The two-stage opening of the western–central Mediterranean basins: a forward modeling test to a new evolutionary model

The Algero–Provençal and the Tyrrhenian extensional basins developed in two stages in a geodynamic setting characterized by the nearly N–S convergence between Africa and Eurasia. The spreading of the Provençal basin occurred in the early Miocene following a long period of rifting in the western Mediterranean area. A dramatic eastward shift of the active extensional deformation resulted in the Tortonian to Quaternary opening of the Tyrrhenian basin. In a companion paper, Carminati et al. propose that: a trench retreat process in a geodynamic setting locked by the continental collisions in the Alps and in the Betic chain is a viable mechanism for the late Oligocene–early Langhian opening of the western Mediterranean; a Langhian slab detachment episode along the north African margin is likely to have caused the end of the trench retreat along this part of the boundary determining the end of active expansion in the western Mediterranean and the beginning of active extension in the Tyrrhenian basin. The objective of the present paper is to quantitatively test this proposed scenario. We calculate, by means of a thin shell model, the effects of these plate boundary reorganizations on the European stress and strain field. We show that the two-stage opening of the western and central Mediterranean can be explained by the evolution proposed by Carminati et al. and that, in particular, the eastward shift of the active extension which produced the termination of the first opening stage and the beginning of the second is likely to have been triggered by the slab detachment episode along the north African margin.     

上地幔俯冲板块的动力学过程:数值模拟

大洋板块俯冲到地幔转换带,进而可形成不同的形态:板块可以停滞在660km不连续面,抑或穿过地幔转换带进入下地幔.这些不同的俯冲模式可进一步影响到海沟的运动.为更好地理解上地幔中俯冲板片的变形行为以及俯冲过程与海沟运动之间的关系,本文通过建立一系列高精度二维热-力学自由俯冲的数值模型,揭示了俯冲板块在上地幔中的变形方式及其与地幔转换带之间的相互作用过程.模拟结果显示,在俯冲板块与地幔转换带的相互作用过程中,其动力学过程可以分为以海沟后撤主导、海沟前进主导以及稳定型海沟等三种主要动力学类型.对于年龄较老,厚度较大的俯冲板块容易形成海沟后撤型俯冲,俯冲板块停滞在660km不连续面.相反,年龄较小,塑性强度较小的板块容易形成海沟前进型俯冲,俯冲板块穿越660km不连续面.     

Linking the Alps and Apennines subduction systems: New constraints revealed by high-resolution teleseismic tomography

We report a new model of the upper mantle structure beneath Italy obtained by means of P-wave teleseismic tomography. Besides the recent and remarkable development of the Italian Seismic Network, a high model resolution has been achieved improving the inversion method upon the ACH method used in previous investigations and picking high quality arrival times with the Multi-Channel Cross-Correlation technique. The finer details of our Vp model yield new insights into the heterogeneous structure of the Adria continental lithosphere involved in the collision between the Africa and Europe plates. A wide low Vp anomaly located in the northern Adria mantle, facing the Alpine high Vp slab, supports the idea that the Adria lithosphere has been hydrated and thinned during the Alpine subduction. We argue that this mantle softening may have played a key role in favoring the subsequent delamination of the Adria lithosphere in the northern Apennines. We hypothesize that delamination of continental lithosphere previously thinned in a back-arc setting may be considered a key process to favor subduction polarity reversal and recycling of continental material into the mantle circulation. Conversely, in the central-southern Apennines, the velocity structure is consistent with the existence of a deeper oceanic slab that flattens at the base of the upper mantle, in agreement with the widely accepted geodynamic evolution of the central Mediterranean by slab retreat and back-arc spreading. The oceanic slab is discontinuously detached from the surface plate, suggesting a different structure of the Adria lithosphere, which resists subduction instead of favoring delamination.     

