Neoproterozoic tectonic evolution of the Hongseong area, southwestern Gyeonggi Massif, South Korea; implication for the tectonic evolution of Northeast Asia

Two types of Neoproterozoic metabasites occur together with regionally intruded arc-related Neoproterozoic granitoids (ca. 850–830 Ma) in the Hongseong area, southwestern Gyeonggi Massif, South Korea, which is the extension of the Dabie–Sulu collision belt in China. The first type of metabasite (the Bibong and Baekdong metabasites) is a MORB-like back-arc basin basalt or gabbro formed at ca. 890–860 Ma. The Bibong and Baekdong metabasites may have formed during back-arc opening by diapiric upwelling of deep asthenospheric mantle which was metasomatized by large ion lithophile element (LILE) enriched melt or fluid derived from the subducted slab and/or subducted sediment beneath the arc axis. The second type of metabasite (the Gwangcheon metabasite) formed in a plume-related intra-continental rift setting at 763.5 ± 18.3 Ma and is geochemically similar to oceanic island basalt (OIB). These data indicate a transition in tectonic setting in the Hongseong area from arc to intra-continental rift between ca. 830 and 760 Ma. This transition is well correlated to the Neoproterozoic transition from arc to intra-continental rift tectonic setting at the margin of the Yangtze Craton and corresponds to the amalgamation and breakup of Rodinia Supercontinent.     

Tectono-sedimentary events and geodynamic evolution of the Mesozoic and Cenozoic basins of the Alpine Margin,Gulf of Tunis,north-eastern Tunisia offshore

The structural pattern, tectono-sedimentary framework and geodynamic evolution for Mesozoic and Cenozoic deep structures of the Gulf of Tunis (north-eastern Tunisia) are proposed using petroleum well data and a 2-D seismic interpretation. The structural system of the study area is marked by two sets of faults that control the Mesozoic subsidence and inversions during the Paleogene and Neogene times: (i) a NE-SW striking set associated with folds and faults, which have a reverse component; and (ii) a NW–SE striking set active during the Tertiary extension episodes and delineating grabens and subsiding synclines. In order to better characterize the tectono-sedimentary evolution of the Gulf of Tunis structures, seismic data interpretations are compared to stratigraphic and structural data from wells and neighbouring outcrops. The Atlas and external Tell belonged to the southernmost Tethyan margin record a geodynamic evolution including: (i) rifting periods of subsidence and Tethyan oceanic accretions from Triassic until Early Cretaceous: we recognized high subsiding zones (Raja and Carthage domains), less subsiding zones (Gamart domain) and a completely emerged area (Raouad domain); (ii) compressive events during the Cenozoic with relaxation periods of the Oligocene-Aquitanian and Messinian-Early Pliocene. The NW–SE Late Eocene and Tortonian compressive events caused local inversions with sealed and eroded folded structures. During Middle to Late Miocene and Early Pliocene, we have identified depocentre structures corresponding to half-grabens and synclines in the Carthage and Karkouane domains. The north–south contractional events at the end of Early Pliocene and Late Pliocene periods are associated with significant inversion of subsidence and synsedimentary folded structures. Structuring and major tectonic events, recognized in the Gulf of Tunis, are linked to the common geodynamic evolution of the north African and western Mediterranean basins.     

Seismic tectono-stratigraphy of fluvio-deltaic to deep marine Miocene silicoclastic hydrocarbon reservoir systems in the Gulf of Hammamet,northeastern Tunisia

