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1.
塔里木盆地的高分辨率沉积记录对于理解青藏高原隆升、亚洲内陆干旱化乃至全球气候变化至关重要.建立可靠的地层年代标尺对于研究塔里木盆地晚新生代沉积环境演化、构造运动及古气候变化具有重要意义.本文对塔里木盆地东北缘库尔勒地区的两个全取心钻孔ZK3（深500 m）、ZK5（深300 m）进行详细的磁性地层学研究,结果表明,ZK3孔中更新统底界为54.8 m,下更新统底界为167.0 m,上新统底界为432.0 m,钻孔底部年龄约为6.2 Ma,属上中新统上部;ZK5孔中更新统底界为64.7 m,下更新统底界为241.5 m,钻孔底部年龄约为3.2 Ma,属上上新统.基于上述磁性地层年代标尺,通过沉积速率分析发现ZK3孔在3.0—3.6 Ma之间沉积速率明显增大,反映了塔里木盆地北部天山在此期间的快速隆升.通过东西部多个盆地地质剖面沉积速率的对比分析发现,这期构造活动在区域上具有准同期活动特征,在时代上与晚中新世以来青藏高原快速隆升的时代一致,可能与青藏高原的隆升扩展效应有关.  相似文献   

2.
错鄂湖200m深井岩芯古地磁测年表明,错鄂湖形成于约2．8Ma年前．沉积岩性组合、粒度特征和磁化率变化揭示了约3次大的沉积环境变化过程,反映了至少2次剧烈的青藏高原隆升过程;同时,孢粉组合也揭示了构造隆升导致的植被组合的变化．初步研究认为,大的湖泊沉积环境变化主要是在青藏高原不断隆升的背景上进行的．2．8-2．5Ma和0．8Ma以来的沉积环境演化主要受构造运动的控制,而2．5-0．8Ma环境演化过程更多的受到冰期-间冰期旋回气候变化的影响．  相似文献   

3.
Uplift of the Tibetan Plateau, inversion of eastern and western geomorphology, eastward flowing of large rivers, and run-through of the Changjiang River exert great influence on sedimentation and environ-mental variations in the East China Sea. Provenance discrimination of Tibetan-Plateau-originated sediments in the river-mouth areas and marginal seas is key to figure out these issues.In the past, most studies of the run-through time of the Changjiang and the Yellow rivers focused on geomo…  相似文献   

4.
Ar-Ar dating results of late Mesozoic-Cenozoic volcanic rocks from the Yanji area, NE China provide a new volcano-sedimentary stratigraphic framework. The previously defined “Triassic-Jurassic” volcanic rocks (including those from Sanxianling, Tuntianying, Tianqiaoling and Jingouling Fms.) were erupted during 118―106 Ma, corresponding to Early Cretaceous. The new eruption age span is slightly younger than the main stage (130―120 Ma) of the extensive magmatism in the eastern Central Asian Orogenic Belt and its adjacent regions. Subduction-related adakites occurring in the previously defined Quanshuicun Fm. were extruded at ca. 55 Ma. Based on these new Ar-Ar ages, the late Mesozoic to Palaeocene volcano-sedimentary sequences is rebuilt as: Tuopangou Fm., Sanxianling/Tuntianying Fm. (118―115 Ma), Malugou/Tianqiaoling Fm. (K1), Huoshanyan/Jingouling Fm. (108―106 Ma), Changcai Fm. (K2), Quanshuicun Fm. (~55 Ma) and Dalazi Fm. Our results suggest that subduction of the Pa- laeo-Pacific Ocean beneath the East Asian continental margin occurred during 106 to 55 Ma, consistent with the paleomagnetic observations and magmatic records which indicated that the Izanagi-Farallon ridge subduction beneath the southwestern Japan took place during 95―65 Ma.  相似文献   

