华北陆块南缘下震旦统顶部裂离不整合的发现及其地质意义

华北陆块南缘四十里长山地区下震旦统四顶山组叠层石白云岩与其上部凤台砾岩的接触界面上为一薄层黄铁矿,对其宏观和微观以及地球化学特征研究表明,这一接触界面为裂离不整合。这一裂离不整合的发现和确认为研究华北陆块在Rodnia超大陆裂解时期的地质响应提供了直接依据,也为研究凤台砾岩及其相对应地层的成因提供了重要的构造背景条件。     

Role of strike-slip faults in the Betic-Rifian orogeny

A new model for the Betic-Rifian orogeny of the Western Mediterranean (Spain and North Africa) is proposed in which four strike-slip faults play an important role; the faults are not of the same age. Two faults, the left-lateral Jebha fault to the south (in Morocco and principally in the Mediterranean Sea) and the right-lateral North Betic fault (southern Spain) to the north, define the boundaries of the Alboran block (Betic and Rifian internal zones). Final movement along these faults was during the Burdigalian time. Two other faults, the left-lateral Nekor fault (North Africa) to the south of the Jebha fault and the right-lateral Crevillente fault, somewhat to the north of the North Betic fault, define a larger Alboran block (including part of the Betic and Rifian external zones) that was present during the Tortonian.The following sequence of events is proposed:

1. (a) During the Eocene and Oligocene, the African and European plates converged in a N-S sense causing the breakup and overthrusting of the Betic, Rifian and Kabyle internal zones and then the movement towards the WSW of the Alboran block by slip along the Jebha and North Betic faults.

2. (b) By the end of Burdigalian time, movement along the Jebha and North Betic faults ceased.

3. (c) With continued N-S convergence, the Nekor and Crevillente faults, which bound a larger Alboran block, were formed during the mid- and late Miocene. The Arc of Gibraltar (the zone lying between the four major faults) seems to be a result of WSW motion of a crustal block being thrust over external zones.

The model proposed adds to the earlier idea that tectogenesis proceeds from the interior to the exterior of an erogenic belt. In the Betic-Rifian orogeny major strike-slip fracture zones shifted to the exterior of the orogenic belt as the orogeny progressed in order to relieve the stress caused by locking of the more internal faults.     

北阿尔金南华纪双峰式火山岩的发现及构造意义

北阿尔金恰什坎萨伊沟南口火山岩显双峰式特征, 由变玄武岩和变流纹岩组成.地球化学分析表明变玄武岩源自富集地幔, 上侵过程中遭受地壳混染, 形成于大陆裂谷环境; 而变流纹岩与铝质A型花岗岩特征类似, 为幔源岩浆底侵下地壳部分熔融成因.变流纹岩锆石LA-ICP-MS U-Pb年龄为749.8±4.6 Ma, 代表火山岩的喷发年龄, 为北阿尔金洋的初始裂解事件提供了时代证据; 与北祁连洋初始裂解时代相近, 从洋盆的初始裂解时间证明北阿尔金与北祁连同为一个带."西域板块"新元古代中期岩浆活动与Rodinia超大陆裂解事件密切相关, 与扬子板块周缘岩浆活动有相似性, 可划分为裂解初期与峰期两个阶段.所发现北阿尔金南华纪双峰式火山岩正是Rodinia超大陆裂解峰期岩浆活动的产物.      

The timing of kimberlite magmatism in North America: implications for global kimberlite genesis and diamond exploration

