## 5 Conclusions  
The lower submember of Member 2, Dongying Formation (E\({}_{3}\)d\({}_{2}\)\({}^{\mathrm{L}}\)), in the HHK Depression contains a thin-bedded beach-bar system characterized by thin sandbodies (3 to 8 m thickness), limited stratigraphic layers (1-2 layers), and exceptional lateral continuity. The following three sedimentary microfacies are identified within this system: bar-core facies exhibiting \(>\) 8 m single-layer thickness, beach-core facies with 3 to 8 m thick sands, and beach-margin facies comprising \(<\) 3 m accumulations. These microfacies display two distinct vertical stacking patterns, the \"Thin-layer Stable Type\" featuring thick mudstone intervals intercalated with isolated sandstone layers, and the \"Thick-Thin Superposition Type\" characterized by alternating thick and thin sand units. The development of this unique depositional system is governed by synergistic interactions among four fundamental controls. A subtropical paleoclimate regime shifting from dry-hot to warm-humid conditions--marked by secondary fluctuations during the Zone III-V polynofacies transition--established the essential environmental foundation. Concurrently, paleobathymetric analysis confirms prevailing shallow lacustrine conditions (mean Fe/Mn = 89.4), with optimal beach-bar deposition concentrated in the 10-20 m depth range of the central strike-slip and uplift zones. Tectonically, strike-slip extensional stress partitioned sub-units through sustained uplift, generating fault-controlled intra-depressional high that dictated sandbody distribution patterns. Provenance constraints from detrital zircon U-Pb age spectra--displaying diagnostic peaks at 137 Ma, 689 Ma, and 2339 Ma--further validate a dual mixing system where braided river deltas along the southern gentle slope supplied substantial sediments. Key innovations emerge from this integrated analysis, most notably the establishment of a novel sedimentary model for thin beach-bars in strike-slip extensional settings. This framework challenges conventional \"tectonic slope-break control\" paradigms by proposing a \"Strike-slip Partitioning + Paleotopography + Climate Transition Synergy\" coupling mechanism. The model demonstrates that intra-depressional highs (central strike-slip/uplift zones) function as primary depositional loci, while synergistic preservation driven by late E\({}_{3}\)d\({}_{2}\)\({}^{\mathrm{L}}\) lacustrine flooding coinciding with warm-humid climatic transition enables unprecedented large-scale deposition of thin-bedded systems. Collectively, these findings deliver significant multidisciplinary implications. Theoretically, this work provides a genetic paradigm for lacustrine, thin beach-bar formation, advancing sedimentological understanding in strike-slip basins and refining beach-bar classification schemes. For petroleum exploration, it identifies central strike-slip/uplift zones as high-potential targets, strategically shifting exploration paradigms from \"thick-focused\" to \"thin-widespread\" lithologic reservoir plays. Methodologically, the integration of palynological climate proxies, zircon provenance tracing, and quantitative paleogeomorphic restoration establishes a transferable analytical framework applicable to depositional systems in complex tectonic settings globally. Conceptualization, J.W. and Y.H. ; methodology, H.L. and B.F.; software, X.Y., X.H., B.F. and Z.Z. ; validation, H.L., X.Y. and X.H. ; formal analysis, X.Y. and X.H. ; investigation, Y.H., H.L., J.W. and B.F.; resources, Z.Z., B.F., X.Y. and X.H. ; data curation, X.Y.,X.H. and B.F.  
writing--original draft preparation, J.W. ; writing--review and editing, J.W. and Y.H. ; visualization, Y.H., H.L., J.W. and Z.Z. ; supervision, Y.H., H.L. and J.W. ; project administration, H.L. and Y.H. ; funding acquisition, H.L. and Y.H. All authors have read and agreed to the published version of the manuscript. This research was funded in part by a grant from the National Key Technologies R & D Program of China during the 14 th Five-Year Plan Period (KJGG2022-0303, No.