中巴喀喇昆仑公路(巴基斯坦境内)河床沉积物与泥石流堆积物的关系

统计分析中巴公路沿线红其拉甫河(Khunjerab River)、洪扎河(Huza River)、吉尔吉特河(Gilgit River)、印度河(India River)共计45个河床沉积物样本,对比分析了样本的平均值、中值、分选系数、偏态和峰度等粒度参数,初步探讨了公路沿线河床沉积物粒度分布与区域内泥石流沉积物的关系,结果表明河流沉积物主要来源于泥石流补给,因而具有了类似于泥石流沉积物的分布特征。     

Origin and chemical partitioning of heavy metals in riverbed sediments

In the present investigation, bulk and chemical partitioning of elements in the Shefa-Rud riverbed sediments are studies. Higher concentrations of elemental concentrations have been observed in estuarine zone when compared with riverine sediments (except for AI, Fe, Pb and Mn). Manganese is mobilized under anoxic conditions prevailing in the Caspian Sea. Lithogenous materials are greatly diluted in the estuarine zone by various pollutants present in the Caspian Sea. Organic metallic bonds are not significantly present in the area of study. Geological units of the area of study have resulted in the lower concentrations of elemental concentrations of riverbed sediments when compared with published values for mean crust and world sediments ones. Though, cluster analysis has clearly shown the importance of alumina-silicates in controlling the distribution of Fe and Mn in riverbed sediments but it could not depict controlling mechanism for other studied elements. Geochemical Index (Igeo) and Enrichment Factor (EF) values are indicative of a clean environment throughout the river course. These values are in a well agreement with results of chemical partitioning data. Quantification of EF values is not logically possible and therefore Igeo values can be used more effectively.     

Quaternary chronology of Goulburn Valley sediments and their correlation in Southeastern Australia

Radiocarbon dates from the Goulburn Valley, Victoria, throw new light on the age of Quaternary tectonics, ancestral streams, fluviatile sediments and associated soils.

Sand dunes were formed during glacial times from ancestral rivers in which discharges were higher than at present. Tectonic movement occurred on the Cadell Fault between 13,000 and 20,000 B.P.

Stratigraphic correlation between the various units currently in use on the Riverine Plain is sometimes ambiguous, whereas wider correlation based on ground‐surface similarities in the valleys of the Goulburn, Maribyrnong and Shoalhaven rivers is invalid.

The sediments dated provide limiting ages for the red‐brown earth and minimal prairie soils developed on them in this area.     

Aqueous and solid phase arsenic speciation in the sediments of a contaminated wetland and riverbed

Mobility of As in the environment is controlled by its association with solid phases through adsorption and co-precipitation. To elucidate the mobilization potential of As deposited in wetland and riverbed sediments of the Wells G & H wetland in Woburn, MA as the result of decades of industrial activity, As retention mechanisms were inferred from aqueous and solid phase geochemical measurements of sediment cores. Testing included a sequential extraction method designed for and standard-tested with As phases and pE/pH equilibrium modeling. The uppermost sediments in the Wells G & H wetland contain elevated concentrations of both dissolved and solid phase As (up to 2,000 μg/L and 15,000 μg/g, respectively) and a maximum concentration between 30 and 40 cm depth. Measurements obtained in this study suggested that As in the wetland sediments was predominantly adsorbed, likely onto amorphous Fe (hydr)oxide phases and mixed valence Fe phases. In the riverbed sediments, however, a relatively greater proportion of the solid As was associated with more reduced and crystalline phases, and adsorbed As was more likely associated with Al oxide or secondary reduced Fe phases. pH–pe modeling of the Fe–As–S system was consistent with observations. The association of As with more oxidized phases in the wetland compared with the riverbed sediments may result from a combination of plant activities, including evapotranspiration-driven water table depression and/or root oxygenation.     