Based on a compilation of more than 100 kimberlite age determinations, four broad kimberlite emplacement patterns can be recognized in North America: (1) a northeast Eocambrian/Cambrian Labrador Sea province (Labrador, Québec), (2) an eastern Jurassic province (Ontario, Québec, New York, Pennsylvania), (3) a Cretaceous central corridor (Nunavut, Saskatchewan, central USA), and (4) a western mixed (Cambrian-Eocene) Type 3 kimberlite province (Alberta, Nunavut, Northwest Territories, Colorado/Wyoming). Ten new U–Pb perovskite/mantle zircon and Rb–Sr phlogopite age determinations are reported here for kimberlites from the Slave and Wyoming cratons of western North America. Within the Type 3 Slave craton, at least four kimberlite age domains exist: I-a southwestern Siluro-Ordovician domain (450 Ma), II-a SE Cambrian domain (540 Ma), III-a central Tertiary/Cretaceous domain (48–74 Ma) and IV-a northern mixed domain consisting of Jurassic and Permian kimberlite fields. New U–Pb perovskite results for the 614.5±2.1 Ma Chicken Park and 408.4±2.6 Ma Iron Mountain kimberlites in the State Line field in Colorado and Wyoming confirm the existence of at least two periods of pre-Mesozoic kimberlite magmatism in the Wyoming craton.

A compilation of robust kimberlite emplacement ages from North America, southern Africa and Russia indicates that a high proportion of known kimberlites are Cenozoic/Mesozoic. We conclude that a majority of these kimberlites were generated during enhanced mantle plume activity associated with the rifting and eventual breakup of the supercontinent Gondwanaland. Within this prolific period of kimberlite activity, there is a good correlation between North America and Yakutia for three distinct short-duration (10 my) periods of kimberlite magmatism at 48–60, 95–105 and 150–160 Ma. In contrast, Cenozoic/Mesozoic kimberlite magmatism in southern Africa is dominated by a continuum of activity between 70–95 and 105–120 Ma with additional less-prolific periods of magmatism in the Eocene (50–53 Ma), Jurassic (150–190) and Triassic (235 Ma). Several discrete episodes of pre-Mesozoic kimberlite magmatism variably occur in North America, southern Africa and Yakutia at 590–615, 520–540, 435–450, 400–410 and 345–360 Ma. One of the surprises in the timing of kimberlite magmatism worldwide is the common absence of activity between about 250 and 360 Ma; this period is even longer in southern Africa. This >110 my period of quiescence in kimberlite magmatism is likely linked to relative crustal and mantle stability during the lifetime of the supercontinent Gondwanaland.

Economic diamond deposits in kimberlite occur throughout the Phanerozoic from the Cambrian (Venetia, South Africa; Snap Lake and Kennady Lake, Canada) to the Tertiary (Mwadui, Tanzania; Ekati and Diavik in Lac de Gras, Canada). There are clearly some discrete periods when economic kimberlite-hosted diamond deposits formed globally. In contrast, the Devonian event, which is such an important source of diamonds in Yakutia, is notably absent in the kimberlite record from both southern Africa and North America.     

华北地块北缘中新元古界沉积构造演化

根据文献资料及对研究区8 条实测剖面资料的综合分析结果表明,Columbia 超级大陆的裂解导致华北陆块北缘大陆裂 谷盆地的形成。随着大陆进一步伸展和洋壳的形成,华北地块北缘逐渐发展为被动大陆边缘。在1400 Ma 左右,即铁岭组 沉积后,华北地块北缘转变为活动大陆边缘。早期洋壳向华北地块低角度的俯冲造成弧后地区发生挤压（芹峪上升）,导致 铁岭组抬升和剥蚀,而后期洋壳高角度的俯冲又造成弧后区域发生强烈的伸展和断陷,沉积了下马岭组,并伴随辉绿岩的 侵入。华北地块与相邻地体之间的碰撞导致下马岭组的抬升（或蔚县抬升）以及碰撞花岗岩的形成,挤压构造发生的时间 对应于Rodinia 超级大陆的形成期。新元古代沉积是Rodinia 超级大陆裂解的结果。龙山组石英砂岩和海绿石砂岩是Rodinia 超级大陆裂解后的最早期沉积,记录了海侵初期的超覆过程。     

Structure and evolution of an obliquely sheared continental margin: Rio Muni, West Africa