The role of slab detachment processes in the opening of the western–central Mediterranean basins: some geological and geophysical evidence

A review of the geological and geophysical data from the central and western Mediterranean region and the present-day upper mantle structure derived from tomographic studies are utilized in order to define the Oligocene–Recent geodynamic evolution for the area. In line with previous work, we suggest that the Miocene–Quaternary opening of the western and central Mediterranean basins is the result of back-arc extension due to the roll back toward the southeast of a northwestward subducting African slab in a geodynamic setting pinned between the Alpine and Betic collisional zones. We find, however, that this general pattern is complicated by four different detachment events which occurred beneath the Alps (Early Oligocene), the Betic chain (Aquitanian), northern Africa (Langhian) and the Apennines (Late Miocene?–Pliocene). We show that each of these events determines a major tectonic reorganization within the European plate.     

Signatures of downgoing plate-buoyancy driven subduction in Cenozoic plate motions

The dynamics of plate tectonics are strongly related to those of subduction. To obtain a better understanding of the driving forces of subduction, we compare relations between Cenozoic subduction motions at major trenches with the trends expected for the simplest form of subduction. i.e., free subduction, driven solely by the buoyancy of the downgoing plate. In models with an Earth-like plate stiffness (corresponding to a plate–mantle viscosity contrast of 2–3 orders of magnitude), free plates subduct by a combination of downgoing plate motion and trench retreat, while the slab is draped and folded on top of the upper-lower mantle viscosity transition. In these models, the slabs sink according to their Stokes’ velocities. Observed downgoing-plate motion–plate-age trends are compatible with >80% of the Cenozoic slabs sinking according to their upper-mantle Stokes’ velocity, i.e., subducting-plate motion is largely driven by upper-mantle slab pull. Only in a few cases, do young plates move at velocities that require a higher driving force (possibly supplied by lower-mantle–slab induced flow). About 80% of the Cenozoic trenches retreat, with retreat accounting for about 10% of the total convergence. The few advancing trench sections are likely affected by regional factors. The low trench motions are likely encouraged by low asthenospheric drag (equivalent to that for effective asthenospheric viscosity 2–3 orders below the upper-mantle average), and low lithospheric strength (effective bending viscosity ～2 orders of magnitude above the upper-mantle average). Total Cenozoic trench motions are often very oblique to the direction of downgoing-plate motion (mean angle of 73°). This indicates that other forces than slab buoyancy exert the main control on upper-plate/trench motion. However, the component of trench retreat in the direction of downgoing plate motion (≈ slab pull) correlates with downgoing-plate motion, and this component of retreat generally does not exceed the amount expected for free buoyancy-driven subduction. High present-day slab dips (on average about 70°) are compatible with largely upper-mantle slab-pull driven subduction of relatively weak plates, where motion partitioning and slab geometry adjust to external constraints/forces on trench motion.     

西太平洋板块向我国东北地区深部俯冲的数值模拟

本文采用依赖温度的黏度结构以及考虑海洋板块和大陆板块厚度差异等特征,以太平洋板块向欧亚板块会聚速率作为板块速度的主要约束,通过变化海沟后撤速度模型,数值模拟西太平洋板块向中国东北的俯冲过程.结果表明,要产生类似于中国东北之下低角度的板片俯冲,海沟后撤是重要条件;而上下地幔黏度的较大差异是决定俯冲板片不穿透660 km相变面的决定因素;西太平洋板块向欧亚板块的俯冲应早于70 Ma B.P.,海沟后撤速度可能小于一些地质学家估计的45 mm/a, 而且可能是分阶段变化的;速度场表明运动学模型的反过程：大陆岩石圈之下物质的不断水平向东的流动和推挤可能成为海沟后撤的力源之一,地幔物质的这种东向流动可能与印度板块挤压碰撞欧亚板块有关,沿欧亚板块东缘的扩张构造可能是太平洋-欧亚板块运动和印度-欧亚板块运动的综合效应.     

