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Judith A. Levy - One of the best experts on this subject based on the ideXlab platform.
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Double jeopardy through social marginalization: HIV risk among Tajik male labor migrants in Moscow.
Drug and alcohol dependence, 2013Co-Authors: Makhbatsho Bakhromov, Judith A. LevyAbstract:This study examines the influence of the double jeopardy of being both a migrant and an injection drug user on the social marginalization of male Tajik labor-migrants working in Moscow and the influence of this dual-marginalization on HIV risk. Three focus group discussions of 8 participants each were conducted in Moscow with a total of 24 Tajik male migrants who regularly inject drugs (IDUs). Results suggest that male Tajik IDUs are at double jeopardy for social marginalization from both Russian society and their own Tajik migrant community. In the absence of adequate knowledge about HIV risk through needle-borne infection, such dual social rejection can help to push Tajik migrant IDUs toward forging close social alliances with their drug-using peers based on a sense of community through sharing drugs and injection equipment. Sexual contact with Russian female sex workers, many of whom use drugs, further contributes to HIV vulnerability and forms a potential bridge for the cross-over of the virus between both populations. With little to no access to formal health services, family and friends living in Moscow can form a sole source of social support at a personal level that can over-ride general community censure but which can lessen or disappear as drug dependency increases. Both drug and health services are sorely needed for this highly vulnerable population. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
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Double jeopardy through social marginalization: HIV risk among Tajik male labor migrants in Moscow.
Drug and Alcohol Dependence, 2013Co-Authors: Makhbatsho Bakhromov, Judith A. LevyAbstract:Abstract Background This study examines the influence of the double jeopardy of being both a migrant and an injection drug user on the social marginalization of male Tajik labor-migrants working in Moscow and the influence of this dual-marginalization on HIV risk. Methods Three focus group discussions of 8 participants each were conducted in Moscow with a total of 24 Tajik male migrants who regularly inject drugs (IDUs). Results Results suggest that male Tajik IDUs are at double jeopardy for social marginalization from both Russian society and their own Tajik migrant community. In the absence of adequate knowledge about HIV risk through needle-borne infection, such dual social rejection can help to push Tajik migrant IDUs toward forging close social alliances with their drug-using peers based on a sense of community through sharing drugs and injection equipment. Sexual contact with Russian female sex workers, many of whom use drugs, further contributes to HIV vulnerability and forms a potential bridge for the cross-over of the virus between both populations. With little to no access to formal health services, family and friends living in Moscow can form a sole source of social support at a personal level that can over-ride general community censure but which can lessen or disappear as drug dependency increases. Conclusion Both drug and health services are sorely needed for this highly vulnerable population.
Bernd Schurr - One of the best experts on this subject based on the ideXlab platform.
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Tajik basin and southwestern tian shan northwestern india asia collision zone 2 timing of basin inversion tian shan mountain building and relation to pamir plateau advance and deep india asia indentation
Tectonics, 2020Co-Authors: Sanaa Abdulhameed, Lothar Ratschbacher, Raymond Jonckheere, łukasz Gągala, Eva Enkelmann, Alexandra Kasner, Myriam Kars, Adam Szulc, Sofiakaterina Kufner, Bernd SchurrAbstract:The Tajik basin and southwestern Tian Shan constitute the northwestern tip of the India-Asia collision zone. Basin inversion formed the thinskinned Tajik fold-thrust belt, outlined by westward convex fold trains, underlain by a decollement in Jurassic evaporites. The belt's leading edge-the Uzbek Gissar-and its transpressional northern lateral margin-the Tajik Gissar-constitute the thickskinned foreland buttresses. Apatite fission-track data indicate~40-to 15-Ma reheating by sediment burial in the Tian Shan. In the Gissar and the Tajik fold-thrust belt, apatite fission-track and (U,Th)/He ages date the major phase of shortening/erosion between~12 and 1 Ma, with exhumation to 2-to 3-km crustal depths within a few Myr after onset of shortening. Shortening spread immediately across the fold-thrust belt, typical for belts floored by a detachment in ductile rocks, and into the foreland buttresses. Reactivation concentrated in the internal (eastern) fold-thrust belt with the thickest evaporates. The youngest ages (~6.6-1.6 Ma) occur along the Vakhsh thrust, the active erosional front of the fold-thrust belt in the northeastern Tajik basin, where it narrows between the converging Tian Shan and Pamir. Our study links major events in the Pamir hinterland with the Tajik basin and Tian Shan foreland. In the late Eocene-early Miocene, the advancing Pamir-plateau crust loaded the foreland, inducing subsidence, reheating, and early shortening. Basin inversion and major shortening/transpression in the foreland buttresses from~12 Ma onward were synchronous with the subcrustal indentation of Indian lithosphere into the Tajik-Tarim basin lithosphere and the onset of its rollback beneath the Pamir.
