No description available.

The Yidun Terrane in the eastern Tibetan plateau is separated from the Songpan-Ganzi Terrane by the Ganzi-Litang suture zone to the east and Qiangtang Block by the Jinsha suture zone to the west. Both suture zones are marked by eastern Paleo-Tethyan ophiolites. The western part of the Yidun Terrane, the Zhongza Massif, is dominated by Paleozoic sedimentary sequences. In the eastern part, Triassic subduction-related plutonic rocks and volcanic-flysch successions of the Yidun Group are important elements for understanding the evolution of eastern Paleo-Tethys and amalgamation of East Asia. The Yidun Group includes the Lieyi, Qugasi, Tumugou and Lanashan Formations from base upwards. Two major depocenters for the Yidun Group can be recognized. Sedimentary detritus supplying for the northern depocenter were dominantly sourced from the Zhongza Massif and received recycling components in a passive margin setting. In the southern depocenter, the Qugasi Formation accumulated materials from the Zhongza Massif, whereas the Tumugou Formation received additional materials from locally distributed Triassic arc rocks and crystalline basement rocks, which indicates transition from a passive margin to a magmatic arc setting. In the southern Yidun Terrane, (quartz-) dioritic hypabyssal intrusions are spatially associated with andesites and dacites and have zircon U-Pb ages from ~230 to 215 Ma. They have adakitic geochemical features and are divided into the ~230-215 Ma high silica (HSA) and ~215 Ma low silica (LSA) adakitic rocks. The HSA formed from subducted slab melts with limited interaction with the overlying mantle wedge, whereas the LSA were generated from slab melts with more extensive interaction with mantle due to slab break-off at ~215 Ma. In the northern Yidun Terrane, granitic plutons and volcanic rocks occur in two parallel N-S belts. The ~228 Ma volcanic rocks in the Xiangcheng region are adakites generated from slab melts, whereas the ~231-230 Ma volcanic rocks in the Changtai region, including basalts, andesites, dacites and rhyolites, formed in a back-arc setting. The Changtai basalts were produced by low degrees of partial melting of an OIB-like mantle source with minor involvement of subducted slab components. The Changtai andesites/dacites represent evolved members from the basaltic magmas through an AFC process, whereas the rhyolites formed from anatexis of a garnet-bearing crustal source. These volcanic rocks are 4-6 mys older than arc granitic rocks in the northern Yidun Terrane. The spatio-temporal framework of all the subdution-related igneous rocks suggests initiation of subduction of the Ganzi-Litang oceanic lithophere under the southern Yidun Terrane at ~230 Ma, resulting in the adakitic magmatism in the Shangri-La and Xiangcheng regions and the back-arc magmatism in the Changtai region. Subsequently at ~224 Ma, the subduction extended to the northern Yidun Terrane, leading to the formation of the arc granitic plutons. From south to north, the Yidun Terrane was sequentially amalgamated with the Songpan-Ganzi Terrane during the Late Triassic. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Transportation is an integral par t of the tourism industry. It is largely due to the improvement of transportation that tourism has expanded. The impacts on the ecology, degradation of destination sites, tourist experience, and economy has called for a better management of this resource. Transportation can be divided into two parts. One is the mobility infrastructure such as railway and highway, connecting and sometimes dividing the tourism destination. And another is site infrastructure which is in the tourism destination and guides the tourists to explore the place. Few places are as globally significant as the Tibetan Plateau, writes Daniel J Miller. Understanding this means looking at the region from a holistic, ecological standpoint. It has huge biodiversity resource and stores a lot of ice on the mountain. Religious affect this area so that it can remain in the harmony of the people and the nature. The Qinghai-Tibet railway is built for the policy or economic reason after is construction finished in 1st of July, 2006. This transportation greatly changed this area. The tourists’ trend increases 30% in Qinghai and 40% in Tibet in 2007. The income of the tourism also increased. Then the conflict occurred, on the ecological aspect: the wildlife, the One is the stepping destroy by the tourist which may cause soil erosion or vegetation destroy. And the social aspect, tourism reform the local people’s life, increases their income but also challenges the line of their religious faith. The stations along the railway became my focus point. They were like the start point, we can see the government intention, and the economic opportunity. In the meanwhile, it could also be the pollution resource and damage beginning. We can’t just simply stop people from going there. Since the railway is just like a window, advertising the beautiful landscape. If the station can’t access, people will find another way to access, in an uncontrolled way. So it is also an opportunity for expressing a new definition of tourism. Education, love, ecotourism. To make the place love for the people, so that they will have the ownership, they want this landscape keeps forever, so that it be an eternity. My thesis is trying to reach a more sustainable way to develop tourism in this very sensitive area, to create a couple of well-designed station stops which does strict (no access) protection for these areas. My intention is to create a system that combines education and the exploration in tourism. / published_or_final_version / Architecture / Master / Master of Landscape Architecture

青藏高原是地球上海拔最高的地理單元,平均海拔超過4000米,連同周邊的高大山脈被稱為地球的「第三極」。青藏高原擁有的冰川儲量僅次於南極、格陵蘭地區及加拿大。高原也是亞洲幾大主要水系的發源地,因而被譽為亞洲「水塔」。在高原腹地的寬谷有密集的湖泊群,其中面積大於1km²的湖泊超過1000個,以內流湖為主。其湖泊面積占中國湖泊總面積的50%左右。陸地水儲量及年際動態是全球水量平衡的重要組成部分,但是在高緯度的青藏高原地區由於缺乏精細的觀測,還存在諸多疑問。因而,針對青藏高原地區,採用新的觀測手段和方法調查高寒水文系統中冰川和湖泊所引起的水儲量變化對理解全球水分平衡和氣候變化影響十分必要。本研究將利用多種遙感衛星觀測系統回答高原水文研究中存在的一些關鍵問題。 / 青藏高原自上世紀八十年代出現快速升溫,從多方面的研究以達成共識。然而,由於資料的不確定性及高原地區降雨本身的空間異質性,降雨的時空變化尚存在不一致的結論。本研究對八種常用的降雨產品的時空相關性進行相互比較,也採用有限的網站觀測對格網降雨資料集進行評價。結果顯示,GPCP, CMAP-1, CMAP-2和PREC/L四個降雨資料集與網站觀測降雨具有更好的相關性,APHRODITE 和TRMM資料次之,兩個再分析降雨資料最不相關。基於GPCP, CMAP-1, PREC/L和APHRODITE降雨資料,分析青藏高原及周邊地區降雨在1979 - 2011期間的變化趨勢。四個資料集一致反映在高原中部及東北部地方,降雨在上世紀90年代開始出現明顯的增長趨勢,在藏東南地區降雨減少,但趨勢不明顯。而在喜馬拉雅地區,四個降雨資料反映的趨勢不一致。本研究進一步分析降雨對青藏高原地區陸地水儲量的在2003 - 2011期間的影響關係發現,高原中部及東北部的降雨增加及天山地區的降雨減少與GRACE衛星觀測的陸地水儲量變化有十分密切的關係。而在喜馬拉雅山脈及藏東南地區,降雨的變化對陸地水儲量的相關性相對較低,一方面可能是降雨資料在該地區由於更複雜的地形具有更大的不確定性,另外一方面,可能存在其他氣候因素(如變暖引起的冰川融水損失等)影響陸地水量的平衡。 / 因此,選擇藏東南地區為研究典型區,調查青藏高原冰凍圈水文系統的陸地水儲量平衡狀態及其與冰川變化關係。利用2003 - 2009時段內GRACE衛星觀測,藏東南地區的物質平衡以5.99 ± 2.78 Gt/yr的速率減少。然而,基於GLDAS/Noah和CPC的模型輸出資料進行分析發現,該地區的土壤含水量、雪水當量及植被冠層含水量等水文因數均無顯著的降低(或增加)趨勢。而根據ICESat測高衛星對藏東南地區冰川的表面高程進行測量得出,冰川在2003 - 2009期間以平均- 0.31 ± 0.14 m/yr的速率消融,相當於- 4.83 ± 2.46 Gt/yr的負物質平衡量。可以推斷,冰川消融引起的水量流失大約能解釋該地區80%的GRACE衛星觀測的物質負平衡量。進一步分析GRACE衛星連續觀測的區域陸地水儲量平衡與氣候因數的統計關係表明,時間序列中的突變、季節性波動及多年週期振盪信號與降水的變化具有高度的相關性,而區域物質平衡的年際收支及長期趨勢更明顯受溫度的控制。該結論進一步證實藏東南地區近年來的陸地水儲量負平衡很大程度上由增加冰川融水流失引起的。 / 在青藏高原內陸湖泊水文研究方面,由於缺乏長期的湖泊水量平衡、水位及湖底地形等實測資料,大尺度定量估算湖泊水量變化的難題一直尚未解決。上世紀70年代以來的光學遙感影像及2003 - 2009期間的ICESat衛星測高資料成為大尺度觀測青藏高原湖泊面積及水位變化的有力工具。遙感觀測結果表明,整個高原湖泊(選取312個大於10 km²的湖泊)面積從1970年代早期的35,638.11 km²增加到2011年的41,938.66 km²。ICESat測高資料覆蓋的湖泊平均水位變化速率為0.23 m/yr。其中,青藏高原中部地區的湖泊,如色林錯,擴張速度最快,而藏南地區的湖泊在2000年代出現迅速萎縮趨勢。基於2003 - 2009期間的湖泊面積及對應的水位資料,建立湖泊水位隨面積變化的統計關係,從而重建湖泊在缺少ICESat測高資料的時段(2003年之前及2009年之後)的湖泊水位資料,有效估算青藏高原湖泊從1970年代約40年來水量增加92.43 Gt (主要增長髮生在2000年代)。對湖泊群密集的羌塘高原湖泊水量平衡進一步分析,該地區湖泊水量在2000年代以6.79 Gt/yr的速率增加,該類比結果與GRACE觀測的該地區物質正平衡趨勢6.81 Gt/yr十分接近。 / 為了解釋青藏高原地區內陸湖泊在2000年代迅速擴張的主要氣候影響機制,針對117個具有測高資料,分析其湖泊水位的趨勢、突變及季節性變化與氣候變數的關係。結果表明,高原湖泊水位的季節性變化表現明顯的時空異質性:昆侖山南部的密集的小湖泊群在暖(濕)季水位降低,而冷(幹)季水位增加,可能更多依賴于季節性雪蓋融水補給,而暖季該地區強烈蒸發作用造成水量負平衡;其他大部分湖泊暖季由於降水徑流補給水位升高,而冷季水位降低或較小地波動。根據水位季節性變化和突變,湖泊可以劃分為8個聚類,不同聚類表現出不同的水位變化態勢,一些明顯的水位增減與該地區降水和蒸發高低密切相關,而冰川融水補給(表現為溫度波動)並未表現出顯著的相關性。將高原範圍內的湖泊劃分為冰川補給型與非冰川補給型湖泊,兩類湖泊群的水位變化在統計上沒有明顯分異。而水位變化速率與湖泊的補給係數(一定程度上反映湖泊降水徑流對水量平衡的影響)具有顯著相關。從不同的氣候子區具體分析,在高原中部地區,冰川融水補給確實更加加劇了降水引起的湖泊水位增長。此外,集成多顆衛星的測高資料,對18個高原典型大湖泊的水位年際增量與氣候因數進行相關分析發現,水位波動呈現出與降水和蒸發更顯著的相關性。總之,該研究綜合多種新型技術手段,在大尺度上調查青藏高原高寒水文系統(主要針對季風型溫性冰川與內陸湖泊)水量變化及其空間異質性特徵,並解釋其氣候影響因素。 / The Tibetan Plateau (TP) and surrounding mountains are known as the Third Pole, with an average elevation of 4,000 meters above sea level. It holds the largest reserves of glacier ice outside of Antarctica, Greenland, and Canada. It is thus referred as Asian water towers, which form the source of more than ten major rivers in Asia. In the broad basins of the inner plateau, there are more than one thousand lakes, mostly featured by closed watersheds. In the context of climate change and variability, regional terrestrial water storage (TWS) budgets of the TP are critical terms in the global water balance, yet they are poorly observed at high altitude. Thus new strategies are required to investigate changes of mountain glaciers and lakes in the high-altitude hydrologic system. Multiple remote sensing techniques are deployed here to address questions in high-latitude hydrology. / The temperature of the TP has risen rapidly since the 1980s, but spatio-temporal variability of precipitation remains unclear partly due to more spatial incoherence in precipitation variation. Eight gridded precipitation datasets are inter-compared with each other and evaluated by gauge-based data over the TP and surroundings between 1979 and 2011. The results show that the GPCP, CMAP-1/2 and PREC/L precipitation data agreebetter with gauge-based precipitation. The two reanalysis data have the weakest correlations with gauge-based data, and the APHRODITE and TRMM data are in between. Analyses of precipitation trends based on the GPCP, CMAP-1, PREC/L and APHRODITE datasets consistently reveal that an obvious increase is observed in the inner TP since the mid-1990s and insignificant decreasing trends areobserved in the southeastern TP. In the Himalayas, the precipitation trends are rather inconsistent among the four datasets. Comparisons of the GRACE TWS changes and precipitation variability between 2003 and 2011 show that increasing precipitation in the central and northeastern TP and decreasing precipitation in the Tienshan Mountains are tightly associated with the TWS variations in the two regions. However, there are relatively lower correlations between TWS changes and precipitation in the Himalayas and southeastern TP. It implies that there areprobably other factors (such as glacier meltwater loss induced by warming climate) which are also correlated with the GRACE-observed mass changes. / The southeastern TP (SETP) is selected as a demonstrative area to