Mineralogy,major and trace element geochemistry of riverbed sediments in the headwaters of the Yangtze,Tongtian River and Jinsha River

We collected riverbed sediments of the headwaters of the Yangtze River (Chumaer River, Tuotuo River, Gaerqu River and Buqu River), Tongtian River and Jinsha River (HTJR) flowing on the eastern Tibetan Plateau and analyzed their mineralogical features, major and trace element contents. The results show: (i) very poor correlations of Na₂O, K₂O, CaO, Ba, and Sr to SiO₂, LREE to Th, HREE to Hf, and Ta/La to Ti, and characteristics of Eu anomaly (the ratios of (Eu/Eu^*)_N range from 0.60 to 0.83 with an average value of 0.71) all indicate that the Jinsha River sediments have not undergone much mineralogical sorting; (ii) illite and chlorite are predominant clay minerals, and quartz, calcite, dolomite, albite, and K-feldspar are prevailing non-clay minerals. The characteristics of mineral assemblage indicate relatively weak chemical weathering degree in these river basins; (iii) very high contents of Fe₂O₃, MgO, TiO₂, Sc, V, Cr, Co, and Ni at Panzhihua mainly result from the huge-sized V–Ti magnetite deposits occurred in layered gabbroic intrusion; and (iv) the chemical alteration index (CIA) in the HTJR ranges from 46.5 to 69.2 and with an average value of 60.5 which indicates relatively weak weathering degree.     

The occurrence of stanols in various living organisms and the behavior of sterols in contemporary sediments

Unsaturated sterols (stenols) and saturated sterols (stanols) in phytoplankton and Zooplankton from Lake Suwa and from higher plants around the lake were analyzed by combined GLC and MS. In all the organisms investigated, 5α-cholestanol, 24-methylcholestan-3β-ol and 24-ethyl-5α-cholestanol were found, although in low concentrations, together with large quantities of stenols. This strongly suggests the contribution of stanols from living organisms to recent sediments.Findings from incubation experiments of cholesterol and 5α-cholestanol in the surface sediment from Lake Suwa extending through 450 days suggest the following: (1) stanols are slowly degraded and tend to survive unaltered in sediments in comparison with stenols, (2) in a relatively oxidative depositional environment such as Lake Suwa, the greater part of the stanols in the surface sediment originates from living organisms, (3) the reduction zone in which the degradation of sterols is suppressed and the rapid hydrogenation of stenols takes place may be in the microbiologically active sediment from 1 cm to about 10 cm in Lake Suwa, and (4) the increase in the ratio of stanols to stenols with depth below the zone may be caused by the simultaneous progress of preferential degradation and slow hydrogenation of stenols during long-term preservation in sediments.     

Potential effect of natural radionuclides in riverbed sediments: a statistical approach based on granulometric and magnetic mineral differences

South India is one of the regions in the world that has the highest background radiation levels. In this region, river sediments are used in large quantities as building material. Therefore, the knowledge of the radionuclides distribution in such sediments is important for assessing their potential adverse effects on humans residing in buildings made of sediment material. For this goal, we focus on the determination of the natural radioactivity levels and magnetic properties in sediment samples collected from 33 locations along the southwestern Bharathapuzha river originating from the Anamalai hills. The sediment samples were subdivided into two categories according to particle size. It is observed that the average activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in sediment samples varied greatly with granulometric and geological differences. The average values of ²²⁶Ra, ²³²Th, and ⁴⁰K and its associated radiological hazard parameters for category II samples (particle size between 149 μm and 2 mm) were lower than category I sediment samples (bulk samples). Moreover, the average radionuclide activity concentrations (except for ⁴⁰K) and the calculated radiation hazard parameters are higher in the lowland region compared to the highland and the midland regions. The mass-specific magnetic susceptibility values ranged widely along the river, as well as between physiographic regions, e.g., average values for category I sediment samples were 950.2 × 10^?8, 351.1 × 10^?8 and 131.8 × 10^?8 m³ kg^?1 (for high-, mid- and lowland regions, respectively). Differences between physiographic regions and sediment fractions from both radioactivity determinations and magnetic parameters were analyzed with statistical tests and multivariate analysis, which showed the advantages of using both independent techniques.     