Most of hydrocarbon accumulations within the Gulf of Hammamet foreland basins in eastern Tunisia are reservoired within the Upper Miocene Birsa and Saouaf sandstones. It is the case of Birsa, Tazarka, Oudna, Baraka, Maamoura, Cosmos and Yasmine fields. These sandstones constitute oil and gas fields located on folded and faulted horst anticline highs and described as varying from shoreface to shallow marine and typically exhibit excellent reservoir quality of 30 to 35% porosity and good permeability from 500 to 1100 md. In addition, the fracturing of faults enhanced their reservoir quality potential. However, due to the lack of seismic stratigraphic studies to highlight depositional environment reservoir characterization and distribution, petroleum exploration faces structural and stratigraphic trap types and remains on targeting only high fold closures with limited reserve volumes of hydrocarbons. As an example of the Birsa concession case, syn-sedimentary tectonic structuring and geodynamic evolution during Middle to Upper Miocene Birsa reservoir sequences have guided the distribution of depositional environment of sandstone channel systems around horst and grabens by E-W, NE-SW and N-S strike slip flower faults controlling the subsidence distribution combined with the eustatic sea level variations. Seismic sequence stratigraphy study of Miocene Birsa reservoir horizons, based on the analysis and interpretations of E-W and N-S 3D selected regional lines that were compared and correlated to outcrops and calibrated by well data, permitted to highlight the basin configuration and sequence deposit nature and distribution. Sedimentary infilling of the basin from Langhian Ain Ghrab carbonate to Serravallian Tortonian Birsa and Saouaf sandstone and shale formations is organized in four third-order seismic sequences, limited by regional erosional toplap, onlap and downlap unconformity surfaces and by remarkable chronostratigraphic horizons of forced and normal erosive lowstand and highstand system tracts separated by transgressive and maximum flooding surfaces. Reconstructed sedimentary paleo-environment distribution vary from deltaic fluvial proximal deposits in the northern part of the high central Birsa horst to a delta front and prodelta coastal and shelf shore face and shore line channelized deposits in the surrounding borders of grabens. Distal deposits seem to be distributed from upper to lower slope fans and probably to the basin floor on the flanks of the subsiding grabens. Synthetic predictive paleogeographic depositional reservoir fairway map distribution of Lower, Middle and Upper Birsa sandstone reservoirs highlights four main domains of channelized superposed and shifted reservoirs to explore.     

藏西北黑石北湖一带新近纪火山岩的特征及构造意义

青藏高原西北部黑石北湖一带发育的橄榄安粗岩系列火山岩具有由早到晚从基性到中性连续演化的特征，3期火山活动期次分明，以中心式喷发为主，K-Ar年龄分别为9．23Ma、3．19Ma和3Ma。该火山岩的稀土元素、微量元素、同位素组成特征与藏北其他地区的新生代火山岩基本相近。火山活动为新构造活动的响应，受控于青藏高原隆升过程中产生的走滑断裂。     

Neogene sediment deformations and tectonic features of northeastern Tunisia: evidence for paleoseismicity

The Neogene stratigraphic series is characterized by predominant clayey facies alternated by other sand layers. The outcrop and subsurface studies show varied and complex styles of deformations and lead to relate the structures to paleoseismic events. The seismicity of eastern onshore and offshore Tunisian margin follows the master fault corridors oriented globally N–S, E–W, and NW–SE that correspond to the bordering faults of grabens and syncline corridors and associated faulted drag fold structures oriented NE–SW. Epicenters of magnitudes between 3 and 5 are located along these border fault corridors. The Neogene strata record brittle structures, including numerous and deep faults and fractures with straight and high-angle dipping planes. The structuring of NE–SW en echelon folds and synclines inside and outside NW–SE and E–W right lateral and N–S and NE–SW left lateral tectonic corridors indicates the strike-slip type of bordering faults and their seismogenic nature. Wrench fault movements that induce mud and salt diapirs, mud volcanoes, and intrusive ascensions are related to seismic shocks. Seismic waves caused by activity along one, or most likely, several tectonic structures would have propagated throughout the Quaternary cover producing seismites. The similarity of deposits, structuring, and seismites between the Tunis-Bizerte to the North and Hammamet-Mahdia to the South accredits the hypothesis that the seismic episodes might have affected sedimentation patterns along the Sahalian large geographic area. The paleoseismic events in northeastern Tunisia might be related to tectonic fault reactivations through time. This hypothesis is consistent with the geomorphologic context of the study area, characterized by several morphostructural lineaments with strong control on the sediment distribution, as well as uplifted and subsiding terrains. The estimated magnitude of the seismic events and the great regional tectonically affected areas demonstrate that the northeastern Tunisia experienced stress through the last geological episodes of its evolution. This Neogene kinematic reconstruction highlights the neotectonic system inducing the actual seismicity on this margin. Therefore, there is a straight relationship between deepseated faults and seismicity.     