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Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 1. Structure, Kinematics, and Salt Tectonics in the Tajik Fold-and-Thrust Belt of the Western Foreland of the Pamir
Tectonics, 2020Co-Authors: Łukasz Gągała, Lothar Ratschbacher, Jean-claude Ringenbach, Sofia-katarina Kufner, Bernd Schurr, Ralf Dedow, Sanaa Abdulhameed, Edouard Le Garzic, Mustafo Gadoev, Ilhomjon OimahmadovAbstract:Surface, seismic, and borehole data characterize the Neogene-Recent Tajik fold-and-thrust belt of the Tajik basin. The basin experienced little sub-detachment basement deformation, acting as a rigid foreland plate during the Pamir orogeny. The Tajik fold-and-thrust belt contains variable thinskinned structural styles, changing along and across strike as a function of the thickness and facies of Upper Jurassic evaporites, which constitute the basal detachment, and the influence of the surrounding thickskinned belts. The southern Tajik fold-and-thrust belt shows regularly spaced, salt-cored, thrusted detachment anticlines that transition northward into imbricated thrust sheets grouped in oppositely verging stacks facing each other across a common footwall syncline. The width of the fold-and-thrust belt decreases northeastward accommodated by the Ilyak fault, a lateral ramp developed over a seismically active dextral basement fault. The southeastern Tajik fold-and-thrust belt contains massive subaerial salt sheets, formed by squeezing of preexisting salt diapirs. The salt-tectonic domain originates from a local depocenter within the Late Jurassic Amu Darya-Tajik evaporitic basin. Serial cross sections, integrating the structural geometries, yielded minimum thinskinned shortening oriented at~90°to the India-Asia convergence direction, increasing from~93 km in the south to~148 km in the center, and dropping tõ 22 km in the northeast; total shortening-including the foreland buttress-is ≥170 km. Most of the shortening in the central-southern Tajik fold-and-thrust belt occurred by hinterland-vergent, high-displacement back thrusts. The Pamir played a dominant role in the transfer of shortening to the sedimentary infill of the Tajik basin with the Tian Shan acting as a semi-passive buttress.
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Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 2. Timing of Basin Inversion, Tian Shan Mountain Building, and Relation to Pamir-Plateau Advance and Deep India-Asia Indentation
Tectonics, 2020Co-Authors: Sanaa Abdulhameed, Łukasz Gągała, Lothar Ratschbacher, Raymond Jonckheere, Eva Enkelmann, Myriam Kars, Adam Szulc, Sofiakaterina Kufner, Alexandra Käßner, Bernd SchurrAbstract:The Tajik basin and southwestern Tian Shan constitute the northwestern tip of the India-Asia collision zone. Basin inversion formed the thinskinned Tajik fold-thrust belt, outlined by westward convex fold trains, underlain by a décollement in Jurassic evaporites. The belt's leading edge-the Uzbek Gissar-and its transpressional northern lateral margin-the Tajik Gissar-constitute the thickskinned foreland buttresses. Apatite fission-track data indicate~40-to 15-Ma reheating by sediment burial in the Tian Shan. In the Gissar and the Tajik fold-thrust belt, apatite fission-track and (U,Th)/He ages date the major phase of shortening/erosion between~12 and 1 Ma, with exhumation to 2-to 3-km crustal depths within a few Myr after onset of shortening. Shortening spread immediately across the fold-thrust belt, typical for belts floored by a detachment in ductile rocks, and into the foreland buttresses. Reactivation concentrated in the internal (eastern) fold-thrust belt with the thickest evaporates. The youngest ages (~6.6-1.6 Ma) occur along the Vakhsh thrust, the active erosional front of the fold-thrust belt in the northeastern Tajik basin, where it narrows between the converging Tian Shan and Pamir. Our study links major events in the Pamir hinterland with the Tajik basin and Tian Shan foreland. In the late Eocene-early Miocene, the advancing Pamir-plateau crust loaded the foreland, inducing subsidence, reheating, and early shortening. Basin inversion and major shortening/transpression in the foreland buttresses from~12 Ma onward were synchronous with the subcrustal indentation of Indian lithosphere into the Tajik-Tarim basin lithosphere and the onset of its rollback beneath the Pamir.
