Miniature gravity corer for recovering short sediment cores   总被引：12，自引：0，他引：12  

John R. Glew 《Journal of Paleolimnology》1991,5(3):285-287

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IMPACTS OF FUTURE SEA LEVEL RISE ON SALT WATER INTRUSION IN THE CHANGJIANG RIVER ESTUARY   总被引：1，自引：0，他引：1  

杨桂山 《中国地理科学(英文版)》1992,2(1):30-41

Sea level rise could increase the salinity of an estuary by altering the balance between fresh water and salt water. The implications of sea level rise for increasing salinity have been examined in the Changjiang (Yangtze) River estuary. By correlative analysis of chlorinity, discharge and tidal level and calculation of two-dimensional chlorinity, distribution of the Changjiang River estuary, the changes of the intensity and lasting hours of salt water intrusion at Wusong Station and the changes of chlorinity distribution in the South Branch of the Changjiang River estuary have been estimated when future sea level rises 50-100 cm. The intensity of salt water intrusion in the future will be far more serious than current trend.  相似文献   

Biostratigraphic and aminostratigraphic constraints on the age of the Middle Pleistocene glacial succession in north Norfolk,UK     

Richard C. Preece  Simon A. Parfitt  G. Russell Coope  Kirsty E. H. Penkman  Philippe Ponel  John E. Whittaker 《第四纪科学杂志》2009,24(6):557-580

Considerable debate surrounds the age of the Middle Pleistocene glacial succession in East Anglia following some recent stratigraphical reinterpretations. Resolution of the stratigraphy here is important since it not only concerns the glacial history of the region but also has a bearing on our understanding of the earliest human occupation of north‐western Europe. The orthodox consensus that all the tills were emplaced during the Anglian (Marine Isotope Stage (MIS) 12) has recently been challenged by a view assigning each major till to a different glacial stage, before, during and after MIS 12. Between Trimingham and Sidestrand on the north Norfolk coast, datable organic sediments occur immediately below and above the glacial succession. The oldest glacial deposit (Happisburgh Till) directly overlies the ‘Sidestrand Unio‐bed’, here defined as the Sidestrand Hall Member of the Cromer Forest‐bed Formation. Dating of these sediments therefore has a bearing on the maximum age of the glacial sequence. This paper reviews the palaeobotany and describes the faunal assemblages recovered from the Sidestrand Unio‐bed, which accumulated in a fluvial environment in a fully temperate climate with regional deciduous woodland. There are indications from the ostracods for weakly brackish conditions. Significant differences are apparent between the Sidestrand assemblages and those from West Runton, the type site of the Cromerian Stage. These differences do not result from contrasting facies or taphonomy but reflect warmer palaeotemperatures at Sidestrand and a much younger age. This conclusion is suggested by the higher proportion of thermophiles at Sidestrand and the occurrence of a water vole with unrooted molars (Arvicola) rather than its ancestor Mimomys savini with rooted molars. Amino acid racemisation data also indicate that Sidestrand is significantly younger than West Runton. These data further highlight the stratigraphical complexity of the ‘Cromerian Complex’ and support the conventional view that the Happisburgh Till was emplaced during the Anglian rather than the recently advanced view that it dates from MIS 16. Moreover, new evidence from the Trimingham lake bed (Sidestrand Cliff Formation) above the youngest glacial outwash sediments (Briton's Lane Formation) indicates that they also accumulated during a Middle Pleistocene interglacial – probably MIS 11. All of this evidence is consistent with a short chronology placing the glacial deposits within MIS 12, rather than invoking multiple episodes of glaciation envisaged in the ‘new glacial stratigraphy’ during MIS 16, 12, 10 and 6. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Ice‐cover variability on shallow lakes at high latitudes: model simulations and observations     

Claude R. Duguay  Greg M. Flato  Martin O. Jeffries  Patrick Mnard  Kim Morris  Wayne R. Rouse 《水文研究》2003,17(17):3465-3483

A one‐dimensional thermodynamic model for simulating lake‐ice phenology is presented and evaluated. The model can be driven with observed daily or hourly atmospheric forcing of air temperature, relative humidity, wind speed, cloud amount and snowfall. In addition to computing the energy balance components, key model output includes the temperature profile at an arbitrary number of levels within the ice/snow (or the water temperature if there is no ice) and ice thickness (clear ice and snow‐ice) on a daily basis, as well as freeze‐up and break‐up dates. The lake‐ice model is used to simulate ice‐growth processes on shallow lakes in arctic, sub‐arctic, and high‐boreal forest environments. Model output is compared with field and remote sensing observations gathered over several ice seasons. Simulated ice thickness, including snow‐ice formation, compares favourably with field measurements. Ice‐on and ice‐off dates are also well simulated when compared with field and satellite observations, with a mean absolute difference of 2 days. Model simulations and observations illustrate the key role that snow cover plays on the seasonal evolution of ice thickness and the timing of spring break‐up. It is also shown that lake morphometry, depth in particular, is a determinant of ice‐off dates for shallow lakes at high latitudes. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Post-solidification cooling and the age of Io's lava flows     

