Desert-steppe migration on the Loess Plateau at about 450 kaBP

According to the field investigation, observation by an electronic microscope and x-ray identification and chemical analysis, desert-steppe migration in the Loess Plateau at about 450 kaBP was studied. The data show that gypsum illuvial horizon indicating the desert-steppe environment developed in the early stage of the formation of the fifth layer loess in Shaoling tableland in Chang‘an and Bailu tableland in Xran of Shaanxi are situated in the southern Loess Plateau. This indicates that remarkable drying occurred, a large-scope migration of desert steppe took place toward south and the climate zone migrated 5 degrees in latitude to south which is the largest migration range indicated by geochemical indexes. The desert-steppe and more wild environment distributed widely on the Loess Plateau at that time. The development of gypsum also indicates that the climate changed at 450 kaBP from monsoon climate to nonmonsoon climate in the Loess Plateau, and the region was not affected by summer monsoon and was in the cold and dry environment of nonmonsoon climate. Annual mean nrecinitation was about 200 rnm. 400 mm less at that time than at oresent.     

广东干湿气候的特征

提出一种月、季干湿气候指数，并用于广东各地干湿气候的分析，结果表明，广东以４－９月为湿季，１０月到翌年１月为干季，２－３月为干转湿的过渡期，干季短而湿季长，干湿季节的互换呈纬向自北向南推南，３－４月呈北湿南干，９月呈北干南湿，干湿季的转换时间与自然季节的转换基本相符。     

湿润指数与干燥度关系的探讨

为使我国气候区划标准与国际气候区划标准接轨，从其定义出发，将《国际防治荒漠化公约》中采用湿润指数划分气候区与我国传统的干燥度气候区划作比较认为：润润指数气候区划与干燥度气候区划在理论上有相关性。     

山东平邑盆地下第三系钙壳的特征及意义

钙壳(Caliches)是一种粉末状——胶结完好的低镁方解石沉积物,含少量石英粉砂及粘土矿物,通常呈乳白色或淡黄色。钙壳是在陆地表面或渗流带中,经成土作用而成。形成这类沉积物的母岩通常是碳酸盐岩,但其他沉积岩,甚至火成岩和变质岩(Seneniuk and Searle,1985)也可作为钙壳的母岩。钙壳的地质时代分布广,从前寒武纪至今均有报道,但以更新世和全新世的研究较多,而更新世以前的相对较少。本文以山东平邑盆地下第三系官庄组二段中钙壳为例,探讨其岩石学及生物化石特征、沉积环境和地层意义。     

Oasis System and Its Reasonable Development in Sangong River Watershed in North of the Tianshan Mountains, Xinjiang, China

An oasis is a kind of medium-sized or small-sized non-zonal landscape coming into being in the dry climate and supported by natural rivers in deserts, which is characterized by the comparatively high primary pro- ductivity and has the mesophytic plants or xero-mesophytic plants as the dominant vegetation (Jia, 1996). The oasis system, first of all, is a subsystem within the macro system of “mountain-oasis-desert” in the arid region. It is also a complex system where the natural and artificia…