Ilhomjon Oimahmadov - One of the best experts on this subject based on the ideXlab platform.
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Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 1. Structure, Kinematics, and Salt Tectonics in the Tajik Fold-and-Thrust Belt of the Western Foreland of the Pamir
Tectonics, 2020Co-Authors: Łukasz Gągała, Lothar Ratschbacher, Jean-claude Ringenbach, Sofia-katarina Kufner, Bernd Schurr, Ralf Dedow, Sanaa Abdulhameed, Edouard Le Garzic, Mustafo Gadoev, Ilhomjon OimahmadovAbstract:Surface, seismic, and borehole data characterize the Neogene-Recent Tajik fold-and-thrust belt of the Tajik basin. The basin experienced little sub-detachment basement deformation, acting as a rigid foreland plate during the Pamir orogeny. The Tajik fold-and-thrust belt contains variable thinskinned structural styles, changing along and across strike as a function of the thickness and facies of Upper Jurassic evaporites, which constitute the basal detachment, and the influence of the surrounding thickskinned belts. The southern Tajik fold-and-thrust belt shows regularly spaced, salt-cored, thrusted detachment anticlines that transition northward into imbricated thrust sheets grouped in oppositely verging stacks facing each other across a common footwall syncline. The width of the fold-and-thrust belt decreases northeastward accommodated by the Ilyak fault, a lateral ramp developed over a seismically active dextral basement fault. The southeastern Tajik fold-and-thrust belt contains massive subaerial salt sheets, formed by squeezing of preexisting salt diapirs. The salt-tectonic domain originates from a local depocenter within the Late Jurassic Amu Darya-Tajik evaporitic basin. Serial cross sections, integrating the structural geometries, yielded minimum thinskinned shortening oriented at~90°to the India-Asia convergence direction, increasing from~93 km in the south to~148 km in the center, and dropping tõ 22 km in the northeast; total shortening-including the foreland buttress-is ≥170 km. Most of the shortening in the central-southern Tajik fold-and-thrust belt occurred by hinterland-vergent, high-displacement back thrusts. The Pamir played a dominant role in the transfer of shortening to the sedimentary infill of the Tajik basin with the Tian Shan acting as a semi-passive buttress.
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timing of seawater retreat from proto paratethys sedimentary provenance and tectonic rotations in the late eocene early oligocene in the Tajik basin central asia
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Zhiliang Zhang, Mustafo Gadoev, Brian F Windley, Shengchen Tian, Sherzod Abdulov, Ilhomjon OimahmadovAbstract:Abstract The Tajik Basin is now located to the west of the Pamirs, but it formerly connected with the Tarim Basin, occupied by a large epicontinental sea (proto-Paratethys Sea) once extended from Europe to Central Asia. However, the northward indentation and collision of the Pamirs into the Tian Shan separated the Tajik and Tarim Basins, creating manifold implications and consequences. Consequently, timing of the final seawater retreat from the Tajik Basin is important for understanding the evolution of the proto-Paratethys Sea, the effect of the northward indentation of the Pamirs on the sea regression, and the influence of seawater retreat on the Cenozoic aridification in the Tajik Basin. Here we present a multidisciplinary study of Upper Paleogene strata from the central Tajik Basin. Our results demonstrate that the final seawater retreat from the center of the Tajik Basin occurred at 38.6 Ma, which is earlier than a previous age of 37.4 Ma from the northeastern Tajik Basin. Such a late Eocene sea retreat was quasi-simultaneous with that in the Tarim Basin. This final marine regression was mainly a consequence of the northward indentation and growth of the Pamirs, which was an intracontinental response to the India-Asia collision. Our new detrital zircon ages indicate that the provenance of Upper Eocene-lower Oligocene strata was from the Pamirs rather than Tian Shan, implying that the reactivation of the Tian Shan was later than the early Oligocene. Our paleomagnetic data indicate a 30° counterclockwise rotation of the central Tajik Basin that is much bigger than the previous estimate of 17°, and we propose that such a counterclockwise rotation mostly occurred after the late Miocene. Finally, different from the previous reported aridfication at 39 Ma or 37 Ma, our evidence demonstrates that drought intensified since the start of the Oligocene at 34 Ma, being related to reduced water vapor transport to Central Asia, caused by global cooling-induced sea-level drop, the retreating Paratethys Sea, and weakened sea surface evaporation.