5.
Reconstruction of uplift history of the Tibetan Plateau is crucial for understanding its environmental impacts. The Oiyug Basin in southern Tibet contains multiple periods of sedimentary sequences and volcanic rocks that span much of the Cenozoic and has great potential for further studying this issue. However, these strata were poorly dated. This paper presents a chronological study of the 145 m thick and horizontally-distributed lacustrine sequence using paleomagnetic method as well as a K-Ar dating of the underlying volcanic rocks. Based on these dating results, a chronostratigraphic framework and the basin-developmental history have been established for the past 15 Ma, during which three tectonic stages are identified. The period of 15-8.1 Ma is characterized by intense volcanic activities involving at least three major eruptions. Subsequently, the basin came into a tectonically quiescent period and a lacustrine sedimentary sequence was developed. Around 2.5 Ma, an N-S fault occurred across the southern margin of the basin, leading to the disappearance of the lake environment and the development of the Oiyug River. The Gyirong basin on northern slope of the Himalayas shows a similar basin developmental history and thus there is a good agreement in tectonic activities between the Himalayan and Gangdise orogenic belts. Therefore, the tectonic evolution stages experienced by the Oiyug Basin during the past 15 Ma could have a regional significance for southern Tibet. The chronological data obtained from this study may provide some constraints for further studies with regard to the tectonic processes and environmental changes in southern Tibetan Plateau.  相似文献   

6.
合肥盆地构造热演化的裂变径迹证据   总被引：12，自引：0，他引：12       下载免费PDF全文
运用裂变径迹分析方法,探讨分析了合肥盆地中新生代的构造热演化特征. 上白垩统和古近系下段样品的磷灰石裂变径迹（AFT）数据主体表现为靠近部分退火带顶部温度(±65℃)有轻度退火,由此估算晚白垩世至古近纪早期合肥盆地断陷阶段的古地温梯度接近38℃/km,高于盆地现今地温梯度(275℃/km).下白垩统、侏罗系及二叠系样品的AFT年龄(975～25Ma)和锆石裂变径迹(ZFT)年龄(118～104Ma)均明显小于其相应的地层年龄,AFT年龄－深度分布呈现冷却型曲线形态,且由古部分退火带、冷却带或前完全退火带及其深部的今部分退火带组成,指示早白垩世的一次构造热事件和其随后的抬升冷却过程. 基于AFT曲线的温度分带模式和流体包裹体测温数据的综合约束,推算合肥盆地早白垩世走滑压陷阶段的古地温梯度接近67℃/km. 径迹年龄分布、AFT曲线拐点年龄和区域抬升剥蚀时间的对比分析结果表明,合肥盆地在早白垩世构造热事件之后的104Ma以来总体处于抬升冷却过程,后期快速抬升冷却事件主要发生在±55Ma.  相似文献   

7.
The base level during the deposition of Jurassic in the Qiangtang Basin shows a complete cycle from rising to falling. The base level change is closely connected with tectonic evolution of the basin, especially connected with Bangonghu-Nujiang ocean evolution process in the formation and evolution of the basin. It is also affected by climate. The Jurassic strata correspond to a long-term base level cycle sequence. The sequence is in fact a non-complete symmetrical cycle, consisting of rising hemicycle and falling hemicycle. It can be divided into 6 intermediate-term base level cycle sequences, including 2 carbonate sequences, 3 mixture sedimentary sequences of carbonate and clastic rocks and one clastic sedimentary sequence. Depositional filling characteristics during base level change show that Bangonghu-Nujiang ocean spreads in Toarcian-Bajocian ages, and is at the height of spreading of Bangonghu-Nujiang ocean in Bathonian-Oxfordian ages. In that process, sea area became smaller because of the dry climate. Eventually, marine depositional filling is ended with the subduction and collision of Bangonghu-Nujiang ocean.  相似文献   

8.
南海北部珠江口与琼东南盆地构造-热模拟研究   总被引：9，自引：3，他引：6       下载免费PDF全文
珠江口盆地和琼东南盆地位于南海北部的大陆边缘,本文在此地区选取了13条典型剖面,进行了构造沉降史和热史的模拟,初步探讨了其新生代以来的构造-热演化历史.其研究结果表明:珠江口盆地存在两次热流升高过程,分别为始新世(56.5～32 Ma)和渐新世(32～23.3 Ma).琼东南盆地存在三期加热和两期冷却过程,始新世盆地热...  相似文献   

