成都盆地新生代大邑砾岩的沉积特征

通过对龙门山前陆盆地大邑砾岩的发育层序、沉积特征及物源的分析，建立其垂向相序，总结出大邑砾岩的沉积具冲积扇相的特点；恢复大邑砾岩发育时期的古地貌，推断其至少由三个冲积扇组成：古岷江扇，古青衣江扇，古玉溪扇。同时，结合测年资料，指出大邑砾岩是上新世一早更新世的整合沉积相，有别于全球其他地区同期的不整合事件。大邑砾岩沉积之后，新构造运动活动强烈。     

日喀则群沉积厚度、沉积速率及剥蚀速率

通过对日喀则弧前盆地日喀则群沉积的详细研究,对日喀则群的沉积厚度、沉积速率做了近似的计算.日喀则群现今保存下来的厚度平均为3 000 m,恢复其原始沉积厚度为4 800 m,从而计算得出沉积速率为34 cm/ka(未脱压校正值为22 cm/ka),主沉积期的沉积速率为308 cm/ka(未脱压校正);并且与其他几个白垩纪同类盆地进行对比,得出白垩纪此类盆地发育过程中,沉积速率的平均值为27.75 cm/ka.根据近似恢复的弧前盆地和剥蚀区的范围,计算得出沉积盆地沉积物充填总量最小90 750 km3,最大137 500 km3;物源区剥蚀速率最小0.1 mm/a,最大0.45 mm/a.     

内蒙古苏尼特左旗早古生代乌华敖包弧前盆地的识别及其古地理意义

通过野外观察和剖面测量、锆石年代学分析及沉积相分析等方法, 对新发现的苏尼特左旗乌华敖包地区浅变质岩系进行研究, 并探讨其古地理意义。结果表明, 该套浅变质岩系以变质火山岩、变质砂岩与大理岩互层为特征, 构成 3 个沉积旋回, 代表弧前盆地中?晚期向上变浅的海相火山喷发?沉积环境; 多层火山岩的出现揭示持续的岩浆活动; 火山岩锆石U-Pb定年结果为454.4±4.1 Ma, 与北部早古生代宝力道岛弧带的岩浆岩年龄相近, 表明该套浅变质岩系与早古生代岛弧岩浆活动有关。由于该岩系位于北部宝力道岛弧岩浆岩带与南部混杂岩带之间, 因此其古地理位置应属早古生代弧前盆地。乌华敖包浅变质岩系的层序、成分、时代和位置特征揭示研究区曾存在弧前盆地。根据早古生代地层、岩浆岩和变质特征, 认为弧前盆地经历了俯冲及碰撞两个阶段。     

Characteristics of Early Eocene radiolarian assemblases of the Sasa area, southern Tibet and their constraint on the closure history of the Tethys

Quantitative analysis of Early Eocene radiolarian assemblages discovered in the sedimentary melange （accretionary prism） of the Saga area, southern Tibet provides new information to constrain the timing of Tethys closure and the initial collision of India and Eurasia. The radiolarian species of Saga include Amphisphaera coronata （Ehrenberg）, Buryella hannae Bak ＆ Barwicz-Piskorz, Buryella clinata Foreman, Buryella tetradica Foreman, Calocycloma ampulla （Ehrenberg）, Lamptonium fabaeforme constrictum Riedel and Sanfilippo, Lamptonium pennatum Foreman, Lithomespilus coronatus Squinabol and Lamptonium （？） colymbus Foreman. The adequate and reliable correlation of these radiolarians specimens indicates that the assemblage is of Early Eocene in age. The age and depositional environment of these radiolarians testify that deep ocean basins existed between India Plate and Asia Plate during the Early Eocene. The complete closure of Tethys must have taken place at least after the Early Eocene.     

源下油气成藏主控因素与成藏模式——以北部湾盆地乌石凹陷乌石17X下始新统流沙港组三段油藏为例

北部湾盆地乌石凹陷下始新统流沙港组三段发育源下断块油藏,其原油来自上覆流沙港组二段超压成熟烃源岩,其成藏受"源储压差"、沉积相和有效断块圈闭三因素控制。"源储压差"控制了油气运移方向,油气由流沙港组二段源内超压区向下部、侧向流沙港组三段常压区运移,在断裂圈闭带中聚集。流沙港组二段超压还起到了封盖油气作用。流沙港组三段近岸水下扇扇中辫状水道微相储层物性较好,是"甜点"储层。下始新统流沙港组三段具有"高压源、源封盖、源储接触"的源下油气成藏模式。乌石凹陷东部流沙港组三段始新世裂陷幕断裂圈闭带是"源下"油气富集的区带。     