Deep geodynamics of far field interconti- nental back-arc extension: Formation of Cenozoic volcanoes in northeastern China

Introduction Northeastem China has the most strong Cenozoic volcanism in China (Liu, 1999), where dis-tributes more than 500 Cenozoic volcanoes, including sleeping volcanoes of Tianchi Lake (Celes-tial Pond) of Changbai Mountain, and Wudalianchi (Five linked Lakes) (LIU, 1999). Vo lcano ofTianchi Lake of Changbai Mountain consists of basaltic rocks of shield-forming stage andtrachytes and pantellerites in cone-forming stage. It is suggested by study of REE, incompatibleelements a…     

Deep geodynamics of far field intercontinental back-arc extension: Formation of Cenozoic volcanoes in northeastern China

There are three cases of variation of trench location possible to occur during subduction: trench fixed, trench advancing, and trench retreating. Retreat of trench may lead to back-arc extension. The Pacific plate subducts at low angle beneath the Eurasia plate, tomographic results indicate that the subducted Pacific slab does not penetrate the 670 km discontinuity, instead, it is lying flat above the interface. The flattening occurred about 28 Ma ago. Geodynamic computation suggests: when the frontier of the subducted slab reaches the phase boundary of lower and upper mantle, it may be hindered and turn flat lying above the boundary, facilitates the retreat of trench and back-arc extension. Volcanism in northeastern China is likely a product of such retreat of subduction, far field back-arc extension, and melting due to reduce of pressure while mantle upwelling. Foundation item: National Natural Science Foundation of China (40234042 and 40174027).     

The influence of trench migration on slab penetration into the lower mantle

A two-dimensional numerical convection model in cartesian geometry is used to study the influence of trench migration on the ability of subducted slabs to penetrate an endothermic phase boundary at 660 km depth. The transient subduction history of an oceanic plate is modelled by imposing plate and trench motion at the surface. The viscosity depends on temperature and depth. A variety of styles of slab behaviour is found, depending predominantly on the trench velocity. When trench retreat is faster than 2–4 cm/a, the descending slab flattens above the phase boundary. At slower rates it penetrates straight into the lower mantle, although flattening in the transition zone may occur later, leading to a complex slab morphology. The slab can buckle, independent of whether it penetrates or not, especially when there is a localised increase in viscosity at the phase boundary. Flattened slabs are only temporarily arrested in the transition zone and sink ultimately into the lower mantle. The results offer a framework for understanding the variety in slab geometry revealed by seismic tomography.     

Seismic signature of the Alpine indentation,evidence from the Eastern Alps

The type of collision between the European and the Adriatic plates in the easternmost Alps is one of the most interesting questions regarding the Alpine evolution. Tectonic processes such as compression, escape and uplift are interconnected and shape this area. We can understand these ongoing processes better, if we look for signs of the deformation within the Earth's deep crust of the region. By collecting records from permanent and temporary seismic networks, we assemble a receiver function dataset, and analyze it with the aim of giving new insights on the structure of the lower crust and of the shallow portion of the upper mantle, which are inaccessible to direct observation. Imaging is accomplished by performing common conversion depth stacks along three profiles that crosscut the Eastern Alpine orogen, and allow isolating features consistently persistent in the area. The study shows a moderately flat Moho underlying a seismically anisotropic middle-lower crust from the Southern Alps to the Austroalpine nappes. The spatial progression of anisotropic axes reflects the orientation of the relative motion and of the stress field detected at the surface. These observations suggest that distributed deformation is due to the effect of the Alpine indentation. In the shallow upper mantle right below the Moho interface, a further anisotropic layer is recognized, extended from the Bohemian Massif to the Northern Calcareous Alps.     

