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"China Boundaries India."
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Timing of India-Asia collision: Geological, biostratigraphic, and palaeomagnetic constraints
A range of ages have been proposed for the timing of India‐Asia collision; the range to some extent reflects different definitions of collision and methods used to date it. In this paper we discuss three approaches that have been used to constrain the time of collision: the time of cessation of marine facies, the time of the first arrival of Asian detritus on the Indian plate, and the determination of the relative positions of India and Asia through time. In the Qumiba sedimentary section located south of the Yarlung Tsangpo suture in Tibet, a previous work has dated marine facies at middle to late Eocene, by far the youngest marine sediments recorded in the region. By contrast, our biostratigraphic data indicate the youngest marine facies preserved at this locality are 50.6–52.8 Ma, in broad agreement with the timing of cessation of marine facies elsewhere throughout the region. Double dating of detrital zircons from this formation, by U‐Pb and fission track methods, indicates an Asian contribution to the rocks thus documenting the time of arrival of Asian material onto the Indian plate at this time and hence constraining the time of India‐Asia collision. Our reconstruction of the positions of India and Asia by using a compilation of published palaeomagnetic data indicates initial contact between the continents in the early Eocene. We conclude the paper with a discussion on the viability of a recent assertion that collision between India and Asia could not have occurred prior to ∼35 Ma.
Journal Article
Where China meets India : Burma and the new crossroads of Asia
\"An account of the Asian frontier's long and rich history and its modern significance.\"--Publisher's description.
Book
boundary between the Indian and Asian tectonic plates below Tibet
The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S receiver function techniques beneath central and western Tibet along two new profiles and discuss the results in connection with results from earlier profiles, which did observe the LAB. The LAB of the Indian and Asian plates is well-imaged by several profiles and suggests a changing mode of India-Asia collision in the east-west direction. From eastern Himalayan syntaxis to the western edge of the Tarim Basin, the Indian lithosphere is underthrusting Tibet at an increasingly shallower angle and reaching progressively further to the north. A particular lithospheric region was formed in northern and eastern Tibet as a crush zone between the two colliding plates, the existence of which is marked by high temperature, low mantle seismic wavespeed (correlating with late arriving signals from the 410 discontinuity), poor Sn propagation, east and southeast oriented global positioning system displacements, and strikingly larger seismic (SKS) anisotropy.
Journal Article
India China : rethinking borders and security
\"Challenging the Westphalian view of international relations, which focuses on the sovereignty of states and the inevitable potential for conflict, the authors from the Borderlands Study Group reconceive borders as capillaries enabling the flow of material, cultural, and social benefits through local communities, nation-states, and entire regions. By emphasizing local agency and regional interdependencies, this metaphor reconfigures current narratives about the China India border and opens a new perspective on the long history of the Silk Roads, the modern BCIM Initiative, and dam construction along the Nu River in China and the Teesta River in India. Together, the authors show that positive interaction among people on both sides of a border generates larger, cross-border communities, which can pressure for cooperation and development. India China offers the hope that people divided by arbitrary geo-political boundaries can circumvent race, gender, class, religion, and other social barriers, to form more inclusive institutions and forms of governance\"-- Provided by publisher.
Book
Greater India Basin hypothesis and a two-stage Cenozoic collision between India and Asia
Cenozoic convergence between the Indian and Asian plates produced the archetypical continental collision zone comprising the Himalaya mountain belt and the Tibetan Plateau. How and where India–Asia convergence was accommodated after collision at or before 52 Ma remains a long-standing controversy. Since 52 Ma, the two plates have converged up to 3,600 ± 35 km, yet the upper crustal shortening documented from the geological record of Asia and the Himalaya is up to approximately 2,350-km less. Here we show that the discrepancy between the convergence and the shortening can be explained by subduction of highly extended continental and oceanic Indian lithosphere within the Himalaya between approximately 50 and 25 Ma. Paleomagnetic data show that this extended continental and oceanic \"Greater India\" promontory resulted from 2,675 ± 700 km of North–South extension between 120 and 70 Ma, accommodated between the Tibetan Himalaya and cratonic India. We suggest that the approximately 50 Ma \"India\"–Asia collision was a collision of a Tibetan-Himalayan microcontinent with Asia, followed by subduction of the largely oceanic Greater India Basin along a subduction zone at the location of the Greater Himalaya. The \"hard\" India–Asia collision with thicker and contiguous Indian continental lithosphere occurred around 25–20 Ma. This hard collision is coincident with far-field deformation in central Asia and rapid exhumation of Greater Himalaya crystalline rocks, and may be linked to intensification of the Asian monsoon system. This two-stage collision between India and Asia is also reflected in the deep mantle remnants of subduction imaged with seismic tomography.