Early tectonic uplift of the northern Tibetan Plateau

The Hexi Corridor is the northmost foreland basin of the Tibetan Plateau and its formation is controlled by the northern marginal fault of Tibet, Altyn Tagh Fault （ATF）-North Qilian Shan marginal Fault （NQF）, and the southern Kuantan Shan-Longshou Shan Fault （KLF）. So its study is important to understanding the mechanism of Tibet formation and its influence on global climate change. The oldest Cenozoic sediments in the Corridor is the Huoshaogou Formation which consists of terrigenous fine conglomerate, sandstone, sandy mudstone and mudstone, depositing in al- luvial to lacustrine and fan delta sedimentary environments. Detailed paleomagnetic measurements of this sequence at Yumen clearly reveal eleven pairs of normal and reversed polarities. Fossil mammals found around the section support that most of the observed polarities can be well correlated with chrons between 13n and 18r of the standard geomagnetic polarity time scale, yielding ages of 40.2-33.35 Ma. The mean declinations of this sequence and its immediately above stratigraphy indicate an 18.3° rapid clockwise rotation of the Hexi Corridor. Since this sequence has been strongly folded and is capped by an angular unconformity, we think that the presence of the thick alluvial fan conglomeration at the bottom of the foreland basin may indicate the initial deformation and uplift of the northern Qilian Shan. This process could occur at latest at 40.2 Ma, driven by the faults NQF and KLF that thrust onto the Hexi corridor respectively from its southern and northern margins. These faults are in an early response to the collision of India with Asia, while the unconformable termination and rotation of the Huoshaogou Formation at -33.35 Ma indicate other early episode of rapid tectonic deformation and uplift of the northern Tibet.     

The age of the plant fossil assemblage in the Liuqu Conglomerate of southern Tibet and its tectonic significance

The Liuqu Conglomerate, situated to the south of Yarlung Tsangbo Suture Zone (YTSZ), is a suit of molasse formed in a foreland basin of the Himalayan orogenic belt after the collision between the two plates of the Indian and Eurasion. It is of great significance in constraining the younger limit time of the collision of the two plates and providing stratigraphic evidence to reveal the post?collisional tectonic evolution and uplifting history of the Tibet plateau. However, the age of this molasse suit and its correlation to other synchronous strata distributed in southern Tibet have been in great disputes for a long time. Especially in recent years, argues on its ages are growing violently with the recognition of the great sedimentary tectonic significances of this molasse. During the field work carried out recently on this molasse suit, a lot of plant fossils were found preserved in fairly good conditions in the upper part of this strata, which is of great help in determining its age. By identification, the assemblage of the plant fossils belongs to a tropic to subtropic flora developed in the southern margin of the Northern Hemisphere supercontinent during the Middle to Later Eocene, which can provide good constraint on its formation age. This paper is to give a brief introduction of the plant assemblage and its age, and to discuss their tectonic significances.     

内蒙古桌子山中奥陶统拉什仲组岩石特征及沉积环境

 内蒙古桌子山中奥陶统拉什仲组主要为一套灰黑色页岩、灰绿色砂岩、粉砂岩及褐灰色砾岩,可分为3个岩性段。通过对岩性、沉积构造、古生物及地球化学等资料的分析,认为拉什仲组沉积环境主要为大陆斜坡至盆地边缘。拉什仲组的沉积相主要为斜坡相及盆地边缘相,并进一步可划分为斜坡上部和斜坡下部2个亚相,近端水道沉积、远端水道沉积及天然堤沉积3个微相。整体上,拉什仲组岩性剖面构成了一完整的海进—海退沉积旋回。     

南堡凹陷北部始新世米兰科维奇记录及其对沉积响应的指示意义

古近纪时期的板块运动造就了渤海湾盆地洼隆相间的构造格局,需要从地质年代学角度研究单一湖盆的层序地层格架及其内部的沉积响应。以南堡凹陷高柳地区始新统为例,利用标准井预处理的自然伽马曲线,利用频谱分析、连续小波变换和滑动频谱分析等方法识别蕴藏的米兰科维奇旋回,基于绝对地质年代锚点,建立天文年代标尺,估算沉积速率,重建古湖平面变化和古沉积物供给能力,从区域沉积体系演化的角度讨论米兰科维奇记录对沉积响应的指示意义。结果表明：(1)始新统沉积序列受控于长偏心率、短偏心率、斜率和岁差周期,共识别出20个长偏心率周期,85个短偏心率周期,累计约8.1 Ma;(2)Es₃¹、Es₂、Es₁^x和Es₁^z亚段顶界面绝对地质年代分别为33.3、31.9、30.5、29.5 Ma,平均沉积速率约124.2 m/Ma;(3)湖平面于36.6～33.3 Ma大规模上升,于33.3～30.5 Ma持续下降,于30.5～28.5 Ma再次小幅回升,而36.6～28....     

