Cenozoic Exhumation and Thrusting in the Northern Qilian Shan, Northeastern Margin of the Tibetan Plateau: Constraints from Sedimentological and Apatite Fission-Track Data

Abstract: The Qilian Shan lies along the northeastern edge of the Tibetan Plateau. To constrain its deformation history, we conducted integrated research on Mesozoic–Cenozoic stratigraphic sections in the Jiuxi Basin immediately north of the mountain range. Paleocurrent measurements, sandstone compositional data, and facies analysis of Cenozoic stratigraphic sections suggest that the Jiuxi Basin received sediments from the Altyn Tagh Range in the northwest, initially in the Oligocene (~33 Ma), depositing the Huoshaogou Formation in the northern part of the basin. Later, the source area of the Jiuxi Basin changed to the Qilian Shan in the south during Late Oligocene (~27 Ma), which led to the deposition of the Baiyanghe Formation. We suggest that uplift of the northern Qilian Shan induced by thrusting began no later than the Late Oligocene. Fission-track analysis of apatite from the Qilian Shan yields further information about the deformation history of the northern Qilain Shan and the Jiuxi Basin. It shows that a period of rapid cooling, interpreted as exhumation, initiated in the Oligocene. We suggest that this exhumation marked the initial uplift of the Qilian Shan resulting from the India–Asia collision.     

关于敦化盆地下白垩统的讨论

前人根据敦化盆地的地层的地层,认为该盆地下白垩统为河流—湖泊相碎屑岩。通过对新钻的敦参1井岩屑录井资料的分析、对16条二维地震资料的层位标定与追踪,以及对敦化盆地早白垩世盆地演化阶段的分析,得到了以下主要结论:1)敦化盆地下白垩统可能有两种分布形态,在盆地的主体部位,以浅变质岩形态存在,而在其他部位则以正常沉积岩形态零星存在;2)敦化盆地白垩系的分布规模不大,夹持于一个北北东向的狭窄长槽内;3)敦化盆地早白垩世处于裂谷盆地发展的初始张裂阶段;4)敦化盆地下白垩统不宜作为勘探目的层。     

Revision of the Clam Shrimp Genus Magumbonia from the Upper Jurassic of the Luanping Basin,Hebei,Northern China

The diverse clam shrimp Nestoria-Keratestheria fauna is widely distributed in the Dabeigou Formation in northern Hebei and eastern Inner Mongolia of China.Its important component genus Magumbonia from the Dabeigou Formation in the Luanping Basin,northern Hebei,China,is revised on the basis of a scanning electron microscope (SEM) examination of the type species M.jingshangensis Wang,1984,which revealed morphological features not recognized previously.These include coarse reticulation on the umbo and promi...     

江汉盆地潜江凹陷潭口地区潜江组盐构造类型及成因机制探讨

潜江凹陷位于江汉盆地的中部,潭口油田靠近潜北大断层.通过勘探开发,根据测、钻井资料及生产动态数据发现,该区地层厚度在短距离内发生较大变化,砂体间的侧向连续性差,范围小.该地区盐岩十分发育,根据地震剖面以及盐层的发育,分析该地区产生一系列盐构造的类型,分别有盐层滑脱带以及滑脱断层、盐隆构造、盐辟构造等几种类型.该地区的盐构造的成因机制主要为走滑作用,根据盐构造的类型,成因机制可分为盐层滑脱作用、盐层隆升作用以及盐层刺穿作用.将盐构造的演化分为3个阶段,分别为荆沙组盐构造孕育期、潜江组潜四-潜三段盐构造生成期、潜江组潜二段-荆河镇组盐构造定型期.盐岩的发育以及盐构造的形成,在一定程度上导致目的层砂体侧向连续性差,油层展布范围小,对油气成藏产生影响.     

