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ΜΟΥΝΤΡΑΚΗΣ, Δ. "Tectonic evolution of the Hellenic Orogen. Geometry and kinematics of deformations." Bulletin of the Geological Society of Greece 34, no. 6 (January 1, 2002): 2113. http://dx.doi.org/10.12681/bgsg.16853.
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The Hellenic orogen consists of three orogenic belts: 1) the Cimmerian orogenic belt, including Rhodopian, Serbomacedonian, Circum Rhodope, Axios and Pelagonian zones, is the internal belt which has been created in pre-Late Jurassic times as a result of the northward drift of Cimmerian contrinental fragments from Gondwana towards Eurasia. Ophiolites from small ocean basins were mainly emplaced onto the Cimmerian continental margins in Middle Jurassic. 2) the Alpine orogenic belt, including External Hellenides and Pindos-Subpelagonian ophiolites and oceanic sediments (Neo-Tethyan), which has been created in Cretaceous-Paleogene times after the subduction of the Neotethyan oceanic crust beneath the Cimmerian-Eurasian plate and the collision of the Apulian microplate to the later, 3) the Mesogean orogenic belt along the External Hellenic orogenic arc as a result of the Mesogean-African underplate beneath the unique Alpine-Cimmerian-Eurasian plate in Miocen- Pliocene times and the exhumation of the Cretan-Southern Peloponesus tectonic windows. Structural analysis and detailed studies of the geometry and kinematics suggest that during Alpine-Mesogean orogenic process a SW-ward migration of successive complessional and extensional tectonic events took place resulted of successive subductions. Thus, crustal thickening produced by compressional tectonics in each area was followed by an extensional exhumation of underplate rocks as tectonic windows.
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Polat, Ali. "Ali Mehmet Celâl Şengör: A geologist who unravels the histories of continents and oceans." Canadian Journal of Earth Sciences 56, no. 11 (November 2019): v—viii. http://dx.doi.org/10.1139/cjes-2019-0175.
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This special issue is dedicated to Ali Mehmet Celâl Şengör for his outstanding contributions to plate tectonics and history of geology. His studies have unraveled several mysteries on the origin and deformation of continents and formation of orogenic belts in many parts of the world. We received 22 articles for the special issue, 11 of which are published in this issue. The rest of the articles will be published in the next issue. The articles in this issue mainly focus on geological processes in the Alpine–Himalayan orogenic belt and on the history of the theory of plate tectonics.
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Erdős, Zoltán, Ritske S. Huismans, and Peter van der Beek. "Control of increased sedimentation on orogenic fold-and-thrust belt structure – insights into the evolution of the Western Alps." Solid Earth 10, no. 2 (March 13, 2019): 391–404. http://dx.doi.org/10.5194/se-10-391-2019.
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Abstract. We use two-dimensional thermomechanical models to investigate the potential role of rapid filling of foreland basins in the development of orogenic foreland fold-and-thrust belts. We focus on the extensively studied example of the Western European Alps, where a sudden increase in foreland sedimentation rate during the mid-Oligocene is well documented. Our model results indicate that such an increase in sedimentation rate will temporarily disrupt the formation of an otherwise regular, outward-propagating basement thrust-sheet sequence. The frontal basement thrust active at the time of a sudden increase in sedimentation rate remains active for a longer time and accommodates more shortening than the previous thrusts. As the propagation of deformation into the foreland fold-and-thrust belt is strongly connected to basement deformation, this transient phase appears as a period of slow migration of the distal edge of foreland deformation. The predicted pattern of foreland-basin and basement thrust-front propagation is strikingly similar to that observed in the North Alpine Foreland Basin and provides an explanation for the coeval mid-Oligocene filling of the Swiss Molasse Basin, due to increased sediment input from the Alpine orogen, and a marked decrease in thrust-front propagation rate. We also compare our results to predictions from critical-taper theory, and we conclude that they are broadly consistent even though critical-taper theory cannot be used to predict the timing and location of the formation of new basement thrusts when sedimentation is included. The evolution scenario explored here is common in orogenic foreland basins; hence, our results have broad implications for orogenic belts other than the Western Alps.
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Lardeaux, Jean-Marc. "Deciphering orogeny: a metamorphic perspective Examples from European Alpine and Variscan belts." Bulletin de la Société Géologique de France 185, no. 5 (May 1, 2014): 281–310. http://dx.doi.org/10.2113/gssgfbull.185.5.281.
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AbstractIn this paper we review and discuss, in a synthetic historical way, the main results obtained on Variscan metamorphism in the French Massif Central. First, we describe the pre-orogenic architecture of the French Massif Central on the base of available lithostratigraphic and geochemical constraints. Second, we portray the progressive metamorphic evolution through time and space with the presentation of 6 metamorphic maps corresponding to critical orogenic periods, namely 430–400 Ma, 400–370 Ma, 370–360 Ma, 360–345 Ma, 340–325 Ma and 320–290 Ma. We discuss the role of multiple subductions in orogeny, the metamorphic effects of continental collision (i.e. regional development of intermediate-pressure metamorphic series) as well as the links between post-thickening tectonics and the regional development of low-pressure metamorphic series coeval with crustal partial melting. As it was the case for the western Alps, we emphasize the lack of temporal data on high-pressure/low-temperature metamorphic rocks as well as the uncertainties on the sizes of rock units that have recorded the same metamorphic history (i.e. coherent P-T-t/deformation trajectories). Finally, we underline the main differences and similarities between the metamorphic evolutions of the western Alps and the French Massif Central.
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Scisciani, Vittorio, Stefano Patruno, Enrico Tavarnelli, Fernando Calamita, Paolo Pace, and David Iacopini. "Multi-phase reactivations and inversions of Paleozoic–Mesozoic extensional basins during the Wilson cycle: case studies from the North Sea (UK) and the Northern Apennines (Italy)." Geological Society, London, Special Publications 470, no. 1 (2019): 205–43. http://dx.doi.org/10.1144/sp470-2017-232.
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AbstractThe Caledonian and Variscan orogens in northern Europe and the Alpine-age Apennine range in Italy are classic examples of thrust belts that were developed at the expense of formerly rifted, passive continental margins that subsequently experienced various degrees of post-orogenic collapse and extension. The outer zones of orogenic belts, and their adjoining foreland domains and regions, where the effects of superposed deformations are mild to very mild make it possible to recognize and separate structures produced at different times and to correctly establish their chronology and relationships. In this paper we integrate subsurface data (2D and 3D seismic reflection and well logs), mainly from the North Sea, and structural field evidence, mainly from the Apennines, with the aim of reconstructing and refining the structural evolution of these two provinces which, in spite of their different ages and present-day structural framework, share repeated pulses of alternating extension and compression. The main outcome of this investigation is that in both scenarios, during repeated episodes of inversion that are a characteristic feature of the Wilson cycle, inherited basement structures were effective in controlling stress localization along faults affecting younger sedimentary cover rocks.
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Bonnet, Cécile, Jacques Malavieille, and Jon Mosar. "Surface processes versus kinematics of thrust belts: impact on rates of erosion, sedimentation, and exhumation – Insights from analogue models." Bulletin de la Société Géologique de France 179, no. 3 (May 1, 2008): 297–314. http://dx.doi.org/10.2113/gssgfbull.179.3.297.
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Abstract The mechanical equilibrium of an orogenic wedge is maintained thanks to interactions between tectonic processes and surface processes. To better constrain the influence of erosion and sedimentation on the evolution of orogens, we performed a series of analogue models based on the tapered wedge principle, varying the amounts of erosion and sedimentation. The models develop by frontal accretion in the foreland basin and by simple underthrusting and subsequent underplating in the hinterland. The variations in rates of erosion and sedimentation strongly modify the extent, the morphology, the structures, the timing of development and the material paths in the different models. Under certain conditions, entire structural units can be formed and subsequently eroded out of the geological record, leading to important underestimations when restoring sections. Particles located in the converging lower-plate or in the upper-plate show complex uplift paths related to tectonic stages. The correlation between models and three Alpine tectonic cross-sections emphasizes the role of erosion and sedimentation on the dynamics and development of the orogen and adjacent Molasse basin. Along strike changes in the present structure of the orogen could be explained in part by differences in surface processes.
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GRANADO, P., W. THÖNY, N. CARRERA, O. GRATZER, P. STRAUSS, and J. A. MUÑOZ. "Basement-involved reactivation in foreland fold-and-thrust belts: the Alpine–Carpathian Junction (Austria)." Geological Magazine 153, no. 5-6 (February 23, 2016): 1110–35. http://dx.doi.org/10.1017/s0016756816000066.
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AbstractThe late Eocene – early Miocene Alpine–Carpathian fold-and-thrust belt (FTB) lies in the transition between the Eastern Alps and the Western Carpathians, SE of the Bohemian crystalline massif. Our study shows the involvement of crystalline basement from the former European Jurassic continental margin in two distinct events. A first extensional event coeval with Eggerian–Karpatian (c. 28–16 Ma) thin-skinned thrusting reactivated the rift basement fault array and resulted from the large degree of lower plate bending promoted by high lateral gradients of lithospheric strength and slab pull forces. Slab break-off during the final stages of collision around Karpatian times (c. 17–16 Ma) promoted large-wavelength uplift and an excessive topographic load. This load was reduced by broadening the orogenic wedge through the reactivation of the lower-plate deep detachment beneath and ahead of the thin-skinned thrust front (with the accompanying positive inversion of the basement fault array) and ultimately, by the collapse of the hinterland summits, enhanced by transtensional faulting. Although this work specifically deals with the involvement of the basement in the Alpine–Carpathian Junction, the main conclusions are of general interest to the understanding of orogenic systems.