Oblique-shear margins are divergent continental terrains whose breakup and early drift evolution are characterized by significant obliquity in the plate divergence vector relative to the strike of the margin. We focus on the Rio Muni margin, equatorial West Africa, where the ca. 70-km-wide Ascension Fracture Zone (AFZ) exhibits oblique–slip faulting and synrift half-graben formation that accommodated oblique extension during the period leading up to and immediately following whole lithosphere failure and continental breakup (ca. 117 Ma). Oblique extension is recorded also by strike–slip and oblique–slip fault geometry within the AFZ, and buckling of Aptian synrift rocks in response to block rotation and local transpression. Rio Muni shares basic characteristics of both rifted and transform margins, the end members of a spectrum of continental margin kinematics. At transform margins, continental breakup and the onset of oceanic spreading (drifting) are separate episodes recorded by discrete breakup and drift unconformities. Oceanic opening will proceed immediately following breakup on a rifted margin, whereas transform and oblique-shear margins may experience several tens of millennia between breakup and drift. Noncoeval breakup and drift have important consequences for the fit of the equatorial South American and African margins because, in reconstructing the configuration of conjugate continental margins at the time of their breakup, it cannot be assumed that highly segmented margins like the South Atlantic will match each other at their ocean–continent boundaries (OCBs). Well known ‘misfits’ in reconstructions of South Atlantic continental margins may be accounted for by differential timing of breakup and drifting between oblique-shear margins and their adjacent rifted segments.     

Tectonics of the Southern Ocean Passive Margins in the Africa–East Antarctica Region

Geotectonics - Based on geological and geophysical data for the conjugate Africa–East Antarctica margins, the peculiarities of preparation of the breakup of central Gondwana are discussed....     

非洲地区盆地演化与油气分布

非洲地区盆地整体勘探程度较低,待发现资源量大,是当前油气勘探开发的热点地区之一。非洲板块在显生宙主要经历了冈瓦纳大陆形成、整体运动和裂解3个构造演化阶段,形成多种不同类型的盆地。通过板块构造演化和原型盆地研究及石油地质综合分析,明确了不同类型盆地的构造特征与油气富集规律。北非克拉通边缘盆地形成于古生代早期,受海西运动影响,油气主要富集在挤压背景下形成的大型穹隆构造之中,以古生界含油气系统为主;北非边缘裂谷盆地海西运动之后普遍经历了裂谷和沉降,裂谷期各盆地沉降幅度和沉降中心的差异导致了油气成藏模式和资源潜力的差异;东、西非被动陆缘盆地形成于中生代潘吉亚大陆的解体、大西洋和印度洋张裂的过程中,西非被动陆缘盆地普遍发育含盐地层,形成盐上和盐下两套含油气系统,东非被动陆缘盆地结构差异较大,油气分布主要受盆地结构控制;中西非裂谷系是经历早白垩世、晚白垩世和古近纪3期裂谷作用而形成的陆内裂谷盆地,受晚白垩世非洲板块与欧亚板块碰撞的影响,近东西向展布盆地抬升剧烈,油气主要富集在下白垩统,北西南东向盆地受影响较弱,油气主要富集在上白垩统和古近系之中;新生代东非裂谷系盆地和红海盆地形成时间相对较晚,以新生界含油气系统为主,新生代三角洲盆地中油气分布主要受三角洲砂(扇)体展布和盆地结构所控制。     