Characteristics of boundary fault systems and its hydrocarbon controlling on hydrocarbon accumulation in Awati Sag,Tarim Basin,China

Based on the interpretation of two-dimensional seismic data, this paper analyzes the characteristics of three boundary fault systems including the Shajingzi fault, the Aqia fault and the Tumuxiuke fault around the Awati sag of the Tarim Basin, and studies its controlling on hydrocarbon accumulation. Neotectonic movement is ubiquitous in oil and gas bearing basins in China, such as Neogene intense activities of large boundary thrusting faults of the Awati sag: Shajingzi fault, Aqia fault and Tumuxiuke fault. Based on a large number of seismic data, it is showed that they have section wise characteristics in the direction of fault strike, and active periods and associated structures formed of different sections are different. Usually, large anticlinal structures are formed in the upper wall, and faulted anticline controlled by companion faults are formed in the bottom wall. Large faults cut the strata from Cambrian up to Neogene. For the anticline in the upper wall, fault activities caused by neotectonic movement played a destructive role in hydrocarbon accumulation, thus the preservation condition is critical for reservoir formation. In this sense, attention should be paid to formations in the upper walls of Aqia fault and Tumuxiuke fault under the Cambrian salt bed, whose plastic deformation could help to heal faults. Companion faults in the bottom wall cut down to the Cambrian and up to the Triassic serving as the pathway for hydrocarbon migration, and associated structures in the bottom wall are noteworthy exploration targets.©2019 China Geology Editorial Office.     

Evolution of the depositional environments of the Jurassic Walloon Coal Measures,Surat Basin,Queensland, Australia

The Jurassic Walloon Coal Measures of the Surat Basin in eastern Australia host the continent's most significant coal bed methane resources. Previous studies have interpreted the Walloon Coal Measures within a single depositional facies model encompassing a wholly terrestrial setting. Using a multidisciplinary approach (facies analysis, palynology and wireline logs), the evolution of the Walloon Coal Measures is described within a new chronostratigraphic framework defined by accurate and precise U–Pb tuff dates. Analysis of sedimentary facies indicates that the majority of the Walloon Coal Measures was deposited by relatively small (<300 m wide), low gradient rivers on a poorly‐drained floodplain with numerous small lakes and mires. However, this study also identified some marine‐influenced facies with brackish palynomorphs (notably dinoflagellate cysts) and tidal sedimentary structures. These facies appear to have been deposited in estuaries during times of transgression. The evidence for base level shifts suggests that the coals may not have coevally accumulated with at least some of the thicker sandstones. Palaeogeographic maps for eleven time intervals suggest that rivers drained towards to the south/south‐west and south‐east, as indicated by sandstone percentage and gross unit isopach maps, presumably into proximal estuarine complexes. Marine incursions into the continent probably came from the north and east during times of high eustatic sea level and as precursors to those of the more persistent and extensive transgressions of the Early Cretaceous. A similar multidisciplinary approach should help to elucidate the evolution of other fluviolacustrine systems in other basins and aid in resource prediction.     

中国海相克拉通盆地内部走滑断裂发育特征及控藏作用

走滑断控油气藏作为一种全新类型油气藏,其勘探潜力已初步显现。在对中国三大海相克拉通盆地内部走滑断裂发育特征与控藏作用开展对比分析的基础上,揭示了塔里木盆地、四川盆地、鄂尔多斯盆地内部走滑断裂空间结构与活动特征的相似性与差异性,并结合盆地动力学演化特征探讨了不同盆地内部走滑断裂成因机制,系统分析了三大盆地内部走滑断裂的控藏作用:(1)中国三大海相克拉通盆地内部均发育中小尺度滑移距走滑断裂,普遍具有“纵向分层,平面分段,垂向多期叠加”的空间结构特征。(2)三大克拉通盆地内部走滑断裂体系具有成因、分布和期次的差异性。塔里木盆地内部走滑断裂体系形成时间早,演化时间长,在盆地北部具有“南北对接,东西分区”特征;鄂尔多斯盆地西南缘受燕山期(侏罗纪—白垩纪)陆内挤压影响,形成了北西西向走滑断裂体系;四川盆地受控于二叠纪峨眉山大地幔柱影响,在盆地内部先存基底断裂基础上,形成了北西向、北西西向、近东西向张扭型走滑断裂。(3)中国三大海相克拉通盆地内部走滑断裂对油气成藏和富集具有重要的控制作用。在控储方面,受断裂-流体耦合改造控制,可形成断控缝洞型储集体、断-溶缝洞型或断控裂缝-孔隙型储集体;在控圈方面,在碳酸盐岩地层中可形成断控缝洞型、断溶缝洞型岩性圈闭;在控运方面,走滑断裂产状高陡,可直接沟通烃源岩和储层,构成重要的油气垂向输导体系。     

