Formation mechanism of ferromagnetic minerals in loess of China： TEM investigation

The results of TEM investigation indicate that magnetite and maghemite are the major ferromagnetic minerals in loess-paleosol sequences. Primary magnetite has the similar morphology and surface characteristics as eolian detrital particles. The magnetite can be classified into two categories, high-titaninm and low-titanium, which may be the indicators of magmatic rocks and metamorphic rocks,respectively. TEM investigation at nanometer scale shows that primary detrital magnetite of micron scale had been partially weathered to magnetite of 5-20 nanometer during the pedogenic process, which maintain the pseudomorphism of the aeolian debris. Some chlorite particles were also weathered to nanometer scale magnetite or maghemite in the pedogenic process. So weathering of the two minerals leads to formation of superparamagnetism, which may be the important mechanism of magnelic-susceptibnlty increase in paleosols. The mgnelite or maghhemite resulting from the weathering of chlorite contains a small amount of P and S,which is the signal of microbe-mineral interaction, and indicates that microbes may play a certain role in chlorite weathering and formation of Superparamagnetic particles.     

郑州—洛阳黄河南岸黄土地层及更新世环境分析

重点介绍了河南豫西地区洛阳－郑州间黄河南岸邙岭的两个黄土剖面,并进行了岩石和磁性地层划分对比,证实了该区黄土最早形成于早更新世晚期的第九层粉砂层（Ｌ９）。在此基础上对黄河的发育及区域更新世环境变迁进行了初步分析。     

Forcing mechanisms for East-Asia monsoonal variations during the late pleistocene

Based on the climate records derived from loess deposits in north-central China, the characteristics of the East-Asia paleomonsoonal changes during the Late Pleistocene are summarized as follows: (ⅰ) The 0.1_Ma climate period is predominant in both summer and winter monsoonal changes over East Asia; (ⅱ) The East-Asia monsoonal variation is different from the Indian monsoon during the Late Pleistocene; (ⅲ) There is a ～5_ka time lag of the East-Asia monsoon changes relative to the theoretically calculated solar radiation changes; (ⅳ) There is a general trend toward increase in winter monsoon and decrease in summer monsoon in the last glaciation; (ⅴ) In the East-Asia monsoonal region, the amplitude of glacial-to-interglacial cycles shows a remarkable increase from south to north. To explain these characteristics, a conceptual model is developed and the forcing of global ice volume variations in the monsoonal history is emphasized.     

Magnetic characteristics and their paleoclimatic significance of Fengzhou loess in the Qinling Mountains of China

The Fengzhou loess section is very typical in the Qinling Mountains. The section, about 82 m thick and underlain by the Neogene red clay, consists of 33 layers of loess and 33 layers of paleosol. The section covers Brunnes normal polarity zone and Matuyama reversed polarity zone, and the B/M boundary is located in the middle of L₈. Matuyama reversed polarity zone records Jaramillo, Olduvai and Reunion normal polarity subchrons. The boundary between Matuyama reversed polarity zone and Gauss normal polarity zone (M/Ga) appears in the lithological boundary between loess and the Neogene red clay. Loess accumulation in Fengzhou started before 2.48 Ma. The magnetic susceptibility curve indicates 33 cold-dry and humid-warm cycles of paleoclimatic variation in the Qinling Mountains during the last 2.48 Ma. The above climatic fluctuation may be well compared with that of the oxygen isotopic records from deep-sea deposits.     

预浸水法在湿陷性黄土地基中的应用

调查分析了新疆伊犁地区湿陷性黄土的工程力学性质,介绍了预浸水法在处理自重湿陷性黄土地基中的应用情况,说明这种方法可以消除黄土地基的自重湿陷性,提高地基的承载力。     

黄土高原半干旱区农田土壤水分动态及其调控——以甘肃为例

由甘肃黄土高原的榆中站、定西站和西峰站的实测（１９８９～１９９２年）农田土壤湿度的对比分析得出，黄土高原半干旱区农田土壤水分的变化规律是：在一年内有春季严重失墒期，夏秋增墒期，秋冬缓慢失墒期和冬季稳墒期等４个时期；在０～２００ｃｍ的土壤剖面内，按其供水性能可分为速变层、活跃层和相对稳定层．并提出了集水蓄墒的具体调控措施     

论黄土高原沟壑区沟坡土地资源的开发

黄土高原沟壑区沟坡面积广大，水土流失严重，土地的生产力很低．随着人、地、粮予盾的不断尖锐，开发沟坡土地资源的生产潜力已势在必行．黄土高原沟壑区沟被土地资源只要因地制宜，综合开发，有可能获得较塬面土地更高的经济效益．本文通过分析黄土高原沟壑区沟坡土地资源的有利条件及开发意义，提出了黄土高原沟壑区沟坡土地资源的开发模式及开发的具体途径与措施．     

可缩多面体是绝对收缩核

在文献［１］（ＰｒｏｃＡｍｅｒ．Ｍａｔｈ．Ｓｏｃ．１９８３，８８：３３３～３３７）中我们证明了每一个可折叠多面体均可内射度量化。借助于这一结果，本文证明了每一个可缩多面体均是个绝对收缩核。     

石油开发对黄土区生态环境的影响与对策

目的 为降低石油开发引起的区域生态破坏和环境污染的影响程度，分析石油开发各阶段对生态因子的影响，并提出保护对策。方法 对土地利用、动植物、植被和景观生态因子采用资料收集和实地调查方法，土壤生态因子采用类比工程监测和USLE模型预测方法。结果 通过分析得出石油开发的建设期、运行期和服务期满后3个阶段均对黄土丘陵沟壑区的土地利用、土壤、动植物、植被和景观产生影响。结论 根据不同阶段和工程类型的影响程度，采取相应的保护对策，尤其是生物措施要贯穿整个开发过程，把石油开发对黄土丘陵沟壑区生态环境的影响程度降低到最小。