Structural And Nd Isotopic Evidence For The Tectonic Evolution Of The Himalayan Fold Thrust Belt Western Nepal And The Northern Tibetan Plateau Phd
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Structural And Nd Isotopic Evidence For The Tectonic Evolution Of The Himalayan Fold Thrust Belt Western Nepal And The Northern Tibetan Plateau Phd
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Author : Delores Marie Robinson
language : en
Publisher:
Release Date : 2001
Structural And Nd Isotopic Evidence For The Tectonic Evolution Of The Himalayan Fold Thrust Belt Western Nepal And The Northern Tibetan Plateau Phd written by Delores Marie Robinson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Channel Flow Ductile Extrusion And Exhumation In Continental Collision Zones
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Author : Richard D. Law
language : en
Publisher: Geological Society of London
Release Date : 2006
Channel Flow Ductile Extrusion And Exhumation In Continental Collision Zones written by Richard D. Law and has been published by Geological Society of London this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Science categories.
This volume includes sections on: Evolution of ideas on channel flow and ductile extrusion in the Himalaya-Tibetan Plateau system; Modeling channel flow and ductile extrusion processes; Geological constraints on channel flow and ductile extrusion as an important orogenic process in the Himalaya-Tibetan Plateau, the Hellenides and Appalachians, and the Canadian Cordillera.
Structural And Thermal Evolution Of The Himalayan Thrust Belt In Midwestern Nepal
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Author : P.G. DeCelles
language : en
Publisher: Geological Society of America
Release Date : 2020-06-16
Structural And Thermal Evolution Of The Himalayan Thrust Belt In Midwestern Nepal written by P.G. DeCelles and has been published by Geological Society of America this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-06-16 with Science categories.
"Spanning eight kilometers of topographic relief, the Himalayan fold-thrust belt in Nepal has accommodated more than 700 km of Cenozoic convergence between the Indian subcontinent and Asia. Rapid tectonic shortening and erosion in a monsoonal climate have exhumed greenschist to upper amphibolite facies rocks along with unmetamorphosed rocks, including a 5-6-km-thick Cenozoic foreland basin sequence. This Special Paper presents new geochronology, multisystem thermochronology, structural geology, and geological mapping of an approximately 37,000 km2 region in midwestern and western Nepal. This work informs enduring Himalayan debates, including how and where to map the Main Central thrust, the geometry of the seismically active basal Himalayan detachment, processes of tectonic shortening in the context of postcollisional India-Asia convergence, and long-term geodynamics of the orogenic wedge"--Publisher's website
Dissertation Abstracts International
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Author :
language : en
Publisher:
Release Date : 2002
Dissertation Abstracts International written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Dissertations, Academic categories.
Uplift Mechanisms And The History Of The Tibetan Plateau
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Author : Junsheng Nie
language : en
Publisher: Geological Society of America
Release Date : 2014
Uplift Mechanisms And The History Of The Tibetan Plateau written by Junsheng Nie and has been published by Geological Society of America this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Science categories.
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Tectonic Evolution Of The Easternmost Himalayan Collisional System
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Author : Peter Jasura Haproff
language : en
Publisher:
Release Date : 2018
Tectonic Evolution Of The Easternmost Himalayan Collisional System written by Peter Jasura Haproff and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
The Cenozoic India-Asia collision generated the Tibetan Plateau and the Himalayan collisional system, the latter consisting of the convergence-perpendicular Himalayan orogen and the convergence-parallel Eastern and Western Flanking Belts located along the margins of India. Studying the evolution of each of these tectonic domains is critical to understanding the collision process and differentiating the end-member models of indenter-induced continental deformation. Despite this importance, there is a notable lack of geologic investigations on the development of the flanking belts in comparison to the extensive research of the Tibetan Plateau and east-trending Himalayan orogen. To address this problem, the research of this dissertation is focused on the Mesozoic-Cenozoic tectonic evolution of the northernmost segment of the Eastern Flanking Belt, the northern Indo-Burma Ranges, which are located directly east to southeast of the eastern Himalayan syntaxis. In the following chapters, I integrate the results of geologic field mapping, balanced cross section construction and restoration, U-Pb zircon geochronology, whole-rock geochemistry, thermobarometry, and (U-Th)/He zircon thermochronology to examine the litho-structural framework of the northern Indo-Burma Ranges and tectonic relationships in time and space with the adjacent eastern Himalayan orogen, the southern Tibetan Plateau, and the Eastern Flanking Belt. The research of this dissertation shows that the study area exposes a southwest- to west-directed Cenozoic thrust belt cored by a hinterland-dipping duplex system. Thrust faults sole into a northeast- to east-dipping di collement, which extends to >30 km depth. Southwestward forward propagation of the thrust belt in the foreland was coeval with out-of-sequence thrusting in the hinterland. This structural framework combined with the observed southward deflection in the trends of ductile stretching lineations within