## 6 Conclusions and Suggestions  
1. Based on geological data such as well logs and core observations, the sedimentary microfacies types of the shallow-water delta front were identified. These can be subdivided into five microfacies: subaqueous distributary channels, estuary dams, estuary dam margins, sheet sands, and interdistributary bays. Using the electrical response characteristics of the rocks, logging facies identification templates and corresponding interpretation criteria were established for each microfacies.
2. Based on single-well and profile facies analyses, the planar distribution characteristics of the shallow-water delta front and the sedimentary evolution of the Daqingzijing area were systematically delineated. The Qing 1 Member exhibits a transitional characteristic from the delta front to the pro-delta to the deep lacustrine. The spatio-temporal distribution characteristics in the study area are as follows: the provenance from the southwest is mainly the delta front, and as it migrates northeastward, vertically, it begins to transition into the pro-delta and deep lacustrine facies with the advance of a large lake area. With the continuous rise in the lake level, the development scale of the sand body decreases. And it shows a pattern of reduced channel development vertically, thinner sandstone layers, the gradual contraction of delta front sand bodies planarly, and the establishment of a sedimentary model of shallow-water delta.
3. The shallow-water delta retrogradational reservoirs are dominated by channel sand bodies and estuary dam sand bodies. The estuary dam sand bodies are relatively well-developed and distributed on both sides of the channels, and they exhibit notable characteristics of vertical stacking, lateral connectivity, and continuous development in the sedimentary sequence. This finding challenges the traditional understanding that river mouth sand bodies develop only at the bifurcation points of distributary channels. It lays a foundation for future reservoir development in the Daqingzijing  
Figure 12: A retrogradational shallow-water delta deposition model of the Qing 1 Member in the Daqingzijing area.  
area and offers new insights into the exploitation of similar sedimentary features in shallow-water delta systems.
* Several factors were not fully considered in this study, including sample chronology, interpretational uncertainty, and potential alternative facies models. It is recommended that future research incorporates additional constraints, such as the integration of 3D seismic data, expansion of the coring grid, and application of provenance geochemistry.  
Scientific literature collection and data analysis, H.W., W.X., and C.W.; writing and revision, H.W., W.X., C.W., S.Q., and C.Y. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Joint Guidance Project of the Natural Science Foundation of Heilongjiang Province grant number [LH2024D010] And The APC was funded by LH2024D010].  
Not applicable.  
The original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding authors.  
We thank all graduate research assistants who helped with data collection.  
The authors declare no conflicts of interest.