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1.
New progresses on geothermal history of Turpan-Hami Basin, Xinjiang, China   总被引：2，自引：0，他引：2  
A comprehensive study on geothermal history of the Turpan-Hami Basin by vitrinite reflectance, fluid inclusion geothermometry, apatite fission track and40Ar-39Ar dating displays that the main effects influencing geotemperature distribution are burial depth of the basement, heat flow, magmatic activities, as well as tectonic movement, having a rugulation to be higher in the east and north, lower in the west and south, as well as higher in the past and lower at the present. The heat of the mantle source and the Indo-China tectonic thermal event have extremely influenced maturation of source rocks of the upper Lower Permian and the Middle and Upper Triassic in the lndo-China epoch. While, the geothermal gradient and the weak tectonic geothermal event of the Early Yanshan Movement provided necessary heat for the maturation of source rock in coal-bearing strata of the Middle and Lower Jurassic.  相似文献   

2.
Neoproterozoic igneous and metamorphic complexes occur as tectonic domes in the Longmen Mountains of the western margin of the Yangtze Block, and are important in reconstructing the Rodinian supercontinent and constraining the timing and mechanism of tectonic denudational processes. The Pengguan dome consists of granitic intrusions and metamorphic rocks of the Huangshuihe Group and is tectonically overlain by ductilly deformed Sinian to Paleozoic strata. The plutonic intrusions consist of granites with abundant amphibolite enclaves. New LA-ICP-MS zircon U-Pb dating yielded an emplacement age of 809±3 Ma and a protolith age of 844±6 Ma for the granite. The granitic rocks have geochemical signatures typical of A-type granites, indicating their formation under an extensional environment, by melting of newly formed tonalite-trondhjemite-granodiorite (TTG) rocks. A detachment fault, characterized by variable ductile shear deformation of S-C fabric and ESE-ward kinematics, separates the Pengguan dome from the Sinian-Paleozoic cover. 40Ar/39Ar dating of muscovite from the mylonite in the detachment fault of the dome demonstrates that ductile deformation occurred at ~160 Ma. This study indicates the existence of a Neoproterozoic magmatic arc-basin system, which was denudated by a Jurassic middle crustal ductile channel flow along the Longmenshan thrust belt.  相似文献   

3.
The analyzing data on stratigraphic temperature measurement, thermal conductivity of the strata and radioactive heat production rate show that the present average geothermal gradient in the Ordos Basin is 2.93 °C/100 m, and the average heat flow value is 61.78 mW/m2, which belongs to the mesothermal basin, and the value of the present geothermal gradient and heat flow in the east is higher than that in the west. The sandstone radioactive heat production rate of Zhiluo Group in Dongsheng Uranium deposits of Yimeng uplift is obviously higher in the mudstone, indicating that there exists a uranium anomaly. Based on studies of the present thermal field of the basin, the late-Mesozoic paleotemperature and paleogeothermal gradient are determined by using different kinds of paleotemperature methods. According to the anomaly of the late-Mesozoic paleotemperature gradient and magmatic event age, there was a tectonic thermal event in the early Cretaceous epoch of late-Mesozoic. This article rebuilds tectonic thermal history of different tectonic units by thermal history simulation using basin simulating software. The evolution of oil-gas and coal, and accumulation (mineralization) of mineral uranium are all controlled by the tectonic thermal history in the Ordos basin, especially by the tectonic thermal event that happened in the late Mesozoic. For both the gas source rocks of upper Paleozoic group and lower paleozoic group, the gas was largely generated in the early Cretaceous epoch of the late Mesozoic. The main petroleum generation period for Yanchang Group in Triassic system is the early Cretaceous epoch too, and the highest thermal maturity of the coal of Permo-Carboniferous, Triassic, and Jurassic reaches is the early Cretaceous epoch also. Early Cretaceous epoch is still one of the most important mineralizing periods of uranium.  相似文献   