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Lardeaux, Jean-Marc. "Deciphering orogeny: a metamorphic perspective. Examples from European Alpine and Variscan belts." Bulletin de la Société Géologique de France 185, no. 2 (February 1, 2014): 93–114. http://dx.doi.org/10.2113/gssgfbull.185.2.93.
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AbstractIn this paper we review and discuss, in a synthetic historical way, the main results obtained on Alpine metamorphism in the western Alps. First, we describe the finite metamorphic architecture of the western Alps and discuss its relationships with subduction and collision processes. Second, we portray the progressive metamorphic evolution through time and space with the presentation of 5 metamorphic maps corresponding to critical orogenic periods, namely 85-65 Ma, 60-50 Ma, 48-40 Ma, 38-33 Ma and 30-20 Ma. We underline the lack of temporal data on high-pressure/low-temperature metamorphic rocks as well as the severe uncertainties on the sizes of rock units that have recorded the same metamorphic history (i.e. coherent P-T-t/deformation trajectories). We discuss the role of subduction-driven metamorphism in ocean-derived protoliths and the conflicting models that account for the diachrony of continental subductions in the western Alps.
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Butler, Robert W. H., Henry W. Lickorish, Jamie Vinnels, and William D. McCaffrey. "Untangling the Annot sand fairway: structure and stratigraphy of the Eastern Champsaur Basin (Eocene–Oligocene), French Alps." Journal of the Geological Society 177, no. 6 (July 7, 2020): 1197–209. http://dx.doi.org/10.1144/jgs2020-015.
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Early foredeep successions can yield insight into tectonic processes operating adjacent to and ahead of fledgling orogenic belts but are commonly deformed by the same orogens. We develop a workflow towards stratigraphic understanding of these deformed basins, applied to the Eastern Champsaur Basin of the French Alps. This contains a down-system correlative of the southern-sourced (Eocene–Oligocene) Annot turbidites. These strata are deformed by arrays of west-facing folds that developed beneath the Embrunais–Ubaye tectonic allochthon. The folds vary in geometry through the stratigraphic multilayer. Total shortening in the basin is around 4 km and the restored (un-decompacted) stratal thickness exceeds 980 m. The turbidites are generally sand-rich and bed-sets can be correlated through the entire fold train. The succession shows onlap and differential thickening indicating deposition across palaeobathymetry that evolved during active basement deformation, before being overridden by the allochthon. The sand system originally continued over what is now the Ecrins basement massif that, although contributing to basin floor structure, served only to confine and potentially focus further sediment transport to the north. Deformation ahead of the main Alpine orogen appears to have continued progressively, and the past definition of distinct ‘phases’ (‘pre-’ and ‘post-Nummulitic’) is an artefact of the stratigraphic record.
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Beltrando, Marco, Gianreto Manatschal, Geoffroy Mohn, Giorgio Vittorio Dal Piaz, Alberto Vitale Brovarone, and Emmanuel Masini. "Recognizing remnants of magma-poor rifted margins in high-pressure orogenic belts: The Alpine case study." Earth-Science Reviews 131 (April 2014): 88–115. http://dx.doi.org/10.1016/j.earscirev.2014.01.001.
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Lescoutre, Rodolphe, and Gianreto Manatschal. "Role of rift-inheritance and segmentation for orogenic evolution: example from the Pyrenean-Cantabrian system." BSGF - Earth Sciences Bulletin 191 (2020): 18. http://dx.doi.org/10.1051/bsgf/2020021.
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The Basque-Cantabrian junction corresponds to an inverted rift accommodation zone at the limit between the former hyperextended Pyrenean and Cantabrian rift segments. The recognition of an inherited rift segment boundary allows to investigate the reactivation associated with large-scale rift segmentation in an orogenic system. We use criteria from published field observations and seismic data to propose a new map of rift domains for the Basque-Cantabrian junction. We also provide balanced cross-sections that allow to define the along-strike architecture associated with segmentation during rifting and subsequent Alpine reactivation. Based on these results, this study aims to characterize and identify reactivated and newly formed structures during inversion of two rift segments and its intermitted segment boundary. It also aims to describe the timing of thin-skinned and thick-skinned deformation associated with the inversion of segmented rift systems. During convergence, two phases have been recognized within the rift segment (eastern Mauléon basin). The Late Cretaceous to Paleocene underthrusting/subduction phase was mostly governed by thin-skinned deformation that reactivated the former hyperextended domains and the supra-salt sedimentary cover. The Eocene to Miocene collisional phase, controlled by thick-skinned deformation that took place once necking domains collided and formed an orogenic wedge. At the rift segment boundary, the underthrusting/subduction phase was already controlled by thick-skinned deformation due to the formation of shortcutting thrust faults at the termination of overlapping V-shaped rift segments. This led to the formation of a proto-wedge composed of the Basque massifs. We suggest that this proto-wedge is responsible for the preservation of pre-Alpine structures in the Basque massifs and for the emplacement of subcontinental mantle rocks at a crustal level beneath the western Mauléon basin. These results argue for a first order cylindrical orogenic architecture from the Central Pyrenean segment to the Cantabrian segment (up to the Santander transfer zone) despite rift segmentation. They also highlight the control of 3D rift-inheritance for the initial phase of orogenic evolution and for the local architecture of mountain belts.
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Dieni, Iginio, Francesco Massari, and Jacques Médus. "Age, depositional environment and stratigraphic value of the Cuccuru ’e Flores Conglomerate: insight into the Palaeogene to Early Miocene geodynamic evolution of Sardinia." Bulletin de la Société Géologique de France 179, no. 1 (January 1, 2008): 51–72. http://dx.doi.org/10.2113/gssgfbull.179.1.51.
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Abstract The Cuccuru ’e Flores Conglomerate of eastern Sardinia, a syntectonic unit lining major Cenozoic faults, has been dated by means of palynology at the early middle Lutetian. The deposits were mainly laid down by sediment gravity flows in a subaqueous setting and formed aprons of laterally interfingering debris cones at the toe of active tectonic scarps. Most clasts of rudites are of local provenance. Interestingly, the rudites include minor amounts of clasts of formations which no longer crop out in the area, providing important information on the reconstruction of the original stratigraphic succession and palaeogeography, especially during late Cretaceous and early Palaeogene times. During the Eocene, i.e. in a pre-rotation stage, Sardinia was subjected to the influence of both Alpine and Pyrenean orogenic belts. In eastern Sardinia, the compressional stress field was consistent with that existing in the foreland of the Alpine chain in Corsica, and was expressed by significant wrench tectonics affecting the Variscan basement and the pre-Oligocene sedimentary cover. Deformations associated with major strike-slip faults, such as enéchelon folds and positive flower structures occurring in fault-restraining bends, suggest a shortening direction around N105° (in present-day coordinates). A subsequent wrenching phase of Late Oligocene-Early Miocene age involved reactivation of former “Alpine” faults in a sharply different stress field. This tectonics reflects the intermediate position of the eastern Sardinia belt between the area affected by back-arc stretching (the Sardinian rift and the Liguro-Provençal basin) and the arcuate Apenninic subduction front active in a framework of left-lateral oblique plate convergence.
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Piana, Fabrizio, Luca Barale, Carlo Bertok, Anna d’Atri, Andrea Irace, and Pietro Mosca. "The Alps-Apennines Interference Zone: A Perspective from the Maritime and Western Ligurian Alps." Geosciences 11, no. 5 (April 25, 2021): 185. http://dx.doi.org/10.3390/geosciences11050185.
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In SW Piemonte the Western Alps arc ends off in a narrow, E-W trending zone, where some geological domains of the Alps converged. Based on a critical review of available data, integrated with new field data, it is concluded that the southern termination of Western Alps recorded the Oligocene-Miocene activity of a regional transfer zone (southwestern Alps Transfer, SWAT) already postulated in the literature, which should have allowed, since early Oligocene, the westward indentation of Adria, while the regional shortening of SW Alps and tectonic transport toward the SSW (Dauphinois foreland) was continuing. This transfer zone corresponds to a system of deformation units and km-scale shear zones (Gardetta-Viozene Zone, GVZ). The GVZ/SWAT developed externally to the Penninic Front (PF), here corresponding to the Internal Briançonnais Front (IBF), which separates the Internal Briançonnais domain, affected by major tectono-metamorphic transformations, from the External Briançonnais, subjected only to anchizonal metamorphic conditions. The postcollisional evolution of the SW Alps axial belt units was recorded by the Oligocene to Miocene inner syn-orogenic basin (Tertiary Piemonte Basin, TPB), which rests also on the Ligurian units stacked within the adjoining Apennines belt in southern Piemonte. The TPB successions were controlled by transpressive faults propagating (to E and NE) from the previously formed Alpine belt, as well as by the Apennine thrusts that were progressively stacking the Ligurian units, resting on the subducting Adriatic continental margin, with the TPB units themselves. This allows correlation between Alps and Apennines kinematics, in terms of age of the main geologic events, interference between the main structural systems and tectonic control exerted by both tectonic belts on the same syn-orogenic basin.
