Influence of basement high and detachment on the kinematics of a fold-and-thrust belt in the central South Yellow Sea Basin, China: Insights from analog modeling

A fold-and-thrust belt (FTB) characterized by a basement high and detachment layer was developed beneath the South Yellow Sea Basin, an important petroleum exploration target. In the central basin, magnetic anomalies have revealed the basement high developed under the Laoshan Uplift. Seismic reflection together with drilling data have revealed the Lower Silurian Gaojiabian Formation exceeding similar to 500 m acting as a low-cohesion detachment layer. However, the influence of these features on regional structures and the consequent hydrocarbon preservation conditions remains unclear. This study examined the kinematic characteristics and deformation localization associated with the basement high and intermediate detachment, respectively and collectively, using four sandbox models and particle velocity analysis under the FTB framework. Model 1, the reference, used pure quartz sand without either feature. Model 2 examined the role of the intermediate detachment using glass microbeads, finding very limited effect in producing typical thin-skinned FTB. Model 3 considered the basement high, finding that it strongly constrained the deformation regime of the wedge. Model 4 examined both features and suggested combined influence on FTB deformation processes. In Model 2, with the absence of a pre-existing basement high, the intermediate detachment did not play a role in FTB deformation. In Model 3, with the absence of an intermediate detachment, deformation propagated along the surface of the basement high after reaching its edge. In Model 4, shortening propagated upward along the edge of the basement high and then into the intermediate detachment; moreover, comparable structural geometry to the prototype was produced, including both thick- and thin-skinned FTBs in nature. The results indicate that in the central South Yellow Sea Basin, structural layers between the basement high and detachment should similarly experience weak deformation; thus, good hydrocarbon preservation conditions can be expected there. This study is of significant importance to guide future petroleum exploration in the central South Yellow Sea Basin.