9.
祁连山东北缘黄土磁组构记录的古风向重建   总被引：2，自引：0，他引：2       下载免费PDF全文
近年来,利用黄土磁化率各向异性/磁组构（AMS）研究古风向变化被广泛应用.在对祁连山东北缘厚755 m的中路黄土剖面岩石磁学和磁组构研究的基础上,恢复了该区14 Ma以来古风向变化序列.磁组构指示的古风向表明,在14～078 Ma期间,本区的地面主导风向为NW-SE;从078 Ma开始,地面主导风向逐渐向NE-SW过渡;至05 Ma时,该区地面主导风稳定为NE-SW向.对青藏高原隆升的研究显示,在12～08 Ma期间青藏高原发生过称为“昆黄运动”的大规模隆起.结合我们对主导风向变化驱动因子的分析表明,祁连山东北缘近地面主导风向的第一次转变很可能是同时期青藏高原构造强烈隆升对大气环流影响产生的环境后果.  相似文献   

10.
The Cretaceous system of the Kuqa depression is a regional scale (second order) depositional sequence defined by parallel unconformities or minor angular unconformities. It can be divided into four third-order sequence sets, eleven third-order sequences and tens of fourth- and fifth-order sequences. It consists generally of a regional depositional cycle from transgression to regression and is composed of three sets of facies associations: alluvial-fluvial, braided river-deltaic and lacustrine-deltaic facies associations. They represent the lowstand, transgressive and highstand facies tracts within the second-order sequence. The tectonic subsidence curve reconstructed by backstripping technique revealed that the Cretaceous Kuqa depression underwent a subsidence history from early accelerated subsidence, middle rapid subsidence and final slower subsidence phases during the Cretaceous time, with the correspondent tectonic subsidence rates being 30-35 m/Ma, 40-45 m/Ma and 5-10 m/Ma obtained from northern foredeep. This is likely attributed to the foreland dynamic process from early thrust flexural subsidence to late stress relaxation and erosion rebound uplift. The entire sedimentary history and the development of the three facies tracts are a response to the basin subsidence process. The slower subsidence foreland gentle slope was a favorable setting for the formation of braided fluvial deltaic systems during the late period of the Cretaceous, which comprise the important sandstone reservoirs in the depression. Sediment records of impermanent marine transgression were discovered in the Cretaceous and the major marine horizons are correctable to the highstands of the global sea level during the period.  相似文献   

11.
ＩＮＴＲＯＤＵＣＴＩＯＮＨａｉｙｕａｎ Ｔｏｎｇｘｉｎｓｙｎｔａｘｉｓ ,ｗｈｉｃｈｌｉｅｓｏｎｔｈｅｎｏｒｔｈｅａｓｔｅｒｎｅｄｇｅｏｆｔｈｅＱｉｎｇｈａｉ ＸｉｚａｎｇＰｌａｔｅａｕ ,ｗａｓｆｏｒｍｅｄａｎｄｓｅｖｅｒｅｌｙｄｅｆｏｒｍｅｄａｓｆｏｒｅｌａｎｄｂａｓｉｎｄｕｅｔｏｔｈｅｒｉｓｅｏｆｔｈｅＱｉｎｇｈａｉ ＸｉｚａｎｇＰｌａｔｅａｕｓｉｎｃｅｔｈｅＣｅｎｏｚｏｉｃ .Ｉｎｔｈｅａｒｃ ｌｉｋｅｒｅｇｉｏｎ ,Ｃｅｎｏｚｏｉｃｄｅｐｏｓｉｔｓａｒｅｗｉｄｅｌｙｄｉｓｔｒｉｂｕｔｅｄａｎｄｐｅ…  相似文献   

12.
Determination of the age of the Precambrian-Cambrian boundary is critical in understanding early evolution of life on Earth. SIMS U-Pb zircon analyses of the Bed 5 tuff layer of the Meishucun section were carried out closely following the guidance of cathodoluminescence images, and the majority of analyses were conducted on the oscillatory zircon grains. Thirteen measurements yield a highly reliable Concordia U-Pb age of 536.7 ± 3.9 Ma for the Bed 5 horizon. A grand mean of 206Pb/238U age of 535.2± 1.7 Ma (...  相似文献   

