大同盆地晚新生代环境演化特征

大同盆地是一受北东向主干断裂控制的不对称地堑盆地。盆地基底形态控制了晚新生代沉积的厚度、结构和分布规律。大同盆地古湖泊在上新世早期即已存在,并被盆地中部呈北东走向的玄武岩垅岗分隔成南北两部分;由于构造运动和古气候变化的影响,早更新世早期湖泊发育达到全盛期,然后几经扩张与收缩,于晚更新世早期逐惭消亡。河流与湖泊的相互消长在盆地内沉积了一套河湖相地层,其物质来源主要是东北部火山岩和变质岩分布区。

The Characteristics of Environmental Evolution in Late-Cenozoic of the Datong Basin

The Datong Basin is an unsymmetrical graben, the main controlling fault of which runs north east. By means of bore-hole cores, heavy minerals, geochemical elements, sporo-pollen association and animal fossils, this paper discusses the characteristics of structure and the evolution of sedimentary environment in Late-Cenozoic of the Datong Basin. The author point out that the shape of the base ment controls the thickness and the distribution of the Late-Cenozoic deposits. The ancient Datong lake had been shaped at the beginning of the early Pliocene and was subdivided into two parts by the basaltic ridge. It was developed largely in the early Pleistocene. At the late Pleistocene, the ancient Datong lake was gradually vanished. The neotectonic movement was the main cause of the lake evolution, although climatic changes were the other reasons. The great thickness deposits of Late-Cenozoic in Datong Basin were mainly combinated with the deposits of lake facies and alluvial fan facies. They mainly came from the northeast part of the basin. A model of the paleoenvironmental evolution in the Datong Basin during late Cenozoic is established.