川滇南北向构造带早中生代构造变形研究

贺兰-川滇南北向构造带是划分中国大陆东西的地幔陡变带,其南段川滇南北向构造带是由几个性质不同的构造系统叠加组成的复杂构造带.研究发现,位于扬子地块西缘的川滇南北向构造带发育由雁行状左行走滑断裂为骨架的走滑构造带.走滑构造带经历了两期构造叠加,早期变形为北东-南西挤压应力场形成的一系列北西-南东走向的逆冲断裂,晚期北西-南东挤压应力场环境下沿先前的逆冲断层形成一系列左行走滑断裂.在这些左行走滑断裂之间,发育一些中生代盆地,盆地沉积相和古流向研究显示,这些盆地的形成受走滑断裂控制.因此,依据盆地内最老地层限定,扬子西缘走滑构造带形成于早中生代.作者认为,这个走滑构造带的形成,很可能与晚三叠世-侏罗纪时期扬子地块顺时针旋转并持续向北俯冲-碰撞有关,川滇南北向构造带在早中生代中国大陆的主体碰撞拼贴过程中就已经开始形成.     

营潍断裂带走滑构造特征、演化及动力学机制

营潍断裂带位于渤海湾,是郯庐大断裂的北延段.由于受早期NW向断裂分割构造块的影响,营潍断裂带可分为走向和构造特征有显著差异的北、中、南三段,其走滑构造特征表现的非常明显,形成了一些特征性的伴生构造.断裂带的深部结构呈现出典型的平移断层性质,已切穿莫霍面乃至岩石圈,成为地幔热物质上涌或基性物质上涌的通道.通过综合分析区域板块构造演化、沉积盆地发育和岩浆活动特征,将营潍断裂发育演化历史归结为晚侏罗世-早白垩世(J3-K1)左行平移期、晚白垩世-始新世(K2-E2)伸展拉张期和渐新世以来(E3-Q)右行平移期三个阶段,并就其动力学机制进行了初步的讨论.     

准噶尔盆地东缘构造:阿尔泰与北天山造山带交接转换的陆内过程

准噶尔盆地位于中亚造山带西段,地表地质已有大量成果,但对该盆地深部结构构造研究相对薄弱,这制约了对该区构造演化的认识.通过对研究区大量二维地震剖面的详细构造解释,揭示出准噶尔盆地东缘主要的逆冲断裂有:乌伦古东、红盆、红盆南、喀拉萨依、滴水泉北、滴水泉南和沙西等断裂.断裂整体组合表现为向北西发散、向南东收敛的逆冲-走滑构造特征,可分为三组构造体系.北部叠瓦式褶皱-逆冲体系位于研究区北部,走向北西,倾向北东,表现为自北向南的叠瓦式逆冲推覆构造,整体上具有北老南新的特征,断裂最早形成于石炭纪,之后向南不断拓展.中部逆冲-走滑体系位于研究区中部,近东西走向,断面陡立,印支期为左行压扭,燕山期发生右行走滑,伴生少量小型正断层.南部褶皱-逆冲体系位于研究区南部,北东走向,倾向北西,分支断裂主体均为走向北东的逆断层.全区断层相关褶皱常见有断展和断弯褶皱.区域构造对比表明,在南阿尔泰和北天山两大造山带的挤压汇聚作用下,准噶尔盆地东缘在三叠纪-早白垩世期间持续发生陆内变形.其中研究区北部主控断裂指示了自北向南的逆冲推覆,动力来自南阿尔泰造山带的持续挤压;南部褶皱不对称性和主逆冲断层指示动力来自北天山造山带的持续挤压;中部走滑断裂早期逆冲作用较强,后期叠加走滑构造,是南、北两大动力系统发生复杂交接转换的结果,并调节了盆地内部次级块体的运动,使其向西挤出.     

