渭南黄土台塬晚新生代环境与城市建设

根据对W7、W8两钻孔中的孢粉、微体古生物化石和矿物成分分析,结合野外考察及古地磁地层年代资料与标准剖面对比,作者提出本区第四纪地层划分的初步意见并阐述了晚新生代环境.根据W7、W8两孔相当层位的深度变化,推断张性正断层的存在,进而讨论了与城市建设有关的地下水资源和黄土塌陷问题.

RESEARCH OF QUATERNARY DEPOSITIONAL ENVIRONMENT ON THE LOESS-PLATEAU OF THE WEINAN OF SHANXI PROVINCE AND IN REFERENCE TO ITS URBAN CONSTRUCTIONAL SIGNIFICANCE

Both the W8 and W7 drilling cores in the Weinan area, with 52 to 92 layers in all can be divided into two parts.the upper one is stratum alternating several fossil soil layers; the lower stratum is a set of layers consisting alternately of sand, gravel, clay and silty clay of the river or lake facies.With stratigraphic correlation and comprehensive comparison between the W8 and W7 drilling cores, they have quite similar characters in the stratigraphy and paleontology, such as the features of strata, sporo-pollen and microfossils.But the difference between the altitudes above sea of the well-matched layers in both the W8 and W7 holes can be well over 100m.Consequently, the layers of different ages have been contacted at the same altitude in the holes while the same layers have been fractured.The fracture extends from the stratum of the later age of the Middle Pleistocene down through the stratum of the Neogene system at the bottoms of the holes perhaps into the bedrock.According to those mentioned above,the authors identify that the characteristics of the fracture belong to tensile normal fault, rataer then the result of exogenic force.The underground water-bearing beds in the loess-plateau area and its surrounding areas have been cut off from each other by the structural fault.Therefore, with the decreasing of the rainfall and the rapid increasing of the extraction of the groundwater, the problems of the environmental geology.including the widespread and big descending of the groundwater level, the worsening of the water quality and the occurring of the man-made funnels of the groundwater, have been presented in the loess-plateau area.If the groundwater is extracted continuously and indiscriminately, ground sinking may occur in a large number in the loess-plateau area.The tremendous losses caused by the sinking will be difficult to estimate.For this reason, the authors suggest that the effective measures to exploit and to rationally use new sources of water and to stop extracting the groundwater at the loess-plateau should be taken immediately in order to protect the groundwater resource in this area.