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一组古藏纸的现代技术分析
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作者 时嘉瞳 葛梦帆 +3 位作者 韩宾 陈相龙 杨益民 施继龙 《复旦学报(自然科学版)》 CAS CSCD 北大核心 2024年第5期586-597,共12页
藏纸是我国具有区域特色的手工纸,对古代藏纸开展科技分析,将推动古藏纸的价值认知,为研究古藏纸的工艺演变、文化交流提供重要信息。本研究通过显微分析、热裂解-气相色谱质谱联用的方法,获取一组古藏纸的纤维、填料、施胶剂、墨迹成... 藏纸是我国具有区域特色的手工纸,对古代藏纸开展科技分析,将推动古藏纸的价值认知,为研究古藏纸的工艺演变、文化交流提供重要信息。本研究通过显微分析、热裂解-气相色谱质谱联用的方法,获取一组古藏纸的纤维、填料、施胶剂、墨迹成分等信息。实验结果表明:此组藏纸采用了瑞香狼毒(Stllera chamaejasme)、白瑞香和桑皮作为造纸纤维;经过了添加填料等处理工艺;纸样上的金色文字是由铜汁书写,银色文字是由银汁书写;3张藏纸上涂的墨汁均是松烟墨制成的。通过此案例研究表明应用综合科技分析方法对古藏纸进行全面分析,有助于更好地了解各个时期古藏纸特性,助益古代造纸技术的研究及纸质文物的保护。 展开更多
关键词 古藏 Py-GC/MS 瑞香狼毒 桑皮
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古籍书目数据库中繁简字的使用
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作者 阎瑞君 陈军 《图书与情报》 CSSCI 北大核心 2003年第3期36-38,共3页
利用计算机技术建立古籍书目数据库 ,必须重视繁简字的使用问题。繁简字的处理是亟待解决的问题之一。本文主要探讨了数据库中繁简字的使用 ,以及建立书目数据库需要考虑的几个方面。
关键词 古藏 书目数据库 繁体字 简化字
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Temporal-Spatial Distribution of Vegetation in the Qinghai-Xizang Plateau During the Past 12 ka BP 被引量:7
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作者 唐领余 《Acta Botanica Sinica》 CSCD 2002年第7期872-877,共6页
Comprehensive studies on the basis of pollen records from lake cores at 30 sites in the Qinghai-Xizang Plateau have been used to reconstruct temporal-spatial distributions of Holocene vegetations. Before the, Holocene... Comprehensive studies on the basis of pollen records from lake cores at 30 sites in the Qinghai-Xizang Plateau have been used to reconstruct temporal-spatial distributions of Holocene vegetations. Before the, Holocene (prior to 12.0 ka BP) desert steppe vegetation was developed from the, east to the west in the most parts of the Plateau, with a few exceptions in the extreme southeastern appeared. During the early Holocene ( 12.0 - 9.0 ka BP) deciduous broad-leaved forest/conifer and broad-leaved deciduous mixed forest were distributed in the east of Plateau (104degrees - 98degrees E). Meadows or shrub, meadow appeared in the middle of tire Plateau (98degrees - 92degrees E). Farther west to about 80degrees E, a steppe landscape was present. During the middle Holocene (9.0 - 3.2 ka BP), the palaeovegetations were sequentially conifer and broad-leaved deciduous mixed forest and sclerophyllous broad-leaved forest (104degrees - 98degrees E) - conifer and broad-leaved deciduous mixed forest (98degrees - 94degrees E) - shrub meadow (94degrees - 92degrees E) - steppe (92degrees - 80degrees E). During the late Holocene (after 3.2 ka BP), the palaeovegetations were sequentially sclerophyllous broad-leaved forest - conifer and broad-leaved deciduous mixed forest - meadow - steppe - desert from east to west of the Plateau. 展开更多
关键词 PALAEOVEGETATION HOLOCENE Qinghai-Xizang Plateau pollen records
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Combustion Properties of Textiles Applied in Tibet Ancient Buildings and Their Clean Flame Retarding Designs 被引量:2
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作者 尤飞 胡源 时虎 《Journal of Donghua University(English Edition)》 EI CAS 2006年第5期135-140,共6页
In the Tibet ancient buildings, there are large amounts of combustible decorative textiles that pose great potential fire hazards. Some typical textile samples were collected from the Potala Palace. Their combustion p... In the Tibet ancient buildings, there are large amounts of combustible decorative textiles that pose great potential fire hazards. Some typical textile samples were collected from the Potala Palace. Their combustion properties were analyzed by UL 94 Vertical Burning test and Limiting Oxygen Index test. The effects of plateau climate on combustion properties, an important fact required to be considered in the flame retarding design for combustible textiles, were preliminarily compared via test data in the plain and those in the plateau. Based on the foregoing analyses, some thoughts were presented on the clean and feasible flame retarding means for the decorative textiles due to their special applications in Tibet, in ancient buildings and in plateau climate. The fire resistance, weather resistance, UV resistance, endurance, ornamentation and religious performances for these textiles must be taken into considerations comprehensively in the designs. 展开更多
关键词 textile TIBET ancient building combustion property flame retarding design.