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Molli, Giancarlo, and Jacques Malavieille. "Orogenic processes and structural heritage in Alpine-type mountain belts and Mediterranean region: A foreword and an introduction." Tectonophysics 579 (December 2012): 1–3. http://dx.doi.org/10.1016/j.tecto.2012.07.020.
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BALESTRO, GIANNI, ANDREA FESTA, ALESSANDRO BORGHI, DANIELE CASTELLI, MARCO GATTIGLIO, and PAOLA TARTAROTTI. "Role of Late Jurassic intra-oceanic structural inheritance in the Alpine tectonic evolution of the Monviso meta-ophiolite Complex (Western Alps)." Geological Magazine 155, no. 2 (July 17, 2017): 233–49. http://dx.doi.org/10.1017/s0016756817000553.
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AbstractThe eclogite-facies Monviso meta-ophiolite Complex in the Western Alps represents a well-preserved fragment of oceanic lithosphere and related Upper Jurassic – Lower Cretaceous sedimentary covers. This meta-ophiolite sequence records the evolution of an oceanic core complex formed by mantle exhumation along an intra-oceanic detachment fault (the Baracun Shear Zone), related to the opening of the Ligurian–Piedmont oceanic basin (Alpine Tethys). On the basis of detailed geological mapping, and structural, stratigraphic and petrological observations, we propose a new interpretation for the tectonostratigraphic architecture of the Monviso meta-ophiolite Complex, and discuss the role played by structural inheritance in its formation. We document that subduction- and exhumation-related Alpine tectonics were strongly influenced by the inherited Jurassic intra-oceanic tectonosedimentary physiography. The latter, although strongly deformed during a major Alpine stage of non-cylindrical W-verging folding and faulting along exhumation-related Alpine shear zones (i.e. the Granero–Casteldelfino and Villanova–Armoine shear zones), was not completely dismembered into different tectonic units or subduction-related mélanges as suggested in previous interpretations. The present-day architecture of the Monviso meta-ophiolite Complex results from nappe-scale folding with a significant component of shearing, and strain partitioning of the Alpine deformation, which were controlled by the inherited occurrence of (i) lateral and vertical variations of facies and thickness of sediments, (ii) an intra-oceanic fault-rock assemblage, which acted as weak horizons in concentrating deformation, and (iii) remnants of a volcanic ridge, which consists of massive metabasalt. Thus, the recognition of pre-collisional, intra-oceanic, tectonostratigraphic inheritance represents an important step in reconstructing the tectonic evolution of meta-ophiolite units in orogenic belts.
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LENAZ, DAVIDE, VADIM S. KAMENETSKY, and FRANCESCO PRINCIVALLE. "Cr-spinel supply in the Brkini, Istrian and Krk Island flysch basins (Slovenia, Italy and Croatia)." Geological Magazine 140, no. 3 (May 2003): 335–42. http://dx.doi.org/10.1017/s0016756803007581.
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In Late Cretaceous times, subduction of oceanic crust occurred to the north of the Adria plate and was followed by the formation of ophiolitic complexes. Continental collision in Alpine orogenic belts lasted from Late Cretaceous to Early Tertiary times. The progressive contraction of oceanic crust caused the uplift of previously rifted continental margin and platforms and the formation of foredeep flysch basins. Detrital Cr-spinels are widespread in Eocene sandstones of the Brkini, Istrian and Krk Island foredeep flysch basins. On the basis of their TiO2 content and FeO/Fe2O3 ratio, spinels derived from peridotites and mantle-derived magmatic rocks were distinguished. The first are statistically more abundant and are considered to have been derived from type I and II peridotites. The second appear to be mainly related to backarc basin products. These results suggest that Cr-spinels were derived from the erosion of the Internal Dinarides, where type II and III peridotites are present, and also from the Outer Dinarides, where type I peridotites crop out.
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Vannucchi, Paola, Jason P. Morgan, Alina Polonia, and Giancarlo Molli. "The life cycle of subcontinental peridotites: From rifted continental margins to mountains via subduction processes." Geology 48, no. 12 (July 28, 2020): 1154–58. http://dx.doi.org/10.1130/g47717.1.
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Abstract Serpentinization greatly affects the physical and chemical properties of lithospheric mantle. Here we address the fate of serpentinized peridotites and their influence over an entire Wilson cycle. We document the near-surface journey of serpentinized subcontinental peridotites exhumed during rifting and continental breakup, reactivated as buoyant material during subduction, and ultimately emplaced as “ophiolite-like” fragments within orogenic belts. This life cycle is particularly well documented in former Tethys margins, where recent studies describe the ongoing incorporation of Mesozoic serpentinized subcontinental peridotites that diapirically rise from a subducting lower plate’s mantle to be emplaced into the accretionary prism in front of a continental arc. This newly recognized mode of subduction-linked serpentine diapirism from the downgoing lithospheric slab is consistent with the origin of some exhumed serpentinized subcontinental peridotites in the Apennines (Italy), these assemblages reaching their present locations during Alpine orogenesis. Transfer of serpentinized subcontinental peridotites from the downgoing to the overriding plate motivates the concept of a potentially “leaky” subduction channel. Weak serpentine bodies may in fact rise into, preferentially migrate within, and eventually leave the intraplate shear zone, leading to strong lateral heterogeneities in its composition and mechanical strength.
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Chew, David M., and Cees R. Van Staal. "The Ocean – Continent Transition Zones Along the Appalachian – Caledonian Margin of Laurentia: Examples of Large-Scale Hyperextension During the Opening of the Iapetus Ocean." Geoscience Canada 41, no. 2 (May 7, 2014): 165. http://dx.doi.org/10.12789/geocanj.2014.41.040.
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A combination of deep seismic imaging and drilling has demonstrated that the ocean-continent transition (OCT) of present-day, magma-poor, rifted continental margins is a zone of hyperextension characterized by extreme thinning of the continental crust that exhumed the lowermost crust and/or serpentinized continental mantle onto the seafloor. The OCT on present-day margins is difficult to sample, and so much of our knowledge on the detailed nature of OCT sequences comes from obducted, magma-poor OCT ophiolites such as those preserved in the upper portions of the Alpine fold-and-thrust belt. Allochthonous, lens-shaped bodies of ultramafic rock are common in many other ancient orogenic belts, such as the Caledonian – Appalachian orogen, yet their origin and tectonic significance remains uncertain. We summarize the occurrences of potential ancient OCTs within this orogen, commencing with Laurentian margin sequences where an OCT has previously been inferred (the Dalradian Supergroup of Scotland and Ireland and the Birchy Complex of Newfoundland). We then speculate on the origin of isolated occurrences of Alpine-type peridotite within Laurentian margin sequences in Quebec – Vermont and Virginia – North Carolina, focusing on rift-related units of Late Neoproterozoic age (so as to eliminate a Taconic ophiolite origin). A combination of poor exposure and pervasive Taconic deformation means that origin and emplacement of many ultramafic bodies in the Appalachians will remain uncertain. Nevertheless, the common occurrence of OCT-like rocks along the whole length of the Appalachian – Caledonian margin of Laurentia suggests that the opening of the Iapetus Ocean may have been accompanied by hyperextension and the formation of magma-poor margins along many segments.SOMMAIREDes travaux d’imagerie sismique et des forages profonds ont montré que la transition océan-continent (OCT) de marges continentales de divergence pauvre en magma exposée de nos jours, correspond à une zone d’hyper-étirement tectonique caractérisée par un amincissement extrême de la croûte continentale, qui a exhumé sur le fond marin, jusqu’à la tranche la plus profonde de la croûte continentale, voire du manteau continental serpentinisé. Parce qu’on peut difficilement échantillonner l’OCT sur les marges actuelles, une grande partie de notre compréhension des détails de la nature de l’OCT provient d’ophiolites pauvres en magma d’une OCT obduite, comme celles préservées dans les portions supérieures de la bande plissée alpine. Des masses lenticulaires de roches ultramafiques allochtones sont communes dans de nombreuses autres bandes orogéniques anciennes, comme l’orogène Calédonienne-Appalaches, mais leur origine et signification tectonique reste incertaine. Nous présentons un sommaire des occurrences d’OCT potentielles anciennes de cet orogène, en commençant par des séquences de la marge laurentienne, où la présence d’OCT a déjà été déduites (le Supergroupe Dalradien d’Écosse et d'Irlande, et le complexe de Birchy de Terre-Neuve). Nous spéculons ensuite sur l'origine de cas isolés de péridotite de type alpin dans des séquences de marge des Laurentides du Québec-Vermont et de la Virginie-Caroline du Nord, en nous concentrant sur les unités de rift d'âge néoprotérozoïque tardif (pour éviter les ophiolites du Taconique). La conjonction d’affleurements de piètre qualité et de la déformation taconique omniprésente, signifie que l'origine et la mise en place de nombreuses masses ultramafiques dans les Appalaches demeureront incertaines. Néanmoins, la présence fréquente de roches de type OCT tout le long de la marge Calédonnienne-Appalaches de Laurentia suggère que l'ouverture de l'océan Iapetus peut avoir été accompagnée d’hyper-étirement et de la formation de marges pauvres en magma le long de nombreux segments.
