A study on the nonlinear stability of fronts in the ocean on a sloping continental shelf

1.IntroductionArnol'd(1965,1969)variationalprincipleandapriorestimatemethodisessentiallyageneralizationofLyapunovstabilitymethodforfinite--dimensionaldynamicalsystemsininfinite--dimensionalones,andhestudiedthenonlinearstabilityof2--dimensionalincompressibleidealfluidmotionbyuseofthismethod,andestablishedtwotheoremswhichareArnol,d'sfirsttheoremandArnol'd'ssecondtheorem.Eversincethe1980's,manyscientistshavebeenworkingonthissubject,Holmetal.(1985);MclntyreandShepherd(1987);Zeng(1989);Muetal.(1…     

Fish Remains from Homestead Cave and Lake Levels of the Past 13,000 Years in the Bonneville Basin

A late Quaternary ichthyofauna from Homestead Cave, Utah, provides a new source of information on lake history in the Bonneville basin. The fish, represented by 11 freshwater species, were accumulated between 11,200 and 1000 ¹⁴C yr B.P. by scavenging owls. The ⁸⁷Sr/⁸⁶Sr ratio of Lake Bonneville varied with its elevation; ⁸⁷Sr/⁸⁶Sr values of fish from the lowest stratum of the cave suggest they grew in a lake near the terminal Pleistocene Gilbert shoreline. In the lowest deposits, a decrease in fish size and an increase in species tolerant of higher salinities or temperatures suggest multiple die-offs associated with declining lake levels. An initial, catastrophic, post-Provo die-off occurred at 11,300–11,200 ¹⁴C yr B.P. and was followed by at least one rebound or recolonization of fish populations, but fish were gone from Lake Bonneville sometime before 10,400 ¹⁴C yr B.P. This evidence is inconsistent with previous inferences of a near desiccation of Lake Bonneville between 13,000 and 12,000 ¹⁴C yr B.P. Peaks in Gila atraria frequencies in the upper strata suggest the Great Salt Lake had highstands at 3400 and 1000 ¹⁴C yr B.P.     

中亚独联体五国铀成矿的大地构造背景

中亚独联体五国 :哈萨克斯坦、乌兹别克斯坦、吉尔吉斯坦、土库曼斯坦和塔吉克斯坦的中亚大陆地壳构造单元 ,其中分布着大批砂岩型铀矿床和碱交代岩型、含铀煤岩型、含鱼残骸泥岩型和碳酸盐岩型铀矿床 ,计百余个。这些矿床的铀储量约占全球总工业铀储量的30 %。文中划分出8个铀矿域 ,编制了各铀矿域的成矿大地构造剖面 ,并进行了对比研究 ;对上述五种主要铀矿床类型的成矿学特征作了概述 ;归纳出四种铀成矿大地构造模式 ,指出除地台型模式外 ,其余的地槽 +地洼型、地台 +地洼型、地洼型等三种模式均与地洼阶段的构造—岩浆活化作用密切相关 ,甚至是形成工业铀矿床最至关重要的背景因素。文中最后还对中亚型和华夏型地洼铀成矿学的异同特点 ,作了对比分析。     

Integrated surface–groundwater flow modeling: A free-surface overland flow boundary condition in a parallel groundwater flow model

Interactions between surface and groundwater are a key component of the hydrologic budget on the watershed scale. Models that honor these interactions are commonly based on the conductance concept that presumes a distinct interface at the land surface, separating the surface from the subsurface domain. These types of models link the subsurface and surface domains via an exchange flux that depends upon the magnitude and direction of the hydraulic gradient across the interface and a proportionality constant (a measure of the hydraulic connectivity). Because experimental evidence of such a distinct interface is often lacking in field systems, there is a need for a more general coupled modeling approach.     

A field study of the coupled effects of aquifer stratification,fluid density,and groundwater fluctuations on dispersivity assessments

A number of experimental studies have tackled the issue of solute transport parameter assessments either in the laboratory or in the field. But yet, the behavior of a plume in the field under density driven forces, is not well known due to possible development of instabilities. Some field tracer tests on the fate of plumes denser than native groundwater such as those encountered under waste disposal facilities, have pointed out the processes of sinking and splitting at the early stage of migration. The process of dispersion was widely investigated, but the range of dispersivity values obtained from either experimental tests, or numerical and theoretical calculations is still very large, even for the same type of aquifers. These discrepancies were considered to be essentially caused by soil heterogeneities and scale effects. In the meantime, studies on the influence of sinking and fingering have remained more scarce. The objective of the work is to analyze how transport parameters such as dispersivities can be affected by unstable conditions, which lead to plume sinking and fingering. A series of tracer tests were carried out to study under natural conditions, the transport of a dense chloride solution injected in a shallow two-layered aquifer. Two types of experiments were performed: in the first type, source injection was such that the plume could travel downward from one layer to the other of higher pore velocity, and in the second one, the migration took place only in the faster layer. The results suggest some new insights in the processes occurring at the early stages of a dense plume migration moving in a stratified aquifer under groundwater fluctuations, which can be summarized through the following points: (i) Above a stability criterion threshold, a fingering process and a multi modal plume transport take place, but local dispersivities can be cautiously derived, using breakthrough curves matching. (ii) When water table is subject to some cycling or rising, the plume can be significantly distorted in the transverse direction, leading to unusual values of the ratio between longitudinal and transverse dispersivities. (iii) Under stable conditions, for example in the case of straightforward injection in the faster aquifer layer, longitudinal dispersivity is greater than the transverse component as usually encountered, and the obtained transport parameters are closed to macro dispersivity values, which reach their asymptotic limit at very short distances. (iv) The classical scale effect about the varying dispersivity at short distances could be a process mainly due to the distance required for a plume stabilization.     