4.
Abstract The Shimanto accretionary complex on the Muroto Peninsula of Shikoku comprises two major units of Tertiary strata: the Murotohanto Sub-belt (Eocene-Oligocene) and the Nabae Sub-belt (Oligocene-Miocene). Both sub-belts have been affected by thermal overprints following the peak of accretion-related deformation. Palaeotemperatures for the entire Tertiary section range from ～ 140 to 315°C, based upon mean vitrinite reflectance values of 0.9–5.0%Rm. Values of illite crystallinity index are consistent with conditions of advanced diagenesis and anchimetamorphism. Illite/mica b0 lattice dimensions indicate that burial pressures were probably no greater than 2.5kbar. In general, levels of thermal maturity are higher for the Murotohanto Sub-belt than for the Nabae Sub-belt. The Eocene-Oligocene strata also display a spatial decrease in thermal maturity from south to north and this pattern probably was caused by regional-scale differential uplift following peak heating. Conversely, the palaeothermal structure within the Nabae Sub-belt is fairly uniform, except for the local effects of mafic intrusions at the tip of Cape Muroto. There is a paleotemperature difference of ～ 90°C across the boundary between the Murotohanto and Nabae Sub-belts (Shiina-Narashi fault), and this contrast is consistent with approximately 1200 m of post-metamorphic vertical offset. Subduction prior to Middle Miocene probably involved the Kula or fused Kula-Pacific plate and the background geothermal gradient during the Eocene-Oligocene phase of accretion was ～ 30–35°C/km. Rapid heating of the Shimanto Belt evidently occurred immediately after a Middle Miocene reorganization of the subduction boundary. Hot oceanic lithosphere from the Shikoku Basin first entered the subduction zone at ～ 15 Ma; this event also coincided with the opening of the Sea of Japan and the rapid clockwise rotation of southwest Japan. The background geothermal gradient at that time was ～ 70°C/km. Whether or not all portions of the inherited (Eocene-Oligocene) palaeothermal structure were overprinted during the Middle Miocene remains controversial.  相似文献   

5.
张强凹陷及邻区的构造应力分析   总被引：4，自引：0，他引：4       下载免费PDF全文
曲国胜  周永胜 《地震地质》1997,19(4):54-352
通过对张强凹陷及邻区露头构造形迹和岩心裂缝测量的应力分析，把该地区的地质历史划分出自太古代以来的８个构造期，确定了各期构造应力场状态及构造组合形式，认为晚侏罗世及白垩纪古构造应力场是断陷盆地形成、发展的主要应力场，晚侏罗世为近东西向拉张的构造应力状态；阜新组沉积期末至泉头组沉积前，由东西向拉张转为近东西向挤压，导致断陷阶段结束和上侏罗统变形；白垩纪为东西向挤压，早期区域整体沉降，晚期大面积隆升遭受剥蚀。早第三纪期为北西－南东向挤压，晚第三纪以来北东东－南西西向挤压。新生代的两期应力场仅使一些断裂继续活动，变形强度小于前两期  相似文献   

6.
大丰—包头剖面以"高密度观测点距与炮距"为特点,我们在1334 km测线上获得了21炮高信噪比的地震资料.在对Pg波震相特点分析基础上利用反演方法处理、构建了基底的精细结构图像,揭示了沿剖面不同构造地块基底结构的差异.苏北盆地基底埋深4.5~9.0 km、苏鲁隆起1.5~2.0 km,基底埋深与速度结构的强烈起伏变化可视其为华北与扬子板块碰撞、挤压构造环境下形成复杂的构造格局在地震学上的体现;鲁西隆起区基底埋深浅、速度高,结构稳定;华北盆地Pg波到时滞后、视速度低,基底埋深7.0~10.km,速度结构与基底面存在局部的起伏变化.诸多现象揭示出该区为新生代沉积巨厚、规模较大的基底坳陷区.同时在盆地内不同构造单元基底结构呈局部分块、凹陷与凸起并存的构造格局,显示出新生代沉积活动显著、变化强烈、结构不稳定的构造特点;太行山前断裂、聊兰断裂是具有显著地震学标志的断裂构造带,断裂两侧基底界面呈现出"断崖式塌陷"和速度结构的强烈横向非均匀性.综合研究认为,太行山前断裂是华北地区一条重要的构造带,它的复杂性不仅体现在两侧地形地貌、地层介质的截然不同,其基底埋深及速度结构、地壳及地幔岩石圈结构均存在显著的差异,其重要的标志是太行山以东不仅地壳厚度发生了相当规模的减薄,岩石圈的厚度也明显减薄,亦即形成了华北克拉.通破坏在东西部其基底一地壳一岩石圈的结构在空间上具有明显的差异性及强烈的横向非均匀性.  相似文献   