A Cordilleran model for the evolution of Avalonia

Striking similarities between the late Mesoproterozoic–Early Paleozoic record of Avalonia and the Late Paleozoic–Cenozoic history of western North America suggest that the North American Cordillera provides a modern analogue for the evolution of Avalonia and other peri-Gondwanan terranes during the late Precambrian. Thus: (1) The evolution of primitive Avalonian arcs (proto-Avalonia) at 1.2–1.0 Ga coincides with the amalgamation of Rodinia, just as the evolution of primitive Cordilleran arcs in Panthalassa coincided with the Late Paleozoic amalgamation of Pangea. (2) The development of mature oceanic arcs at 750–650 Ma (early Avalonian magmatism), their accretion to Gondwana at ca. 650 Ma, and continental margin arc development at 635–570 Ma (main Avalonian magmatism) followed the breakup of Rodinia at ca. 755 Ma in the same way that the accretion of mature Cordilleran arcs to western North America and the development of the main phase of Cordilleran arc magmatism followed the Early Mesozoic breakup of Pangea. (3) In the absence of evidence for continental collision, the diachronous termination of subduction and its transition to an intracontinental wrench regime at 590–540 Ma is interpreted to record ridge–trench collision in the same way that North America's collision with the East Pacific Rise in the Oligocene led to the diachronous initiation of a transform margin. (4) The separation of Avalonia from Gondwana in the Early Ordovician resembles that brought about in Baja California by the Pliocene propagation of the East Pacific Rise into the continental margin. (5) The Late Ordovician–Early Silurian sinistral accretion of Avalonia to eastern Laurentia emulates the Cenozoic dispersal of Cordilleran terranes and may mimic the paths of future terranes transferred to the Pacific plate.This close similarity in tectonothermal histories suggests that a geodynamic coupling like that linking the evolution of the Cordillera with the assembly and breakup of Pangea, may have existed between Avalonia and the late Precambrian supercontinent Rodinia. Hence, the North American Cordillera is considered to provide an actualistic model for the evolution of Avalonia and other peri-Gondwanan terranes, the histories of which afford a proxy record of supercontinent assembly and breakup in the late Precambrian.     

塔里木盆地碎屑锆石年龄分布对前寒武纪基底的指示

应用碎屑锆石LA-ICP-MS U-Pb定年方法研究塔里木盆地前寒武纪基底与超大陆的关系, 对盆地内部不同地区井下11个碎屑岩样品进行锆石年代学分析。塔里木盆地南部与北部分别检测到早元古代、中元古代产生的物源, 结合周边造山带测年资料分析佐证了早中元古代塔里木南北块体演化有差异, 北部大量的中元古代早期年代数据可能预示塔北微块体存在与Columbia超大陆裂解时间相近的构造－热事件。南北塔里木在新元古代早期才发生碰撞拼合形成统一的基底与演化进程, 所有样品都检测到南华纪年龄数据证实塔里木板块及其周缘在此期发生大规模裂解事件, 南华纪大规模火成岩活动形成了盆地显生宙碎屑岩最主要的蚀源, 塔里木板块存在与Rodinia超大陆裂解时间相当的构造－热事件。碎屑锆石测年资料为研究塔里木板块与超大陆的关系提供了来自盆地内部的证据。     

Triassic breakup of Pangea in southern Mexico: Thermochronological evidence from the Tianguistengo formation

Southern Mexico is a key area for unraveling the tectonic evolution of North America because it contains the stratigraphic and structural record of the major tectonic events that shaped this continental mass, such as the breakup of Pangea and the growth of the North America Cordilleran Orogeny. However, multiple reactivations of faults and erosion of the stratigraphic record do not permit to adequately assess the timing of these tectonic events. Although most authors suggested that lithospheric extension and exhumation of continental blocks during Pangea breakup started in Mexico by Early Jurassic time, works published in the last decade provide an increasing number of thermo-tectonic evidence of an earlier phase of continental thinning. In this work, we present detrital apatite thermochronological and geochemical data (trace elements including rare earth elements) from fluvial deposits of the Tianguistengo formation, which is the oldest stratigraphic unit of the Otlaltepec Basin, a major basin in southern Mexico that has been linked to Pangea breakup. Our data show that at least a part of the Tianguistengo formation was derived from the adjacent Pennsylvanian–Cisuralian Totoltepec pluton. Apatite fission-track-based time–temperature modelling for unreset apatite populations suggests that the main exhumation of the Totoltepec pluton, which prompted the deposition of a part of the Tianguistengo formation, took place during Late Triassic time. Thus, our results suggest that Pangea breakup in southern Mexico started at least by Middle–Late Triassic time (240–230 Ma), as it is recorded in the Otlaltepec Basin.     

