A fore-arc origin for the Thrace Basin,NW Turkey

Hydrocarbon-bearing Thrace Basin occupies much of the European part of Turkey. The Middle Eocene to Oligocene sequence in the centre of the basin exceeds 9 km in thickness. Based on the stratigraphy, structure and the regional context of this basin, we propose that it developed as a fore-arc basin between the medial Eocene and the Oligocene, above the northward subducting Intra-Pontide Ocean. Its post-Miocene history has been dominated mainly by wrench tectonics resulting from the activity of the now-deactivated northwestern strand. of the present-day North Anatolian fault zone.     

库车坳陷同沉积演化的古地磁研究

运用古地磁学方法研究了库车坳陷第三系同沉积褶皱,同褶皱检验发现上新统和渐新统原生剩磁主要是同沉积剩磁,说明该区上新世和渐新世表现出较强的构造活动性;因而,对推断控制库车坳陷油气分布的构造格架和相关的构造形迹有十分重要的地质意义。     

The rodent fauna from the Adapazarı pull-apart basin (NW Anatolia): its bearings on the age of the North Anatolian fault

To the east of the Sea of Marmara, the North Anatolian fault (NAF) branches into two strands, namely the northern and the southern strands. The Adapazarı pull-apart basin is located in the overlapping zone of the Dokurcun and the İzmit–Adapazarı segments of the northern strand. The combined temporal ranges of the arvicolids from the Karapürçek formation (the first unit of the basin fill), deposited in the primary morphology of the Adapazarı pull-apart basin, cover the latest Villanyian (latest Pliocene) and the Biharian (Early Pleistocene) time interval. The Değirmendere fauna collected from the lowermost sediments of this formation suggests that the Adapazarı pull-apart basin started to form in the latest Pliocene. This, in turn, suggests that the dextral movement along the northern strand of the NAF commenced during the latest Pliocene. A new species, Tibericola sakaryaensis is also described.     

The rodent fauna from the Adapazarı pull-apart basin (NW Anatolia): its bearings on the age of the North Anatolian fault

Abstract

To the east of the Sea of Marmara, the North Anatolian fault (NAF) branches into two strands, namely the northern and the southern strands. The Adapazan pull-apart basin is located in the overlapping zone of the Dokurcun and the ?zmit-Adapazan segments of the northern strand. The combined temporal ranges of the arvicolids from the Karapürçek formation (the first unit of the basin fill), deposited in the primary morphology of the Adapazan pull-apart basin, cover the latest Villanyian (latest Pliocene) and the Biharian (Early Pleistocene) time interval. The De?irmendere fauna collected from the lowermost sediments of this formation suggests that the Adapazan pull-apart basin started to form in the latest Pliocene. This, in turn, suggests that the dextral movement along the northern strand of the NAF commenced during the latest Pliocene. A new species, Tibericola sakaryaensis is also described. © 2001 Éditions scientifiques et médicales Elsevier SAS     

江南东段地区NE-SW向断裂带断层滑移矢量反演及其大地构造意义

华南中-新生代构造演化受太平洋构造域和特提斯洋构造域的联合控制.以江南东段NE-SW向景德镇-歙县剪切带和球川-萧山断裂中发育的脆性断层为研究对象,利用野外交切关系和断层滑移矢量反演方法厘定了7期构造变形序列并反演了各期古构造应力场,讨论了断层活动的时代及其动力学.白垩纪至新生代研究区7期古构造应力场分别为:(1)早白垩世早期(136～125Ma)NW-SE向伸展;(2)早白垩世晚期(125～107Ma)N-S向挤压和E-W向伸展;(3)早白垩世末期至晚白垩世早期(105～86Ma)NW-SE向伸展;(4)白垩世中期(86～80Ma)NW-SE向挤压和NE-SW向伸展;(5)晚白垩世晚期至始新世末期(80～36Ma)N-S向伸展;(6)始新世末期至渐新世早期(36～30Ma)NE-SW向挤压和NW-SE向伸展;(7)渐新世早期至中新世中期(30～17Ma)NE-SW向伸展.结合区域地质研究表明,第1期至第4期古构造应力场与古太平洋构造域的板片后撤、俯冲以及微块体(菲律宾地块)间的碰撞作用有关;第5期伸展作用受控于新特提斯构造域俯冲板片后撤,而第6期和第7期古构造应力场主要与印-亚碰撞的远程效应有关.白垩纪至新生代,华南东部受伸展构造体制和走滑构造体制的交替控制.先存断裂的发育可能是导致华南晚中生代走滑构造体制的主要控制因素.     