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Şengör, A. M. Celâl, and Joann Stock. "The Ayyubid Orogen: An Ophiolite Obduction-Driven Orogen in the Late Cretaceous of the Neo-Tethyan South Margin." Geoscience Canada 41, no. 2 (May 7, 2014): 225. http://dx.doi.org/10.12789/geocanj.2014.41.042.
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A minimum 5000-km long obduction-driven orogeny of medial to late Cretaceous age is located between Cyrenaica in eastern Libya and Oman. It is herein called the Ayyubid Orogen after the Ayyubid Empire that covered much of its territory. The Ayyubid orogen is distinct from other Alpide orogens and has two main parts: a western, mainly germanotype belt and an eastern mainly alpinotype belt. The germanotype belt formed largely as a result of an aborted obduction, whereas the alpinotype part formed as a result of successful and large-scale obduction events that choked a nascent subduction zone. The mainly germanotype part coincides with Erich Krenkel's Syrian Arc (Syrischer Bogen) and the alpinotype part with Ricou's Peri-Arabian Ophiolitic Crescent (Croissant Ophiolitique péri-Arabe). These belts formed as a consequence of the interaction of one of the now-vanished Tethyan plates and Afro-Arabia. The Africa-Eurasia relative motion has influenced the orogen's evolution, but was not the main causative agent. Similar large and complex obduction-driven orogens similar to the Ayyubids may exist along the Ordovician Newfoundland/Scotland margin of the Caledonides and along the Ordovician European margin of the Uralides.SOMMAIREEntre la Cyrénaïque dans l'est de la Libye et Oman, se trouve un ceinture orogénique d’au moins 5 000 km de longueur créé par obduction au Crétacé moyen et tardif. Nous le nommons ici l’orogène ayyoubide d’après l'empire ayyoubide qui couvrait une grande partie de son territoire. L'orogène ayyoubide qui est distincte des autres orogènes alpides, comporte deux parties principales : une bande occidentale, principalement germanotype, et une bande orientale principalement alpinotype. La bande germanotype s’est formée en grande partie à la suite d'une obduction avortée, tandis que la partie alpinotype s’est formée par des épisodes d’obduction à grande échelle qui ont étranglé une zone de subduction naissante. La partie principalement germanotype coïncide avec l’arc syrien d’Erich Krenkel (Syrischer Bogen), alors que la partie alpinotype correspond au croissant ophiolitique péri-Arabe de Ricou (Croissant ophiolitique péri-Arabe). Ces bandes se sont formées par l'interaction de l'une des plaques de la Téthys, maintenant disparues, avec l’Afro-Arabie. Le mouvement relatif Afrique-Eurasie a influencé l'évolution de l'orogène, mais ça n’a pas été le principal facteur. Des orogènes grandes et complexes résultant de mécanismes d’obduction similaires à l’orogène Ayyoubide peuvent exister le long de la marge des Calédonides de l'Ordovicien de Terre-Neuve/Écosse et le long de la marge européenne des Uralides de l'Ordovicien.
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ERKÜL, FUAT. "Tectonic significance of synextensional ductile shear zones within the Early Miocene Alaçamdağ granites, northwestern Turkey." Geological Magazine 147, no. 4 (December 4, 2009): 611–37. http://dx.doi.org/10.1017/s0016756809990719.
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AbstractSynextensional granitoids may have significant structural features leading to the understanding of the evolution of extended orogenic belts. One of the highly extended regions, the Aegean region, includes a number of metamorphic core complexes and synextensional granitoids that developed following the Alpine collisional events. The Alaçamdağ area in northwestern Turkey is one of the key areas where Miocene granites crop out along the boundary of various tectonic units. Structural data from the Early Miocene Alaçamdağ granites demonstrated two different deformation patterns that may provide insights into the development of granitic intrusions and metamorphic core complexes. (1) Steeply dipping ductile shear zones caused emplacement of syn-tectonic granite stocks; they include kinematic indicators of a sinistral top-to-the-SW displacement. This zone has also juxtaposed the İzmir–Ankara Zone and the Menderes Massif in the west and east, respectively. (2) Gently dipping ductile shear zones have developed within the granitic stocks that intruded the schists of the Menderes Massif on the structurally lower parts. Kinematic data from the foliated granites indicate a top-to-the-NE displacement, which can be correlated with the direction of the hanging-wall movement documented from the Simav and Kazdağ metamorphic core complexes. The gently dipping shear zones indicate the presence of a detachment fault between the Menderes Massif and the structurally overlying İzmir–Ankara Zone. Mesoscopic- to map-scale folds in the shallow-dipping shear zones of the Alaçamdağ area were interpreted to have been caused by coupling between NE–SW stretching and the accompanying NW–SE shortening of ductilely deformed crust during Early Miocene times. One of the NE-trending shear zones fed by granitic magmas was interpreted to form the northeastern part of a sinistral wrench corridor which caused differential stretching between the Cycladic and the Menderes massifs. This crustal-scale wrench corridor, the İzmir–Balıkesir transfer zone, may have controlled the asymmetrical and symmetrical extensions in the orogenic domains. The combination of the retreat of the Aegean subduction zone and the lateral slab segmentation leading to the sinistral oblique-slip tearing within the Eurasian upper plate appears to be a plausible mechanism for the development of such extensive NE-trending shear zones in the Aegean region.
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Verwater, Vincent F., Eline Le Breton, Mark R. Handy, Vincenzo Picotti, Azam Jozi Najafabadi, and Christian Haberland. "Neogene kinematics of the Giudicarie Belt and eastern Southern Alpine orogenic front (northern Italy)." Solid Earth 12, no. 6 (June 15, 2021): 1309–34. http://dx.doi.org/10.5194/se-12-1309-2021.
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Abstract. Neogene indentation of the Adriatic plate into Europe led to major modifications of the Alpine orogenic structures and style of deformation in the Eastern and Southern Alps. The Giudicarie Belt is a prime example of this, as it offsets the entire Alpine orogenic edifice; its activity has been kinematically linked to strike-slip faulting and lateral extrusion of the Eastern Alps. Remaining questions on the exact role of this fold-and-thrust belt in the structure of the Alpine orogen at depth necessitate a quantitative analysis of the shortening, kinematics, and depth of decoupling beneath the Giudicarie Belt and adjacent parts of the Southern Alps. Tectonic balancing of a network of seven cross sections through the Giudicarie Belt parallel to the local NNW–SSE shortening direction reveals that this belt comprises two kinematic domains that accommodated different amounts of shortening during overlapping times. These two domains are separated by the NW–SE-oriented strike-slip Trento-Cles–Schio-Vicenza fault system, which offsets the Southern Alpine orogenic front in the south and merges with the Northern Giudicarie Fault in the north. The SW kinematic domain (Val Trompia sector) accommodated at least ∼ 18 km of Late Oligocene to Early Miocene shortening. Since the Middle Miocene, this domain experienced at least ∼ 12–22 km shortening, whereas the NE kinematic domain accommodated at least ∼ 25–35 km shortening. Together, these domains contributed an estimated minimum of ∼ 40–47 km of sinistral strike-slip motion along the Northern Giudicarie Fault, implying that most offset of the Periadriatic Fault is due to Late Oligocene to Neogene indentation of the Adriatic plate into the Eastern Alps. Moreover, the faults linking the Giudicarie Belt with the Northern Giudicarie Fault reach ∼ 15–20 km depth, indicating a thick-skinned tectonic style of deformation. These fault detachments may also connect at depth with a lower crustal Adriatic wedge that protruded north of the Periadriatic Fault and are responsible for N–S shortening and eastward, orogen-parallel escape of deeply exhumed units in the Tauern Window. Finally, the E–W lateral variation of shortening across the Giudicarie Belt indicates internal deformation and lateral variation in strength of the Adriatic indenter related to Permian–Mesozoic tectonic structures and paleogeographic zones.
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Tartarotti, Paola, Silvana Martin, Andrea Festa, and Gianni Balestro. "Metasediments Covering Ophiolites in the HP Internal Belt of the Western Alps: Review of Tectono-Stratigraphic Successions and Constraints for the Alpine Evolution." Minerals 11, no. 4 (April 14, 2021): 411. http://dx.doi.org/10.3390/min11040411.
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Ophiolites of the Alpine belt derive from the closure of the Mesozoic Tethys Ocean that was interposed between the palaeo-Europe and palaeo-Adria continental plates. The Alpine orogeny has intensely reworked the oceanic rocks into metaophiolites with various metamorphic imprints. In the Western Alps, metaophiolites and continental-derived units are distributed within two paired bands: An inner band where Alpine subduction-related high-pressure (HP) metamorphism is preserved, and an outer band where blueschist to greenschist facies recrystallisation due to the decompression path prevails. The metaophiolites of the inner band are hugely important not just because they provide records of the prograde tectonic and metamorphic evolution of the Western Alps, but also because they retain the signature of the intra-oceanic tectono-sedimentary evolution. Lithostratigraphic and petrographic criteria applied to metasediments associated with HP metaophiolites reveal the occurrence of distinct tectono-stratigraphic successions including quartzites with marbles, chaotic rock units, and layered calc schists. These successions, although sliced, deformed, and superposed in complex ways during the orogenic stage, preserve remnants of their primary depositional setting constraining the pre-orogenic evolution of the Jurassic Tethys Ocean.
