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阿拉善地块位于中亚造山带南缘,是研究中亚造山带南缘二叠纪构造背景及演化的关键地区。本研究在阿拉善地块东北缘狼山地区野外调查的基础上,对狼山地区大红山组地层进行古流向、碎屑锆石LA-ICP-MS U-Pb定年和砂岩碎屑组分分析。研究表明砾石最大扁平面倾向为SWW—NWW,指示大红山组地层沉积时的古水流的流向总体呈现自西向东,推测大红山组砾石主要来自狼山西部地区。砂岩中碎屑锆石最小年龄峰值为275 Ma和278 Ma,表明大红山组沉积时代不早于中二叠世早期。砂岩的碎屑组分分析和碎屑锆石年龄谱指示大红山组可能来自于晚古生代诺尔公—狼山弧,砾石的古流向分析和碎屑锆石年龄谱推测大红山组砾石极有可能来自于阿拉善地块前寒武纪变质基底。结合诺尔公—狼山构造带晚古生代大陆岩浆弧的存在,认为二叠系大红山组地层沉积于弧背前陆盆地的构造背景。 相似文献
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Paleocurrent indicator data collected in field work were used to study the early Cenozoic regional paleodrainage patterns in the Hob Xil basin in northern Tibetan plateau. The paleocurrent directions of the Eocene Fenghuoshan Group obviously show that the flows were northward with a unidirectional dispersal pattern. This probably reflects the uplift of the Qiangtang terrain during the initial basin deposition period and indicates that the Tanggula Moutains occurred as topographic highlands at least in the Eocene. Paleoflows of the Oligocene Yaxicuo Group were dominantly oriented to the north and then flowed eastwards during its late deposition. This regional variability of paleodrainage patterns of the Yaxicuo Group is interpreted to record the dispersal style of sediments from transverse rivers to longitudinal river systems. It is inferred that the Oligocene uplift of the Kunlun Mountains obstructed by northward paleoflows and created longitudinal river systems parallel to the orogenic belts. The temporal and spatial changes of the paleodrainage patterns suggest that the northern boundary of the Tibetan plateau during the early Cenozoic was situated in the Hoh Xil area and its uplift has progressed northwards through time. 相似文献
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西秦岭关家沟组地层时代、物源及其构造响应 总被引：1，自引：0，他引：1
在西秦岭关家沟组贾昌沟砂板岩所夹的硅质岩层中发现晚石炭世和晚二叠世的古生物化石;在关家沟组砾岩中所采的花岗质和火山质砾石,利用氩-氩(40Ar/39Ar)法测年所获得的年龄为晚三叠世。对关家沟组物源及其古水流分析,其古水流方向230°~356°,其物源主要来自南东侧活动大陆边缘的碧口岛弧,且秦岭全面碰撞造山期为早中生代。由此,初步推测关家沟组形成时代可能与秦岭全面碰撞造山为同期——早中生代。 相似文献
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Basin-fill sequences of Mesozoic typical basins in the Yanshan area, North China may be divided into four phases, reflecting lithosphere tectonic evolution from flexure (T3), flexure with weak rifting (J1+2), tectonic transition (J3), and rifting (K). Except the first phase, the other three phases all start with lava and volcaniclastic rocks, and end with thick coarse clastic rocks and/or conglomerates, showing cyclic basin development rather than simple cyclic rift mechanism and disciplinary basin-stress change from extension to compression in each phase. Prototype basin analysis, based on basin-fill sequences, paleocurrent distribution and depositional systems, shows that single basin-strike and structural-line direction controlling basin development had evidently changed from east-west to northeast in Late Jurassic in the Yanshan area, although basin group still occurred in east-west zonal distribution. Till Early Cretaceous, main structural-line strike controlling basins just turned to northeast by north in the studied area. 相似文献
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通过对青藏高原东北部11个新近纪沉积盆地的沉积相演化、古流向和物源演变的详细对比研究,揭示了研究区新近纪4次沉积演变与构造隆升的响应.①中新世早期(23～19.5Ma):阿牙克库木湖、柴达木、德令哈和酒泉盆地的古流向和物源分析表明东昆仑和阿尔金已经抬升成剥蚀区.循化、贵德和临夏等盆地物源和古流向指示西秦岭和拉脊山也已成为隆起区.区域上整体地势差异不显著.②中新世早中期(17.5～15Ma):区域湖盆面积扩大,阿牙克库木湖、索尔库里、柴达木和酒泉盆地的资料反映东昆仑、阿尔金和祁连山已经全面隆升,贵德循化、临夏盆地的古流向反映为盆地周缘型,指示西秦岭和拉脊山明显抬升,区域差异隆升造成盆地凹陷扩张进入湖泛期.③中新世中晚期(10～7Ma):阿牙克库木湖、索尔库里、柴达木和酒泉盆地沉积物的粒径和沉积速率增大,与热年代学证据一致,揭示出阿尔金山和祁连山进一步快速隆升.贵德、循化和临夏盆地古流向和物源反映为显著的多源性,除西秦岭和拉脊山外,位于循化和临夏两盆地间的积石山也开始隆起.④上新世(5.3Ma以来):索尔库里、柴达木和酒泉盆地古流向没有明显变化,沉积速率和粒径继续增大,阿尔金和祁连山加速隆升为高海拔地貌.贵德盆地主物源区是拉脊山.区域上,地势差异加强,湖盆被肢解后逐步萎缩消亡. 相似文献
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Precise statistical models are proposed for the distribution of paleocurrent directions in distributary systems. These models are based on a von Mises distribution for directions of paleocurrents in a system. The method of maximum likelihood is used to obtain an estimated position and confidence regions for the apex of the system. Both axial data (where only the trend of the paleocurrent is known) and directional data (where the direction of paleoflow is known) can be used. These models have been applied to two fluvial distributary systems in flat-lying Miocene deposits in the Ebro Basin, northern Spain. The estimate of the position of the apex of one of these systems is in good agreement with the position at the basin margin predicted from sedimentary facies information. The estimate of the position of the apex of the second system lies outside of the sedimentary basin; this result is considered to indicate that the distributary system had several feeder points along the basin margin, a situation which is predicted also from facies distributions. This statistical procedure can be used successfully on small data sets of around a hundred paleocurrent readings provided that they are scattered evenly across the area or lie in a wide arc. 相似文献