## 4 Results  
### Restoration Results of Graben Denudation in Changling Formation  
Using the stratigraphic trend method, we have successfully reconstructed the denudation volumes for the four main tectonically active phases within the Changling Graben. As illustrated by the denudation volume restoration of the Shahezi Formation in the ChanglingGraben (Figure 9), the denudation characteristics of the strata exhibit a clear pattern. By analyzing the underlying strata, their internal co-phase axes, and the strata's diminishing trend, and integrating these observations with the stratigraphic trend extrapolation method, we have been able to restore the denudation thickness across various strata. This approach not only restores the denudation thickness but also reinforces the theoretical foundation of the stratigraphic trend extrapolation method, which transitions from individual points to lines and ultimately to a comprehensive surface analysis. Through the detailed restoration of the upper surfaces of each eroded stratum within the profile, it has been observed that the primary denudation in the study area occurred within the Huoshiling, Shahezi, and Yingcheng Formations, while the denudation thickness significantly decreased in the Denglouku Formation. By integrating the analysis of tectonic movements and regional context, we have achieved a comprehensive denudation restoration across the entire region, systematically transitioning from point to line and then to surface, thereby achieving a three-dimensional closure. This approach has allowed us to meticulously restore the denudation volumes for the Huoshiling, Shahezi, Yingcheng, and Denglouku Formations with a 16 \(\times\) 16 grid density, as illustrated in Figure 9. Consequently, we have been able to estimate the denudation and the original depositional thickness data for the graben strata with greater precision. (1) Denudation characteristics of Huoshiling Formation  
Seismic profiles clearly reveal the most significant truncation characteristics in the central and northern sectors of the Changling Graben (Figure 10a). The stratigraphic distribution of the Huoshiling Formation is controlled by the boundary faults that define the depression, thereby establishing the fundamental structural framework of the graben basin. In the later stages of sedimentation, the strata experienced uplift due to tectonic  
Figure 9: Denudation calculation of the Shahezi Formation in Changling Graben using the stratigraphic trend extrapolation method. Notes: (**a**) fold denudation type; (**b**) marginal uplift denudation type; (**c**) the location of the typical profile for denudation recovery is shown in (B,B). activities, followed by denudation, resulting in an angular unconformity with the overlying strata. Using the stratigraphic trend extrapolation method, we have determined that the denudation thickness across the Huoshiling Formation ranges from 0 to 450 m, with an average thickness of approximately 125 m. The most substantial denudation thickness is observed near the Shenzijing and Hashituo Troughs within the Changling Graben, with the central trough being the most severely eroded. In contrast, the northern and southern troughs exhibit relatively milder denudation and more intact strata. The residual thickness of the Huoshiling Formation varies from 0 to 1200 m, with the most significant denudation, around 417 m, noted in the Shenzijing-Hashituo region. The denudation intensity is most pronounced in the central region, decreasing from north to south, and the denudation thickness primarily extends in a north-south orientation. (2) Denudation characteristics of Shahezizu Formation  
The denudation of the Shahezi Formation is predominantly evident in the regions of Shenzijing, Hashituo, Chaganhua, Fulongquan Troughs, and Da'an Graben, as depicted in Figure 10b.