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Luca Pandolfi - One of the best experts on this subject based on the ideXlab platform.
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Deformation History of the eclogite‐ and jadeitite‐bearing mélange from North Motagua Fault Zone, Guatemala: insights in the processes of a fossil subduction channel
Geological Journal, 2009Co-Authors: Michele Marroni, Luca Pandolfi, Gianfranco Principi, Alessandro Malasoma, Francesca MeneghiniAbstract:In Guatemala, along the northern side of the Motagua Valley, a melange consisting of blocks of eclogite and jadeitite set in a metaserpentinitic and metasedimentary matrix crops out. The metasedimentary rocks display a complex Deformation History that includes four tectonic phases, from D1 to D4. The D1 phase occurs only as a relic and is characterized by a mineral assemblage developed under pressure temperature (P-T) conditions of 1.00-1.25 GPa and 206-2638C. The D2 phase, characterized by isoclinal folds, schistosity and mineral/stretching lineation, developed at P-T conditions of 0.70-1.20 GPa and 279-4098C. The following D3 and D4 phases show Deformations developed at shallower structural levels. Whereas the D1 phase can be interpreted as the result of underplating of slices of oceanic lithosphere during an intraoceanic subduction, the following phases have been acquired by the melange during its progressive exhumation through different mechanisms. The Deformations related to the D2 and D3 phases can be regarded as acquired by extrusion of the melange within a subduction channel during a stage of oblique subduction. In addition, the structural evidences indicate that the coupling and mixing of different blocks occurred during the D2 phase, as a result of flow reverse and upward trajectory in the subduction channel. By contrast, the D4 phase can be interpreted as related to extension at shallow structural levels. In this framework, the exhumation- related structures in the melange indicate that this process, probably long-lived, developed through different mechanisms, active in the subduction channel through time. Copyright # 2009 John Wiley & Sons, Ltd.
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Polyorogenic Deformation History recognized at very shallow structural levels: the case of the Antola Unit (Northern Apennine, Italy)
Journal of Structural Geology, 2006Co-Authors: N. Levi, Alessandro Ellero, Giuseppe Ottria, Luca PandolfiAbstract:Abstract The Antola Unit is a Ligurian Unit occurring at the top of the nappe pile of the Northern Apennines (Italy). Structural analysis indicates that the Antola Unit has been involved in a complex polyphase Deformation History developed at a shallow structural level. The successive Deformation phases belong to both the Alpine and Apenninic orogenic cycles. Therefore the Antola Unit is a good example of a polyorogenic tectonic unit deformed at a very shallow structural level. The older part of the structural evolution is assigned to the Meso-Alpine tectonic stage and consists of two Deformation phases (D1 and D2) characterized by opposite tectonic transport directions. The D1 and D2 structures were sealed by the middle Eocene-Miocene deposits of the Tertiary Piedmont Basin. The younger part of the Deformation History instead can be referred to the Northern Apennines tectonics, and consists of two phases (D3 and D4) both involving the Tertiary Piedmont Basin succession. The structural data indicate that the D1 Deformations developed in mostly unlithified rocks, and that these structures can be related to the westward emplacement of the Antola Unit in the Alpine orogenic wedge. The D2 phase is characterized by folds and low-angle extensional faults, and is referable to a gravity-driven Deformation. Both the D3 and D4 phases, characterized by folds and thrusts, are due to the compressive regime related to the development of the Northern Apennines.
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LITHOSTRATIGRAPHY AND Deformation History OF THE LAGO NERO UNIT (CHENAILLET MASSIF, WESTERN ALPS)
Ofioliti, 2004Co-Authors: N. Levi, Michele Marroni, Luca PandolfiAbstract:In the Western Alps, the Schistes Lustres includes ophiolitic units that, even if affected by HP metamorphism, are relatively poorly deformed. Among them, the Lago Nero unit displays a thick and well-developed sedimentary cover, that allows a comparison with the analogue successions of the Northern Apennines. This sedimentary cover includes hemipelagic deposits, represented by Radiolarite Fm., Metalimestone and Replatte Fm., showing a transition to turbiditic (Gondran Flysch) and mass-gravity deposits (Rocher Renard complex). This succession, characterized by a coarsening upward trend, records the approaching of an oceanic floor section to the accretionary wedge. In this picture, the Rocher Renard complex can be regarded as a formation related to a frontal erosion of the accretionary wedge, whereas the Gondran Flysch is interpreted as a turbidite deposits supplied by the continental margin of the Europe plate. The following Deformation History includes four Deformation phases. The first phase D1 Deformations, characterized by HP metamorphism (lawsonite±Na-amphibole±phengite), were achieved during the coherent underplating in the alpine subduction zone. The D2, D3 and D4 phases was developed under retrograde metamorphic conditions, from grren-schist to very-low grade, during the progressive exhumation of the Lago Nero unit. All the collected data suggest that the succession of the Lago Nero unit can be correlated with those of the Internal Liguride units where the same sequence of hemipelagic to turbiditic and mass-gravity deposits has been recognized.