7.
Masayuki  Ehiro  Satoru  Kojima  Tadashi  Sato  Talat  Ahmad  Tomoyuki  Ohtani 《Island Arc》2007,16(1):124-132
Abstract   Callovian (late Middle Jurassic) ammonoids Macrocephalites and Jeanneticeras were recovered from the Shyok suture zone, northeast of Chang La Pass, Ladakh, northwest India. They are the first reliable Jurassic fossils and the oldest chronologic data from the Shyok suture zone. The ammonoid-bearing Jurassic strata, newly defined as the Tsoltak Formation, consist largely of terrigenous mudstone with thin sandstone beds and were probably a part of the continental basement to the Cretaceous Ladakh Arc.  相似文献   

8.
Abstract   Detrital composition and major element geochemistry of Jurassic sandstones in the south Hefei Basin, central China, show their provenance to be the Dabie Mountains, whose tectonic attributes are closely related to continent–island arc complexes. It was found that a provenance change, from recycled orogen signatures and mixed orogenic sandstones to arc orogen, occurs from the lower Middle Jurassic to the Upper Jurassic (the Zhougongshan Formation). Dissected magmatic arc sources were gradually exposed in the Dabie Mountains due to intensive exhumation during the Late Jurassic, particularly after the Fenghuangtai depositional phase. Furthermore, it can be infered that the magmatic arc was initially present in both the Early Paleozoic and the Triassic, according to isotopic dating studies in previously published reports. δ13C–δ18O tracing between existing marbles of different strata in the Dabie block and marble gravels of the Fenghuangtai Formation in the Hefei Basin indicate that partial lithostratigraphic units for the Jurassic provenances have entirely disappeared from the Dabie block; therefore, it is impossible to reconstruct integral orogenic processes from studies on the remaining Dabie block alone. These findings, together with basin-fill sequences, also suggest that the Hefei Basin was mainly subjected to compressive mechanical regimes rather than extensional regimes in the Jurassic, which resulted in reverse-grading clastic depositional sequences, and is probably related to the northward intracontinental deep subduction of the Yangtze Plate. Regional exhumation properties and a tectonic model of the Late Mesozoic Dabie orogenesis are discussed in this paper.  相似文献   

9.
中国东北地区大兴安岭西侧盆地群包括漠河盆地、根河盆地、拉布达林盆地、海拉尔盆地和二连盆地等,蕴藏着丰富的中、新生代油气资源.为研究该盆地群域古生代、中新生代构造演化,综合建立盆地群域地球动力学模型,补充东北亚构造演化理论,本文综述该盆地群域受控的区域构造与深部构造背景、盆地群构造特征与性质、主要控盆断裂特征、盆地群油气条件比较以及盆地群域已完成并取得重要结果的地球物理工作.归纳已有主要认识和研究结果:(1)对大兴安岭西侧的盆地群起构造控制作用的构造带包括蒙古—鄂霍茨克洋缝合带、西拉木伦河缝合带、黑河—贺根山缝合带、塔原—喜桂图缝合带、西太平洋板块俯冲带,以及额尔古纳—呼伦断裂和得尔布干断裂.(2)二连盆地、海拉尔盆地和漠河盆地的盆地构造轴向与蒙古—鄂霍茨克洋缝合带走向相关;而且三个盆地内的一级构造单元走向(隆起、坳陷和推覆带)也具有这类特点.(3)几个地学断面的综合地球物理研究表明,大兴安岭西侧盆地群岩石圈地幔厚度自北向南变厚,南部盆地基底与华北地台基底表现类似;盆地群基底电性结构因受到软流圈热物质作用可能在继续演化.(4)在盆地沉积地层方面,漠河盆地的下部是侏罗系陆相煤系地层,上部是白垩系火山岩地层;海拉尔盆地由下侏罗统的铜钵庙组、南屯组,上侏罗统的大磨拐河组和下白垩统的伊敏组共同组成扎赉诺尔群,厚约3000m;二连盆地中生代地层中,中下侏罗统主要为含煤建造,上侏罗统为火山岩建造,下白垩统主要为含油建造和含煤建造,上白垩统为砂砾岩建造.(5)盆地群整体勘探程度较低.基于上述研究结果,需要进一步研究的科学问题包括:由本研究区的地球物理、构造地质、石油地质等多学科的综合研究,解决研究区受控的区域构造应力场所包括的因素及其作用,以及在岩石圈尺度上三维空间的地球物理场表征;深部构造对盆地群域构造的作用;从晚古生代到中新生代研究区构造演化特点及其依据;从北至南约1650km长的盆地群域构造差异与依据;盆地群(域)油气条件与毗邻的松辽盆地在构造成因上的差异.  相似文献   