Magnetic susceptibility as a proxy for coal ash pollution within riverbed sediments in a watershed with complex geology (southeastern USA)

A study of near surface sediments from the Dan River (southeastern USA) was conducted to assess the use of magnetic properties as proxies of coal ash after a recent spill. The watershed geology is diverse and potentially contributes magnetic minerals to riverbed sediment from diabase dikes in the Dan River Triassic Basin and from granitic gneiss outside the basin. Coal ash is heterogeneous, including aluminosilicate spheres, amorphous particles and carbonaceous rods and lacy particles. The magnetic fraction of ash from the failed storage pond is up to 17 wt% and is mostly composed of black spheres with maghemite and magnetite. Ash was detected in riverbed sediment from quiet water settings such as inside of meander bends, the confluence of tributary streams and near islands between the spill site and 20 miles downstream in the Schoolfield Reservoir, Danville, VA. The strong magnetic signal is detected above background in riverbed samples and is strongly positively correlated with total ash; elevated low field magnetic susceptibility (χ _LF) is evident in samples with ≥ 12% ash content. Anhysteretic remanent magnetization and hysteresis parameters delineate native sediment, ash-bearing sediment, and diabase dikes. Between 20 and 70 miles downstream of the spill site, ash concentrations were either buried or too low due to dilution with native sediment to be detected with χ _LF in riverbed samples.     

长江与黄河沉积物中磁铁矿成分标型意义

长江与黄河沉积物中磁铁矿的元素组成揭示,两者的ＦｅＯ与Ｆｅ２Ｏ３及一些置换元素的含量差异明显。长江磁铁矿中ＦｅＯ与Ｆｅ２Ｏ３含量稍高于黄河磁铁矿,而Ｔｉ、Ｖ、Ｓｉ、Ａｌ、Ｃｒ、Ｍｇ及Ｍｎ等元素含量明显地低于黄河磁铁矿,元素含量变化显著小于黄河磁铁矿。这反映长江磁铁矿中Ｆｅ＾２＋及Ｆｅ＾３＋的类质同象置换较少,主要为均质相单矿物颗粒,而黄河磁铁矿中元素含量变化大,既有均质相的颗粒,也存在一些Ｆｅ＾２     

Spores of the dung fungus Sporormiella: Increased abundance in historic sediments and before Pleistocene megafaunal extinction

Spores of the dung fungus Sporormiella become abundant following the historic introduction of grazing herbivores at seven sites in the western United States. During the Holocene they are generally rare, but at six sites Sporormiella spores are abundant before the extinction of Pleistocene megaherbivores ca. 11,000 yr B.P. Sporormiella spores are directly linked to extinct megaherbivores by their presence in mammoth dung preserved in Bechan Cave, Southern Utah. Their abundance in late-glacial sediments may reflect the abundance of megaherbivores during Quaternary, thereby indicating the age of Pleistocene extinctions where other indicators are absent.     

碎屑金红石地球化学特征对库车坳陷中生代沉积物源的启示

本文主要对库车坳陷的库车河流域和巴音布鲁克盆地中生代砂岩样品进行了碎屑金红石微量元素电子探针分析。结果显示,巴音布鲁克地区侏罗纪砂岩中的碎屑金红石来自变质泥质岩和来自基性变质岩的比例大致相当,而库车坳陷中生代砂岩中碎屑金红石则主要来自变质泥质岩。两地金红石的变质级别以角闪岩相/榴辉岩相为主,并有一定比例麻粒岩相变质的金红石。库车坳陷中生代砂岩中麻粒岩相金红石的含量,从三叠纪至白垩纪呈现出低—高—低的特点,说明侏罗纪时期物源方向有所变化,可能有东南部物源的参与。白垩纪时期,库车河地区砂岩中麻粒岩相变质金红石含量减少,可能与南天山再度抬升隆起成为优势物源区有关。     

Mercury Anomaly in the Okinawa Trough Sediments—An Indicator of Modern Seafloor Hydrothermal Activity