渤海海域主要新构造活动断裂带

渤海位于渤海湾盆地的东部,是我国华北地区新构造活动最强烈的地区之一,盆地内的沉积盖层(N-Q)中断裂极为发育。许多研究者从不同角度对渤海新构造进行过研究,但认识不一。笔者基于以往的工作,对该区新构造作了较深入的分析,确定渤海新构造运动起始于中新世晚期(12~10Ma BP)。从三维空间分析盖层断裂,并按其与盆地基底断裂的成因关系,将新构造活动的断裂分为继续活动断裂和新生断裂,并划分出3条主要的新构造活动断裂带:北东(偏北)向营口-潍坊断裂带北段是继续活动构造带,右旋逆平移活动,活动性弱;北西西向北京-蓬莱断裂带亦为继续活动构造带,左旋正平移活动,活动性较强;北东向庙西北-黄河口断裂带为新生构造带,右旋平移活动,活动性强。后两者组成一对以庙西北-黄河口断裂带为主的偏共轭活动构造带,该区域地震活动与之关系密切。最后探讨了渤海地区新构造期北东东-南西西至近东西向水平挤压的构造应力场及其与新构造活动断裂带发育的关系。提出新构造应力场与古近纪盆地裂陷阶段的应力场截然不同,新构造为地壳共轭剪切破裂系统,古近纪盆地构造是发育于地壳上部的伸展构造系统,这是两期不同体制的构造系统。     

辽东半岛晚侏罗-早白垩世挤压-伸展构造转折及金成矿意义

由于缺少沉积、岩浆和变质作用记录,挤压构造向伸展构造的转折过程是研究的盲点和难点.东部华北克拉通东缘的辽东半岛,在经历早中侏罗世褶皱-逆冲挤压构造作用后,至早白垩世转变为区域性的伸展构造.其间晚侏罗世-早白垩世早期至少有约13Myr构造活动性较弱,理解程度较低,是区域构造演化与构造动力学分析的盲点.本文选取辽东半岛北部通远堡-爱阳地区进行了详细的构造调查与解析,识别出一系列小规模SN向逆冲-左行走滑为主、NW向右行逆冲-走滑为辅的断层和相关褶皱.根据断层及其擦痕线理与构造运动学关系分析,恢复的构造应力场以走滑机制为主,最大主压应力场为NW-SE向.区域上这些近SN向逆冲-走滑断层组合表现为右列排列,控制了断层桥区的局部挤压抬升和剥蚀,切割分解并在相邻岩桥之间保存了早中侏罗世大型火山-沉积的残留盆地,在随后的演化中,在通远堡、方家隈子等上覆形成早白垩世小型火山-沉积盆地.通过对盆地性质和形成时间的分析,结合区域岩浆作用年代综合分析,辽东半岛的构造转折开始于156～153Ma,结束于约140～139Ma.我们提出上述逆冲-走滑断层组合是晚侏罗世-早白垩世早期郯庐断裂带持续左行走滑和沿渤海湾地区向北扩展过程中形成的R-R′破裂组合,是古太平洋板块俯冲方向由向NW转向NNW的过程中,构造应力场逐渐减弱导致,从而提出了挤压构造向伸展构造转折的构造模式,并认为这个过程可能为金元素活化和含金流体开始迁移提供有利条件,从而开启了新一次金成矿富集过程.     

渤海盆地现代构造应力场与强震活动

渤海位于北华北新生代裂陷盆地的东部，是一个晚第四纪形成的内陆海盆. 渤海盆地活动断裂发育，地震活动强烈，交会于渤海中部的NE向营口——潍坊断裂带北段、庙西北——黄河口——临邑断裂带及NW向北京——蓬莱断裂带是主要的活动构造带，将海区分成4个次级新构造区，成为现代应力场作用的构造基础. 综合研究38个震源机制解和75个井区应力场等资料，以及构造应力场二维数值模拟计算结果表明，渤海及其邻区现代构造应力场的压应力方向为NE60～90，张应力为SN——NW30；以水平和近水平应力作用为主；不同构造区主应力方向存在一定的差异. 现今渤海地区地壳发育以NNE——NE和NW——WNW走向的共轭剪切破裂为特征，是控制地震活动的主要构造.      

