Reproduction de : Thèse de doctorat : Géographie : Lyon 2 : 1997. / Titre provenant de l'écran-titre. Bibliogr.

I determined the source parameters of 53 moderate-sized earthquakes in the region of the Eastern Himalayan Syntaxis through the joint inversion of regional and teleseismic distance long-period body waves. The average rates of deformation are determined by summing the moment tensors from both recent and historic earthquakes. Strike-slip movement on the Sagaing fault terminates in the north (just south of the syntaxis), where thrusting (northeast convergence) and crustal thickening are predominant. Slip vectors for thrust mechanisms in the Eastern Himalaya in general are not orthogonal to the Himalayan mountain front but show an oblique component of slip. A combination of thrust and strike-slip faulting (Molnar and Deng, 1984) for the great 1950 Assam earthquake is consistent with the rates of underthrusting in the entire Himalaya and the rate of spreading in Tibet (assuming that a 1950-type earthquake recurs every 400 years). An estimated 4-21 mm/yr of right-lateral motion between southeast Asia and the Burma subplate is absorbed within the zone of distributed shear between the Sagaing and Red River faults. A component of westward motion (3-7 mm/yr) of the western boundary of the distributed shear zone may cause some of the late Cenozoic compression and folding in the northern Indoburman Ranges. Distributed shear and clockwise rotation of blocks is also occurring in Yunnan north of the Red River Fault. The inversion of 130 regional distancewaveforms for average crustal thickness and upper mantle Pn velocity indicates an increase in Pn velocity, coincident with increase in crustal thickness, of about 0.20 km/s beneath the Tibetan Plateau. Impulsive Pn arrivals from paths that cross the Tibetan Plateau can be modeled with a positive upper mantle velocity gradient, indicating an upper mantle lid approximately 100-km-thick beneath southern Tibet. This "shield-like" structure supports a model in which Indian continental lithosphere has underthrust Tibet. The crustal shortening within Tibet 8 mm/yr is thus viewed as an upper crustal phenomenon in which the faults do not penetrate the deep crust or upper Mantle. The forces generated by the thick crust in Tibet may partly cause the strike-slip faulting and east-west convergence in Sichuan and the movement of upper crustal blocks in Yunnan.

Thesis--University of California, Berkeley. / Includes bibliographical references (leaves 315-323). Also issued in print.

Thesis--University of California, Berkeley. / Includes bibliographical references (leaves 315-323).

No description available.

Berberis L. contains more than 500 species, is the largest genus in the Berberidaceae, and is now recognised to comprise Berberis s.s. with simple leaves and compoundleaved species formally ascribed to Mahonia. Because of its sheer size, much basic taxonomy is required in Berberis, and this thesis provides a taxonomic revision for the species found in Nepal, which includes a key, full descriptions, illustrations, phenology, notes on ecology, distinguishing features and distribution maps. Twenty one species are recognised in Nepal, of which two, B. karnaliensis and B. pendryi, are newly described. Nine taxa are lectotypified during this study. Berberis has a mainly Northern Hemisphere distribution, with its main centre of distribution in the Sino-Himalaya. Berberis s.s. extends into South America where it has a secondary centre of diversity. There have been few phylogenetic studies of Berberis, and previous studies were inadequate because they did not use outgroups to root their phylogenies. This thesis provides parsimony and Bayesian analyses of chloroplast ndhF data of 64 accessions of 59 Berberis taxa, rooted using multiple outgroups including Ranzania, the putative sister group of Berberis. The results support the monophyly of Berberis s.l, but compound-leaved Berberis are shown to be paraphyletic. Berberis higginsae, a member of section Horridae, is sister to all other taxa sampled. The ndhF phylogeny, dated using a fossil calibration, indicates the North American origin of compound-leaved Berberis, and the origin of the simple-leaved South American lineages in long distance dispersal events from Eurasia. ITS sequences of 97 accessions of 79 species of Berberis are studied to investigate the origin and diversification of simple-leaved Berberis in Nepal. The Nepalese species are shown to have multiple origins from at least four different colonisations and have subsequently speciated in situ. The diversification of some groups appears to have been triggered by the active uplift phase of the Himalaya during the Miocene. The tendency of phylogenetically close Nepalese species to grow in similar ecological conditions indicates that phylogenetic niche conservatism is evident in Nepalese Berberis species. Chromosome counts for nine taxa of Nepalese simple-leaved Berberis are obtained, of which five taxa are counted for the first time. All the taxa examined are diploids with 2n=28, suggesting that the polyploidy is not an important factor in the diversification of Berberis in Nepal.