Journal Article
Geodynamic model and tectono-structural framework of the Bengal Basin and its surroundings
We present a brief, but precise description of the geodynamic evolution, and tectono-structural framework of the Bengal Basin. The tectonic map (Main Map) at 1:12,50,000 scale should be considered as a first attempt to provide a more comprehensive and accurate geotectonic cartography of the entire region, with respect to the available maps in the published literatures, and in the light of scientific advances in geodynamics, tectonics and structures reached in the last decades plus new geological field works carried out in some key sectors of the Bengal Basin. The tectonic map of the Bengal Basin improves the knowledge of the geometry of the basin boundary, tectonic settings and relevant structures, and its relation to the collision of the Indian and the Burmese plates. Three schematic geological cross-sections illustrate the tectonic architecture of the basin in depth as well as surroundings. The latest understanding of the present-day geodynamics would help to develop advanced kinematic and dynamic modelling of the Bengal Basin in relation to the pre- and post-collisional stages of the Indian Plate.
Journal Article
Ultralow velocity zone and deep mantle flow beneath the Himalayas linked to subducted slab
The origins of ultralow velocity zones, small-scale structures with extremely low seismic velocities found near the core–mantle boundary, remain poorly understood. One hypothesis is that they are mobile features that actively participate in mantle convection, but mantle flow adjacent to ultralow velocity zones is poorly understood and difficult to infer. Although deep mantle anisotropy observations can be used to infer mantle flow patterns, ultralow velocity zone structures are often not examined jointly with these observations. Here we present evidence from seismic waves that sample the lowermost mantle beneath the Himalayas for both an ultralow velocity zone and an adjacent region of seismic anisotropy associated with mantle flow. By modelling realistic mineral physics scenarios using global wavefield simulations, we show that the identified seismic anisotropy is consistent with horizontal shearing orientated northeast–southwest. Based on tomographic data of the surrounding mantle structure, we suggest that this southwestward flow is potentially linked to the remnants of the subducted slab impinging on the core–mantle boundary. The detected ultralow velocity zone is located at the southwestern edge of this anisotropic region, and therefore potentially affected by strong mantle deformation in the surrounding area.
The presence of an ultralow velocity zone and seismic anisotropy in the lowermost mantle beneath the Himalayas is linked to subducted slab remnants and southwest mantle flow, according to analyses of seismic waves and mantle anisotropy measurements.
Journal Article
Geographical Diversions
Working at the intersections of cultural anthropology, human geography, and material culture, Tina Harris explores the social and economic transformations taking place along one trade route that winds its way across China, Nepal, Tibet, and India. How might we make connections between seemingly mundane daily life and more abstract levels of global change? Geographical Diversions focuses on two generations of traders who exchange goods such as sheep wool, pang gdan aprons, and more recently, household appliances. Exploring how traders \"make places,\" Harris examines the creation of geographies of trade that work against state ideas of what trade routes should look like. She argues that the tensions between the apparent fixity of national boundaries and the mobility of local individuals around such restrictions are precisely how routes and histories of trade are produced. The economic rise of China and India has received attention from the international media, but the effects of major new infrastructure at the intersecting borderlands of these nationstates-in places like Tibet, northern India, and Nepal-have rarely been covered. Geographical Diversions challenges globalization theories based on bounded conceptions of nation-states and offers a smaller-scale perspective that differs from many theories of macroscale economic change.
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