Sedimentary Environment and Acoustic Characteristic of the Holocene deposits in the southeastern Yellow Sea

High-resolution (Chirp and Sparker system) seismic survey and sediment sampling were conducted to investigate sedimentary environment and acoustic characteristics of the Holocene deposits in the southeastern Yellow Sea. Based on the analysis of the high resolution seismic profiles, the sedimentary sequence was divided into three units bounded by erosional bounding surface: (1) acoustically transparent or indistinctly layers and homogeneous seismic facies (Unit A), (2) parallel reflections and ridge-and-swale topography (Unit B), (3) confused inner reflectors and incision-fills (Unit C). The features of acoustic turbidity related to shallow gas are widely founded in the inner reflections of Unit A and B. On the basis of seafloor morphology, surface bedforms, and subbotom acoustic characters, echo types in the study area were classified; (1) flat seafloor with sharp bottom echoes (transgressive sediment sheets or relict sands), (2) acoustically transparent unit of sheet or distinct reflections (Holocene muds), (3) mounded seafloor (tidal ridges), and (4) various-scale eroded seafloor (channels). Core samples were analyzed for sediment textures, physical properties (porosity, water content, bulk density, grain density and shear strength), acoustic properties (compressional wave speed and attenuation), and electrical resistivity.