兰州—民和盆地河口群沉积相和岩石磁化率——祁连山白垩纪隆升的记录   总被引：1，自引：0，他引：1  

唐玉虎  戴霜  黄永波  朱强  方小敏  胡鸿飞  刘俊伟  孔立  赵杰  刘学 《地学前缘》2008,15(2):261-271

研究白垩纪祁连山构造隆升过程对认识青藏高原形成及其环境效应具有重要意义,兰州—民和盆地连续出露的河口群沉积物较好地记录了早白垩世祁连山隆升过程。河口群从下向上由冲积扇、扇三角洲、辫状河、滨湖、滨浅湖、半深湖、三角洲7个沉积相体系组成;综合分析沉积相时空演化、砾石成分及古水流方向统计和岩石磁化率测量,揭示出早白垩世祁连山经历了3期隆升过程:早期(约143～123Ma)快速强烈隆升阶段,此时祁连山东段开始逐渐断陷下沉,盆地沉积了冲积扇至滨浅湖相沉积体系的砾岩、砂岩和泥岩,岩石磁化率值总体偏低,隆升速度较快;中期(约123～113Ma)稳定隆升阶段,湖盆面积达到最大,沉积物以半深湖相泥岩为主,磁化率值总体偏高,隆升速度较慢;晚期快速隆升阶段,约从113Ma开始,祁连山隆升速度加快,湖盆萎缩,沉积了以三角洲相为主的泥岩和砂岩,磁化率值总体偏低,直至109Ma以后,盆地回返,祁连山地区整体抬升遭受剥蚀。  相似文献   

渝北—川东地区黄龙组古岩溶储层稳定同位素地球化学特征   总被引：10，自引：0，他引：10  

郑荣才  胡忠贵  郑超  陈守春  戴荔果 《地学前缘》2008,15(6):303

石炭系黄龙组碳酸盐岩古岩溶储层是渝北—川东地区最重要的天然气储集类型之一。依据岩溶岩的结构特征,将黄龙组岩溶岩系划分为弱溶蚀岩溶岩、中等溶蚀多孔状岩溶岩、强溶蚀角砾状岩溶岩和强溶蚀交代的次生灰质岩溶岩等4种岩溶岩类型,和淡水方解石与白云石两种胶结物类型。以基质岩为对比参照物,对各类岩溶岩和胶结物的碳、氧、锶稳定同位素分析对比研究结果表明,不同成因类型、溶蚀强度、结构和成分的岩溶岩与胶结物的碳、氧、锶稳定同位素地球化学特征各异,其形成、演化和分布规律明显受古地理背景、流体性质、流体来源以及同位素分馏效应控制。依据岩溶岩系的结构和地球化学特征的差异性,可总结出4个主要特征:(1)伴随岩溶强度加大,δ13C表现向低值方向弱偏移,而δ18O负偏移较强烈;(2)87Sr/86Sr比值出现由渗流-活跃潜流带的正偏移,至静滞潜流带转化为强烈负偏移的演化趋势;(3)对应古岩溶系碳、氧、锶稳定同位素演化,古岩溶储层的物性出现由差变好至重新变差的对应变化关系;(4)淡水白云石结晶沉淀过程中可能具有对87Sr有很强"捕获"能力的锶同位素正偏移分馏效应。  相似文献   

Modeling Groundwater in Multimodal Porous Media with Localized Decompositions     

Chaocheng Huang  Zhenxue Dai 《Mathematical Geosciences》2008,40(6):689-704

In the present paper, a new stochastic framework is introduced to decompose random variables. This decomposition method is shown to better capture and reflect the medium heterogeneity for multimodal porous media than the classical Reynolds decomposition does. In particular, with this decomposition method, the variance of log conductivity is decomposed into two parts. The first one measures the mean differences of log conductivity across different units having high contrasting conductivity. The second part measures the variation of log conductivity arisen within individual units. Based on this localized decomposition, a new stochastic model is proposed for flow in a highly heterogeneous porous media. This stochastic model shall produce much sharper approximations under the assumption that only the second part of the variance of log conductivity is small. Therefore, the proposed model can partially overcome the assumption of small composite variance for log conductivity in current theory for both flow and transport.  相似文献   

ECMWF模式对陕西2016年春夏季气温预报性能评估     

王丹  王建鹏  潘留杰  何林  程路  戴昌明  胡皓  白庆梅 《气象科技》2018,46(1):92-101

利用2016年春、夏季节陕西99个国家站的气温逐1 h观测数据,对ECMWF高分辨率数值模式对陕西国家站0~72 h逐3 h和78~240 h逐6 h的气温预报性能进行评估。结果表明,陕西大部分地区,气温预报误差≤1 ℃和≤2 ℃的准确率在72 h之前分别为30%~50%和55%~85%,96 h之后分别为10%~30%和25%~55%,夏季的准确率高于春季,20:00起报的准确率略高于08:00起报。随着预报时效的增加,模式的气温预报能力和稳定性波浪式下降,日变化特征明显,23:00至次日11:00时段的预报能力和稳定性好于14:00—20:00时段。模式的气温预报值与观测值有很好的相关性,但是模式和实际观测站的地形高度差异会对气温预报质量产生较大影响。基于气温垂直变率和模式与实际观测站的地形高度差异进行的高度差订正,可以适当提高模式的气温预报水平,文中提出的几种气温预报的高度差订正方法,对陕西大部分地区的气温预报为正订正效果,但还存在一些问题,有待进一步研究。  相似文献   