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High-altitude gastrointestinal bleeding:An observation in Qinghai-Tibetan railroad construction workers on Mountain Tanggula 被引量:28
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作者 Tian-Yi Wu Shou-Quan Ding +6 位作者 Jin-Liang Liu Jian-Hou Jia Rui-Chen Dai Dong-Chun Zhu Bao-Zhu Liang De-Tang Qi Yong-Fu Sun 《World Journal of Gastroenterology》 SCIE CAS CSCD 2007年第5期774-780,共7页
AIM: To investigate the gastrointestinal bleeding (GIB) in people from lowland to high altitude and in workers on Mountain Tanggula and its causes as well as treatment and prophylaxis.METHODS: From 2001 to October 200... AIM: To investigate the gastrointestinal bleeding (GIB) in people from lowland to high altitude and in workers on Mountain Tanggula and its causes as well as treatment and prophylaxis.METHODS: From 2001 to October 2003, we studied GIB in 13 502 workers constructing the railroad on Mountain Tanggula which is 4905 m above the sea level. The incidence of GIB in workers at different altitudes was recorded. Endoscopy was performed when the workers evacuated to Golmud (2808 m) and Xining (2261 m). The available data on altitude GIB were analyzed.RESULTS: The overall incidence of GIB was 0.49% in 13 502 workers. The incidence increased with increasing altitude. The onset of symptoms in most patients was within three weeks after arrival at high altitude. Bleeding manifested as hematemesis, melaena or hematochezia, and might be occult. Endoscopic examination showed that the causes of altitude GIB included hemorrhage gastritis, gastric ulcer, duodenal ulcer, and gastric erosion. Experimental studies suggested that acute gastric mucosal lesion (AGML) could be induced by hypoxic and cold stress, which might be the pathogenesis of altitude GIB. Those who consumed large amount of alcohol, aspirin or dexamethasone were at a higher risk of developing GIB. Persons who previously suffered from peptic ulcer or high-altitude polycythemia were also at risk of developing GIB. Early diagnosis, evacuation, and treatment led to early recovery. CONCLUSION: GIB is a potentially life threatening disease, if it is not treated promptly and effectively. Early diagnosis, treatment and evacuation lead to an early recovery. Death due to altitude GIB can be avoided if early symptoms and signs are recognized. 展开更多
关键词 High altitude Gastrointestinal bleeding Hypoxic stress Acute gastric mucosal lesion Risk factors
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Active Tectonics and Erosional Unloading at the Eastern Margin of the Tibetan Plateau 被引量:34
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作者 Alexander L. Densmore LI Yong +1 位作者 Michael A. Ellis ZHOU Rongjun 《Journal of Mountain Science》 SCIE CSCD 2005年第2期146-154,共9页
The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography,coupled with abundant Mesozoic thrusts within the margin,explains why tectonic maps of... The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography,coupled with abundant Mesozoic thrusts within the margin,explains why tectonic maps of the India-Asia collision typically show the eastern margin as a major thrust zone. Actually,it does not like that. Field observations suggest that the margin is better characterized as a zone of NNE-directed dextral shear with extensive strike-slip faulting and secondary thrusting. The high relief and steep gradients are partially explained by erosional unloading of an elastic lithosphere;the pre-erosion inherited topography may be the inherited Mesozoic thrust belt landscape modified by a component of Cenozoic tectonic shortening. 展开更多
关键词 Tibetan Plateau TECTONIC erosional unloading FAULTING
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FIRST AMMONITE AND INOCERAMID DATA FROM THE UPPER CRETACEOUS OF THE TINGRI SECTION IN SE-TIBET:BIOSTRATIGRAPHICAL AND PALAEOENVIRONMENTAL IMPLICATIONS
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作者 Jens LEHMANN Ines WENDLER +2 位作者 Jens WENDLER Helmut WILLEMS Xiumian HU 《地学前缘》 EI CAS CSCD 北大核心 2005年第2期105-112,共8页