应用震源机制解分析依兰-伊通地堑北段现代构造应力场

应用震源机制解分析了依兰-伊通地堑断裂北段的汤原-萝北段的构造活动和现代构造应力场,结果表明:区域构造活动受地堑构造控制,NW向断裂是区内主要的发震构造,震源机制主压应力轴优势分布方向为NE50°~70°,仰角40°~60°。     

张强凹陷及邻区的构造应力分析

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     

太行山南缘断裂带新构造活动及其区域运动学意义

基于TM遥感影像的构造地貌解译和野外活动断层滑动矢量的测量和分析 ,阐述了太行山南缘断裂带第四纪左旋走滑活动的构造和地貌标志 ,反演了断裂变形的构造应力场 ,探讨了太行山南缘断裂带左旋走滑活动的区域运动学意义。研究表明 ,第四纪时期太行山南缘断裂带是一条斜张左旋走滑断裂。断层滑动矢量观测显示新近纪以来有 2期引张应力作用 :早期为NE -SW向引张 ,晚期为NNW -SSE向引张 ,这个观测结果与渭河地堑盆地的新近纪—第四纪 2期引张构造应力场一致。根据华北盆地构造资料推断 ,太行山南缘断裂带向东延伸与盆地内的泌阳 -开封 -商丘断陷带相接 ,共同构成了南华北和北华北 2个断陷区的构造边界。指出该断裂带作为南华北块体北缘 ,其新构造时期的斜张左旋走滑活动与南部秦岭断裂系左旋走滑活动一致 ,它们组成了一个宽阔的、向东撒开的、弥散型分布的左旋走滑形变带 ,调节着华南地块相对于华北地块向SEE方向的构造挤出     

中国地震科学台阵两期观测资料近场记录揭示的南北地震带地壳剪切波分裂特征

利用中国地震科学台阵第一期(2011-01-2014-06)及部分中国地震科学台阵第二期(2013-02-2015-12)的流动地震台阵记录到的小震波形资料,运用剪切波分裂系统分析(SAM)方法,分析南北地震带的地壳各向异性,对剪切波分裂参数所反映的区域应力环境及构造特征,以及区域内主压应力方向与断裂分布的关系展开讨论.研究结果表明,南北地震带快剪切波偏振方向自北向南由NE向逐渐转变为NNW向,与南北地震带区域主压应力的方向变化具有一致性.区域内分布的大量NE及WNW或NW向断裂构造同样对快波偏振方向有比较大的影响,位于走滑断裂附近的台站,其快波方向与断裂走向大致平行,部分位于走滑断裂附近的台站其快波方向几乎垂直于断裂走向,而与构造应力场方向一致性较好.个别台站表现出复杂快波优势方向特征,反映出研究区内构造环境的复杂性.慢波时间延迟结果显示,南北地震带南段的平均时间延迟高于北段,反映了受印度板块和欧亚板块的碰撞挤压作用,南段地壳介质各向异性程度更大,构造变形更加剧烈.对比南北地震带上地幔各向异性特征,推测在川滇菱形块体内部可能存在复杂的壳幔耦合现象,地壳剪切波分裂除了反映区域应力特征,还可以揭示出区域构造信息.     

Cenozoic structural deformation and expression of the “Tan-Lu Fault Zone” in the West Sag of Liaohe Depression, Bohaiwan basin province, China

