中更新世转型时期南海北部上层水体结构演化特征——ODP1146站浮游有孔虫稳定同位素记录     

王海粟  党皓文  翦知湣 《第四纪研究》2019,39(2):316-327

文章以南海北部ODP1146站沉积物岩芯为研究材料,利用浮游有孔虫次表层水种Pulleniatina obliquiloculata壳体的氧、碳稳定同位素,结合该站位浮游及底栖有孔虫氧碳同位素数据,分析中更新世以来南海北部上层水体结构的演化。1.2 Ma以来ODP1146站P.obliquiloculata壳体δ^18O的变化可分3个阶段:1)1.2~0.9 Ma,冰期-间冰期变化幅度较小、主导周期为41 ka斜率周期;2)0.9~0.6 Ma,冰期旋回变化幅度逐渐增强、100 ka偏心率周期开始强化;3)0.6 Ma以来,冰期旋回呈现稳定且幅度较大的100 ka周期变化。0.9 Ma以来南海北部上层海水δ^18O的冰期旋回变幅增强,可能反映东亚冬季风在0.9 Ma之后显著强化。其中,表层水体δ^18O只在冰期变幅增强,P.obliquiloculata所反映的次表层水体δ^18O的变化幅度在冰期和间冰期都显著增强。约0.9 Ma浮游和底栖有孔虫δ^18O的100 ka周期几乎同时显现;但在0.9~0.6 Ma时期P.obliquiloculata的δ^18O偏心率周期更为显著、斜率周期的强度也更高。因此,冰期旋回周期转型及幅度变化两方面的证据共同反映温跃层结构演化在南海北部中更新世转型(MPT)气候转变过程中的特殊性。1.2 Ma以来ODP1146站P.obliquiloculata的δ^13C在0.02 Ma、0.49 Ma和0.99 Ma左右呈明显的碳重值,同时表层种-次表层种之间的δ^13C差值减小到近于0,可以解读为碳重值事件期间南海北部生产力相对减弱。  相似文献   

Integrated Geological–Geophysical and Oceanographic Research in the South China Sea: Cruise 88 of the R/V “Akademik M.A. Lavrentyev”     

Shakirov  R. B.  Cuong  Do Huy  Obzhirov  A. I.  Valitov  M. G.  Lee  N. S.  Legkodimov  A. A.  Kalgin  V. Yu.  Yeskova  A. I.  Proshkina  Z. N.  Telegin  Yu. A.  Storozhenko  A. V.  Ivanov  M. V.  Pletnev  S. P.  Sedin  V. T.  Bulanov  A.V.  Shvalov  D. A.  Lipinskaya  N. A.  Bovsun  M. A.  Makseev  D. S.  Thanh  Nguyen Trung  Anh  Le Duc  Luong  Le Duc 《Oceanology》2021,61(1):147-149

Oceanology - Abstract—The paper gives brief results of comprehensive studies in the South China Sea obtained from a joint Russian–Vietnamese expedition in November 2019 (cruise 88 of...  相似文献   

Geology ‘far from the madding crowd’, along the northern border of Vietnam     

Mark Williams  Toshifumi Komatsu  Phong Nguyen Duc  Tom Harvey  Thijs Vandenbroucke 《Geology Today》2019,35(6):217-220

To the north of Hanoi, about a day's drive by car, lies Ha Giang Province, the northernmost region of Vietnam. Ha Giang is remote from the hustle and bustle of daily life, and beyond its eponymous provincial capital towards the border with China, mountains rise quickly to Quan Ba, ‘Heaven's Gate’. The mountains form an uneven landscape of steep‐sided karst rising from deep river‐cut gorges and form a formidable barrier on the northern frontier of Vietnam. Beyond ‘Heaven's Gate’ lies the little travelled region of Dong Van, with its majestic mountains of Palaeozoic strata rising precipitously to the sky. Here, a century ago, the French geologists Henri Mansuy and Jacques Deprat documented early finds of fossils from lower Palaeozoic strata on the border with China.  相似文献   

New urban map of Eurasia using MODIS and multi-source geospatial data     

Bayan Alsaaideh  Ryutaro Tateishi  Dong Xuan Phong  Nguyen Thanh Hoan  Ahmad Al-Hanbali  Bai Xiulian 《地球空间信息科学学报》2017,20(1):29-38

Urban areas are of paramount significance to both the individuals and communities at local and regional scales. However, the rapid growth of urban areas exerts effects on climate, biodiversity, hydrology, and natural ecosystems worldwide. Therefore, regular and up-to-date information related to urban extent is necessary to monitor the impacts of urban areas at local, regional, and potentially global scales. This study presents a new urban map of Eurasia at 500 m resolution using multi-source geospatial data, including Moderate Resolution Imaging Spectroradiometer (MODIS) data of 2013, population density of 2012, the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) nighttime lights of 2012, and constructed Impervious Surface Area (ISA) data of 2010. The Eurasian urban map was created using the threshold method for these data, combined with references of fine resolution Landsat and Google Earth imagery. The resultant map was compared with nine global urban maps and was validated using random sampling method. Results of the accuracy assessment showed high overall accuracy of the new urban map of 94%. This urban map is one product of the 20 land cover classes of the next version of Global Land Cover by National Mapping Organizations.  相似文献   