Slab pull,mantle convection,and Pangaean assembly and dispersal

Two global-scale mantle convection cells presently exist on Earth, centred on upwelling zones in the South Pacific Ocean and northeast Africa: one cell (Panthalassan) contains only oceanic plates, the other (Pangaean) contains all the continental plates. They have remained fixed relative to one another for >400 Ma. A transverse (Rheic–Tethyian) subduction system splits the Pangaean cell. Poloidal plate motion in the oceanic cell reflects circumferential pull of Panthalassan slabs, but toroidal flow in the Pangaean cell, reflected by vortex-type motion of continents toward the Altaids of central-east Asia throughout the Phanerozoic, has resulted from the competing slab-pull forces of both cells. The combined slab-pull effects from both cells also controlled Pangaean assembly and dispersal. Assembly occurred during Palaeozoic clockwise toroidal motion in the Pangaean cell, when Gondwana was pulled into Pangaea by the NE-trending Rheic subduction zone, forming the Appalachian–Variscide–Altaid chain. Pangaean dispersal occurred when the Rheic trench re-aligned in the Jurassic to form the NW-trending Tethyside subduction system, which pulled east Gondwanan fragments in the opposite direction to form the Cimmerian–Himalayan–Alpine chain. This re-alignment also generated a new set of (Indian) mid-ocean ridge systems which dissected east Gondwana and facilitated breakup. 100–200-Myr-long Phanerozoic Wilson cycles reflect rifting and northerly migration of Gondwanan fragments across the Pangaean cell into the Rheic–Tethyian trench. Pangaean dispersal was amplified by retreat of the Panthalassan slab away from Europe and Africa, which generated mantle counterflow currents capable of pulling the Americas westward to create the Atlantic Ocean. Thermal blanketing beneath Pangaea and related hotspot activity were part of a complex feedback mechanism that established the breakup pattern, but slab retreat is considered to have been the main driving force. The size and longevity of the two cells, organised and maintained by long-lived slab-pull forces, favours deep mantle convection as the dominant circulation process during the Phanerozoic.     

Geodynamics of the Gibraltar Arc and the Alboran Sea region

Located at the Westernmost tip of the Mediterranean sea, the Gibraltar Arc is a very complex zone. The Betics in Spain and the Rif belt in Morocco surround the Alboran sea characterized by a thinned continental crust. The geodynamic evolution of this region results from the convergence of African and Iberian margins since the Late Cretaceous. It is controlled both by plate convergence and mantle dynamics, which significantly impact on morphology, sedimentary environments, tectonics, metamorphism and magmatism. We present here the contents of the special issue on the Gibraltar Arc and nearby regions, following the workshop organized at the University Abdelmalek Essaadi of Tetouan in Morocco from 27 to 28 October, 2011. The goal of this international workshop was to have an overview of the actual advance in research concerning the Rif and Betics chains, the Alboran basin, and their influence on the Iberian and African forelands.     

What triggered the early-to-mid Pleistocene tectonic transition across the entire eastern Mediterranean?

Subduction plays a fundamental role in plate tectonics and when interrupted it may trigger a series of geodynamic and sedimentary responses. Synchronous structural modifications recorded across the entire eastern Mediterranean region are dated to a relatively short period — early-to-mid Pleistocene. These deformations are documented within plates (e.g., Arabian, Sinai and African plates), along plate boundaries (e.g., Dead Sea and North Anatolian faults and Cyprus Arc), and in the Mediterranean basin. During the same period the northward subduction of the Sinai plate was interrupted when the Eratosthenes Seamount–Cyprus Arc collision initiated. Subduction–collision processes of the eastern Mediterranean serve as a unique modern analogue for similar settings worldwide. Understanding their association with accompanying neo-tectonic processes is therefore predominantly important. By fostering a detailed and comprehensive approach this research provides a coherent tectonic picture for the eastern Mediterranean early-to-mid Pleistocene tectonic transition in order to explore its triggering mechanisms. Since the Neogene convergence across the eastern Mediterranean was accompanied by Eurasian indentation by Arabia northward motion, westwards Anatolia escape and southwards Aegean propagation. This semi counterclockwise plate motion was temporarily interrupted by the incipient Seamount–Arc collision which is suggested here as a trigger of the early-to-mid Pleistocene tectonic transition.     

