THE RECORD OF YOUNGER DRYAS EVENT IN EOLIAN SAND DEPOSIT IN QAIDAM BASIN

The Qaidam Basin is one of the main areas where the desert of the Qinghai-Xizang Plateau is distributed.According to the envirotunment records and the age of stratigraphy in Xiaxitai section in southeast part of Qaidam Basin,this paper reached the following conclusions: the desert development, formation of the cold-dry climate, evolution of natural environment and their reverse changes occurred frequently since the late glacial. In eolian sand deposits, the YoungerDryas event clearly appeared, which manifesed a dry-cold climatic period. Now there are two different opinions about theclimatic effect of Younger Dryas. According to the predecessors’ research and the field work of the authors, it is considered that the Younger Dryas event not only exists in different climatic zones of China, but the manifests the unitary drycold climatic effect.

Eolian sand deposition and its environmental significance in the northeastern margin of the Qinghai-Xizang Plateau

The dry climate which appeared about 8-7 Ma ago in South Asia has been interpreted as results of the intensification of Asian monsoon caused by the uplift of the Qinghai-Xizang Plateau at its maximum altitude around that time. Whether it is or not, it is a critical problem. A total of 55 samples were taken from the Tertiary red earth and Quaternary lacustrine deposits and loess in the Linxia Basin which is located in the northeastern margin of the

柴达木盆地沙漠沉积中的新仙女木事件记录

对柴达木盆地晚更新世沙漠演化过程的研究，发现青藏高原沙漠沉积中清楚地记录了新仙女木事件，并呈于冷降温的气候效应。进一步分析得出：新仙女木事件在我国不同自然气候带呈单一的干冷降温效应，并作为多模式效应。

临夏盆地晚中新世以来的风沙沉积及环境意义

对临夏盆地 １５ Ｍａ以来地层中的石英砂所作的扫描电镜分析表明，风成砂一直存在，并在 ８ Ｍａ和 ６～５ Ｍａ时含量最高。最大颗粒的平均粒径在（１．５～３．６）／２．６ Ｍａ达 ０．４ｍｍ，３．６～２．６Ｍａ之后显著下降。前者表明 ３．６～２．６ Ｍａ以前，近源风沙作用一直存在，并在８Ｍａ和 ６～５Ｍａ达到最盛；后者表明第四纪以来，远源风沙沉积盛行，可能反映了青藏高原在 ３．６～２．６Ｍａ急剧隆起和与之相关的大气环流的改变。

粤东及琼东北第四纪老红砂风成的若干证据

粤东及琼东北第四纪老红砂分布于全新世和现代海岸风沙强烈作用带，其野外产状、沉积构造与海滩砂不同，粒度、石英砂磨圆度、石英砂表面微结构统计、孢粉和硅藻等分析证明这些老红砂与海岸沙丘砂有着成因上的联系，热释光年代为距今1．62—5．19万a，故它们是毗邻海滩的海岸风成砂，形成于未次冰期的低海平面期，其形成和分布与盛行风和向岸风的共同作用有关。

风成砂覆盖区地电化学提取前后土壤中元素赋存状态变化研究

在洛恪顿铅锌多金属矿5勘探线地电化学勘查剖面上采集了电提取前后的土壤样品,开展了全量及顺序提取"七步法"分析测试,对比结果表明:地电化学过程所提取的元素是以多种相态存在于土壤介质中的,以水溶态、离子交换态、碳酸盐结合态等活性相态为主,同时颗粒较小的弱活性相态,甚至残渣态颗粒也可被电化学过程所迁移、吸附;电提取后,土壤中多数元素某一种或几种相对活性相态含量与矿体产生了极好的空间对应关系;较浅的运积物覆盖层及深部有矿体或矿化体存在,可导致电提取后土壤中多数微量金属元素全量显著增加,这表明地电化学方法在运积物覆盖区具有较大的勘查适用性。

强夯法消除风积粉细砂湿陷性研究

沙漠地区的风积粉细砂具有轻微至严重的湿陷性,消除该类地基土的湿陷性是工程学术界亟待解决的问题。结合工程实例,采用强夯法加固风积粉细砂地基土,通过浅层平板载荷试验及室内土工试验检测加固情况,评价强夯法消除风积粉细砂地基湿陷性的效果及规律。结果表明,风积粉细砂的湿陷性主要受含水率及密实度的影响,含水率对于湿陷变形作用尤其突出;强夯施工前,应对场地洒水充足,使土体含水率达到最优含水率;强夯加固中,填方区最佳锤击数为10击,挖方区最佳锤击数为8击,坚持动态化设计信息化施工;强夯后,风积粉细砂的承载力是强夯前的两倍,在湿陷试验中风积粉细砂变形增量随时间变化较少;强夯法改善风积粉细砂湿陷性效果显著,其中,洒水是控制湿陷性的主要因素,强夯是次要因素。研究结果有助于为强夯法处理风积粉细砂地基的设计、施工提供参考,为同类型地基处理提供借鉴。