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B. Fügenschuh A. Loprieno S. Ceriani S. M. Schmid 《International Journal of Earth Sciences》1999,88(2):201-218
Valais and Subbriançonnais units of the Western Alps of Savoie underwent a common structural evolution, postdating peak pressure conditions associated with high-pressure metamorphism of internal parts of the Valais units. The first two phases, due to roughly north/south-directed shortening, are interpreted to be related to a NNE/SSW-striking corridor of sinistral transpression between the internal Western Alps and the European foreland. Both phases led to nappe formation, isoclinal folding and north–south elongation. Only the third phase of deformation is related to WNW-directed orogen-perpendicular shortening, thus far regarded as the predominant thrusting direction in the Western Alps. Late (post 5?Ma) normal faulting, evidenced by fission-track dating, reactivated the Houiller Front in the north and the Penninic Front in the south. Kinematics of movement, observed along the present-day Houiller Front and Penninic Front, change from north to south. In the north the Houiller Front indicates post-D3 normal faulting while the Penninic Front preserved WNW-directed thrusting (D3). In the south the Houiller Front preserves syn-D2 north-directed thrusting, whereas the Penninic Front is partly reactivated by post-D3 normal faulting. Our observations clearly favor tectonic reasons for the disappearance of the Valais units south of Moûtiers in present-day map view. 相似文献
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Tectonic progradation and plate tectonic evolution of the Alps 总被引：2，自引：0，他引：2
W. Frisch 《Tectonophysics》1979,60(3-4):121-139
Rifting and spreading, trench formation, flysch deposition, subduction and nappe formation prograde from internal to external parts of the Alpine orogen. The progradation is a characteristic feature of the evolution of the Alps. A plate tectonics model based on this cognition is presented and an attempt is made to integrate the plate movements of the Alpine region during the Mesozoic and Cenozoic into the plate pattern of the Western Mediterranean.
Important events in the evolution of the Alps are the successive opening and closing of the Piedmont (South Penninic) and Valais (North Penninic) oceans, and the two continental collisions related to this. The southward drift of the Briançonian plate in the Cretaceous closes the Piedmont and opens the Valais ocean. The evolution of these oceans is related to the plate movements in the North Atlantic. The second continental collision is followed by the formation of an exogeosyncline, the molasse foredeep.
Prograding orogens like the Alps are most likely to evolve in an originally continental environment by rifting. Retrograding orogens, however, indicate an originally oceanic environment with well-developed magmatic arcs and back-arc basins. 相似文献
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We present a map that correlates tectonic units between Alps and western Turkey accompanied by a text providing access to literature data, explaining the concepts used for defining the mapped tectonic units, and first-order paleogeographic inferences. Along-strike similarities and differences of the Alpine-Eastern Mediterranean orogenic system are discussed. The map allows (1) for superimposing additional information, such as e.g., post-tectonic sedimentary basins, manifestations of magmatic activity, onto a coherent tectonic framework and (2) for outlining the major features of the Alpine-Eastern Mediterranean orogen. Dinarides-Hellenides, Anatolides and Taurides are orogens of opposite subduction polarity and direction of major transport with respect to Alps and Carpathians, and polarity switches across the Mid-Hungarian fault zone. The Dinarides-Hellenides-Taurides (and Apennines) consist of nappes detached from the Greater Adriatic continental margin during Cretaceous and Cenozoic orogeny. Internal units form composite nappes that passively carry ophiolites obducted in the latest Jurassic–earliest Cretaceous or during the Late Cretaceous on top of the Greater Adriatic margin successions. The ophiolites on top of composite nappes do not represent oceanic sutures zones, but root in the suture zones of Neotethys that formed after obduction. Suturing between Greater Adria and the northern and eastern Neotethys margin occupied