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Deformation History of the ophiolite sequence from the Balagne Nappe, northern Corsica: insights in the tectonic evolution of Alpine Corsica
Geological Journal, 2003Co-Authors: Michele Marroni, Luca PandolfiAbstract:In Alpine Corsica, the Jurassic ophiolites represent remnants of oceanic lithosphere belonging to the Ligure-Piemontese Basin located between the Europe/Corsica and Adria continental margins. In the Balagne area, a Jurassic ophiolitic sequence topped by a Late Jurassic–Late Cretaceous sedimentary cover crops out at the top of the nappe pile. The whole ophiolitic succession is affected by polyphase Deformation developed under very low-grade orogenic metamorphic conditions. The original palaeogeographic location and the emplacement mechanisms for the Balagne ophiolites are still a matter of debate and different interpretations for its History have been proposed. The Deformation features of the Balagne ophiolites are outlined in order to provide constraints on their History in the framework of the geodynamic evolution of Alpine Corsica. The Deformation History reconstructed for the Balagne Nappe includes five different Deformation phases, from D1 to D5. The D1 phase was connected with the latest Cretaceous/Palaeocene accretion into the accretionary wedge related to an east-dipping subduction zone followed by a Late Eocene D2 phase related to emplacement onto the Europe/Corsica continental margin. The subsequent D3 phase was characterized by sinistral strike-slip faults and related Deformations of Late Eocene–Early Oligocene age. The D4 and D5 phases were developed during the Early Oligocene–Late Miocene extensional processes connected with the collapse of the Alpine belt. Copyright © 2003 John Wiley & Sons, Ltd.
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Deformation History of the blueschist-facies sequences from the Villa de Cura unit (Northern Venezuela)
Ofioliti, 2001Co-Authors: Alessandro Ellero, Michele Marroni, Elisa Padoa, Luca Pandolfi, Franco UrbaniAbstract:The Serrania del Interior terrane is located in Northern Venezuela, that represents the southern margin of the Caribbean plate. This terrane includes the Villa de Cura unit, which mainly consists of multiple sub-units of metamorphosed and deformed Cretaceous volcano-sedimentary sequences. These sequences are commonly interpreted as generated in a supra-subduction zone setting. The structural History of the Villa de Cura blueschists-facies units includes four main Deformational phases, from D1 to D4. The first D1 phase is mainly represented by a relict S1 schistosity developed under HP/LT conditions. The relic S1 schistosity is deformed by isoclinal to subisoclinal F2 folds showing similar geometry. The F2 folds are characterized by a continuous S2 crenulation cleavage developed under greenschist-facies metamorphism. The parallelism between the A2 axes and the related L2 mineral lineations suggests an interpretation of the F2 folds as sheath folds developed during non-coaxial Deformation. The kinematic indicators suggest a top-to-W sense of shear for the D2 phase. The D3 phase is distinguished by asymmetric, parallel F3 folds with a S vergence. Finally, the D4 phase consists of F4 open, gentle folds with high-angle to sub-vertical axial planes. The collected data suggest a complex Deformation History, characterized by coupling of strike-slip tectonics and shortening during the retrograde evolution of the blueschist-facies sequences.
Chunhui Song - One of the best experts on this subject based on the ideXlab platform.