Strain segmentation and lateral membrane deformation rate of the subducted Ryukyu slab

Abstract Focal mechanisms of intermediate-depth earthquakes within the subducted Ryukyu slab indicate a systematic pattern of down-dip extension in the northern part under Kyushu. These mechanisms switch rapidly around the Tokara channel to down-dip compression in the southern part toward Taiwan. This intriguing pattern of strain segmentation, together with the differences between the slab geometry of the northern and southern parts, has raised the question of whether stress segmentation, as defined possibly by a tear fault, might exist in the slab. However the Ryukyu trench has a concave oceanward shape in the northern segment while it is convex in the southern oceanward part toward Taiwan. The inflection zone is located around the Tokara channel. The concept of Gaussian curvature of a curved surface suggests that the along-arc variation of the geometric configuration of a subducted slab is related to the shape of the trench. This is in order to accommodate the lateral membrane deformation of the slab as the oceanic lithosphere subducts from a spherical shell to the geometry delineated by the Wadati-Benioff zone. The membrane deformation regime of the subducted Ryukyu slab and its relation with the trench geometry was examined by assuming that the subduction be modelled by the flow field of a thin viscous sheet. A projection operator was utilized to compute the membrane strain-rate tensor of an arbitrary non-Euclidean surface. Numerical experiments indicated that the northern segment of the slab was dominated by lateral compression and down-dip extension and the southern part by lateral extension and down-dip compression. This transition is sharply located near the Tokara channel. These patterns were compatible with what had been observed from studies of focal mechanisms, suggesting that the strain segmentation might be controlled, at least in part, by the lateral membrane deformation within the slab due to the trench shape in this subduction zone. The slab geometry was predicted by minimizing the integrated total dissipation power; this revealed distinct features that were consistent with observations. This implies that the slab geometry may also be affected by the membrane deformation in a systematic fashion.     

Early-stage rifting of the Southern Tyrrhenian region: The Calabria–Sardinia breakup

The Southern Tyrrhenian Sea is an extensional basins linked to the Neogene evolution of the Calabria subduction zone located in the western Mediterranean realm where controversial kinematic and geodynamical models have been proposed. Our study provides a key to unravel timing and mode of extension of the upper plate and the breakup of Calabria from Sardinia. By combining original stratigraphic analysis of wells and seismic profiles off Calabria with a stratigraphic correlation to onshore outcrops, we re-assess the tectonic evolution that controlled the sedimentation and basement deformation of the Southern Tyrrhenian basin during Serravallian–Tortonian times. We document the tectono-stratigraphic evolution of adjacent extensional basins characterized by 3rd order depositional sequences (Ser1, Tor1 and Tor2) and different modes of extension, subsidence and opposite dipping faults. Episodic basin development is recorded by a coarsening-up and fining-up trend of the sedimentary succession and by tectonically enhanced unconformities that reflect three episodes of fault activity. We reconstruct Serravallian–Tortonian paleogeographic maps and propose a block faulting model for the evolution of the Sardinia–Calabria area. Sardinia was disconnected from Calabria through N–S normal faults forming Tyrrhenian extensional basins that formed contemporaneously to the E–W opening of the Algerian basin. Unlike published Serravallian–Tortonian reconstructions of the western Mediterranean realm, our results support a geodynamic model characterized by rapid trench retreat, trench-normal extension in the entire overriding plate and very weak coupling between plates.     

Upper Pleistocene uplifted shorelines as tracers of (local rather than global) subduction dynamics

Past studies have shown that high coastal uplift rates are restricted to active areas, especially in a subduction context. The origin of coastal uplift in subduction zones, however, has not yet been globally investigated. Quaternary shorelines correlated to the last interglacial maximum (MIS 5e) were defined as a global tectonic benchmark (Pedoja et al., 2011). In order to investigate the relationships between the vertical motion and the subduction dynamic parameters, we cross-linked this coastal uplift database with the “geodynamical” databases from Heuret (2005), Conrad and Husson (2009) and Müller et al. (2008). Our statistical study shows that: (1) the most intuitive parameters one can think responsible for coastal uplift (e.g., subduction obliquity, trench motion, oceanic crust age, interplate friction and force, convergence variation, dynamic topography, overriding and subducted plate velocity) are not related with the uplift (and its magnitude); (2) the only intuitive parameter is the distance to the trench which shows in specific areas a decrease from the trench up to a distance of ∼300 km; (3) the slab dip (especially the deep slab dip), the position along the trench and the overriding plate tectonic regime are correlated with the coastal uplift, probably reflecting transient changes in subduction parameters. Finally we conclude that the first order parameter explaining coastal uplift is small-scale heterogeneities of the subducting plate, as for instance subducting aseismic ridges. The influence of large-scale geodynamic setting of subduction zones is secondary.     

