Organic carbon isotope gradient and ocean stratification across the late Ediacaran-Early Cambrian Yangtze Platform     

WANG XinQiang  SHI XiaoYing  JIANG GanQing  TANG DongJie 《中国科学:地球科学(英文版)》2014,57(5):919-929

Organic carbon isotope(δ13Corg) data from two well-preserved sections across a shallow-to-deep water transect of the late Ediacaran-Early Cambrian Yangtze Platform in South China show significant temporal and spatial variations. In the shallow-water Jiulongwan-Jijiapo section, δ13Corg values of the late Ediacaran Dengying Formation range from -29‰ to -24‰. In the deep-water Longbizui section, δ13Corg values from time-equivalent strata of the Dengying Formation are mostly between –35‰ and -32‰. These new data, in combination with δ13Corg data reported from other sections in South China, reveal a 6‰–8‰ shallow-to-deep water δ13Corg gradient. High δ13Corg values(-30‰) occur mostly in shallow-water carbonate rocks, whereas low δ13Corg values(-32‰) dominate the deep-water black shale and chert. The large temporal and spatial δ13Corg variations imply limited buffering effect from a large dissolved organic carbon(DOC) reservoir that was inferred to have existed in Ediacaran-Early Cambrian oceans. Instead, δ13Corg variations between platform and basin sections are more likely caused by differential microbial biomass contribution to total organic matter. High δ13Corg values(-30‰) documented from shallow-water carbonates are within the range of typical Phanerozoic δ13Corg data and may record the isotope signature of organic matter from primary(photosynthetic) production. In contrast, low δ13Corg values(-32‰) from deep-water sections may have resulted from higher chemoautotrophic or methanotrophic biomass contribution to bulk organic matter in anoxic environments. The δ13Corg data provide indirect evidence for ocean stratification and episodic chemocline fluctuations in the Ediacaran-Early Cambrian Yangtze Platform.  相似文献   

Hydrogeochemical stratification of the unconfined Samobor aquifer (Zagreb,Croatia)   总被引：1，自引：0，他引：1  

Tatjana Vlahović  Andrea Bačani  Kristijan Posavec 《Environmental Geology》2009,57(8):1707-1722

In the western part of the city of Zagreb, Croatia, hydrogeochemical and isotopic investigations of the Samobor aquifer were carried out with the aim of determining the differences in hydrogeochemical characteristics at increasing aquifer depths. The aquifer comprises 40-m thick gravelly–sandy deposits, with lenses and interlayers of silt and clay. The analyses have proven that with increasing aquifer depth, there are decreases in groundwater temperature and the values of electrical conductivity and increases in the sodium, iron and manganese concentrations. The δ¹³C distribution shows an evident increase in biogenic carbon concentrations with increasing aquifer depth. The measured specific ¹⁴C activities showed that the deeper part of the aquifer is characterized by slow water exchange, while the shallower part is influenced by current recharge, although the pumping wells located on the well-field downstream penetrate the aquifer fully. A direct exchange of water from the Sava River and groundwater occurs in the near vicinity of the river. This exchange weakens further away, while the difference in hydrogeochemical characteristics between the Sava River water and groundwater increases.  相似文献   

用测井曲线自动划分层序地层研究   总被引：15，自引：2，他引：13  

邵才瑞  李洪奇  张福明  张元福  吕希学 《地层学杂志》2004,28(4):321-325

无论在基础地质研究还是在指导沉积矿产资源勘查中 ,层序地层划分都具有重要的作用。利用测井资料进行人工层序地层划分是一项重要工作 ,但效率较低。根据层序地层划分的原则 ,采用频谱分析和砂泥岩比值方法设计了层序地层划分的自动算法 ,在济阳坳陷部分区块进行了应用 ,取得了较好的效果 ,为层序地层划分提供了有效的工具。  相似文献   

Role of mean circulation,tides, and waves in the transport of bottom sediment on the New Zealand continental shelf   总被引：1，自引：1，他引：0  

L. Carter  R. A. Heath 《新西兰海洋与淡水研究杂志》2013,47(4):423-448

Evaluation of velocity data on water movements over the New Zealand continental shelf has revealed that the mean circulation by itself is too slow to induce transport of bottom sediments. Tides generally have higher velocities, but are still not the main transporting agent except in the tide‐dominated Cook and Foveaux. Straits. Waves have the potential to stir sediments on the inner and middle shelf (less than about 70 m deep) during annual storms, and probably down to 130 m depth during the maximum 25‐y storm.