A section in the Zhepure Mountains near Old Tingri in SE-Tibet,ranging from the Upper Albian to Paleogene,was described in detail by Willems et al.(1996).These authors worked on the litho-and microfacies and set up th... A section in the Zhepure Mountains near Old Tingri in SE-Tibet,ranging from the Upper Albian to Paleogene,was described in detail by Willems et al.(1996).These authors worked on the litho-and microfacies and set up the biostratigraphical framework by planktonic foraminifera.Willems et al.(1996)established their section as a standard for southern Tibet and compared it to the Gamba area.During the 2004 Tibet-expedition of Chengdu University of Technology in China,in co-operation with Bremen and Kiel universities in Germany,the locality was revisited for the purpose of collecting invertebrate fossils.This field-work included only the Upper Cretaceous part of the Tingri section and its invertebrate faunal content.Until today almost no ammonite and inoceramid data existed for this section.This is true for most Cretaceous sections in Tibet,although the Upper Cretaceous succession was interpreted as shelf environment.which in other parts of the world contains rich faunas of these macrofossil groups.The newly discovered continuous record of rare ammonites and inoceramids is probably limited since the preservation in the wacke-and packstones is poor.In addition,sampling conditions were unfavorable and the environmental conditions disadvantageous for most groups of invertebrates,as possibly indicated by larger amounts of small bivalve debris(filaments)in the upper part of the Gamba Group.Although the collected fauna is sparse and poorly preserved,the following biostratigraphical data can be added to the hitherto described microfauna:Calycoceras?from the Upper Gamba Group is Late Cenomanian in age and is accompanied by indeterminable juvenile desmoceratids.Superjacent follows a record of the ammonite Forresteria sp.,indicating that this level in the upper part of the Gamba Group belongs to the Lower Coniacian.This supports the finding of Inoceramus(Cremnoceramus)waltersdorfensis?hannovrensis?from the same interval.Anagaudryceras?is an individual ammonite finding from the Zhepure Shanbei or Zhepure Shanpo Formation,corresponding to the Santonian-Maastrichtian part of the succession. 展开更多
关键词 ammonite inoceramid Upper Cretaceous BIOSTRATIGRAPHY PALAEOENVIRONMENT Tingri MAASTRICHTIAN TIBET
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Study on Holocene Paleoearthquakes in Xizhang Trench on the Jiaocheng Fault Zone,Shanxi Province
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作者 Xie Xinsheng Zhao Jinquan +8 位作者 Jiang Wali An Weiping Li Zihong Zhang Dawei Cheng Xinyuan Gao Shuyi Wang Chunhe Sun Changbin Yan Chengguo 《Earthquake Research in China》 2008年第4期428-439,共12页
Xizhang trench is located 10 km northwest of Taiyuan city, Shanxi Province, in front of a NNW-trending scarp of 4.6m height on the northern segment of the Jiaocheng fault zone. The dimensions of the trench are 108m in... Xizhang trench is located 10 km northwest of Taiyuan city, Shanxi Province, in front of a NNW-trending scarp of 4.6m height on the northern segment of the Jiaocheng fault zone. The dimensions of the trench are 108m in length, 8m in width, and 10m in depth. There are 18 horizons revealed in the trench. The upper strata are sandy loam; the upper strata of the downthrown block of the fault are gravels, the lower ones are an interbed of brown loam and sandy loam. The strata on the upthrown block of the fault are sandy loam containing gravel. The trench shows 3 fault planes, and the upper offset point on the fault plane is 1.5m below the ground surface, the newest dislocated stratum is (3.74±0.06) ka BP. The trench reveals a lot of deformation traces, such as fault planes, dislocated strata, colluvial wedges and formation tilting. The relationship between strata and faults in the trench shows that 3 paleoearthquake events have occurred at the Jiaocheng fault zone since the Early Holocene, they are about (3.74±0.06)- (3.06±0.26)ka BP, (8.35±0.09)ka- (3.74±0.06)ka BP, and( 10.66±0.85) - (8.35±0.09)ka BP. The average interval among the events is 2.6 - 3.6ka. The minimum coseismic vertical displacements of the 3 events are 3.0m, 2.5m and 3.2m, respectively. The significance of Xizhang trench is that the Jiaocheng fault used to be active thousands of years ago, though there is no M ≥ 7.0 earthquake recorded in historical documents. Evidence of new Jiaocheng fault zone activity during the Holocene is important for the earthquake safety assessment of Taiynan city in the future. 展开更多
关键词 PALEOEARTHQUAKE HOLOCENE Xizhang trench Jiaocheng fault SHANXI
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Influence of Air Pollution on the Deterioration of Monuments and Museum Collections
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作者 Raed Alghazawi 《Journal of Environmental Science and Engineering(A)》 2015年第7期329-335,共7页