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Vozárová, Anna, Fritz Ebner, Sándor Kovács, Hans-Georg Kräutner, Tibor Szederkenyi, Branislav Krstić, Jasenka Sremac, Dunja Aljinovič, Matevž Novak, and Dragomir Skaberne. "Late Variscan (Carboniferous to Permian) environments in the Circum Pannonian Region." Geologica Carpathica 60, no. 1 (February 1, 2009): 71–104. http://dx.doi.org/10.2478/v10096-009-0002-7.
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Late Variscan (Carboniferous to Permian) environments in the Circum Pannonian RegionThe Pennsylvanian-Cisuralian late-orogenic and post-orogenic paleoenvironments of the Circum Pannonian Region (CPR) include tectono-stratigraphic sequences developed from the Upper Bashkirian-Moscovian marine early molasse stage up to the Guadalupian-Lopingian post-orogenic stage, with gradual connection to the beginning of the Alpine (Neotethyan) sedimentary cycle. Shallow marine siliciclastic or carbonate siliciclastic overstep sequences started in the internal part of the Variscan orogenic belt during the latest Serpukhovian and Bashkirian-Moscovian. They overlapped unconformably the variably metamorphosed Variscan basement, or weakly deformed and metamorphosed foreland and syn-orogenic flysch sediments of Mississippian to Early Pennsylvanian age. The post-Variscan rifting largely affected the Variscan orogenic belt by reactivation of the Variscan lithosphere. The late- to post-orogenic terrestrial sequences started within the internal part of the Variscan orogenic belt during the Middle/Late Pennsylvanian. It continued gradually to terrestrial-shallow water carbonate-siliciclastic sequences in its external part through the Permian. According to the present configuration, the Alpine (Neotethyan) northward shifting transgression started during the Guadalupian/Lopingian in the South and during the Early Triassic in the North.
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Ghanbarian, Mohammad Ali, Ali Yassaghi, and Reza Derakhshani. "Detecting a Sinistral Transpressional Deformation Belt in the Zagros." Geosciences 11, no. 6 (May 24, 2021): 226. http://dx.doi.org/10.3390/geosciences11060226.
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The oblique collision between the northeastern margin of the Arabian platform and the Iranian microcontinent has led to transpressional deformation in the Zagros orogenic belt in the central part of the Alpine–Himalayan orogenic belt. Although previous articles have emphasized the dextral sense of shear in the Zagros orogenic belt, in this paper, using several indicators of kinematic shear sense upon field checking and microscopic thin-section studies, evidence of the development of a sinistral top-to-the NW deformation belt is presented. The mean attitudes of the foliations and lineations in this belt are 318°/55°NE and 19°/113°, respectively.
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BUZZI, L., L. GAGGERO, L. GROZDANOV, S. YANEV, and F. SLEJKO. "High-Mg potassic rocks in the Balkan segment of the Variscan belt (Bulgaria): implications for the genesis of orogenic lamproite magmas." Geological Magazine 147, no. 3 (October 27, 2009): 434–50. http://dx.doi.org/10.1017/s0016756809990550.
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AbstractUltrapotassic plutons from several domains of the Variscan orogenic belt have been in turn interpreted as syn- to post-orogenic due to their age spread, but assessment of their geodynamic setting and source regions is still open to interpretation. In the Svoge region (Bulgaria), at the southern margin of the Balkan orogen, peralkalic plutons are hosted within Ordovician pelites. The main intrusion, with lamproitic affinity, which hosts monzodiorite xenoliths and a polyphase syenite suite, was emplaced at a shallow level.40Ar–39Ar dating by step-heating of amphibole and biotite yielded a Early Carboniferous intrusion age for the main body (337 ± 4 and 339.1 ± 1.6 Ma). The lamproite intrusion is silica-rich compared with bona fide lamproites and characterized by moderate LILE and LaN/YbNenrichments. Sr and Nd isotopic data (initial ϵNdin the range −4.87 to −5.88) suggest an origin in a depleted lithospheric mantle, possibly refertilized by eo-Variscan subduction. The high-K syn-tectonic plutonism in several zones of the Variscan orogen (Bohemian, Austro-Alpine, Vosges, French and Corsica domains) is consistent with a derivation of high-K magmatism from partial melting of metasomatized mantle following the subduction along the collision front between Gondwana and Laurasia.
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Alonso-Chaves, F., J. I. Soto, M. Orozco, A. A. Kilias, and M. D. Tranos. "TECTONIC EVOLUTION OF THE BETIC CORDILLERA: AN OVERVIEW." Bulletin of the Geological Society of Greece 36, no. 4 (January 1, 2004): 1598. http://dx.doi.org/10.12681/bgsg.16563.
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The Betic (Southern Spain) and the Rif (Morocco) mountain chains, connected through the Gibraltar Strait, shapes a W-E elongated and arcuate Alpine orogenic belt. The Alborân Sea, in continuity to the east with the South Balearic Basin, is located in the inner part of this alpine belt. The Iberian and African continental forelands bound the region as a whole to the north and south, respectively, and to the east it is connected to the oceanic Sardine-Balearic Basin. The peculiarities of these westernmost Mediterranean chains result from: (1) its position between two large convergent plates -Africa and Europe- that have had variable directions of relative motion since the late Cretaceous; and (2) the Neogene westward migration of the orogenic hinterland and its simultaneous "back-arc"-like extension, generating the Alborén Sea basin. The complexes and large paleogeographic terrains traditionally recognized in the Betic and Rif chains belong to four pre-Neogene crustal domains: the South-Iberian and Maghrebian passive continental paleomargins (External Zones of the orogen), the Flysch Units, and the Alborân Crustal Domain composed mainly of a pre- Miocene metamorphosed thrust-stack (Nevado-Filabride, Alpujârride, and Malaguide complexes, from bottom to top). The boundaries between the main metamorphic complexes of the Alborân Domain are extensional detachments, which finally developed under brittle conditions and are commonly sealed by middle-to-late Miocene marine-to-continental sediments. They, nonetheless, are not the most recent structures in the Alborân Domain, because upright, E-W open folds warp the extensional detachments, and finally, high-angle normal faults and strike-slip faults, many of which are still active, offset folds and extensional detachments. The tectonic evolution of the Betic Alborân orogenic system shows close similarities with the one depicted in other arcuate-shaped, Alpine mountain ranges in the Mediterranean, such as the Hellenic Arc and the Aegean Sea. Like in the westernmost Mediterranean, a thickened (pre Miocene) crust is bounding there a thinned, continental (?) basin. Extension is also formed here in a "back-arc" setting, being developed simultaneously with the N-S convergence between the African and European plates.
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Long, Sean P., and Matthew J. Kohn. "Distributed ductile thinning during thrust emplacement: A commonly overlooked exhumation mechanism." Geology 48, no. 4 (January 31, 2020): 368–73. http://dx.doi.org/10.1130/g47022.1.
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Abstract Quantifying the processes that control exhumation is essential for understanding the evolution of mountain belts. In the Cordilleran orogen in Nevada (western United States), rocks exhumed in the Ruby–East Humboldt metamorphic core complex underwent 4 ± 2 kbar of decompression between 85 and 60 Ma, which has been interpreted as a consequence of synorogenic extension. However, evidence for significant normal faulting in this region prior to 45 Ma is lacking. Here, we present an alternative interpretation: that this decompression can be attributed to distributed ductile thinning (DDT) of mid-crustal metamorphic rocks above the basal Cordilleran décollement during eastward translation. Such a process has been documented within the Himalayan Main Central thrust sheet, which locally accommodated up to 15 km of DDT during Miocene translation. Other examples of DDT have been documented in the Alpine and Caledonian orogens (Europe), and the Sanbagawa belt (Japan). DDT may represent a widespread exhumation process that can account for a significant portion of the decompression path of deeply exhumed rocks. As a condition of strain compatibility, thrust-parallel stretching accompanying DDT is expected to enhance displacement magnitude in the transport direction, and is therefore an important component of the deformation field that must be considered for accurate assessment of mass balance in thrust systems.
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Wagner, T., and N. J. Cook. "Late-orogenic alpine-type (apatite)-quartz fissure vein mineralization in the Rheinisches Schiefergebirge, NW Germany: mineralogy, formation conditions and lateral-secretionary origin." Mineralogical Magazine 64, no. 3 (June 2000): 539–60. http://dx.doi.org/10.1180/002646100549418.
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AbstractMineralogical, geochemical and fluid inclusion investigations of a representative suite of fissure vein mineralizations in the Rheinisches Schiefergebirge, NW Germany indicate a link to the latest stage of the Variscan orogenic evolution. Model P-T-conditions during initiation of fibrous fissure vein quartz growth are in the range 370–420°C at 0.2–0.7 kbar. The dataset suggests significant fluid cooling during evolution of the vein systems. Minimum temperatures at the end of fibrous quartz growth lie in the range 140–190°C, with conductive heat transfer and heat consumption during interaction with wallrock believed to be the main mechanisms responsible. Wallrock alteration is characterized by leaching and mobilization of most of the dominant vein components (quartz, albite, apatite), notably Si, Na and P. The principal stage of vein formation is, on the basis of available data, believed to relate to a process of intra-formational redistribution or lateral secretion. However, part of those elements deposited both in wallrock and fissure veins were probably supplied directly by the external fluid. Rates of fissure opening and material deposition were in equilibrium during the principal growth stage of fibrous quartz. However, this situation evolved due to a slowing down of material supply and deposition coupled with an increased rate of fissure opening to produce open fissures and formation of idiomorphic quartz crystals within them. Deposition depths were in the range of 0.6–2.1 km, appreciably lower than estimations of overburden. We believe therefore that formation of the fissure vein systems took place along the retrograde late–orogenic exhumation path, in a transitional stage between Variscan collision and a late- to post-orogenic extensional regime. Fluid composition characteristics also strongly suggest a relationship to the latest stages of the Variscan mineralization cycle in which low–salinity brines dominate. Development of fissure vein systems during the latest stages of continental collision, identified here from the Variscan orogeny, can be considered analogous with similar phenomena in the Alpine orogenic belt.