Ashley Gerard Davies  Dennis L. Matson  Glenn J. Veeder  Torrence V. Johnson  Diana L. Blaney 《Icarus》2005,176(1):123-137

The modeling of thermal emission from active lava flows must account for the cooling of the lava after solidification. Models of lava cooling applied to data collected by the Galileo spacecraft have, until now, not taken this into consideration. This is a flaw as lava flows on Io are thought to be relatively thin with a range in thickness from ∼1 to 13 m. Once a flow is completely solidified (a rapid process on a geological time scale), the surface cools faster than the surface of a partially molten flow. Cooling via the base of the lava flow is also important and accelerates the solidification of the flow compared to the rate for the ‘semi-infinite’ approximation (which is only valid for very deep lava bodies). We introduce a new model which incorporates the solidification and basal cooling features. This model gives a superior reproduction of the cooling of the 1997 Pillan lava flows on Io observed by the Galileo spacecraft. We also use the new model to determine what observations are necessary to constrain lava emplacement style at Loki Patera. Flows exhibit different cooling profiles from that expected from a lava lake. We model cooling with a finite-element code and make quantitative predictions for the behavior of lava flows and other lava bodies that can be tested against observations both on Io and Earth. For example, a 10-m-thick ultramafic flow, like those emplaced at Pillan Patera in 1997, solidifies in ∼450 days (at which point the surface temperature has cooled to ∼280 K) and takes another 390 days to cool to 249 K. Observations over a sufficient period of time reveal divergent cooling trends for different lava bodies [examples: lava flows and lava lakes have different cooling trends after the flow has solidified (flows cool faster)]. Thin flows solidify and cool faster than flows of greater thickness. The model can therefore be used as a diagnostic tool for constraining possible emplacement mechanisms and compositions of bodies of lava in remote-sensing data.  相似文献   

圆盘固相萃取富集-气相色谱法测定地表水中有机氯和有机磷农药   总被引：4，自引：2，他引：2  

何淼  饶竹 《岩矿测试》2008,27(1):12-16

采用环境友好的圆盘固相萃取新技术富集水体中有机氯农药和有机磷农药,分别用微池电子捕获检测器(μECD)和火焰光度检测器(FPD)气相色谱法检测,实现了水中有机氯和有机磷农药残留物的测定。结果表明,16种有机氯农药的平均回收率为64.7%~102%,精密度(RSD,n=6)为2.9%~15%;13种有机磷农药的平均回收率为65.9%~104%,精密度(RSD,n=6)为1.7%~17%。方法快速、灵敏、低污染,可用于水体中多种有机氯农药和有机磷农药的残留分析。  相似文献   

大型敞流坳陷湖盆浅水三角洲与湖盆中心砂体的形成与分布   总被引：34，自引：0，他引：34  

邹才能  赵文智  张兴阳  罗平  王岚  刘柳红  薛叔浩  袁选俊  朱如凯  陶士振 《地质学报》2008,82(6):813-825

大型敞流坳陷湖盆浅水三角洲及湖盆中心砂体已成为中国陆相盆地岩性油气藏最重要的勘探目标。通过对现代典型湖盆浅水三角洲的深入分析,结合我国中、新生代大型坳陷湖盆浅水三角洲及湖盆中心砂体的地质研究,取得以下主要进展与认识：①在分析浅水三角洲形成地质背景的基础上,按照供源体系、湖水深度及三角洲前缘倾斜坡度将湖盆三角洲分为9种成因结构类型;②建立了毯式浅水曲流河三角洲的沉积模式,指出末端分流河道及末端决口扇是浅水曲流河三角洲的典型微相类型;③分析了浅水三角洲砂体大面积分布的形成条件,指出敞流湖盆是湖盆中心浅水三角洲砂体发育的重要条件,敞流通道对湖盆中心砂体分布有重要控制作用;④湖盆中心发育河流、三角洲、湖流及密度底流砂体等牵引流成因砂体,也发育洪水浊积扇及滑塌浊积扇等重力流成因砂体;⑤大型浅水三角洲体系三级层序界面对岩性（成岩）圈闭的发育有重要控制作用,三角洲平原带层序界面上覆叠置砂体富集岩性油气藏,勘探潜力大。本文研究成果希对坳陷湖盆沉积学研究及岩性油气藏勘探能有推动作用。  相似文献   