by the Tisza and Dacia mega-units and the Pontides occurred in the latest Cretaceous along the Sava-İzmir-Ankara-Erzincan suture zones. The Rhodopian orogen is interpreted as a deep-crustal nappe stack formed in tandem with the Carpatho-Balkanides fold-thrust belt, now exposed in a giant core complex exhumed in late Eocene to Miocene times from below the Carpatho-Balkan orogen and the Circum-Rhodope unit. Its tectonic position is similar to that of the Sakarya unit of the Pontides. We infer that the Rhodope nappe stack formed due to north-directed thrusting. Both Rhodopes and Pontides are suspected to preserve the westernmost relics of the suture zone of Paleotethys. 相似文献
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Frederik Kirst 《Swiss Journal of Geoscience》2017,110(2):503-521
This study assesses the significance, geometry, and kinematics of greenschist-facies deformation along the Dent Blanche Basal Thrust (DBBT), a major tectonic contact in the Internal Western Alps of Switzerland and Italy. The DBBT separates continental units of the Dent Blanche nappe, the structurally highest unit in the Western Alps, from underlying Piemont-Ligurian ophiolites. Mylonites and deformation structures along the contact provide a record of its retrograde greenschist-facies evolution after earlier high-pressure metamorphism. A first phase of foreland-directed, reverse-sense, top-(N)W shearing (D1) occurred between ca. 43 and 39 Ma, related to exhumation of the Dent Blanche nappe from high-pressure conditions. It led to the formation of mylonitic fabrics under high- to medium-grade greenschist-facies conditions along the entire DBBT. A phase of ductile normal-sense top-SE shearing (D2) at ca. 38–37 Ma was mainly localized within underlying ophiolitic units and only partly affected the DBBT. Another phase of ductile deformation (D3) under medium- to low-grade greenschist-facies conditions at ca. 36–35 Ma occurred in response to underthrusting of European continental margin units and resulted in the updoming of the nappe stack. Especially the southeastern DBBT was characterized by bulk top-NW shearing, partly conjugate top-NW/top-SE shearing, and resulting orogen-perpendicular crustal extension. Subsequently, the DBBT was affected by a phase of orogen-perpendicular shortening (D4) and formation of folds and crenulations at ca. 34–33 Ma due to increasing compressional tectonics. Finally, a phase of semi-ductile to brittle normal-sense top-NW and conjugate shearing (D5) from ca. 32 Ma onwards particularly affected the southeastern segment and indicates exhumation of the DBBT through the ductile–brittle transition. This was followed by brittle NW–SE extensional deformation. This study suggests that the DBBT experienced a polyphase deformation and reactivation history under decreasing greenschist-facies metamorphic conditions during which different segments of this major shear zone were variably affected. 相似文献
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The classical concept of the nappe structure of the central Northern Calcareous Alps (NCA) is in contradiction with modern stratigraphic, structural, metamorphic and geochronological data. We first perform a palinspastic restoration for the time before Miocene lateral tectonic extrusion, which shows good continuity of structures, facies and diagenetic/metamorphic zones. We present a new nappe concept, in which the Tirolic unit practically takes the whole area of the central NCA and is divided into three subunits (nappes): Lower and Upper Tirolic subunit, separated by the Upper Jurassic Trattberg Thrust, and the metamorphic Ultra-Tirolic unit. The Hallstatt (Iuvavic) nappe(s) formed the highest unit, but were completely destroyed by erosion after nappe stacking. Remnants of the Hallstatt nappes are only represented by components of up to 1 km in size in Middle/Upper Jurassic radiolaritic wildflysch sediments ("Hallstatt Mélange" belonging to the Tirolic unit). Destruction of the continental margin started in Middle to Upper Jurassic time and prograded from the oceanic side towards the shelf. The original substratum of the external nappes (Bavaric units) of the NCA was largely the Austroalpine crystalline basement, of the internal nappes (Tirolic units) the weakly metamorphosed Palaeozoic sequences (Greywacke Zone and equivalents). Eocene movements caused limited internal deformation in the Tirolic unit. 相似文献
9.