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Late Miocene accelerated exhumation in the central Tajik Basin and implications for northward indention and lateral growth of the Pamir
Tectonophysics, 2020Co-Authors: Jimin Sun, Mustafo Gadoev, Zhiliang Zhang, Shengchen Tian, Sherzod Abdulov, Yingying Jia, Ilhomjon OimahmadovAbstract:Abstract The Tajik Basin, located at the west of the Pamir, is characterized by a series of thin-skinned folds and thrusts within its interior. Constraining the onset of deformation of these structures is important both for illustrating basin inversion process and for understanding growth history of the adjacent Pamir. To date, the timing of thrusting and folding within the Tajik Basin has not been well studied. In this study, we determined the timing of fault motion of the Aruntau thrust in the central Tajik Basin by using apatite (U Th)/He thermochronometry. Apatite (U Th)/He age data of sandstone samples collected from the hanging wall of the Aruntau thrust fault, combined with thermal history simulation, constrains the onset of rapid cooling of rock samples at ca. 10–6 Ma. Given the compressional tectonic regime, we propose that the observed rapid cooling was caused by thrust-induced exhumation, and thus, the cooling age of ~10–6 Ma approximately represents the timing of thrusting initiation. Integrated with previous studies, we found that the late Miocene tectonic deformation was not only circumscribed within the Tajik Basin, but also occurred in the areas north and east of the Pamir and within the Pamir. We suggest that the synchronously widespread tectonic deformation in the Pamir-Tian Shan convergence zone reflects the enhanced northward indentation and lateral growth of the Pamir since the late Miocene.
Lothar Ratschbacher - One of the best experts on this subject based on the ideXlab platform.
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Tajik basin and southwestern tian shan northwestern india asia collision zone 2 timing of basin inversion tian shan mountain building and relation to pamir plateau advance and deep india asia indentation
Tectonics, 2020Co-Authors: Sanaa Abdulhameed, Lothar Ratschbacher, Raymond Jonckheere, łukasz Gągala, Eva Enkelmann, Alexandra Kasner, Myriam Kars, Adam Szulc, Sofiakaterina Kufner, Bernd SchurrAbstract:The Tajik basin and southwestern Tian Shan constitute the northwestern tip of the India-Asia collision zone. Basin inversion formed the thinskinned Tajik fold-thrust belt, outlined by westward convex fold trains, underlain by a decollement in Jurassic evaporites. The belt's leading edge-the Uzbek Gissar-and its transpressional northern lateral margin-the Tajik Gissar-constitute the thickskinned foreland buttresses. Apatite fission-track data indicate~40-to 15-Ma reheating by sediment burial in the Tian Shan. In the Gissar and the Tajik fold-thrust belt, apatite fission-track and (U,Th)/He ages date the major phase of shortening/erosion between~12 and 1 Ma, with exhumation to 2-to 3-km crustal depths within a few Myr after onset of shortening. Shortening spread immediately across the fold-thrust belt, typical for belts floored by a detachment in ductile rocks, and into the foreland buttresses. Reactivation concentrated in the internal (eastern) fold-thrust belt with the thickest evaporates. The youngest ages (~6.6-1.6 Ma) occur along the Vakhsh thrust, the active erosional front of the fold-thrust belt in the northeastern Tajik basin, where it narrows between the converging Tian Shan and Pamir. Our study links major events in the Pamir hinterland with the Tajik basin and Tian Shan foreland. In the late Eocene-early Miocene, the advancing Pamir-plateau crust loaded the foreland, inducing subsidence, reheating, and early shortening. Basin inversion and major shortening/transpression in the foreland buttresses from~12 Ma onward were synchronous with the subcrustal indentation of Indian lithosphere into the Tajik-Tarim basin lithosphere and the onset of its rollback beneath the Pamir.
