加利福尼亚洋流北区早更新世以来似太平洋年代际振荡的微体化石记录

加利福尼亚洋流系统(CCS)是东北太平洋一股十分重要的边界流,在全球海气交换过程中具有重要地位。CCS的海洋-大气变化尤其是涌升流的强弱变化,在年代和多年代时间尺度上的变化主要受太平洋年代际震荡(PDO,20~30年周期)的控制。为了解CCS北区早更新世以来涌升流强弱变化规律及其主要控制机理,本文分析了国际大洋钻探1020B(CCS北区南部41°N)和1245B(北部44°N)钻孔钙质超微化石和硅藻化石等记录。结果显示,多半时间段的记录具有冰期和间冰期旋回的变化;其中超微化石的高含量见于间冰期,而硅藻高含量对应于冰期。这两类化石在沉积物中的含量变化显示出时间尺度长约0.5 Ma的3个阶段:早更新世(1.5~1.1 Ma)两个孔以超微化石含量高为特征;中更新世(1.1~0.65 Ma)两孔中的超微化石和硅藻化石含量相对较高,但它们在两个孔的变化趋势不同;晚更新世(0.65 Ma)以来,南部1020B孔超微化石含量高且出现频率高于硅藻化石,而北部1245B孔以硅藻化石含量较高且持久出现为特征。本文提出了该区涌升流受长周期“似太平洋年代际振荡模式”和“似北太平洋环流振荡模式”控制的假设。早更新世(1.5~1.1 Ma)主要受到持续的似PDO正位相 (似+PDO,表层海水温暖)的控制,涌升流弱,海水中碳酸盐离子丰富,利于颗石藻骨骼钙化形成颗石和颗石产量高,沉积物中超微化石含量高。中更新世过渡期(MPT,1.1~0.65 Ma)受到似PDO负位相(似-PDO,海水表层水体冷、涌升流强、海水pH值低,硅藻生产力高,沉积物中硅藻化石含量高)与似+PDO的交替影响。晚更新世(0.65 Ma)以来,南部1020站位受到似-PDO/似-NPGO?的交替控制,但似-NPGO?的强度和出现频率均大于似-PDO,因此超微化石含量和出现时期比硅藻多;北部1245站位则仅受似-PDO的持续性控制,涌升流较强且持续时间长、沉积物中硅藻化石几乎持续出现且含量较高。MPT时期以硅藻化石含量在1.1 Ma突然增加(南部增加3倍,北部5倍)为起始点,以0.65 Ma时超微化石含量突变(南部增加3倍,北部降3倍)为终止点。本文认为MPT起止点化石含量的突变,是古海洋和气候环境突变的结果,也意味着长时间尺度的似PDO的正负位相之间的转换变化可能是突变过程。MPT时期CCS北部区域内出现了南部和北部站位硅质和钙质两类化石含量变化趋势相反的记录,指示着这一时期该区的古海洋和气候条件出现了地理上的南北分异,并且自0.65 Ma以来南北两个站位控制模式不同。本文的这些记录为CCS区现代海洋-大气过程和生物地理分区大致以40°N为界的研究提供了早更新世以来的历史记录。     

简论21世纪初美国中东战略中的美国-伊朗关系

美国对伊朗战略是美国中东战略的重要组成部分。伊朗的政治、经济、社会体制的变化将引起中东政治格局的重大变化。9.11事件以后,美国中东战略的焦点转变为“反恐”:军事上以打击恐怖主义组织和活动、占领中东的战略要地为目标,在中东大力传播美国的“民主、人权”意识,在重建伊拉克、阿富汗、推进中东和平路线图的口号下“改造中东”,经济上控制中东的石油天然气资源,扩张美国在中东的市场,实施“美国-中东自由贸易区”构想,弱化中东和平进程的意义,千方百计使美国的国家利益最大化。美国-伊朗关系,始终围绕着两国国家利益这一核心展开。本文简略地分析了21世纪初期以来美国-伊朗关系的特征及其变化、影响当今美国-伊朗关系的重大障碍,预测了美国的伊朗政策走势,结论是:21世纪初期美国-伊朗关系根本改善的可能性不大。     

雅鲁藏布江中游沙地植物区系与阿拉善荒漠植物区系的比较

从区系地理成分来看,雅鲁藏布江中游沙地植物区系以东亚成分(中国-喜马拉雅成分)占绝对优势,而阿拉善荒漠则以亚洲中部荒漠成分(即戈壁成分)占主导地位。另外,两个地区的地方特有成分的优势都十分明显,但雅鲁藏布江中游沙地中的特有种大都是在青藏高原隆起以后由于特殊的生境(高寒、干旱)而分化出来的新种,而阿拉善荒漠中的特有种大都是些古老的单种属和寡种属。雅鲁藏布江中游沙地植物区系和阿拉善荒漠植物区系都具有古老的热带起源,然而前者是在古老的第三纪热带植物区系的基础上,在高原隆升过程中经过山区特化和气候特化形成的新的年轻的区系,而后者则较多地保留了热带起源特别是古地中海起源的古老性。     

