Structural Evolution Of The Himalayan Thrust Belt West Nepal
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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
Structural Evolution Of The Himalayan Thrust Belt West Nepal
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Author : An Li
language : en
Publisher:
Release Date : 2013
Structural Evolution Of The Himalayan Thrust Belt West Nepal written by An Li and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Geology categories.
Himalayan foreland basin strata were recently documented to crop out in a structural window in the central portion of the Himalayan thrust belt. Presently, structural interpretations of the thrust belt do not explain in detail how these strata were incorporated into the thrust belt and why they are not widely exposed throughout the Himalaya. My research provides answers to these two issues. The structural window is located in the Lesser Himalaya of western Nepal and exposes rocks which lie structurally beneath the Main Central thrust (MCT) and Ramgarh thrust (RT) sheets. The thrust sheet consists of Proterozoic metamorphic rocks. Below the thrust sheet, footwall rocks exposed in the window are unmetamorphosed sedimentary rocks which consist of the early foreland basin strata (the Suntar and Swat formations) and the pre-foreland basin strata (the Melpani and Lakharpata formations). These unmetamorphosed rocks are present in the foreland basin beneath Siwalik group, ~100km to the south (towards the foreland). Two geologic maps were created; One covering the structural window and another covering the thrust belt from the High Himalaya to the MFT (Main Frontal Thrust). Several cross-sections were constructed from both maps. Structural reconstruction of these cross-sections reveal the following: 1) ~ 75 km-long hanging wall flat extends northward from its surface trace to the southern margin of the Lesser Himalayan duplex; 2) The geometry of the Jarjarkot klippe is narrower and structurally deeper than klippe to the west. The geometry of the northern flank of the klippe results from stacking of duplex horses, while the geometry of the southern flank results from slip over a ramp in the footwall of the MBT, 3) The early foreland basin strata in the window are modeled to have originated at the front of the thrust belt, and subsequently buried by the Ramgarh and MCT thrust sheets, and 4) Exposure of these strata results from growth of the duplex which brought them to a higher structural level than most parts of the thrust belt. This structural model explains why the only other exposure of foreland basin strata within the thrust belt is documented within a duplex on the north side of the Dadeldhura klippe. Moreover, this model predicts that foreland basin strata are likely to be exposed wherever duplexes exist.
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.
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.
Geometry And Kinematics Of The Fold Thrust Belt And Structural Evolution Of The Major Himalayan Fault Zones In The Darjeeling Sikkim Himalaya India
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Author : Kathakali Bhattacharyya
language : en
Publisher:
Release Date : 2010
Geometry And Kinematics Of The Fold Thrust Belt And Structural Evolution Of The Major Himalayan Fault Zones In The Darjeeling Sikkim Himalaya India written by Kathakali Bhattacharyya and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
"The Darjeeling - Sikkim Himalaya lies in the eastern part of the Himalayan fold-thrust belt (FTB) in a zone of high arc-perpendicular convergence between the Indian and Eurasian plates. In this region two distinct faults form the Main Central thrust (MCT), the structurally higher MCT1 and the lower MCT2; both these faults have translated the Greater Himalayan hanging wall rocks farther towards the foreland than in the western Himalaya. The width of the sub-MCT Lesser Himalayan rocks progressively decreases from the western Himalaya to this part of the eastern Himalaya, and as a result, the width of the FTB is narrower in this region compared to the western Himalaya. Our structural analysis shows that in the Darjeeling - Sikkim Himalaya the sub-MCT Lesser Himalayan duplex is composed of two duplex systems and has a more complex geometry than in the rest of the Himalayan fold-thrust belt. The structurally higher Daling duplex is a hinterland-dipping duplex; the structurally lower Rangit duplex varies in geometry from a hinterland-dipping duplex in the north to an antiformal stack in the middle and a foreland-dipping duplex in the south. The MCT2 is the roof thrust of the Daling duplex and the Ramgarh