济阳坳陷石炭系—二叠系储层成岩作用及孔隙演化

石炭纪—二叠纪海陆交互沉积背景下发育的碎屑岩是济阳坳陷主要的储集岩。薄片、扫描电镜等多种微观分析研究表明,储层成岩作用主要有压实作用、胶结作用、交代作用、溶蚀作用及裂缝形成作用等。依据残留地层叠置样式及埋藏史,结合古地温、有机质热演化参数、黏土矿物转化序列、自生矿物以及成岩事件等多方面研究成果,将储层划分为古最大埋深等于现今埋深、古最大埋深大于现今埋深两种成岩阶段类型,前者处于中成岩B阶段和晚成岩阶段,后者处于中成岩A阶段和B阶段。多期复杂的构造运动导致储层具有多变的成岩环境及复杂的成岩演化序列,并控制了储层的成岩演化史、孔隙演化史及储集性能。     

浅析末次间冰期以来柴达木盆地东南部古气候环境演化

在前人研究的基础上,以柴达木盆地察尔汗地区ZK2钻孔沉积物为研究对象。选取古气候替代指标——色度,分析了察尔汗地区近130kaB．P．以来气候的变化．揭示了该区对全球气候变化的响应模式以及古气候变化在色度指标上的表现。结果表明：末次间冰期以来,察尔汗地区环境由温暖湿润冷暖频繁波动干热环境变化,色度L＊,a＊,b＊具体表现为在不同水平的波动。其中b＊较L＊,a＊能更敏感地反映古环境的变化,在温暖湿润的间冰期,b＊值趋向于高值区间;而在寒冷干燥的冰期,b＊值趋向于低值区间波动。这种整体波动的趋势与氧同位素的5个阶段基本吻合。     

一次暴雨过程天气尺度云系演变特征分析

通过对2005年6月18日至23日造成广西大范围持续性暴雨过程天气尺度云系特征分析,发现暴雨落区与阶段平均云图的TBB≤-60℃区域有很好的对应关系,表明暴雨主要是由中尺度天气系统造成的,利用这些关系可以很有助于做好强降雨的精细化预报。     

龙木错地区泽错岩体演化历史及构造意义:来自地球化学和年代学的约束

沿大型断裂带出露的深成岩体记录并保存了形成时的大地构造活动及后期演化和变形的重要信息。为了更好地理解羌塘西部花岗岩的成因机制和演化历史,本文选取了龙木错断裂南部的泽错岩体进行地球化学、SHRIMP锆石U-Pb年代学及云母和钾长石~(40)Ar/~(39)热年代学分析。全岩地球化学判别图显示花岗岩样品为高钾钙碱性系列至钙碱性系列和过铝质。矿物组合表明无角闪石且含白云母。以上特征均显示出明显的S型花岗岩趋势。锆石U-Pb年龄为123±1. 7Ma至107±1. 4Ma,表明岩浆侵位的时代为早白垩世,此时班公-怒江洋仍在向北俯冲。云母和钾长石~(40)Ar/~(39)年龄及前人低温热年代学数据显示,侵位后岩体至少有四个阶段的冷却,包括120～90Ma、90～38Ma、38～26Ma和26～0Ma。第一阶段在侵位后10Myr内快速冷却至低于～320℃,而随后以相对较慢的速率冷却至～220℃。从90Ma到38Ma期间经历了较长时期极为缓慢的冷却,该阶段构造活动趋于静止,表明羌塘地体-拉萨地体碰撞应发生在90Ma之前。中新世受控于龙木错断裂左旋走滑的影响,最后一期的构造变形以东西向伸展为主,深成岩逐渐剥露至地表。龙木错断裂可能作为中新世以来高原物质向东运移西部边界的一条新的应力释放途径。     

基于RS技术的北江下游河道岸滩演变分析

以1975～2001年共7个时相的遥感影像作为数据源,在GIS支持下采用动态分析方法,对比各个时期北江下游河道岸滩形态及位置变化,结合河道的地质、地貌、水文泥沙、整治工程等信息,分析洲滩消长的原因,获取河道横向演变特性,预测岸滩变化趋势以及整治工程效果.对比该时段内北江下游河道纵向演变情况,得出河道的纵向变形影响横向变形,总体变化两者成反比关系,河势向着稳定的趋势发展.     