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Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 1. Structure, Kinematics, and Salt Tectonics in the Tajik Fold-and-Thrust Belt of the Western Foreland of the Pamir
Tectonics, 2020Co-Authors: Łukasz Gągała, Lothar Ratschbacher, Jean-claude Ringenbach, Sofia-katarina Kufner, Bernd Schurr, Ralf Dedow, Sanaa Abdulhameed, Edouard Le Garzic, Mustafo Gadoev, Ilhomjon OimahmadovAbstract:Surface, seismic, and borehole data characterize the Neogene-Recent Tajik fold-and-thrust belt of the Tajik basin. The basin experienced little sub-detachment basement deformation, acting as a rigid foreland plate during the Pamir orogeny. The Tajik fold-and-thrust belt contains variable thinskinned structural styles, changing along and across strike as a function of the thickness and facies of Upper Jurassic evaporites, which constitute the basal detachment, and the influence of the surrounding thickskinned belts. The southern Tajik fold-and-thrust belt shows regularly spaced, salt-cored, thrusted detachment anticlines that transition northward into imbricated thrust sheets grouped in oppositely verging stacks facing each other across a common footwall syncline. The width of the fold-and-thrust belt decreases northeastward accommodated by the Ilyak fault, a lateral ramp developed over a seismically active dextral basement fault. The southeastern Tajik fold-and-thrust belt contains massive subaerial salt sheets, formed by squeezing of preexisting salt diapirs. The salt-tectonic domain originates from a local depocenter within the Late Jurassic Amu Darya-Tajik evaporitic basin. Serial cross sections, integrating the structural geometries, yielded minimum thinskinned shortening oriented at~90°to the India-Asia convergence direction, increasing from~93 km in the south to~148 km in the center, and dropping tõ 22 km in the northeast; total shortening-including the foreland buttress-is ≥170 km. Most of the shortening in the central-southern Tajik fold-and-thrust belt occurred by hinterland-vergent, high-displacement back thrusts. The Pamir played a dominant role in the transfer of shortening to the sedimentary infill of the Tajik basin with the Tian Shan acting as a semi-passive buttress.
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Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 2. Timing of Basin Inversion, Tian Shan Mountain Building, and Relation to Pamir-Plateau Advance and Deep India-Asia Indentation
Tectonics, 2020Co-Authors: Sanaa Abdulhameed, Łukasz Gągała, Lothar Ratschbacher, Raymond Jonckheere, Eva Enkelmann, Myriam Kars, Adam Szulc, Sofiakaterina Kufner, Alexandra Käßner, Bernd SchurrAbstract:The Tajik basin and southwestern Tian Shan constitute the northwestern tip of the India-Asia collision zone. Basin inversion formed the thinskinned Tajik fold-thrust belt, outlined by westward convex fold trains, underlain by a décollement in Jurassic evaporites. The belt's leading edge-the Uzbek Gissar-and its transpressional northern lateral margin-the Tajik Gissar-constitute the thickskinned foreland buttresses. Apatite fission-track data indicate~40-to 15-Ma reheating by sediment burial in the Tian Shan. In the Gissar and the Tajik fold-thrust belt, apatite fission-track and (U,Th)/He ages date the major phase of shortening/erosion between~12 and 1 Ma, with exhumation to 2-to 3-km crustal depths within a few Myr after onset of shortening. Shortening spread immediately across the fold-thrust belt, typical for belts floored by a detachment in ductile rocks, and into the foreland buttresses. Reactivation concentrated in the internal (eastern) fold-thrust belt with the thickest evaporates. The youngest ages (~6.6-1.6 Ma) occur along the Vakhsh thrust, the active erosional front of the fold-thrust belt in the northeastern Tajik basin, where it narrows between the converging Tian Shan and Pamir. Our study links major events in the Pamir hinterland with the Tajik basin and Tian Shan foreland. In the late Eocene-early Miocene, the advancing Pamir-plateau crust loaded the foreland, inducing subsidence, reheating, and early shortening. Basin inversion and major shortening/transpression in the foreland buttresses from~12 Ma onward were synchronous with the subcrustal indentation of Indian lithosphere into the Tajik-Tarim basin lithosphere and the onset of its rollback beneath the Pamir.
