Seismic morphology and infilling architecture of incised valleys in the northwest South Yellow Sea since the last glaciation

Based on the interpretation of ∼3000 km of high-resolution seismic profiles, the small local rivers that form the channel network of the northwestern South Yellow Sea are identified for the first time. Incised-valley systems orientated NW–SE and NE–SW were detected outside Dingziwan Bay and Rushan Bay, respectively. Analysis of the sedimentation and fill sequences of these valleys revealed six main types of fill architecture: horizontal or near-horizontal, lateral, undulate-wavy, concave, divergent, and chaotic. Stratigraphic sequence relationships and AMS 14C and OSL dating of two cores (QDZ03 and QDZ01) suggest that these incised valleys were formed during the period from late Marine Isotope Stage 3 (MIS 3) to MIS 1, between 30 and 11 ka BP. The incised-channel fill begins with fluvial sediments and shows a transition to estuarine sediments that are truncated by a transgressive ravinement. There is little evidence of lag deposits at the base of the fill and no evidence of capping by Holocene mud deposits. The incised-valley model presented in this paper differs from current classical sequence stratigraphic models and contributes to our understanding of incised valleys.