大洋钻探与全球变化(一)——南极地区显生宙晚期气候演变历史及对全球的影响

通过介绍Ｊ．Ｐ．Ｋｅｎｎｅｔｔ为代表的“洋流说”阐述了大洋钻探２５年来约１０个航次研究所揭示的南极地区显生宙晚期气候演变的历史。晚白垩世时南极地区和全球一样暖和无冰，末期变冷，古新世开始后不久又转暖，早始新世－中始新世早期达顶峰，以后变冷。渐新世为主要冷却期，南极东部形成冰盖，中，晚中新世为另一重要冷却期，南极西部以至全部南极在中新世晚期－上新世早期最终形成稳定冰盖。德雷克海峡打开，环南极洋流（Ａ     

The Intra-Pontide ophiolites in Northern Turkey revisited:From birth to death of a Neotethyan oceanic domain

The Anatolian peninsula is a key location to study the central portion of the Neotethys Ocean(s)and to understand how its western and eastern branches were connected.One of the lesser known branches of the Mesozoic ocean(s)is preserved in the northern ophiolite suture zone exposed in Turkey,namely,the Intra-Pontide suture zone.It is located between the Sakarya terrane and the Eurasian margin(i.e.,Istanbul-Zonguldak terrane)and consists of several metamorphic and non-metamorphic units containing ophiolites produced in supra-subduction settings from the Late Triassic to the Early Cretaceous.Ophiolites preserved in the metamorphic units recorded pervasive deformations and peak metamorphic conditions ranging from blueschist to eclogite facies.In the nonmetamorphic units,the complete oceanic crust sequence is preserved in tectonic units or as olistoliths in sedimentary melanges.Geochemical,structural,metamorphic and geochronological investigations performed on ophiolite-bearing units allowed the formulation of a new geodynamic model of the entire"life"of the IntraPontide oceanic basin(s).The reconstruction starts with the opening of the Intra-Pontide oceanic basins during the Late Triassic between the Sakarya and Istanbul-Zonguldak continental microplates and ends with its closure caused by two different subductions events that occurred during the upper Early Jurassic and Middle Jurassic.The continental collision between the Sakarya continental microplate and the Eurasian margin developed from the upper Early Cretaceous to the Palaeocene.The presented reconstruction is an alternative model to explain the complex and articulate geodynamic evolution that characterizes the southern margin of Eurasia during the Mesozoic era.     

The structure and regional significance of the Talea Ori,Crete

On the basis of detailed geological mapping in the Talea Ori of Crete, metamorphic rocks previously interpreted as basement to the Plattenkalk Series are re-interpreted as down-faulted parts of the overlying Phyllite-Quartzite Series nappe. A supposed unconformity separating these two units is shown to be a high-angle fault. The Phyllite-Quartzite Series and overlying nappes were affected by two major deformational phases, whereas the Plattenkalk Series has a simpler structural history and was folded and imbricated by southwards-directed overthrusting which emplaced the Phyllite-Quartzite Series nappe and other overlying nappes in the Oligocene. We reject previous models of a huge inversion of the Plattenkalk Series and we also consider that considerable local inversion by tight to isoclinal folding and thrusting means that the stratigraphic thickness is much less than previously appreciated. The differences between the structural and sedimentological histories of the Plattenkalk Series and the overlying nappes implies that they were separated by a major crustal discontinuity, such as a transform or transcurrent fault, before the Oligocene overthrusting.     

A numerically calibrated reference level (MP28) for the terrestrial mammal-based biozonation of the European Upper Oligocene

The fauna of the Enspel (Westerwald) and the neighbouring Kärlich (Neuwied basin) fossil deposits correspond to the Upper Oligocene Mammal Paleogene (MP) reference level 28 and 28–30, respectively. Basaltic flows and a trachyte tuff terminating and predating the fossil deposit sedimentation allow to numerically calibrate the MP reference levels by radioisotope dating. Laser fusion ⁴⁰Ar/³⁹Ar step heating on volcanic feldspars yield a time interval of 24.9–24.5 Ma for reference level MP28 at Enspel and a maximum age of 25.5 Ma for the time interval MP28–MP30 at Kärlich. Interpolation between the time intervals determined for the Enspel reference level MP28 and the age of the global Oligocene/Miocene boundary of 24.0 ± 0.1 Ma taken from literature results in time intervals of 24.5–24.2 Ma and 24.2–23.9 Ma for the younger reference levels MP29 and MP30, respectively. These intervals of ≤ 0.4 m.y. for MP reference levels of the latest Oligocene are short relative to older Oligocene MP reference levels 21–27 between 34 and 25 Ma. Since subdivision into MP reference levels essentially is based on assemblages of mammal taxa and on evolutionary changes in tooth morphology of mammals short MP time intervals during the latest Oligocene indicate a rapid evolutionary change relative to the early Oligocene.     

