Extensional structures of the Nan'an Basin in the rifting tip of the South China Sea: Implication for tectonic evolution of the southwestern continental margin

Nan'an Basin is a giant hydrocarbon basin,but its tectonic division scheme and associated fault systems has not been well understood.Based on newly acquired seismic data from the southwestern margin of the South China Sea,this study analyzed the structural units,tectonic feature and geodynamics of the sedimentary basin.The new data suggests that the Nan0 an Basin is a rift basin oriented in the NE-SW direction,rather than a pull-apart basin induced by strike-slip faults along the western margin.The basin is a continuation of the rifts in the southwest South China Sea since the late Cretaceous.It continued rifting until the middle Miocene,even though oceanic crust occurred in the Southwest Subbasin.However,it had no transfer surface at the end of spreading,where it was characterized by a late middle Miocene unconformity(reflector T3).The Nan'an Basin can be divided into eight structural units by a series of NE-striking faults.This study provides evidences to confirm the relative importance and interplay between regional strike-slips and orthogonal displacement during basin development and deformation.The NE-SW-striking dominant rift basin indicates that the geodynamic drivers of tectonic evolution in the western margin of the South China Sea did not have a large strike-slip mechanism.Therefore,we conclude that a large strike-slip fault system did not exist in the western margin of the South China Sea.

TECTONIC EVOLUTION OF THE EOCENE DROSH-VOLCANO-SEDIMENTARY BASIN IN NW-KOHISTAN ISLAND ARC TERRANE, HINDUKUSH, N. PAKISTAN

In NW Himalayas, the suture zone between the collided Indian and the Karakoram plates is occupied by crust of the Cretaceous Kohistan Island\|Arc Terrane [1] . Late Cretaceous (about 90Ma) accretion with the southern margin of the Karakoram Plate at the site of the Shyok Suture Zone turned Kohistan to become an Andean\|type margin. The Neotethys was completely subducted at the southern margin of Kohistan by Early Tertiary, leading to collision between Kohistan and continental crust of the Indian plate at the site of the Main mantle thrust.More than 80% of the Kohistan terrane comprises plutonic rocks of (1) ultramafic to gabbroic composition forming the basal crust of the intra\|oceanic stage of the island arc, and (2) tonalite\|granodiorite\|granite composition belong to the Kohistan Batholith occupying much of the intermediate to shallow crust of the terrane mostly intruded in the Andean\|type margin stage [2] . Both these stages of subduction\|related magmatism were associated with volcanic and sedimentary rocks formed in Late Cretaceous and Early Tertiary basins. This study addresses tectonic configuration of Early Tertiary Drosh basin exposed in NW parts of the Kohistan terrane, immediately to the south of the Shyok Suture Zone.

FROM BACK-ARC BASIN TO BACK-ARC FORELAND BASIN—THE SEDIMENTARY BASIN AND TECTONIC EVOLUTION OF THE LATE CALEDONIAN—EARLY HERCYNIAN STAGES IN CORRIDOR AND NORTH QILIAN MTS

Qilian orogenic belt is a typical orogenic belt formed by polycyclic collisions between the North China plate and Qaidam microplate. Qilian ocean originated from the rift of the late Proterozoic Rodinia continent(Pangea\|850), evolved through rift basin and became an archipelagic ocean in the Caledonian stage. The Lower Proterozoic strata in Qilian area are mid\|high\|rank metamorphic rocks that constitute the metamorphic basement of the area. The “Huangyuan Movement" (in South Qilian and Central Qilian) and "Alashan Movement" (in North Qilian) in the latest Late Proterozoic formed a regional unconformity. The middle Proterozoic in the area are mudstones and carbonate rocks with stromatolites and ooids. The Qingbaikou System of the upper Proterozoic in the North Qilian and Corridor region is also mudstone and carbonate rock with stromatolites. The Qingbaikou System in Central Qilian is sandstones and mudstones. There are alkaline and tholeiite in the Sinian System in North Qilian and Corridor. The contact between Qingbaikou System and Sinian System is a regional unconformity (Quanji Movement). Qilian ocean began to rift away in Caledonian tectonic stage on the Pre\|Sinian basement.

