石.石英斑岩中绿泥石具有富铁贫镁低钛的特征(Fe/(Fe Mg)=0.72～0.76;TiO2=0.02%～0.06%),其形成温度为139～224℃.而似斑状黑云母花岗岩中绿泥石相对贫铁富镁高钛(Fe/(Fe Mg)=0.36～0.44;TiO2=0.05%～0.36%),形成温度稍高,为229～346℃,与该矿床流体包裹体研究获得的成矿温度(220～400℃)基本吻合.Sr-Nd-Hf同位素综合研究表明,永平似斑状黑云母花岗岩具有变化较大且相对较高的εHf(t)值(-0.1～-10.3)和εNd(t)值(-5.83～-7.95),反映岩石具有明显的壳幔混合成因特征.而石英斑岩的εHf(t)值(-8.4～-12.5)和εNd(t)值(-9.93～-10.2)均稍低于似斑状黑云母花岗岩,反映其形成过程中幔源物质贡献相对较小.永平岩体的地壳端元很可能就是该区中元古代基底地层重熔的产物.     

川西前陆盆地中—新生代沉积迁移与构造转换

川西前陆盆地中—新生代各构造层的残余厚度展布和沉积特征分析发现,四川克拉通周缘的前陆盆地在晚三叠世时期发育于龙门山山前,明显属于龙门山褶皱逆冲构造载荷所形成的前渊凹陷;侏罗纪早期的沉积地层呈面状分布,没有表现出显著的挠曲沉降,指示了一个构造相对平静的阶段;中侏罗世早期前渊凹陷迁移至龙门山北段和米仓山山前,前渊沉积从晚三叠世的北东向转换为近东西向,广泛的湖泊相沉积预示了前陆盆地的欠充填状态;中侏罗世中晚期,川西盆地沉降中心又迁移到大巴山山前,相应的挠曲变形又从近东西向转化为北西向,构成了大巴山的前渊凹陷;晚侏罗世—早白垩世时期,沉降中心再次回到米仓山山前,巨厚的前渊凹陷沉积指示了米仓山冲断带的主要活动时期;白垩纪末—古近纪的前渊凹陷则跃迁至雅安—名山地区。川西前陆盆地的同造山沉降中心以四川盆地中心为核心在西部和北部呈弧形迁移,沉积序列不断更替和叠加。中生界各构造层底界构造图显示现今的构造低部位位于川西北地区和川西南地区,在川西北地区均有东西走向的等值线分布,而川西南地区等值线走向则为北东-南西向。因此分析认为,晚侏罗世至早白垩世的构造变形可能控制了川西盆地现今的地层变形,形成了川西北地区的南北向构造挤压结构,而晚期的新生代构造变形则主要体现在川西盆地的西南部,形成北东-南西向的地层展布特征。     

沿海城市海水入侵问题研究

近年来，沿海城市的海水入侵问题逐渐成为人们关心的焦点之一。文章通过资料搜集与整理，对沿海城市的海水入侵状况作了全面描述与分析。系统地总结了海水入侵的若干特点及海水入侵的成因分析与规律，较为详细的分析了海水入侵的基本事实、基本矛盾和各发展阶段的发展原因，在此基础上总结了海水入侵的基本理论。为进一步的研究打下良好的基础。     

冲绳海槽热流机制浅析

冲绳海槽是一个高热流区，平均热流值极高，但不均匀，实测最小值与最大值相差三个数量级以上，结合海槽地区的构造和地球物理特征，探讨了导致这一高而分散热流特征的多种因素。包括异常壳幔结构。海底热液循环以及地下水对流等，并分析了相应的控制机制。     

我国主要育珠贝(蚌)贝壳珍珠层的扫描电子显微镜研究

采用扫描电子显微镜（SEM）对我国海水马氏珍珠贝Pinctada martensi(Dunker），大珠母贝Pinctada maxima(Jameson）、企鹅珍珠贝Pteria penguin(Roeding）和淡水三角帆蚌Hy-riopsis cumingii（Lea）贝壳珍珠层内层面的形貌特征进行了研究，结果表明，4种贝壳珍珠层均呈砖墙式结构，珍珠层中文五笔型小板片呈不规则多边形至六边形，直径为1.3-4.5μm，厚度0.35-0.85μm，同一种类贝壳中文石小板片的形状及粒径均匀一致，反映了生物矿物化的特殊性。珍珠层沿壳内层面与棱柱层过滤带中均存在初始生长的文石小晶体结构排列较混乱的现象，与成熟珍珠层中文石小板片的定向排列结构明显不同。     