尼日尔Termit盆地古近系构造样式及其对油气聚集的控制作用

尼日尔Termit盆地主要发育早白垩世和始新世-渐新世两个裂陷旋回,其起源于不同的动力学背景和运动学机制,相应表现出不同的盆地性质。其中古近纪始新世-渐新世第二裂陷旋回受区域挤压应力环境下的非洲板块内部局部应力释放控制,具有逃逸盆地的性质,在盆地内部表现为典型走滑伸展特征。该旋回在第一期NW-SE控盆断裂基础上发育了NNW-SSE断裂体系,盆地整体呈现地堑地垒和半地堑结构,北部为双断结构地堑,南部为西断东超多米诺半地堑结构。古近系断裂的斜向拉张作用形成了大量雁列式正断层,以软连接方式相连,在二级构造单元内发育了大量构造调节带,分为同向型、对向型和背向型3大类,以同向叠覆型、对向平行型和背向叠覆型为主,成为Termit盆地最主要的构造调节带样式。古近纪始新世-渐新世第二裂陷旋回及其构造样式控制了盆地沉积体系,在始新世Sokor1初始裂陷期形成了三角洲湖泊沉积体系、渐新世-早中新世Sokor2深陷期沉积了湖相泥岩,形成了盆地主力储盖组合。同时,该旋回的构造调节作用形成了大量断块和断鼻/断背斜构造,成为Termit盆地的主要圈闭类型。渐新世-早中新世的深陷期导致断层沟通白垩系成熟烃源岩,在盆地内发生广泛的垂向和侧向运移,该时期断层的活动强度决定了古近系油气分布和富集程度。Sokor1和Sokor2段中下部岩性圈闭及Sokor2段成藏组合是Termit盆地的下步勘探领域。     

高密度电法在草炭土分布特征调查中的应用

为了更好的研究草炭土湿地基本信息,获取草炭土分布特征,选择吉林省东部沼泽草炭土湿地为研究对象,运用高密度电阻率法,对比不同装置下探测结果的差异,再与已知的探槽资料做对比,得出温纳—施伦贝格装置为最可靠、最合理的探测装置。再将该装置运用到其他草炭土地区,得出对草炭土湿地的探测为浅层地质问题,草炭土的视电阻率为50~300Ω·m,深度为1.2~3.9 m,在反演图像中表现为低阻体部分,各地层间层状结构明显,电性界限分明。     

Salt-influenced normal fault growth and forced folding: The Stavanger Fault System,North Sea

Displacement ratio (D_r) is the ratio between salt thickness (T_v) and sub-salt normal fault displacement (D) (D_r = T_v/D), and it is typically used to predict the degree of geometric and kinematic linkage between sub- and supra-salt fault populations, and the overall structural style in salt-influenced extensional settings. However, we currently lack natural examples of how D_r and the underlying geological controls vary, and how these may control the three-dimensional geometry and evolution of salt-influenced normal fault systems. Furthermore, it is currently unknown if kinematic coherence in salt-influenced extensional settings can be maintained over relatively long length-scales (10¹–10³ m) and for relatively long timeframes, and how this may impact the growth and geometry of large-throw (>500 m), salt-influenced normal fault systems. In this paper we use a 3600 km², high-quality 3D seismic reflection dataset and borehole data from the Stavanger Fault System (SFS), Egersund Basin, eastern North Sea Basin to investigate; (i) how pre-rift salt thickness (T_v) and sub-salt fault throw (T) control the structural style and evolution of a basin-bounding, salt-influenced normal fault system; and (ii) the role salt plays in maintaining kinematic coherence in normal fault systems. We demonstrate that; (i) pre-rift salt distribution (T_v), specifically its presence in the proto-footwall (i.e., when T_v > 0), is the primary control on partitioning of faulting and (forced) folding along the fault system, and the style of linkage (i.e., hard- or soft-linkage) between sub- and supra-salt fault populations; and (ii) sub- and supra-salt fault populations represent brittle elements of a single, geometrically and kinematically coherent structure, the geometry and evolution of which is related to the ductile translation of strain on a scale (up to 8 km) and duration (c. 65 Myr) that believe is significantly greater and longer than previously documented.