10.
The timing of the "Yanshanian Movement" and the tectonic setting that controlled the Yanshan fold-and-thrust belt during Jurassic time in China are still matters of controversy. Sediments that filled the intramontane basins in the Yanshan belt perfectly record the history of "Yanshanian Movement" and the tectonic background of these basins. Recognizing syn-tectonic sedimentation, clarifying its relationship with structures, and accurately defining strata ages to build up a correct chronostratigraphic framework are the key points to further reveal the timing and kinematics of tectonic deformation in the Yanshan belt from the Jurassic to the Early Cretaceous. This paper applies both tectonic and sedimentary methods on the fold-and-thrust belt and intramontane basins in the Zhangjiakou area, which is located at the intersection between the western Yanshan and northern Taihangshan. Our work suggests that the pre-defined "Jurassic strata" should be re-dated and sub-divided into three strata units: a Late Triassic to Early Jurassic unit, a Middle Jurassic unit, and a Late Jurassic to early Early Cretaceous unit. Under the control of growth fold-and-thrust structures, five types of growth strata developed in different growth structures: fold-belt foredeep type,thrust-belt foredeep type, fault-propagation fold-thrust structure type, fault-bend fold-thrust structure type, and fault-bend foldthrust plus fault-propagation fold composite type. The reconstructed "source-to-sink" systems of Late Triassic to Early Jurassic,Middle Jurassic and Late Jurassic to early Early Cretaceous times, which are composed of a fold-and-thrust belt and flexure basins, imply that the "Yanshanian Movement" in our study area started in the Middle Jurassic. During Middle Jurassic to early Early Cretaceous times, there have been at least three stages of fold-thrust events that developed "Laramide-type" basementinvolved fold-thrust structures and small-scale intramontane broken "axial basins". The westward migration of a "pair" of basement-involved fold-thrust belt and flexure basins might have been controlled by flat subduction of the western Paleo-Pacific slab from the Jurassic to the Early Cretaceous.  相似文献   

11.
Protolith ages and Indosinian deformation mechanism of metamorphic rocks in the Zhangbaling uplift segment of the Tan-Lu Fault Zone are important, unsolved problems. Our LA-ICP-MS zircon dating work indicates that protolith ages of the greenschist-facies Zhangbaling Group are 754–753 Ma, and those of the amphibolite-facies Feidong Complex are 800–745 Ma. These rocks belong to the earliest cover of the Yangtze Plate. Their ages and metamorphic features suggest that the rocks did not come from the Dabie Orogen. The Indosinian structures in the Zhangbaling Group and lower Sinian strata formed in a flatlying ductile detachment zone with a shear sense of top-to-the-SSW whereas those in the underlying Feidong Complex are characterized by ENE-WSW inclined folds developed under a ductile regime. It is suggested therefore that the sinistral Tan-Lu Fault Zone of the Indosinian period is buried under the Hefei Basin west of the Zhangbaling uplift segment and the uplift segment is a displaced block neighboring the fault zone. Detachment deformation between the upper rigid and lower ductile crust during displacement of the Zhangbaling uplift segment resulted in the formation of the flat-lying ductile detachment zone and its underlying drag fold zone of a ductile regime. The protolith ages and deformation mechanism in the Zhangbaling uplift segment further prove sinistral origination of the Tan-Lu Fault Zone during the continent-continent collision of the North China and Yangtze plates and support the indentation model for the two-plate collision that considers the Tan-Lu Fault Zone as an oblique convergence boundary.  相似文献   

