2026/05/05 by Xin Shan, Robert W. Dalrymple, Xuefa Shi +7
Earth and Planetary Sciences · Environmental Science · #Geological formations and processes #Coastal wetland ecosystem dynamics #Hydrology and Sediment Transport Processes
paper · doi:10.1111/sed.70122
ABSTRACT Depositional models for straits have predominantly focused on symmetric systems in both the longitudinal (along‐strait) and transverse (across‐strait) directions. This framework overlooks straits characterised by significant asymmetry, specifically those displaying profound imbalances in both directions regarding topography, hydrodynamics and sediment supply. Bohai Strait, connecting the Bohai and Yellow Seas, serves as an important example to investigate this topic. Transversely, it features a deep, tide‐dominated northern passageway that contains little mobile sediment operating in parallel with a shallow, wind‐driven southern margin receiving the immense fine‐grained load of the Yellow River. Longitudinally, the strait exhibits an asymmetry, characterised by a larger flood‐tidal delta that contrasts with a much smaller ebb‐tidal delta. The asymmetric products of the Bohai Strait result primarily from a three‐stage evolution throughout the late Pleistocene and Holocene. The incipient strait (~11.6 to 10.3 ka cal BP) was characterised by the discharge of the Yellow River into the central Bohai Sea, which deposited the paleo‐Shandong Mud Wedge. A critical reorganisation probably started at ~10.3 ka cal BP, driven by two factors: the widening of the strait and the cutoff of mud supply due to the southward avulsion of the Yellow River. This event triggered a spatial contrast, causing a widespread depositional hiatus in the south while initiating the tide‐dominated channel with its sandy flood‐tidal delta in the north. After ~6.5 ka cal BP, the return of the Yellow River to Bohai Sea amplified this spatial divergence between the deeply scoured northern tide‐dominated system and the shallow southern supply‐dominated system. Overall, the northern half of the Strait experiences net input of locally eroded sand to the Bohai Sea (i.e. it is flood‐tide dominated), whereas the southern half exports mud to the Yellow Sea. The Bohai Strait highlights that longitudinal and transverse asymmetries in sedimentary processes and products require a broader framework beyond the simplified tidal‐strait models.