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1.
黄河中游河流阶地的对比及阶地系列形成中构造作用的多层次性分析 总被引：22，自引：0，他引：22
黄河在流经青藏市原东北缘海原－同以弧形构造区的过程中,发育了多达10－21组的斯座和侵蚀型阶地,其最大拔河高度为40lm,最高阶地的发育年代为1．57MaBP。通过对该区米家山、车木峡和黑山峡河口3处黄河阶地以及我国北方大范围内河流阶地的对比分析发现,河流阶地系列形成中在构造作用上具有多层次性特征,即它包含了不同范围或规模和不同级次构造隆升作用所导致的阶地。研究区的黄河阶地系列可以划分为3个层次。其中,第一层次的阶地共有6级,为我国北方大范围内同期形成的阶地,它们代表1．6Ma以来青藏高原阶段性隆升的次数,其隆升幅度由西向东逐渐减小;第二层次的阶地共有5级,为海原－天景山构造区内同期发育的阶地,它们代表1．6Ma以来该构造区本身自隆升的次数和幅度;第三层次阶地为发育在米家山东坡的10级不同期阶地,它们代表1．6Ma以来海原构造山地独自的抬升的次数和幅度。阶地发育时间与黄土－古土壤序列的对比还表明,反映青藏高原大范围构造隆升的第一层次阶地与气候变化之间有很好的可对比性,其形成年代均与相应古土壤发育时间的间冰期对应,暗示导致河流下切的在范围构造抬升与强干冷期后同样可导致河流下切的气候暖湿期紧密相关,它们共同组成了构造－气候旋回。第二层次和第三层次阶地的形成时间与气候变化之间无统一特定的关系,显示它们的形成更主要的受控于天景山块体和海原构造带的隆升作用。因此,研究区的河流阶地主要可分为2种成因类型。一种是在大范围构造抬升和气候变化联合作用下形成的构造－气候旋回阶地,此类阶地分布范围广,具有区域间的可对比性;另一种是以局部构造抬升为主导因素形成的脉动式构造旋回阶地,此类阶地的分布受 控于活动构造带,在构造区带内自成体系,不具有区域间的可对比性。 相似文献
2.
最近14 Ma青藏高原东北缘阶段性隆升的地貌证据 总被引：33，自引：2，他引：33
对青藏高原东北缘代表性的河流阶地-风成堆积序列进行了沉积学、地貌学和年代学的综合调查研究, 获得了最近14 Ma以来高原东北缘阶段性隆升的新证据和新认识. 湟水流域西宁-互助地区至少发育了11级典型的河流阶地(除第1级阶地T1外, 全部为基座阶地). 测试了阶地上覆风成黄土-红粘土序列的1030块古地磁样品、16块释光样品和4000多个粉末样品, 结合地貌发育和地层结构分析表明, T11, T10, T8, T7, T3, T2和T1分别形成于距今约14, 11.3, 1.55, 1.2, 0.15, 0.07和0.01 Ma. 基于沉积物分析和地貌发育过程的研究证实, 这里的河流阶地以构造抬升驱动为主, 以气候变化对河流阶地发育的影响为辅. 因此, 西宁盆地的阶地序列指示了14 Ma以来高原东北缘的多次阶段性抬升, 其中, 在距今14, 11.3, 1.2和0.15 Ma的构造抬升是明显的. 青藏高原东北缘西宁-互助地区的河流在中新世数百万年时间内(T11到T9)下切不到100 m, 而在更新世1.2 Ma以来(T7以来)下切了432 m, 指示了该地区在晚新生代后期加速隆升的事实. 湟水流域在1.55~1.2 Ma之间有一次大的水系格局调整. 在此之前, 古河流流向是西偏南, 之后流向为东偏南, 这次水系调整与构造活动有关. 相似文献
3.