STUDY ON SEDIMENTARY-TECTONIC EVOLUTION IN THE NORTH QAIDAM BASIN,QINGHAI PROVINCE

Jurassic deposition was extensively developed in the northern Qaidam basin.According to sequence stratigraphical analysis of outcrops,the Jurassic profile in the Dameigou area can be divided into 6 sequences.Sequences 1 and 4 consist of lowstand,water transgression and highstand systems tracts,and sequences 2,3 and 5 consist of lowstand and transgression systems tracts.However,sequence 6 only consists of a lowstand systems tract.The development of depositional sequences is controlled by lake level changes and basement faulting,which continued to be active in the Jurassic. The result of sedimentary－ tectonic evolution research indicates that the Qaidam Basin is a fault subsidence.This kind of basin framework determined that the coal－ forming environment would occur on the north side of the northern boundary fault of the Qaidam Basin and on the south side of the Lingjian fault, and the source rock would develop in the central subsidence belt between the two faults.

Tectonic relationship between the Kelameili range and the Dajing depression: Insights into the Carboniferous tectonic-sedimentary framework

Based on comprehensive analysis of typical outcrops, latest deep wells drilled and high resolution seismic profiles in the study area, we examined the geologic structure of the Kelameili range, and analyzed the structural relationship between the Kelameili range and the Dajing depression, and discussed the tectonic-sedimentary framework in different periods of Carboniferous by using axial surface analysis and balanced section techniques. Understandings in three aspects are achieved:(1) The study area experienced five stages of compressional tectonic movements, the Early Carboniferous, the Late Carboniferous, the Middle-Late Permian, Late Cretaceous and Paleogene, and three stages of extensional tectonic movements, the middle-late Early Carboniferous, the middle-late Late Carboniferous and Early Permian. At the end of the Early Permian and the Mid-Late Cretaceous, the tectonic wedges moved southward respectively.(2) The Kelameili range and Dajing depression had the first basin-range coupling during the early Early Carboniferous, basin-range decoupling in the following middle-late Early Carboniferous to the Early Permian, then basin-range strong recoupling in the Middle Permian, and the basin-range coupling had been inherited in the subsequent Indosinian, Yanshanian and Himalayan movements.(3) During the early Early Carboniferous, the study area was a foreland basin where the Dishuiquan Formation source rock developed;in mid-late Early Carboniferous, a series of NW-and NWW-trending half-garben fault basins developed, where the Songkaersu Formation volcanic reservoir formed. In late Early Carboniferous, the study area entered into depression basin stage after rifting, and the Shuangjingzi Formation source rock developed;in the mid-late Late Carboniferous, Batamayineishan fault basin emerged, and the Upper-Carboniferous volcanic reservoir was formed, affected by the tectonic compression during late Carboniferous and Mid-Permian, the Batamayineishan Formation suffered extensive erosion, and only partially remains in the piedmont depression zone.

Extensional Tectonics, Rifting, Formation of Sedimentary Basins, Cretaceous Volcanism, Emplacement of Dyke Swarms and Development of Hydrocarbon Pools: Case Studies from Peninsular India and Indian Ocean Region

Prolonged extensional regime in peninsular India resulted in formation of rift and grabens,elongated basins and Gondwana sedimentation along them.Downward progression of rift related faults caused decompression

Reconstruction of the Triassic Tectonic Lithofacies Paleogeography in Qiangtang Region, Northern Qinghai-Tibet Plateau, China

