更新世黄土高原强烈侵蚀期发生的环境条件

在更新世,黄土高原经历了若干堆积-侵蚀旋回。其中黄土堆积主要发生在冷干期,而强烈土壤侵蚀发生的环境条件至今尚无统一认识,其确定对了解黄土高原地貌的演化过程和更新世侵蚀期的求得均具有重要意义。通过对比黄土高原侵蚀模数分布图与新构造运动分区图,得出侵蚀模数高值区与构造抬升强烈区并不吻合,推断黄土高原侵蚀期发生的主要原因不是构造抬升。在野外考察中,寻找了多个侵蚀面,并与邻近较为完整的黄土-古土壤剖面进行比照,发现侵蚀面主要存在于黄土层上部,其上覆的古土壤层一般保存完整,说明土壤侵蚀主要发生在黄土层,即气候由冷干向暖湿的过渡时期。这一结论为求取黄土高原第四纪侵蚀期提供了理论依据。

Environmental Conditions of Intensive Erosion Periods on Loess Plateau During Pleistocene

During the Pleistocene, the Loess Plateau had experienced a number of accumulation - erosion cycles. Accumulation mainly occurs in the cool -dry periods; however, there is no uniform understanding on environmental conditions in which intensive soil erosion occurred. The determination of the latter is of great significance for the understanding of the landform evolution during Pleistocene of the Loess Plateau and to obtain erosion periods. By comparing the modulus distribution map and Neotectonits division map on the Loess Plateau, it is found that the area where bears high erosion modulus do not consistent with the area where experiencing strong tectonic uplift, which could be inferred that Neotectonics is not the main reason of intensive soil erosion on the Loess Plateau. After field survey, a number of erosion surfaces and some relatively complete loess - paleosol sequences nearby were found, erosion surfaces mainly on the upper part of loess layer, while the paleosol layer above keeps intact, indicating soil erosion mainly occurred to the loess layer. The environmental condition is climate transition period from cool - dry to warm - wet. This conclusion delivered theoretical basis for obtaining erosion periods during the Quaternary on the Loess Plateau.