13.
Regional architecture of geochronology and differential cooling pattern show that the Dabie orogen underwent a thermal doming extension during 140-85 Ma. This extension resulted in widespread re-melting of the Dabie basement, intense volcanic activities in North Huaiyang and the formation of fault-controlled depressions in the Hefei basin. This thermal doming extension can be further divided into two consecutive evolving stages, i.e. the intensifying stage (140-105 Ma) and the declining stage (105-85 Ma). In the first stage (140-105 Ma), the thermal doming mainly was concentrated in the Dabie block, and to a less degree, in the Hongan block. The thermal doming structure of the Dabie block is configured with Macheng-Yuexi thermal axis, Yuexi/Luotian thermal cores and their downslide flanks. The orientation of thermal axis is dominantly parallel to the strike of orogen, and UHP/HP units together with metamorphic rocks of North Huaiyang constitute the downslide flanks. The Yuexi core differs from the Luotian core in both the intensity and the shaping time. To some extent, the Hongan block can be regarded as part of downslide systems of the Dabie doming structure. The doming process is characterized by thermal-center's migration along the Macheng-Yuexi thermal axis; consequently, it is speculated to be attributed to the convective removal of thickened orogenic root, which is a process characterized by intermittance, migration, large-scale and differentiation. During the declining stage (105-85 Ma), the dome- shaped figure still structurally existed in the Dabie orogen, but orogenic units cooled remarkably slow and magmatic activities stagnated gradually. Study on the thermal doming of Dabieshan Mountains can thus provide detailed constraints on the major tectonic problems such as the UHP/HP exhumation model, the boundary between North Dabie and South Dabie, and the orogenesis mechanism.  相似文献   

14.
The Taishu Group, a marine formation with a thickness of >5400 m, crops out on Tsushima Island, located in the southwestern Japan Sea. The group, which is generally regarded as early Eocene to early Miocene in age, provides important information about the tectonic setting of the Japan Sea. In this study, we present new SHRIMP U–Pb dates for igneous zircons from the Kunehama Tuff, which is in the basal part of the Taishu Group, and the Oobaura Tuff, which is in the uppermost part of the group. Results show that the Taishu Group was deposited rapidly, during the short interval of 17.9–15.9 Ma (early–middle Miocene), and is equivalent to other early–middle Miocene strata found in the Japan Sea region. Our results provide new constraints on the geological history of the Japan Sea and its islands.  相似文献   

15.
塔里木盆地库车坳陷克拉苏河沿岸发育良好的新生界地层.我们对克拉苏河沿岸新生界剖面分A、B两段进行系统采样,获得定向岩芯样品1700余块. 岩石磁学研究表明,新生代沉积岩中磁性矿物以赤铁矿为主,含有少量磁铁矿;磁组构测试结果显示,两段剖面磁面理均较磁线理发育,最小磁化率主轴近于直立,显示原生沉积组构. A剖面磁化率主轴к1的偏角指示古流向. 库姆格列木群沉积时的古水流方向为NEE-SWW向,至苏维依组沉积时,流向变为NNE-SSW向. 河流古流向在苏维依组形成时发生急剧变化,说明南天山此时可能发生了明显的隆升,且以北西部隆升为主;B剖面为吉迪克组、康村组和库车组粗粒碎屑岩,磁组构显示к1-к2构成的磁面理与层理面小角度相交,к3呈叠瓦状分布,可以用来指示古水流方向.从吉迪克组至库车组下段,古流向均为NNW-SSE,但逐渐偏东,暗示天山在此期间处于缓慢的隆升期或东西部处于同步隆升,且西部隆升速度快于东部.  相似文献   