The time has come to recognize the extreme importance of the archaeological sites in Jordan. They provide a wealth evidence and precise information regarding ancient civilizations and cultures. The safeguarding of thi... The time has come to recognize the extreme importance of the archaeological sites in Jordan. They provide a wealth evidence and precise information regarding ancient civilizations and cultures. The safeguarding of this cultural heritage is one of the most urgent priorities, that involve the proper conservation and preservation methods of all artifacts and buildings that have an important artistic and historic value. Conservation is a whole field in regarding the care and treatment of valuable artifacts, both movable and immovable. It has two aspects: (1) the control of the environment--to minimize the decay of artifacts and materials and (2) the treatment of these--in order to stop or slow down any deterioration and to stabilize them where possible against further dilapidation. The museum environment is a limited space dedicated not only to exhibition but also to the appropriate conservation of works of art. This article presents an overview of the types of damage and deterioration that air pollution causes to indoor cultural heritage materials and monuments. It identifies the main damaging air pollutants from outdoor sources to be sulphur dioxide, nitrogen dioxide, ozone and sulphide gases. 展开更多
关键词 Air pollution cultural heritage DETERIORATION museum.
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Dynamic Crowd Loading Test on Tibetan Ancient Structures
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作者 Na Yang Ting Guo 《Journal of Civil Engineering and Architecture》 2010年第5期15-21,共7页
The field test of a typical Tibetan ancient structure instrumented with displacement and acceleration transducers was conducted to measure time histories due to crowd walking and running. The test case is introduced f... The field test of a typical Tibetan ancient structure instrumented with displacement and acceleration transducers was conducted to measure time histories due to crowd walking and running. The test case is introduced firstly. The displacement time histories are then used to analyze the dynamic property such as fundamental frequency of vertical vibration and damping ratio of the test structure, and the acceleration time histories are applied to evaluate the floor vibration serviceability. The floor interaction and comparison of human walking and running are also discussed. Some valuable conclusions are given. 展开更多
关键词 Tibetan ancient structure field test dynamic property crowd walking and running floor vibration serviceability.
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Comparative analyses of leaf anatomy of dicotyledonous species in Tibetan and Inner Mongolian grasslands 被引量:13
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作者 MA JianJing JI ChengJun +5 位作者 HAN Mei ZHANG TingFang YAN XueDong HU Dong ZENG Hui HE JinSheng 《Science China(Life Sciences)》 SCIE CAS 2012年第1期68-79,共12页
Knowledge of the leaf anatomy of grassland plants is crucial for understanding how these plants adapt to the environment. Tibetan alpine grasslands and Inner Mongolian temperate grasslands are two major grassland type... Knowledge of the leaf anatomy of grassland plants is crucial for understanding how these plants adapt to the environment. Tibetan alpine grasslands and Inner Mongolian temperate grasslands are two major grassland types in northern China. Tibetan alpine grasslands occur in high-altitude regions where the low temperatures limit plant growth. Inner Mongolian temperate grasslands are found in arid regions where moisture is the limiting factor. Few comparative studies concerning the leaf anatomy of grassland plants of the Tibetan Plateau and Inner Mongolian Plateau have been conducted. We examined leaf characteristics at 71 sites and among 65 species, across the alpine grasslands of the Tibetan Plateau and the temperate grasslands of the Inner Mongolian Plateau. We compared the leaf structures of plants with different life forms and taxonomies, and their adaptation to arid or cold environments. We explored relationships among leaf features and the effects of climatic factors (i.e., growing season temperature and precipitation) on leaf characteristics. Our results showed that (i) there were significant differences in leaf anatomy between Tibetan alpine and Inner Mongolian temperate grasslands. Except for mesophyll cell density, the values obtained for thickness of leaf tissue, surface area and volume of mesophyll cells were larger on the Tibetan Plateau than on the Inner Mongolian