大兴安岭下嘎来奥伊铅锌矿床钾长花岗岩的岩石成因及地质意义

下嘎来奥伊铅锌矿床位于黑龙江省西北部,大地构造位于额尔古纳地块额木尔山隆起带南缘与大兴安岭火山岩带北缘接合部位的西段。研究区广泛分布大面积不同期次侵入岩,矿体产于中酸性浅成侵入岩及其与大理岩接触带——矽卡岩带中。LA-ICP-MS锆石U-Pb定年结果表明,下嘎来奥伊钾长花岗岩成岩年龄为（168.9±2.1）、（165.9±2.1） Ma,认为其成矿时代为中侏罗世。元素地球化学测试结果显示,下嘎来奥伊钾长花岗岩属于准铝质-弱过铝质碱性系列;岩石具有高Si、K、碱和贫Al质量分数的特征;A/CNK值为0.97~1.02;锆石饱和温度介于760~851℃之间,平均温度为811℃,具A型花岗岩特征;稀土元素特征表现为轻稀土富集、重稀土相对亏损,富集大离子亲石元素（Rb、K）和高场强元素（Th、U、Zr、Hf）,亏损高场强元素（P、Ti、Nb、Ta）,具Eu负异常（δEu值为0.01~0.27）。下嘎来奥伊钾长花岗岩w（Sr）=（13.20~62.80）×10^-6,平均值为38.95×10^-6,w（Yb）=（2.44~7.81）×10^-6,平均值为4.50×10^-6,属于低Sr高Yb质量分数型花岗岩。结合区域大地构造背景及相关研究认为,矿区钾长花岗岩的形成与中侏罗世蒙古—鄂霍茨克洋闭合所形成的伸展环境密切相关。     

哀牢山-大象山变质杂岩带中斜长角闪岩的地球化学、同位素年代学及其地质意义

哀牢山-大象山变质杂岩带位于青藏高原东南缘,是西南三江地区重要的北西向造山带。杂岩带主要由各种类型的副片麻岩、片岩、石英岩、大理岩和斜长角闪岩构成,岩石发生强烈的糜棱岩化。本文在哀牢山变质杂岩带东南段元江和金平地区以及大象变质杂岩带北段老街和Pho Rang地区发现了中二叠-早三叠世的斜长角闪岩。岩石地球化学和锆石U-Pb年龄研究表明,这些斜长角闪岩可分为4组：第1组为元江斜长角闪岩,具有类似于E-MORB的稀土和微量元素配分曲线特征,锆石U-Pb定年显示其原岩形成年龄为272.5±1.7Ma;第2组为勐桥-马鞍底斜长角闪岩,相比于元江斜长角闪岩（第1组）具有更高的轻/重稀土分馏程度,其稀土和微量元素配分曲线类似于E-MORB,微量元素比值（Nb/Yb、Th/Yb等）显示具有沿MORB-OIB序列演化的趋势,勐桥和马鞍底斜长角闪岩中的Ti含量和Ti/Y比值等特征分别类似于峨眉山低Ti玄武岩和高Ti玄武岩。锆石U-Pb定年结果表明,勐桥-马鞍底斜长角闪岩形成于265.2±1.0Ma~266.2±1.0Ma和250.4±1.5Ma~248.7±1.6Ma,其中晚期岩石中含有261.2±1.5Ma~257.9±1.6Ma的继承锆石,该年龄与峨眉山玄武岩（约260Ma）近于同期。上述证据表明勐桥-马鞍底斜长角闪岩岩浆演化过程中可能混染了部分具有OIB属性的峨眉山地幔柱物质成分;第3组为大象山老街-Pho Rang斜长角闪岩,具有类似于OIB的稀土和微量元素配分曲线特征,微量元素含量和比值（TiO₂=3.28%~4.31%,Nb/La=0.84~1.01,Ti/Y>500等）特征显示与峨眉山高Ti玄武岩相似的地球化学属性,表明峨眉山玄武岩在哀牢山-大象山变质杂岩带内广泛分布,该岩石成分可能为勐桥-马鞍底斜长角闪岩（第2组）的端元组分之一;第4组为大象山Pho Rang斜长角闪岩,该组岩石具有与元江斜长角闪岩（第1组）相似的E-MORB属性特征。进一步的研究表明,哀牢山-大象山变质杂岩带中具有类似于E-MORB属性的斜长角闪岩均表现出不同程度的Nb、Ta元素亏损和Rb、Ba等大离子元素富集,微量元素比值（Nb/Yb（0.72~5.29）,Th/Yb（0.11~0.87）,La/Nb（0.91~8.83））等特征类似于岛弧玄武岩,这些特征指示其原岩岩浆可能是俯冲环境下地幔楔岩石部分熔融的产物。结合哀牢山-大象山变质杂岩带、哀牢山-马江缝合带以及扬子地块之间的时-空关系,本文推测哀牢山-大象山变质杂岩带内的E-MORB类型岩浆岩形成于东古特提斯支洋（即哀牢山-马江洋）向东的俯冲过程,其俯冲持续时间为中二叠-早三叠世（272~248Ma）。     