12.
Hidetoshi  Hara  Ken-Ichiro  Hisada 《Island Arc》2007,16(1):57-68
Abstract   Micro-thermometry of water-rich fluid inclusions from two syn-tectonic veins sets ( D1 and D2 veins) in the Otaki Group, part of the Cretaceous Shimanto accretionary complex of the Kanto Mountains, central Japan reveals the following tectono-metamorphic evolution. Combining the results of microthermometric analyses of fluid inclusions from D1 veins with an assumed geothermal gradient of 20–50°C/km indicates that the temperature and fluid pressure conditions during D1 were 270–300°C and 140–190 MPa, respectively. Peak metamorphic conditions during the development of D2 slaty cleavage involved temperatures in excess of 300°C and fluid pressures greater than 270 MPa, based on analyses of microthermometry of water-rich fluid inclusions from the D2 vein and illite crystallinity. The estimated fluid pressure increased by approximately 80 MPa from D1 accretionary processes to metamorphism and slaty cleavage development during D2 . Assuming that fluid pressure reached lithostatic pressure, the observed increase in fluid pressure can be accounted for by thrusting of the Jurassic Chichibu accretionary complex over the Cretaceous Shimanto accretionary complex. Following thrusting, both accretionary complexes were subjected to metamorphism during the latest Cretaceous.  相似文献   

13.
As is well known that many decollement layers were developed in the Longmenshan thrust belt,Si-chuan Basin,China. Through field investigation,explanation of seismic profiles and analysis of the balanced sections,we can divide the decollement zones into 3 categories: (1) the deep level decolle-ment zones,including the crust-mantle decollement layer,intracrustal decollement layer,and presinian basal decollement layer. The main structural styles of their deformation are the crust-mantle decoup-ling detachment deformation,the basal ductile shear deformation,etc.; (2) the middle level decollement zones,including the Cambrian-Ordovician decollement layer,the Silurian decollement layer,etc.,the main structural styles of their deformation are the isopachous fold,the angular fold,the saddle struc-ture,and the combination styles of them; and (3) the shallow level decollement zones,including the Xujiahe Formation decollement layer of Upper Triassic and the Jurassic decollement layers,the main structural styles of their deformation are the thrust-nappe tectonic,the pop-up,the triangle zone ,the duplex,etc. Multi-level decollement zones not only made the Longmenshan thrust belt develop many different deformation styles from deep place to shallow place,but also made some local areas have the superimposition of the tectonic deformation apparently. This study indicates that the multi-level de-collement zones have a very important effect on the shaping and evolution of the Longmenshan thrust belt.  相似文献   

14.
Synthetical research has been done on the geological thermal history of the Turpan-Hami Basin by using vitrinite reflectance, fluid inclusion geothermometry and fission track. The geotcmperature of the Turpan-Hami Basin has the character that suggests higher temperature in the past, in the east and south of the basin, and in the areas of large-fracture, and lower temperature in the present day and in the west and north of the basin. This feature is controlled by the difference of burial depth of basement and heat flow values, which made Permian source rock mature in the late Triassic and Jurassic source rock mature at the end of Jurassic and the early Tertiary. Project supported by the Chinese Tnrpan-Hami Oil Field cooperation project.  相似文献   