Plateau. (ii) Within the same family or genus, leaf anatomy showed significant differences between two regions, and trends were consistent with those of whole species. (iii) Leaf anatomy of woody and herbaceous plants also showed significant differences between the regions. Except for mesophyll cell density, the values obtained for the thickness of leaf tissue, and the surface area and volume of mesophyll cells were larger in herbaceous than in woody plants. (iv) Leaf anatomical traits changed accordingly. Total leaf thickness, thicknesses of lower and upper epidermal cells, and surface area and volume of mesophyll cells were positively correlated, while mesophyll cell density was negatively associated with those traits. (v) Growing season temperature had stronger effects on leaf anatomy than growing season precipitation. Although the communities in Tibetan and Inner Mongolian grasslands were similar in appearance, leaf anatomy differed; this was probably due to the combined effects of evolutionary adaptation of plants to environment and environmental stress induced by climatic factors. 展开更多
关键词 Tibetan Plateau Inner Mongolian Plateau STEPPE MEADOW leaf anatomy dicotyledons
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Lower limits of evaluation parameters for the lower Paleozoic Longmaxi shale gas in southern Sichuan Province 被引量:21
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作者 LI YanJun LIU Huan +3 位作者 ZHANG LieHui LU ZongGang LI QiRong HUANG YongBin 《Science China Earth Sciences》 SCIE EI CAS 2013年第5期710-717,共8页
Here we present six key parameters that have been applied to evaluate the Silurian Longmaxi shale gas accumulations of southern Sichuan Province.These parameters include richness of organic matter,single layer shale t... Here we present six key parameters that have been applied to evaluate the Silurian Longmaxi shale gas accumulations of southern Sichuan Province.These parameters include richness of organic matter,single layer shale thickness,burial depth of the shale,maturity,shale properties,and brittle mineral content.In combination with drilling data,the lower limits of these six parameters for marine shale gas have been evaluated and the following conclusions are drawn:(1)Organic carbon recovery, gas content inversion,and production tests have been applied for the first time to measure the lower limit of TOC,which is determined to be 1.0%.(2)Based on the hydrocarbon generation and expulsion theory for source rocks and the characteristics of Longmaxi shale,the lower limit of the single-layer thickness is estimated to be 30 m,of which a thickness of at least 15 m should contain high-quality shale.(3)Based on the correlation of TOC and porosity,the lower limit of gas-filled porosity is 1.2%.(4)Other parameters,such as maturity,burial depth,and brittle mineral content have also been studied with regard to the geologic conditions of southern Sichuan.Based on the study results,an evaluation index system has been established for highly evolved marine shale gas,and the system has been applied successfully to geologically screened shale gas occurrences in southern Sichuan Province. 展开更多
关键词 shale gas lower limit evaluation system Longmaxi Formation southern Sichuan Province
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Holocene climate change in the Central Tibetan Plateau inferred by lacustrine sediment geochemical records 被引量:16
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作者 Andreas LüCKE Bernd WüNNEMANN 《Science China Earth Sciences》 SCIE EI CAS 2007年第10期1548-1555,共8页
Multi-proxies of lacustrine sediments, such as total carbon (TC), total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), total sulfur (TS), hydrogen index (HI), oxygen index (OI) and stable car... Multi-proxies of lacustrine sediments, such as total carbon (TC), total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), total sulfur (TS), hydrogen index (HI), oxygen index (OI) and stable carbon isotopic composition of organic matter (δ^(13)C_(org)), were analyzed using a 7.3 m core from Zige Tangco. The source of the organic matter in the sediment was mainly from autochthonous phyto-plankton, therefore the significances of proxies can be interpreted as that high TOC, TOC/TS, HI and δ^(13)C_(org) values, low TC, TIC values corresponded to warm and wet climatic condition, and vice versa. The process of climatic development in the Zige Tangco region was hence recovered. During the early and Mid-Holocene, the climate was warm and wet and intensive cold events occurred during the periods of 8600 to 8400 cal a BP and 7400 to 7000 cal a BP. In the second half of Holocene, the climate became cold and dry gradually. The palaeoclimatic process during Holocene in Zige Tangco region matched well with that in Co Ngoin region which is ca 40 km to the south-east. Therefore this palaeoclimatic process represents the Holocene climatic feature in the Central Tibetan Plateau which has the same pattern in the Northern Tibetan Plateau, but the time and duration of some climatic events might be different. We can conclude that in Holocene solar insolation controlled the climatic pattern on the central Tibetan Plateau. 展开更多