西藏雅鲁藏布江一带中生代沉积盆地的演化

经过研究证实,在雅鲁藏布江蛇绿岩的南北两侧,有两套形成于雅鲁藏布江洋底盆地的沉积组合,它们不但形成于不同时代,而且属于不同构造环境下的产物。时代属于晚侏罗世到早白垩世的南侧沉积组合为放射虫硅质岩-层状玄武岩,其沉积特征类似于太平洋洋隆类型,反映了它可能是属于西藏特提斯快速扩张的产物。根据最近所发现的圆笠虫化石确定北侧一套的时代属于中白垩世,它是蛇绿质碎屑岩-枕状玄武岩组合,反映了一种类似于大西洋洋脊类型的、慢速扩张的板块构造环境。它是正常沉积接触关系覆于雅鲁藏布江蛇绿岩套之上。雅鲁藏布江蛇绿岩套是这个时期形成的洋壳的残留体。在晚白垩世时,雅鲁藏布江蛇绿岩被捕获在北部的冈底斯山弧前并且变为冈底斯南缘弧前盆地的基底。随后日喀则群浊积岩在其上堆积。     

First discovery and characterizations of late Cretaceous seep carbonates from Xigaze in Tibet, China

Hydrocarbon seeps,widely occurring in continental margins,have become increasingly focused owing to their close relationships with gas hydrates,strong greenhouse gas methane,and biological resources in extreme environments.Ancient hydrocarbon seeps have already been recognized from Devonian to Quaternary strata worldwide based on seep carbonates or seep-related fossil chemosynthetic assemblages.However,seep-related deposits are rarely found from ancient strata in the mainland China.Here,we report the first discovery of an ancient seep deposit,specifically late Cretaceous seep carbonates from Xigaze in Tibet,China.Xigaze seep carbonates,occurring as nodules,are enclosed in upper Cretaceous turbidite strata in Xigaze forearc basin.These carbonates are composed of authigenic carbonate(56.2% on average),clastic quartz and feldspar(27.3% on average),and clay minerals(chlorite,illite and smectite,16.5% on average).Clotted micrites,peloids and framboid pyrites are frequently observed,all of which are common in modern seep carbonates.The carbonates have negative δ13 C values varying from 27.7‰ to 4.0‰(V-PDB),suggesting that thermogenic methane is the primary carbon source.Ce/Ce* values revised by eliminating La effects show no real Ce anomaly,indicating the carbonates were primarily precipitated in a weak reducing environment.Overall,these features provide unequivocal evidences that the seafloor of Xigaze forearc basin developed hydrocarbon seeps in late Cretaceous.     

青海囊谦第三纪盆地沉积学特征

囊谦盆地位于青藏高原东部 ,研究程度较低 ,倘处于地层格架建立阶段。在野外工作的基础上全面叙述了地层的岩相特征、沉积体系、古流向等。指出盆地沉积环境为近源、快速堆积环境 ,沉积体系不对称分布且相变迅速 ,物源区单一性 ,古流向的变化表明了盆地的不断加大及控制盆地的扎曲断裂的持续活动性     

西藏札达盆地构造与沉积特征

札达盆地位于青藏高原南西部,是发育于喜马拉雅山内部的盆地。盆地北东侧以阿依拉日居断裂为边界,该断裂属逆冲性质。西北边界为曲松断裂,为一拆离断层。盆地西南主边界为藏南拆离系（STDS）,是盆地主控构造。盆地内部沉积了巨厚的第三纪地层,可以分为上下2个部分,即上部的湖相沉积和下部的河湖交互相沉积。湖相沉积是以泥岩为主的巨厚沉积;河湖交互相沉积以砾岩层的出现为标志,可分为3个沉积旋回。札达盆地的主控构造为伸展构造,但同时经受了垂直于造山带的挤压作用。     

Palaeo-altimetry of the late Eocene to Miocene Lunpola basin, central Tibet

The elevation history of the Tibetan plateau provides direct insight into the tectonic processes associated with continent-continent collisions. Here we present oxygen-isotope-based estimates of the palaeo-altimetry of late Eocene and younger deposits of the Lunpola basin in the centre of the plateau, which indicate that the surface of Tibet has been at an elevation of more than 4 kilometres for at least the past 35 million years. We conclude that crustal, but not mantle, thickening models, combined with plate-kinematic solutions of India-Asia convergence, are compatible with palaeo-elevation estimates across the Tibetan plateau.     