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Célini, Naïm, Jean-Paul Callot, Jean-Claude Ringenbach, and Rodney Graham. "Anatomy and evolution of the Astoin diapiric complex, sub-Alpine fold-and-thrust belt (France)." BSGF - Earth Sciences Bulletin 192 (2021): 29. http://dx.doi.org/10.1051/bsgf/2021018.
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The structure of the southwestern branch of the Alpine orogen is affected by the extensive Late Triassic evaporites. These evaporites have been involved in polyphased salt tectonics since the early Liassic, coeval with the Tethyan rifting, and are the décollement level for thrusts in the external parts during Alpine orogeny. The role of salt tectonics in this branch of the Alpine arc is re-evaluated in order to determine the relative importance of early deformation related to salt motion with respect to deformation related to main Alpine compressional events. This paper focuses on one structure identified as diapiric since the 1930’s: the Astoin diapir (Goguel, 1939). Analysis of geological maps together with new field work have allowed to better define diapirism in the Upper Triassic evaporites outcrops around Astoin. Study of the diapir and the surrounding depocenters reveals a major involvement of salt in the structuration of the area, since the Liassic. Several salt ridges are linked to a main diapiric structure, explaining why we call it the “diapiric complex” of Astoin. Salt tectonics was initiated during the Liassic rifting, and a few locations show evidence of reactive diapirism whereas in others evidence of passive diapirism as early as the Liassic is seen. Passive diapirism continued during the post-rift stage of Alpine margin history in the Late Jurassic and Cretaceous when an allochthonous salt sheet was emplaced. Diapirism also occurred during the Oligocene while the Alpine foreland basin was developing in this part of the European margin of the Alps. Serial interpretative cross-sections have been drawn in order to illustrate the lateral variations of diapirism and structural style. Sequential evolutions for each cross-section are proposed to reconstruct the diapiric complex evolution through time. The Astoin diapir shows a complex structural framework with an important along-strike variation of diapiric activity. Most of the geometries are inherited from salt tectonics that occurred during extension, and in some places these early structures are overprinted by Alpine compressional structures.
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Mock, Samuel, Christoph von Hagke, Fritz Schlunegger, István Dunkl, and Marco Herwegh. "Long-wavelength late-Miocene thrusting in the north Alpine foreland: implications for late orogenic processes." Solid Earth 11, no. 5 (October 13, 2020): 1823–47. http://dx.doi.org/10.5194/se-11-1823-2020.
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Abstract. In this paper, we present new exhumation ages for the imbricated proximal molasse, i.e. Subalpine Molasse, of the northern Central Alps. Based on apatite (U-Th-Sm)/He thermochronometry, we constrain thrust-driven exhumation in the Subalpine Molasse between 12 and 4 Ma. This occurs synchronously to the main deformation in the adjacent Jura fold-and-thrust belt farther north and to the late stage of thrust-related exhumation of the basement massifs (i.e. external crystalline massifs) in the hinterland. Our results agree with other findings along the north Alpine foreland. While site-specific variations in the mechanical stratigraphy of the molasse deposits influence the pattern of thrusting at the local scale, we observe that late-Miocene thrusting is a long-wavelength feature occurring along the north Alpine foreland roughly between Lake Geneva and Salzburg. The extent of this thrusting signal as well as the timing suggests that late-Miocene thrusting in the north Alpine foreland coincides with the geometries and dynamics of the attached Central Alpine slab at depth. Interestingly, this implies that the slab geometry at depth does not coincide with the boundary between the Eastern and Central Alps as observed in the surface geology. Using this observation, we propose that thrusting in the Subalpine Molasse and consequently also the late stage of thrust-related exhumation of the external crystalline massifs, as well as the main deformation in the Jura fold-and-thrust belt are at least partly linked to changes in slab dynamics.
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Ring, U., K. Gessner, S. Thomson, and V. Markwitz. "Along-strike variations in the Hellenide Anatolide orogen: A tale of different lithospheres and consequences." Bulletin of the Geological Society of Greece 47, no. 2 (January 24, 2017): 625. http://dx.doi.org/10.12681/bgsg.11096.
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Structure and exhumation history of the Hellenide-Anatolide Orogen in the Aegean Sea region and the adjacent Anatolian peninsula is controlled by along-strike variations of pre-Alpine palaeogeography. In the Hellenides, Mesozoic extension created ribbon-like continental fragments of thinned and dense lithosphere that pinch out eastwards. In the east, the relatively large Anatolide microcontinent mostly escaped Mesozoic extension and lithospheric thinning, presumably because it had a distinctly different, thicker and more depleted lithosphere. In the Aegean transect these alongstrike differences in lithosphere structure ultimately resulted in sustained highpressure metamorphism followed by progressive slab retreat since about 60 Ma. Further east, collision of the Anatolide microcontinent at about 42 Ma formed a south verging greenschist-facies thrust-and-fold belt. Pronounced slab retreat in the Aegean forced differential extension resulting in a broad sinistral wrench corridor that started to from at 24-23 Ma. Since then, extension in both regions mainly controlled denudation. This review highlights how differences in pre-orogenic architecture control lithospheric thickening and the subsequent exhumation of high-pressure rocks, and how large-scale continental extension evolves
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SHAKED, YONATHAN, DOV AVIGAD, and ZVI GARFUNKEL. "Alpine high-pressure metamorphism at the Almyropotamos window (southern Evia, Greece)." Geological Magazine 137, no. 4 (July 2000): 367–80. http://dx.doi.org/10.1017/s001675680000426x.
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The Alpine orogenic belt of the Hellenides has been strongly reworked by ductile and brittle extensional tectonics. Extensional structures have affected the central Aegean region and obliterated much of the original orogenic architecture since at least early Miocene times. In the area of Almyropotamos (on the island of Evia, flanking the western part of the Aegean) a unique remnant compressional nappe stack involving Tertiary metamorphic rocks has been preserved. This nappe sequence comprises a high-pressure rock unit on top of a lower grade unit. The upper unit (South Evia Blueschist Belt) is thought to be the westward continuation of the Cycladic blueschist belt metamorphosed at high-pressure conditions during Late Cretaceous–Eocene times. The underlying unit (the Almyropotamos Unit) is a continental margin sequence covered by a flysch and containing Lutetian nummulites, indicating that this unit accumulated sediments until at least late Eocene times.In the present study we analyse the petrology of the Almyropotamos nappe stack and define the P–T conditions of each of the different rock units exposed there. The presence of glaucophane, lawsonite rimmed by epidote, and jadeite (70 mol.%) suggest that peak P–T conditions in the South Evia Blueschist Belt reached approximately 10–12 kbar and 350–450 °C. Unlike previous studies, which estimated that the underlying Almyropotamos Unit reached only greenschist-facies conditions, glaucophane relics and Si-rich phengites were found by us in this unit. These indicate that high-pressure metamorphism and crustal thickening in this part of the Aegean lasted until at least the late Eocene or early Oligocene. We note that in this respect the architecture of southern Evia resembles that of northern Greece (Olympos, Ossa). Our structural data indicate that rock units in the Almyropotamos area record different folding phases, with the South Evia Blueschist Belt having a more complex fold history than the underlying Almyropotamos Unit. The entire nappe stack shares large-scale folds which are E–W trending, and locally overturned-to-the-south, and which may represent (at present coordinates) N–S contraction and nappe transport.
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Vanderhaeghe, Olivier, and Alexia Grabkowiak. "Tectonic accretion and recycling of the continental lithosphere during the Alpine orogeny along the Pyrenees." Bulletin de la Société Géologique de France 185, no. 4 (April 1, 2014): 257–77. http://dx.doi.org/10.2113/gssgfbull.185.4.257.