《中国科学:地球科学》2017,(2)
阶地是研究现代河谷形成发育的重要地貌标志,结合年代学研究可以为区域古环境提供丰富的构造、气候和古水文变化信息.通过古地磁、电子自旋共振、光释光及黄土-古土壤地层序列的对比,初步确定渭河上游三阳川盆地1.2Ma以来共发育和保存着13级河流阶地.阶地特征与成因分析表明,阶地是在构造抬升背景下,河流系统对轨道尺度气候变化的响应,侧蚀堆积和深切下蚀作用交替进行.阶地序列的河漫滩顶部大多对应于古土壤层发育,表明河流下切阶地形成主要发生在古土壤开始发育的冰期向间冰期过渡阶段.河流两侧阶地时空展布的差异表明,0.62Ma三阳川盆地发生了构造反转,由过去盆地的整体抬升为主逐渐转变为断陷沉降.综合流域内阶地序列的研究,表明渭河上游现代河谷的形成发育起始于早更新世晚期1.4~1.2Ma. 相似文献
4.
宽谷及宽谷阶地的形成与流域内的构造抬升活动密切相关。文中在考察阿尔金北缘断裂东段雁丹图与长草沟宽谷的基础上 ,结合古气候资料 ,探讨了晚更新世晚期以来两地河流阶地所反映的构造抬升。雁丹图自约 16 1kaBP以来发育了 3级堆积阶地 (T1,T2 与T3) ,并出露埋藏主要宽谷。 3级阶地面年龄分别约为 16 1ka ,12 8ka ,6 2ka ,反映了 3次构造抬升的存在 ,代表了 3次构造抬升发生的时间。雁丹图自约 16 1kaBP以来的构造抬升速率约为 4 8～ 4 5mm/a ;12 8～ 6 2kaBP间的抬升速率约 6 4mm/a ;6 2kaBP以来为 3 1mm/a。长草沟在 7kaBP以来有 4级阶地发育 (T3,T2 ,T′1与T1) ,均为堆积阶地 ,并出露埋藏宽谷。其中T3与T2 出露埋藏主要宽谷 ,T′1与T1出露埋藏次要宽谷。T3,T2与T′13级阶地的阶地面年龄分别约为 7ka ,3ka,2 5ka。 4级阶地反映 2次构造抬升 ,一次在约 7kaBP ,一次在 3kaBP左右。自 7 0kaBP以来长草沟的抬升速率约为 5 9mm/a ,在 7～ 3 相似文献
5.
《地震地质》2017,(6)
河流阶地作为构造和气候作用的载体,记录了活动造山带地区的构造活动和气候变化之间的相对变化信息。文中以穿过祁连山北缘活动断裂带的洪水坝河和马营河为例,探讨河流地貌发育与构造和气候之间的关系。基于遥感影像解译识别出8—9级河流阶地,并对其期次进行划分。根据洪水坝河T5和马营河T6阶地的相对拔河高度和年龄,分别计算出2条河流15ka和11ka以来的平均下切速率为(10.2±2.0)mm/a和(12.2±2.8)mm/a。再利用差分GPS分别对2条河流的T5和T6阶地面上的断层陡坎进行精确测量,结合测年结果,计算出佛洞庙-红崖子活动断裂的垂直滑移速率比河流下切速率低1个量级。对比研究区内活动断裂两侧阶地发育序列的差异性,构造抬升和河流下切速率数量级的差别,并结合祁连山北缘区域上已发表的研究结果,初步认为构造活动与气候变化共同影响祁连山北缘河流阶地的发育,其中气候变化是控制该区全新世河流阶地发育的主要因素。更深入的活动构造调查和阶地年龄约束有助于更好地揭示祁连山北缘的活动构造特征和河流演化历史。 相似文献
6.