青藏高原西南部南北向构造研究的新见解

广泛分布在青藏高原西南部的南北向构造,是高原新生代陆内汇聚变形的重要组成部分。经过中外学者40余年研究,至今已取得许多重要进展并形成了一些共识,也存在若干分歧。作者对南北向构造研究及某些共识的不同意见是：①南北向构造不仅有伸展构造形迹,还有褶皱、逆断、叠加等挤压构造形迹;②不能用裂谷系代表所有的伸展构造,也不能用裂谷系、地堑系等伸展构造名称代表高原西南部的全部南北向构造形迹。建议采用＂南北向构造＂这一包容性强的中性名称;③南北向构造最早产生于始新世-渐新世;④首先产生南北向伸展构造的是藏北羌塘-青南地区而非喜马拉雅地区;⑤大致在渐新世末-中新世初,青藏高原曾出现过一次短暂的东西挤压应力场,生成了各式挤压构造变形形迹。本文的新见解既丰富了南北向构造的成份与内涵,又可以此将南北向构造划分为早期（E2-3）伸展、中期（E3末-N1初）挤压、晚期（中新世及以后）再伸展3个发生、发展期。     

Origin of the Sea of Marmara as Deduced from Neogene to Quaternary Paleogeographic Evolution of its Frame

The Sea of Marmara Basin (SMB) is connected to the fully marine Mediterranean by the Dardanelles strait and to the brackish Black Sea by the Thracian Bosporus. This linkage to two different marine realms with contrasting water chemistry has been a prime control on the sedimentary history of the SMB, which in turn was controlled by its tectonics. Isolation from any of these realms resulted in drastic changes in its paleoceanographic conditions and made it a part either of the global ocean system or of a brackish-marine environment, depending on the realm from which the connection was severed.

The SMB represents the inundated part of the northwestern Anatolian graben system that resulted from the interaction between the North Anatolian fault (NAF) zone and the present N-S extensional tectonic regime of the Aegean. The geologic history of this basin began during the late Serravallian when the NAF was initiated. The first inundation of the basin coincided in both time and space with this initiation. The invading sea was the Mediterranean, which stayed there for a short period and subsequently was replaced by the Paratethys during the late Miocene. Paratethyan conditions prevailed in the basin until the latest Pliocene, when the second flooding from the Mediterranean occurred through the Dardanelles. Owing to glacio-eustatic sea-level changes during the Pleistocene, Paratethyan/Black Sea and Mediterranean conditions alternated. In the last (Würm) glaciation, the SMB was completely isolated and turned into a euxinic lacustrine environment, similar to the Black Sea at that time. Following the Würm glaciation, the Mediterranean Sea broke its way once more into the SMB and filled it with salt water. When sea level in the basin rose above the Bosporous sill at 7.5 Ka B.P., the present dual flow regime was established.     

泌阳凹陷新生代构造特征与形成机制及其与油气成藏的关系

根据地层层序特征 ,叠加在东秦岭造山带之上的泌阳凹陷伸展作用可以划分出 6个伸展作用幕。核二段沉积前泌阳凹陷以北东—南西向的伸展作用为主 ,构造变形受以正断层为主兼具左旋走滑分量的唐河—栗园断裂控制。核二段沉积期——廖庄组沉积末期构造应力场发生转变 ,以北西—南东向伸展作用为主 ,构造变形主要受以正断层为主兼具右旋走滑分量的泌阳—栗园断裂控制。断裂活动引起上盘构造变形 ,对先成构造进行改造。廖庄组沉积末期发生区域性的隆升作用 ,北西—南东向的伸展作用导致边界断裂上盘发生断块掀斜 ,地层遭受强烈剥蚀。核二段沉积以来尤其是廖庄组沉积末期 ,受北西—南东向不均匀伸展作用的影响 ,北西向走滑断层活动并影响盖层构造样式     