龙门山北段构造变形及演化历史

5．12汶川8级大地震表明龙门山断裂带仍然是一个构造活动带,为了达到防震减灾的目的．对其进行深入研究是很有必要的。通过龙门山北段毛坝一竹园坝实测构造地质剖面．分析野外实测构造的变形特征．根据变形强弱差异,将毛坝一竹同坝之问分为4个构造变形带,并总结各个构造带的变形特征以及变形序列。在野外研究基础上．首次提出竹园坝断裂．并指出竹园坝断裂是龙门山前山带的主干断裂之一,是喜马拉雅山运动的直接结果。最后．再结合前人资料讨论龙门山北段的构造演化。     

Midlatitude mesopause region winds and waves and comparison with stratospheric variability

We present time series of January–May mean mesosphere/lower thermosphere (MLT) mean winds and planetary wave (PW) proxies over Europe together with stratospheric stationary planetary waves (SPW) at 50°N and time series of European ozone laminae occurrence. The MLT winds are connected with stratospheric PW and laminae at time scales of several years to decades. There is a tendency for increased wave activity after 1990, together with more ozone laminae and stronger MLT zonal winds. However, possible coupling processes are not straightforward. While mean MLT winds before the 1990s show similar interannual variations than stratospheric PW at 100 hPa, later a tendency towards a connection of the MLT with the middle stratosphere SPW is registered. There is also a tendency for a change in the correlation between lower and middle stratosphere SPW, indicating that coupling processes involving the European middle atmosphere from the lower stratosphere to the mesopause region have changed.     

A report on long-term trends and variabilities in middle atmospheric temperature over Gadanki (13.5°N, 79.2°E)

The present study reports long-term variabilities and trends in the middle atmospheric temperature (March 1998–2008) derived from Rayleigh backscattered signals received by the Nd:YAG lidar system at Gadanki (13.5°N, 79.2°E). The monthly mean temperature compositely averaged for the years 1998–2008 shows maximum temperature of 270 K in the months of March–April and September at altitudes between 45 and 55 km. The altitude profile of trend coefficients estimated from the 10 years of temperature observations using regression analysis shows that there exists cooling at the rate with 1σ uncertainty of 0.12±0.1 K/year in the lower stratospheric altitudes (35–42 km) and 0.2±0.08 K/year at altitudes near 55–60 km. The trend is nearly zero (no significant cooling or warming) at altitudes 40–55 km. The regression analysis reveals the significant ENSO response in the lower stratosphere (1 K/SOI) and also in mesosphere (0.6 K/SOI). The solar cycle response shows negative maxima of 1.5 K/100F10.7 units at altitudes 36 km, 41 km and 1 K/100F10.7 units at 57 km. The response is positive at mesospheric altitude near 67 km (1.3 K/100F10.7 units). The amplitudes and phases of semiannual, annual and quasi-biennial oscillations are estimated using least squares method. The semiannual oscillation shows larger amplitudes at altitudes near 35, 45, 62 and 74 km whereas the annual oscillation peaks at 70 km. The quasi-biennial oscillations show larger amplitudes below 35 km and above 70 km. The phase profiles of semiannual and annual oscillations show downward propagation.     

Desert pavement development and landscape stability on the Eastern Libyan Plateau, Egypt

Desert pavement surfaces of the eastern Libyan Plateau in central Egypt represent a stable landscape preserving Middle and Upper Paleolithic artifacts. Detailed measurements of pavement clasts indicate significant variability in clast size, density, lithology and orientation between pavements, but no spatial relationship among any of these pavement variables over the study area. Pavement characteristics are unrelated to local geomorphic features including slope gradient and aspect, suggesting a desert pavement surface that has developed without significant influence from transporting mechanisms such as overland flow and slope failure. Meridional vertical cracks in surface clasts implicate thermal stresses due to diurnal solar variation as a mechanical weathering process, whereas the presence of a clast-free silty layer within all soil profiles indicates that these are accretionary pavement surfaces that have grown upward over time. The desert pavement in this region has likely developed in situ through mechanical breakdown of surface clasts and desert pedogenesis, indicating long-term stability for this region and minimal taphonomic effects on artifacts > 2 cm in diameter deposited on this surface over the last ca. 100 ka.     

A New Ichnogenus Kailidiscus Produced by Attachment from the Middle Cambrian Kaili Formation in Taijiang, Guizhou Province, China

Over 190 specimens of an attachment ichnofossil Kailidiscus （n. ichnogen.） have been found in the Kaili Bitoa, a Burgess Shale-type biota, from the middle Kaili Formation （early Middle Cambrian） in Taijiang County, Guizhou Province, southern China. Kailidiscus is an epichnia with a circular to oval attachment platform, on which there is a carbonaceous film probably formed by the body of the living organism. Structures such as a marginal furrow, an inner and outer marginal ride, many convex fold-ridges, and a large caved peripheral furrow on the attachment platform may be the result of basal tissues of a sessile organism that wrinkled to increase the attachment＇s surface area. The Kailidiscus organism may have been a sessile cnidarian attached to the muddy seafioor. Kailidiscus organisms lived in relatively quiet water, and were buried by a sudden influx of sediment.