Based on the interpretation of 3D seismic data and structural mapping we analyzed the geometry and kinematics of the fault system and validated the expression of the “Tan-Lu Fracture Zone” in the West Sag of Liaohe Depression, Bohaiwan basin province. The Cenozoic structural deformation within the West Sag of Liaohe Depression can be divided into extensional structure system and dextral structure system. The extensional system is constituted by numerous NNE-NE trending Paleogene normal faults, where the Taian-Dawa fault (F1) is the master boundary fault (MBF) dominating the deposition during Paleogene so that the sag shows a complex half-graben with “boundary fault in the east and overlap in the west”. The dextral system is constituted by 2–3 dextral basement faults in NNE-NE trending (F2, F3, F4) and associated structure, and the time of structural action started in Oligocene and continued to Quarternary so that some associated secondary faults of the dextral system cut off the Neogene and Quaternary. Under the influence of the position and attitude of NNE-NE trending basement strike-slip faults, the central north part and the south part of the West Sag show obviously different structural features. The former appears to be a complex “graben” structure limited by the reversed strike-slip fault in the west and bounded by the inverted normal fault in the east, the latter remains the complex half-graben structure with “boundary fault in the east and overlap in the west”, and the graben was mildly reconstructed by one or two normal strike-slip faults. The dextral system within the West Sag is the element of the west branch fault of the Tan-Lu Fracture Zone, which is a deep fracture zone extending along the east of the Liaodongwan Gulf. The deep fracture zone branches off into two separate faults within the Liaohe Depression. The east branch goes through from northern part of the Liaodongwan Gulf to the East Sag of Liaohe Depression and links with the Denghua-Mishan Fault near Shenyang, and the west branch passes from northern part of the Liaodongwan Gulf to the West Sag and Damintun Sag of Liaohe Depression and links with the Yilan-Yitong Fault. The principal displacement zone of the west branch of the Tan-Lu Fracture Zone cuts off the master extensional fault (F1) within the West Sag of Liaohe Depression and induces many cover faults in EW trending within the Neogene and Quaternary.     

喜马拉雅东构造结周边地区主要断裂现今运动特征与数值模拟研究

本研究通过对东构造结及其周边地区主要断裂进行野外考察,通过GPS观测数据和地质、地球物理资料的综合分析,建立三维有限元模型;运用数值模拟方法对东构造结周边地区主要断裂现今运动特征进行模拟研究,取得一些初步的认识:(1)东构造结北侧和东侧地块总体上围绕构造结发生顺时针旋转,右旋走滑的东南边界断裂不是嘉黎断裂,可能是阿帕龙...     