热带大气发展运动的低频模式

当热带大气运动的适应过程完成后 ,即进入到缓变的发展运动 ,描写发展运动的模式有Gill的长波近似模式以及作者提出的短波近似模式。文中在分析这两个模式的特点和不足之处后 ,提出了低频近似下的发展模式。如 f0 是热带地区典型的科氏参数值或惯性振荡频率 ,设运动的特征频率为 σ,则长波和短波近似的成立条件之一 ,要求 σ f0 。而低频近似模式要求 σ2 f20 ,即对运动频率的要求比长波或短波近似模式降低一个量级 ,因此适用性更广。     

Evolution and Frontogenesis of an Imbalanced Flow —the Influence of Vapor Distribution and Orographic Forcing

1.InttoductionIftheinitialfieldsarenotingeostrophicbalance,theadjustmentandevolutionwilloccurinthestratifiedfluid,andthefrontogenesiswilloccurundersuitableconditions.ThisaspectwasfirstinvestigatedbyRossby(1938),followedbymanyscientists(Blumen,1972;Gill,1976,1982;VanHeijst,1985;BossandThompson,1985;On,1984,1986;McWilliams,1988;Middleton,1987;Glendening,1993;BlumenandWu,1995;WuandBlumen,1995;Grimshaw1998;Blumen,1998;etc.).Intheseresearches,theenergyconversionratioy=AEk/BE,isaninterestin…     

Volcanic history of El Chichón Volcano (Chiapas, Mexico) during the Holocene, and its impact on human activity

2 abundance and depletion in MgO, CaO, TiO₂, as well as trace and rare earth elements. This suggests segregation of olivine and orthopyroxene from the melt. Since human settlements in southeast Mexico and Central America can be traced as far back as approximately 2500 years BP, most of these events probably affected human activity. In fact, there are reports of pottery shards and other artifacts in deposits from the eruption of 1250 BP. Pottery fragments in deposits of an eruption that took place 2500 BP are also reported in this paper. Thus, the impact of the volcano on human activities has been frequent, with most of the repose intervals lasting between 100 to 600 years. The impact of the eruptions was probably of greater than local extent, because airfall tephra could reach distant sites and possibly even affect weather. The eruptive history of El Chichón also offers clues in the investigation of the Maya civilization. Several researchers have considered the volcano as an important factor in the answer to some intriguing questions such as the extensive use of volcanic ash in Late Classic Maya ceramics or, of greater importance, the causes of the collapse of the Classic Maya civilization. Received : 4 May 1998 / Accepted: 1 November 1999     

热带大气和海洋的半地转适应和发展运动

半地转适应和半地转发展是热带大气和海洋运动的两种基本形态,它们在时间上是可分的,反映了不同的物理过程。当初始扰动作用于大气或海洋时,首先将激发出重力惯性波,当重力惯性波频散后,建立起半地转的平衡状态,此后运动进入到以Rossby波（长波或短波）、Kelvin波和混合波中的Rossby短波为主导的发展状态。文中研究的纬圈半地转适应和发展运动,是Gill长波近似模式的理论基础。同时研究了经圈半地转适应和发展运动,实际上这相当于短波近似模式,它可以应用到研究海洋经圈边界附近的一类问题。     

New data on the zoogeography of Aphanius sophiae (Teleostei: Cyprinodontidae) in the Central Zagros (Southwest Iran)

The clade of the Iranian freshwater Aphanius species from endorheic and exorheic drainage basins contains three subclades, of which the Aphanius sophiae subclade with seven species is the most specious one. Recently, two previously not known populations of Aphanius were discovered in two isolated basins; one in the Arjan Wetland (Helleh subbasin), and the other in the Semirom spring (Karun Basin), both are located in the Central Zagros Mountains (SW Iran). The objective of this study is to investigate their taxonomic status, to elucidate their phylogenetic relationships and to contribute to future conservation strategies and habitat management of the freshwater species of Aphanius in Iran. Methods include analysis of genetic data based on mtDNA (cyt b), combined with meristics, morphometrics, scale sizes (J-indices) and otolith data. The results based on cyt b clearly indicate that two species are present in the Arjan Wetland, one is closely related to A. sophiae (currently thought to be restricted to the Kor Basin), the other represents Aphanius shirini (previously only known from its type locality Paselari spring). However, significant phenotypic differences are not present between these two species. The second population from the Semirom spring is sister to A. sophiae (Kor Basin) according to cyt b data, but differs significantly from this species with regard to the phenotype. The presence of A. shirini in the Arjan Wetland is most likely be explained by man-made introduction because of the recent droughts. The similarity of the two species present in the Arjan Wetland may be due to phenotypic plasticity, but also hybridization could have played a role. The isolation of populations of A. sophiae is discussed in the context of the active geological history and climate change, and it is likely that their divergence happened in the Early or Middle Holocene (c. 11,700–4000 y. ago). The presence of A. sophiae in the Helleh subbasin and Karun Basin extends the currently known zoogeographic range of this species, which previously has only been reported from the Kor Basin. Such knowledge is important for future conservation strategies and habitat management.