华南老红砂沉积年代学及其环境意义：以福建青峰老红砂为例   总被引：1，自引：0，他引：1  

靳建辉  李志忠  雷国良  凌智永  姜锋  申健玲  刘秀铭 《地理科学》2017,37(2):301-310

对福建海坛岛青峰老红砂进行了系统的光释光测年研究,结合已发表的相关测年数据,在统一的时间标尺上探讨了老红砂发育过程及其与海平面变化和东亚季风变化之间的关系。结果表明：① QFS剖面沉积年龄为110~33 ka,起始发育年龄延伸到了末次间冰期。主要涵盖了MIS5c~MIS3阶段,其中存在4个快速堆积期。结合已发表的年代学数据进行综合分析,认为前人得出的老红砂发育在末次冰期以来的结论需要得到修正。② 华南老红砂发育过程与区域海平面变化密切相关。在末次间冰期和末次冰期均有发育,高海面（>-50 m）或较高海面（-50~-70 m）时期是老红砂普遍发育期。区域地壳运动叠加海平面变化造成闽南和闽东北老红砂的沉积差异：海退过程中的较高海面时期北部先发生快速堆积;海侵过程中的较高海面时期南部先发生快速堆积。LGM（海平面<-70 m）期,老红砂不发育。③ 老红砂在冰期-间冰期尺度上的沉积速率体现了源区气候和海平面变化对老红砂物源输送的双重制约。  相似文献   

Alteration of nuclear glass in contact with iron and claystone at 90 °C under anoxic conditions: Characterization of the alteration products after two years of interaction     

《Applied Geochemistry》2016

The present study investigates the alteration of a fractured glass block in contact with iron and Callovo-Oxfordian claystone at 90 °C under anoxic and water-saturated conditions. The alteration rates and the nature of glass alteration products at the different compact interfaces (glass-clay, glass-iron) and in cracks were assessed by solution chemistry and microscopic-scale techniques (scanning electron microscopy coupled with energy-dispersive X-ray microscopy, microRaman spectroscopy, and X-ray absorption fine structure spectroscopy). A significant but modest (two-fold) increase in glass alteration in contact with steel was observed, leading to an average alteration rate over the experiment of about 0.007–0.014 g/m²/d. This rate is significantly lower than forward rate r₀ in clay-equilibrated groundwater (1.7 g/m²/d), indicating that a decrease of the alteration rate was not hindered by the steel presence. The corrosion–alteration interface was made up of successive layers of corrosion products in contact with iron, a layer of Fe silicates, and an altered glass layer enriched in Fe. Characterization of the glass block in direct contact with claystone revealed that the thickness of altered glass was much more important than at the glass-iron interface. The altered glass layer in contact with clay was slightly enriched in Fe and Mg, and depleted in alkali cations. Altered glass layers in cracks were usually limited to fringes thinner than 2 μm, with a thickness decreasing from the crack mouth, indicating that alteration is controlled by transport in the cracks. The fractures were partially filled with calcite and lanthanide hydroxocarbonate precipitates. These results contribute to the understanding of nuclear vitrified waste-iron-corrosion products interactions in a deep geological repository.  相似文献   

Does ecological redundancy maintain functioning of marine benthos on centennial to millennial time scales?          下载免费PDF全文

Chris L.J. Frid  Bryony A. Caswell 《Marine Ecology》2016,37(2):392-410

Predicting the ability of the biosphere to continue to deliver ecosystem services in the face of biodiversity loss and environmental change is a major challenge. The results of short‐term and small‐scale experimental studies are both equivocal and difficult to extrapolate from. In this study we use data on benthic palaeocommunities covering 4,000,000 years (in the Late Jurassic when temperate coastal seas in NW Europe experienced fluctuations in oxygenation). The biological traits associated with each species in the palaeocommunities were combined to index the delivery of ecological functions. Five ecosystem functions were examined: food for large mobile predators, biogenic habitat provision, nutrient recycling/regeneration, inorganic carbon sequestration and food‐web dynamics. In modern systems these ecological functions underpin ecosystem services that are important for human well‐being. Our results show that the supply of food for higher predators was remarkably constant during the 4,000,000 years, suggesting that redundancy amongst species in the assemblage drives the biodiversity–ecosystem function (BEF) relationship. By contrast, the provision of biogenic habitat varied with the occurrence of a relatively few taxa, a pattern consistent with a rivet type model of BEF. For nutrient regeneration, carbon sequestration and food‐web dynamics the patterns were complex and suggestive of an idiosyncratic model of BEF. To our knowledge this is the first study to quantify ecological functioning through deep time and demonstrates the utility of this approach to understanding long‐term patterns of BEF in both ancient and contemporary marine ecosystems. The delivery of all five ecological functions studied became increasingly variable as the regional climate became drier, thus modifying the supply of terrigenous nutrient inputs.  相似文献   