15.
Deformation of the Circum-Rhodope Belt Mesozoic (Middle Triassic to earliest Lower Cretaceous) low-grade schists underneath an arc-related ophiolitic magmatic suite and associated sedimentary successions in the eastern Rhodope-Thrace region occurred as a two-episode tectonic process: (i) Late Jurassic deformation of arc to margin units resulting from the eastern Rhodope-Evros arc–Rhodope terrane continental margin collision and accretion to that margin, and (ii) Middle Eocene deformation related to the Tertiary crustal extension and final collision resulting in the closure of the Vardar ocean south of the Rhodope terrane. The first deformational event D1 is expressed by Late Jurassic NW-N vergent fold generations and the main and subsidiary planar-linear structures. Although overprinting, these structural elements depict uniform bulk north-directed thrust kinematics and are geometrically compatible with the increments of progressive deformation that develops in same greenschist-facies metamorphic grade. It followed the Early-Middle Jurassic magmatic evolution of the eastern Rhodope-Evros arc established on the upper plate of the southward subducting Maliac-Meliata oceanic lithosphere that established the Vardar Ocean in a supra-subduction back-arc setting. This first event resulted in the thrust-related tectonic emplacement of the Mesozoic schists in a supra-crustal level onto the Rhodope continental margin. This Late Jurassic-Early Cretaceous tectonic event related to N-vergent Balkan orogeny is well-constrained by geochronological data and traced at a regional-scale within distinct units of the Carpatho-Balkan Belt. Following subduction reversal towards the north whereby the Vardar Ocean was subducted beneath the Rhodope margin by latest Cretaceous times, the low-grade schists aquired a new position in the upper plate, and hence, the Mesozoic schists are lacking the Cretaceous S-directed tectono-metamorphic episode whose effects are widespread in the underlying high-grade basement. The subduction of the remnant Vardar Ocean located behind the colliding arc since the middle Cretaceous was responsible for its ultimate closure, Early Tertiary collision with the Pelagonian block and extension in the region caused the extensional collapse related to the second deformational event D2. This extensional episode was experienced passively by the Mesozoic schists located in the hanging wall of the extensional detachments in Eocene times. It resulted in NE-SW oriented open folds representing corrugation antiforms of the extensional detachment surfaces, brittle faulting and burial history beneath thick Eocene sediments as indicated by 42.1–39.7 Ma 40Ar/39Ar mica plateau ages obtained in the study. The results provide structural constraints for the involvement components of Jurassic paleo-subduction zone in a Late Jurassic arc-continental margin collisional history that contributed to accretion-related crustal growth of the Rhodope terrane.  相似文献   

16.
The study of basement geochronology provides crucial insights into the tectonic evolution of oceans. However, early studies on the basement of the Xisha Uplift were constrained by limited geophysical and seismic data; Xiyong1 was the only commercial borehole drilled during the 1970 s because of the huge thickness of overlying Cenozoic strata on the continental margin. Utilizing two newly-acquired basement samples from borehole XK1, we present petrological analysis and zircon uranium(U)-lead(Pb) isotope dating data in this paper that enhance our understanding of the formation and tectonic features of the Xisha Uplift basement. Results indicate that this basement is composed of Late Jurassic amphibole plagiogneisses that have an average zircon 206 Pb/238 U age of 152.9±1.7 Ma. However, the youngest age of these rocks, 137±1 Ma, also suggests that metamorphism termination within the Xisha basement occurred by the Early Cretaceous. These metamorphic rocks have adamellites underneath them which were formed by magmatic intrusions during the late stage of the Early Cretaceous(107.8±3.6 Ma). Thus, in contrast to the Precambrian age(bulk rubidium(Rb)-strontium(Sr) analysis, 627 Ma) suggested by previous work on the nearby Xiyong1 borehole, zircons from XK1 are likely the product of Late Mesozoic igneous activity. Late Jurassic-Early Cretaceous regional metamorphism and granitic intrusions are not confined to Xisha; rocks have also been documented from areas including the Pearl River Mouth Basin and the Nansha Islands(Spratly Islands) and thus are likely closely related to large-scale and long-lasting subduction of the paleo-Pacific plate underneath the continental margins of East Asia, perhaps the result of closure of the Meso-Tethys in the South China Sea(SCS). Controversies remain as to whether, or not, the SCS region developed initially on a uniform Precambrian-aged metamorphic crystalline basement. It is clear, however, that by this time both Mesozoic compressive subduction and Cenozoic rifting and extension had significantly modified the original basement of the SCS region.  相似文献   

17.
The compositions of Jurassic detrital garnets in Hefei Basin are complicated. Contents of the end member are from zero to 43% for pyrope, from less than 1% to 50% for grossular, from 2% to 92% for almandine, and from zero to 88% for spessartine. Part of relatively pyrope-rich detrital garnets might be originated from high pressure-ultrahigh pressure metamorphic rocks. Contents of spessartine in garnets from the present metamorphic rocks of the Dabie Mountains, including the greenschists of Foziling Group, are lower than 30%. Therefore, they would not be the source of the spessartine-rich detrital garnets in the Jurassic sedimentary rocks of the Hefei Basin. Chemical compositions of the Jurassic detrital garnets in the Hefei Basin have some characteristics in the distribution with strata, which can be applied to study of the sedimentary filling sequence and stratigraphic correlation.  相似文献   