TECTONIC CHARACTERISTICS OF BAOTOU UPLIFT IN HETAO DEPRESSION ZONE

The Hetao depression zone, located to the north of Ordos block, is a complex depression basin that consists of two sub-uplifts and three sub-depressions. The depression zone is subject to the regional extensional stress field driven by the Indo-Asian continental collision and the westward subduction of the Pacific Plate. The Baotou uplift that separates the Baiyanhua sub-depression and Huhe sub-depression is mainly composed of Archean gneiss and is overlaid by Quaternary sedimentary strata. The two sub-depressions are bordered by the Wula Mountains and Daqing Mountains to the north, respectively. The bedrock exhumed in Wula Mountains and Daqing Mountains consists mostly of Precambrian granitic gneiss, and the piedmont depressions are infilled by thick Cenozoic strata. The Wulashan piedmont fault and Daqingshan piedmont fault extend along the range front of Wula Mountains and Daqing Mountains, respectively. The subsidence is controlled by the two boundary faults. Previous studies have preliminarily documented the characteristics of the northwest boundary fault of Baotou uplift. Combining shallow seismic exploration, active fault mapping, and geological drilling, this paper presents a detailed study on the tectonic characteristics of the Baotou uplift. The shallow seismic exploration reveals that the Baotou uplift is an asymmetrical wedge with a steep southeast wing and a gentle dipping northwest wing. The Baotou uplift is wider in the northeastern part and narrows down towards the southwest. In seismic profiles, the Baiyanhua sub-depression and the Huhe sub-depression manifest as asymmetric dustpan-like depressions with south-dipping controlling faults. Baotou uplift is bounded by the Xishawan-Xingsheng Fault to the northwest and Daqingshan piedmont fault to the southeast. The two faults exhibit significant difference in many aspects, such as fault geometry, fault displacement, the latest active time, and so on. The southeast boundary fault of Baotou uplift is the Baotou section of the Daqingshan piedmont fault which is a Holocene active fault and the major boundary fault of Huhe sub-depression. East of Wanshuiquan, the fault strikes EW-NEE; west of Wanshuiquan, the strike changes to NW. The Daqingshan piedmont fault appears as a south-dipping listric fault in seismic profiles whose dip decreases with depth and cuts through all the sedimentary strata in Huhe sub-depression; the fault extends along the late Pleistocene lacustrine platform at surface with prominent geomorphological evidences. The Xishawan-Xingsheng Fault is a buried high-angle normal fault that mainly dips to the northwest and strikes NE. The fault strike changes to NNE at the eastern tip. Based on the results of seismic exploration and geological drilling, the Xishawan-Xingsheng buried fault is an early to middle Pleistocene Fault capped by late Pleistocene lacustrine strata. We reckon that the Xishawan-Xingsheng Fault is one of the synthetic faults that dip towards the main boundary fault of Baiyanhua sub-depression. Similarities in lithology, geometry, and structural characteristics of south boundary faults all indicate that Baotou uplift is the western extension of Daqing Mountains. Multiple factors may contribute to the formation of Baotou uplift, such as tectonic subsidence and the development of large-scale river system and mega-lake. We suggest that the upwelling of asthenosphere may play a primary role in the evolution of Wulanshan piedmont fault and Daqingshan piedmont fault. Separated by the Baotou uplift, the Wulashan piedmont fault and Daqingshan piedmont fault can be regarded as independent seismogenic faults. The Hetao depression zone is featured by complex inner structures, and many scientific issues are subject to further researches. Thus, more attention should be paid to the secondary structures within the depression zone for a better understanding on the formation and evolution of Hetao depression zone.     

SLIP RATES OF THE RIYUE MT. FAULT AT DEZHOU SEGMENT SINCE LATE PLEISTOCENE

The Riyue Mt. Fault is a secondary fault controlled by the major regional boundary faults (East Kunlun Fault and Qilian-Haiyuan Fault). It lies in the interior of Qaidam-Qilianshan block and between the major regional boundary faults. The Riyue Mt. fault zone locates in the special tectonic setting which can provide some evidences for recent activity of outward extension of NE Tibetan plateau, so it is of significance to determine the activity of Riyue Mt. Fault since late Pleistocene to Holocene. In this paper, we have obtained some findings along the Dezhou segment of Riyue Mt. Fault by interpreting the piedmont alluvial fans, measuring fault scarps, and excavating trenches across the fault scarp. The findings are as follows:(1) Since the late Pleistocene, there are an alluvial fan f_p and three river terraces T₁-T₃ formed on the Dezhou segment. The abandonment age of f_p is approximately (21.2±0.6) ka, and that of the river terrace T₂ is (12.4±0.11) ka. (2) Since the late Pleistocene, the dextral strike-slip rate of the Riyue Mt. Fault is (2.41±0.25) mm/a. In the Holocene, the dextral strike-slip rate of the fault is (2.18±0.40) mm/a, and its vertical displacement rate is (0.24±0.16) mm/a. This result indicates that the dextral strike-slip rate of the Riyue Mt. Fault has not changed since the late Pleistocene. It is believed that, as one of the dextral strikeslip faults, sandwiched between the the regional big left-lateral strike-slip faults, the Riyue Mt. Fault didn't cut the boundary zone of the large block. What's more, the dextral strike-slip faults play an important role in the coordination of deformation between the sub-blocks during the long term growth and expansion of the northeast Tibetan plateau.     