The Triassic petrostratigraphic system and chronologic stratigraphic sketch have been updated and perfected in the Qiangtang area, Qinghai-Tibet Plateau based on the integrated 1：250000 regional geological survey and the latest research progeny. The first finished 1：3000000 Triassic tectonic lithofacies paleogeographic maps in the Qiangtang area shows that the Triassic tectonic unit in the Qiangtang area can been divided into three parts from north to south： northern Qiangtang block; Longmucuo-Shuanghu suture zone; and southern Qiangtang block. The early-middle Triassic tectonic paleogeography in the Qiangtang area is divides into three sub- units： northern Qiangtang passive continental marginal basin （NQPB）, Longmucuo- Shuanghu residual basin （LSRB） and southern Qiangtang residual basin （SQRB）. The NQPB can be subdivided into four paleogeography units： The Tanggula-Zangxiahe shallow and bathyal sea; The Wangquanhe- Yingshuiquan carbonate platform; The Rejuechaka-Jiangaidarina littoral- shallow sea; and Qiangtang central uplift. The above units of The NQPB possess EW trend, geomorphology high in the south and low in the north, the seawater depth northward. The basinal paleo-current direction is unidirectional, and basinal tectonic subsidence center is in accord with the depo-center, located in the Tanggula-Zangxiahe belt, north of the basin. The sedimentation and tectonic evolution of the NQPB are characterized with passive continental marginal basin. The Qiangtang central orogenic denuded area （ancient land） may be as a sedimentary materials source of the NQPB. SQRB can be divided into two units： Duoma carbonate platform and southern Qiangtang neritic-deep sea. The late Triassic tectonic paleogeography in the Qiangtang area is the framework of the ＂archipelagic-sea＂ as a whole, and it may be divided into three sub-units： northern Qiangtang back- arc foreland basin（NQFB）, Longmucuo-Shuanghu residual basin（LSRB） and southern Qiangtang marginal-sea basin（SQMB）. Thereinto, NQFB can be divided into five paleogeography units： the Zangxiahe-Mingjinghu bathyal basin characterized with the flysch; the Tanggula shallow-sea shelf with the fine-clastics; the Juhuashang platform with carbonates; the Tumenggela-Shuanghu coastal- delta with coal-bearing clastics and the Nadigangri- Geladandong arc with volcanics and tuffs. In transverse section, the NQFB fills is wedge-shaped, and the sediments characterized with thicker in north and thinner in south, and with double materials derived from the Ruolagangri orogenic belt in north and the Shuanghu central orogenic belt in south. The late Triassic depocenter of NQFB is located in the middle of the basin, the Yakecuo-Bandaohu-Quemocuo belt, but the subsidence center in the north, the Zangxiahe- Mingjinghu belt, and basinal tectonic subsidence center not concordant with the depo-center. Late Triassic, the SQMB may be divided into three sub-units： Xiaochaka shallow-sea; Riganpeicuo platform~ and South Qiangtang southern bathyal basin. In transverse section, the basement of the SQMB is characterized with low in the northern and southern, but high in the middle; forming wedge shaped sediments with thicker in the north and thinner in the south; the sedimentary materials derived from the Qiangtang central uplift and Nadigangri arcs in north. The late Triassic subsidence centre of the SQMB is located in the northern （Xiaochaka area）, but the depocenter in the southern （Qixiancuo Suobucha area）. The sedimentation and tectonic evolution of the SQMB are characterized with marginal sea.

Earthquake-related Tectonic Deformation of Soft-sediments and Its Constraints on Basin Tectonic Evolution

