15万年以来极地冰芯、黄土、深海沉积的对比研究与全球变化          下载免费PDF全文

康建成  温家洪 《极地研究》1997,9(2):55-65

由极地冰芯记录、中纬黄土记录和深海沉积记录的对比可得，１５万年以来全球变化的基本框架为：末次间冰期，从距今１４万年开始到约１２．５万年达鼎盛，可分为五个阶段，即冰芯中三次高温期夹两次低温期；黄土中三层古土壤夹两层黄土；深海沉积中三次高海面夹两次低海面。末次冰期，距今８万年到１万年，可分为三个阶段，早、晚冰段和中间的间冰段。早、晚冰段盛期气候寒冷程度相当，但晚冰段最低温持续期更长，造成海面比早期更低。中间的间冰段，至少可分为７个亚段，即４次暖期（４次弱成土古土壤）夹３次冷期。全新世与末次间冰期对比，总体气候变化较平缓。在上述基本框架中，近几年发现，在末次冰期存在许多短周期、高频快速变化事件。这些事件，温度变化幅度达７℃，变化速率为几年到几十年，对应的环境变化速率可能更快。这些事件的引发机理目前还不清楚，有待进一步研究。  相似文献   

当代国际移民创业研究进展     

杨家蕊  符文颖 《世界地理研究》2020,29(3):480-490

移民创业活动是经济地理学研究中一个重要主题。创业是一种经济活动,但不同群体的创业活动蕴含着不同文化内涵和行为选择。移民创业的研究是解读移民群体社会与文化形成的一个关键的维度。移民群体具有明显的边界,其内部的空间秩序、社会网络、族裔文化以及共同的身份认同都是值得探讨话题,因此学界对移民创业活动给予了持续的关注。移民活动日益频繁,所涉及的行业地域日益扩大,对移民创业群体的研究有利于促进区域经济发展、了解全球政治网络,沟通地理学与社会学和经济学的研究融合,是经济地理学研究中值得关注的问题。本文基于Citespace软件,运用文献分析法,从国际移民创业概念内涵阐述、研究动态、研究前沿及演变、未来研究可能四个方面出发,阐述移民创业研究的历史脉络及进展。研究发现美国和英国在移民创业中占有重要地位。区域创业环境是研究者们主要关注的话题,与创业联系最为紧密的是绩效（0.28）、自雇佣（0.17）和组织（0.17）等关键词研究。全球化趋势不可逆转,跨国主义日趋强盛,未来关于移民及移民创业的研究大有可期。  相似文献   

Characteristics of industrial structure evolution and isomorphism in Central Asia     

Kang  Lei  Liu  Yi 《地理学报(英文版)》2020,30(11):1781-1801

Journal of Geographical Sciences - This study undertakes a systematic examination of characteristics of the spatio-temporal evolution of industrial economies in Central Asia from the perspectives...  相似文献   

哈尔滨黄土的粒度与地球化学特征及其对粉尘物源的指示   总被引：2，自引：1，他引：1  

杜慧荣  谢远云  康春国  迟云平  王嘉新  孙磊 《中国沙漠》2020,40(1):64-76

哈尔滨黄土位于欧亚黄土带的最东端,对它的风尘物源研究是深层次理解风尘堆积与区域构造-地貌-气候变化耦合关系的关键。然而,对哈尔滨黄土地球化学组成的研究尚未开展,对其性质还存在认识上的不统一。为此,我们研究了哈尔滨天恒山剖面L₁黄土层的粒度和地球化学组成,并对其化学风化和物源等展开讨论。为了示踪哈尔滨黄土的物源,我们还对东北沙地（浑善达克沙地、科尔沁沙地、呼伦贝尔沙地和松嫩沙地）进行了表土采样和地球化学分析。结果表明：哈尔滨黄土不含细砂组分（125~250 μm）,含有极细砂组分（63~125 μm,4.8%~10.5%）,粉砂（4~63 μm）和黏土组分（<4 μm）占绝对优势,分别占73%~82%和12%~18%;粒度模式为三峰态分布（众数分别为36~40、8~10 μm和0.8 μm）,与黄土高原典型黄土的粒度分布模式一致,但明显粗于黄土高原中部黄土。哈尔滨黄土经历了初级的化学风化过程,具有较低的成熟度和再循环历史。单靠地球化学方法不能很好地确定哈尔滨黄土的物源,但整合的方法（包括粒度、元素和同位素组成、MDS和PCA统计方法以及自然地理要素等）很好确定了哈尔滨黄土有一个混合源,松嫩沙地松花江水系沉积物为哈尔滨黄土提供了主要的粉尘贡献,浑善达克沙地和科尔沁沙地为哈尔滨黄土提供了部分细颗粒粉尘。  相似文献   