《四川地震》2017,(3)
本文通过嘉陵江广元段卫星影像的解译和野外地质地貌调查,将该地区的地貌分为河流冲积平原、低山丘陵和基岩山区三种类型,并统一划分出河流T1、T2、T3级阶地,阶地堆积以典型的河流二元结构为主,砾石的磨圆度和分选性较好。该地区第四纪地层厚度一般小于32 m,其中T1阶地第四纪地层厚度较大,主要分布在15~32 m范围内,而T2、T3阶地为基座基底,上覆第四系不甚发育,T2第四纪地层厚度小于15 m,T3阶地厚度小于5 m。该地区河流阶地的物质组成、地层厚度及分布特征,与龙门山构造活动强烈地区的河流阶地堆积差别较为明显,显示出嘉陵江广元段河流下切作用较弱,沉积相比较单一稳定,这表明这一地区的河流堆积主要受到气候因素影响,与这一地区微弱的构造活动背景也较为吻合。 相似文献
7.
8.
海南岛北西部新构造特征及其演化研究 总被引：3，自引：1，他引：2
利用DGPS系统测量海南岛西部阶地, 绘制地质地貌综合剖面, 将西部阶地分为海成阶地和河流阶地两种。 其中海成地貌包括一条砂堤和四级阶地: 砂堤宽2～10 m, 高程约10 m, 形成于5 ka以来; 海成一级阶地发育较好, 阶地面高程21～22 m, 形成于晚更新世至全新世之间; 海成二级阶地顶面高程约32 m左右, 形成于晚更新世晚期; 海成三级阶地较为发育, 阶地面高程40～42 m, 形成于121.8 ka; 海成四级阶地零星分布, 阶地面高程约57 m, 形成于中更新世晚期。 河流阶地也可分出四级: 一级阶地高程约20 m, 局部发育, 形成于11.4 ka; 二级阶地高程约34 m, 形成于47.2 ka; 三级阶地高约50 m, 其基座顶面标高约41 m, 形成于晚更新世早期; 四级阶地高程约71 m, 基座面标高约60 m, 形成于中更新世晚期。 这些阶地中均以二级最为发育。 晚更新世以来全区处于整体加速抬升的状态。 依据阶地面的综合剖面特征, 认为王五-文教断裂晚更新世以来的活动性较弱。 相似文献
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10.
利用卫星资料对阿尔金断裂带阿克塞以西进行阶地面对比和位错量分析 总被引：1，自引：0，他引：1
利用高精度的Spot卫星资料，通过详细的地质解译，对研究区域内的河流及其形成的河流阶地进行了系统的对比，通过区域对比，得到了阿尔金活动断裂带在阿克塞附近的最近一段时期以来的可靠的河流阶地的位错，在研究区域内，规模相近的河流形成的同级的河流阶地具有相近的水平位错，T3阶地的水平位错约为380m,T4阶地的水平位错约为1300m，T6阶地的水平位错约为3000m. 相似文献
11.
D. M. Pechersky A. A. Lyubushin Z. V. Sharonova 《Izvestiya Physics of the Solid Earth》2010,46(7):613-623
The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The
times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized
by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and
the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between
the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic
world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by
the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle
of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes
in the organic world. 相似文献
12.
The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth. 相似文献
13.
综合APIA、HONOLULU、PAMATAI 3个地磁台三分量的11年周期变化的形态后，可定性地提出该变化源于内场。如内源为核幔边界的电涡流，则其中心点应位于3台之间。 相似文献
14.