The authors introduced two kinds of newly found soft-sediment deformation-synsedimentary extension structure and syn-sedimentary compression structure, and discuss their origins and constraints on basin tectonic evolution. One representative of the syn-sedimentary extension structure is syn-sedimentary boudinage structure, while the typical example of the syn-sedimentary compression structure is compression sand pillows or compression wrinkles. The former shows NW-SE-trendlng contemporaneous extension events related to earthquakes in the rift basin near a famous Fe-Nb-REE deposit in northern China during the Early Paleozoic （or Mesoproterozoic as proposed by some researches）, while the latter indicates NE-SW-trending contemporaneous compression activities related to earthquakes in the Middle Triassic in the Nanpanjiang remnant basin covering south Guizhou, northwestern Guangxi and eastern Yunnan in southwestern China. The syn-sedimentary boudinage structure was found in an earthquake slump block in the lower part of the Early Paleozoic Sailinhudong Group, 20 km to the southeast of Bayan Obo, Inner Mongolia, north of China. The slump block is composed of two kinds of very thin layers-pale-gray micrite （microcrystalline limestone） of 1-2 cm thick interbedded with gray muddy micrite layers with the similar thickness. Almost every thin muddy micrite layer was cut into imbricate blocks or boudins by abundant tiny contemporaneous faults, while the interbedded micrite remain in continuity. Boudins form as a response to layer-parallel extension （and/or layer-perpendicular flattening） of stiff layers enveloped top and bottom by mechanically soft layers. In this case, the imbricate blocks cut by the tiny contemporaneous faults are the result of abrupt horizontal extension of the crust in the SE-NW direction accompanied with earthquakes. Thus, the rock block is, in fact, a kind of seismites. The syn-sedimentary boudins indicate that there was at least a strong earthquake belt on the southeast side of the basin during the early stage of the Sailinhudong Group. This may be a good constraint on the tectonic evolution of the Bayan Obo area during the Early Paleozoic time. The syn-sedimentary compression structure was found in the Middle Triassic flysch in the Nanpanjiang Basin. The typical structures are compression sand pillows and compression wrinkles. Both of them were found on the bottoms of sand units and the top surface of the underlying mud units. In other words, the structures were found only in the interfaces between the graded sand layer and the underlying mud layer of the flysch. A deformation experiment with dough was conducted, showing that the tectonic deformation must have been instantaneous one accompanied by earthquakes. The compression sand pillows or wrinkles showed uniform directions along the bottoms of the sand layer in the flysch, revealing contemporaneous horizontal compression during the time between deposition and diagenesis of the related beds. The Nanpanjiang Basin was affected, in general, with SSW-NNE compression during the Middle Triassic, according to the syn-sedimentary compression structure. The two kinds of syn-sedimentary tectonic deformation also indicate that the related basins belong to a rift basin and a remnant basin, respectively, in the model of Wilson Cycle.

The Sedimentologic-Geotectonic Evolution in the Jiangsu-Zhejiang-Anhui Region

The Yangtze plate, extending from east to west in southern China, was formed about 800 Ma ago. Since the Sinian, two aulacogens trending east-northeast and connected at the east ends, have been initiated in the Jiangsu-Zhejiang-Anhui region on the east margin of the plate with a sedimentary sequence up to 10,000 m in thickness. At a later stage of sedimentologic evolution, flysch and molasse were produced. The flyseh was accumulated in the Late Ordovician, when the two aulacogens became bays that opened to the east; the elastic materials were derived from the Yangtze oldland on the northern and southern sides of the basins. The molasse was accumulated from the terminal Late Ordovician to the Middle Ordovician; the clastie materials came from an uplifted orogenic belt in the east. This indicates that a major change in the tectonic pattern of the basins has taken place.