新疆且干布拉克超大型蛭石矿床的成因与成矿模式

新疆尉犁县且干布拉克超基性杂岩体位于塔里木北缘隆起带库鲁克塔格前寒武纪地块中西段,兴地塔格断裂带附近。该蛭石矿床是继南非Palabora、美国Libby和俄罗斯Kovdorsk蛭石矿之后的第4个超大型蛭石矿床。根据野外地质观察和室内薄片鉴定结果,结合该区已有的岩石地球化学和矿床学资料,并通过与国外同类型矿床进行详细对比,从含矿杂岩体的岩石组合、矿体发育特征和矿物共生组合等不同层面探讨了该杂岩体的演化过程和矿床成因,并建立了相关成岩成矿模型。结果表明,且干布拉克杂岩体是裂谷背景下,富集岩石圈地幔低程度部分熔融岩浆经岩浆分异和不混熔作用并以橄榄岩-黑云母透辉岩-碳酸岩等岩相依次侵入的产物,蛭石矿床中的金云母是岩浆晚期高温富碱质热液交代超基性岩的产物,云母类矿物在剥蚀到近地表后,在大气降水作用下发生表生风化最终形成蛭石矿床。矿床的形成过程复杂,经历了从地幔交代、超大陆裂解、岩浆分异、热液蚀变到表生风化作用等五大地质过程。这一模式的建立将为进一步寻找和深入研究该类矿床提供理论依据和实践指导。     

Conditioned duality between supercontinental 'assembly' and 'breakup' LIPs

A compilation of 178 more precise ages on 10 potential Large Igneous Provinces(LIPs) across southern Africa,is compared to Earth's supercontinental cycles,where 5 more prominent LIP-events all formed during the assembly of supercontinents,rather than during breakup.This temporal bias is confirmed by a focused review of field relationships,where these syn-assembly LIPs formed behind active continental arcs;whereas,the remaining postassembly-and likely breakup-related-LIPs never share such associations.Exploring the possibility of two radically different LIP-types,only the two younger breakup events(the Karoo LIP and Gannakouriep Suite) produced basalts with more enriched asthenospheric OIB-signatures;whereas,all assembly LIPs produced basalts with stronger lithospheric,as well as more or less primitive asthenospheric,signatures.A counterintuitive observation of Precambrian breakup LIPs outcropping as smaller fragments that are more peripherally located along craton margins,compared to assembly LIPs as well as the Phanerozoic Karoo breakup LIP,is explained by different preservation potentials during subsequent supercontinental cycles.Thus,further accentuating radical differences between(1) breakup LIPs,preferentially intruding along what evolves to become volcanic rifted margins that are more susceptible to deformation within subsequent orogens,and(2) assembly LIPs,typically emplaced along backarc rifts within more protected cratonic interiors.A conditioned duality is proposed,where assembly LIPs are primarily sustained by thermal blanketing(as well as local arc hydration and rifting) below assembling supercontinents and breakup LIPs more typically form above impinging mantle plumes.Such a duality is further related to an overall dynamic Earth model whereby predominantly supercontinent-orientated ocean lithospheric subduction establishes/revitalizes large low shear velocity provinces(LLSVPs) during assembly LIP-activity,and heating of such LLSVPs by the Earth's core subsequently leads to a derivation of mantle plumes during supercontinental breakup.     

柴达木盆地北缘新元古代-早古生代大洋的形成、发展和消亡

柴达木盆地北缘构造带是一条典型的早古生代造山带,是由陆壳深俯冲形成的高压/超高压变质带,产于其中的高压/超高压变质岩石原岩形成时代普遍大于750Ma,原岩的性质为陆壳属性,但柴北缘东段都兰沙柳河地区出露的含柯石英榴辉岩原岩的形成时代为516Ma,原岩的性质为洋壳属性,证实柴北缘局部地段还存在洋壳深俯冲,柴北缘地区可能记录了从大洋俯冲到大陆俯冲再到碰撞造山这一完整的演化历史。本文主要从岩石学、年代学、地球化学以及同位素地球化学等方面对柴北缘地区陆壳深俯冲前新元古代-早古生代大洋发展与演化的岩石记录进行了系统总结,认为柴北缘地区在700~850Ma时受Rodinia超大陆裂解事件的影响发生了裂解;535~700Ma时在裂解事件的基础上形成了一个新元古代-早古生代的大洋,沿柴北缘连续分布的岩石记录表明该洋盆可能在早古生代已具有一定的规模;460~535Ma时该洋壳发生了俯冲消减作用;450~460Ma期间洋盆闭合消失。这一认识对全面深入了解柴北缘高压/超高压变质带早古生代构造演化历史具有重要意义。     