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Cenozoic Deformation History of the Qilian Shan (northeastern Tibetan Plateau) constrained by detrital apatite fission-track thermochronology in the northeastern Qaidam Basin
Tectonophysics, 2018Co-Authors: Chunhui Song, Yadong Wang, Qingquan Meng, Lihao Chen, Lijie Yao, Ruohan Huang, Wei Feng, Shuo ChenAbstract:Abstract The Cenozoic Deformation History of the Qilian Shan, which is a reactivated fold-thrust belt in the northeastern region of the Tibetan Plateau, is poorly understood but features prominently in the geodynamic mechanism of the evolution of the plateau. The northeastern Qaidam Basin, which is located on the south flank of the Qilian Shan, provides a valuable record of the timing and pattern of the Cenozoic Deformation of the Qilian Shan in its synorogenic sediments. This study analyzes the apatite fission-track (AFT) thermochronological signatures of the middle Miocene-Quaternary detrital sediments in the northeastern Qaidam Basin and modern stream sands draining the Qilian Shan as a proxy for the timing of tectonic Deformation in the Qilian Shan. Our detrital AFT ages indicate that a Cenozoic initial rapid exhumation event occurred in the Qilian Shan in the late Paleocene-early Eocene (~60–54 Ma), followed by another rapid exhumation event during the middle-late Eocene (~42–38 Ma) and some exhumation during the Oligocene-middle Miocene (~33–14 Ma). Distinct changes in detrital AFT ages at depositional ages of ~12 Ma and ~2.1 Ma suggest that further tectonic Deformation affected the Qilian Shan at these times. Our results, along with those of previous studies, suggest that tectonic Deformation propagated into the northeastern edge of the Tibetan Plateau almost simultaneously with the India-Asia collision. The spatial evolution of Cenozoic Deformation in the Qilian Shan is likely based on the distribution of weak structures in the upper crust.
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cenozoic pulsed Deformation History of northeastern tibetan plateau reconstructed from fission track thermochronology
Tectonophysics, 2016Co-Authors: Xiuxi Wang, Chunhui Song, Massimiliano Zattin, Ai Song, Qiangqiang WangAbstract:Abstract The synorogenic basin deposits and bedrocks of their source terranes within and along the Tibetan Plateau contain fundamental information regarding the spatiotemporal evolution of the largest orogenic plateau on Earth. The Guide–Xining region is located on the northeastern portion of the Tibet and its Eocene–early Pleistocene basin succession is well preserved. By integrating apatite fission-track thermochronology from sedimentary and basement samples, with heavy minerals and paleocurrent data, we decipher an almost complete sequence of exhumation and depositional events during the Cenozoic. Our data indicates that the initial Deformation along the Guide–Xining region occurred since the Eocene, with the reorganization of the regional tectonomorphology and the formation of a broad basin. Thereafter, this single large basin was disrupted by multiple episodes of exhumation and Deformation. Our study illuminate that the multiple-stage active processes (occurred at 49–42, 36–32, 23–19, 16–13 and 8–4 Ma) work together to produce the current NE Tibetan Plateau.
Qiangqiang Wang - One of the best experts on this subject based on the ideXlab platform.
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cenozoic pulsed Deformation History of northeastern tibetan plateau reconstructed from fission track thermochronology
Tectonophysics, 2016Co-Authors: Xiuxi Wang, Chunhui Song, Massimiliano Zattin, Ai Song, Qiangqiang WangAbstract:Abstract The synorogenic basin deposits and bedrocks of their source terranes within and along the Tibetan Plateau contain fundamental information regarding the spatiotemporal evolution of the largest orogenic plateau on Earth. The Guide–Xining region is located on the northeastern portion of the Tibet and its Eocene–early Pleistocene basin succession is well preserved. By integrating apatite fission-track thermochronology from sedimentary and basement samples, with heavy minerals and paleocurrent data, we decipher an almost complete sequence of exhumation and depositional events during the Cenozoic. Our data indicates that the initial Deformation along the Guide–Xining region occurred since the Eocene, with the reorganization of the regional tectonomorphology and the formation of a broad basin. Thereafter, this single large basin was disrupted by multiple episodes of exhumation and Deformation. Our study illuminate that the multiple-stage active processes (occurred at 49–42, 36–32, 23–19, 16–13 and 8–4 Ma) work together to produce the current NE Tibetan Plateau.