investigate the TWS changes in the cryo-hydrologic system and relations with glacier variations. The GRACE observations during 2003 - 2009 reveal a serious mass loss with rate of - 5.99 ± 2.78 Gt/yr in the SETP. Based on hydrological data by model calculations from the GLDAS/Noah and CPC, other hydrologic elements, including soil moisture, snow water equivalent and canopy water storage, showed no obvious change trends. The glacier measured by the ICESat altimetry showed a thinning rate of - 0.31 ± 0.14 m/yr during 2003 - 2009. An approximate estimation of the glacier mass budget was - 4.83± 2.46 Gt/yr, which accounted for ~ 80% of the GRACE-observed mass loss in this area. The further examinationon climate forces of TWS changes in the SETP suggest that abrupt, seasonal and multi-year undulating signals of GRACE TWS anomaly time series were tightly associated with precipitation variability, while the annual mass budgets and trends were more related to temperature variability. / In contrast to glacial meltwater loss in outflow areas of the SETP, the hydrological processes in the inner TP are characterized by closed lake systems. In-situ measurements of lake water balance and lake bathymetry are missing to monitor the TWS changes in lake-hydrologic system of the TP. Remote sensing allows observation of area and water level variations in Tibetan lakes (312 lakes larger than 10 km²). The total lake area increased from 35,638. 11km² in the early-1970s to 41,938.66 km² in 2011. The mean rate of change in water level for all examined lakes was 0.23 m/yr between 2003 and 2009. The most dramatic lake expansion was observed in the central TP. Lakes in South Tibet showed shrinking tendency in the past decade. Then, based on the time series of lake area and water level, the statistical relationships between lake area and water level are established to estimate lake water volume (storage) variations and compare with GRACE-observed mass gains in this area. The results show that the total water storage increased by 92.43 Gt (km³) from the early 1970s to 2011.The positive water mass budget of 6.81 Gt/yr in the Changtang Plateau derived from GRACE data agrees well with the change rate of lake water storage (6.79 Gt/yr) derived from the statistical models in the 2000s. / Based on satellite altimetry data, the trends, abrupt and seasonal changes of water level for 117 lakes with elevation measurements are examined to explore the potential climate forces of lake variations in the 2000s. Results suggest that seasonal water-level variations were featured by strong spatio-temporal heterogeneity which was largely associated with the seasonally and spatially varied climate. The rates of change of non-glacier-fed lakes in the 2000s were basically as high as those of glacier-fed lakes across the plateau while the lake level changes were closely associated with the lake supply coefficients (the basin / lake area ratio, which partly indicates the role of precipitation and runoff on lake water balance). The lake variations agreed well with the spatial pattern of precipitation changes.In addition, the correlation analyses between water level variations and climatic variables for 18 typical large lakes indicate that lake dynamics were more related to precipitation and evaporation than temperature. In sum, this study provides new insight and large-scale investigation on high-altitude hydrologic systems of the TP. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Song, Chunqiao. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 181-203). / Abstracts also in Chinese.