陆相坳陷盆地层序地层格架下岩性地层圈闭/油藏类型与分布规律——以松辽盆地白垩系泉头组—嫩江组为例

本文在圈闭组成和形成条件分析的基础上对坳陷盆地层序地层格架下岩性地层圈闭/油藏类型与分布规律进行了初步分析和总结,探讨了层序地层格架下不同体系域中圈闭/油藏类型的纵向分布、盆地中不同构造部位圈闭/油藏类型的横向分布规律。系统解剖了松辽坳陷盆地白垩系二级层序格架内低位、湖侵和高位体系域中圈闭/油藏类型的纵向分布和变化特征;对比分析了坳陷盆地从凹陷带(近凹中心)、过渡带(凹陷边缘)到斜坡带(环凹斜坡)圈闭/油藏类型的横向分布和变化规律。圈闭/油藏类型的纵、横向分布和变化规律表明:岩性地层圈闭/油藏的形成及类型具有纵向“层控”、横向“相控”的规律性,即纵向上受控于层序格架(体系域),横向上受控于一定构造背景下特定的沉积相带。     

Rare and vulnerable species in the mollusc communities in the mining subsidence reservoirs of an industrial area (The Katowicka Upland, Upper Silesia, Southern Poland)

Pollution of the water environment by mining waters is a problem not only in Poland, but worldwide. This study investigated the mollusc communities in seven mining subsidence reservoirs affected by coal mine output (the Katowicka Upland, Upper Silesia, Southern Poland). The objective of the survey was to determine the relationship between the molluscs and their environments and to evaluate the ecological-conservation value of freshwater habitats which support rare and vulnerable molluscs. From 1993 to 2005, 23 mollusc species were recorded. Our result confirmed an invasion by Potamopyrgus antipodarum (Gray, 1843), whose density varied from 2 to 2422 individuals/m² in the waters of the Katowicka Upland. A few rare and vulnerable species were found, e.g. Acroloxus lacustris (Linnaeus, 1758), Hippeutis complanatus (Linnaeus, 1758), Ferrissia wautieri (Mirolli, 1960), Anodonta anatina (Linnaeus, 1758), Musculium lacustre (O.F. Müller, 1774) or Pisidium casertanum (Poli, 1791). Principal component analysis showed a positive correlation between mollusc density and pH, the concentration of chlorides, the total hardness, alkalinity and total dissolved solids, and a negative correlation between the number of species and phosphates. Because of the distinctive environmental features of the mining subsidence reservoirs in Czułów, the research area has provided a refuge for wildlife.     

南羌塘盆地扎仁古油藏白云岩储层特征及成因研究

根据薄片、铸体薄片、压汞、阴极发光等研究,详细描述了南羌塘盆地扎仁古油藏白云岩的储层特征,并对白云岩成因作了初步研究。认为该白云岩在沉积期后变化中经历了多种成岩作用改造,其中影响白云岩储集性的作用主要有白云石化作用、溶蚀作用、重结晶作用和构造应力作用,对白云岩孔渗改善起了积极作用。白云岩主要储集空间为晶间孔、晶间溶孔,储集物性良好。广泛发育的白云石环边结构等淡水成因标志表明,该区白云岩是通过大气水-海水孔隙混合流体交代灰岩所形成的。     

青藏高原区域重磁异常的东西向分区及其构造地质特征

自从大陆整合以来作为一个整体的青藏高原继续受着印度板块向北俯冲的影响,也必定不断地改造着原各地体的结构构造,形成了高原整体意义上东西向的差异。这种差异与原本各地体的组成、结构和东西向延伸不一致。这不仅表现在南北向断裂构造跨各单个地体范围的出现,而且,逐步形成了东西的分区。这种分区突出地表现在区域重力与磁场的特征上,这不仅是局部的岩石磁性与密度变化的结果,而且是由于印度板块向北俯冲过程中,在其前缘的不同部位上经受的压力不同,以及地块的隆升与扩张作用的差异造成了高原东西各区段的地壳组分与厚度的变化。青藏高原的南北向断裂构造并非地壳上层的局部断裂,它具有深层的原因。由于印度板块向北推进的过程中不是均匀地齐头并进,而是在帕米尔高原以东的青藏高原范围内存在着推进速度和俯冲深度的差异,随着高原隆升的加剧高原本身出现断裂,自中新生代以来就存在着一定差异,所以南北向的断裂构造比目前地表见到的多些,而且具有较大的深度,Moho面的深度和地壳厚度都受南北向断裂的控制,并形成了区域重磁场的变化。同时,高原的东西向拉张作用也使南北断裂带发育加剧。     

黑龙江省东部鸡西群与龙爪沟群综合地层对比研究

利用最新古生物、磁性地层年代学资料对鸡西群、龙爪沟群进行了年代地层划分．确定了两群形成时间为早白垩世凡兰吟期-阿尔布中期。同时采用层序地层、盆地形成动力学、事件地层学、盆地湖（海）平面升降曲线与全球海平面升降曲线对比等方法．对两群进行了综合对比．证实两群为同一构造-沉降旋回背景下的等时异相关系。笔者认为龙爪沟群自下而上划分为4个组，即裴德组、七虎林河组、下云山组、朝阳组，其在横向上分别对应鸡西群滴道组、城子河组、穆棱组、东山组。这一研究结果将对进一步讨论黑龙江东部中生代海陆变迁机制、地层、构造格架建立及煤矿预测等具有重要的指示意义。