Strain partitioning between the Suruga Trough and the Zenisu Thrust: Neogene to present tectonic evolution in the onland and offshore Tokai district, Japan

The Tokai district in central Japan is located close to the convergent boundary between the Philippine Sea and Eurasian plates, and has experienced not only repeated large interplate earthquakes but also intense aseismic movement. In this paper, the spatial and temporal tectonic evolution of the Tokai district, particularly around the Omaezaki area, is discussed to assess whether the district has been and will be active or inactive. According to a geological survey, the horizontal crustal shortening strain can imply the hypothetical tectonic model that the area has been getting less active and the strain rate since the Neogene can be calculated as 12% and 2×10⁻⁶%/year, respectively. The present interseismic horizontal crustal strain and strain rate around the Omaezaki area are approximately 4×10⁻⁷% and 4×10⁻⁹%/year. By comparing these rates, the decrease since Neogene can imply the hypothetical tectonic model that the area has been getting less active influenced by the strain partitioning between the Suruga Trough and the Zenisu Thrust.     

东北地区晚古生代区域构造演化

东北地区主要由东部佳木斯地块、中部兴安—松嫩地块和西部额尔古纳地块构成,各地块之间主要构造带拼合时代的研究表明,晚古生代之前各地块之间已经完成拼合,形成了统一的佳—蒙地块。晚古生代开始东北地区进入统一的盖层演化阶段,在佳—蒙地块南缘发育了晚古生代具有大陆边缘沉积特征的盖层建造。晚古生代早期佳—蒙地块南缘为活动陆缘,在～320Ma向北的俯冲过程中古亚洲洋板块发生断离,形成火山弧,同时导致其北侧"贺根山"弧后洋的拉开,持续的向北俯冲导致弧-陆碰撞,并于～280Ma贺根山洋已经完全闭合。佳—蒙地块南缘开始由活动陆缘向被动陆缘环境转化,最后在晚二叠世末期古亚洲洋完全闭合转入内陆环境。     

渤海湾地区中生代构造活动与沉积作用

通过研究渤海湾及周边地区中生代南部典型露头剖面的沉积特征及中部岩相古地理特征,认为中生代渤海湾地区由一系列受到断层严格控制的断陷盆地组成,主要发育冲积扇-河流-湖泊沉积体系,湖泊内部包括滨浅湖、滩坝和半深湖等亚相;经历了由冲积扇-河流沉积体系向上演化为湖泊沉积体系,再逐渐演化为冲积扇-河流沉积体系的过程;欧亚构造域的西伯利亚板块、扬子板块与华北板块的挤压拼接在渤海湾地区侏罗纪盆地充填中起到主要的控制作用;郯庐断裂的左行走滑在渤海湾地区白垩纪盆地充填中起到主要的控制作用。     

Palaeogeographic,climatic and tectonic change in southeastern Australia: the Late Neogene evolution of the Murray Basin