Synchronous uplift of the lower crust of the Ivrea Zone and of Southern Calabria and its possible consequences for the Hercynian orogeny in Southern Europe

Along the border of the Adriatic microplate, pre-Alpine granulite-facies rocks from the deepest crust are outcropping at only two places: in the Ivrea Zone of the Southern Alps and in Southern Calabria. In these two areas the main features of the present crustal structures, i.e. overlapping of large continental crustal and upper mantle segments, are interpreted as resulting from their Hercynian geodynamic evolutions.The tilted, nearly complete crustal sections in both areas display very similar lithological sequences and experienced a common geological evolution, as deduced from petrological and radiometric dates. At the end of Hercynian time (～295 m.y.), the Ivrea body and the lower crustal rocks of Southern Calabria were contemporaneously sheared off from the upper mantle and uplifted into intermediate crustal levels, where they slowly cooled during Mesozoic time. The tectonic uplift was accompanied by granitoid plutonism and andesitic to rhyolitic volcanism, which continued after the Hercynian uplift.Considering the presently similar crustal structures and the Upper Carboniferous and Permian geological evolutions along the whole Adriatic plate boundary, the Ivrea Zone and Southern Calabria are used to resolve the pre-Alpine history of the boundary zone between the Adriatic and the Central European block: the uplift of the lower crustal/upper mantle flakes of the Adriatic block was due to flat overthrusting of these flakes on the continental crust of “Central Europe”. The material of the Central European crust underthrust (subducted) thereby melted during the re-equilibration of the geotherms which had been disturbed by the subduction process; this led to an extensive calc-alkaline plutonism and volcanism of crustal origin along the Adria boundary. In this boundary region, the overlying uppermost crustal levels (“Schiefergebirgsstockwerk”) were synchronously folded (“Asturian phase”) in response to the overlapping of the deeper crustal levels. Subsequently to the orogeny, the mountain chain was eroded and molasse basins developed on the overthrust Adriatic crustal segment during the Lower Permian.In this model, the granulite-facies flakes of the Ivrea Zone and of Southern Calabria are interpreted as pre-Hercynian lower crustal segments which were thrust into the middle crust during the Hercynian orogeny, thus giving rise to wave velocity inversions in the crust. Further, it is proposed that similar geodynamic processes have played a role in the genesis of the Conrad discontinuity which is present in many parts of the Hercynian fold belt. But only in the Ivrea Zone and in Southern Calabria the crustal discontinuities formed in Hercynian time were uplifted to the surface as a result of Alpine reactivation of the Adriatic boundary zone and due to their special positions in the bends of the Alpine-Apennine-Maghrebide mountain system.According to the present knowledge of the Carboniferous paleogeography and of the orogenic evolution on both sides of the Adria sufure zone, this fault zone was located within the European continent. Its role during the Hercynian orogeny is discussed envisaging two possibilities: an A-subduction zone or a subfluence zone (in the sense of Behr and Weber).     