华北陆块对Rodinia超大陆的响应及其特征

研究揭示华北陆块1300-1000Ma和800-650Ma都存在比较弱的岩浆-变质事件，它们可能对应于华南陆块的碰撞（四堡运动）和裂解事件。华北陆块的四堡期蛇绿混杂岩可能只见于新元古代秦岭造山带中。秦岭造山带北缘识别出了一些花岗质分清入体，它们具有碰撞或碰撞后花岗岩的特征。华北陆块北缘的火山沉积岩生活费不具有离散边界杂岩的特征，它们可能揭示了大陆边缘或者大陆伸展过程。华北陆块与800-650Ma事件相关的岩石主要为来自富集地幔的基性岩墙和来自陆内裂谷的沉积岩，它们很可能与Rodinia裂解有关。沉积学和古生物学特征表明元古宙华北陆块不同华南陆块，而与西伯利亚陆块相似。据此可以认为华北陆块是Rodinia超大陆的一部分，它位于超大陆的边缘，可以不与华南陆块紧邻，而与西伯利亚陆地较近。     

北非盆地叠加演化及其对油气地质条件的控制作用

以板块学说为理论依据,利用IHS和Tellus能源信息库,在对北非不同盆地群原型盆地恢复的基础上,系统分析了北非主要地质时期的盆地演化过程,从古板块位置、盆地类型、古海平面变化、古温度和古气候等方面,指出了盆地演化特征对北非油气地质条件形成的控制作用。志留纪和白垩纪北非被动大陆边缘和裂谷盆地的发育以及当时的海侵环境,控制了北非地区两套主要烃源岩的形成。而三叠纪北非地区低纬度板块位置和当时较高的气温以及海退环境,控制了北非最为重要的蒸发盐岩盖层的形成。不同盆地区盆地演化特征的差异,造成了其生、储和盖层发育的差异,也形成了北非西部盆地以古生代油气系统为主,而中东部盆地以中、新生代油气系统为主的油气分布格局,对于认识北非地区盆地的形成与演化及油气分布特征和开发潜力,具有一定的理论意义和实际价值。     

Paleoenvironment reconstructions and climate simulations of the Early Triassic: Impact of the water and sediment supply on the preservation of fluvial systems

Paleoenvironmental reconstructions and climatic modelling allow us to investigate the influence of water and sediment supply on the preservation of fluvial systems within a given geodynamic context. To simulate climate, we need global-scale paleoenvironmental and paleotopographic reconstructions. However, the present study only covers the West-Tethys domain, where sedimentological and stratigraphic data allow us to check climate simulation results against geological data. We focus our modelling on the Olenekian, with the aim of characterizing the impact of climate on fluvial sedimentation in the West-Tethys domain. The climatic simulations show that paleoclimates differ between Western Europe and North Africa. A more humid climate is simulated over North Africa, whereas a rather arid climate prevails over Western Europe. In Western Europe, the sediments are preserved for the most part in endoreic basins and the presence of rivers in an arid environment suggests that these rivers are mainly fed by precipitation falling on the North Africa Variscan Mountains. In North Africa, sedimentation is exclusively preserved in exoreic basins (coastal plain sediments). Consequently, the lack of preserved fluvial systems in endoreic basins in North Africa either could be due to a shortage of accommodation space in this area, or is linked to the climatic conditions that controlled the water and sediment supply.     

