摘要
黄土的显微结构特征是黄土粉尘物质堆积之后在特定气候条件和特定自然地理环境中形成的。我国黄土高原晚更新世黄土的显微结构特征反映出晚更新世黄土形成时西北部干旱而东南比较湿润的气候状况,与现今高原区的气候环境区域性变化相一致。根据黄土的显微结构特征,并考虑到黄土的主要化学成分以及磁化强度,黄土高原区晚更新世黄土自西北而东南可以划分为呈逐渐过渡关系的弱风化成土黄土、中等风化成土黄土、较显著风化成土黄土和显著风化成土黄土,它们分别是在干旱、半干旱、半干旱—半显润和半湿润的气候环境中形成的。
The microfabrics of loess were formed under specific climatic conditions and physico-geographical environments after deposition of the dust materials, which for this reason are of important significance in reconstructing the paleoclimatic environment during the formation of loess in the locality in question at that time. In the Loess Plateau of China, the microfabric characteristics (e. g., the forms and arrangement of skeleton grains, kinds and manner of occurrence of cementing materials, manner of occurrence of calcium carbonates, cementation degree and microfabric types) of the late Pleistocene loess show obvious regional variations from northwest to southeast. Againast a general background of a relatively arid paleoclimate reflected by the microfabrics during the formation of the late Pleistocene loess, the climate changed gradually from arid in the northwest to a bit humid in the southeast, which is conformable with the regional variations of the present climate of the Loess Plateau.According to the micromorphology of loess as well as the main chemical composition and the intensity of magnetization, the late Pleistocene loess in the Loess Plateau can be classified into four types from northwest to southeast: 1) loess formed by weak weathering, 2) loess formed by intermediate weathering, 3) loess formed by relatively obvious weathering, and 4) loess formed by obvious weathering. These types are gradational. Their corresponding climatic conditions may be respectively arid, semiarid, semiarid-semihumid, and semihumid.
出处
《地质论评》
CAS
CSCD
北大核心
1989年第4期333-341,共9页
Geological Review
基金
国家自然科学基金