CENOZOIC TECTONIC EVOLUTION AND GEODYNAMICS OF KEKEXILI BASIN IN NORTHERN QINGHAI—XIZANG PLATEAU

Kekexili basin, located in Northern Qinghai—Xizang plateau, has an area of over 4000km\+2 and is the largest Paleogene land facies basin in the plateau. With NWW\|SEE trend, Kekexili basin extends along the north side of the Jinshajiang suture. Its sediments, Fenghuoshan group, formed in E 1—E 3, show a shape of wedge with big thickness in south and small thickness in north. There are four sedimentary facies; fan\|delta and alluvial facies that occur in south, lake and lake\|delta facies, which do in north, in this basin. The north\|dipping Jinshajiang normal faults on the south margin of the basin have controlled the developments of the basin. The S—N compression at the end of E3 strongly folded the basin strata and transformed Jinshajiang normal faults into thrusts. In N1, widespread denudation occurred in the whole plateau. During N 2—Q, Kekexili area uplifted along with the whole plateau, besides, the thrusts in the basin showed coherent activity. We propose a geodynamical model for explaining the basin development. In early E,India plate, due to its colliding Eurasia plate, stopped its ocean crust subduction northward, then the subducted ocean lithosphere breaking away made the south margin area, most possibly to the south of Jinshajiang suture, of Eurasia plate isostatically uplift, so the north\|dipping Jinshajiang suture acted as normal faults and controled the north basin development. In late E, the isostatic uplift finished, the basin also gradually terminated its development .At the end of E, Jinshajiang normal faults became thrusts and the basin strata were folded under the northward compression of India plate. In the N1, India plate started incontinental subduction, the lower crust and lower mantle lithosphere of Qinghai—Xizang area underwent more intensive compression and deformation than its upper crust, and the induced transversal expansion in the lower lithosphere uplifted the upper crust and decreased its horizontal stress, which conduced the upper crust undergo denudation. During N 2—Q, convective removal of the lower mantle lithosphere of Qinghai\|Xizang area led to rapid uplift of this area.

The dependence of response spectrum on the tectonic ambient shear stress field

It has been analyzed the influence of the tectonic ambient shear stress value on response spectrum based on the previous theory. Based on the prediction equation BJF94 presented by the famous American researchers, CLB20, a new prediction formula is proposed by us, where it is introduced the influence of tectonic ambient shear stress value on response spectrum. BJF94 is the prediction equation, which mainly depends on strong ground motion data from western USA, while the prediction equation SEA99 is based on the strong ground motion data from exten-sional region all over the world. Comparing these two prediction equations in detail, it is found that after BJF94′s prediction value lg(Y) minus 0.16 logarithmic units, the value is very close to SEA99′s one. This case demonstrates that lg(Y) in extensional region is smaller; the differences of prediction equation are mainly owe to the differences of tectonic ambient shear stress value. If the factor of tectonic ambient shear stress value is included into the pre-diction equation, and the magnitude is used seismic moment magnitude to express, which is universal used around the world, and the distance is used the distance of fault project, which commonly used by many people, then re-gional differences of prediction equation will become much less, even vanish, and it can be constructed the uni-versal prediction equation proper to all over the world. The error in the earthquake-resistant design in China will be small if we directly use the results of response spectrum of USA (e.g. BJF94 or SEA99).

Sedimentary elements,evolutions and controlling factors of the Miocene channel system:a case study of the deep-water Taranaki Basin in New Zealand

Deep-water channel systems are important petroleum reservoirs,and many have been discovered worldwide.Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration and development.Based on high-resolution 3D seismic data,the Miocene channel system in the deep-water Taranaki Basin,New Zealand,was analyzed by using seismic interpretation techniques such as interlayer attribute extraction and strata slicing.The channel system was divided into five composite channels(CC-I to CC-V)according to four secondary level channel boundaries,and sedimentary elements such as channels,slump deposits,inner levees,mass transport deposits,and hemipelagic drape deposits were identified in the channel system.The morphological characteristics of several composite channels exhibited stark variances,and the overall morphology of the composite channels changed from relatively straight to highly sinuous to relatively straight.The evolution of the composite channels involved a gradual and repeated process of erosion and filling,and the composite channels could be divided into three evolutionary stages:initial erosion-filling,later erosion-filling(multistage),and channel abandonment.The middle Miocene channel system may have formed as a consequence of combined regional tectonic activity and global climatic change,and its intricate morphological alterations may have been influenced by the channel's ability to self-regulate and gravity flow properties.When studying the sedimentary evolution of a large-scale deep-water channel system in the Taranaki Basin during the Oligocene-Miocene,which transitioned from a passive margin to plate convergence,it can be understood how tectonic activity affected the channel and can also provide a theoretical reference for the evolution of the deepwater channels in areas with similar tectonic conversion environments around the world.