shear zones (northeast-trending in the north and east-trending in the south) suggest deformation around the eastern Himalayan syntaxis is best approximated by models of clockwise lithospheric flow accommodated by distributed thrusting. Major lithologic units involved in the northern Indo-Burma thrust belt from south to north include the easternmost continuations of the Tertiary Sub-Himalayan Sequence, Proterozoic-Cambrian Lesser Himalayan Sequence, and Indus-Yarlung suture zone of the Himalayan orogen and the Mesozoic northern Gangdese batholith belt and Mesoproterozoic basement of the Lhasa terrane. However, several Himalayan-Tibetan lithologic units are missing, including the Paleoproterozoic-Ordovician Greater Himalayan Crystalline Complex, Proterozoic-Eocene Tethyan Himalayan Sequence, Mesozoic-Cenozoic Xigaze forearc basin, and Cenozoic igneous rocks of the southern Gangdese batholith. Research suggests that these units were present in the study area at the onset of the Cenozoic India-Asia collision and their present-day absence is related to an eastward increase in post-collisional crustal shortening and continental underthrusting along the Himalayan collisional system. This interpretation is supported by a Cenozoic shortening strain estimate of ~81% (>156 km) across the northern Indo-Burma Ranges and a dramatic southward decrease in the width of the collisional system from ~200 km across the Himalayan orogen to ~5 km across the study area. Active deformation across the northern Indo-Burma Ranges and adjacent southeastern Tibetan Plateau is characterized by right-slip transpression partitioned between the range-bounding, oblique-slip Mishmi thrust in the southwest and right-slip Puqu and Parlung faults of Jiali fault zone in the northeast. The leading Mishmi thrust is kinematically-linked with the ~1000-km-long, right-slip Sagaing fault to the south via a previously-unmapped, southwest-trending restraining bend. This structural relationship of the Eastern Flanking Belt provides a key example of the spatial transition from transpressional deformation near the corner of an indenter to discrete right-slip motion along the side of an indenter during continental collision.
Structural And Kinematic Evolution Of The Himalayan Thrust Belt Central Nepal
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Author : Subodha Khanal
language : en
Publisher:
Release Date : 2014
Structural And Kinematic Evolution Of The Himalayan Thrust Belt Central Nepal written by Subodha Khanal and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Electronic dissertations categories.
Over the last two decades, several competing dynamic models have been proposed to explain the kinematics of the Himalayan thrust belt. The accuracy of dynamic and kinematic models is limited by poorly documented geologic structures. With increased accessibility of the thrust belt and advances in analytical techniques, several new data sets greatly improve our understanding and provide a background to reevaluate the kinematics of the Himalayan thrust belt. In this dissertation, I integrate structural mapping, microstructural analysis, detrital and igneous zircon geochronology, low-temperature thermochronology, Nd isotopic analysis, and structural reconstructions in central Nepal to determine the evolution of the Himalayan thrust belt. Because the role and evolution of the Main Central thrust, the Ramgarh-Munsiari thrust, and the Lesser Himalayan duplex are highly debated, I emphasize these systems to provide a comprehensive structural evolution of the Himalayan thrust belt. U-Pb dating of metamorphic rims of igneous zircons and crystallization ages of cross-cutting pegmatite veins suggest that deformation on the Himalayan thrust belt started with slip on an intra-Greater Himalayan thrust active at ~20-29 Ma that emplaced the now erosionally isolated Kathmandu klippe. These ages predate the slip on the Main Central thrust. Absence of a fault contact between the Greater Himalaya and Tethyan Himalaya in the klippe suggests the South Tibetan Detachment system may have activated after the slip started on the intra-Greater Himalayan thrust. Ductile motion on the South Tibetan Detachment system may have ended prior to the activation of the Main Central thrust. This result and observations contradict the extrusion model that advocates contemporaneous activity with thrust sense shear on the Main Central thrust and normal sense shear on the South Tibetan Detachment system. In addition, there is another orogenic scale thrust, subparallel to the Main Central thrust, the Ramgarh-Munsiari thrust, that only carries lower Lesser Himalayan Paleoproterozoic rock over other Lesser Himalayan rock and accommodates a magnitude of shortening similar to the 100's km of slip on the Main Central thrust. I construct an orogenic scale balanced cross-section along the Marsyangdi River where the entire Lesser Himalayan duplex is exposed, particularly focusing on the architecture of the duplex to determine whether the duplex is forward dipping or hinterland dipping and the presence/absence of an orogenic scale, out-of-sequence thrust. I integrate quartz-feldspar deformation temperatures and zircon (U-Th)/He thermochronology and present a kinematic model that provides the structural context for geophysical, petrological, and geochronological studies in central Nepal. Collectively, this study helps to determine partitioning of strain among the various thrust sheets that account for over 2000 km of shortening in a compressional continental tectonic setting. The results suggest that deformation in the Himalaya began with the activation of an intra-Greater Himalayan thrust and successively moved south with the activation of Main Central thrust, Ramgarh-Munsairi thrust, Lesser Himalayan duplex, and finally the Subhimalayan thrust system. Although there was minor out-of-sequence thrusting in the hinterland, the bulk of the Himalaya evolved in-sequence thrusting from north to south.
