## 4 Discussion  
Genetic mechanism analysis indicates a subtropical climate during stable beach-bar deposition in the E3d2L of the HHK Depression, with a climatic shift from dry-hot to warm-humid from E3s2 to E3d2L. Under the persistent extension strike-slip tectonic stress field, increased fault activity rates in the Dongying Formation, sustained intra-depression uplift, gradual water deepening, sufficient local sediment supply from delta fronts, and enhanced wave reworking collectively promoted beach-bar development. The late lacustrine flooding event in E3d2L facilitated beach-bar preservation, forming extensive thin-bedded (<5 m), laterally continuous beach-bar sandbodies within uplifted zones. Paleoenvironmental evolution and secondary fluctuations provided unique depositional conditions. Tectonic controls manifest in the following three key aspects: (1) sandbody distribution constrained by sub-tectonic units; (2) sandbody thickness modulated by differential fault displacement; (3) delta-front sheet sand dimensions dependent on regional provenance supply, while sandbody enrichment is governed by local reworking processes. The coupling of these factors establishes the genetic model for thin stable beach-bar deposits in the HHK Depression. This genetic model exhibits significant differences from conventional lacustrine beach-bar systems, as contrasted below (Table 6). Integrated studies of paleoclimate, paleobathymetry, tectonics, and provenance support a braided-delta beach-bar sedimentary model under strike-slip faulting (Figure 10). This model synthesizes spatial sediment distribution patterns, paleoclimate constraints, and lacustrine paleogeomorphology, objectively delineating controls on beach-bar distribution. Spatiotemporal analysis reveals the following distinct evolutionary phases: During the Shahejie Formation deposition, ample sediment supplies developed fan-delta to braided-delta systems extending southward to the central structural ridge, forming interconnected depositional systems with southern braided deltas [50; 51]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Feature** & **HHK E3d2L Beach-Bar System** & **Conventional Lacustrine Beach-Bar Systems** \\ \hline Climate Context & Dry–hot \(\rightarrow\) Warm–humid transition & Arid-dominated conditions \\ Tectonics & Strike-slip extensional tectonic & Simple fault-slope control \\  & framework & Thick–thin interbedded architecture, \\ Sandbody Distribution & Thin-bedded (3 to 8 m) and laterally &
\begin{tabular}{c} Thick–thin interbedded architecture, \\ relevant vertical stacking, and rapid \\ lateral variation \\ \end{tabular} \\ Provenance & Dual sources with paleotopographic & Single dominant source \\  & coupling & Strike-slip partitioning + & \\ Innovation & Paleotopography + climate transition & Tectonic–sedimentary binary control \\  & synergy & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparative characteristics of beach-bar systems. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Well**} & \multirow{2}{*}{
\begin{tabular}{c} **Sampling** \\ **Depth/m** \\ \end{tabular} } & \multirow{2}{*}{**Zircon Age Range (Ma)**} & \multicolumn{6}{c}{**Geological Age**} \\ \cline{4-9}  & & & **Cenozoic** & **Mesozoic** & **Paleozoic** & **Pt3** & **Pt2/Pt1/Ar2** \\ \hline C3-1-a & 3450 & — & 570–1000 & 1800–3100 & 0 & 0 & 11 & 50 \\  & 3515 & — & 500–1000 & 1800–3100 & 0 & 0 & 5 & 16 & 59 \\  & 2675 & 65–250 & 570–1000 & 1800–3850 & 0 & 0 & 7 & 9 & 54 \\  & 2775 & 135–250 & 570–1000 & 1800–3100 & 0 & 2 & 1 & 9 & 52 \\ B8-2-a & 3165 & 65–250 & 570–1000 & 1800–3100 & 0 & 3 & 5 & 14 & 45 \\ B8-2s-b & 3190 & 65–250 & 500–800 & 1800–3100 & 0 & 11 & 2 & 15 & 73 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Statistical Analysis of Detrital Zircon U-Pb Age Populations Determined by LA-ICP-MS. In the Dongying Formation, weakened northern sediment supply and gentler slopes promoted braided-delta beach-bar systems throughout the depression.