渭河中游全新世黄土剖面光释光测年及记录的古洪水事件   总被引：1，自引：0，他引：1  

王恒松  黄春长  周亚利  庞奖励  查小春  顾洪亮 《地质学报》2012,86(6):994-1004

通过对渭河流域进行广泛的考察,在中游咸阳附近一处阶地发现保存完好的全新世黄土-古土壤剖面里夹有古洪水滞流沉积层,对其进行了年代学和沉积学研究。对于采集的全新世地层样品,进行粒度、磁化率测量分析,证明所夹沉积物是典型的古洪水滞流沉积物,该层记录了古洪水事件发生的气候水文信息。应用红外后蓝光的SAR光释光测年技术,获得该剖面9个OSL年龄值,确定渭河在距今3.2～2.8ka之间为一个洪水多发时期,并建立了渭河古洪水事件的年代序列。这一结果揭示了古洪水的频发与全新世中期向晚期过渡的转折时期,气候由温湿向干旱化发展,大气系统失稳,气候变化剧烈,降水量异常变化,变率增大,是导致渭河流域特大古洪水多发的主要原因。  相似文献   

Hydrological simulation of a conservation bench terrace system in a subhumid climate     

VISHWA NATH SHARDA  JAGIR SINGH SAMRA 《水文科学杂志》2013,58(4):549-561

Abstract

A finite element model to simulate runoff and soil erosion from agricultural lands has been developed. The sequential solutions of the governing differential equations were found: Richards' equation with a sink term for infiltration and soil water dynamics under cropped conditions; St Venant equation with kinematic wave approximation for overland and channel flow; and sediment continuity equation, for soil erosion. The model developed earlier has been improved to simulate erosion/deposition in impoundments and predicted and observed soil loss values were in reasonably good agreement when the model was tested for a conservation bench terrace (CBT) system. The finite element model was extensively applied to study the hydrological behaviour of a CBT system vis-à-vis the conventional system of sloping borders. The model estimates runoff and soil loss reasonably well, under varying conditions of rainfall and at different crop growth stages. The probable reasons for discrepancies between observation and simulation are reported and discussed. Sensitivity analysis was carried out to study the effect of various hydrological, soil and topographical parameters, such as ratio of contributing to receiving areas, weir length, depth of impoundment, slope of contributing area, etc. on the flow behaviour in a CBT system.  相似文献   

渭河盆地的水系与现代构造运动     

苏生瑞 《地球科学与环境学报》1991,(1)

通过卫星象片解释、实地调查测量和查阅历史文献,本文较全面地研究了渭河盆地的水系及其所反映的现代构造运动特征。水系平面组合形态、渭河河型、水系转折及冲沟错位、河流密度、渭河河床的迁移、历史水涝灾害都一致地反映本区现代构造运动继承了第四纪以来的特点。水系历史演变又表明现代构造运动具有周期性。据水系错位和河流流向的统计分析确定本区现代构造应力场主压应力方向为N50°～60°E。本文最后还讨论了根据水系研究现代构造运动的意义以及应注意的问题。  相似文献   

渭河盆地中土层场地对地震动的放大作用   总被引：11，自引：1，他引：10       下载免费PDF全文

王海云 《地球物理学报》2011,54(1):137-150

土层场地对地震动的影响较大,建(构)筑物的选址及其抗震设防必须考虑土层场地的放大作用,以避免或减轻其震害.汶川地震中,布设在渭河盆地中的数字强震动台网共有27个台站(包括2个基岩台站和25个土层台站)获得良好的主震加速度时程.利用这些加速度时程,选择汤峪台做为参考场地,基于考虑几何衰减的传统谱比法分析研究了25个土层场...  相似文献   

陕西渭河盆地固市凹陷渭热2井组 甲烷气成因及其意义   总被引：1，自引：0，他引：1  

李玉宏  王行运  韩伟  宫振奇 《地质通报》2013,32(11):1790-1797

渭河盆地固市凹陷渭热2井组甲烷气的成功点火,再一次引起人们对渭河盆地油气资源前景的关注。渭热2井组及邻区7口井天然气组分、甲烷C同位素等分析指标显示,该区甲烷气具有2种成因类型,浅部气层为新近系张家坡组生物成因气,中深部天然气来自前新生界煤型热解-裂解气;伴生CO2气为有机成因。地质分析认为,渭河盆地固市凹陷具有良好的新生界生物气资源前景,前新生界煤系地层也是渭河盆地重要的潜在烃源岩,表明渭河盆地具有开展进一步油气调查的资源基础。  相似文献   

沧东断裂山岭子东段地质构造分析     

王继革  易志东  靳宝珍  贾志  岳丽燕  魏永民 《华北地质》2013,(3)

依据钻井、MT测深、地震剖面资料对沧东断裂山岭子东段地质构造进行了研究,认为该段沧东断裂断面形态呈“阶形”,自沧县隆起至北塘凹陷由高、中、低三个台阶组成断阶构造。中生代白垩纪末期,在南东-北西向压扭应力作用下形成褶皱及逆断层,新生代古近纪反转为正断层,断阶带内发育北东及北北西向共轭剪切断层,它们是沟通不同热储层的重要通道。  相似文献   