The Okinawa Trough is located between the shelf-sea area of the East China Sea and the deep-sea area of western Pacific Ocean. More than 60 chemical elements in the sediments from the shelf area of the East China Sea, the Okinawa Trough and western Pacific Ocean were determined by advanced techniques including neutron activation analysis, X-ray fluorescence spectrometry, atomic fluorescence spectrometry and atomic absorption spectrometry. Quantitative comparisons of the element abundances of the sediments were made in terms of the enrichment coefficients (K) of the elements.K > 1.5 indicates enrichment (K = 1.5–2, weak enrichment; K = 2–4, strong enrichment) andK > 4, anomalous enrichment. The results show that the Okinawa Trough sediments are characterized by Hg anomaly and the enrichment of such elements as Au, Ag, Se, Te, Sb, Cd, Mn, Mo, etc. Detailed studies show that the excess Hg comes from hydrothermal solutions rather than from the continent, sea water, marine organisms, cosmic dust or volcanic rocks. Attributed to modern hydrothermal activities on the sea floor, Hg anomaly can be used as a geochemical indicator of modern seafloor hydrothermal activity. This project was granted by the National Natural Science Foundation of China.     

Geochemical-focusing of manganese in lake sediments — An indicator of deep-water oxygen conditions

The lateral distributions of Mn concentrations in the sediments of two Swiss lakes under varying oxygen conditions have been determined. The comparison of Mn distribution patterns with oxygen in the deep-water provides strong evidence for a geochemical-focusing effect, which is driven by the redox cycle of manganese. Conditions essential for this process to occur are anoxic sediments in contact with oxic deep-water. Average sedimentary manganese concentrations determined for different water-depth ranges are directly proportional to the area of shallower sediments. This result indicates that geochemical-focusing of manganese in lake sediments is a promising proxy indicator for the reconstruction of oxygen conditions during deposition.     

上海市近岸海域表层沉积物类型与元素丰度相关关系特征

通过上海市近岸海域多目标区域地球化学调查,共采集947件表层沉积物样品,分析测试了52种化学元素以及pH值和有机碳等指标。总结了该区域表层沉积物及深层沉积物类型和分布特征,沉积物类型主要为细砂、粉砂质砂、砂质粉砂、粉砂、粘土质粉砂,其中粘土质粉砂分布最为广泛。元素含量与砂含量呈正相关的元素主要为SiO2、Sr、Na2O等。其它指标大都与粘土含量呈正相关关系。     

On the experimental silicification of microorganisms II. On the time of appearance of eukaryotic organisms in the fossil record