扬子褶皱带侏罗纪砂岩古地磁及其褶皱带弧形弯曲的成因

为了更好地认识上扬子褶皱带和中扬子褶皱带走向差异的机制,我们对中、上扬子褶皱带过渡的关键地区重庆市万州和云阳两个地区的中、晚侏罗世砂岩进行了古地磁研究.逐步热退磁分离出两个组分,低温组分（LTC）在所有样品中均分离出来,为现代地磁场的重磁化;中侏罗世样品和万州地区的晚侏罗世样品分离出来的高温组分（HTC）也为现代地磁场的重磁化.云阳地区晚侏罗世样品分离出来的高温组分通过逐步展平褶皱检验显示：在褶皱展平至33.8%时,精度参数达到最大,相应的古地磁方向为D=19.1°,I=48.9°（α₉₅= 6.3°）,古地磁极为73.5°N,198.2°E（dp=5.5°, dm=8.3°）,与白垩纪参考古地磁极对比,此高温组分揭示云阳地区在褶皱变形的后期经历了7.7°±6.1°的顺时针旋转.结合前人的数据,我们认为中扬子褶皱带普遍存在弯山构造（orocline）,这可能与华北板块向华南板块的挤入作用有关;但是中、上扬子褶皱带过渡地区的弧形弯曲总体上不是由弯山构造形成的,很可能是在太平洋板块向北西方向俯冲的宏观板块构造背景下的应变分异作用形成的.     

Restoring earth surface processes through landform design. A 13‐year monitoring of a geomorphic reclamation model for quarries on slopes

The application of geomorphic principles to land reclamation after surface mining has been reported in the literature since the mid‐1990s, mostly from Australia, Canada and the USA. This paper discusses the reclamation problems of contour mining and quarries on slopes, where steep gradients are prone to both mass movement and water erosion. To address these problems simultaneously, a geomorphic model for reclaiming surface mined slopes is described. Called the ‘highwall–trench–concave slope’ model, it was first applied in the 1995 reclamation of a quarry on a slope (La Revilla) in Central Spain. The geomorphic model does not reproduce the original topography, but has two very different sectors and objectives: (i) the highwall–trench sector allows the former quarry face to evolve naturally by erosion, accommodating fallen debris by means of a trench constructed at the toe of the highwall; (ii) the concave‐slope base sector, mimicking the landforms of the surrounding undisturbed landscape, promotes soil formation and the establishment of self‐sustaining, functional ecosystems in the area protected from sedimentation by the trench. The model improves upon simple topographic reconstruction, because it rebuilds the surficial geology architecture and facilitates re‐establishment of equilibrium slopes through the management and control of geomorphic processes. Thirteen years of monitoring of the geomorphic and edaphic evolution of La Revilla reclaimed quarry confirms that the area is functioning as intended: the highwall is backwasting and material is accumulating at the trench, permitting the recovery of soils and vegetation on the concave slope. However, the trench is filling faster than planned, which may lead to run‐off and sedimentation on the concave slope once the trench is full. The lesson learned for other scenarios is that the model works well in a two‐dimensional scheme, but requires a three‐dimensional drainage management, breaking the reclaimed area into several watersheds with stream channels. Copyright © 2010 John Wiley & Sons, Ltd.     

欧亚东边缘的双向板块汇聚及其对大陆的影响

自3 Ma至现今,在欧亚东缘太平洋、菲律宾海板块以较大速率朝NWW方向运动,并沿海沟向欧亚大陆俯冲;同时欧亚板块以较小速率朝SEE方向移动,构成双方向的板块汇聚格局.沿日本岛弧东侧,海洋板片以较小的倾角插入欧亚大陆下面,在浅部产生的挤压变形扩展到日本海东边缘.琉球岛弧的中、北部,菲律宾海俯冲板片的倾角较大,其西南段由NE向转变为EW向,正经历活动的海沟后退与弧后扩张.台湾是3种板块汇聚的交点:欧亚沿马尼拉海沟向东俯冲,吕宋弧与台湾碰撞,使台湾岛陆壳东西向缩短与隆升,形成年轻的造山带,菲律宾海板块沿琉球海沟的西南段向北俯冲到欧亚下面.位于南海与菲律宾海之间的菲律宾群岛是宽的变形过渡带,两侧被欧亚向东、菲律宾海向西俯冲夹击,中间是大型左旋走滑断层.总体上,现今时期的太平洋、菲律宾海板块的西向俯冲运动所产生的变形主要分布在俯冲板片内部及岛弧,未扩散到弧后地区,可能这种俯冲运动产生的水平应力较小,不能阻挡欧亚大陆的向东移动,对大陆内部的现今构造没有明显的影响.