西昆仑早古生代构造演化及其对塔西南盆地的影响

在板块构造理论基础上，通过区内蛇绿岩、与俯冲有关的岩浆岩及相关沉积等综合研究，对西昆仑早古生代构造演化进行了重建：震旦纪－寒武纪西昆仑从塔里木大陆分裂出去，并在它们之间形成“昆仑洋”；寒武纪－奥陶纪“昆仑洋”洋壳向南俯冲于西仑之下，形成库地俯冲带、库地弧前盆地、西昆仑早古生代火山弧及麻扎－黑卡弧后盆地；志留纪－早泥盆世，“昆仑洋”消失，西昆仑早古生代火山弧与塔里木大陆碰撞，并形成塔里木前陆冲断带和泥盆纪前陆盆地磨拉石及塔里木大陆内泥盆纪的“红层相”     

西藏措勤中-新生代沉积盆地演化

措勤盆地位于西藏冈底斯地块中西段,是在古生界褶皱基底上发展起来的一个中-新生代盆地.通过对措勤盆地内发育的构造、地层、岩石及沉积相综合分析,讨论了措勤盆地与喜马拉雅构造带和班公-怒江构造带的对应演化关系,反演了措勤盆地的地质发展历史.其演化经历了盆地基底形成阶段(D-P)、复合弧后盆地演化阶段(J-E2)和高原隆升盆地消亡三个阶段(Es-现今).     

Paleocurrent analysis on the basal conglomerate of the model Changzhougou formation in Qian’an

The paleoflow direction of the basal conglomerate of the Changzhougou formation is obtained by the paleocurrent analysis of certain sedimentary structures, and the ancient sedimentary environment of the Qian'an Region is determined by observing the psephicity and gradation of gravel in conglomerate. The results show that the paleoflow direction is from northwest to southwest, and the paleocurrent data manifest a single-peak style in a rose diagram. The average paleoflow direction in the Qian'an region is 265°. The basal conglomerate is of littoral facies, and the sediments of conglomerates are mainly sourced from Shanhaiguan.     

惠民凹陷古近系碎屑岩储集体成因类型及特征分析

对惠民凹陷在古近系碎屑岩储集体的成因特征进行了分析研究.发现成因类型有:冲积扇、河流、近岸水下扇、扇三角洲、深水浊积扇、三角洲、三角洲前缘滑塌浊积扇以及滨浅湖滩坝.储层岩石类型有砾岩、含砾砂岩、中细砂岩及粉砂岩.不同成因类型的碎屑岩储集体成分成熟度和结构成熟度差异较大,三角洲河口坝及滨浅湖滩坝砂体成分成熟度和结构成熟度最高.不同成因类型储集体的物性特征不同,三角洲平原分支河道、(扇)三角洲前缘水下分流河道及河口坝砂体储集物性最好,其次为(扇)三角洲前缘席状砂及滨浅湖滩坝砂体,近岸水下扇和浊积扇砂体物性相对较差.     

东濮凹陷碎屑岩沉积充填特征及变化对构造活动的响应

东濮凹陷为渤海湾盆地西南端的一陆相断陷湖盆,具有砂层薄、粒度细和非均质性显著的沉积特征。盆地在古近系的沉积演化受频繁构造活动影响显著。通过研究古近系沙河街组碎屑岩尤其是盆缘的砾岩特征,分析不同构造变革期沉积物组成类型特征及变化,明确不同时期沉积充填对断裂活动的响应:盆地形成初期兰聊断裂的活动,东西两侧物源类型差异小,组成相对单一,均以中生界碎屑岩为主;随着构造活动频发和流域面积的增加,在沙三下文西、卫西、观城、马寨、马厂和三春集等断裂活动,湖盆水体加深,并出现多个沉降中心,东西两侧沉积体系和物源组成发生变化,砾石成分显示西侧物源中上古生界碎屑岩和下古生界碳酸盐岩、中生界火山岩和太古界基底变质岩逐渐增加,东侧上古生界物质比例增加;沙三中长垣断层和黄河断层活动造成南北差异显著,出现多源混合,砾石成分复杂度最高;至沙二期北部文东、卫东、文明寨等断层活动,东部洼陷沉降幅度增加,东侧近源物质大量充填砾石成分以上古生界碎屑岩和下古生界碳酸盐岩为主。沉积物的变化直接反映了各时期构造活动的强弱记录了盆地的演化历史,对认识同沉积断裂活动影响下储层砂体的发育及烃源岩的展布具有重要意义。     

二连盆地蒙古林砾岩油藏微相特征及对开发的影响

综合运用岩心观察描述、分析化验、测井等资料,探讨了二连盆地蒙古林砾岩油藏沉积微相特征,并深入研究了不同微相的沉积特征、电性特征、储集特征及展布规律;结合生产动态分析及油水运移规律研究,就沉积微相对油水运动规律的影响等进行综合研究,探索剩余油分布规律及其影响因素.研究结果表明,该区发育辫状河三角洲平原、前缘亚相的五种沉积微相砂砾岩体,不同微相具有各自特色的岩性及储集条件;储层的含油性、砾岩体的分布等,乃至油水运移规律、剩余油分布等,均明显受到沉积微相的控制.