Coal Permeability Evolution Under Different Water-Bearing Conditions     

Li  Jianhua  Li  Bobo  Pan  Zhejun  Wang  Zhihe  Yang  Kang  Ren  Chonghong  Xu  Jiang 《Natural Resources Research》2020,29(4):2451-2465

Natural Resources Research - The seepage problem of coal-bed methane (CBM) has attracted increasing attention from the research and industry communities. Coal permeability, which is a key parameter...  相似文献   

商河油田古近系碎屑岩储层及同沉积断层对其控制作用     

牵尊芝  杨志军  纪友亮  李亚辉  王思文  康云  张竹林 《海洋地质译丛》2010,(3):34-41

商河地区为自北向南成明显阶梯状分布的多级构造调节带及多级坡折带,受其构造特征影响,储层特征也表现出明显的规律性。通过对商河地区大量储层物性数据的统计,结合镜下薄片观察发现商河油田具有同一层位,自北向南,商一区、商二区、商三区、商四区储层物性依次变差的特点;而对于同一地区,整体上自上向下随深度增加储层物性逐渐变差;同一层位不同沉积微相的储层具有不同的物性特征,三角洲前缘河口坝砂体储层物性最好,水下分支河道较好,而远砂坝、席状砂砂体储层物性相对较差。经综合研究分析认为储层特征主要受沉积相及成岩作用共同影响,储层成岩作用主要受地层埋深的影响,而由于商河地区的分界大断层主要为同沉积断层,地层厚度和沉积相分布主要受同生断层活动的影响,因此构造作用的同沉积断层是商河地区储层物性的主要控制因素。  相似文献   

Growth,feeding and ecological roles of the mixotrophic and heterotrophic dinoflagellates in marine planktonic food webs   总被引：4，自引：0，他引：4  

Hae Jin Jeong  Yeong Du Yoo  Jae Seong Kim  Kyeong Ah Seong  Nam Seon Kang  Tae Hoon Kim 《Ocean Science Journal》2010,45(2):65-91

Planktonic mixotrophic and heterotrophic dinoflagellates are ubiquitous protists and often abundant in marine environments. Recently many phototrophic dinoflagellate species have been revealed to be mixotrophic organisms and also it is suggested that most dinoflagellates may be mixotrophic or heterotrophic protists. The mixotrophic and heterotrophic dinoflagellates are able to feed on diverse prey items including bacteria, picoeukaryotes, nanoflagellates, diatoms, other dinoflagellates, heterotrophic protists, and metazoans due to their diverse feeding mechanisms. In turn they are ingested by many kinds of predators. Thus, the roles of the dinoflagellates in marine planktonic food webs are very diverse. The present paper reviewed the kind of prey which mixotrophic and heterotrophic dinoflagellates are able to feed on, feeding mechanisms, growth and ingestion rates of dinoflagellates, grazing impact by dinoflagellate predators on natural prey populations, predators on dinoflagellates, and red tides dominated by dinoflagellates. Based on this information, we suggested a new marine planktonic food web focusing on mixotrophic and heterotrophic dinoflagellates and provided an insight on the roles of dinoflagellates in the food web.  相似文献   

Latitudinal distribution of mesozooplankton in the off-equatorial northeastern Pacific before and after the 1998/99 La Niña event     