N. Levi - One of the best experts on this subject based on the ideXlab platform.
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Polyorogenic Deformation History recognized at very shallow structural levels: the case of the Antola Unit (Northern Apennine, Italy)
Journal of Structural Geology, 2006Co-Authors: N. Levi, Alessandro Ellero, Giuseppe Ottria, Luca PandolfiAbstract:Abstract The Antola Unit is a Ligurian Unit occurring at the top of the nappe pile of the Northern Apennines (Italy). Structural analysis indicates that the Antola Unit has been involved in a complex polyphase Deformation History developed at a shallow structural level. The successive Deformation phases belong to both the Alpine and Apenninic orogenic cycles. Therefore the Antola Unit is a good example of a polyorogenic tectonic unit deformed at a very shallow structural level. The older part of the structural evolution is assigned to the Meso-Alpine tectonic stage and consists of two Deformation phases (D1 and D2) characterized by opposite tectonic transport directions. The D1 and D2 structures were sealed by the middle Eocene-Miocene deposits of the Tertiary Piedmont Basin. The younger part of the Deformation History instead can be referred to the Northern Apennines tectonics, and consists of two phases (D3 and D4) both involving the Tertiary Piedmont Basin succession. The structural data indicate that the D1 Deformations developed in mostly unlithified rocks, and that these structures can be related to the westward emplacement of the Antola Unit in the Alpine orogenic wedge. The D2 phase is characterized by folds and low-angle extensional faults, and is referable to a gravity-driven Deformation. Both the D3 and D4 phases, characterized by folds and thrusts, are due to the compressive regime related to the development of the Northern Apennines.
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THE POLYPHASE Deformation History OF THE ANTOLA UNIT (NORTHERN APENNINE, ITALY)
Ofioliti, 2004Co-Authors: N. Levi, Alessandro ElleroAbstract:The Antola Unit (AU) occurs at the top of the Northern Apenninic nappe pile, cropping out in the area regarded as the boundary between Alpine and Apenninic units. The relationships among all these units are sealed by the Tertiary Piedmont Basin (TPB) (Late Eocene-Miocene). The AU is characterized by a succession that consists of an Helmintoid Flysch, correlated to the External Ligurian successions. The first part of the AU Deformation History represents the Early to Middle Eocene Meso-Alpine tectonics, related to closure of the Ligure-Piemontese oceanic basin and the subsequent continental collision; the second one is related to the reactivation of the Meso-alpine structures during the Late Oligocene-Early Miocene. The first Deformation phase (D1) is characterized by structures, as for example folds and boudinage, affecting mostly the base of the AU and showing features indicative of soft-sediment conditions. All these structures are deformed by a folding phase (D2) characterized by the development of sub-isoclinal folds and extensional tectonic contacts. The structures related to the D1 and D2 tectonic phases are sealed by the TPB deposits. The third Deformation phase (D3), affecting also the TPB deposits (Early Oligocene), is characterized by the development of open, asymmetric, overturned folds with sub-horizontal axial planes. The axes orientation is strongly variable, with foldfacing ranging from North to East. The D3 structures are deformed by a D4 folding phase, characterized by the development of open concentric folds with sub-vertical axial plane. The kinematics indicators of the D1 phase are indicative of an “Alpine” vergence during the early stage of its emplacement. The D2 is indicative of a NE-ward emplacement, probably related to a gravitational tectonic phase. The Alpine structural setting was subsequently reactivated during the Late Oligocene-Early Miocene age, as supported by the occurrence of the D3 phase folding structures affecting the TPB deposits.
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LITHOSTRATIGRAPHY AND Deformation History OF THE LAGO NERO UNIT (CHENAILLET MASSIF, WESTERN ALPS)
Ofioliti, 2004Co-Authors: N. Levi, Michele Marroni, Luca PandolfiAbstract:In the Western Alps, the Schistes Lustres includes ophiolitic units that, even if affected by HP metamorphism, are relatively poorly deformed. Among them, the Lago Nero unit displays a thick and well-developed sedimentary cover, that allows a comparison with the analogue successions of the Northern Apennines. This sedimentary cover includes hemipelagic deposits, represented by Radiolarite Fm., Metalimestone and Replatte Fm., showing a transition to turbiditic (Gondran Flysch) and mass-gravity deposits (Rocher Renard complex). This succession, characterized by a coarsening upward trend, records the approaching of an oceanic floor section to the accretionary wedge. In this picture, the Rocher Renard complex can be regarded as a formation related to a frontal erosion of the accretionary wedge, whereas the Gondran Flysch is interpreted as a turbidite deposits supplied by the continental margin of the Europe plate. The following Deformation History includes four Deformation phases. The first phase D1 Deformations, characterized by HP metamorphism (lawsonite±Na-amphibole±phengite), were achieved during the coherent underplating in the alpine subduction zone. The D2, D3 and D4 phases was developed under retrograde metamorphic conditions, from grren-schist to very-low grade, during the progressive exhumation of the Lago Nero unit. All the collected data suggest that the succession of the Lago Nero unit can be correlated with those of the Internal Liguride units where the same sequence of hemipelagic to turbiditic and mass-gravity deposits has been recognized.