生物基可降解聚乳酸(PLA)沙障对沙丘表层沉积物粒度特征的影响   总被引：4，自引：0，他引：4  

丁延龙  高永  汪季  孙晓瑞  党晓宏  韩彦隆  李鹏 《中国沙漠》2018,38(2):262-269

以吉兰泰盐湖北部流沙区铺设8 a的不同规格聚乳酸（PLA）沙障内沉积物为研究对象,利用激光衍射技术分析了沙丘表层0~3 cm沉积物粒度组成,计算并分析平均粒径、标准偏差等粒度参数,探讨了影响障内沉积物相对粗细的关键组分,分析PLA沙障的防沙效益。结果表明：PLA沙障内沉积物以细沙、中沙、极细沙为主。中沙、极细沙、细沙是障内沉积物的关键组分。PLA沙障的阻滞作用使得中沙、粗沙含量百分比升高,细颗粒含量百分比降低,障内沙粒分选性逐渐变差,峰态偏离正态分布,向负偏方向发展,频率分布曲线分布范围变宽,累积频率曲线变缓,表层颗粒组成趋于粗化。1 m×1 m规格PLA沙障内均以积沙为主;沙丘迎风坡和背风坡的2 m×2 m、3 m×3 m沙障内均为积沙状态,丘顶则为风蚀状态。综合考虑沙障铺设成本和防护效果,得出研究区域内2 m×2 m规格PLA沙障整体防沙效益最佳。  相似文献   

A distinction between summer rainy season and summer monsoon season over the Central Highlands of Vietnam     

Ngo-Thanh  Huong  Ngo-Duc  Thanh  Nguyen-Hong  Hanh  Baker  Peter  Phan-Van  Tan 《Theoretical and Applied Climatology》2018,132(3-4):1237-1246

Theoretical and Applied Climatology - The daily rainfall data at 13 stations over the Central Highlands (CH) Vietnam were collected for the period 1981–2014. Two different sets of criteria...  相似文献   

夯扩挤密水泥土桩复合地基的应用研究   总被引：4，自引：0，他引：4  

邓才雄  何俊光 《岩土工程技术》1999,(1):53-57

根据水泥土和夯扩挤密施工法的特点,结合工程实例,对夯扩挤密水泥土桩在地基处理设计与施工进行了一些探讨和研究,阐明了利用夯扩挤密水泥土桩进行地基处理是安全可行、经济合理的一种型式,以及设计与施工中应注意的几个问题,并在高层住宅中进行了尝试,取得了较好的效果。  相似文献   

Carbon pools and fluxes in the China Seas and adjacent oceans     

Nianzhi Jiao  Yantao Liang  Yongyu Zhang  Jihua Liu  Yao Zhang  Rui Zhang  Meixun Zhao  Minhan Dai  Weidong Zhai  Kunshan Gao  Jinming Song  Dongliang Yuan  Chao Li  Guanghui Lin  Xiaoping Huang  Hongqiang Yan  Limin Hu  Zenghu Zhang  Long Wang  Chunjie Cao  Yawei Luo  Tingwei Luo  Nannan Wang  Hongyue Dang  Dongxiao Wang  Si Zhang 《中国科学:地球科学(英文版)》2018,61(11):1535-1563