thrust is the roof thrust of the Rangit duplex. In this region, the Ramgarh thrust has a complex structural history with continued reactivation during footwall imbrication. The foreland-dipping component of the Rangit duplex, along with the large displacement associated with the reactivation of the Ramgarh thrust accounts for the large translation of the MCT sheets in the Darjeeling - Sikkim Himalaya. The growth of the Lesser Himalayan duplex modified the final geometry of the overlying MCT sheets, resulting in a plunge culmination that manifests itself as a broad N-S trending "anticline" in the Darjeeling - Sikkim Himalaya. This is not a "river anticline" as its trace lies west of the Teesta river. A transport parallel balanced cross section across this region has accommodated a total minimum shortening of ~502 km (~82%) south of the South Tibetan Detachment system (STDS). Based on this shortening, the average long-term shortening rate is estimated to be ~22mm/yr in this region. The available shortening estimates from different parts of the Himalayan arc show significant variations in shortening, but based on the present available data, it is difficult to evaluate the primary cause for this variation. The shortening in the Himalayan fold - thrust belt (FTB) is highest in the middle of the Himalayan arc (western Nepal) and progressively decreases towards the two syntaxes. Although the width of the Lesser Himalayan belt decreases in the eastern Himalaya, the Lesser Himalayan shortening percentage remains approximately similar to that in the Nepal Himalaya. In addition, the shortening accommodated within the Lesser Himalayan duplex progressively increases from the western to the eastern Himalaya where it accommodates nearly half of the total shortening. The regional restorations suggest that the width of the original Lesser Himalayan basin may have played an important role in partitioning the shortening in the Himalayan FTB. In addition, the retrodeformed cross section in the Darjeeling - Sikkim Himalaya provides insights into the palinspastic reconstruction of the Gondwana basin of Peninsular India, suggesting that this basin extended ~150 km northward of its present northernmost exposure in this region. The balanced cross section suggests that each of the MCT sheets has undergone translation of >̲ 100km in this region. Although a regional scale flat-on-flat relationship is seen in the MCT sheets, there is a significant variation in overburden from the trailing portion to the leading edge of the MCT due to the geometry of the tapered crystalline orogenic wedge. Microstructural studies from three segments of the MCT2 fault zone suggest that the MCT2 zone has undergone strain softening by different mechanisms along different portions of its transport-parallel length, mainly as a result of changing overburden conditions. This regional strain softening provides a suitable explanation for the large translation of >̲100 km along a relatively thin MCT2 fault zone in the Darjeeling - Sikkim Himalaya."--Leaves vi-viii.
Tectonics Of The Himalaya
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Author : S. Mukherjee
language : en
Publisher: Geological Society of London
Release Date : 2015-09-28
Tectonics Of The Himalaya written by S. Mukherjee 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 2015-09-28 with Science categories.
The Himalayan mountain belt, which developed during the India–Asia collision starting about 55 Ma ago, is a dramatically active orogen and it is regarded as the classic collisional orogen. It is characterized by an impressively continuous 2500 km of tectonic units, thrusts and normal faults, as well as large volumes of high-grade metamorphic rocks and granites exposed at the surface. This constitutes an invaluable field laboratory, where amazing crustal sections can be observed directly in very deep gorges. It is possible to unravel the tectonic and metamorphic evolution of litho-units, to observe the mechanisms of exhumation of deep-seated rocks and the propagation of the deformation. Himalayan tectonics has been the target of many studies from numerous international researchers over the years. In the last 15 years there has been an explosion of data and theories from both geological and geophysical perspectives. This book presents the results of integrated multidisciplinary studies, including geology, petrology, magmatism, geochemistry, geochronology and geophysics, of the structures and processes affecting the continental lithosphere. These processes and their spatial and temporal evolution have major consequences on the geometry and kinematics of the India–Eurasia collision zone.