The Murray Basin is a low-lying but extensive intracratonic depocentre in southeastern Australia, preserving an extraordinary record of Late Neogene sedimentation. New stratigraphic and sedimentologic data allow the long-term evolution of the basin to be re-evaluated and suggest a significant role for: (1) tectonism in controlling basin evolution, and (2) progressive and step-wise climatic change beginning in the early Pleistocene. Tectonic change is associated with regional uplift, occurring at approximately the same rate from the early Pliocene until the present day, and possibly associated with changing mantle circulation patterns or plate boundary processes. This uplift led to the defeat and re-routing of the Murray River, Australia’s major continental drainage system. Key to our interpretation is recognition of timing relationships between four prominent palaeogeographic features – the Loxton-Parilla Sands strandplain, the Gambier coastal plain, palaeo megalake Bungunnia and the Kanawinka Escarpment. Geomorphic and stratigraphic evidence suggest that during the Early Pliocene the ancestral Murray River was located in western Victoria, flowing south along the Douglas Depression. Relatively small amounts of regional uplift (<200 m) defeated this drainage system, dramatically changing the palaeogeography of southeastern Australia and forming Plio-Pleistocene megalake Bungunnia. At its maximum extent Lake Bungunnia covered more than 50,000 km², making it one of the largest known palaeo- or modern-lakes in an intracontinental setting. Magnetostratigraphic constraints suggest lake formation c. 2.4 Ma. The formation of Lake Bungunnia influenced the Pliocene coastal dynamics, depriving the coastline of a sediment source and changing the coastal system from a prograding strandline system to an erosional one. Erosion during this period formed the Kanawinka Escarpment, a palaeo sea-cliff and one of the most prominent and laterally extensive geomorphic features in southeastern Australia. Marine sediments c. 800 ka to c. 1.16 Ma represent the time of re-establishment of depositional coastal dynamics and of a permanent outlet for the Murray River. This age range is consistent with our best estimate of the age of the youngest Lake Bungunnia sediments and points towards an early Pleistocene age for the demise of the lake system. The youngest Lake Bungunnia sediment, present on a number of distinct terraces, suggests that progressive, step-wise climatic change played a role in the demise of the lake. However, in order for the ancestral Murray River system to have been able to breach the pre-existing tectonic dam, it is likely that tectonic change and/or temporarily enhanced discharge was also significant. This scenario indicates that the modern Murray River has only been in existence for at most 700 ka.     

New insights on the tectonic and paleogeographic evolution of the central Atlasic domain of Tunisia

Geological and geoseismic profiles and well data gathered with field observations from the Atlasic Chain in central Tunisia highlight folded structures, tectonic events, and significant faults. These events controlled basin formation and evolution during successive Mesozoic extensional phases, followed by the tectonic inversion during the Atlasic Orogeny known on a Tethyan scale. The Cretaceous extension is well recorded through deposition, which supplied the normal faults system and influenced sediment distribution and regional subsidence. The major event is the normal slip of the principle inherited fault during the Cretaceous subsidence. The northwestern blocks, which are north of the faults of Mrhila–Trozza–Cherichira and Ballouta and west of the NS axis, correspond to continually subsiding areas of the Upper Cretaceous series. Subsequent faulting reactivated compressional structures such as strike-slips, reverse, and thrust faults during the Tertiary Orogeny which largely affected the Tunisian Atlasic domain. Geological profiles point out the evidence of the Upper Cretaceous emersion of the central Tunisia domain and lateral thickness variation of the series from Jurassic to Quaternary, unconformities, and halokinesis movement.     

Style and timing of tectonic deformation across the Bou Arada-El Fahs troughs system,Northeast Tunisia: integration in the structural evolution of Atlas fold and thrust belt