For sediment transport to take place, energies of at least two of the major water movements would have to complement one another. Optimum conditions for transport probably occur during storm periods when wave‐suspended sediment is readily moved by tides and the mean circulation.

The direction of transport is mainly along the continental shelf and is largely in response to prevailing weather patterns coincident with the direction of the mean circulation and strongly reinforced by the appropriate phase of the tide.  相似文献   

郑徐高铁开封段地面沉降分层监测方法     

张丹  郝亚东 《测绘通报》2017,(11):77-79

高铁沿线施工期间引起地面沉降的因素错综复杂、相互影响,本文提出通过对沉降区域地下水位、孔隙水压力等进行分层观测,根据分层观测得到地下水位变化、孔隙水压力变化等数据,并采用回归分析法构建了沉降区域地面沉降与诸影响因子的关联模型,通过对郑徐客运专线开封段进行的地面沉降监测量与同时采用二等精密水准测量得到的监测点沉降量进行对比分析,结果表明本方法的有效性和可靠性。  相似文献   

磨刀门河口环流与咸淡水混合层化机制   总被引：1，自引：0，他引：1       下载免费PDF全文

吕紫君  冯佳佳  郜新宇  汪玉平  张梦茹  孔俊 《水科学进展》2017,28(6):908-921

为研究磨刀门盐水混合层化特征,基于SCHISM模型,建立了三维盐度数值模型,根据实测资料对其进行验证。结合水体势能异常理论,对枯季磨刀门河口混合层化的时空变化特征及深槽与浅滩的层化机制差异进行分析。结果表明:磨刀门河口小潮时水体层化最强,中潮时水体层化最弱,且拦门沙至挂定角段水体层化始终较强。磨刀门深槽水体层化主要受纵向平流、纵向水深平均应变和垂向混合影响,而浅滩水体层化则受横向平流、横向水深平均应变和垂向混合影响;磨刀门河口表、底层水体湍动能耗散率较高,而中间水层存在低耗散区,且涨潮时湍动能耗散率比落潮时大。  相似文献   

阶层化背景下的就业空间——以常住人口与流动人口为例   总被引：1，自引：0，他引：1  

林耿  王炼军 《地理研究》2010,29(6):1069-1082

采用2000年第五次人口普查数据,以市辖区(县、市)为基本地理单元,对广东省的21个地级市133个样本进行阶层化背景下的就业空间研究。通过对常住人口和流动人口的就业构成和就业类型区的分析发现:(1)与流动人口相比,常住人口就业空间的分异更显多元化,其就业的体制内特征更为明显。两类人口就业空间没有形成社会极化结果,收入与职业的极化并未导致社会空间极化的出现,但也存在着类社会极化的特征。(2)常住人口和流动人口的就业构成具有中产化特征,在空间上具有中心城市指向性。而就业差异是否导致常住人口和流动人口之间的结构性阶层分异,则需进行后续的深入论证。  相似文献   

Observations of internal tidal waves in the isolated seasonally stratified region of the western Irish Sea     

J.A.M. Green  J.H. SimpsonS.A. Thorpe  T.P. Rippeth 《Continental Shelf Research》2010

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Social construction functions of consumption space under stratification: The case of Guangzhou     

Geng Lin  Lianjun Wang  Xiaoying Zhang 《中国地理科学(英文版)》2010,20(5):450-460

As Chinese cities rapidly transformed themselves into consumerist societies, the relationship between consumers and consumption space under stratification has become a new research area in the field of urban social geography. Based on a consumer behavior analysis, this study explores the relationship between consumption space and the social strata of consumers in typical shopping malls in Guangzhou where the first shopping mall in China was built. The result shows that shopping malls have performed significant constructive functions of organizing consumers from different social classes into different consumption space. For middle- and upper-class consumers, the function of shopping malls centers on utilitarian consumption, identity recognition, and identity construction; whereas for lower-class consumers, its function revolves around pleasure and enjoyment. The symbolism of consumption space is the underlying reason for shopping malls to have their social constructive function. The findings of this research suggest that: 1) a shopping mall is a productive consumption space and a geographical space with subjectivity; 2) the micro-location of a shopping mall has social construction function; and 3) symbolic consumption is the core of social construction.  相似文献   

Stability of shear flows with multilayered density stratification and monotonic velocity profiles having no inflection points     

S. M. Churilov 《地球物理与天体物理流体动力学》2016,110(1):78-108

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