On the basis of ultrastructural, biochemical and genetic studies, bacteria and blue green algae (Kingdom Monera, all prokaryotes) differ unambiguously from the eukaryotic organisms (Fungi, plants sensu stricto) and protists or protoctists, (Copeland, 1956). The gap between eukaryotes and prokaryotes is recognized as the most profound evolutionary discontinuity in the living world. This gap is reflected in the fossil record. Fossil remains of Archaean and Proterozoic Aeons primarily consist of prokaryotes and the Phanerozoic is overwhelmingly characterized by fossils of the megascopic eukaryotic groups, both metazoa and metaphyta. Based on the morphological interpretation of microscopic objects structurally preserved in Precambrian cherts, the time of appearance of remains of eukaryotic organisms in the fossil record has been claimed to be as early as 2.7 · 10⁹ years ago, (Ka?mierczak, 1976). Others suggest chronologies varying between 1.7 to 1.3 · 10⁹ (Schopf et al., 1973) or a time approaching 1.3 · 10⁹ years (Cloud, 1974).There is general agreement that many of the Ediacaran faunas, which have been dated at about 680 m.y. are fossils of megascopic soft-bodied invertebrate animals. Since all invertebrates are eukaryotic, the ca. 680 m.y. date for deposition of these animal assemblages may represent the earliest appearance of eukaryotic organisms. But the question remains as to whether there is definitive evidence for eukaryotic cells before this “benchmark” of the late Precambrian.An excellent discussion of this particular problem as especially relating to acritarchs extending from rocks of Upper Riphean through Vendian and into the basal Cambrian is presented in recent studies by Vidal (1974, 1976) in Late Precambrian microfossils from the Visingsö rocks of southern Sweden.Previous work on the laboratory silicification of wood and algal mat communities (Leo and Barghoorn, 1976) suggested that further analysis of “artificial fossils” might be of aid in the interpretation of fossil morphology toward the ultimate solution of this problem. Thus the procedure developed by one of us (ESB) for laboratory wood silicification was adapted to various smaller objects.By successive immersions of wet cellular aggregates, colonies of various organisms and abiotic organic microspheres in tetraethyl orthosilicate, silicified cells and structures are produced which bear an interesting resemblance to ancient chert-embedded microfossils. Our observation of these microorganisms and proteinoid microspheres silicified in the laboratory as well as of degrading microorganisms, both eukaryotic and prokaryotic, have led us to conclude that many, if not all, of the criteria for assessing fossil eukaryotic microorganisms are subject to serious criticism in interpretation. We studied a large variety of prokaryotic algae, some eukaryotic algae, fungi, protozoa, and abiotic organic microspheres stable at essentially neutral pH. In some cases, degradation and/or silicification systematically altered both size and appearances of microorganisms. By the use of monoalgal cultures of blue-green algae, features resembling nuclei, chloroplasts, tetrads, pyrenoids, and large cell size may be simulated. In many cases individual members of these cultures show so much variation that they may be mistaken as belonging to more than one species. The size ranges for silicified prokaryotic and eukaryotic algae overlap. Several prokaryotes routinely yielded spherical or filamentous structures that resembled large cells. Because of genuine large sizes (e.g., Prochloron), shrinkage, systematic alteration or congregation of unicells to form other structures we find sizes to be of very limited use in determining whether an organism of simple morphology was prokaryotic or eukaryotic. Although some “prebiotic proteinoid microspheres” (of Fox and Harada, 1960) are impossible to silicify with our laboratory methods, those stable at neutral pH (Hsu and Fox, 1976) formed spherical objects that morphologically resemble silicified algae or fungal spores. Many had internal structure. We conclude that even careful morphometric studies of fossil microorganisms are subject to many sources of misinterpretation. Even though it is a logical deduction that eukaryotic microorganisms evolved before Ediacaran time there is no compelling evidence for fossil eukaryotes prior to the late Precambrian metazoans.     

Alluvium: Implications for stratigraphy and correlation of quaternary sediments

Based on a generalized knowledge of conditions and mechanisms for accumulation of the cycle terrace alluvium on plain and mountain rivers, alluvium is suggested as an instrument for stratigraphic studies, interregional correlation, and correction of present schemes. Diachronous alluvial formations are uniformly constructed. They include two subunits, a lower “warm” and an upper “cool” one. In addition the formations are subdivided in dynamic phases that display a dominating regime and stages of erosion-and-accumulation cycle. Alluvial formations are characterized by a peculiar mechanical and mineralogical composition, gradation, bedding, thickness, landscape and climatic conditions of accumulation, paleontological content, character of occurrence, and position in a cycle incision. All these characters of an alluvial formation and its subformations correspond to a complete climatic rhythm and oscillation stages. Alluvial formations are associated in a certain way with glacial and marine sediments making up a single formation complex.     

江陵剖面沉积物的粒度特征及其古气候意义

通过对江汉平原江陵剖面高分辨率采样，利用激光粒度仪对沉积物粒度进行测试，分析了粒度的组成及其参数特征，结合孢粉资料和岩性特征，探讨了粒度在该区的古气候意义。结果表明，降水量较大的湿润气候条件下沉积物的粗颗粒组分明显增多；而降水量相对较少的干旱气候条件下沉积物的粗颗粒组分相对减少。通过与邻区对比．江汉平原江陵剖面沉积物粒度所揭示的该区近9000aB．P．以来的古气候变化与国内相邻区域其他指标的研究结果相一致。