关中平原500～10ka BP黄土地层岩溶作用研究

Karst Processes in Loess Strata Between 500 and 10 ka in the Guanzhong Plain

根据关中平原黄土地层岩溶作用产物的研究,可将该区500～10ka BP黄土地层岩溶作用分为北亚热带侵蚀-溶蚀型、湿暖湿润带强溶蚀-侵蚀型、温冷半湿润带中溶蚀-侵蚀型和温冷半干旱带弱溶蚀-侵蚀型4种。根据古土壤发育时岩溶作用垂向分带遗迹,可将前人划分的渗流带进一步分为上部非饱和循环强溶蚀亚带、中部过饱和循环沉淀亚带和下部不稳定循环弱溶蚀-弱沉淀亚带。3个亚带的划分对确定CO_2在垂向上的循环有重要指示意义。该区500～10ka BP可分为10个岩溶发育阶段,构成5个岩溶旋回,发展趋势是由强变弱。

On the basis of a study of the karst processes in loess strata in the Guanzhong Plain, the karst processes between 500 and 10 ka in the area can be subdivided into the erosion-dissolution type of the north subtropics, strong dissolution-erosion type in the south humid temperate zone, mediun dissolution-erosion type in the north semi-humid temperate zone and weak dissolution-erosion type in the north semi-arid temperate zone. According to the karst remains in the vertical zoning section during the development of paleosols, the vadose zone defined by predecessors can be subdivided into three subzones, namely, the upper strong dissolution subzone with unsaturat-ed water solution, the middle precipitation subzone with supersaturated water solution and lower weak dissolution or weak precipitation subzone with unstable water solution. The subdivision of the vadose zone is of very important significance for determining the CO2 vertical circulation. Ten karst stages constituting 5 karst cycles occurring between 500 and 10 ka in the area can be determined and the developmental trend of karst processes was from strong to weak in the period.