Salt tectonics,a controlling factor on the development of the Marseilles and Grand-Rhone sedimentary ridges,Gulf of Lions,western Mediterranean Sea     

Antonio Tadeu dos Reis  Christian Gorini  Alain Mauffret  Wiktor Weibull 《Comptes Rendus Geoscience》2004,336(2):143-150

The Marseilles (also called Marseilles/Planier) and Grand Rhone sedimentary ridges, offshore the Gulf of Lions, western Mediterranean Sea, are generated by sediment spillover funnelled by the Marseilles and Grand-Rhone canyons, respectively. We show that the Marseilles and Grand-Rhone canyon directions are tectonically conditioned by Plio-Quaternary salt-induced sea-floor relief. Overburden extension in the area created an assemblage of listric faults running parallel to the strike of the continental margin. This salt-induced topography resulted in accentuated fault scarps impacting the sea-floor morphology and forcing submarine valleys to deflect to the east. Gravity-induced extension equally influenced the morphological pattern of the valley overbanking deposits. Sediment spillover occurred on both flanks of the canyons, but because active faulting generated space accommodation for overflow deposits, it inhibited the development of typical levee morphology along the canyons' left flanks. To cite this article: A.T. dos Reis, C. R. Geoscience 336 (2004).  相似文献   

金口大峡谷地貌成因与旅游资源   总被引：7，自引：0，他引：7  

罗成德 《山地学报》2004,22(1):30-35

金口大峡谷位于大渡河下游，主要支谷有8条，皆以嶂谷地貌为特色。与大峡谷相邻的大瓦山(3236m)为我国最高的桌状山。这一区域以喀斯特地貌为主，受新构造运动影响明显，具有丰富的旅游地貌资源。  相似文献   

DESIGN OF SEDIMENT FLUSHING OUTLETS     

Prabhata K. SWAMEE 《国际泥沙研究》2002,17(4)

1 INTRODUCTION Considerable amount of sediment discharge enters in a canal at the head works. This sediment discharge is carried safely as the slopes of the canal in the head reaches are large. Subsequently, for economy, the slopes of canal are reduced in the downstream reaches. This makes the sediment concentration far excess of its carrying capacity. This excess sediment has to be removed by suitable design of a sedimentation basin. Also, one of the requirements for successful function…  相似文献   

Was Grand Banks event of 1929 a slump spreading in two directions?     

M. D. Trifunac  A. Hayir  M. I. Todorovska 《Soil Dynamics and Earthquake Engineering》2002,22(5)

This paper describes a kinematic model of tsunami generated by submarine slides and slumps spreading in two orthogonal directions. This model is a generalization of our previously studied models spreading in one direction. We show that focusing and amplification of tsunami amplitudes can occur in an arbitrary direction, determined by the velocities of spreading. This kinematic model is used to interpret the asymmetric distribution of observed tsunami amplitudes following the Grand Banks earthquake—slump of 1929.  相似文献   

高分辨率洞穴石笋中稳定同位素应用——北京元大都建立后对森林资源的破坏—δ~(13)C记录   总被引：8，自引：1，他引：7  

李红春  顾德隆  陈文寄  袁道先  李铁英 《地质论评》1998,44(5):456-463

对采自北京西山石花洞内的石笋进行了δ~(18)O,δ~(13)C和Mg/Sr分析,获得分辨率为25a的北京地区3000a以来的古气候和古环境信息。以δ~(18)O和D_(Mg/Ca)作为气候变化信息,证实石笋δ~(13)C反映了古气候变化对植被的影响。当石笋δ~(13)C值增大时,表示C_3/C_4植物比值降低,气候变干热;当石笋δ~(13)C值减小时,表示C_3/C_4植物比值升高,气候变湿冷。同时,笔者也发现了北京元大都建立以来对森林资源的破坏。在650B P至360B P,从元大都建立到明代晚期北京外城的增筑,北京西山林木被砍伐用于建筑和烧制木炭,使得这一地区的植被遭受重大改变。C_3/C_4植物的比值大幅度降低,石笋的δ~(13)C值增大3‰。尽管在此之后的气候条件有利于C_3植物的发育,但这一地区的植被没有恢复到受人类破坏前的水平。通过与历史资料对比,证明石笋中的δ~(13)C记录的确能反映C_3/C_4植物比值的分配变化,从而可以间接地反演古气候和人类活动的影响。  相似文献   

Comparison of soil salinity and solute transport for different cultivated soil types in northeastern Egypt / Comparaison de la salinité du sol et du transport de solutés pour différents types de sols cultivés du nord-est de l'Egypte     

《水文科学杂志》2013,58(2):466-478

Abstract

The soil salinity distribution and solute transport properties of three different soil types were investigated and compared within a project area in northeastern Egypt. For this purpose, dye tracer experiments and salinity sampling were carried out. The resulting salinity maps showed that the soil salinity in the cultivated western site of the project area is 8–10 times higher than that in the cultivated eastern site. However, the cultivated soil displayed significantly lower salinity with higher uniformity as compared to the uncultivated soil. The preferential flow phenomenon was less apparent in the cultivated soil. This is mainly due to tillage which disrupts the structure of the soil so that deep cracks are no longer connected to the soil surface. This reduces the risk for groundwater contamination through preferential flow. The study showed that careful and continuous monitoring of the salinity status is needed now and in the future.  相似文献   