The depth to the top of magnetic dykes can be estimated from total field aeromagnetic data using the relation between the depth to magnetic sources and the autocorrelation function of magnetic data. By using synthetic anomalies we show that in the ideal case, depth can be determined to an accuracy of 10% or better, when the anomaly sources are two-dimensional dykes. However, the estimated depths depend on the width of the dykes. The estimated depth is about 0.6 times the actual depth to the top of thin dykes, and around the true depth for thick dykes having width-to-depth ratio around 3. The depth is considerably overestimated for very thick dykes (e.g., contacts, which is a special case of the thick dyke). Thus, the autocorrelation method requires that the width-to-depth ratio of the dyke is estimated independently to correctly estimate the depths. Alternatively, it must be assumed that the width-to-depth ratio for the two-dimensional source body is between 1.5 and 4. 相似文献
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As is known, the secular deceleration of the Earth's diurnal rotation is explained mainly by the tidal friction in the ocean. Below we consider this mechanism in some detail, taking into account also elastic deformations of the mantle under the action of ocean loading and the interaction between the tide-generating body, ocean tidal wave, liquid outer core, and solid inner core. It is shown that elastic displacements of the core-mantle boundary under the action of ocean loading are of about the same amplitude and phase as the elastic loading displacements of the Earth's outer surface. As a result, side by side with the mechanism of secular deceleration of diurnal rotation of the mantle, there are also (1) the opposite mechanism of secular acceleration of diurnal rotation of the outer liquid core and of the solid inner core and (2) the mechanism of excitation of differential rotation in the liquid core. Taking these effects into account, we compare theoretical and modern observed data on the eastward drift of the solid inner core. It is shown that the best agreement may be obtained if the turbulent viscosity of the liquid core is about 2 × 10
3
Poise 相似文献
17.
On data of bottom sampling, carried out by means of grab, trawl and underwater photography in August–September of 1993 in the area of the Pechora Sea, quantitative regularities of macrobenthos distribution are described for the ecological monitoring purposes. Maps of -biodiversity and biomass indices, bottom communities and trophic zones, singled out by dominant method, are presented. Assessment of structure changes of the investigated area bottom communities during the last 60–70 years is fulfilled. It is shown that the described communities on the whole are of natural undisturbed character and that the revealed changes are within the natural fluctuations in the abundance of benthic populations or may be interpreted in terms of methodical differences in the data analysis and generalization by different authors. 相似文献
18.
地震激励下处于深水中的桥墩和周围水体的相互作用将对桥梁结构的动力响应产生较大影响。首先对地震作用下水-桥墩的相互作用理论做了概括,给出了动水压力对桥墩的作用效应及各自的适用范围;对主要的三种考虑流固耦合效应的分析方法做了对比,探讨了地震作用下影响水-结构相互作用的主要因素,并对今后的研究提出了建议。 相似文献
19.
在数据完整率达到95%的基础上,为进一步确保中国大陆构造环境监测网络GNSS基准站观测数据质量,选取2010—2020年全国基准站观测数据,采用TEQC软件进行质量检验,分类整理其中多路径效应计算结果呈典型特征的台站,结合观测环境状态,对多路径效应存在的区域性特征进行分析,发现除接收机天线周围发生遮挡外,硬件更换、台站周围地势差等因素,均对多路径效应产生不同程度的影响,可为建站选址和观测环境监测工作提供参考。 相似文献
20.
Summary The maintenance of the axisymmetric component of the flow in the atmosphere is investigated by means of a steady-state, quasi-geostrophic formulation of the meteorological equations. It is shown that the meridional variations in the time-averaged axisymmetric variables can be expressed as the sum of three contributions, one being due to the eddy heat transport, another to the eddy momentum transport, and a third to the convective-radiative equilibrium temperature which enters the problem through the specification of a Newtonian form of diabatic heating. The contributions by the large scale eddies are evaluated through the use of observed values for the eddy heat and momentum transports.The contributions from each of the three forcing mechanisms to the temperature and zonal wind fields are invstigated individually and found to be of about equal importance. The sum of the three contributions are also presented for the temperature, the zonal wind, the stream function associated with the mean meridional circulation and the corresponding vertical motion. Although the results fail to reproduce the main observed features of the lower stratosphere, they are found to be in good agreement with observations in the middle latitude troposphere. At any pressure level, for example, the computed mean zonal wind has a jet-like profile and the axis of the jet is found to slope to the south with height, as observed in the atmosphere.Based in part on a thesis submitted by the first author as partial fulfillment of the requirements for the Ph.D. degree at the University of Michigan. — Publication No. 194 from the Department of Meteorology and Oceanography, The University of Michigan. 相似文献