16.
1999年山西大同Ms 5.6地震的震源断层   总被引：9，自引：0，他引：9  
大同震区先后在 1989、1991和 1999年发生MS >5地震 ,利用大同遥测地震台网的记录资料进行比较精确的地震序列震源定位 ,结合宏观烈度分布和震源机制解资料 ,详细地分析对比了 3次子序列的异同。结果显示 ,1999年MS5 .6地震的震源断层是走向NWW、长 16km、宽12km、埋深 5km以下、倾角近直立的左旋走滑断层。而前 2个子序列是NNE为主的右旋走滑断层活动所致 ,表明地震破裂方向发生了变化。这种 2个以上方向先后出现、并且强弱有别的地震破裂是普遍存在的 ,表明震源环境的复杂程度与地震序列的类型有关。虽然震区存在NE向的大王村断裂和NW向的团堡断裂 ,但目前没有证据说明震源断层和 2条构造断层连通。 3次子序列的震源断层都是走滑断层 ,也和 2条构造正断层有别。 1999年的子序列可能属于新破裂。  相似文献   

17.
The Jurassic stratigraphy in China is dominated by continental sediments. Marine facies and marine-terrigenous facies sediment have developed locally in the Qinghai-Tibet area, southern South China, and northeast China. The division of terrestrial Jurassic strata has been argued, and the conclusions of biostratigraphy and isotope chronology have been inconsistent.During the Jurassic period, the North China Plate, South China Plate, and Tarim Plate were spliced and formed the prototype of ancient China. The Yanshan Movement has had a profound influence on the eastern and northern regions of China and has formed an important regional unconformity. The Triassic-Jurassic boundary(201.3 Ma) is located roughly between the Haojiagou Formation and the Badaowan Formation in the Junggar Basin, and between the Xujiahe Formation and the Ziliujing Formation in the Sichuan Basin. The early Early Jurassic sediments generally were lacking in the eastern and central regions north of the ancient Dabie Mountains, suggesting that a clear uplift occurred in the eastern part of China during the Late Triassic period when it formed vast mountains and plateaus. A series of molasse-volcanic rock-coal strata developed in the northern margin of North China Craton in the Early Jurassic and are found in the Xingshikou Formation, Nandailing Formation, and Yaopo Formation in the West Beijing Basin. The geological age and markers of the boundary between the Yongfeng Stage and Liuhuanggou Stage are unclear. About 170 Ma ago, the Yanshan Movement began to affect China. The structural system of China changed from the near east-west Tethys or the Ancient Asia Ocean tectonic domain to the north-north-east Pacific tectonic domain since 170–135 Ma. A set of syngenetic conglomerate at the bottom of the Haifanggou or Longmen Fms. represented another set of molasse-volcanic rock-coal strata formed in the Yanliao region during the Middle Jurassic Yanshan Movement(Curtain A1). The bottom of the conglomerate is approximately equivalent to the boundary of the Shihezi Stage and Liuhuanggou Stage. The bottom of the Manas Stage creates a regional unconformity in northern China(about 161 Ma, Volcanic Curtain of the Yanshan Movement, Curtain A2). The Jurassic Yanshan Movement is likely related to the southward subduction of the Siberian Plate to the closure of the Mongolia-Okhotsk Ocean. A large-scale volcanic activity occurred in the Tiaojishan period around 161–153 Ma. Note that 153 Ma is the age of the bottom Tuchengzi Formation, and the bottom boundary of the Fifth Stage of the Jurassic terrestrial stage in China should have occurred earlier than this. This activity was marked by a warming event at the top of the Toutunhe Formation, and the change in the biological assembly is estimated to be 155 Ma. The terrestrial Jurassic-Cretaceous boundary(ca. 145.0 Ma) in the Yanliao region should be located in the upper part of Member 1 of the Tuchengzi Formation, the Ordos Basin in the upper part of the Anding Formation, the Junggar Basin in the upper part of the Qigu Formation, and the Sichuan Basin in the upper part of the Suining Formation The general characteristics of terrestrial Jurassic of China changed from the warm and humid coal-forming environment of the Early-Middle Jurassic to the hot, dry, red layers in the Late Jurassic. With the origin and development of the Coniopteris-Phoenicopsis flora, the Yanliao biota was developed and spread widely in the area north of the ancient Kunlun Mountains, ancient Qinling Mountains, and ancient Dabie Mountain ranges in the Middle Jurassic, and reached its great prosperity in the Early Late Jurassic and gradually declined and disappeared and moved southward with the arrival of a dry and hot climate.  相似文献   