No description available.

Research was carried out in a 15,000 km2 study area in central Ladakh, India. The study area is Transhimalayan in character with ecological affinities to Tibet and Central Asia. The main study species were Ladakh urial Ovis vignei, bharal Pseudois nayaur and Himalayan ibex Capra sibirica, with additional data collected on two species occurring marginally within the study area, argali Ovis ammon and kiang Equus klang. Distributions were mapped in detail. Distribution of urial was restricted to a band along the Indus valley and its tributaries. Bharal and ibex were widely distributed and apparently share the study area. Bharal occur in the eastern part of the Zanskar Range and across the eastern plateau of Ladakh. Ibex occur mainly in the western part of the Zanskar range, along the northern slopes of the Himalayan range and the southern slopes of the Ladakh range. Argali and kiang occur across eastern Ladakh and just reach the eastern edge of the study area; both have occasionally established a presence farther west. Current estimated numbers in the study area were: 500-700 urial; 6,000-10,000 bharal, 3150-6150 ibex, <50 kiang and c. 12 argali. Urial use even terrain between 3000-4250m and avoid areas with cliffs. Ibex and bharal both use altitudes up to 5000m and prefer broken, more rugged terrain which they use as escape cover. Discriminant function analysis showed a clear differentiation between urial habitat and that of ibex and bharal, but a substantial overlap in the habitat used by ibex and bharal. The habitat preferences recorded are similar to what is known of other Caprini species. The ungulate community consisted of three main species, each occupying separate parts of the study area. The abrupt boundary between the distributions of ibex and bharal was examined in the framework of parapatry theory. Conservation prospects for mountain ungulates in the study area are currently satisfactory.

No description available.

Extensive studies have been undertaking in exploring the tectonic evolution of the Himalayan Orogen. Various tectonic models were developed to explain and constraint spatially and temporally critical events including the collision of Indian Plate with the Eurasia Plate, crustal thickening in association with the indentation, crustal spreading of the Tibetan Plateau. Recent study by King et al., 2011 identified two distinct leucogranite suites which were formed by contrasting tectonic actions at Sakya. They are Equigranular Anastomosing Leucogranite (AEG) formed under prograde fluidpresent condition while the Discrete Porphyritic Pluton Leucogranite (DPP) formed with retro-grade fluid-absent environment. Based on the characteristics of AEG and DPP, this study started with the acquisition of geochemistry data of rock samples collected for researches at various locations of the Himalaya Orogen. The two leucogranite suites were characterized through the study of their geochemistry comprised major elements, trace elements and rare earth elements models. Results of the studies concluded the existence of AEGs and DPPs distributed over the eastern area of the Himalaya Orogen beyond longitude 85 degree East. DPPs are also found at the far West location of the orogen. AEGs are typically formed from around 38Ma to 23Ma, while DPPs are of young age from 23Ma to 15Ma. Based on the observation of missing, or paucity in data for AEG and DPPs available to the west of longitude 85 degree East, it is hypothesized that recent collision of the Arabia plate to the Iran Domain inhibited the northward indentation movement of the Indian plate that not only caused the anticlockwise rotation of the Indian plate but also decreased the rate of tectonic movement of the Indian plate in the West relative to Eurasia plate. The slow rate of tectonic movement may result in insufficient thickening/energy developed within the crustal layer to cause any melting. Further studies to examine and development of the hypothesis is recommended. / published_or_final_version / Applied Geosciences / Master / Master of Science