Evolutionary history of hoofed mammals during the Oligocene–Miocene transition in Western Europe

The biostratigraphy and diversity patterns of terrestrial, hoofed mammals help to understand the transition between the Palaeogene and the Neogene in Western Europe. Three phases are highlighted: (1) the beginning of the Arvernian (Late Oligocene, MP25-27) was characterised by a “stable” faunal composition including the last occurrences of taxa inherited from the Grande Coupure and of newly emerged ones; (2) the latest Arvernian (Late Oligocene, MP28-30) and the Agenian (Early Miocene, MN1-2) saw gradual immigrations leading to progressive replacement of the Arvernian, hoofed mammals towards the establishment of the “classical” Agenian fauna; (3) the beginning of the Orleanian (Early Miocene, MN3-4) coincided with the African-Eurasian faunal interchanges of the Proboscidean Datum Events and led to complete renewal of the Agenian taxa and total disappearance of the last Oligocene survivors. Faunal balances, poly-cohorts and particularly cluster analyses emphasise these three periods and define a temporally well-framed Oligocene–Miocene transition between MP28 and MN2. This transition started in MP28 with a major immigration event, linked to the arrival in Europe of new ungulate taxa, notably a stem group of “Eupecora” and the small anthracothere Microbunodon. Due to its high significance in the reorganisation of European, hoofed-mammal communities, we propose to name it the Microbunodon Event. This first step was followed by a phase of extinctions (MP29-30) and later by a phase of regional speciation and diversification (MN1-2). The Oligocene–Miocene faunal transition ended right before the two-phased turnover linked to the Proboscidean Datum Events (MN3-4). Locomotion types of rhinocerotids and ruminants provide new data on the evolution of environments during the Oligocene–Miocene transition and help understand the factors controlling these different phases. Indeed, it appears that the faunal turnovers were primarily directed by migrations, whereas the Agenian transitional phase mainly witnessed speciations.     

Structural zones and continental collision, Central Alps

The traverse of the Central Alps between Lake Constance and Lake Como (eastern Switzerland, northern Italy) allows the reconstruction of a cross-section through a collision belt some 140 km wide and 40 km deep. It can be described in terms of a series of structural zones (A–F), defined by the age and character of the latest phase of penetrative deformation affecting both basement and cover rocks, each zone showing a characteristic structural history. These zones do not coincide with the well-known tectono-stratigraphic Alpine subdivisions (Helvetic, Pennine, Austroalpine) which are based on gross geometry, facies and petrography. Zones A and B, in the north, developed during late Oligocene and Miocene times, affecting the Helvetic realm and the already overlying Pennine and Austroalpine units. Zone A is characterized by a steeply dipping penetrative cleavage S_A, zone B by the same cleavage later modified by nappe-forming movements. Zone F, in the south, also developed during the late Oligocene and Miocene, first as a monoclinal flexure, later as a steeply dipping zone of mylonitization and cataclasis (foliation S_f), affecting Pennine and Austroalpine units. The final manifestation of these movements was the Tonale line and their net result was the uplift of the region to the north by about 20 km. Between these two belts lay an area in which late Oligocene-Miocene movements had little effect — structural zones C (Pennine), D (Pennine-Austroalpine transition) and E (Austroalpine). In zones C and D, the latest phase of penetrative deformation, resulting in large recumbent fold structures and a penetrative foliation S_c zone C, can be dated as late Eocene-early Oligocene. This seems to be related to the overriding of the Austroalpine nappe complex (zone E), which already showed the effects of a late Cretaceous orogeny.Unravelling these events backwards, reveals, at the Eocene—Oligocene boundary, a southward dipping subduction zone in the process of locking. Its mouth is full of upper Cretaceous-Eocene flysch; its throat is choked by the Pennine nappe complex, undergoing the s_c ductile deformation. Before subduction, the Pennine nappe complex can best be described as a mega-mélange-a tectonic mixture of large fragments of continental basement, oceanic basement, trough-facies cover and platform-facies cover, already showing a complicated structural history. It is supposed that collision started in mid-Cretaceous times, not at a single subduction suture (trench), but by complicated surficial processes across a wide zone, as non-matching, rifted and thinned continental margins approached and small oceanic remnants were obducted. Post-mid-Oligocene events are essentially intra-plate compressional effects, combined with isostatic response.     