Les continents péri-atlantiques au crétacé supérieur: Migrations des faunes continentales et problèmes paléogéographiques

Terrestrial vertebrates offer possibilities of reconstructing the migrations by land-routes followed during the late Cretaceous on the peri-Atlantic continents (North America, South America, Europe, Africa). South America and Africa were not separated before the Aptian. Later, migrations could still have occurred between Africa and South America during the late Cretaceous by a land-route (probably discontinuous) situated on the Rio Grande Rise-Walvis Ridge barrier; it is not impossible that some amphibia used this route. In Laurasia, two provinces were largely separated during the early part of the late Cretaceous: Euramerica and Asiamerica in the terminology of Cox (1974), (that is, Europe plus eastern North America and Asia plus western North America). During the latest Cretaceous, western North America became connected with Euramerica, but probably separated from Asia. During the latest Cretaceous, a route, probably terrestrial, permitted important faunal exchanges between South America and Laurasia; this connection was situated in the Caribbean region, perhaps where Central America is today. Limited faunal exchange occurred between Euramerica and North Africa.     

Connection between South Mediterranean climate and North African atmospheric circulation during the last 50,000 yr BP North Atlantic cold events

High-resolution clay mineralogical analyses were performed on sediment deposited during the last 50,000 yr in the Alboran sea (ODP Site 976). The clay mineral record is compared with pollen assemblages and with annual precipitation (Pann) and mean temperatures of the coldest month (MTCO) reconstructed with the modern analog technique (MAT). Enhanced contribution of palygorskite, a typical wind-blown clay mineral, characterizes the North Atlantic cold climatic events. Coeval development of the semi-arid vegetation (Artemisia rich) associated with a drastic fall of reconstructed precipitations and temperatures, suggest cold and arid continental conditions in the West Mediterranean area during North Atlantic cold events. The clay mineral association, especially the palygorskite content and the illite-to-kaolinite ratio, indicate western Morocco as one of the major source of the clay-size fraction during the North Atlantic cold events. The maximum abundance of Artemisia associated with the presence of Argania pollen both indicate Morocco as the main origin for pollen during these cold periods. The comparison of these pollen and clay mineral-specific features allows us to pinpoint western Morocco as the dominant source of wind-blown particles during North Atlantic cold events. These specific mineralogical composition and palynological assemblages reveal enhanced aridity over North Africa and intensification of winds favouring dust erosion and transport from North Africa toward the Alboran Sea during the North Atlantic cold events. According to atmospheric models, such a meridian transport (1) likely results from the development of strong and stable anticyclonic conditions over the tropical Atlantic and North Africa, similar to today's summer meteorological configuration and (2) implies a northward position of the westerly winds during North Atlantic cold events. Finally the synoptic situation over the West Mediterranean during the North Atlantic cold events is compared with the North Atlantic Oscillation (NAO), suggesting that during the cold Atlantic events, weather regimes over Europe and North Africa may have been systematically shifted towards a positive NAO situation.     

志留纪全球古板块再造及岩相古地理*

依据古地磁方法,对志留纪全球古板块进行再造,并在此基础上叠加了更新的志留纪全球大地构造背景、洋流系统、气候带分布以及岩相古地理、烃源岩分布等要素,编制了志留纪全球古板块再造图、全球古地理图、全球岩相古地理及烃源岩分布图。志留纪全球板块构造格局最重要的特点是劳俄大陆的形成以及冈瓦纳大陆北缘的持续裂解事件。早—中志留世全球性的海侵事件导致各大板块周缘普遍发育陆表海,碳酸盐岩台地广泛分布于冈瓦纳大陆的周缘以及西伯利亚板块和劳俄大陆的大部分。志留纪较高的温度以及广阔的陆表海促进了海洋生物的进一步繁盛,为烃源岩的发育提供了丰富的母质;同时,上升流作用以及冈瓦纳大陆内部大型河流的搬运作用,导致在冈瓦纳大陆的西缘(北非和阿拉伯地区)发育有厚层的黑色页岩,其为志留系重要的烃源岩。