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Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 3. Preorogenic to Synorogenic Retro-foreland Basin Evolution in the Eastern Tajik Depression and Linkage to the Pamir Hinterland
Tectonics, 2020Co-Authors: Ralf Dedow, Łukasz Gągała, Lothar Ratschbacher, Jean-claude Ringenbach, Adam Szulc, Matthias Franz, Jörg Schneider, Jan Brückner, Negmat Rajabov, Mustafo GadoevAbstract:The Tajik basin archives the orogenic evolution of the Pamir hinterland. Stratigraphic‐sedimentologic observations from Cretaceous‐Pliocene strata along its eastern margin describe the depositional environment and basin‐formation stages in reaction to hinterland exhumation and basin inversion. During the Late Cretaceous‐Eocene (preorogenic stage: ~100–34 Ma), a shallow‐marine to terrestrial basin extended throughout Central Asia. An alluvial plain with influx of conglomerate bodies (Baljuvon Formation) indicates a first pulse of hinterland erosion and foreland‐basin formation in the late Oligocene‐early Miocene (synorogenic stage Ia: ~34–23 Ma). Further hinterland exhumation deposited massive alluvial conglomerates (Khingou Formation) in the early‐middle Miocene (synorogenic stage Ib: ~23–15 Ma). Westward thickening growth strata suggest transformation of the Tajik basin into the Tajik fold‐thrust belt in the middle‐late Miocene (synorogenic stage IIa: ~15–5 Ma). Increased water supply led to the formation of fluvial mega‐fans (Tavildara Formation). Latest Miocene‐Pliocene shortening constructed basin morphology that blocked sediment bypass into the central basin from the east (Karanak Formation), triggering drainage‐system reorganization from transverse to longitudinal sediment transport (synorogenic stage IIb: < ~5 Ma). Accelerated shortening (~27–20 Ma) and foreland‐directed collapse (~23–12 Ma) of Pamir‐plateau crust loaded the foreland and induced synorogenic stages Ia and Ib. Coupling of Indian and Asian cratonic lithospheres and onset of northward and westward delamination/rollback of Asian lithosphere (i.e., lithosphere of the Tajik basin) beneath the Pamir at ~12–11 Ma transformed the Tajik basin into the Tajik fold‐thrust belt (synorogenic stage IIa). The timing of the sedimentologically derived basin reconfiguration matches the thermochronologically derived onset of Tajik‐basin inversion at ~12 Ma.
Sanaa Abdulhameed - One of the best experts on this subject based on the ideXlab platform.
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Tajik basin and southwestern tian shan northwestern india asia collision zone 2 timing of basin inversion tian shan mountain building and relation to pamir plateau advance and deep india asia indentation
Tectonics, 2020Co-Authors: Sanaa Abdulhameed, Lothar Ratschbacher, Raymond Jonckheere, łukasz Gągala, Eva Enkelmann, Alexandra Kasner, Myriam Kars, Adam Szulc, Sofiakaterina Kufner, Bernd SchurrAbstract:The Tajik basin and southwestern Tian Shan constitute the northwestern tip of the India-Asia collision zone. Basin inversion formed the thinskinned Tajik fold-thrust belt, outlined by westward convex fold trains, underlain by a decollement in Jurassic evaporites. The belt's leading edge-the Uzbek Gissar-and its transpressional northern lateral margin-the Tajik Gissar-constitute the thickskinned foreland buttresses. Apatite fission-track data indicate~40-to 15-Ma reheating by sediment burial in the Tian Shan. In the Gissar and the Tajik fold-thrust belt, apatite fission-track and (U,Th)/He ages date the major phase of shortening/erosion between~12 and 1 Ma, with exhumation to 2-to 3-km crustal depths within a few Myr after onset of shortening. Shortening spread immediately across the fold-thrust belt, typical for belts floored by a detachment in ductile rocks, and into the foreland buttresses. Reactivation concentrated in the internal (eastern) fold-thrust belt with the thickest evaporates. The youngest ages (~6.6-1.6 Ma) occur along the Vakhsh thrust, the active erosional front of the fold-thrust belt in the northeastern Tajik basin, where it narrows between the converging Tian Shan and Pamir. Our study links major events in the Pamir hinterland with the Tajik basin and Tian Shan foreland. In the late Eocene-early Miocene, the advancing Pamir-plateau crust loaded the foreland, inducing subsidence, reheating, and early shortening. Basin inversion and major shortening/transpression in the foreland buttresses from~12 Ma onward were synchronous with the subcrustal indentation of Indian lithosphere into the Tajik-Tarim basin lithosphere and the onset of its rollback beneath the Pamir.