琼东南盆地陆源海相烃源岩有机质富集机理

琼东南盆地渐新统陆源海相烃源岩是深水区的一套重要烃源岩。从盆地构造格局、古气候、沉积相和三角洲规模4个方面对琼东南盆地渐新统陆源海相烃源岩的形成机理进行了分析。结果表明:盆地构造格局整体上控制了烃源岩的发育类型,断陷期的崖城组陆源有机质主要以近岸堆积形式形成煤系烃源岩;而陵水组(E_(3)l)陆源有机质则以河流-三角洲搬运形式形成陆源海相烃源岩。崖城组三段(崖三段,E_(3)y^(3))和三亚组二段(三二段,N_(1)s^(2))沉积期陆源高等植物最繁盛;崖二段(E_(3)y^(2))-崖一段(E_(3)y^(1))和陵水组二段(陵二段,E_(3)l^(2))-陵一段(E_(3)l^(1))沉积期次之,陆源高等植物供给充足。沉积相带控制陆源有机质的差异,同时卸载的不同形成了明显差异的陆源海相烃源岩。陆源海相烃源岩有利的发育区域为三角洲前缘-内浅海以及海底扇。大规模的三角洲可以输送更高生物通量的陆源有机质,提高了烃源岩有机质丰度,从而形成海域最为重要的一类有特色的气源岩。

准噶尔盆地南缘下侏罗统三工河组地球化学、沉积环境及源区特征分析

准噶尔盆地南缘是重要的油气勘探地区,也是研究盆地构造属性、沉积环境演化的重要区域。南缘下侏罗统三工河组由上部主体浅青灰色-灰绿色长石岩屑砂岩、粉砂质泥岩、泥质粉砂岩和下部土黄色长石岩屑砂岩、含砾粗砂岩、砾岩组成,对上部样品进行岩石学、岩相学和地球化学研究显示:样品化学蚀变指数(CIA)为77.57,反映物源区经历中等风化作用;碎屑物质磨圆和分选较差,表明沉积物搬运距离短,成分成熟度低;Cu/Zn、V/Cr、V/(V+Ni)、Ni/Co及U/Th值指示古沉积环境为富氧的氧化环境-贫氧过渡环境;Sr/Cu、Al_(2)O_(3)/MgO值指示温暖湿润的气候特征;Li,Sr,Sr/Ba,Th/U值指示淡水环境;综合岩相学特征认为,其上部主体为浅湖亚相沉积,下部为辫状河三角洲平原亚相沉积。样品中含流纹岩岩屑,La/Th-Hf、La/Sc-Co/Th和Ni-TiO_(2)判别图指示三工河组源岩主要来自于上地壳长英质火山岩;出现少量安山岩岩屑和Th/Co、Th/Cr比值显示源岩有少量中-基性岩。通过样品与不同构造背景杂砂岩成分对比、Th-Co-Zr/10、La-Th-Sc、Th-Sc-Zr/10判别图显示物源区应为大陆岛弧构造背景。

松辽盆地北部青山口组富烃页岩形成环境与成因

通过古地温、古地貌、沉积环境定量恢复及地质事件综合研究,分析青山口组富烃页岩形成环境及成因。结果表明,松辽盆地青山口组富烃页岩R_(o)介于0.75%~1.60%,游离烃含量高,介于(4~12)mg/g,形成于古地温梯度(50~70)℃/km的高温热盆背景;在拉伸大地动力学及热沉降背景下形成了正断层密集断裂带控制的页岩层系,两凹一凸的古地貌为页岩形成演化提供富集场所;湖相温湿气候及岩浆热液为藻类繁殖成为厚层富烃页岩发育奠定物质基础;缺氧的半深湖—深湖还原—强还原环境有利于有机质埋藏。综合分析表明,构造、湖相沉积与古地温耦合作用奠定了富烃页岩的构造背景和热动力条件,温湿气候、缺氧环境及火山热液带来的营养物质是富烃页岩形成的重要原因。