Tectonic Evolution Of The Northeastern Tibetan Plateau
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Author : Andrew Vincent Zuza
language : en
Publisher:
Release Date : 2016
Tectonic Evolution Of The Northeastern Tibetan Plateau written by Andrew Vincent Zuza and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
How the Tibetan Plateau was constructed and evolved in response to ongoing India-Asia convergence since 65-55 Ma is fundamental in understanding processes of continental tectonics. Furthermore, the kinematics and mechanisms of plateau formation and continental deformation have implications for the complex interactions between tectonics, erosion, and climate change in Earth's most recent history. To provide insights into these processes, my research is focused on the development of the northern margin of the Tibetan Plateau, which is defined by the 350-km-wide and 1300-km-long Cenozoic Qilian Shan-Nan Shan thrust belt. This active fold and thrust system overprinted a region that has a complex pre-Cenozoic tectonic history involving multiple phases of Proterozoic basement deformation and early Paleozoic orogeny. In this work, I integrate geologic mapping, balanced cross section construction and restoration, seismic reflection interpretation, geochronology, thermobarometry, geodetic data analysis, and analogue modeling to investigate the tectonic development of northern Tibet over a range of timescales, from the Proterozoic evolution of central Asian cratons to the active deformation that is shaping the northern margin of the Tibetan Plateau. The magnitude, style, and distribution of Cenozoic shortening strain across northern Tibet can be used to test competing models of continental deformation. The shortening distribution across the Qilian Shan-Nan Shan thrust belt, derived from surface mapping and subsurface seismic reflection profiles, suggests that the modern thickness and elevation of the northern plateau has developed as a result of southward continental underthrusting of Asia beneath Tibet and distributed crustal thickening. The thrust systems in northern Tibet link to the east with > ~1000-km-long parallel left-slip strike-slip faults (i.e., the Haiyuan, Qinling, and Kunlun faults). The along-strike variation of fault offsets and pervasive off-fault deformation along these strike-slip faults create a strain pattern that departs from the expectations of the classic plate-like rigid-body motion and flow-like distributed deformation models of continental deformation. Instead, I propose that the major strike-slip faults formed as a non-rigid bookshelf-fault system where clockwise rotation of northern Tibet drives left-slip bookshelf faulting and related off-strike-slip fault deformation. In addition, I employ a stress-shadow model that uses the characteristic spacing of strike-slip faults and seismogenic-zone thickness estimates across northern Tibet and central Asia to estimate fault strength and the regional stress state. The strike-slip faults in Asia have a low coefficient of fault friction (~0.15), which may explain why deformation penetrates more than 3500 km into Asia from the Himalayan collisional front, and why the interior of Asia is prone to large (M > 7.0) devastating earthquakes along major strike-slip faults. A well-constrained understanding of Cenozoic deformation across northern Tibet allows for better reconstructions of the Proterozoic and Paleozoic tectonics. Field relationships and geochronologic studies reveal that the early Paleozoic Qilian suture, which bounds the southern margin of the North China craton, records the Ordovician-early Silurian closure of the Qilian Ocean via south-dipping subduction beneath the Qaidam continent. The evolution of this ocean and North China's southern margin has implications for reconstructions of Neoproterozoic and Paleozoic Earth, including the development of the Tethyan and Paleo-Asian Oceanic Domains. By restoring the Phanerozoic deformation along the northern and southern margins of the Tarim and North China cratons, I propose and test a hypothesis that these cratons once stretched westward across present-day Asia, possibly as far west as Baltica, as a continuous Neoproterozoic continent.