关键词 lacustrine sediment hydrogen index (HI) stable carbon isotopic composition (δ^(13)C_(org)) PALAEOCLIMATE Central Tibetan Plateau
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A 12-kyr record of microbial branched and isoprenoid tetraether index in Lake Qinghai,northeastern Qinghai-Tibet Plateau:Implications for paleoclimate reconstruction 被引量:6
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作者 WANG HuanYe DONG HaiLiang +2 位作者 ZHANG ChuanLun JIANG HongChen LIU WeiGuo 《Science China Earth Sciences》 SCIE EI CAS CSCD 2016年第5期951-960,共10页
Branched and Isoprenoid Tetraether(BIT) index was considered as a proxy for terrestrial organic matter input in lake sediments, based on the assumption that branched glycerol dialkyl glycerol tetraethers(b GDGTs) are ... Branched and Isoprenoid Tetraether(BIT) index was considered as a proxy for terrestrial organic matter input in lake sediments, based on the assumption that branched glycerol dialkyl glycerol tetraethers(b GDGTs) are mainly derived from terrestrial soils. However, mounting evidences have showed that the in situ production of b GDGTs is widespread in lakes, challenging BIT as a reliable terrestrial input proxy. Recently, BIT has been proven to be a reliable proxy for paleohydrology in a small crater lake(Lake Challa) in accordance with a different mechanism. However, the response of BIT to paleohydrology variation may differ for different lakes. In this study, we investigate the variations in the BIT index and the concentrations of its related GDGTs in a 12-ka sediment core from Lake Qinghai, in combination with our previous results for surface sediments. We find that variations in BIT strongly depend on the concentration of crenarchaeol in both surface and ancient sediments of this lake, whereas b GDGT concentration varies much less remarkably. Considering that crenarchaeol production is positively correlated with water depth in Lake Qinghai, water depth may exert negative control on the BIT index in this lake. This case is inconsistent with the positive relationship between BIT and lake levels or rainfall intensity reported for Lake Challa, suggesting that the response of BIT to local paleohydrology is site specific in lacustrine systems. Hence, the application of sedimentary BIT as a paleohydrological proxy in a specific lake requires caution before confirming the environmental controls on BIT in that lake. 展开更多
关键词 Lake Qinghai BIT lake water depth precipitation paleohydrology
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Paleomagnetic results of Late Paleozoic rocks from northern Qiangtang Block in Qinghai-Tibet Plateau, China 被引量:10
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作者 CHENG Xin WU HanNing +10 位作者 GUO Qiang HOU BaoNing XIA LingYan WANG HaiJun DIAO ZongBao HUO FeiFei JI WenHua LI RongShe CHEN ShouJian ZHAO ZhenMing LIU XiaoJi 《Science China Earth Sciences》 SCIE EI CAS 2012年第1期67-75,共9页
Tectonic evolution of the Tethys and the boundary between the Gondwanaland and the Eurasia during the Carboniferous and Permian remain hotly debated. Qiangtang region in the Qinghai-Tibet Plateau may be a key place to... Tectonic evolution of the Tethys and the boundary between the Gondwanaland and the Eurasia during the Carboniferous and Permian remain hotly debated. Qiangtang region in the Qinghai-Tibet Plateau may be a key place to study these problems. A paleomagnetic study was conducted on the Late Paleozoic rocks in the northern Qiangtang region (33.7°N, 86.7°W), Tibet. Two sites (21 samples) in the Upper Carboniferous, eleven sites (101 samples) in the Permian, and two sites (16 samples) in the Lower Triassic were investigated. The rock magnetic data revealed hematite and magnetite as the main magnetic carders. In stepwise thermal demagnetization and/or combined alternating field (AC) demagnetization, two characteristic components in the majority of the samples were identified as (1) the Low-temperature Component (LTC), characterized