The Monte Orfano Conglomerate revisited: stratigraphic constraints on Cenozoic tectonic uplift of the Southern Alps (Lombardy, northern Italy)

The Monte Orfano Conglomerate (MOC), exposed in the foothills of the Southern Alps (northern Italy), is one of the few outcrops of sediments documenting the Cenozoic tectonic evolution of the Alpine retrowedge. Calcareous nannofossil biostratigraphy allowed us to constrain the upper part of the MOC, formerly attributed to the Early-Middle Miocene in the type-locality, to the earliest Miocene (Neogene part of the NN1 nannofossil zone). A likely latest Oligocene age is therefore suggested for the bulk of the underlying conglomerates, whose base is not exposed. Deposition of the MOC can be placed within the post-collisional tectonic uplift of the Alps, documented in the Lake Como area by the Como Conglomerate (CC) at the base of the Gonfolite Lombarda Group, and supports the correlation with Upper Oligocene clastic sediments cropping out further to the East, in the Lake Garda and in the Veneto-Friuli areas (“molassa”). The remarkable difference in petrographic composition between the western (CC) and eastern (MOC) clastics deposited in the Alpine retro-foreland basin highlights the synchronous tectonic activity of two structural domains involving different crustal levels. Whilst the bulk of the CC, that straddles the Oligocene/Miocene boundary, records largely the tectonic exhumation of the Alpine axial chain crystalline complexes, the coeval MOC consists of detritus derived from the superficial crustal section (Triassic to Paleogene sedimentary rocks) of the Alpine retrowedge and constrains the onset of the post-collisional deformation phase of the Southern Alps as not younger than the Late Oligocene.     

琼东南盆地断裂活动性定量计算及其发育演化模式

在地震剖面解释的基础上,运用断层活动速率法和位移-距离法对琼东南盆地主要断裂系统的活动性进行了定量计 算。结果表明,断裂的活动性与盆地的演化阶段相对应,同时可以在同裂陷阶段划分出始新世-早渐新世裂陷幕和晚渐新 世断坳转换幕,这两幕裂陷控制了盆地深部的基本构造格局。单条断层在早渐新世至晚渐新世期间断裂主要活动中心存在 由东向西迁移的过程,盆地断裂系统活动中心在晚渐新世至早中新世也存在由东向西迁移的过程,盆地内规模较大的复合 断裂带具有区段式活动的特征。将盆地内断裂系统发育模式总结为两种：以6号和11号断裂带为代表的简单生长模型,断裂 系统发育演化过程中表现为单一区段断层独立生长的特征,断层简单地由中间向两侧生长,断层位移距离曲线自始至终为 半椭圆型,且最大位移大致位于断层中部;以2号和5号断裂带为代表的生长连通型生长模式,断裂带由多条区段式活动的 断层生长连接形成,其生长发育过程表现为沿断层面纵向上最大滑移量由各个区段的中心向各个区段交汇处迁移,由此各 个区段断端破裂扩展,最终相互连接而形成一条大型断裂带。     

Multistage shortening in the Dauphiné zone (French Alps): the record of Alpine collision and implications for pre-Alpine restoration

Three-dimensional modelling tools are used with structural and palaeomagnetic analysis to constrain the tectonic history of part of the Dauphiné zone (external Western Alps). Four compressive events are identified, three of them being older than the latest Oligocene. Deformation D1 consists of W–SW directed folds in the Mesozoic cover of the study area. This event, better recorded in the central and southern Pelvoux massif, could be of Eocene age or older. Deformation D2 induced N-NW-oriented basement thrusting and affected the whole southern Dauphiné basement massifs south of the study area. The main compressional event in the study area (D3) was WNW oriented and occurred before 24 Ma under a thick tectonic load probably of Penninic nappes. The D2-D3 shift corresponds to a rapid transition from northward propagation of the Alpine collision directly driven by Africa-Europe convergence, to the onset of westward escape into the Western Alpine arc. This Oligocene change in the collisional regime is recorded in the whole Alpine realm, and led to the activation of the Insubric line. The last event (D4) is late Miocene in age and coeval with the final uplift of the Grandes Rousses and Belledonne external massifs. It produced strike-slip faulting and local rotations that significantly deformed earlier Alpine folds and thrusts, Tethyan fault blocks and Hercynian structures. 3D modelling of an initially horizontal surface, the interface between basement and Mesozoic cover, highlights large-scale basement involved asymmetric folding that is also detected using structural analysis. Both, Jurassic block faulting and basement fold-and-thrust shortening were strongly dependent on the orientation of Tethyan extension and Alpine shortening relative to the late Hercynian fabric. The latter’s reactivation in response to oblique Jurassic extension produced an en-échelon syn-rift fault pattern, best developed in the western, strongly foliated basement units. Its Alpine reactivation occurred with maximum efficiency during the early stages of lateral escape, with tectonic transport in the overlying units being sub-perpendicular to it.     