18.
Regional architecture of geochronology and differential cooling pattern show that the Dabie orogen underwent a thermal doming extension during 140–85 Ma. This extension resulted in widespread re-melting of the Dabie basement, intense volcanic activities in North Huaiyang and the formation of fault-controlled depressions in the Hefei basin. This thermal doming extension can be further divided into two consecutive evolving stages, i.e. the intensifying stage (140–105 Ma) and the declining stage (105–85 Ma). In the first stage (140–105 Ma), the thermal doming mainly was concentrated in the Dabie block, and to a less degree, in the Hongan block. The thermal doming structure of the Dabie block is configured with Macheng-Yuexi thermal axis, Yuexi/Luotian thermal cores and their downslide flanks. The orientation of thermal axis is dominantly parallel to the strike of orogen, and UHP/HP units together with metamorphic rocks of North Huaiyang constitute the downslide flanks. The Yuexi core differs from the Luotian core in both the intensity and the shaping time. To some extent, the Hongan block can be regarded as part of downslide systems of the Dabie doming structure. The doming process is characterized by thermal-center’s migration along the Macheng-Yuexi thermal axis; consequently, it is speculated to be attributed to the convective removal of thickened orogenic root, which is a process characterized by intermittance, mi gration, large-scale and differentiation. During the declining stage (105–85 Ma), the dome-shaped figure still structurally existed in the Dabie orogen, but orogenic units cooled remarkably slow and magmatic activities stagnated gradually. Study on the thermal doming of Dabieshan Mountains can thus provide detailed constraints on the major tectonic problems such as the UHP/HP exhumation model, the boundary between North Dabie and South Dabie, and the orogenesis mechanism.  相似文献   

19.
南海西南海盆构造演化的热模拟研究   总被引：17，自引：6，他引：11       下载免费PDF全文
南海西南海盆的张裂和海底扩张是白垩纪末至中始新世南海形成过程中最重要的构造事件.本文采用三维有限单元法对该区的热演化过程进行了模拟计算.通过对变形、温度结构的计算,研究了西南海盆张裂变形、海底扩张持续时间、地幔物质上升、地壳岩墙沿扩张中心的挤入扩张活力、岩浆活动等.计算结果表明：由于其深部动力学条件不足,海盆一次扩张持续时间在10～15Ma之间,其后地幔物质的上升活动逐渐停止,地壳失去扩张动力,使得扩张中心成为残留扩张中心的死亡裂谷,而未构成中脊或中隆带.虽然该处地幔物质上升的潜力不足,但伴随局部的断裂,尤其是盆、缘边界的拆离拉张,仍能产生相当强烈的岩浆喷溢活动,导致此区海盆成型之后的海山崛起.  相似文献   

20.
We present 39Ar–40Ar dating of phengite, muscovite and paragonite from a set of mafic and metasedimentary rocks sampled from the high-pressure (HP) metaophiolites of the Voltri Group (Western Alps) and from clasts in the basal layer conglomerates from the Tertiary molasse which overlie the high-pressure basement. The white mica-bearing rocks display peak eclogitic and blueschist-facies parageneses, locally showing complex greenschist-facies replacement textures. The internal discordance of age spectra is proportional to the chemical complexity of the micas. High-Si phengites from eclogite clasts record a 39Ar–40Ar age of ca. 49 Ma for the eclogite stage and ca. 43 Ma for the blueschist retrogression; phengites from a blueschist basement sample yield an age of ca. 40 Ma; low-Si muscovite from a metasediment dates the formation of the greenschist paragenesis at ca. 33 Ma. Our data indicate that the analyzed samples reached high-pressure conditions at different times over a time-span of c.a. 10 Ma. Subduction was continuing during exhumation and blueschist retrograde re-equilibration of higher-pressure, eclogite-facies rocks. This process kept the isotherms depressed, allowing the older HP-rocks to escape thermal re-equilibration. Our results, added to literature data, fit a tectonic model of a subduction–exhumation cycle, with different tectonic slices subducted at different times from Early Eocene until the Eocene–Oligocene boundary.  相似文献   

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