The Bou Arada-El Fahs troughs system is a particularly E-W trending collapsed structure with the manifestation of normal-to-strike-slip faults. A combined multi-source and multi-scalar structural and geophysical investigation provides important insights on the geometry and the kinematics evolution of trough systems in the Atlas of Tunisia. New data, as well as a reappraisal of available data show that the studied troughs system is established during three main successive events: the Oligocene-Miocene, the Tortonian, and the Plio-Quaternary events. The goal of this paper is to present the structural evolution of the study area, on a pre-structured substratum. The structural evolution progressed from an extensional event, manifested by the formation of grabens, passing by an episode of reactivation of faults related troughs in strike-slip motion during the Atlas compression accompanied by an en-échelon folding in foot wall and hanging wall. These results acquired and presented in the following order: We will initially present the geological context by integrating and correlating the lithostratigraphic data. We continue by examining the geometry and kinematics of structure-related troughs via the detailed geological mapping, the interpretation of available 2D seismic data, and the interpretation of processed fault slip data. This integrated geological and geophysical study allows a better understanding of the BETS, and makes it possible to propose a new geometrical and kinetic model of the establishment of trough structure in the Tunisian Atlas.     

新近纪以来中国构造演化特征与天然气田的分布格局

中国地处三大板块间的三角地带 ,是世界上新近纪以来构造运动活跃地区之一 ,与油气成藏及保存条件相关的主要特征是 :(1)在西部 ,古老造山带的重新活跃 ,在其前缘形成前陆盆地及逆冲构造 ,新近纪以来的急剧沉降、快速沉积 ,促进了深部源岩有机质的演化进程 ,也为生物气藏的形成创造了有利的地质条件 ;(2 )多期次的构造热事件及高热流值促进了有机质的快速演化、成藏 ,以及异常高压及泥拱等特殊构造的形成 ;(3)多期次构造运动为油气的快速运聚、幕式充注成藏提供了优质输导系统 ,为超晚期快速成藏提供了储聚场所 ;(4 )大断裂、岩浆及深部热流体的活动 ,不仅促进有机成因油气藏的形成 ,也是无机成因气的主要释放和聚集时期。新近纪以来构造演化特征在西部影响最广泛 ,也最深刻 ,形成的前陆盆地是中国重要天然气聚集区之一 ,是这些盆地本部气藏最终形成、定型时期 ,并在造山带内形成了近百个小型断陷盆地 ,形成了新的油气勘探领域。在中部 ,是四川盆地所有气田最终的形成、定型时期 ;在鄂尔多斯盆地促进了靖边至乌审旗地区天然气进一步富集。在东部 ,渤海海域形成一批大中型油气田 ,促进了其他盆地 (坳陷 )不同成因气藏的形成 ;在近海海域 ,既促进了有机成因气藏快速形成 ,也促进了无机成因非烃气藏以及无?     

甘肃昌马地区寒武纪构造演化探讨

位于北祁连山造山带西段的昌马地区,1:5万东湾、三道湾幅区调在中寒武世地层中发现Leiosphaeridia,Lophosphaeridium,Cymatiosphaera,Retisphaeridium,Synsphaeridium,Multiplicis-phaeridium,Retinarites等晚震旦世的藻类化石。据此,笔者将本区中寒武世地层解体为3部分:晚震旦世地层、早寒武世地层和中寒武世黑茨沟组。并对锅底坑蛇绿混杂岩带进行了确认,在此基础上对本区寒武纪构造演化模式作以探讨。     

中国近海新生代盆地构造差异性演化及油气勘探方向

中国近海处于欧亚、印度-澳大利亚及太平洋三大板块的交汇地带,其盆地形成与演化受控于洋、陆板块的相互作用,区域构造背景对盆地形成和演化起到了重要的作用,并由此导致了中国近海盆地显著的分段性和差异性演化特征。渤海海域、北黄海至南黄海盆地属于陆内裂陷型盆地;东海海域为活动大陆边缘弧后裂陷型盆地;珠江口盆地和琼东南盆地为被动大陆边缘型盆地;莺歌海海域为转换大陆边缘型盆地。受此影响,油气分布有明显的分段分区性,渤海—南黄海陆内盆地以成油为主,东海弧后盆地以成气为主,南海北部大陆边缘北部成油、南部成气,莺歌海转换盆地以成气为主。中国近海未来的找油领域主要在渤海、珠江口盆地北部和北部湾盆地;找气领域主要在东海盆地、南海北部深水区和莺歌海盆地6大领域。     