中更新世气候转型期南海北部和南部的气候变化差异

选取大洋钻探ODP184航次在南海北部采集的1144站为研究材料,通过分析中更新世0.4～1.4Ma期间506个样品中浮游有孔虫氧、碳稳定同位素的变化特征,并与南海南部ODP 1143站和西太平洋暖池ODP 807站的同位素资料进行比较,发现南海北部的氧、碳稳定同位素及其差值的变化响应中更新世气候转型事件,在中更新世距今约0.9Ma之后100ka的偏心率周期明显增强。在中更新世气候转型之前,南海北部、南海南部和赤道西太平洋都呈现出典型的热带气候特征,具有岁差和半岁差的气候周期;转型之后,随着北半球冰盖的进一步扩张,南海北部受东亚冬季风增强的影响而导致温度下降、温跃层变深,但南海南部与赤道西太平洋的温度变化较小且温跃层变浅,说明同属季风区的南海北部和南部对气候变化的响应有所不同。     

UKF算法及其在GPS卫星轨道短期预报中的应用

分析了GPS卫星预报星历,在比较分析EKF和UKF优缺点的基础上,将UKF引入GPS卫星轨道预报研究中.数值模拟和结果分析表明,UKF方法预报更稳定,能有效地提高轨道预报精度和稳定性.     

Pelagic records from the Equatorial Ninetyeast Ridge and significant environmental events during the past 3.5 Ma

This paper presents pelagic records of planktic foraminifera, as well as data of stable isotope stratigraphy and carbonate stratigraphy since 3.5 Ma B.P. from site ODP758 in the Ninetyeast Ridge of the Indian Ocean. Based on these data, manifestations and related mechanisms of major tectonic and environmental events such as the rapid uplift of the Himalaya Mountains, “middle Pleistocene climatic transition” and “mid-Brunhes dissolution event” in the region are discussed. According to the analysis and comparison of various indices and changes in terms of foraminifera assemblage, paleotemperature, paleosalinity and themocline from site ODP758, the authors deduce that the paleoclimatic changes might correlate with the mid-Pleistocene transition at 1.4–1.7 Ma B.P. The changes of CaCO₃, mass accumulation rates (MAR) of CaCO₃ and non- CaCO₃ MAR indicate that the loaded terrigenous sediments increased at 1.7 Ma, which is in agreement with the uplift history of the Qinghai-Tibet plateau as shown by the available data. The last two changes coincide with the uplift of the Qinghai-Tibet plateau, hence they are called “Qinghai-Tibet movement” (1.7 Ma), and the “Kunlun-Yellow River movement” (1.2–0.6 Ma). The changes of the CaCO₃ content, coarse fraction (> 150 μm) content and planktonic foraminifera biostratigraphy show that strong dissolution of abyssal CaCO₃ occurred in the study region during 0.5–0.4 Ma. The event was consistent with the “mid-Brunhes dissolution event” in the sedimentary records of the Atlantic Ocean, Pacific Ocean, Indian Ocean and Nansha sea area of the South China Sea. __________ Translated from Geological Bulletin of China, 2007, 26(12): 1627–1632 [译自: 地质通报]     

Dynamics of the mid-ocean ridge plate boundary: Recent observations and theory

The global mid-ocean ridge system is one of the most active plate boundaries on the earth and understanding the dynamic processes at this plate boundary is one of the most important problems in geodynamics. In this paper I present recent results of several aspects of mid-ocean ridge studies concerning the dynamics of oceanic lithosphere at these diverging plate boundaries. I show that the observed rift valley to no-rift valley transition (globally due to the increase of spreading rate or locally due to the crustal thickness variations and/or thermal anomalies) can be explained by the strong temperature dependence of the power law rheology of the oceanic lithosphere, and most importantly, by the difference in the rheological behavior of the oceanic crust from the underlying mantle. The effect of this weaker lower crust on ridge dynamics is mainly influenced by spreading rate and crustal thickness variations. The accumulated strain pattern from a recently developed lens model, based on recent seismic observations, was proposed as an appealing mechanism for the observed gabbro layering sequence in the Oman Ophiolite. It is now known that the mid-ocean ridges at all spreading rates are offset into individual spreading segments by both transform and nontransform discontinuities. The tectonics of ridge segmentation are also spreading-rate dependent: the slow-spreading Mid-Atlantic Ridge is characterized by distinct bulls-eye shaped gravity lows, suggesting large along-axis variations in melt production and crustal thickness, whereas the fast-spreading East-Pacific Rise is associated with much smaller along-axis variations. These spreading-rate dependent changes have been attributed to a fundamental differences in ridge segmentation mechanisms and mantle upwelling at mid-ocean ridges: the mantle upwelling may be intrinsically plume-like (3-D) beneath a slow-spreading ridge but more sheet-like (2-D) beneath a fast-spreading ridge.