Downslope transition of turbidity current bedforms linked to minimal slope changes in the northeast South China Sea

Supercritical‐flow bedforms are ubiquitous on Earth and crucial in shaping landscapes. While flume experiments have demonstrated that various types of bedforms may coexist and mutually transition, these phenomena remain poorly documented in stratigraphic records. This study reports novel findings of the downslope transition between four types of supercritical to transitional bedforms within a ~20 000 km 2 Quaternary turbidity current sediment wave field in the transition from continental rise to abyssal plain of the northeastern South China Sea, by integrating high‐resolution seismic data interpretation and numerical simulations. The identified bedforms include cyclic step (CS), upslope‐migrating antidune (UMA), downslope‐migrating antidune (DMA) and upper‐regime plane beds (UPB). Five downslope transition patterns between these bedforms are recognised, which are CS‐to‐UMA and UMA‐to‐UPB transitions at concave‐upward slope breaks, and UMA‐to‐CS, UPB‐to‐CS and UPB‐to‐DMA transitions at convex‐upward slope breaks. These bedform transitions occur alternatively downslope across a fairly gentle (<0.6°) region from the continental rise to the abyssal plain over tens to hundreds of kilometres, exhibiting a complex bedform transition pattern that reflects frequent variations of flow dynamics. Numerical simulations indicate that minimal slope‐break magnitudes of 0.1° to 0.5° can trigger bedform transitions through decelerating flows as the slope angle decreases and accelerating flows as the slope angle increases. These findings highlight the diversity of bedform types and the complexity of their transitions in unconfined deep‐sea settings and underscore the sensitivity of turbidity currents to subtle slope perturbations.