The paleogeographic implications of loess mounds: Laizhou Bay plain     

ZHANG Zu-lu  LIU En-feng  NIE Xiao-hong  WANG Lin 《地理学报》2002,12(2):196-201

The loess mounds are a newly discovered type of landforms on the Laizhou Bay plain south of the Bohai Sea. Research shows that they were formed in the late period of the late Pleistocene when the Bohai Sea was exposed in the period of late Wümu glacial age and changed into plain. As the exposed area is not protected by vegetation, the sediments at the sea bottom are blown and transported southward by strong north winds, and deposit on the coastal plains. As thick loess is accumulated, the loess mound landforms are formed in the direction of down wind.  相似文献   

Evolution of orogenic wedges and continental plateaux: insights from crustal thermal–mechanical models overlying subducting mantle lithosphere     

O. Vanderhaeghe  S. Medvedev  P. Fullsack  C. Beaumont  R. A. Jamieson 《Geophysical Journal International》2003,153(1):27-51

  相似文献   

A high-resolution magnetotelluric survey of the Iapetus Suture Zone in southwest Scotland   总被引：1，自引：0，他引：1  

Sebastian Tauber  Roger Banks  Oliver Ritter  Ute Weckmann 《Geophysical Journal International》2003,153(3):548-568

  相似文献   

Gorringe Ridge gravity and magnetic anomalies are compatible with thrusting at a crustal scale     

J. Galindo-Zaldívar  A. Maldonado  A. A. Schreider 《Geophysical Journal International》2003,153(3):586-594

  相似文献   

An integrated global model of present-day plate motions and plate boundary deformation   总被引：18，自引：0，他引：18  

Corné Kreemer  William E. Holt  A. John Haines 《Geophysical Journal International》2003,154(1):8-34

  相似文献   

Exploring some relationships between biological soil crusts, soil aggregation and wind erosion   总被引：5，自引：0，他引：5  

David J. Eldridge  John F. Leys 《Journal of Arid Environments》2003,53(4):457-466

A portable wind tunnel was used to test the contribution of biological and physical elements to overall soil aggregation on a soil dominated by biological soil crusts in south-eastern Australia. After moderate disturbance and simulated wind erosion, 90% of surface aggregates on the loamy soil and 76% on the sandy soil were dominated by biological elements (cryptogams). Lower levels of biological bonding were observed on the severely disturbed treatment. Linear regression indicated a significant positive relationship (r²=0·72) between biological soil crust cover and dry aggregation levels greater than 0·85mm. To maintain sediment transport below an erosion control target of 5gm⁻¹s⁻¹ for a 65kmh⁻¹ wind at 10m height, a crust cover of approximately 20% is required. When a multiple regression model which sequentially fitted biological crust cover and dry aggregation greater than 0·85mm was applied to the data, dry aggregation accounted for more of the variation in sediment transport rate than biological crust cover. These data were used to develop a conceptual model which integrates crust cover and dry aggregation, and provides a useful framework within which to predict the likely impacts of changes in soil crust cover and aggregation.  相似文献   

Salt tolerance of Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crust, was enhanced by exogenous carbohydrates     

Lanzhou Chen  Dunhai Li  Yongding Liu 《Journal of Arid Environments》2003,55(4):381

Microcoleus vaginatus isolated from a desert algal crust of Shapotou was cultured in BG-11 medium containing 0.2 mol l⁻¹ NaCl or 0.2 mol l⁻¹ NaCl plus 100 mg l⁻¹ sucrose, extracellular polymeric substances (EPS) or hot water-soluble polysaccharides (HWP), respectively. Photosynthetic oxygen evolution rates, photosystem II activity (Fv/Fm) and dark respiration of NaCl-stressed cells were enhanced significantly by the added sucrose or EPS under salt stress conditions (0.2 mol l⁻¹ NaCl). Compared with cells treated with salt alone, sodium contents in cells reduced significantly; the content of cellular total carbohydrate did not change, and intracellular sucrose, water-soluble sugar increased significantly following the addition of exogenous carbohydrates. Sucrose synthase (SS) activity of NaCl-stressed cells increased following the addition of sucrose, and sucrose phosphate synthase (SPS) activity of NaCl-stressed cells increased following the addition of exogenous sucrose, EPS or HWP compared with cells stressed with NaCl only. The results suggested that the extruded EPS might be re-absorbed by cells of M. vaginatus as carbon source, they could increase salt tolerance of M. vaginatus through the changes of carbohydrate metabolism and the selective uptake of sodium ions.  相似文献   

藏北新生代两套钾玄质火山岩系列地球化学特征   总被引：8，自引：2，他引：8  

刘燊  胡瑞忠  迟效国  李才  冯彩霞 《矿物岩石》2003,23(2):66-71

岩石学和元素地球化学特征研究表明，藏北新生代自南向北沿可可西里岩带和喀喇昆仑—玉门岩带出露有两套钾玄质系列火山岩。它们富集大离子亲石元素(LILE)和轻稀土(LREE)及明显亏损Nb—Ta—Ti，同时具有板内和岛弧(陆弧)的双重特征。源区来源于可能与俯冲带流体有关的相似交代富集地幔，成岩过程主要经历了低度(＜10％)辉石分离结晶作用，同时，源区伴有地壳物质的混染作用。  相似文献   

华南地区地壳速度结构分析   总被引：18，自引：0，他引：18       下载免费PDF全文

郑圻森  朱介寿  宣瑞卿  蔡学林 《沉积与特提斯地质》2003,23(4):9-13

笔者利用地球物理综合剖面上获取的P波速度值，对岩石圈地壳进行分层研究，划分出上、中、下地壳。按照大地构造单元进行数据的归类总结，计算出地壳各层平均速度和厚度值，以及地壳的平均速度和厚度值，最终通过所取得的数据资料的分析研究，探讨地球内部结构的动力学过程。  相似文献   

南秦岭下地壳组成及岩石圈的拆离俯冲作用   总被引：3，自引：3，他引：3       下载免费PDF全文

路凤香王春阳胡宝群吴其反  郑建平 《中国地质》2003,30(2):113-119

根据新提供的Pb同位素组成及岩石地球化学研究成果，本文进一步证实了位于北秦岭北界的明港地区发育的早中生代安山玄武质火山角砾岩岩筒所携带的下地壳捕虏体属于南秦岭。所恢复的南秦岭下地壳剖面自下而上为：底侵成因的变辉长岩-基性麻粒岩(其中含有榴辉岩及辉石岩的透镜体)-酸性麻粒岩。秦岭造山带总体的岩石因模型为：南秦岭(扬子块体)向北拆离俯冲，北秦岭地壳向华北仰冲，华北岩石因呈楔状插入秦岭造山带，拆离面约在中、下地壳之间。南秦岭俯冲岩片延伸的范围在平面上有可能达到400km。  相似文献