澜沧江云南德钦古水一带第四纪堰塞湖的沉积特征及其环境意义     

张永双  赵希涛 《地质学报》2008,82(2):262-268

在云南省西北部德钦县古水一带深切的澜沧江河谷中,发现了一套第四纪湖相沉积物,以纹层状粘土、粉砂质粘土和粉砂的互层组合为特征,构成了第三和第四级阶地的基座.笔者对该湖相剖面进行了U系、孢粉和若干地球化学指标的分析测试,并以这些结果讨论了古湖的形成时代和成因,以及古湖堆积时期的古植被和古气候.剖面顶部、中部和中下部粘土的U系法年龄测定结果分别为52.3±3.4 ka、64.2±5.6 ka和81.9±6.5 ka,说明古水古湖形成于晚更新世早中期的末次间冰期晚期和末次冰期的早冰阶与间冰阶早期,很可能是大型冰川(如下游的明永冰川等)或巨量的冰水沉积物堰塞了澜沧江河谷而造成的结果.  相似文献   

Geotechnical properties of evaporite soils of the Dead Sea area     

Sam Frydman  Josef Charrach  Ian Goretsky 《Engineering Geology》2008,101(3-4):236-244

The Dead Sea Basin is the lowest point on earth and is tectonically subsiding. During the Holocene Period the climate became much drier with increasing evaporation whereby initially lacustrine sediments were deposited from the non-marine brines, giving a multi-layered stratigraphy of lime carbonate and halite sediments. The lime carbonate sediments are comprised of laminated, clay to silt sized, clastic sediments (calcite) and authigenic aragonite and gypsum. The halite commonly appears as rock salt. Chemical industries, based on harvesting the salts from the Dead Sea, have developed on both the Israeli and the Jordanian sides of the basin. The lime carbonate soils are used for dike construction, and these soils, together with significant salt layers, are encountered in the foundations of structures, dikes, and tailings dams, requiring definition of their geotechnical properties. Use of standard soil mechanics definitions and testing approaches for the lime carbonates have been found inapplicable, particularly in view of their exceptionally high saline content, and it has been necessary to develop new concepts. The rock salt is encountered at shallow depths, with unit weights considerably lower than those usually discussed in the literature, and with correspondingly different mechanical properties. The geotechnical properties of these soils, and approaches used to define them, are discussed in the paper.  相似文献   

Li-Sr-Nd isotope signatures of the plume and cratonic lithospheric mantle beneath the margin of the rifted Tanzanian craton (Labait)   总被引：3，自引：2，他引：1  

Sonja Aulbach  Roberta L. Rudnick  William F. McDonough 《Contributions to Mineralogy and Petrology》2008,155(1):79-92

Lithium concentrations and isotopic compositions of olivine and ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd of coexisting clinopyroxene from peridotite xenoliths from the Quaternary Labait volcano, Tanzania, document the influence of rift-related metasomatism on the ancient cratonic mantle. Olivines show negative correlations between Fo content and both δ⁷Li and Li concentrations. Olivines in iron-rich peridotites (Fo_85–87) have high Li concentrations (3.2–4.8 ppm) and heavy δ⁷Li (+5.2 to +6.6). In contrast, olivines in ancient, refractory peridotites have lower Li concentrations (∼2 ppm) and relatively light δ⁷Li (+2.6 to +3.5). This reflects mixing between ancient, refractory cratonic lithosphere and asthenosphere-derived rift magmas. A uniquely fertile, deformed, high-temperature garnet lherzolite, interpreted to be from the base of the lithosphere, has a ⁸⁷Sr/⁸⁶Sr of 0.7029 and ¹⁴³Nd/¹⁴⁴Nd of 0.51286, similar to HIMU oceanic basalts. It provides the best estimate of the Sr–Nd isotope composition of the upwelling mantle (i.e., plume, sensu lato) underlying this portion of the East African Rift, and is slightly less radiogenic compared to previous estimates of the plume that were based on rift basalts. Although elevated δ⁷Li are not exclusive to HIMU source regions, the data collectively indicate that the plume beneath Labait has HIMU characteristics in Sr, Nd and Li isotope composition. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献