A proposed Laramide proto-Grand Canyon     

C.A. Hill  W.D. Ranney   《Geomorphology》2008,102(3-4):482-495

The absence of “rim gravels” north of Grand Canyon and of “Canaan Peak-type” gravels south of Grand Canyon suggests that a paleocanyon, which intersected the transport of these gravels north and south, may have begun forming in the Laramide in approximately the same position as today's central Grand Canyon. This Laramide-age canyon is envisioned as having flowed generally from the SW to NE; from the Peach Springs Canyon area to Mile 197 where it was captured by karst; then along a N. 60°E joint system to the Kanab Point area where it converged with drainage coming off the west side of the Kaibab arch. From there it flowed north along the west flank of the Kaibab arch to Paleogene Lake Claron. The critical idea suggested by this proposed model is that the modern Colorado River utilized Laramide paleotopography in establishing its course through the central Grand Canyon, with younger sections of the canyon integrating with it later, in the middle to late Miocene. This paleocanyon route, in association with headward erosion from the Grand Wash Cliffs toward the Kaibab arch after 16–17 Ma, helps account for the total volume of rock eroded from Grand Canyon, which cannot be explained by present-day incision rates.  相似文献   

中国明、清时期黄河和京杭大运河地图的特征与价值     

姜莉莉  齐清文  赵锴 《地球信息科学学报》2016,18(1):39-48

黄河是中华民族的母亲河,而京杭大运河则担负着河运的重要职责,其重要性决定了古代关于黄运工程及其治理的地图数量繁多。本文旨在通过对大量明、清时期黄河、京杭大运河水利地图的梳理,对明、清时期水利地图的载体形式、表现形式和绘制特点进行剖析,并探讨其在地理学、地图学、水利学方面的应用价值和研究价值。明、清时期的黄河、京杭大运河地图,从载体形式来分,主要分为水利典籍（志书、图说）附图和绘本舆图2类：前者多为示意性地图,画法比较简单,只起到辅助说明水利典籍的作用;后者多采用山水形象画法绘制,多为长卷展开景物再现式地图,其主要特点是形象直观。其采用的“对景法”地图表现形式（即所绘黄河、京杭大运河两岸各类地物要素均朝向河流中心线）,容易引起读者的视觉共鸣,轻松构筑被描画事物的整体画面。从表现形式和绘制特点来看,明、清时期还出现了另外2类地图：计里画方类地图和经纬度实测地图,但由于其实用性和艺术性不如山水形象画法地图,因此,这2类地图在明、清并没有得到广泛普及。但从功能和价值而言,不论是长卷展开式古地图、计里画方类古地图,还是经纬度实测地图,对于古地图史、历史地理学、古代水利研究,对如今的地图、水利、地理学研究等,都是不可多得的历史瑰宝。  相似文献   

Tectonics and Seismicity of the Yarlung Tsangpo Grand Canyon Region     

Shao Cuiru  You Huichuan  Cao Zhongquan  Wang Chunyong  Tang Fangtou  Zhang Decheng  Lou Hai  Xu Guangyin  Yang Qiyan  Mei Tuo  Xie Ping  Yu Gang 《中国地震研究》2009,23(2):144-160

The Yarlung Tsangpo Grand Canyon region is located in the frontal zone of the eastern Himalayan syntaxis, where neo-tectonics and seismicity are intensive and closely related to each other. In the region, two sets of fault structures have developed, striking NNE-NE and NWW-NW, respectively. Investigation shows that they differ markedly in terms of scope, property, active times and intensity. The NWW-NW trending faults are large in size, and most are thrust and thrust strike-slip faults, formed in earlier times. The NEE-NE-strike faults are relatively small in size individually, with concentrated distribution, constituting the NNE-trending shear extensional fault zone, which is relatively younger with evident late Quaternary activities. Strong earthquakes occur mainly in the areas or zones of intensive differential movement of the Himalayas, e.g. along the deep and large fault zones around the crustal blocks. Most earthquakes of M≥7.0 are closely related to tectonics, where large-scale Holocene active faults are distributed with complicated fault geometry, or the faults of multiple directions intersect. Among them, earthquakes of M≥7.5 have occurred on the NW and NE-trending faults with a greater strike-slip component in the fault tectonic zones.  相似文献   

世界遗产视野中的京杭运河北端通惠河   总被引：1，自引：1，他引：0  

阙维民 《地理研究》2009,28(2)

通惠河是元明清时期京杭运河北端的漕运河道,但列入UNESCO世界遗产预备名录的京杭运河项目中并未包括通惠河.为了在正式申报时弥补这一缺憾,笔者于2007年底对通惠河的历史地理与遗产资源做了文献梳理、社会调研与实地勘察,结果显示:通惠河的运河遗产资源价值较高,但运河遗产资源的环境现状不容乐观,原住居民对运河遗产资源的认知程度不高,运河遗产资源的保护管理力度不够.有鉴于此,建议从三个方面加强通惠河遗产资源的保护与管理:重点保护符合申遗标准的遗产资源;综合整治遗产资源本体及其环境;传承发扬运河历史文脉与非物质遗产.  相似文献