滇西南地区黑河断裂中西段晚第四纪构造活动特征

通过卫星影像解译、野外实地调查与地质填图,对滇西南地区黑河断裂中西段晚第四纪构造活动特征进行了研究.结果表明,黑河断裂为一条规模较大的区域性活动断裂带,西起沧源县南,向东南止于澜沧江断裂,全长约168 km,走向280°～310°.该断裂晚第四纪新活动性具有一定的差异性和分段性.根据其几何结构、最新活动性及1988年澜沧7.6级地震破裂带特征,可将黑河断裂从西向东划分为沧源-木戛、木戛-南代和南代-勐往三条次级断裂段.其中的中、西段长约88 km,全新世活动显著,活动性质以右旋走滑为主.沿断裂形成了丰富的断错地貌现象.西段断裂的最新活动断错了全新世晚期地层;中段是1988年澜沧7.6级地震的发震断裂之一.根据对断错冲沟的测量和年代测试,得到其全新世以来右旋滑动速率为(3.54±0.78)mm/a,与区域上其它断裂的滑动速率大致相当,反映了其区域构造活动的整体性和协调性.     

Northwest trending tectonic belt in the middle Yanshan Orogenic Belt of northeast Hebei Province,North China: Tectonic evolution and geochronology

1 An out-of-line northwest trending tectonic beltin the middle part of the Yanshan Orogenic Belt The tectonic framework of the intraplate YanshanOrogenic Belt is dominated by east-west and northeastextending structures as revealed by many geologists.There lies, however, a 100-km-long enigmatic out-of-line northwest extending tectonic complex in the mid-dle part of the Yanshan Orogenic Belt (fig. 1). Theresearch on the geometry, kinematics, timing of thiscomplex tectonic belt and its r…     

Geometry and Late Quaternary Kinematic Characteristics of the Huoshan Fault in Shanxi Province

The Huoshan fault is an important fault controlling the boundary of the Linfen basin at the middle transtensional segment of the Shanxi graben system.In this paper a discussion is made emphatically on the tectonic segmentation of the Huoshan fault,its internal geometric structures and characteristics of its activities since the late Quaternary on the basis of 1:10,000 scale geological mapping.Our investigations indicate that the Huoshan fault can be divided into 3 segments with different behaviors and structures.Among these 3,the shear segment with dextral movement is composed of a number of second-order shear faults in right-lateral stepover or left-lateral stepover arrangement.It has a maximum dextral displacement up to 9.83 km since the Pliocene,a dextral slip rate of 2.0 mm/a; a maximum vertical differential displacement of 3.44 km,and a differential oscillatory movement rate of 0.69 mm/a.The lower limit of dextral Holocene slip rate is about 5 mm/a.     

GEOLOGICAL AND GEOMORPHIC EVIDENCE FOR DEXTRAL STRIKE SLIP OF THE HELAN SHAN WEST-PIEDMONT FAULT AND ITS TECTONIC IMPLICATIONS

The horizontal movement of the Helan Shan west-piedmont fault is important to determination of the present-day boundary between the Alashan and North China blocks as well as to the exploration of the extent of the northeastward expansion of the Tibetan plateau. Field geological surveys found that this fault cuts the west wing of the Neogene anticline, which right-laterally offset the geological boundary between Ganhegou and Qingshuiying Formations with displacement over 800m. The secondary tensional joints (fissures)intersected with the main faults developed on the Quaternary flood high platform near the fault, of which the acute angles indicate its dextral strike slip. The normal faults developed at the southern end of the Helan Shan west-piedmont fault show that the west wall of this fault moves northward, and the tensional adjustment zone formed at the end of the strike slip fault, which reflects that the horizontal movement of the main fault is dextral strike slip. The dextral dislocation occurred in the gully across the fault during different periods. Therefore, the Helan Shan west-piedmont fault is a dextral strike slip fault rather than a sinistral strike slip fault as previous work suggested. The relationship between the faulting and deformation of Cenozoic strata demonstrates that there were two stages of tectonic deformation near the Helan Shan west-piedmont fault since the late Cenozoic, namely early folding and late faulting. These two tectonic deformations are the result of the northeastward thrust on the Alashan block by the Tibet Plateau. The influence range of Tibetan plateau expansion has arrived in the Helan Shan west-piedmont area in the late Pliocene leading to the dextral strike slip of this fault as well as formation of the current boundary between the Alashan and North China blocks, which is also the youngest front of the Tibetan plateau.     