天山北缘河流阶地形成及构造变形定量分析   总被引：4，自引：1，他引：4  

袁庆东  郭召杰  张志诚  吴朝东  方世虎 《地质学报》2006,80(2):210-216

新生代以来,北天山山前发育了3排冲断褶皱带。新生代晚期一系列河流普遍穿过这3排冲断褶皱带并发育了三级河流阶地。在最新构造活动的影响下,河流阶地普遍发生变形,遭受抬升。利用光释光及14C年代学方法确定了塔西河三级阶地的形成年龄,并实际测量了三级阶地的高程。结果表明吐谷鲁背斜的构造抬升速率在32．85-28．75 ka问为9．50-12．57 mm／a,12-13 ka间为9．67-14．5 mm／a,全新世则增至10．79-23．44mm／a,天山基底的平均隆升速率达到3．39-3．86mm／a。通过对天山最高一级夷平面、野外实测侏罗纪地层高程及天山发育的煤层的相对隆升速率的研究则表明天山自24 Ma以来平均的隆升速率约为0．085-0．146 mm／a。结合对北天山其他主要河流阶地的观察及研究可以看出自晚更新世一全新世以来,天山北缘的最新构造活动具有不断加快的特征。  相似文献   

The Balderton Sand and Gravel: Pre-Ipswichian cold stage fluvial deposits near Lincoln,England     

Allan Brandon  Michael G. Sumbler 《第四纪科学杂志》1991,6(2):117-138

The Balderton Terrace marks a former course of the River Trent between Newark and the Lincoln Gap. The principal deposit, the Balderton Sand and Gravel, is interpreted as a braided river sediment. Ice wedge casts truncated by intraformational erosion surfaces at many levels indicate syndepositional permafrost. Remnant cover deposits overlying the Balderton Sand and Gravel include the partly aeolian Whisby Sand. Locally, both the upper part of the Balderton Sand and Gravel and the cover deposits exhibit features indicative of temperate climate pedogenesis. All these deposits are affected by subsequent cryoturbation. On the basis of these features and the geomorphological and topographical relationship to other terrace deposits of the area, the Balderton Sand and Gravel and Whisby Sand are regarded as post-Hoxnian and pre-lpswichian, i.e. Wolstonian. Electron spin resonance age determinations for fossil elephant teeth and amino acid analyses on molluscs from the Balderton Sand and Gravel suggest correlation with Oxygen Isotope Stage 6. The Balderton Sand and Gravel has yielded a cold-climate mammalian fauna dominated by woolly mammoth and woolly rhinoceros, though rarer species suggest periods of milder climate. Silts from channels near the base of the deposit have produced pollen, mollusc, ostracod and beetle assemblages also indicating a cold climate.  相似文献   

New geomorphic evidence for anticlinal growth driven by blind-thrust faulting along the northern Marche coastal belt (central Italy)   总被引：2，自引：0，他引：2  

Paola Vannoli  Roberto Basili  Gianluca Valensise 《Journal of Seismology》2004,8(3):297-312

The Northern Marche coastal belt is characterised by a series of NW-SE trending, NE verging folds forming the easternmost edge of the Apennines thrust front. Several geomorphic features suggest that the folds are still growing and hence that the thrust front is active. The occurrence of several historical and instrumental earthquakes (e.g. 1672, 1690, 1786, 1875, 1916, 1930, 1972, all having M_e 5.2) suggests that the thrust faults are also seismogenic.We performed a geomorphological analysis to identify and characterise the faults driving the active folds. Our approach assumes that anomalous drainage patterns and deformed Middle-Late Pleistocene alluvial and coastal terraces are indicators of the vertical component of tectonic strain. We identified, mapped and correlated with sea-level fluctuations a sequence of alluvial and coastal terraces. Longitudinal profiles of six rivers (Conca, Foglia, Metauro, Cesano, Misa, and Esino) show that terraces (1) consistently converge downstream, suggesting that they result from regional uplift that dies out near the coast, and (2) some are slightly warped where they cross anticline axes. We interpreted as coastal terraces several land-surface remnants arranged parallel to the present coastline. Lower remnants clearly top off gently landward-tilted coastal deposits. Reconstructed coastal terraces also seem to be tectonically warped.Our results help characterise the geometry and segmentation of a system that generated the largest earthquakes of the region and suggest the loci of potential seismic gaps. We conclude that the earthquake potential of the densely populated northern Marche coastal belt may be substantially higher than currently estimated.  相似文献   

渭河盆地地温场分布规律及其控制因素     

任战利  刘润川  任文波  祁凯  杨桂林  崔军平  杨鹏  张园园 《地质学报》2020,94(7):1938-1949

本文以渭河盆地地温场为研究对象,在收集补充新地热井资料及分析测试样品的基础上,通过盆地深部结构、构造特征、地温场特征、热储层特征、地热资源量等分析,建立了盆地不同岩性岩石热导率与深度关系图版,确定了盆地地温场变化规律及地热田控制因素,提出了渭河盆地地热田形成模式。评价了盆地地热资源有利区,为盆地后续的开发利用提供了理论支持。研究认为渭河盆地热地温梯度分布在2.34～5.85℃/100m之间,平均地温梯度为3.50℃/100m,代表性大地热流68.33mw/m~2,地温梯度及不同深度地层温度具有东高西低、南高北低的特点。热导率总体上具有随深度的增加,逐渐增大的规律,热导率随深度增加主要受压实程度增强控制。相同深度条件下泥岩热导率最低,砂岩热导率居中、白云岩热导率最高。渭河盆地主要为层状地热田,盆地内地热通过热传导及热对流两种方式进行传递,以热传导为主。渭河盆地地热资源丰富,热储层可分为三种类型:①新生界砂岩孔隙型;②下古生界碳酸盐岩岩溶型;③断裂型。渭河盆地地热资源有利区主要分布于西安凹陷、固市凹陷。盆地地温场及地热田分布与莫霍面、软流圈上隆、岩石圈厚度减薄的深部背景密切相关,主要受地热传导和深大断裂热对流控制,是岩石圈深部结构、盆地构造、基底岩性、储盖组合等多因素共同作用下形成的。最后结合当前渭河盆地地热资源开发利用现状及存在问题,提出了地热开发利用建议。  相似文献