Jürgen F. von Raumer François Bussy Gérard M. Stampfli 《Comptes Rendus Geoscience》2009,341(2-3):239-252
In the general discussion on the Variscan evolution of central Europe the pre-Mesozoic basement of the Alps is, in many cases, only included with hesitation. Relatively well-preserved from Alpine metamorphism, the Alpine External massifs can serve as an excellent example of evolution of the Variscan basement, including the earliest Gondwana-derived microcontinents with Cadomian relics. Testifying to the evolution at the Gondwana margin, at least since the Cambrian, such pieces took part in the birth of the Rheic Ocean. After the separation of Avalonia, the remaining Gondwana border was continuously transformed through crustal extension with contemporaneous separation of continental blocks composing future Pangea, but the opening of Palaeotethys had only a reduced significance since the Devonian. The Variscan evolution in the External domain is characterised by an early HP-evolution with subsequent granulitic decompression melts. During Visean crustal shortening, the areas of future formation of migmatites and intrusion of monzodioritic magmas in a general strike–slip regime, were probably in a lower plate situation, whereas the so called monometamorphic areas may have been in an upper plate position of the nappe pile. During the Latest Carboniferous, the emplacement of the youngest granites was associated with the strike–slip faulting and crustal extension at lower crustal levels, whereas, at the surface, detrital sediments accumulated in intramontaneous transtensional basins on a strongly eroded surface. 相似文献
10.
Albrecht Steck Franco Della Torre Franz Keller Hans-Rudolf Pfeifer Johannes Hunziker Henri Masson 《Swiss Journal of Geoscience》2013,106(3):427-450
The Lepontine dome represents a unique region in the arc of the Central and Western Alps, where complex fold structures of upper amphibolite facies grade of the deepest stage of the orogenic belt are exposed in a tectonic half-window. The NW-verging Mont Blanc, Aar und Gotthard basement folds and the Lower Penninic gneiss nappes of the Central Alps were formed by ductile detachment of the upper European crust during its Late Eocene–Early Oligocene SE-directed underthrust below the upper Penninic and Austroalpine thrusts and the Adriatic plate. Four underthrust zones are distinguished in the NW-verging stack of Alpine fold nappes and thrusts: the Canavese, Piemont, Valais and Adula zones. Up to three schistosities S1–S3, folds F1–F3 and a stretching lineation XI with top-to-NW shear indicators were developed in the F1–F3 fold nappes. Spectacular F4 transverse folds, the SW-verging Verzasca, Maggia, Ziccher, Alpe Bosa and Wandfluhhorn anticlines and synclines overprint the Alpine nappe stack. Their formation under amphibolite facies grade was related to late ductile folding of the southern nappe roots during dextral displacement of the Adriatic indenter. The transverse folding F4 was followed since 30 Ma by the pull-apart exhumation and erosion of the Lepontine dome. This occurred coevally with the formation of the dextral ductile Simplon shear zone, the S-verging backfolding F5 and the formation of the southern steep belt. Exhumation continued after 18 Ma with movement on the brittle Rhone-Simplon detachment, accompanied by the N-, NW- and W-directed Helvetic and Dauphiné thrusts. The dextral shear is dated by the 29–25 Ma crustal-derived aplite and pegmatite intrusions in the southern steep belt. The cooling by uplift and erosion of the Tertiary migmatites of the Bellinzona region occurred between 22 and 18 Ma followed by the exhumation of the Toce dome on the brittle Rhone–Simplon fault since 18 Ma. 相似文献
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ABSTRACT Nappe refolding, back-thrusting and normal faulting frequently cause severe late-stage overprinting of the architecture of an orogen. A combined investigation of nappe stack polarity, kinematics of shearing and metamorphic gradients in the Western Alps develops criteria for distinguishing between these three modes of late-stage deformation. This distinction is a prerequisite for any retro-deformation necessary for understanding the main tectonic and metamorphic evolution of collisional orogens. In the case of the Western Alps overprint was by mega-scale nappe refolding in the Oligocene. This implies exhumation of the HP-rocks prior to postnappe folding, i.e. during nappe stacking and by foreland-directed ascent within a subduction channel. 相似文献