Clay smear: Review of mechanisms and applications     

《Journal of Structural Geology》2016

Clay smear is a collection of fault processes and resulting fault structures that form when normal faults deform layered sedimentary sections. These elusive structures have attracted deep interest from researchers interested in subsurface fluid flow, particularly in the oil and gas industry. In the four decades since the association between clay-smear structures and oil and gas accumulations was introduced, there has been extensive research into the fault processes that create clay smear and the resulting effects of that clay smear on fluid flow. We undertake a critical review of the literature associated with outcrop studies, laboratory and numerical modeling, and subsurface field studies of clay smear and propose a comprehensive summary that encompasses all of these elements. Important fault processes that contribute to clay smear are defined in the context of the ratio of rock strength and in situ effective stresses, the geometric evolution of fault systems, and the composition of the faulted section. We find that although there has been progress in all avenues pursued, progress has been uneven, and the processes that disrupt clay smears are mostly overlooked. We highlight those research areas that we think will yield the greatest benefit and suggest that taking these emerging results within a more process-based framework presented here will lead to a new generation of clay smear models.  相似文献   

K-Ar Dating of Fault Gouges from the Red River Fault Zone of Vietnam   总被引：1，自引：0，他引：1  

BUI Hoang B  NGO Xuan Thanh  Yungoo SONG  Tetsumaru ITAYA  Koshi YAGI  KHUONG The Hung  NGUYEN Tien Dung 《《地质学报》英文版》2016,90(5):1653-1663

Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions(0.1 μm,0.1-0.4 μm and 0.4-1.0 μm).The results show that the K-Ar age values decrease from coarser to finer grain fractions(24.1 to 19.2 Ma),suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite(19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma).In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi(DNCV) metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone(RR-ASFZ).During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.  相似文献   

The ultimate uplift capacity of multi-plate strip anchors in undrained clay     

R.S. Merifield  C.C. Smith 《Computers and Geotechnics》2010

Soil anchors are commonly used as foundation systems for structures requiring uplift resistance such as transmission towers, or for structures requiring lateral resistance, such as sheet pile walls. Anchors commonly have more than one plate or bearing element and therefore there is a complex interaction between adjacent plates due to overlapping stress zones. This interaction will affect the failure mode and ultimate capacity. However, no thorough numerical analyses have been performed to determine the ultimate pullout loads of multi-plate anchors. By far the majority of the research has been directed toward the tensile uplift behaviour of single anchors (only one plate). The primary aim of this research paper is to use numerical modelling techniques to better understand plane strain multi-plate anchor foundation behaviour in clay soils. A practical design framework for multi-plate anchor foundations will be established to replace existing semi-empirical design methods that are inadequate and have been found to be excessively under or over conservative. This framework can then be used by design engineers to more confidently estimate the pullout capacity of multi-plate anchors under tension loading.  相似文献   

页岩气的赋存形式研究及其石油地质意义   总被引：11，自引：0，他引：11  

张雪芬  陆现彩  张林晔  刘庆 《地球科学进展》2010,25(6):597-604

页岩气是以游离、吸附和溶解状态赋存于暗色泥页岩中的天然气,其赋存形式具有多样性,但以游离态和吸附态为主,溶解态仅少量存在。综述了页岩气的赋存形式及其影响因素,包括页岩气成因、页岩的物质组成(有机碳含量、矿物成分、岩石含水量)、岩石结构(孔隙度、渗透率)和温度、压力等。认识影响不同形式页岩气赋存量的地质因素,有助于利用容积法评估页岩气地质储量的水平,因为游离态页岩气的含量取决于页岩的有效孔隙度和含气饱和度,而吸附态页岩气的含量则受页岩的气体吸附能力影响。认为发展页岩孔隙结构表征技术,研究页岩气在粘土矿物表面和纳米孔隙中的吸附行为,可以进一步了解不同地质条件下页岩气的赋存形式,并为页岩气的资源评价提供更为准确的参数,因此它们将是页岩气下一步研究的重点之一。  相似文献   