Observed spatiotemporal variation of three-dimensional structure and heat/salt transport of anticyclonic mesoscale eddy in Northwest Pacific     

Dai  Jun  Wang  Huizan  Zhang  Weimin  An  Yuzhu  Zhang  Ren 《中国海洋湖沼学报》2020,38(6):1654-1675

Journal of Oceanology and Limnology - As in-situ observations are sparse, targeted observations of a specific mesoscale eddy are rare. Therefore, it is difficult to study the three-dimensional...  相似文献   

Can Langmuir Circulations Solve the Problem of Insufficient Upper-Ocean Mixing?     

Huang  Chuanjiang  Qiao  Fangli  Dai  Dejun 《中国海洋大学学报(英文版)》2020,19(4):761-771

Insufficient vertical mixing in the upper ocean during summer is a common problem of oceanic circulation and climate models. The turbulence associated with non-breaking waves is widely believed to effectively solve this problem. In many studies, non-breaking surface wave processes are attributed to the effects of Langmuir circulations(LCs). In the present work, the influences of LCs on the upper-ocean thermal structure are examined by using one-and three-dimensional ocean circulation, as well as climate, models. The results indicated that the effect of vertical mixing enhanced by LCs is limited to the upper ocean. The models evaluated, including those considering LC effects alone and the combined effects of LCs and wave breaking, failed to produce a reasonable summertime thermocline, resulting in a large cold bias in the subsurface layer. Therefore, while they can slightly reduce the biases of mixed layer depths and sea surface temperatures in models, LCs are insufficient to solve the problem of insufficient vertical mixing. Moreover, restriction of non-breaking surface wave-induced processes in LCs may be questionable.  相似文献   

Variations in the potential climatic suitability distribution patterns and grain yields for spring maize in Northeast China under climate change     

Jin Zhao  Xiaoguang Yang  Zhijuan Liu  Shuo Lv  Jing Wang  Shuwei Dai 《Climatic change》2016,134(1-2):29-44

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Seasonal evaluation of evapotranspiration fluxes from MODIS satellite and mesoscale model downscaled global reanalysis datasets     

Prashant K. Srivastava  Dawei Han  Tanvir Islam  George P. Petropoulos  Manika Gupta  Qiang Dai 《Theoretical and Applied Climatology》2016,124(1-2):461-473

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Effects of urban land-use change in East China on the East Asian summer monsoon based on the CAM5.1 model     

Hongyun Ma  Zhihong Jiang  Jie Song  Aiguo Dai  Xiuqun Yang  Fei Huo 《Climate Dynamics》2016,46(9-10):2977-2989

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On the variability of near-bed floc size due to complex interactions between turbulence,SSC, settling velocity,effective density and the fractal dimension of flocs     

Yang Yang  Ya Ping Wang  Chunyan Li  Shu Gao  Benwei Shi  Liang Zhou  Dandan Wang  Gaocong Li  Chen Dai 《Geo-Marine Letters》2016,36(2):135-149

Interactions between turbulence, suspended sediment concentration (SSC), settling velocity, effective density, fractal dimension, and floc size were studied on the tide-dominated, muddy coastal shelf of the southwestern Yellow Sea, China. The measurements were carried out in July 2013 at two sites located in water depths of 21.2 and 22.1 m. Negative correlations were observed between shear rate, SSC, effective density, and mean floc size, which supports the results of previous numerical, experimental, and field studies. A significant positive correlation was observed between near-bed SSC and shear rate, an indication that SSC variations are controlled by turbulence and re-suspension. In addition, significant linear relationships were found between settling velocity and other parameters (floc size, turbulence, SSC, effective density, and fractal dimension) at the two sites, indicating that the controlling factors on settling velocity are spatially variable. Principal component analysis was applied to determine the relative importance of turbulence, flocculation ability, and SSC as controls on floc size in situ. The relative contributions of turbulence, flocculation ability, and SSC to floc size (at both sites) were ~33.0%, 30.3%, and 29.7%, respectively, this being a new field-based quantitative analysis of the controls on floc size. The findings demonstrate that, in nature, flocculation ability affects floc size to the same degree as turbulence and SSC. Therefore, predictions of floc size in coastal marine environments require constraints not only on turbulence and SSC, but also on flocculation ability.  相似文献