## 4 Results
### Drilling Profiles  
#### 4.2.1 Profile A-A\({}^{\prime}\)  
According to lithology, color, material composition and sedimentary structure, 10 stratigraphic layers can be identified from the drilled core columns in profile A-A\({}^{\prime}\) (Figure 4a).  
Figure 3: The time profile of the survey line CX1.  
Layers 1 to 5 are the eolian loess-paleosol strata, whilst layer 6 is fluvial deposition. The details of each layer from top to bottom are described as follows.  
Layer 1 includes backfill, heilu soil and loess. Heilu soil (S0) has uniform soil texture, visible pores and massive structures, and contains calcareous streaks and concretions. The loess layer is labeled as L1, which is the first layer of the eolian loess sequence, with a uniform soil texture, visible pores and a yellow-brown color. The heilu soil and loess only exist in the individual boreholes. The backfill and heilu soil were formed during Holocene, while the loess layer L1 was formed during the Late Pleistocene.  
Layer 2 is the Upper Pleistocene paleool S1 layer, with a reddish-brown color. The soil texture in this layer is uniform with visible pores, presenting massive structures and containing a higher concentration of white calcareous streaks and concretions. This layer is one of the most significant marker layers in the study area, which was also revealed by the foundation pit; details of this layer are described below.  
Figure 4: Stratigraphic lithology of the drilling profile A–A\({}^{\prime}\) (**a**) and profile B–B\({}^{\prime}\) (**b**).  
Layer 3 is the loess layer L2 formed during the Middle Pleistocene. It has a uniform soil texture with visible pores and contains a modicum of concretions and calcareous streaks. The color of this layer is brownish-yellow.  
Layer 4 is the paleosol layer S2 formed during the Middle Pleistocene, with a reddish-brown color. The soil texture in this layer is uniform, with visible pores and massive structures. It contains a higher concentration of white calcareous streaks and concretions.  
Layers 5 and 2 are the loess layers L3 and L4, which show similar features to layer 3. Additionally, layers 6 and 8 are the paleosol layers S3 and S4, and their natures are similar to layer 4.  
Layer 5 is the loess-paleosol sequence underlying the paleosol S4, which was formed during the Early to Middle Pleistocene. Due to the difficulty in correlating the strata in the profile, it is categorized as one major layer. This set of stratigraphy has a uniform soil texture with visible pores and contains white calcareous streaks and concretions. The loess layer has a lighter color, while the paleosol layer has a darker color. Both the loess and paleosol layers exhibit a pattern: the deeper the layer, the smaller the pores and the darker the color.  
Layer 6 consists of silty clay, silt and fine sand. It also has a uniform soil texture with a sticky characteristic, and contains iron oxide-rich silt, as well as a modicum of concretions. The fine sand is uniform in texture, including components like quartz and feldspar. It has a yellow-brown color and was formed during the Early Pleistocene. This layer is distinct from the overlying strata and is characterized by fluvial-lacustrine deposition, which indicates its relatively horizontal layering.