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

Based on the interpretation of similar to 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 C-14 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.