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The volcanosedimentary units of Late Mesozoic-Tertiary age that outcrop in the Southeast Anatolian orogenic belt are commonly
referred to as the Maden complex. There is a long-lasting controversy over its definition, age, stratigraphic and structural
position, and the origin, and thus, the orogenic evolution. To solve this problem, large strips across the Southeast Anatolian
orogenic belt have been studied extensively, and different rock groups which were regarded previously as the Maden unit have
been differentiated. Their major characteristics and differences have been identified. The Maden unit sensu stricto is here
redefined as a volcanosedimentary succession of Middle Eocene age representing a short-lived back-arc basin which reached
the stage of an embryonic ocean. Presently, the Maden group occurs mainly within the lower nappe stack of the nappe zone of
the Southeast Anatolian orogen. It rests stratigraphically on an amalgamated nappe package consisting of the different metamorphic
tectonic units and, in turn, is overlain tectonically by the upper nappe units. 相似文献
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《Geodinamica Acta》1999,12(2):97-111
In the southwestern part of the Belledonne Massif (External Crystalline Massifs, French Alps), superimposition of three distinct crustal units has been interpreted as the consequence of Late Devonian-Early Carboniferous thrusting toward the ENE under typical collisional metamorphic conditions (9-7 kbar, 600–650 °C). Structural relationships between the different units and the kinematic analysis of microstructures suggest that ductile extensional tectonics with a sinistral component towards the southwest is responsible for the late structure of this domain. Extensional tectonics are responsible for the exhumation of the deep level of the nappe pile (Allemont unit) that recorded an earlier HP-LT tectonometamorphic evolution ( 10 ± 1 kbar, 550 ± 50 °C and for the syn-kinematic adiabatic decompression path recorded in the two lowest units (Livet and Allemont). Such isothermal decompression may have been related to rapid thinning (~ 3mm y−1) and led to local decompressional melting at the base of the nappe pile. The thinning is best explained by extensional tectonics processes affecting the previously thickened Variscan crust during the Upper Carboniferous prior to its restoration to normal thickness. 相似文献
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The Teggiolo zone is the sedimentary cover of the Antigorio nappe, one of the lowest tectonic units of the Penninic Central
Alps. Detailed mapping, stratigraphic and structural analyses, and comparisons with less metamorphic series in several well-studied
domains of the Alps, provide a new stratigraphic interpretation. The Teggiolo zone is comprised of several sedimentary cycles,
separated by erosive surfaces and large stratigraphic gaps, which cover the time span from Triassic to Eocene. At Mid-Jurassic
times it appears as an uplifted, partially emergent block, marking the southern limit of the main Helvetic basin (the Limiting
South-Helvetic Rise LSHR). The main mass of the Teggiolo calcschists, whose base truncates the Triassic–Jurassic cycles and
can erode the Antigorio basement, consists of fine-grained clastic sediments analogous to the deep-water flyschoid deposits
of Late Cretaceous to Eocene age in the North-Penninic (or Valais s.l.) basins. Thus the Antigorio-Teggiolo domain occupies a crucial paleogeographic position, on the boundary between the Helvetic
and Penninic realms: from Triassic to Early Cretaceous its affinity is with the Helvetic; at the end of Cretaceous it is incorporated
into the North-Penninic basins. An unexpected result is the discovery of the important role played by complex formations of
wildflysch type at the top of the Teggiolo zone. They contain blocks of various sizes. According to their nature, three different
associations are distinguished that have specific vertical and lateral distributions. These blocks give clues to the existence
of territories that have disappeared from the present-day level of observation and impose constraints on the kinematics of
early folding and embryonic nappe emplacement. Tectonics produced several phases of superimposed folds and schistosities,
more in the metasediments than in the gneissic basement. Older deformations that predate the amplification of the frontal
hinge of the nappe generated the dominant schistosity and the km-wide Vanzèla isoclinal fold. 相似文献
15.