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Abstract The goal of this paper is to identify the fate of the continental lithosphere along the Iberia-Eurasia convergent plate boundary marked by the formation of the Pyrenean orogenic belt. The present-day volumes of crust and lithosphere beneath the Pyrenees and the volume of eroded crust redistributed in neighbo ring basins are evaluated based on a synthesis of available geological and geophysical data. The volumes that are expected to have transited across the former plate boundary are modeled taking into account Iberia-Eurasia convergence and making assumptions regarding the initial lithospheric and crustal structure of the Iberia-Eurasia plate boundary at the onset of continental collision (~83 Ma). Despite large uncertainties, the difference between the initial and present-day lithospheric structures suggests that at 83 Ma, either the Iberia-Eurasia plate boundary was marked by a zone of thinned lithosphere (oceanic and/or continental), or the lithosphere having transited across the plate boundary has for the most part been recycled into the mantle. At the crustal-scale, the volume of tectonically accreted crust is estimated by adding the volume of crust currently present in the Pyrenean orogenic belt to the volume of sediments deposited in neighboring basins, and by subtracting the initial volume of crust at the onset of continental collision considering two end-members, namely (i) a continental rift or (ii) a 35 km wide oceanic basin. In both cases, this tectonically accreted crustal volume is not enough to match the calculated volume of crust that has potentially transited across the plate boundary as a consequence of convergence since 83 Ma. As a result, our computation suggests that at least 30% (and as much as 63%) of the continental crust has subducted with the Iberian lithospheric slab and has been recycled into the mantle. In addition, the synthesis of topographic and geophysical (gravity and seismic tomography) reveals a peculiar crustal and lithospheric scale structure for the current day Pyrenees characterized by (i) an elliptical-cone-shape Pyrenean mountain range underlain by an elliptical-cone-shaped crustal root pointing down, and (ii) two tongues of lithospheric mantle in the central part of the belt. These features are interpreted as reflecting redistribution of the lithospheric mantle and of the orogenic crust by ductile flow after subduction and tectonic accretion. We propose that following a period of subduction/collision from 83 to 35 Ma, the decrease in the convergence rate between Iberia-Eurasia favored thermal relaxation of the Iberian slab promoting ductile flow and the development of gravitational instabilities. We suggest that the orogenic root has been dragged down by the dense lithospheric root and that part of it has been recycled into the mantle. In this view, the current-day lithospheric tongues represent the remnants of the lithospheric root after thermal relaxation and recycling by convective removal.
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von Gosen, W. "Fabric developments and the evolution of the Periadriatic Lineament in southeast Austria." Geological Magazine 126, no. 1 (January 1989): 55–71. http://dx.doi.org/10.1017/s0016756800006142.
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AbstractThe Periadriatic Lineament Zone which forms the boundary between the Eastern and Southern Alps in the Karawanken region of Austria has a complex history spanning the Variscan and Alpine orogenies. Variscan regional metamorphism and polyphase deformation followed by Late to Post Variscan intrusive activity with accompanying contact metamorphism affects a belt of structurally complex rocks referred to as the Eisenkappel Zone to the north of the lineament. Weak Early Alpine deformation in the Southern Alpine rocks can also be recognized in the Eisenkappel Zone. The Young Alpine intrusion of the Karawanken Tonalite was followed by lateral fault displacements associated with the formation of the Periadriatic Lineament. Late Tertiary sediments, caught up in the northward directed thrusting responsible for the uplift of the Karawanken chain, record the youngest deformation in the area.
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de Boorder, H., W. Spakman, S. H. White, and M. J. R. Wortel. "Late Cenozoic mineralization, orogenic collapse and slab detachment in the European Alpine Belt." Earth and Planetary Science Letters 164, no. 3-4 (December 1998): 569–75. http://dx.doi.org/10.1016/s0012-821x(98)00247-7.
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VIGNAROLI, GIANLUCA, FEDERICO ROSSETTI, THOMAS THEYE, and CLAUDIO FACCENNA. "Styles and regimes of orogenic thickening in the Peloritani Mountains (Sicily, Italy): new constraints on the tectono-metamorphic evolution of the Apennine belt." Geological Magazine 145, no. 4 (February 6, 2008): 552–69. http://dx.doi.org/10.1017/s0016756807004293.
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AbstractThe Peloritani Mountains constitute the Sicilian portion of the Calabria–Peloritani Arc (Italy), a tectono-metamorphic edifice recording the history of the subduction–exhumation cycle during Tertiary convergence between the African and European plates. Here, we describe the kinematic and the petrological characteristics of the major shear zones bounding the lowermost continental-derived metamorphic units cropping out in the eastern portion of the Peloritani Mountains. Both meso- and micro-scale shear sense criteria indicate a top-to-the-SSE tectonic transport, during a general evolution from ductile to brittle deformation conditions. Quantitative thermobarometry on texturally equilibrated phengite–chlorite pairs crystallized along the shear bands indicates pressure of 6–8 kbar at temperatures of 360–440 °C for the structurally highest units and 3–4 kbar at 380–440 °C for the lowest ones. This documents an overall inverse-type nappe arrangement within the tectonic edifice and a transition from an Alpine- (13–18 °C km−1) to a Barrovian-type (28–36 °C km−1) geothermal gradient during the progress of the Alpine orogenic metamorphism in the Peloritani Mountains. The integration of these results allows the Peloritani Mountains to be considered as a constituent element of the Apennine orogenic domain formed during the progressive space–time transition from oceanic to continental subduction at the active convergent margin.
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Michard, André, Ahmed Chalouan, Hugues Feinberg, Bruno Goffé, and Raymond Montigny. "How does the Alpine belt end between Spain and Morocco ?" Bulletin de la Société Géologique de France 173, no. 1 (January 1, 2002): 3–15. http://dx.doi.org/10.2113/173.1.3.
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Abstract The Betic-Rif arcuate mountain belt (southern Spain, northern Morocco) has been interpreted as a symmetrical collisional orogen, partly collapsed through convective removal of its lithospheric mantle root, or else as resulting of the African plate subduction beneath Iberia, with further extension due either to slab break-off or to slab retreat. In both cases, the Betic-Rif orogen would show little continuity with the western Alps. However, it can be recognized in this belt a composite orocline which includes a deformed, exotic terrane, i.e. the Alboran Terrane, thrust through oceanic/transitional crust-floored units onto two distinct plates, i.e. the Iberian and African plates. During the Jurassic-Early Cretaceous, the yet undeformed Alboran Terrane was part of a larger, Alkapeca microcontinent bounded by two arms of the Tethyan-African oceanic domain, alike the Sesia-Margna Austroalpine block further to the northeast. Blueschist- and eclogite-facies metamorphism affected the Alkapeka northern margin and adjacent oceanic crust during the Late Cretaceous-Eocene interval. This testifies the occurrence of a SE-dipping subduction zone which is regarded as the SW projection of the western Alps subduction zone. During the late Eocene-Oligocene, the Alkapeca-Iberia collision triggered back-thrust tectonics, then NW-dipping subduction of the African margin beneath the Alboran Terrane. This Maghrebian-Apenninic subduction resulted in the Mediterranean basin opening, and drifting of the deformed Alkapeca fragments through slab roll back process and back-arc extension, as reported in several publications. In the Gibraltar area, the western tip of the Apenninic-Maghrebian subduction merges with that of the Alpine-Betic subduction zone, and their Neogene roll back resulted in the Alboran Terrane collage astride the Azores-Gibraltar transpressive plate boundary. Therefore, the Betic-Rif belt appears as an asymmetrical, subduction/collision orogen formed through a protracted evolution straightfully related to the Alpine-Apenninic mountain building.
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Allemand, Pascal, and Jean-Marc Lardeaux. "Strain partitioning and metamorphism in a deformable orogenic wedge: Application to the Alpine belt." Tectonophysics 280, no. 1-2 (October 1997): 157–69. http://dx.doi.org/10.1016/s0040-1951(97)00136-4.
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Trifonov, V. G., and S. Yu Sokolov. "Structure of the mantle and tectonic zoning of the central Alpine-Himalayan belt." Geodynamics & Tectonophysics 9, no. 4 (December 9, 2018): 1127–45. http://dx.doi.org/10.5800/gt-2018-9-4-0386.
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The Alpine-Himalayan orogenic belt is characterized by longitudinal zoning and transverse segmentation. Using the 3D seismic tomography model, we compiled the sections showing the deviations of seismic P-wave velocities from the average values in the mantle, and analyzed the sections in comparison with the data on the crustal inhomogeneities expressed in geological structures. The sections go across of the central part of the belt from Adriatic to Western Tien Shan, Pamirs, Western Himalayas, and the adjacent territories of the East African rift system, the Arabian, Turanian and Scythian plates, and the East European platform. Our model based on the seismic tomography data is mainly targeted at studying the inhomogeneities in the upper mantle, considering the fact that the resolution of mantle differentiation in terms of P-waves is higher in the upper mantle than in the lower one. Based on the analysis of the sections, we determine the directions of seismically low-velocity upper-mantle flows spreading from the Ethiopian-Afar super-plume, which differ in intensity. The relationships are revealed between these flows and the high-velocity bodies that are subsided into the mantle due to subduction and collision of the plates. The deep-seated features that give evidence of transverse segmentation of the belt are detected.
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Zouhri, Lahcen, Christian Lamouroux, Daniel Vachard, and Alain Pique. "Evidence of flexural extension of the Rif foreland: The Rharb-Mamora basin (northern Morocco)." Bulletin de la Société Géologique de France 173, no. 6 (November 1, 2002): 509–14. http://dx.doi.org/10.2113/173.6.509.