Kang JH  Kim WS  Chang KI 《Marine environmental research》2008,65(3):218-234

Factors affecting mesozooplankton distributions in the northeastern tropical Pacific Ocean were investigated using data obtained along a meridian line (5 degrees -12 degrees N, 131.5 degrees W) in the summers of 1998, 1999, and 2003. The survey periods corresponded to a sharp transition between the 1997-1998 El Ni?o and 1998-1999 La Ni?a events, the 1999 La Ni?a event, and near-normal conditions after the moderate 2002-2003 El Ni?o in the equatorial Pacific. A strong upwelling in the divergence zone from 10.5 degrees to 11 degrees N caused a shoaling of the thermocline depth (approximately 30 m), resulting in increases in nitrate and phytoplankton chlorophyll a (chl-a) concentrations, and, in turn, mesozooplankton abundance during the La Ni?a in 1999. In contrast, in 1998, remnants of El Ni?o characteristics, deeper thermocline depth (60-150 m) and warm surface water (>28 degrees C), led to low concentrations of nitrate, chl-a and low mesozooplankton abundance, except in the convergence zone around 7 degrees N. The thermocline depth and nitrate concentration obtained during the near-normal period in 2003 corresponded to intermediate values as compared to those obtained during El Ni?o and La Ni?a conditions. Interannual changes in the position and strength of ecotones, such as divergence and convergence zones, affected mesozooplankton community structure and cyclopoid-to-calanoid ratios along the 131.5 degrees W meridian line. The clustering pattern of the mesozooplankton community was mostly characterized by calanoid (mainly Clausocalanus sp.) and cyclopoid (mainly Oncaea sp.) copepods, accounting for most of the observed differences among groups during the study period. Cyclopoids and calanoids were more abundant in 1999 than in 1998 or 2003, with a sharp increase to the north, while they were less abundant to the north in 1998 and 2003. The cyclopoid-to-calanoid ratio peaked in the convergence zone in 1998 and the divergence zones in 1999 and 2003, apparently due to the strength and location of the ecotones. Principal component analysis (PCA) with environmental factors and dominant mesozooplankton groups showed that dominant groups were affected by nitrate and chl-a concentrations in 1998, by sigma-t (water density), nitrate and chl-a concentrations in 1999, and by sigma-t, salinity and chl-a concentration (except siphonophores) in 2003. Latitudinal distribution of thermocline depth before and after the 1998/99 La Ni?a event showed a distinct interannual difference. The abundance of mesozooplankton in the divergence zone in 1999 was distinctively higher than abundances found in the convergence and divergence zones in 1998 and 2003, which resulted from the shallow thermocline depth due to an intensified upwelling during the strong 1998-1999 La Ni?a event.  相似文献   

水沙环境中重金属迁移转化模型的两个解析解   总被引：2，自引：0，他引：2  

袁德奎  郑康  聂红涛 《海洋技术学报》2008,27(3)

选取整体模型,将水体中的溶解态(水相)和吸附态(固相)重金属作为整体,开展了水沙环境中重金属迁移转化数学模型的解析解研究.在一定的简化条件下,得出了泥沙单纯沉积和单纯侵蚀两种特定动床条件下一维重金属迁移转化模型的两个解析解.文中成果可用于数学模型的验证和完善.  相似文献   

川东石炭系地层—构造复合圈闭控制因素及有利区研究     

康保平  张箭  张志勇  彭光明  廖开贵 《海洋地质译丛》2008,(2):40-45

根据川东石炭系实钻资料,结合前人资料对石炭系地层—构造复合圈闭进行了分类和总结;在此基础上,对川东石炭系地层—构造复合圈闭的控制因素进行了研究。研究表明沉积相是地层—构造复合圈闭的次要控制因素,而古岩溶、古构造是其主要控制因素;在此过程中,根据黄龙纽残余厚度分布状况提供的岩溶剥蚀强度信息、经压实恢复上覆梁山组碳质泥岩等厚度图反映的黄龙组顶面侵蚀地形变化印模及由岩溶相组合特征所显示的古水文条件,恢复了川东地区黄龙组古岩溶地貌。在分析古岩溶地貌单元古水文状况、溶蚀方式和强度、古构造及古岩溶厚度的基础上,对川东内古岩溶进行了区块划分。最后综合了各种资料,对川东石炭系地层—构造复合圈闭有利区带进行了预测。  相似文献