## 5 Conclusions  
1. The target formation in the study area develops a set of terminal fan deposits at the margin of an alluvial fan. Controlled by the long-term rise of the base level, these deposits exhibit a retrogradational stacking pattern. The terminal fan formed in a gentle-slope zone under an arid climate and was controlled by episodic flood events. It is dominated by fine sandstone, with multiple channel bifurcations forming large-scale lobes along their margins. Frequent channel bifurcations and multi-stage evolution led to the lateral amalgamation of lobes in plan view and their vertical stacking over multiple depositional phases.
2. Well log data were used to identify channels, lobes, lobe margins, and interlobe mudstone. By delineating the boundaries and spatial distribution of sedimentary microfacies, an architecture analysis of the X42\(-\)8 sublayer was conducted. The results indicate that long-term to mid-term base-level cycles controlled the advance and retreat of the terminal fan, systematically regulating its scale and distribution pattern. From bottom to top, the deposits transition from laterally extensive thick sand bodies to more dispersed thin lobe deposits. Overall, lobe width and thickness exhibit a linear correlation, with an average ratio of approximately 128.
3. The lobe, classified as an eighth-order architectural element within the sand bodies of the study area, was identified as the key research focus. Four indicators were used to identify its lateral boundaries: sedimentary facies transitions, variations in sand body basal elevation, trends in sand body central thickness, and differences in hydrocarbon content. The contact relationships between single-sand-body lobes at the alluvial fan fringe were categorized into two types: stacked and isolated. Stacked lobes exhibit three subtypes--lateral amalgamation, vertical stacking, and incision--while isolated lobes are classified into laterally separated and vertically isolated types. As the base level changes, the contact patterns of individual sand bodies also vary accordingly.
4. In the study area, channels are small in width and thickness but extend long distances along the transport direction. Channel development involves multiple phases of in situ incision, with limited bifurcation. The combination of channels and lobes is elongated and sinuous, with weak lateral amalgamation and insignificant vertical accretion.
5. A 3D sedimentary architecture model of the alluvial fan fringe derived from the southern provenance has been established. The model is characterized by a main distributary channel system that progressively branches downstream. Along the channel margins, lobes, lobe margins, and interlobe mudstones develop from proximal to distal locations. The channel-lobe assemblages form complex lateral amalgamations in plan view, resulting in extensive sand-body connectivity, while in the vertical dimension, they exhibit offset stacking, creating a complex spatial architecture.  
Figure 7: Sedimentary facies model diagram of the study area.  
**Author Contributions:** Conceptualization, B.Z. and L.W.; methodology, B.Z. and Y.Y.; software, L.W.; validation, B.Z., L.W. and Y.Y.; formal analysis, B.Z. and L.W.; investigation, Y.Y.; resources, Y.Y. and L.W.; data curation, B.Z. and L.W.; writing--original draft preparation, B.Z.; writing--review and editing, B.Z. and Y.Y.; visualization, L.W.; supervision, Y.Y.; project administration, Y.Y. and L.W.; funding acquisition, Y.Y. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** All data and materials are available on request from the corresponding author. The data are not publicly available due to ongoing research using a part of the data.  
**Conflicts of Interest:** The authors declare no conflicts of interest.