正压准平衡海洋模型及其解Ⅱ:中纬度自由涡旋波动

本文研究了正压准平衡海洋模型中的自由涡旋波.得到的主要结论有:该模型中的解为波包,其载频都是西传的.在仅考虑大洋西海岸时其载频频率是连续谱;而同时考虑大洋东、西海岸时则其为离散谱;且均有其载频频率越高(周期越短)其水平尺度越大的特点,对过分低频的波动,则会使准平衡的假定不再适用.模型中波包载频的周期约在26 d至24 ...     

重庆合川自流井组植物化石的发现

描述了发现于合川自流井组东岳庙段的三种似木贼植物化石,即Equisetites flus Harris,E．1ateralis(Phillips)和E．columnaris(Brongn．)Phillips。标本保存良好,依据植物和双壳类化石的分布关系,提出自流井组东岳庙段的时代为早侏罗世晚期至中侏罗世早期。同时,分析了东岳庙段的岩相特征和沉积环境。     

"拉美现象"的特点、成因及其对我国的启示

纵观当代发展中国家的发展历程,拉丁美洲是较早摆脱殖民统治并着力发展民族经济的区域。近20多年来,拉美各国经济虽有一定增长,人均GDP也并不低,但贫富差距过于悬殊,失业率居高不下,经济危机迭起,社会动荡不安,形成独特的“拉美现象”。本文分析了“拉美现象”的特点及其形成的原因,并探讨了“拉美现象”对我国经济社会发展的启示。     

甘肃兰州海石湾中侏罗世Coniopteris nikaensis的大化石及原位孢子特征

本文对采集于甘肃省兰州市海石湾镇中侏罗统窑街组的一块真蕨类化石进行了系统描述。当前标本最显著的特征是,小羽片分裂2～3次,相邻羽片相互接触或略叠覆,同时保留有完整的实羽叶,通过与前人已报道的蕨叶、叶脉、羽片、小羽片分裂的程度及裂片形状等特征的对比分析,发现其与Coniopteris nikaensis的基本特征完全符合,可明确该化石植物为C.nikaensis,属于窑街盆地的首次报道。经过实验分析,揭示了C.nikaensis的原位孢子基本特征：孢子三缝,赤道轮廓亚三角形,三边微凹,顶角钝圆,直径平均约35 μm;射线较窄且平直,具微弱发育的唇,长度约为孢子体半径的3/4或更长;外壁薄,表面光滑。本研究为完善窑街盆地古植物群面貌提供了新材料,窑街盆地和宝积山盆地相较伊犁盆地更适宜Coniopteris的生长。     

ODP与冲绳海槽海底热水活动研究

本文简要介绍了ＯＤＰ与海底热水活动研究，冲绳海槽中部现代海底热水活动区热水活动研究简况及其热水活动特征；就冲绳海槽中部热水活动研究中存在的问题与ＯＤＰ在冲绳海槽热水区钻探的科学目标进行了讨论。     

High-resolution sediment echosounding off Peru: Late Quaternary depositional sequences and sedimentary structures of a current-dominated shelf

About 6000 km of both bathymetric and high-resolution acoustic profiles were acquired on the shelf and upper slope offshore Peru between 9° S and 14° S. Two new sediment echosounder systems – SEL-96 and SES-2000DS – provided details of the sedimentary structures of the Quaternary sequences within the Sechura-Salaverry, Huacho and Pisco Basins. To a great extent, the poleward undercurrent determines the distribution of sediments. The undercurrent has generated numerous erosional unconformities, it has winnowed hardgrounds and has created mudwaves common between 250 m and 400 m water depth. Distinct subbottom reflectors within sedimentary units represent hiatuses due to periods of intensified winnowing or non-deposition. Erosional unconformities usually marked by pronounced reflectors suggest shifts of the undercurrent system related to climatic changes and eustatic variations of sea level. On a larger scale, the stacked prograding depositional sequences reflect the sea-level cycles of the Middle Pleistocene to the Holocene. Based on the stratigraphy of our piston cores and that of Ocean Drilling Program (ODP) Site 680, the depositional sequences limited by extended unconformities were assigned to oxygen isotope stages 1 to 7. Other sedimentary structures are small straight channels that were conduits for downslope sediment transport. Deformed sediments associated with synsedimentary normal faults result from creep movements indicating beginning slope failure.     

A depocenter of organic matter at 7800 m depth in the SE Pacific Ocean

The Atacama trench, the deepest ecosystem of the southern Pacific Ocean (ca. 8000 m depth) was investigated during the Atacama Trench International Expedition. Sediments, collected at three bathyal stations (1040–1355 m depth) and at a hadal site (7800 m) were analyzed for organic matter quantity and biochemical composition (in terms of phytopigments, proteins, carbohydrates and lipids), bacterial abundance, biomass and carbon production and extracellular enzymatic activities. Functional chlorophyll-a (18.0±0.10 mg m⁻²), phytodetritus (322.2 mg m⁻²) and labile organic carbon (16.9±4.3 g C m⁻²) deposited on surface sediments at hadal depth (7800 m) reached concentrations similar to those encountered in highly productive shallow coastal areas. High values of bacterial C production and aminopeptidase activity were also measured (at in situ temperature and 1 atm). The chemical analyses of the Atacama hadal sediments indicate that this trench behaves as a deep oceanic trap for organic material. We hypothesize that, despite the extreme physical conditions, benthic microbial processes might be accelerated as a result of the organic enrichment.     

泥河湾盆地吉家庄遗址地层易溶盐沉积记录的古气候信息

泥河湾盆地发育晚新生代河湖相沉积并记录了华北更新世人类活动历史。近年来的发现表明,作为盆地重要组成部分,蔚县盆地是解读中更新世古人类行为演化与环境适应的关键区域。吉家庄遗址地处蔚县盆地东部吉家庄-黄梅台地古人类活动集中区,是近年来新发现和发掘的中更新世古人类活动遗址之一。对遗址湖滨相沉积物易溶盐的测试和分析表明,此剖面代表的泥河湾古湖易溶盐为HCO3－-SO42－-Na＋型,pH值平均为8.93,偏碱性;剖面平均含盐量为0.67‰,属于半咸水湖,指示半干旱区湖泊演化由碳酸盐湖向硫化物湖过渡阶段。SO42－、Cl－、Na＋、Ca2＋和Mg2＋等5类离子的变化曲线与剖面沉积物易溶盐总含量变化大体一致。依据易溶盐主要离子比值和碳酸盐碳、氧稳定同位素含量,并结合沉积物特点将湖泊气候演化划分为4个阶段,记录了气候由相对冷湿→凉干→相对温暖湿润的变化过程,古人类在该遗址活动时期对应于湖泊演化的第2阶段早期,处在古湖水位降低且气候向干凉转变的湖滨环境。该项研究对探讨泥河湾古湖的演化以及蔚县盆地吉家庄遗址利用者的生存行为与气候关系具有重要意义。     

Geochemistry and environment evolution of Core E in the Laizhou Bay since last stage of Middle Pleistocene

IwrincrIONOn the evolution of palcoenvironment, salt-water encroachmnt and the distributionof subsurface brine in the LaizhOu Bay area, many researches had been carried out, and muchknowledge abeut the gcolOgical features in this area since Late QUaternary was aCquired' ) (H8nand Wu, l992; Han and Meng, l994; Wen et al. l989). However there was IittIe studyon the sediment geOChemical characteristics since Quaternary. In this Paper, the element strati-graphic characteristics and evolut…