柴达木盆地七个泉背斜狮子沟组与七个泉组构造-沉积演化及对砂岩型铀矿成矿的启示

从构造-沉积演化角度分析矿体的形成和发育过程是砂岩型铀矿研究工作的重要内容。作者基于文献调研、野外地质调查和井震解释,对柴达木盆地七个泉背斜狮子沟组与七个泉组构造-沉积演化过程及其与砂岩型铀矿成矿的联系开展研究。研究认为:(1)狮子沟组富泥质砂,呈现退积旋回;七个泉组富砾,呈现进积旋回,底部与狮子沟组间发育新近系—第四系角度不整合,内部发育规模稍小的第四系内部角度不整合;狮子沟组—七个泉组发育由泥石流、下切沟道—充填和片流沉积构成的大型冲积扇,其中砂质层中密集发育地震变形构造。(2)新近纪以来最剧烈的构造抬剥事件发生在新近纪—第四纪之交,由此形成了新近系—第四系不整合并奠定了七个泉背斜构造格局。(3)推测七个泉背斜狮子沟组砂岩型铀矿潜在铀矿化段主要形成于新近纪—第四纪构造抬剥事件中,该事件催生出含矿构造,并加大了源区铀通量,最终控制了潜在铀矿化段形成发育和空间展布。新近系—第四系不整合则可作为预测潜在铀矿化段空间展布的关键构造控矿标志。同时,冲积扇扇中/扇缘中砂砾岩百分含量介于20%~50%之间的砂(砾)泥互层带可作为关键沉积控矿标志。研究成果可以为青藏高原东北缘盆地分析提供沉积学和地层学证据,对理解柴达木盆地其他背斜砂岩型铀矿形成发育过程具有重要价值。

新疆博格达山北缘二叠纪中—晚期构造运动的沉积响应

博格达山北缘是准噶尔盆地与天山造山带之间的关键部位,是研究盆山关系的重点区域。博格达山北缘二叠纪中、晚期的构造演化与沉积时空演变关系存在较大争议。本研究通过野外实地勘测、镜下岩石薄片鉴定、粒度分析实验和地震资料解析等方法,针对博格达山北缘东、西部两条剖面—大龙口剖面和井井子沟剖面开展研究,分析其沉积类型和演变过程,解析盆山构造变形和发育特征,探讨构造运动的沉积响应。研究结果表明:瓜德鲁普统乌拉泊组为湖成三角洲相,井井子沟组至红雁池组为湖泊相,乐平统泉子街组为冲积扇—河流相沉积,梧桐沟组和锅底坑组为滨浅湖—三角洲相沉积;研究区可分为两个主要构造层,下构造层以伸展断陷为主要结构,上构造层以前陆冲断为主要构造变形;多期构造活动控制瓜德鲁普统、乐平统沉积演化过程,在挤压构造背景下,瓜德鲁普统的湖泊相转变为乐平统冲积扇—河流相沉积,晚期构造活动趋于稳定,区域进入准平原化作用阶段。