The evolution of pre-existing structures during the tectonic inversion process of the Atlas chain of Tunisia

Previous studies on the plate movement between Africa and Eurasia have pointed out the evidence of successive phases of transtension and transpression. The transtensional regime was active between Jurassic and Cretaceous times. It led to extensional structures which were reactivated during the Cenozoic transpressional regime as consequence of the Africa–Europe convergence. In this paper, we used satellite images and field observations from Central Tunisia to demonstrate the role of the previous extension tectonics in the structural evolution of the Atlassic chain for the tectonic inversion process. In the study area, the geometry of structures and fault kinematics is used to document transition from transtension to transpression. The tectono-sedimentary record reflects the mechanical influence of reactivation of previous tectonics in the structural evolution of the study area and points out the significant role of the tectonic inheritance in the development of the Atlassic chain of Tunisia.     

Orogen-parallel brittle extension as a major tectonic imprint in the Neogene evolution of the south-western Alpine arc

International Journal of Earth Sciences - We present a new analysis of the late Alpine brittle deformation in the southern branch of the western Alpine arc, focusing on the stack of internal...     

Zircon SHRIMP U-Pb dating of the Neogene coral reefs,Xisha Islands,South China Sea: implications for tectonic evolution

The Xisha Block is a minor one in the South China Sea and an important tectonic unit in the northwestern part of the region. Zircon SHRIMP U-Pb ages for three volcanic intrusive core samples from Xike-1, an exploratory well penetrating the bioherms of the Xisha Islands. The core samples are from the Miocene reef carbonate bedrock and are recognized as dark-gray biotite-hornblende gabbro, gray fine-grained biotite diorite, and gray fine-grained granite, respectively. Zircon cathodoluminescence (CL) images and trace Th, U and Pb compositions of the zircons show that these rocks are of volcanic intrusive origin. Zircon SHRIMP U-Pb dating yielded six groups of ages, ranging from 2451-1857 Ma to early Cretaceous, which indicate that the formation and evolution of the Xisha Block was affected by the evolution and closure of Neotethys Ocean, probably within its eastern extension into South China Sea. Both old, deep-sourced material, including fragments from Rodina supercontinent, and recent mantle-derived magma products contributed to the emergence and formation of the Xisha block. The SHRIMP U-Pb results also proved that this process differed from that of the Kontum massif, the Hainan Block, and the South China Block, but is similar to that of the Nansha and Zhongsha blocks. The process was associated with the effects of Yanshanian magmatism induced by subduction mechanisms of the Paleo-Pacific Plate or the reworking of the multiple magmatisms since the Early to mid-Yanshanian, possibly jointly experienced by the Xisha-Zhongsha-Nansha Block.     

Neogene evolution of the Campo de Dalias and the surrounding offshore areas - (Northeastern Alboran Sea)

Abstract

The Campo de Dalias is an emerged portion of the Alboran Sea, located on its northeastern margin. The study of this basin and its surrounding offshore areas reveals the structure on the region, whose outstanding feature is the N70-80E anticline extending from Guardias Viejas to Roquetas and continuing eastward under the sea. The other parts of the structure are characterized by several fault sets, the most important of which are those of N 70-9OE, N 120E and N45E direction. Some of these fault sets of originally different ages later replayed throughout the late Miocene up to the Quaternary. These replays seem to have occurred in approximately N-S compressive situations.

The main compressive events took place in the latest Torto-nian and early Pleistocene. Between these two events a stage of considerable subsidence in the Pliocene basin can be detected, which caused the accumulation of sediments over a thousand metres thick in some places. Equally, we can detect an important uplift of the surrounding reliefs coeval with subsidence. Two transgressive situations are recorded and two important eustatic falls and partial emersion of the basin margin, mainly during the Messinian.