The China Seas include the South China Sea, East China Sea, Yellow Sea, and Bohai Sea. Located off the Northwestern Pacific margin, covering 4700000 km~2 from tropical to northern temperate zones, and including a variety of continental margins/basins and depths, the China Seas provide typical cases for carbon budget studies. The South China Sea being a deep basin and part of the Western Pacific Warm Pool is characterized by oceanic features; the East China Sea with a wide continental shelf, enormous terrestrial discharges and open margins to the West Pacific, is featured by strong cross-shelf materials transport; the Yellow Sea is featured by the confluence of cold and warm waters; and the Bohai Sea is a shallow semiclosed gulf with strong impacts of human activities. Three large rivers, the Yangtze River, Yellow River, and Pearl River, flow into the East China Sea, the Bohai Sea, and the South China Sea, respectively. The Kuroshio Current at the outer margin of the Chinese continental shelf is one of the two major western boundary currents of the world oceans and its strength and position directly affect the regional climate of China. These characteristics make the China Seas a typical case of marginal seas to study carbon storage and fluxes. This paper systematically analyzes the literature data on the carbon pools and fluxes of the Bohai Sea,Yellow Sea, East China Sea, and South China Sea, including different interfaces(land-sea, sea-air, sediment-water, and marginal sea-open ocean) and different ecosystems(mangroves, wetland, seagrass beds, macroalgae mariculture, coral reefs, euphotic zones, and water column). Among the four seas, the Bohai Sea and South China Sea are acting as CO_2 sources, releasing about0.22 and 13.86–33.60 Tg C yr~(-1) into the atmosphere, respectively, whereas the Yellow Sea and East China Sea are acting as carbon sinks, absorbing about 1.15 and 6.92–23.30 Tg C yr~(-1) of atmospheric CO_2, respectively. Overall, if only the CO_2 exchange at the sea-air interface is considered, the Chinese marginal seas appear to be a source of atmospheric CO_2, with a net release of 6.01–9.33 Tg C yr~(-1), mainly from the inputs of rivers and adjacent oceans. The riverine dissolved inorganic carbon (DIC) input into the Bohai Sea and Yellow Sea, East China Sea, and South China Sea are 5.04, 14.60, and 40.14 Tg C yr~(-1),respectively. The DIC input from adjacent oceans is as high as 144.81 Tg C yr~(-1), significantly exceeding the carbon released from the seas to the atmosphere. In terms of output, the depositional fluxes of organic carbon in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea are 2.00, 3.60, 7.40, and 5.92 Tg C yr~(-1), respectively. The fluxes of organic carbon from the East China Sea and South China Sea to the adjacent oceans are 15.25–36.70 and 43.93 Tg C yr~(-1), respectively. The annual carbon storage of mangroves, wetlands, and seagrass in Chinese coastal waters is 0.36–1.75 Tg C yr~(-1), with a dissolved organic carbon(DOC) output from seagrass beds of up to 0.59 Tg C yr~(-1). Removable organic carbon flux by Chinese macroalgae mariculture account for 0.68 Tg C yr~(-1) and the associated POC depositional and DOC releasing fluxes are 0.14 and 0.82 Tg C yr~(-1), respectively. Thus, in total, the annual output of organic carbon, which is mainly DOC, in the China Seas is 81.72–104.56 Tg C yr~(-1). The DOC efflux from the East China Sea to the adjacent oceans is 15.00–35.00 Tg C yr~(-1). The DOC efflux from the South China Sea is 31.39 Tg C yr~(-1). Although the marginal China Seas seem to be a source of atmospheric CO_2 based on the CO_2 flux at the sea-air interface, the combined effects of the riverine input in the area, oceanic input, depositional export,and microbial carbon pump(DOC conversion and output) indicate that the China Seas represent an important carbon storage area.  相似文献   

Thermo-hydro-mechanical modeling of unsaturated soils using isogeometric analysis: Model development and application to strain localization simulation     

Shahriar Shahrokhabadi  Toan Duc Cao  Farshid Vahedifard 《国际地质力学数值与分析法杂志》2020,44(2):261-292

This study presents a thermo-hydro-mechanical (THM) model of unsaturated soils using isogeometric analysis (IGA). The framework employs Bézier extraction to connect IGA to the conventional finite element analysis (FEA), featuring the current study as one of the first attempts to develop an IGA-FEA framework for solving THM problems in unsaturated soils. IGA offers higher levels of interelement continuity making it an attractive method for solving highly nonlinear problems. The governing equations of linear momentum, mass, and energy balance are coupled based on the averaging procedure within the hybrid mixture theory. The Drucker-Prager yield surface is used to limit the modified effective stress where the model follows small strain, quasi-static loading conditions. Temperature dependency of the surface tension is implemented in the soil-water retention curve. Nonuniform rational B-splines (NURBS) basis functions are used in the standard Galerkin method and weak formulations of the balance equations. Displacement, capillary pressure, gas pressure, and temperature are four independent quantities that are approximated by NURBS in spatial discretization. The framework is used to simulate strain localization in an undrained dense sand subjected to plane strain biaxial compression under different temperatures and displacement velocities. Results show that an increase in the displacement rate leads to reduction in the equivalent plastic strain while an increase in the temperature leads to an increase in the equivalent plastic strain. The findings suggest that the proposed IGA-based framework offers a viable alternative for solving THM problems in unsaturated soils.  相似文献   

西秦岭甘南地区上二叠统毛毛隆组古环境演变:基于遗迹网络分析          下载免费PDF全文

党志英  张立军 《古地理学报》2020,22(6):1171-1180

西秦岭地区是二叠系—三叠系之交深水相保存较为连续的地区,西秦岭甘南地区上二叠统毛毛隆组发育丰富的遗迹化石(12属17种)。遗迹网络分析作为新兴的研究方法,侧重于用相互连接的遗迹分类群来重建遗迹群落系统,这为研究遗迹群落的行为学和生态学提供了丰富的手段。笔者以西秦岭甘南地区上二叠统毛毛隆组发现的遗迹化石为数据源,运用遗迹网络分析方法,揭示出毛毛隆组遗迹群落具结构化特征,遗迹群落体现出环境驱动的遗迹组合面貌特征: Palaeophycus-Lockeia-Arenicolites-Dictyodora-Planolites-Protovirgularia-Chondrites组合(C1,近源浊流区),Palaeophycus-Lockeia-Arenicolites-Dictyodora-Protovirgularia-Phycodes-Chondrites-Helminthopsis组合(C2,浊流过渡区—浊流远源区),和Palaeophycus-Nereites-Scolicia-Protovirgularia-Helminthopsis组合(C3,远源浊流区)。该遗迹群落由C1演变至C3的过程,揭示了古环境从近源浊流区至远源浊流区的演变历程。  相似文献