C.-h. Wahlgren - One of the best experts on this subject based on the ideXlab platform.
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Unraveling 1.5 Ga of brittle Deformation History in the Laxemar‐Simpevarp area, southeast Sweden: A contribution to the Swedish site investigation study for the disposal of highly radioactive nuclear waste
Tectonics, 2009Co-Authors: Giulio Viola, G. Venvik Ganerød, C.-h. WahlgrenAbstract:[1] The Swedish Nuclear Fuel and Waste Management Company (SKB) is undertaking site investigation at two locations in Sweden, Forsmark and Laxemar-Simpevarp, with the aim of identifying a suitable area for the construction of a deep repository for the disposal of highly radioactive nuclear waste. Fault slip data from outcrops and oriented drill cores were used to compute paleostress states and to unravel the sites' brittle Deformation History. Results from the Laxemar-Simpevarp area show that its suggested brittle History results from multiple reactivation of fracture and fault sets caused by the many orogenic episodes that affected the region during at least 1.5 Ga of geological evolution in the brittle Deformational regime. Two compressional, approximately NW/NNW-SE/SSE and NNE-SSW oriented shortening events generated sets of conjugate, steep strike-slip fractures. These sets formed during the late stages of the Svecokarelian and possibly also of the Gothian orogeny, soon after the region entered the brittle Deformation domain. The Mesoproterozoic Sveconorwegian orogeny generated fractures and faults that are assigned to a third set of conjugate strike-slip faults, which constrain an approximately E-W σ1. The Caledonian shortening, oriented approximately NW-SE to E-W, reactivated the latter but also formed a new, similarly oriented set of subvertical strike-slip fractures. Permian transtension was oriented NW-SW and caused a prominent set of moderately dipping NW-SE trending normal faults in the Precambrian basement of the study area. Two other approximately NW-SW and NW-SE oriented shortening events are recorded in Ordovician limestones and can be tentatively linked to the far-field effects of the Laramide and Alpine orogenies.
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unraveling 1 5 ga of brittle Deformation History in the laxemar simpevarp area southeast sweden a contribution to the swedish site investigation study for the disposal of highly radioactive nuclear waste
Tectonics, 2009Co-Authors: Giulio Viola, Venvik G Ganerod, C.-h. WahlgrenAbstract:[1] The Swedish Nuclear Fuel and Waste Management Company (SKB) is undertaking site investigation at two locations in Sweden, Forsmark and Laxemar-Simpevarp, with the aim of identifying a suitable area for the construction of a deep repository for the disposal of highly radioactive nuclear waste. Fault slip data from outcrops and oriented drill cores were used to compute paleostress states and to unravel the sites' brittle Deformation History. Results from the Laxemar-Simpevarp area show that its suggested brittle History results from multiple reactivation of fracture and fault sets caused by the many orogenic episodes that affected the region during at least 1.5 Ga of geological evolution in the brittle Deformational regime. Two compressional, approximately NW/NNW-SE/SSE and NNE-SSW oriented shortening events generated sets of conjugate, steep strike-slip fractures. These sets formed during the late stages of the Svecokarelian and possibly also of the Gothian orogeny, soon after the region entered the brittle Deformation domain. The Mesoproterozoic Sveconorwegian orogeny generated fractures and faults that are assigned to a third set of conjugate strike-slip faults, which constrain an approximately E-W σ1. The Caledonian shortening, oriented approximately NW-SE to E-W, reactivated the latter but also formed a new, similarly oriented set of subvertical strike-slip fractures. Permian transtension was oriented NW-SW and caused a prominent set of moderately dipping NW-SE trending normal faults in the Precambrian basement of the study area. Two other approximately NW-SW and NW-SE oriented shortening events are recorded in Ordovician limestones and can be tentatively linked to the far-field effects of the Laramide and Alpine orogenies.