Tectonic And Climatic Evolution Of The Central Northern Tibetan Plateau
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Author : Lin Li
language : en
Publisher:
Release Date : 2016
Tectonic And Climatic Evolution Of The Central Northern Tibetan Plateau written by Lin Li and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
"The uplift history of the Tibetan Plateau serves as key evidence for understanding the dynamic models that build the Plateau and its influence on Cenozoic climate change of East Asia. This dissertation contributes to our knowledge for the growth history of the central and northern Tibetan Plateau through sedimentary analysis of basin sequences, and stable isotope analysis of carbonate rocks and modern surface waters. Field work in the Hoh Xil basin of central Tibet, including facies analysis, paleocurrent reconstruction, detrital zircon provenance analysis, and stable isotope analysis, suggests that a unified Hoh Xil basin, including both the east and west sub-basins, experienced a transition from pre-India-Asia collision foreland basin to post-collision hinterland basin setting at around 50 Ma. The Qiangtang terrane, serving as the main source for sediments deposited in the Hoh Xil basin, experienced significant topographic growth during the Cretaceous time. Far field deformation in the Hoh Xil basin was initiated shortly after India-Asia collision; contractional deformation and concomitant filling of the Hoh Xil hinterland basin provides clues for outward and upward growth of the Tibetan Plateau during Cenozoic time. Work in the western Qaidam basin provides new lithostratigraphy and carbonate stable isotope data that records early-middle Miocene topographic growth of the northern Tibetan Plateau. A hydrological change from restricted sub-basin to open marginal basin around 20 Ma was probably caused by late Oligocene-early Miocene tectonic activity around the Qaidam basinches A major topographic growth in the northern Tibetan Plateau is inferred around 15 Ma based on a negative shift in oxygen isotopic values, sedimentary facies changes from marginal lacustrine to fluvial, and an increase in sedimentation rate. A 13-12 Ma aridification event that was observed over a large area of the northern Plateau was likely caused by continued topographic growth to a critical point to block moisture from entering the northern Tibetan Plateau. To understand the caveats of stable isotope-based paleoaltimetry in the central and northern Tibetan Plateau, a comprehensive data set of 1,315 river water samples (450 newly collected) was compiled. With this large data set, a consistently assumed, but not well-documented prerequisite is demonstrated that river waters are a good substitute for isotopic studies of precipitation on the high Tibetan Plateau on the mean annual scale. The spatial variations of [delta]18O/[delta]D and d-excess values in the plateau margins can be modeled as a Rayleigh distillation process, on which stable isotope-based paleoaltimetry is based. On the contrary, the isotopic values of meteoric waters in the interior of the plateau are controlled by the combined effects of mixing of different moisture sources, contribution of recycled moisture from local surface water evaporation, and sub-cloud evaporation. A Rayleigh distillation model modified by sub-cloud evaporation is provided to simulate the isotopic variations in the western Plateau. This new understanding indicates that stable isotope-based paleoaltimetry is most reliable in the southern margins of the Plateau, and increasingly unreliable toward the northern Plateau. In addition, the contour maps of modern isotopic variations of meteoric waters across the whole Tibetan Plateau also provide validation criteria for isotopic simulations using general circulation models"--Pages v-vi.
Tectonics Of The Southern Annapurna Range Central Nepal Himalaya
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Author :
language : en
Publisher:
Release Date : 2005
Tectonics Of The Southern Annapurna Range Central Nepal Himalaya written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
Over the past two decades, several competing dynamic models have emerged to explain the tectonic evolution of the Himalayan thrust belt. Basic aspects of the geology of the range remain relatively poorly known, however, limiting the accuracy of dynamic and kinematic models. For example, the location of a mega-thrust now exposed in the interior of the range, the Main Central thrust (MCT), is only approximately known across much of the Himalaya. Both because the MCT accommodated at least 150 kilometers of slip during the mid-late Tertiary and because it carries in its hanging wall the highest-grade metamorphic rocks exposed in the range, the MCT is a prominent feature in all models that seek to explain the tectonic evolution of the Himalaya. Whole-rock Nd isotopes and detrital zircon U-Pb ages allow the discrimination of hanging wall and footwall rocks of the MCT. Application of these techniques in the Annapurna Range of central Nepal unambiguously locates the MCT. Microstructural analyses confirm the presence of a thrust-sense ductile shear zone superimposed on this isotopic boundary. With improved locations of the MCT and other faults, it is now possible to understand thermobarometric and kinematic data in more correct structural context. Thermobarometric estimates demonstrate that rocks exposed in fault-bounded blocks in the Modi Khola transect experienced approximately constant peak conditions, and that peak conditions change dramatically across large faults. Pressure-temperature estimates combined with constraints on the extent of metasomatism indicate the presence of a large normal fault one kilometer structurally above the MCT. Preliminary Th-Pb dating of monazite suggests that this normal fault may have been active during slip on the MCT. The presence of such a proximal normal fault slipping synchronously with the MCT challenges some current representations of dynamic models for the evolution of the thrust belt. In situ Th-Pb ages of monazite inclusions in garnet, chemical and age zoning in the inclusions, and textural relationships between monazite, garnet, and nearby minerals demonstrate that interpretation of the tectonic significance of Tertiary Th-Pb ages from matrix monazite is simpler than interpretation of ages from inclusions in garnet.