Structural Evolution Of The Central Nepal Fold Thrust Belt And Regional Tectonic And Structural Significance Of The Ramgarh Thrust Phd
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Author : Ofori Pearson
language : en
Publisher:
Release Date : 2002
Structural Evolution Of The Central Nepal Fold Thrust Belt And Regional Tectonic And Structural Significance Of The Ramgarh Thrust Phd written by Ofori Pearson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with categories.
Geology Of The Nepal Himalaya
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Author : Megh Raj Dhital
language : en
Publisher: Springer
Release Date : 2015-02-11
Geology Of The Nepal Himalaya written by Megh Raj Dhital and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-02-11 with Science categories.
This book addresses the geology of the entire Himalayan range in Nepal, i.e., from the Gangetic plain in the south to the Tethyan zone in the north. Without a comprehensive look at the various Himalayan zones, it is practically impossible to fully grasp the processes at work behind the formation and development of the spectacular Himalaya. However, the goal is not merely to document all the scientific ontology but rather to reveal a sound basis for the prevailing concepts. Both the early literature on Himalayan geology and contemporary trends are fully covered. For the first time, the origin, use, and abuse of common Himalayan geological terms such as the Siwaliks, Lesser Himalaya, Main Boundary Thrust, Main Central Thrust, and Tethys are discussed. The book will help readers to progress from a cognitive approach to a constructive one by linking various types of knowledge, such as seeking relations between various geological structures as well as between earlier thoughts or views and contemporary approaches.
Understanding An Orogenic Belt
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Author : Ashok Kumar Dubey
language : en
Publisher: Springer
Release Date : 2014-07-08
Understanding An Orogenic Belt written by Ashok Kumar Dubey and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-07-08 with Science categories.
The book provides a model for the structural evolution of the Himalaya with relevant background information making it easily accessible to earth scientists specializing in other areas. The book is divided into two parts: The first part describes the basic principles of structural geology that are required to understand the evolutionary model described in the second part. The book incorporates some of the commonly ignored structural features, such as Pre-Himalayan rift tectonics, reactivation of faults, simultaneous development of folds and thrust faults, superposed folds, strike-slip faults developed during early and superposed deformation, problems with GPS data, erratic crustal shortening obtained by restoration of deformed sections, etc. The proposed model is essentially based on inversion tectonics and provides answers to some previously unresolved questions. It describes in detail the structure of the Himalaya as a primary arc, with supporting evidence from model deformation under controlled boundary conditions and anisotropy of magnetic susceptibility studies.
Structural Evolution Of The Kohat And Potwar Fold And Thrust Belts Of Pakistan
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Author : Humaad Ghani
language : en
Publisher:
Release Date : 2019
Structural Evolution Of The Kohat And Potwar Fold And Thrust Belts Of Pakistan written by Humaad Ghani and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
Fold and thrust belts are characteristic features of collisional orogen that grow laterally through time by deforming the upper crust in response to stresses caused by convergence. The deformation propagation in the upper crust is accommodated by shortening along major folds and thrusts. The formation of these structures is influenced by the mechanical strength of décollements, basement architecture, presence of preexisting structures and taper of the wedge. These factors control not only the sequence of deformation but also cause differences in the structural style. The Himalayan fold and thrust belt exhibits significant differences in the structural style from east to west. The external zone of the Himalayan fold and thrust belt, also called the Subhimalaya, has been extensively studied to understand the temporal development and differences in the structural style in Bhutan, Nepal and India; however, the Subhimalaya in Pakistan remains poorly studied. The Kohat and Potwar fold and thrust belts (herein called Kohat and Potwar) represent the Subhimalaya in Pakistan. The Main Boundary Thrust (MBT) marks the northern boundary of both Kohat and Potwar, showing that these belts are genetically linked to foreland-vergent deformation within the Himalayan orogen, despite the pronounced contrast in structural style. This contrast becomes more pronounced toward south, where the active strike-slip Kalabagh Fault Zone links with the Kohat and Potwar range fronts, known as the Surghar Range and the Salt Range, respectively. The Surghar and Salt Ranges developed above the Surghar Thrust (SGT) and Main Frontal Thrust (MFT). [...]