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Abstract The Rharb-Mamora basin is the foreland of the Rif Cordillera (orogenic belt). The Mamora area (northern Morocco) is located at the southern border of the Rharb basin and intercalated between the Alpine Rif Mountains to the north and the Hercynian Moroccan Meseta domain to the south. Analysis and interpretation of seismic lines, hydrogeological and oil wells, have allowed to precise the major structural elements of the Mamora area, which is covered by late Neogene sediments. The structure of the area is controlled by faults that also affect the Paleozoic basement. The NE-SW and NW-SE trending faults induce the palaeogeographical evolution and control, the facies distribution and the thickness variations. The most important or relevant structural feature of the Mamora area is the Kenitra-Sidi-Slimane fault (K2SF) [Zouhri et al., 2001]. This fault N110oE trending is south of the Rif Alpine thrust front and is marked by a progressive deepening of its northern compartment, at least since Cretaceous time. Thus the Mamora appears as a hinge between the Rharb Basin and the Moroccan Meseta from Cretaceous to Neogene time.
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Chalouan, Ahmed, Andre Michard, Hugues Feinberg, Raymond Montigny, and Omar Saddiqi. "The Rif mountain building (Morocco); a new tectonic scenario." Bulletin de la Société Géologique de France 172, no. 5 (September 1, 2001): 603–16. http://dx.doi.org/10.2113/172.5.603.
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Abstract The building of the Alpine Rif belt (southern limb of the Betic-Rif orocline) is restored, mostly based on the Tertiary stratigraphic and metamorphic data set. The Betic-Rif Internal zones derive from an exotic Alboran Terrane partly involved in a S-dipping Betic subduction during the Late Cretaceous ?-Eocene. Incipient collision of the terrane against Iberia triggered back-thrust tectonics south of the Internal mountain belt during the latest Eocene-Oligocene. A N-dipping Maghrebian subduction developed from that time up to Middle Miocene, responsible for the rifting of the internal Alboran Terrane. Docking of the extending Alboran Terrane onto the North African margin occurred during the Neogene through the closure of the Maghrebian Flysch oceanic trough, with southwestward growth of the external accretionary prism, and foredeep subsidence. Subduction zone westward roll back associated with delamination of the dense lithosphere seem to account for the Betic-Rif late orogenic evolution.
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CHEN, ZHONG-QIANG, XIANGDONG WANG, BARRY RICHARDS, and MARKUS ARETZ. "Multidisciplinary studies of global Carboniferous stage boundaries: towards a better definition and global correlations: an introduction." Geological Magazine 151, no. 2 (February 13, 2014): 199–200. http://dx.doi.org/10.1017/s0016756813001155.
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Earth was very dynamic during the Carboniferous with major components of the Pangea supercontinent being assembled from late Famennian to latest Pennsylvanian times, although maximum consolidation occurred during Late Permian – Early Triassic time. During the Carboniferous Period, our planet also underwent at least three major icehouse periods. The first two, in late Famennian – early Tournaisian and late Visean – Bashkirian times, indicate the onset of the Late Palaeozoic Ice Age (LPIA) with ice sheets being confined to the alpine regions of southern Gondwana. The third icehouse regime during Gzhelian – Early Permian time represents the main episode of the LPIA when a continental ice sheet developed on the Australian, Antarctic and southern African components of southern Gondwana. During the Tournaisian equatorial areas in Euramerica were occupied by extensive arid belts, in which massive carbonate deposits formed on vast platforms in that time. From the late Tournaisian into the Visean and Serpukhovian much of the equatorial belt developed into a humid-tropical realm and the former arid belt split and shifted to higher latitudes. Shelf-carbonate deposition continued over extensive areas of the continental shelves and western Palaeo-Tethys but coal swamps were developing in the forelands of the rising Appalachian and Variscan orogens. The late Serpukhovian – early Bashkirian interval saw the closure of the Rheic Ocean and a continent–continent collision between Euramerica (Laurussia) and Gondwana to form Pangea. As a consequence, a marked transition from Visean carbonate deposition to the development of coal swamps and deposition of siliciclastics during the Serpukhovian Stage occurred in many regions.
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Unal, M., and C. Uslu. "GIS-BASED ACCESSIBILITY ANALYSIS OF URBAN EMERGENCY SHELTERS: THE CASE OF ADANA CITY." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W1 (October 26, 2016): 95–101. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w1-95-2016.
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Accessibility analysis of urban emergency shelters can help support urban disaster prevention planning. Pre-disaster emergency evacuation zoning has become a significant topic on disaster prevention and mitigation research. In this study, we assessed the level of serviceability of urban emergency shelters within maximum capacity, usability, sufficiency and a certain walking time limit by employing spatial analysis techniques of GIS-Network Analyst. The methodology included the following aspects: the distribution analysis of emergency evacuation demands, the calculation of shelter space accessibility and the optimization of evacuation destinations. This methodology was applied to Adana, a city in Turkey, which is located within the Alpine-Himalayan orogenic system, the second major earthquake belt after the Pacific-Belt. It was found that the proposed methodology could be useful in aiding to understand the spatial distribution of urban emergency shelters more accurately and establish effective future urban disaster prevention planning. Additionally, this research provided a feasible way for supporting emergency management in terms of shelter construction, pre-disaster evacuation drills and rescue operations.
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Koulakov, Ivan, Sergey Tychkov, Natalia Bushenkova, and Alexander Vasilevsky. "Structure and dynamics of the upper mantle beneath the Alpine–Himalayan orogenic belt, from teleseismic tomography." Tectonophysics 358, no. 1-4 (November 2002): 77–96. http://dx.doi.org/10.1016/s0040-1951(02)00418-3.
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Vozárová, Anna, Sergey Presnyakov, Katarína Šarinová, and Miloš Šmelko. "First evidence for Permian-Triassic boundary volcanism in the Northern Gemericum: geochemistry and U-Pb zircon geochronology." Geologica Carpathica 66, no. 5 (October 1, 2015): 375–91. http://dx.doi.org/10.1515/geoca-2015-0032.
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AbstractSeveral magmatic events based on U-Pb zircon geochronology were recognized in the Permian sedimentary succession of the Northern Gemeric Unit (NGU). The Kungurian magmatic event is dominant. The later magmatism stage was documented at the Permian-Triassic boundary. The detrital zircon assemblages from surrounding sediments documented the Sakmarian magmatic age. The post-orogenic extensional/transtensional faulting controlled the magma ascent and its emplacement. The magmatic products are represented by the calc-alkaline volcanic rocks, ranging from basaltic metaandesite to metarhyolite, associated with subordinate metabasalt. The whole group of the studied NGU Permian metavolcanics has values for the Nb/La ratio at (0.44–0.27) and for the Nb/U ratio at (9.55–4.18), which suggests that they represent mainly crustal melts. Magma derivation from continental crust or underplated crust is also indicated by high values of Y/Nb ratios, ranging from 1.63 to 4.01. The new206U–238Pb zircon ages (concordia age at 269 ± 7 Ma) confirm the dominant Kungurian volcanic event in the NGU Permian sedimentary basin. Simultaneously, the Permian-Triassic boundary volcanism at 251 ± 4 Ma has been found for the first time. The NGU Permian volcanic activity was related to a polyphase extensional tectonic regime. Based on the new and previous U-Pb zircon ages, the bulk of the NGU Permian magmatic activity occurred during the Sakmarian and Kungurian. It was linked to the post-orogenic transpression/transtension tectonic movements that reflected the consolidation of the Variscan orogenic belt. The Permian-Triassic boundary magmatism was accompanied by extension, connected with the beginning of the Alpine Wilson cycle.
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Butler, R. W. H., S. J. Matthews, and M. Parish. "The NW external Alpine Thrust Belt and its implications for the geometry of the Western Alpine Orogen." Geological Society, London, Special Publications 19, no. 1 (1986): 245–60. http://dx.doi.org/10.1144/gsl.sp.1986.019.01.14.
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Hnylko, O. M. "GEODYNAMICS." GEODYNAMICS 1(10)2011, no. 1(10) (June 28, 2011): 47–57. http://dx.doi.org/10.23939/jgd2011.01.047.
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The tectonic units of the Carpathians are considered in terms of the terrain analysis. Carpathathian orogen is build up of three main elements: microcontinental terrains, sutures and flysch-molasse accretionary prism. There are two main terrains: a northern ALCAPA and a southern Tisza-Dacia. Sutures (Fore-Marmarosh suture, Pieniny Klippen Belt and others), marking the ancient oceanic basins, bound these terrains. The Flysch Carpathians are regarded as the Cretaceous-Neogene accretionary prism. Growing the prism was caused by the Alpine subduction of the Carpathian Flysch basin basement beneath both the ALCAPA and Tisza-Dacia terrains.
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Doroozi, Roghieh, Carmela Vaccaro, and Fariborz Masoudi. "Mesozoic alkaline plutonism: Evidence for extensional phase in Alpine-Himalayan orogenic belt in Central Alborz, north Iran." Solid Earth Sciences 2, no. 4 (December 2017): 91–108. http://dx.doi.org/10.1016/j.sesci.2017.07.001.
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Storetvedt, K. M. "The Tethys Sea and the Alpine-Himalayan orogenic belt; mega-elements in a new global tectonic system." Physics of the Earth and Planetary Interiors 62, no. 1-2 (January 1990): 141–84. http://dx.doi.org/10.1016/0031-9201(90)90198-7.
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Somma, Roberta, Antonia Messina, and Stefano Mazzoli. "Syn-orogenic extension in the Peloritani Alpine Thrust Belt (NE Sicily, Italy): Evidence from the Alì Unit." Comptes Rendus Geoscience 337, no. 9 (July 2005): 861–71. http://dx.doi.org/10.1016/j.crte.2005.03.004.
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