The Penninic oceanic sequence of the Glockner nappe and the foot-wall Penninic continental margin sequences exposed within the Tauern Window (eastern Alps) have been investigated in detail. Field data as well as structural and petrological data have been combined with data from the literature in order to constrain the geodynamic evolution of these units. Volcanic and sedimentary sequences document the evolution from a stable continent that was formed subsequent to the Variscan orogeny, to its disintegration associated with subsidence and rifting in the Triassic and Jurassic, the formation of the Glockner oceanic basin and its consumption during the Upper Cretaceous and the Paleogene. These units are incorporated into a nappe stack that was formed during the collision between a Penninic Zentralgneis block in the north and a southern Austroalpine block. The Venediger nappe and the Storz nappe are characterized by metamorphic Jurassic shelf deposits (Hochstegen group) and Cretaceous flysch sediments (Kaserer and Murtörl groups), the Eclogite Zone and the Rote Wand–Modereck nappe comprise Permian to Triassic clastic sequences (Wustkogel quartzite) and remnants of platform carbonates (Seidlwinkl group) as well as Jurassic volcanoclastic material and rift sediments (Brennkogel facies), covered by Cretaceous flyschoid sequences. Nappe stacking was contemporaneous to and postdated subduction-related (high-pressure) eclogite and blueschist facies metamorphism. Emplacement of the eclogite-bearing units of the Eclogite zone and the Glockner nappe onto Penninic continental units (Zentralgneis block) occurred subsequent to eclogite facies metamorphism. The Eclogite zone, a former extended continental margin, was subsequently overridden by a pile of basement-cover nappes (Rote Wand–Modereck nappe) along a ductile out-of-sequence thrust. Low-angle normal faults that have developed during the Jurassic extensional phase might have been inverted during nappe emplacement. 相似文献
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AbstractIn the southwestern part of the Belledonne Massif (External Crystalline Massifs, French Alps), superimposition of three distinct crustal units has been interpreted as the consequence of Late Devonian-Early Carboniferous thrusting toward the ENE under typical collisional metamorphic conditions (9–7 kbar, 600–650 °C). Structural relationships between the different units and the kinematic analysis of microstructures suggest that ductile extensional tectonics with a sinistral component towards the southwest is responsible for the late structure of this domain. Extensional tectonics are responsible for the exhumation of the deep level of the nappe pile (Allemont unit) that recorded an earlier HP-LT tectonometamorphic evolution (10 ± 1 kbar, 550 ± 50 °C) and for the syn-kinematic adiabatic decompression path recorded in the two lowest units (Livet and Allemont). Such isothermal decompression may have been related to rapid thinning (~ 3mm y?1) and led to local decompressional melting at the base of the nappe pile. The thinning is best explained by extensional tectonics processes affecting the previously thickened Variscan crust during the Upper Carboniferous prior to its restoration to normal thickness. © Elsevier, Paris 相似文献
17.
Briançonnais units are squeezed between two Mesozoic eclogitic belts (Piemont-Ligurian ocean and Valaisan ocean) along the ECORS-CROP seismic line in the Italian-French Western Alps (France, Italy). The metamorphic evolution of this area plays a key role for understanding the evolution of the Western Alps and is discussed on the basis of detailed petrographic investigations carried out on weathered sediments issued from the erosion of the Hercynian belt, especially on lower Permian to Mesozoic sediments. In the Zone Houillère, as well in the Permo-Triassic cover of the Briançonnais basement, the index metamorphic mineral assemblage is mainly composed of white micas with varying chemical composition, chloritoid and garnet. This same assemblage occurs within different lithologies (metaarkose, metapelite, metasandstone). Consequently, equilibrium phase diagrams were computed for different whole rock compositions using DOMINO software. The results of the P-T investigations clearly show that each unit underwent a different sequence of metamorphic reactions. An increase in metamorphic grade from greenschist facies conditions in the Northwest (Zone Houillère) to the transition between blueschist and eclogite facies conditions in the Southeast (Internal Briançonnais) is observed. A major discontinuity in metamorphic grade is located at the contact between Zone Houillère and Ruitor unit, as documented by a pressure gap of ~ 7 kbar. In general, the observed metamorphic field gradient is inverted and is interpreted to represent different depths of burial during subduction, which correlates with the paleogeographic position of the different units. 相似文献
18.