Effects of fracture grouting with sodium hydroxide during electro-osmosis on clay     

Jun Wang  Ziyang Gao  Lingyu Li  Hongtao Fu  Yuanqiang Cai 《Marine Georesources & Geotechnology》2013,31(2):245-255

ABSTRACT

Electro-osmosis is a foundation treatment method for clay that is not widely used because of its nonuniform consolidation effect and high cost. To overcome these limitations, this study investigates fracture grouting. To determine the optimal grouting method, anode grouting, polyurethane grouting, and fracture grouting were first compared in one-dimensional electro-osmosis consolidation tests using self-made model boxes under an equal electric potential gradient, and then different solution concentrations were tested. By comparing the current, drainage rate, and coefficient of energy consumption during the electro-osmosis process, as well as moisture content, electrical conductivity, and shear strength after the tests, the moisture and shear strength of clay after electro-osmosis were found to be significantly improved by adding chemical reagents at the fracture. In addition, the optimum concentration of fracture grouting was determined to be 1.5%, and the shear strength after testing of clay that had been treated with sodium hydroxide was found to be higher than that of the control group. However, the effects of fracture grouting in the early stage were clearer than the effects of fracture grouting at later stages.  相似文献   

Engineering properties of unfired clay masonry bricks   总被引：2，自引：1，他引：1  

J.E. Oti  J.M. Kinuthia  J. Bai 《Engineering Geology》2009,107(3-4):130-139

The shortage of low cost and affordable housing in the UK has led to many investigations into new building masonry materials. Fired clay masonry bricks are conventionally used for mainstream masonry wall construction but suffer from the rising price of energy plus other related environmental problems such as high energy usage and carbon dioxide emission. The use of stabilised unfired clay bricks for masonry construction may solve these problems.This paper reports on the engineering properties of unfired clay bricks produced during the first industrial trial of unfired clay material development carried out at Hanson Brick Company, in Stewartby, Bedfordshire, under the Knowledge Exploitation Fund (KEF) Collaborative Industrial Research Project (CIRP) programme. The mixes were formulated using a locally available industrial by-product (Ground Granulated Blastfurnace Slag — GGBS) which is activated with an alkaline (lime or Portland cement) combined with clay soil. Portland cement was not used in the formulation of the unfired stabilised masonry bricks, except as a control, which is a significant scientific breakthrough for the building industry. Another breakthrough is the fact that only about 1.5% lime was used for GGBS activation. This level of lime is not sufficient for most road construction applications where less strength values are needed and where 3–8% lime is required for effective soil stabilisation. Hence, the final pricing of the unfired clay bricks is expected to be relatively low.The laboratory results demonstrate that the compressive strength, moisture content, rate of water absorption, percentage of void, density and durability assessment (repeated 24-hour freezing/thawing cycles) were all within the acceptable engineering standards for clay masonry units. The paper also discusses on the environmental performance of the unfired clay in comparison to the bricks, used in mainstream construction of today. The bricks produced using this technology can be used for low-medium cost housing and energy efficient masonry wall construction.  相似文献   

奠边府断裂带的走滑特征及其区域构造分析     

唐渊  刘俊来  Tran My Dung  宋志杰 《地质学报》2009,83(10):1401-1414

位于越南西北部的奠边府(Dien Bien Phu)断裂,向北延伸入中国云南境内,向南进入老挝境内,走向由近N—S向向南逐渐过渡为NE—SW向,倾角陡立。沿断裂带发育3个具有不同运动学机制的第四纪盆地——婵讷(Chan Nua)盆地、莱州(Lai Chau)盆地和奠边府盆地。根据对奠边府断裂带地区ETM遥感数据进行详细解译以及野外实地考察,得到奠边府断裂具有早期的右行走滑和后期的左行走滑特征的证据;并且根据断裂两侧水系受断裂影响发生左错的程度不同,认为奠边府断裂的西盘相对于东盘较为活动,即为主动盘。奠边府断裂北延进入越南境内,与金平地区的三家河断裂相连,并继续向北并入哀牢山剪切带中。奠边府断裂现今的左行走滑与红河断裂现今的右行走滑共同组成了一组共轭断裂系。  相似文献