## 1 Introduction  
The Songliao Basin, located in northeastern China, is a continental basin formed during the Mesozoic-Cenozoic era, rich in oil and gas resources. The Changling Graben, the largest fault depression group in the southern part of the Songliao Basin, features a typical double-layer structure of fault depression superposition [1,2]. Significant breakthroughs were made with the deployment of the Changshen 40 and 41 wells in the Changling Graben, revealing the vast resource potential of deep tight gas [3, 4, 5]. Since the Early Cretaceous Huoshiling period, the Changling Graben has undergone multiple phases of complex tectonic movements, greatly altering the basin's landscape. According to the \"prototype controls source\" theory, the development of source rocks is influenced by the basin prototype during their formation period, such as basin type, paleogeomorphological features, and paleo-depositional environments [6]. To further analyze the deep oil and gas exploration potential of the Changling Graben, it is necessary to restore the basin prototype, clarify the tectonic movements the basin has experienced, and define the impact of later tectonic movements on the basin [6, 7, 8, 9, 10]. The uplift and denudation of strata can alter the burial history of the basin, affecting the generation, migration, and preservation conditions of oil and gas [11, 12, 13, 14, 15]. Therefore, reconstructing paleogeomorphology combined with denudation amounts can restore the sedimentary records affected by denudation and depict the basin's appearance during the deposition period. Analyzing the prototype basin by integrating basin structure and its evolution, sedimentary fill characteristics, and paleogeomorphological features can summarize the basin's evolutionary laws, providing important evidence for the tectonic evolution of the Songliao Basin [16, 17, 18].  
Previous studies on the protolithic basin of the Changling Graben have primarily focused on individual graben layers, lacking a systematic restoration of regional denudation amounts across the entire graben [19, 20]. Currently, the study area has achieved full coverage of 3D seismic data, with partial completion of secondary acquisition. Various methods exist for calculating stratigraphic denudation amounts, such as the stratigraphic structural trend extrapolation method, the acoustic well logging method, and the wave equation analysis method. In this study, the collected data include acoustic well logging data and seismic data. However, since the upper part of the strata in the Changling Graben period experienced much greater subsidence than denudation, the well logging data do not conform to the principles of sedimentation and compaction, making it impossible to calculate the denudation amount of the graben period strata using well data [21, 22, 23, 24, 25, 26, 27]. Consequently, the stratigraphic structural trend extrapolation method was selected to restore the denudation volume of the graben period strata from point to line to surface [28]. Based on the denudation volume and the residual strata, the original depositional thickness of the strata was reconstructed. By integrating the basin structure and evolution, sedimentary filling characteristics, and paleotopography, the protolithic basin of different periods was analyzed, and the patterns of subsidence filling and tectonic evolution were summarized. This analysis provides valuable support for the selection of favorable exploration zones.