## 6 Conclusions  
Based on the analysis of the sequence stratigraphic superposition patterns, seismic reflection structures, paleoclimate changes, and tectonic activities, the study area was divided into three sequence types: elastic sequence, saline lake sequence, and volcanic-clastic sequence. According to the different drilling data and seismic reflection characteristics, two second-order sequence interfaces and one third-order sequence interface in the fourth member of the Shahejie Formation were identified in the volcanic-evaporite-clastic symbiotic zone and divided into one second-order sequence, two third-order sequences, and six system tracts. According to the different findings of lithofacies combination, a clastic (delta-lake) stratigraphic superposition pattern developed in the clastic sequence strata. Influenced by volcanic activities, volcanic-clastic sequences mainly developed in the southwest gentle slope belt of the lower sub-member of the fourth member of the Shahejie Formation in the south of Laizhou Bay. According to the change in the lithofacies combination, the proximal caving-thermal clastic flow stratigraphic superposition pattern mainly developed in the volcanic-clastic sequence. According to the energy change and lithologic characteristics, volcanic activities could be divided into five periods, in which the LST was volcanic phase 1, and the lake TST was the volcanic-intermittent period, with normal clastic sedimentation, and three periods of volcanic activities were in the HST. The saline lake sequence mainly developed in the center of the lake basin in the fourth member of the Shahejie Formation, and it was subdivided into the gypsum saline lake sequence in the lower sub-member of the fourth member of the Shahejie Formation and the carbonate lake sequence in the upper sub-member according to different salinization degrees. The sulfate lake superposition pattern of progradation-accretion saline lake salt rock-saline lake mud mixed-sedimentation and the progradation-retrogression carbonate rock-clastic rock mixed-sedimentation type stratigraphic superposition pattern developed. Based on the study of several types of sequence strata in different blocks, a unified sequence stratigraphic framework was established, and the stratigraphic distribution characteristics were examined under the sequence stratigraphic framework. According to the distribution and evolution of the sequence stratigraphy in the Lainan subdepression, the sequence thickness of the fourth member of the Shahejie Formation in the study area was generally thinner in the southwest, south, and east, and thickest in the middle and northeast. The reflected provenance included three directions: west, south, and east. Based on the analysis of the sequence stratigraphy, the evolution law of sequence filling was discussed and a unique sequence development model in the study area was established. Generally, the strata in the study area presented a pyroclastic rock-evaporite-clastic rock mixed-sedimentation type filling pattern. Moreover, a sequence stratigraphic model for the comparison of steep slope-gentle slope differences was constructed. Based on the analysis of sequence stratigraphic characteristics, the filling evolution law, and the establishment of the sequence development model combined with the characteristics of seismic emission, the high-stand system tract of the fourth member of the Shahejie Formation in the B structural belt is found in the study area. The low system tract of the fourth member of the Shahejie Formation in the D structural belt is found in the study area; the high-stand system tract and the low-stand system tract of the upper fourth member of the Shahejie Formation and the high-stand system tract and the low-stand system tract of the lower fourth member of the Shahejie Formation in the E structural belt have well-developed lithological bodies, which can be used as key potential targets for future oil and gas exploration. Conceptualization, investigation, writing--original draft, and data curation: C.Z.