The European Variscan and Alpine mountain chains are collisional orogens, and are built up of pre-Variscan “building blocks” which, in most cases, originated at the Gondwana margin. Such pre-Variscan elements were part of a pre-Ordovician archipelago-like continental ribbon in the former eastern prolongation of Avalonia, and their present-day distribution resulted from juxtaposition through Variscan and/or Alpine tectonic evolution. The well-known nomenclatures applied to these mountain chains are the mirror of Variscan resp. Alpine organization. It is the aim of this paper to present a terminology taking into account their pre-Variscan evolution at the Gondwana margin. They may contain relics of volcanic islands with pieces of Cadomian crust, relics of volcanic arc settings, and accretionary wedges, which were separated from Gondwana by initial stages of Rheic ocean opening. After a short-lived Ordovician orogenic event and amalgamation of these elements at the Gondwanan margin, the still continuing Gondwana-directed subduction triggered the formation of Ordovician Al-rich granitoids and the latest Ordovician opening of Palaeo-Tethys. An example from the Alps (External Massifs) illustrates the gradual reworking of Gondwana-derived, pre-Variscan elements during the Variscan and Alpine/Tertiary orogenic cycles. 相似文献
19.
Rheological control on the tectonic evolution of a continental suture zone: the Variscan example from NW Iberia (Spain) 总被引：1，自引：1，他引：0
Rubén Díez Fernández David A. Foster Juan Gómez Barreiro Montserrat Alonso-García 《International Journal of Earth Sciences》2013,102(5):1305-1319
The Variscan continental suture zone exposed in NW Iberia is examined to uncover the long-lived rheological control exerted by the strata deposited over the external parts of Gondwana on its geodynamic evolution. The suture occurs within a set of allochthonous terranes whose limits were taken as domain boundaries to interpret the Variscan stacking of Paleozoic continental domains and retrodeform the resulting nappe pile. The suture zone formed due to closure of ocean basins located between Gondwana and Laurussia during the Late Paleozoic and consists of relics of oceanic and transitional crust. The suture zone exhibits a tabular to lens shape due to repeated tectonic events dominated by non-coaxial deformation (thrusts and low-angle normal faults). Thrusting and normal faulting also involved the margins of the continents bounding the suture. The structure of the continental blocks, however, is dominated by folds, particularly large nappe folds with pronounced superimposed flattening. The upper part of the basal allochthonous units comprises a rheologically incompetent domain below the suture zone. This domain is typified by the carbonaceous-rich strata, which are probably Ordovician–Silurian sediments based on U–Pb detrital zircon populations. The rheology of this layer determined the location of the first accretionary thrust that initiated the Late Devonian subduction of the Gondwana margin below the suture zone. By favoring fault development, the upper sequence of the basal allochthonous units as a whole influenced the exhumation of deep-seated continental crust, the transference of the suture zone over Gondwana, and the re-equilibration of the resulting overthickened crust. 相似文献
20.
Little is known about the Early Pleistocene landscape and glacial history of the Swiss Alps, largely because of the scarcity of sediments dating from that period. Here we investigate high-altitude, presumably Early Pleistocene relics of unconsolidated, near-surface sediments that occur at the Stockeseen site (close to the Stockhorn) and at Wagenmoos (close to Sibe H?ngste) in the Bernese Alps. We complemented our study by analysing cave gravels from 13 sites. Whereas the underlying bedrocks are part of the purely sedimentary Penninic Prealps and the Helvetic zone, the investigated sediments and cave gravels contain characteristic erratic crystalline clasts (HP-LT-metagabbro, medium-grade metamorphic quartzite, jadeitite, glaucophane-schist, low-grade metamorphic gabbro and peridotite). The erratics originate from Penninic and Austroalpine nappes which are exposed only south of the Bernese High Alps, today??s water divide. In combination with partly distinct glacial features of the indicator erratics, this suggests that transfluences existed from the Valais (Rh?ne valley) to the Bernese Alps. Our findings suggest two transfluence routes, one over a precursor of the Gemmipass to the palaeo-Kander valley, providing crystalline erratics towards Sibe H?ngste, and one over precursors of the Sanetschpass and Saanenm?serpass into the palaeo-Simmen valley and towards the Stockhorn. The Wagenmoos erratics must have been deposited before the re-routing of the palaeo-Aare river (from northward to westward) and its subsequent deepening, which indicates an Early Pleistocene timing of the respective transfluence. This is in agreement with published burial ages of ~1.87?Ma?±?0.21 for cave gravels with crystalline components in the cave system Réseau Siebenhengste?CHohgant (beneath the Wagenmoos site). 相似文献