渤海湾盆地辽中凹陷北部东营组沉积体系发育演化与构造古地貌的控制作用

根据地震和钻、测井资料,识别渤海湾盆地东北部辽中凹陷北部东营组中下段地震相和岩相组合类型,揭示沉积体系的发育演化规律;拉平古水平面,恢复东营组沉积时期构造古地貌,探讨构造古地貌对沉积体系发育演化的控制作用。结果表明:辽中凹陷北部东营组中下段可识别6种地震相与9种岩相组合类型,发育辫状河三角洲、曲流河三角洲、湖底扇以及碎屑湖泊等沉积,北部由辫状河三角洲演变为双向供源的曲流河三角洲-湖底扇,中南部早期发育小型辫状河三角洲并逐渐消亡,南部小型辫状河三角洲逐渐向北推进;东营组中下段沉积期研究区整体南高北低,可划分辽东凸起和辽中凹陷2个隆坳单元,进一步识别断裂陡坡带、缓坡断阶带、缓坡带、古沟谷等构造古地貌单元;研究区发育的沉积体系类型及规模与古坡折坡度、凹陷沉降中心位置、古沟谷规模密切相关,沉积体系的分布演化是盆地隆坳格局、坡折地貌形态、古沟谷发育位置与物源供给方向共同作用的结果。该结果对研究区油气勘探有利砂体预测具有指导意义。

粤东河源盆地的深部构造、沉积序列与盆地演化

粤东河源盆地是东南沿海规模较大的晚中生代—新生代陆相盆地之一,发育有较为完整的晚白垩世—新近纪地层。研究该盆地的深部构造、控盆断裂、沉积序列和盆地的形成发展,对于认识东南沿海晚中生代—新近纪的大地构造演化有重要意义。通过对野外地质调查、地球物理反射剖面和约两千米的地质科学钻探等数据资料的综合研究,查明了河源盆地为中生代—新生代沉积断陷盆地,地层结构清晰,沉积基底为早古生代地层,并建立了该盆地晚白垩世—新近纪的三阶段沉积序列;该盆地发育渐新世的火山岩,揭示了控盆边界断裂及内部构造发育特征,暗示了原型盆地的破坏发生于晚新生代:即盆地南北两侧紫金—博罗逆冲断层和河源断裂带在晚古近纪—新近纪强烈地改造了原型盆地;基于以上认识,初步恢复了河源盆地的形成演化历史,构建了河源盆地沉积序列-构造演化模式。

Formation,evolution,reconstruction of black shales and their influence on shale oil and gas resource

Black shales are important products of material cycling and energy exchange among the lithosphere,atmosphere,hydrosphere,and biosphere.They are widely distributed throughout geological history and provide essential energy and mineral resources for the development of human society.They also record the evolution process of the earth and improve the understanding of the earth.This review focuses on the diagenesis and formation mechanisms of black shales sedimentation,composition,evolution,and reconstruction,which have had a significant impact on the formation and enrichment of shale oil and gas.In terms of sedimentary environment,black shales can be classified into three types:Marine,terrestrial,and marine-terrestrial transitional facies.The formation processes include mechanisms such as eolian input,hypopycnal flow,gravity-driven and offshore bottom currents.From a geological perspective,the formation of black shales is often closely related to global or regional major geological events.The enrichment of organic matter is generally the result of the interaction and coupling of several factors such as primary productivity,water redox condition,and sedimentation rate.In terms of evolution,black shales have undergone diagenetic evolution of inorganic minerals,thermal evolution of organic matter and hydrocarbon generation,interactions between organic matter and inorganic minerals,and pore evolution.In terms of reconstruction,the effects of fold deformation,uplift and erosion,and fracturing have changed the stress state of black shale reservoirs,thereby having a significant impact on the pore structure.Fluid activity promotes the formation of veins,and have changed the material composition,stress structure,and reservoir properties of black shales.Regarding resource effects,the deposition of black shales is fundamental for shale oil and gas resources,the evolution of black shales promotes the shale oil and gas formation and storage,and the reconstruction of black shales would have caused the heterogeneous distribution of oil and gas in shales.Exploring the formation mechanisms and interactions of black shales at different scales is a key to in-depth research on shale formation and evolution,as well as the key to revealing the mechanism controlling shale oil and gas accumulation.The present records can reveal how these processes worked in geological history,and improve our understanding of the coupling mechanisms among regional geological events,black shales evolution,and shale oil and gas formation and enrichment.