Latest Triassic to Early Jurassic Thrusting and Exhumation in the Southern Ordos Basin,North China: Evidence from LA‐ICP‐MS‐based Apatite Fission Track Thermochronology

The contractional structures in the southern Ordos Basin recorded critical evidence for the interaction between Ordos Basin and Qinling Orogenic Collage. In this study, we performed apatite fission track(AFT) thermochronology to unravel the timing of thrusting and exhumation for the Laolongshan-Shengrenqiao Fault(LSF) in the southern Ordos Basin. The AFT ages from opposite sides of the LSF reveal a significant latest Triassic to Early Jurassic time-temperature discontinuity across this structure. Thermal modeling reveals at the latest Triassic to Early Jurassic, a ~50°C difference in temperature between opposite sides of the LSF currently exposed at the surface. This discontinuity is best interpreted by an episode of thrusting and exhumation of the LSF with ~1.7 km of net vertical displacement during the latest Triassic to Early Jurassic. These results, when combined with earlier thermochronological studies, stratigraphic contact relationship and tectono-sedimentary evolution, suggest that the southern Ordos Basin experienced coeval intense tectonic contraction and developed a north-vergent fold-and-thrust belt. Moreover, the southern Ordos Basin experienced a multi-stage differential exhumation during Mesozoic, including the latest Triassic to Early Jurassic and Late Jurassic to earliest Cretaceous thrust-driven exhumation as well as the Late Cretaceous overall exhumation. Specifically, the two thrust-driven exhumation events were related to tectonic stress propagation derived from the latest Triassic to Early Jurassic continued compression from Qinling Orogenic Collage and the Late Jurassic to earliest Cretaceous intracontinental orogeny of Qinling Orogenic Collage, respectively. By contrast, the Late Cretaceous overall exhumation event was related to the collision of an exotic terrain with the eastern margin of continental China at ~100 Ma.     

Cryptic tectonic domains of the Klamath Mountains, California and Oregon

Numerous fragments of oceanic crust and island arcs make up the Klamath Mountains province. These fragments were joined together (amalgamated) in an oceanic setting during Paleozoic and Mesozoic collisional events and were accreted to North America as a composite unit during latest Jurassic or earliest Cretaceous time. The roughly arcuate and concentric distribution of the terranes of the Klamath Mountains does not now seem to be a result of simple oroclinal bending as earlier believed. Although commonly described as a west-facing arcuate structure, the province is cut diagonally by a vaguely defined NW-trending zone of discontinuity, or hinge line, that divides the province into NE and SW tectonic domains. The zone of discontinuity is marked by a number of lithic and structural anomalies, and particularly by the distribution of a remarkable series of belts of plutonic rocks. The terranes, regional structures, and plutonic belts of the NE domain trend NE and are generally wider and more coherent than the narrow NW-trending terranes and plutonic belts of the SW domain. Most plutonic belts of the NE domain do not have equivalents in the SW domain. Paleomagnetic evidence suggests that all the plutonic belts, except possibly the youngest (the earliest Cretaceous Shasta Bally belt), were emplaced before the Klamath Mountains terranes finally accreted to North America.     

南海西部晚渐新世主要断裂活动特征及与红河断裂之关系

南海的形成演化是众多被动型边缘海中最复杂的,而南海西部的断裂带构造活动特征又是南海中最复杂的构造之一。本文针对前人提出的红河断裂带出莺歌海盆地后的东延、南延以及东南延问题,通过晚渐新世-早中新世琼东南盆地受到南北向挤压的区域应力场分析,认为这期的应力主要来自南海西部近南北向断裂带的右旋剪切活动,结合红河断裂带的构造运动特征,提出晚渐新世末南海西部发生断裂构造置换,红河断裂带17°30′N以南近SN走向部分被南海西缘断裂带所置换,并且构造活动特征与北部红河断裂带明显不同,南海西部晚渐新世前后两个时期不同的断裂构造活动特征反映了印度板块与欧亚板块碰撞造成的两种不同影响效应。