Previous studies on reconstructing the paleoclimate on the Tibetan Plateauare commonly based on a single proxy, and have thus limited the usage of their results. Therefore this study was designed firstly to evaluate the applicability of organic carbon isotopes from modern plants in the Tibetan Plateau as a paleo-environmental proxy, and secondly to apply palynology, organic geochemistry and biomarkers to the reconstructions ofpaleo-environmental history of central Tibet. The new, comprehensive records reveal the history of regional precipitation, temperature and vegetation change in responding to Holocene climatic changesin the region. Organic carbon isotope (δ13C) and lipid n-alkanes were measured from plant samples collected from various altitudes and environments across the study area. The δ13C results indicate the importance of availability of water to C3/C4 herbs distribution in this alpine region. The molecular distributions of trees, shrubs, herbs and submergent macrophytes show distinctive features in a number of indices. These indices are considered to be useful for paleo-environmental reconstructions. A 5.8m-long peat core, which were dated back to 95,000 yr BP was obtained from a river valley at an altitude of 4300 m above sea level. The pollen data from the core reveals a sparse herbaceous vegetation in the catchment area during early Holocene, suggesting non-favourable conditions for vegetation growth. The environment became wetter during the early mid-Holocene around 8100-7000 cal. yr BP, and since then a sedge-dominated wetland habitat was developed. This vegetation changed little until about 1100 cal. yr BP; from which an increase of drought-tolerant herbs was indicated by the pollen data, implying a slightly drier condition of the latter part of late Holocene. The pollen record suggests that the optimum precipitation in central Tibet occurred later and lasted longer than that in the East Asian Monsoon region. Finally, bulk sample carbon geochemistry(TOC, δ13C) as well as the biomarkers analysis on n-alkanes and GDGTs as paleo-limnology and paleo-temperature indicators respectively were applied to the core. Before 1500 cal. yr BP, the wetland was dominated by both vascular herbs as suggested by the δ13Cdata and aquatic floating/submerged macrophytes as indicated by mid-chain n-alkanes. The relative proportion of the two sources of organic matter input varied slightly, and vascular herbs increased in two episodes(5400 -4700 and 2800 -2300 cal. yr BP) indicated by the increase of long-chain n-alkanes (>n-C25). Considering of the soil water content variation by the ratios of iGDGTs to bGDGTs, the change between the two plant communities could to be caused by different lake status. GDGTs paleo-temperature reconstruction indicates a warm period from 6700 to 6000 cal. yr BP, which is believed to be the warmest and highly humid in central Tibetan region. Then the temperature decreased towards the late Holocene, consistent with other paleo climate records across the Plateau region, i.e. largely controlled by change of solar insolation. Along the decreasing trend, a warm episode at about 1200 yr BP that inferred from MAAT was suggested corresponding with the North Hemisphere Medieval Warming. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 132-150).

New applications of the optically stimulated luminescence (OSL) dating were carried out with the aim of understanding late Quaternary activities for the Tibetan Plateau. This included studying the slip rate of the Altyn Tagh Fault, northeast Tibetan Plateau, and revealing the environmental changes derived from large inland lake’s evolution, central south Tibet. Two deflected streams across the Altyn Tagh Fault close to Aksay (39°24.572’N, 94°16.012’E) were investigated. Geomorphological analysis suggests that loess covering deflected stream banks has recorded past faulting events. A conceptual model is proposed illustrating the relationship. OSL dating of sixteen loess samples at both streams support the model, suggesting the loess is deposited episodically after fault strikes and subsequent channel wall refreshment. The age and offset indicate a slip rate of 11 ±2 mm/yr for this part of the Altyn Tagh Fault. Another river section near Aksay was also investigated for the slip rate information. Two risers between three terraces are clearly offset; OSL dating of loess covering terrace surfaces yielded terrace ages. Using the upper-terrace age to represent riser displacement duration, the rate is estimated to be 12 ±1 mm/yr. The result suggests that using upper terrace is more suitable in this region. Notably, though, the slow rate is at odds with proposals that assume high-speed extrusion (~23 mm/year) of the Tibetan Plateau being accommodated by the Altyn Tagh Fault. Palaeo-shorelines around the third largest lake in Tibet, Zhari Namco, were for the first time systematically investigated using OSL dating. Twenty-two sediment samples from eleven shorelines indicate that the water level has dropped ~128 m and the lake has undergone stepwise shrinkage since 8.2 ka. Digital elevation model calculation indicates the lake has shrunk from 4605 km2 in size at 8.2 ka to 996 km2 at present, which is equivalent to ~300 km3 of water. This implies a significant reduction in precipitation over the past 8.2 ka, a result of weakening Indian Monsoon or a shift of monsoon circulation path. The result is consistent with other lake-core, ice-core climate proxies and solar insolation changes, implying the dominance of a weakening Indian Monsoon over central Tibet in the Holocene. Using the elevation of the highest shoreline of the four largest lakes in Tibet, the early Holocene Pan-lake hypothesis is proposed for the central Tibet. In addition to these applications of OSL dating, technical studies on sensitivity changes and residual doses have been carried out for potassium rich feldspar (K-feldspar). Recent development of infrared stimulated luminescence (IRSL) signals from K-feldspar has shown great potential for extending the datable range for OSL dating. Sensitivity changes and residual doses of post-IR IRSL and multi-elevated -temperature post-IR IRSL protocols for K-feldspar were studied. A sensitivity decrease is observed after adopting a high temperature IRSL. IRSL signals stimulated at high temperature are found to contain large residual doses. The residual dose rises with stimulation time, suggesting that the initial part of IRSL signals contains more easy-to-bleach signals comparing with the later part. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

No description available.

Thesis (Master of Science)--Miami University, Dept. of Geology, 2004. / Title from first page of PDF document. Document formatted into pages; contains [1], v, 76 p. : ill. Includes bibliographical references (p. 42-50).

No description available.