18.
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   

19.
Based on the drilling data,the geological characteristics of the coast in South China,and the interpretation of the long seismic profiles covering the Pearl River Mouth Basin and southeastern Hainan Basin,the basin basement in the northern South China Sea is divided into four structural layers,namely,Pre-Sinian crystalline basement,Sinian-lower Paleozoic,upper Paleozoic,and Mesozoic structural layers.This paper discusses the distribution range and law and reveals the tectonic attribute of each structural layer.The Pre-Sinian crystalline basement is distributed in the northern South China Sea,which is linked to the Pre-Sinian crystalline basement of the Cathaysian Block and together they constitute a larger-scale continental block—the Cathaysian-northern South China Sea continental block.The Sinian-lower Paleozoic structural layer is distributed in the northern South China Sea,which is the natural extension of the Caledonian fold belt in South China to the sea area.The sediments are derived from southern East China Sea-Taiwan,Zhongsha-Xisha islands and Yunkai ancient uplifts,and some small basement uplifts.The Caledonian fold belt in the northern South China Sea is linked with that in South China and they constitute the wider fold belt.The upper Paleozoic structural layer is unevenly distributed in the northern South China.In the basement of Beibu Gulf Basin and southwestern Taiwan Basin,the structural layer is composed of the stable epicontinental sea deposit.The distribution areas in the Pearl River Mouth Basin and the southeastern Hainan Basin belong to ancient uplifts in the late Paleozoic,lacking the upper Paleozoic structural layers.The stratigraphic distribution and sedimentary environment in Middle-Late Jurassic to Cretaceous are characteristic of differentiation in the east and the west.The marine,paralic deposit is well developed in the basin basement of southwestern Taiwan but the volcanic activity is not obvious.The marine and paralic facies deposit is distributed in the eastern Pearl River Mouth Basin basement and the volcanic activity is stronger.The continental facies volcano-sediment in the Early Cretaceous is distributed in the basement of the western Pearl River Mouth Basin and Southeastern Hainan Basin.The Upper Cretaceous red continental facies clastic rocks are distributed in the Beibu Gulf Basin and Yinggehai Basin.The NE direction granitic volcanic-intrusive complex,volcano-sedimentary basin,fold and fault in Mesozoic basement have the similar temporal and spatial distribution,geological feature,and tectonic attribute with the coastal land in South China,and they belong to the same magma-deposition-tectonic system,which demonstrates that the late Mesozoic structural layer was formed in the background of active continental margin.Based on the analysis of basement structure and the study on tectonic attribute,the paleogeographic map of the basin basement in different periods in the northern South China Sea is compiled.  相似文献   

20.
The Helan Mountain lies in the northwest margin of Ordos Basin and its uplift periods have close relations with the tectonic feature and evolution of the basin. There are many views on the uplift time of Helan Mountain, which is Late Triassic and Late Jurassic. It is concluded by the present strata, magmatic rock and hot fluid distribution that the Helan Mountain does not uplift in Late Triassic to Middle Jurassic but after Middle Jurassic. Through the research of the sedimentary strata and deposit rate in Yinchuan Graben which is near to the Helan Mountain, it is proved that the Helan Mountain uplifts in Eocene with a huge scale and in Pliocene with a rapid speed. The fission track analysis of apatite and zircon can be used to determine the precise uplift time of Helan Mountain, which shows that four stages of uplifting or cooling Late Jurassic to the early stage of Early Cretaceous, mid-late stage of Early Cretaceous, Late Cretaceous and since Eocene. During the later two stages the uplift is most apparent and the mid-late stage of Early Cretaceous is a regional cooling course. Together with several analysis ways, it is considered that the earliest time of Helan Mountain uplift is Late Jurassic with a limited scale and that Late Cretaceous uplift is corresponding to the whole uplift of Ordos Basin, extensive uplift happened in Eocene and rapid uplift in Pliocene.  相似文献   

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