Kinematics of the Rockland Brook Fault, Nova Scotia: Implications for the interaction of the Meguma and Avalon terranes

The Cobequid-Chedabucto fault system of northern mainland Nova Scotia represents the surface expression of the Avalon-Meguma terrane boundary, but because it is exposed at high crustal levels in the Cobequid Highlands, the fault system provides little information as to the kinematic relationships of the two terranes in this area. In the eastern Cobequid Highlands, the Rockland Brook Fault (RBF) is exposed within the more deeply eroded highlands massif and juxtaposes units of widely varying ages and lithologies. Therefore, this fault is better suited to define the nature and timing of fault movement associated with Avalon-Meguma terrane interaction.In several large Carboniferous plutons along the length of the RBF, and in previously deformed Precambrian rocks, mylonitic foliation orientations are predominantly east-west trending and mineral lineations plunge southeast. Kinematic indicators such as minor fold vergence, porphyroclast systems, asymmetric boudins, shear-band fabrics, and preferred recrystallization orientations indicate dextral shear. These data are taken to infer that the central section of the RBF is dominated by dextral strike-slip motion. Transpression occurs locally where the RBF curves into restraining bends. Kinematic data in these bends indicate top to the northwest thrusting. At the easternmost extent of the RBF, high-level brittle normal faults predominate in the locally extensional environment. The timing of RBF movement is constrained only by the ca 360 Ma granite bodies which it deforms and by the Westphalian sedimentary rocks which are affected by only the latest stages of movement.These kinematic data are consistent with previously published kinematic models for the interaction of the southern margin of the Avalon Composite Terrane with the Meguma Terrane in mainland Nova Scotia. These models suggest that regional dextral shear was accompanied by localized components of transpressional thrusting, wrench tectonism, and small-scale sedimentary basin development during Devonian to Carboniferous terrane interaction.     

research on characteristics of late quaternary activity of the jiangsu segment of anqiu-juxian fault in the tanlu fault zone

Anqiu-Juxian Fault is an important fault in the Tanlu fault zone, with the highest seismic risk, the most recent activity date, and the most obvious surface traces. Due to lack of credible geological evidences, there is big controversy on the Holocene activity in the Jiangsu segment of this fault. Research on the characteristics of late Quaternary activity in the Jiangsu segment of Anqiu-Juxian Fault, particularly its latest activity time, is of great significance to assessment of its earthquake ability and seismic risk. Based on field investigations on the Jiangsu segment of Anqiu-Juxian Fault, and combining with the results of fault activities identification on this fault in Suqian City, we discussed the characteristics of its activities in late Quaternary. Multiple geological sections we found in this study and the results of fault activities identification in Suqian City all indicate that there was an ancient seismic event occurring in middle period of Holocene in the segment from southern Maling Mountain to Suqian City; but the trench at Houchen village did not show any evidence of Holocene activity on the Chonggangshan segment of this fault. Based on method of shallow seismic exploration, we carried out a systematic exploration of this fault to get its accurate position and activity characteristics. The results show that Anqiu-Juxian Fault in Suqian City is mainly characterized by dextral strike-slip, associated with both thrusting and extensional movement in different positions. A series of low hills were formed along the fault in the north of Suqian City, and a small graben basin was formed in the south of Suqian City, both are controlled by the dextral strike-slip movement of this fault. The Jiangsu segment of Anqiu-Juxian Fault in general is characterized by dextral strike-slip with thrusting movement. But some parts of it are characterized by dextral strike-slip with extensional movement. The Jiangsu segment of Anqiu-Juxian Fault experienced a number of activities since the late Quaternary, with an obvious activity in Holocene. The seismic activities of Jiangsu segment of Anqiu-Juxian Fault have the characteristic of high intensity and low frequency. Its activities decrease gradually from north to south as a whole.