by northerly decli- nation and moderate to steep inclination, corresponding to a pole position overlay with the present North Pole. A minority of the samples present single component, and their directions are the same as (2) the High-temperature Component (HTC) of double components. The combined single-component and HTC data of the Permian can pass the R-test at 95% level and the F-test at 99% level, as well as the BC-test. The pole position from the Late Carboniferous is at 31.8°S, 45.7°E with dp=2.1, dm=3.9, that from the Early and Middle (Late) Permian is at 31.7°S, 46.8°E with @=9.2, dm=16.9 (34.4°N, 54.1°E with dp=6.9, dm=1 2.5) respectively, and that from the Early Triassic is at 16.9°S, 22.5°E with dp=4.9, dm=9.2. These pole positions are different from the other poles for the Qiangtang Block, which suggests the single-component and HTC directions are probably a primary magnetization and the northern Qiangtang Block was paleogeographically situated at low latitudes in the Northern Hemisphere in the Late Paleozoic. 展开更多
关键词 PALEOMAGNETISM TETHYS Northern Qiangtang Block Late Paleozoic
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Altitudinal effect of soil n-alkane δD values on the eastern Tibetan Plateau and their increasing isotopic fractionation with altitude 被引量:2
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作者 BAI Yan CHEN ChiHao +2 位作者 FANG XiaoMin LIU XiaoMing GUO HaiChao 《Science China Earth Sciences》 SCIE EI CAS CSCD 2017年第9期1664-1673,共10页
Stable isotope paleoaltimetry has provided unprecedented insights into the topographic histories of many of the world's highest mountain ranges. However, on the Tibetan Plateau(TP), stable isotopes from paleosols ... Stable isotope paleoaltimetry has provided unprecedented insights into the topographic histories of many of the world's highest mountain ranges. However, on the Tibetan Plateau(TP), stable isotopes from paleosols generally yield much higher paleoaltitudes than those based on fossils. It is therefore essential when attempting to interpret accurately this region's paleoaltitudes that the empirical calibrations of local stable isotopes and the relations between them are established. Additionally,it is vital that careful estimations be made when estimate how different isotopes sourced from different areas may have been influenced by different controls. We present here 29 hydrogen isotopic values for leaf wax-derived n-alkanes(i.e., δD_(wax) values,and abundance-weighted average δD values of C_(29) and C_(31)) in surface soils, as well as the δD values of soil water(δD_(sw)) samples(totaling 22) from Mount Longmen(LM), on the eastern TP(altitude ~0.8–4.0 km above sea level(asl), a region climatically affected by the East Asian Monsoon(EAM). We compared our results with published data from Mount Gongga(GG). In addition,47 river water samples, 55 spring water samples, and the daily and monthly summer precipitation records(from May to October,2015) from two precipitation observation stations were collected along the GG transect for δD analysis. LM soil δD_(wax) values showed regional differences and responded strongly to altitude, varying from.160‰ to.219‰, with an altitudinal lapse rate(ALR) of.18‰ km^(-1)(R^2=0.83; p<0.0001; n=29). These δD_(wax) values appeared more enriched than those from the GG transect by ~40‰. We found that both the climate and moisture sources led to the differences observed in soil δD_(wax) values between the LM and GG transects. We found that, as a general rule, ε_(wax/rw), ε_(wax/p) and εwax/sw values(i.e., the isotopic fractionation of δD_(wax) corresponding to δD_(rw), δD_p and δD_(sw)) increased with increasing altitude along both the LM and GG transects(up to 34‰ and 50‰, respectively). Basing its research on a comparative study of δD_(wax), δD_p, δD_(rw)(δD_(springw)) and δD_(sw), this paper discusses the effects of moisture recycling, glacier-fed meltwater, relative humidity(RH), evapotranspiration(ET), vegetation cover, latitude,topography and/or other factors on ε_(wax/p) values. Clearly, if ε_(wax-p) values at higher altitudes are calculated using smaller ε_(wax-p) values from lower altitudes, the calculated paleowaterδD_p values are going to be more depleted than the actual δD values, and any paleoaltitude would therefore be overestimated. 展开更多
关键词 Hydrogen isotope values for leaf wax-derived n-alkanes Aparent fractionation factor Surface water evaporation Local water vapor recycling Paleoaltitudinal reconstruction Eastern Tibetan Plateau
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