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Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 1. Structure, Kinematics, and Salt Tectonics in the Tajik Fold-and-Thrust Belt of the Western Foreland of the Pamir
Tectonics, 2020Co-Authors: Łukasz Gągała, Lothar Ratschbacher, Jean-claude Ringenbach, Sofia-katarina Kufner, Bernd Schurr, Ralf Dedow, Sanaa Abdulhameed, Edouard Le Garzic, Mustafo Gadoev, Ilhomjon OimahmadovAbstract:Surface, seismic, and borehole data characterize the Neogene-Recent Tajik fold-and-thrust belt of the Tajik basin. The basin experienced little sub-detachment basement deformation, acting as a rigid foreland plate during the Pamir orogeny. The Tajik fold-and-thrust belt contains variable thinskinned structural styles, changing along and across strike as a function of the thickness and facies of Upper Jurassic evaporites, which constitute the basal detachment, and the influence of the surrounding thickskinned belts. The southern Tajik fold-and-thrust belt shows regularly spaced, salt-cored, thrusted detachment anticlines that transition northward into imbricated thrust sheets grouped in oppositely verging stacks facing each other across a common footwall syncline. The width of the fold-and-thrust belt decreases northeastward accommodated by the Ilyak fault, a lateral ramp developed over a seismically active dextral basement fault. The southeastern Tajik fold-and-thrust belt contains massive subaerial salt sheets, formed by squeezing of preexisting salt diapirs. The salt-tectonic domain originates from a local depocenter within the Late Jurassic Amu Darya-Tajik evaporitic basin. Serial cross sections, integrating the structural geometries, yielded minimum thinskinned shortening oriented at~90°to the India-Asia convergence direction, increasing from~93 km in the south to~148 km in the center, and dropping tõ 22 km in the northeast; total shortening-including the foreland buttress-is ≥170 km. Most of the shortening in the central-southern Tajik fold-and-thrust belt occurred by hinterland-vergent, high-displacement back thrusts. The Pamir played a dominant role in the transfer of shortening to the sedimentary infill of the Tajik basin with the Tian Shan acting as a semi-passive buttress.
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Tajik Basin and Southwestern Tian Shan, Northwestern India-Asia Collision Zone: 2. Timing of Basin Inversion, Tian Shan Mountain Building, and Relation to Pamir-Plateau Advance and Deep India-Asia Indentation
Tectonics, 2020Co-Authors: Sanaa Abdulhameed, Łukasz Gągała, Lothar Ratschbacher, Raymond Jonckheere, Eva Enkelmann, Myriam Kars, Adam Szulc, Sofiakaterina Kufner, Alexandra Käßner, Bernd SchurrAbstract:The Tajik basin and southwestern Tian Shan constitute the northwestern tip of the India-Asia collision zone. Basin inversion formed the thinskinned Tajik fold-thrust belt, outlined by westward convex fold trains, underlain by a décollement in Jurassic evaporites. The belt's leading edge-the Uzbek Gissar-and its transpressional northern lateral margin-the Tajik Gissar-constitute the thickskinned foreland buttresses. Apatite fission-track data indicate~40-to 15-Ma reheating by sediment burial in the Tian Shan. In the Gissar and the Tajik fold-thrust belt, apatite fission-track and (U,Th)/He ages date the major phase of shortening/erosion between~12 and 1 Ma, with exhumation to 2-to 3-km crustal depths within a few Myr after onset of shortening. Shortening spread immediately across the fold-thrust belt, typical for belts floored by a detachment in ductile rocks, and into the foreland buttresses. Reactivation concentrated in the internal (eastern) fold-thrust belt with the thickest evaporates. The youngest ages (~6.6-1.6 Ma) occur along the Vakhsh thrust, the active erosional front of the fold-thrust belt in the northeastern Tajik basin, where it narrows between the converging Tian Shan and Pamir. Our study links major events in the Pamir hinterland with the Tajik basin and Tian Shan foreland. In the late Eocene-early Miocene, the advancing Pamir-plateau crust loaded the foreland, inducing subsidence, reheating, and early shortening. Basin inversion and major shortening/transpression in the foreland buttresses from~12 Ma onward were synchronous with the subcrustal indentation of Indian lithosphere into the Tajik-Tarim basin lithosphere and the onset of its rollback beneath the Pamir.